Shaft seal

Abstract

The present invention provides a shaft seal which can reduce the rotation torque and has excellent sealing performance. The shaft seal (1) is an annular shaft seal which is in close contact with the outer peripheral surface of a rotating shaft (6) and seals the sealing fluid; the gap between the rotating shaft (6) and the housing (7) on which the shaft seal (1) is installed is divided into a high-pressure side and a low-pressure side by the shaft seal (1); the shaft seal (1) is an injection molded body which is roughly U-shaped in an axial cross-sectional view, and has a sealing lip (2) extending toward the high-pressure side and sliding with the rotating shaft (6), and an outer lip (3) arranged on the outer diameter side relative to the sealing lip (2); the inclination angle α of the sealing lip (2) relative to the outer peripheral surface of the rotating shaft (6) is 5° to 20°, and in the axial cross-sectional view of the shaft seal (1), the length L2 of the sealing lip is 2.0 mm to 6.5 mm.

Description

Technical Field

[0001] The invention relates to a shaft seal of a rotating shaft, and in particular to a shaft seal of a rotating shaft of a scroll compressor of a vehicle air conditioner. Background Art

[0002] A sealing member is used in a compressor to prevent leakage of refrigerant and refrigeration oil. For example, in a scroll compressor having a compression mechanism composed of a fixed scroll and a movable scroll that performs a gyratory motion relative to the fixed scroll, a shaft seal is installed on a rotating shaft that drives the compression mechanism.

[0003] As shaft seals, lip seals such as those disclosed in Patent Documents 1 and 2 are disclosed. For example, the lip seal of Patent Document 1 is shown in FIG. Figure 6 .like Figure 6 As shown in the lip seal 21, in a cross-sectional view along the axial direction of the drive shaft 22, there are inner peripheral seal portions 25, 26, and 27 that are in contact with the outer peripheral surface of the drive shaft 22. Furthermore, the lip seal 21 has a structure in which the inner peripheral seal portions 25 and 26 include a first seal lip L1 and a second seal lip L2 located on the inner side of the housing 24 in the drive shaft direction relative to the fixing portions 28 and 29 on the side of the shaft hole 23, and the inner peripheral seal portion 27 includes a third seal lip L3 located on the outer side of the housing 24 in the drive shaft direction relative to the fixing portion 30 on the side of the shaft hole 23. Since a space S capable of retaining lubricating oil is formed between the second seal lip L2 and the third seal lip L3, the lubricating oil retained in the space S prevents the wear of the second seal lip L2 and the third seal lip L3, thereby ensuring sealing performance. In Patent Document 1, the inclination angle θ of the second seal lip L2 relative to the outer peripheral surface of the drive shaft 22 is about 30°, but the relationship between θ and the rotational torque is not studied.

[0004] The lip seal of Patent Document 2 is shown in Figure 7 .like Figure 7 As shown in , the lip seal 31 is installed between the housing 32 and the rotating shaft 33, and the sealing lip 35 of the first sealing element 34 and the sealing lip 37 of the second sealing element 36 are used to prevent the fluid (refrigerant and refrigeration oil) in the fluid containing chamber R from leaking to the low-pressure side A. The first sealing element 34 is formed of synthetic rubber, and the second sealing element 36 is formed of a synthetic resin such as tetrafluoroethylene (PTFE) resin. When the rotating shaft is stationary, the sealing lip 35 of the first sealing element 34 elastically contacts the rotating shaft 33 to prevent leakage of the fluid. In addition, the fluid that leaks slightly from the first sealing element 34 during rotation is sealed with the sealing lip 37 of the second sealing element 36. In Patent Document 2, there is no mention of the inclination angle of the first sealing element 35 relative to the outer peripheral surface of the rotating shaft.

[0005] On the other hand, as a shaft seal with a simple structure, a shaft seal with a roughly U-shaped cross-section is known. For example, in Patent Document 3, as a roughly U-shaped shaft seal, a U-shaped (U-shaped) seal including a bottom wall, an inner lip and an outer lip is disclosed, which is installed in a concave groove to be installed, and the inner lip is in sliding contact with the rotating shaft. In this U-shaped seal, the back of the bottom wall is formed as a flat surface that fits closely with the inner end surface of the concave groove, and the outer surface corners of the two end corners of the bottom wall are respectively right angles, and straight lines of a predetermined height from the back side are formed on the inner surface and the outer surface. Furthermore, a gradient portion is formed from the terminal end of each straight line portion, and the inner lip and the outer lip are inclined and protruded in a direction in which the front ends are separated from each other. In the free state of the U-shaped seal, the gradient portion is inclined at a predetermined angle relative to the axis.

[0006] In addition, patent document 4 discloses a sealing ring that can be used for a scroll compressor. As the shape of the sealing ring, a square ring and a U-shaped sealing ring (a ring-shaped sealing member with a roughly U-shaped cross section) can be listed. The sealing ring is a molded body of a resin composition. As a resin composition, a resin composition containing 1 to 7 parts by weight of a powder of a compound having a layered crystal structure and 8 to 27 parts by weight of unmodified polytetrafluoroethylene powder relative to 100 parts by weight of polyethersulfone is proposed. In addition, it is said that an elastomer can be contained in the resin composition, and when the content is less than 7.5% by mass, the bending modulus is reduced within the range of not damaging the mechanical properties represented by wear resistance and elongation at break.

[0007] Patent Document 5 discloses a seal ring composed of a mixture of a soft resin containing at least one of a thermoplastic elastomer and a dynamically crosslinked resin and a hard resin.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2018-17161

[0011] Patent Document 2: Japanese Patent No. 2847277

[0012] Patent Document 3: Japanese Patent Application Publication No. 2003-166649

[0013] Patent Document 4: Japanese Patent No. 5876007

[0014] Patent Document 5: Japanese Patent Application Publication No. 2014-156935 Summary of the invention

[0015] Problems to be solved by the invention

[0016] In the above-mentioned Patent Documents 1 and 2, it has not been studied how the rotation torque and sealing performance will be affected when the inclination angle of the sealing lip relative to the outer peripheral surface of the rotating shaft and the length of the sealing lip in the cross-sectional view are changed. In addition, the lip seals of the above-mentioned Patent Documents 1 and 2 are of a complex shape consisting of an annular metal core material and a plurality of sealing lips formed of resin or rubber, and may be expensive.

[0017] On the other hand, regarding the substantially U-shaped shaft seal, although the above-mentioned Patent Document 3 mentions the inclination angle of the gradient portion, it does not study the inclination angle of the seal lip mounted on the rotating shaft relative to the outer peripheral surface of the rotating shaft. In addition, it has not yet studied how the rotation torque and sealing performance will be when the length of the seal lip in the cross-sectional view is changed. Patent Documents 4 and 5 do not mention the specific cross-sectional shape of the seal lip.

[0018] 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 properties.

[0019] Means for solving problems

[0020] The shaft seal of the present invention is an annular shaft seal that fits tightly against the outer peripheral surface of the rotating shaft and seals the sealing fluid, and is characterized in that the gap between the rotating shaft and the housing on which the shaft seal is installed is divided into a high-pressure side and a low-pressure side by the shaft seal; the shaft seal is an injection molded body that is roughly U-shaped in an axial cross-sectional view, and has a sealing lip that extends toward the high-pressure side and slides with the rotating shaft, and an outer lip that is arranged on the outer diameter side relative to the sealing lip; the inclination angle of the sealing lip relative to the outer peripheral surface of the rotating shaft is 5° to 20°, and in the axial cross-sectional view of the shaft seal, the length of the sealing lip is 2.0 mm to 6.5 mm. The "inclination angle of the sealing lip" in the present invention refers to the angle at which the sealing lip is inclined relative to the outer peripheral surface of the rotating shaft when the shaft seal is installed on the rotating shaft.

[0021] The invention is characterized in that the shaft seal is formed of a resin composition or a thermoplastic elastomer composition.

[0022] The shaft seal is characterized in that the flexural modulus based on ASTM D790 is 200 MPa to 2400 MPa.

[0023] The shaft seal is characterized in that the shaft seal is formed of a resin composition containing an ethylene-tetrafluoroethylene copolymer (ETFE) resin or a tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) resin as a main component.

[0024] The resin composition is characterized in that the resin composition contains 1 to 20 volume % of at least one of carbon fiber, graphite and PTFE resin, relative to 100 volume % of the resin composition.

[0025] The resin composition is characterized in that the carbon fibers have an average fiber length of 20 μm to 200 μm.

[0026] The shaft seal is characterized in that the shaft seal is formed of a thermoplastic elastomer composition, the thermoplastic elastomer composition contains a polyester elastomer as a main component, and the polyester elastomer is a copolymer of a hard segment containing an aromatic polyester unit and a soft segment containing a polyester unit or a polyether unit.

[0027] The present invention is characterized in that the aromatic polyester unit contains a naphthalene ring.

[0028] The thermoplastic elastomer composition is characterized in that the thermoplastic elastomer composition contains 1 volume % to 40 volume % of PTFE resin relative to 100 volume % of the thermoplastic elastomer composition.

[0029] The characteristic lies in that, when the inner diameter dimension of the shaft seal before assembling the rotating shaft is d, the outer diameter dimension of the rotating shaft is D, and the interference between the shaft seal and the rotating shaft is (Dd), the shaft seal satisfies (Dd) / D=0.005-0.06.

[0030] The shaft seal is used in a scroll compressor having a compression mechanism, wherein the compression mechanism is a combination of a fixed scroll and a movable scroll that orbits relative to the fixed scroll, and the rotating shaft is a rotating shaft that drives the compression mechanism.

[0031] The invention is characterized in that the scroll compressor is a scroll compressor of a vehicle air conditioner.

[0032] Characteristically, the sealing fluid contains oil.

[0033] In addition, the shaft seal of the present invention is an annular shaft seal that is in close contact with the outer circumferential surface of the rotating shaft and seals the sealing fluid, and is characterized in that the gap between the rotating shaft and the housing on which the shaft seal is installed is divided into a high-pressure side and a low-pressure side by the shaft seal; the shaft seal is roughly U-shaped in an axial cross-sectional view, and has a sealing lip extending toward the high-pressure side and sliding with the rotating shaft, and an outer lip arranged on the outer diameter side relative to the sealing lip; the shaft seal is a molded body of a resin composition with ETFE resin or PFA resin as the main component; when the inner diameter dimension of the shaft seal before assembling the rotating shaft is set to d, the outer diameter dimension of the rotating shaft is set to D, and the interference between the shaft seal and the rotating shaft is set to (Dd), (Dd) / D=0.005~0.06 is satisfied.

[0034] In addition, the shaft seal of the present invention is an annular shaft seal that is in close contact with the outer peripheral surface of a rotating shaft and seals a sealing fluid containing oil, and is characterized in that the shaft seal is roughly U-shaped in an axial cross-sectional view, and has a sealing lip portion that extends to one side in the axial direction and slides with the rotating shaft, and an outer lip portion that is arranged on the outer diameter side relative to the sealing lip portion; the shaft seal is a molded body of a thermoplastic elastomer composition with a polyester elastomer as a main component, and has a bending elastic modulus based on ASTM D790 of 200MPa to 2400MPa.

[0035] Effects of the Invention

[0036] The shaft seal of the present invention is roughly U-shaped in the axial cross-sectional view, and has a sealing lip extending toward the high-pressure side and sliding with the rotating shaft, and an outer lip provided on the outer diameter side relative to the sealing lip. The sealing lip has an inclination angle of 5° to 20° relative to the outer peripheral surface of the rotating shaft, so that the pressing force on the rotating shaft can be appropriately exerted, the rotational torque can be reduced, and the sealing performance is excellent. Furthermore, in the axial cross-sectional view of the shaft seal, the length of the sealing lip is 2.0 mm to 6.5 mm. The sealing lip has a certain length, so the pressing force of the sealing lip on the rotating shaft becomes smaller, which further contributes to low torque.

[0037] Since the shaft seal is formed of a resin composition or a thermoplastic elastomer composition, a metal core material or the like is not required, and the economic efficiency is also excellent.

[0038] The shaft seal has a flexural modulus of 200 MPa to 2400 MPa according to ASTM D790. Therefore, the flexibility of the shaft seal is improved and the pressing force can be appropriately reduced.

[0039] The shaft seal is formed of a resin composition with ETFE resin or PFA resin as the main component, so it is excellent in flexibility and can be injection molded. In addition, due to its excellent chemical resistance and oil resistance, it is suitable for environments in contact with fluids such as refrigerants and oils.

[0040] The resin composition contains 1% to 20% by volume of at least one of carbon fiber, graphite, and PTFE resin relative to 100% by volume of the resin composition, so that the friction and wear characteristics are excellent. In addition, since the carbon fiber used is a short fiber with an average fiber length of 20 to 200 μm, the increase in melt viscosity can be suppressed compared to the case where long fibers are used, and a shaft seal can be easily obtained by injection molding.

[0041] In the shaft seal, since (Dd) / D obtained by dividing the interference (Dd) by the outer diameter dimension D of the rotating shaft is within the above-mentioned numerical range, the rotation torque can be reduced without impairing the sealing performance.

[0042] The shaft seal is formed of a thermoplastic elastomer composition mainly composed of a polyester elastomer, which is a copolymer of a hard segment containing an aromatic polyester unit and a soft segment containing a polyester unit or a polyether unit, and thus has excellent flexibility and moldability. Furthermore, since the aromatic polyester unit contains a naphthalene ring, it can improve chemical resistance and oil resistance, and is suitable for environments in contact with sealing fluids containing oil.

[0043] The thermoplastic elastomer composition contains 1 to 40 volume % of the PTFE resin relative to 100 volume % of the thermoplastic elastomer composition, and thus the dynamic friction coefficient can be reduced while maintaining the elongation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a diagram showing a state in which an example of a shaft seal according to the present invention is mounted on a rotating shaft.

[0045] Figure 2 yes Figure 1 An enlarged cross-sectional view of the shaft seal before installation.

[0046] Figure 3 This is a diagram showing a state in which another example of the shaft seal of the present invention is attached to a rotating shaft.

[0047] Figure 4 It is a schematic cross-sectional view showing a compression mechanism portion of a scroll compressor.

[0048] Figure 5 This is a schematic diagram of a rotation torque measurement test.

[0049] Figure 6 It is a diagram showing the structure of a conventional shaft seal.

[0050] Figure 7 It is a diagram showing the structure of a conventional shaft seal. DETAILED DESCRIPTION

[0051] based on Figure 1 A compressor to which the shaft seal of the present invention is applied will be described. Figure 1 An axial cross-sectional view showing the state where the shaft seal is installed on the rotating shaft. Figure 1 As shown in , the shaft seal 1 is an annular component that is roughly U-shaped in an axial cross-sectional view, and has a sealing lip 2 on the sealing inner diameter side extending to one side in the axial direction, and an outer lip 3 provided on the sealing outer diameter side relative to the sealing lip 2. The sealing lip 2 and the outer lip 3 extend from the base end 4, respectively. A groove 5 is formed by the sealing lip 2, the outer lip 3 and the base end 4. An insertion hole 7a for inserting the rotating shaft 6 is provided in the housing 7, and an annular groove 8 is provided around the insertion hole 7a. The shaft seal 1 is mounted on the annular groove 8, and the rotating shaft 6 rotates around the axis O, so that the sealing lip 2 slides on the rotating shaft 6.

[0052] exist Figure 1 In the embodiment, the shaft seal 1 is installed in the annular groove 8 in such a manner that the sealing lip 2 and the outer lip 3 extend toward the high pressure side H, respectively. In this case, the groove 5 side corresponds to the high pressure side H, and the back surface 4a side of the base end portion 4 corresponds to the low pressure side L. In the installed state, the vicinity of the front end portion 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 front end portion of the sealing lip 2 contacts the outer peripheral surface of the rotating shaft 6. In addition, 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 3 and the side wall 8a, and between the sealing lip 2 and the rotating shaft 6, respectively.

[0053] As a viewpoint, the inventors have found that the shaft seal 1 having a simple structure and a substantially U-shaped shape can achieve low torque and low leakage by optimizing the inclination angle α of the seal lip 2 relative to the outer peripheral surface of the rotating shaft 6 and the lip length L2 of the seal lip in the cross-sectional view. Specifically, the feature is that Figure 1 For the shaft seal 1, the inclination angle α of the sealing lip 2 is 5° to 20°, and the lip length L2 of the sealing lip 2 is 2.0 mm to 6.5 mm. If the inclination angle α is less than 5°, the sealing lip 2 is parallel to the rotating shaft 6, so fluid leakage may easily occur. On the other hand, if the inclination angle α is greater than 20°, the pressing force of the sealing lip 2 on the rotating shaft 6 increases, so the rotation torque may increase. The inclination angle α is preferably 10° to 20°.

[0054] In addition, if the lip length L2 is shorter than 2.0 mm, the sealing lip 2 is not easily flexed, the pressing force increases, and the rotation torque may increase. On the other hand, if the lip length L2 becomes longer, the space for assembling the shaft seal becomes larger, so the upper limit is set to 8.0 mm, for example. The preferred range of the lip length L2 is 4.2 mm to 6.5 mm.

[0055] Reference Figure 2 The dimensions of the shaft seal 1 are described. Figure 2 The shaft seal is shown in a state (free state) before being installed in the housing. In the shaft seal 1, the sealing lip 2 and the outer lip 3 are formed to be inclined in a direction in which the front end 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. The inner diameter dimension d represents the inner diameter dimension of the shaft seal 1. Figure 2 The distance between the front end portions 2a of the sealing lips 2 facing each other. On the other hand, the maximum inner diameter dimension d of the shaft seal 1 max is the maximum distance between the four opposing base ends. Figure 2 is the distance between the inner edges of the back surface 4a. Figure 2 In the embodiment, the inner peripheral surface of the shaft seal 1 is formed to continuously reduce in diameter from the back surface 4a to the front end portion 2a, and the outer peripheral surface of the shaft seal 1 is formed to continuously expand in diameter from the back surface 4a to the front end portion 3a.

[0056] The sealing lip 2 has a predetermined lip length L2 on its outer peripheral surface. Figure 2 As shown in FIG. 1 , the lip length L2 is the length of a straight line from the corner of the bottom surface 4b of the shaft seal 1 (on the sealing lip 2 side) to the vertex on the outer diameter side of the front end portion 2a of the sealing lip 2. Figure 2 In the embodiment, the back surface 4a and the bottom surface 4b are formed by flat surfaces substantially parallel to the surface orthogonal to the axis of the shaft seal 1. Thus, it is easy to fit closely with the bottom wall 8b of the annular groove 8 (see Figure 1 ). It should be noted that the lip length L2 is Figure 2 The state of freedom and Figure 1 The same length when installed.

[0057] In addition, the outer lip portion 3 has a predetermined lip length L3 on its inner circumference. Figure 2 As shown in FIG. 1 , the lip length L3 is the length of a straight line from the corner of the bottom surface 4b of the shaft seal 1 (on the outer lip 3 side) to the vertex on the inner diameter side of the front end portion 3a of the outer lip 3. It should be noted that the lip length L3 of the outer lip 3 is preferably longer than the lip length L2 of the sealing lip 2.

[0058] The thickness t2 of the sealing lip 2 is preferably 0.3 mm to 1 mm. In addition, when the thickness t2 changes from the base end side to the front end side, it is preferably changed within the range of 0.3 mm to 1 mm. If the thickness t2 is less than 0.3 mm, it is easy to cause short shots during injection molding. In addition, if the thickness t2 exceeds 1 mm, the pressing force of the sealing lip 2 on the rotating shaft increases, and the rotational torque may increase. The thickness t2 is more preferably 0.3 mm to 0.6 mm. In addition, from another point of view, if Figure 2 As shown in , the thickness t2 of the sealing lip 2 is preferably smaller than the thickness t3 of the outer lip 3. If the thickness t2 is larger than the thickness t3, the pressing force of the outer lip 3 on the housing 7 is smaller than the pressing force of the sealing lip 2 on the rotating shaft 6, and there is a possibility that slippage will occur between the outer lip 3 and the side wall 8a of the housing 7.

[0059] Back to Figure 1 The shaft seal 1 is in close contact with the outer peripheral surface of the rotating shaft 6 through the sealing lip 2, thereby preventing the fluid on the high-pressure side H from leaking to the low-pressure side L. Examples of the fluid include refrigerant, oil, and a mixture of refrigerant and oil. In order to ensure the sealing performance of the shaft seal, the inner diameter dimension d of the shaft seal 1 before installation (see Figure 2 ) is smaller than the outer diameter D of the rotating shaft 6. That is, when the shaft seal 1 is assembled to the rotating shaft 6, the shaft seal 1 needs to have an interference.

[0060] The relationship between the inner diameter dimension d of the shaft seal 1 before assembly with the rotating shaft 6, the outer diameter dimension D of the rotating shaft 6, and the interference (Dd) of the rotating shaft 6 is not particularly limited, but preferably satisfies (Dd) / D=0.005 to 0.06, more preferably satisfies (Dd) / D=0.005 to 0.03, and further preferably satisfies (Dd) / D=0.01 to 0.02. By setting the dimensional ratio of the outer diameter dimension D of the rotating shaft 6 and the interference (Dd) of the front end of the seal lip that contacts the rotating shaft 6 to a predetermined range, the rotation torque can be further reduced without impairing the sealing performance.

[0061] In addition, in order to achieve a reduction in rotational torque, such as Figure 1 As shown in , it is preferable to form a space between the seal lip 2 and the rotating shaft 6. In this case, in the mounted state, the base end portion 4 does not contact the rotating shaft 6. In addition, in terms of the dimensional relationship, it is preferable that D<d max (Refer to Figure 2 ).

[0062] The size of the outer diameter D of the rotating shaft 6 is not particularly limited, and is, for example, about 10 mm to 50 mm. The size of the interference (Dd) is not particularly limited, and is, for example, about 0.1 mm to 3 mm.

[0063] It should be noted that the shaft seal of the present invention is not limited to Figure 1 For example, in Figure 1 In the embodiment, the sealing lip 2 is formed into a straight line, or the sealing lip 2 is formed into a straight line. Figure 3 The curved shape is shown in Figure 3 In the case of, the inclination angle α is the angle formed by the tangent line (indicated by a dotted line) of the sealing lip 2 at the tangent point between the sealing lip 2 and the rotating shaft 6 and the outer peripheral surface of the rotating shaft 6. The lip length L2 of the sealing lip 2 is Figure 2 In addition, the shaft seal may be provided with a lip other than the sealing lip and the outer lip (for example, a dust lip that slides with the rotating shaft, etc.).

[0064] exist Figure 1 In the compressor, a compression mechanism is provided on the high pressure side H of the housing 7. The compression mechanism may be any mechanism that compresses the fluid by the rotation of the rotating shaft, and may be a scroll type, a swash plate type, etc. For example, in the case of a scroll type, the compression mechanism is composed of a fixed scroll and a movable scroll that orbits relative to the fixed scroll.

[0065] exist Figure 4 A partial cross-sectional view of the scroll type compression mechanism is shown in FIG. Figure 4As shown in , the compression mechanism 9 comprises: a fixed rotor 11 having a substrate 11a and a fixed-side vortex blade 11b standing upright on its surface; and a movable rotor 12 having a substrate 12a and a movable-side vortex blade 12b standing upright on its surface. The fixed rotor 11 and the movable rotor 12 are meshed with each other in an eccentric state, 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 the movable rotor 12 revolves around the axis of the fixed rotor 11, thereby the compression chamber 10 moves toward the center side of the scroll shape to compress the fluid. The compressed compressed fluid is discharged from the discharge pipe through the discharge port 13 in the center of the movable rotor 12 and flows out to the refrigeration cycle. In addition, the fluid (refrigerant gas, etc.) of the refrigeration cycle is introduced into the compression chamber 10 via the suction port (omitted from the figure).

[0066] The shaft seal of the present invention is an injection molded body formed of a resin composition or a thermoplastic elastomer composition. For the injection molded body, the bending modulus measured according to ASTM D790 is preferably 200MPa to 2400MPa. If the bending modulus is less than 200MPa, it may be easily worn and the sealing performance may be reduced. In addition, if the bending modulus exceeds 2400MPa, the pressing force of the shaft seal on the rotating shaft increases and may become a high torque. The bending modulus of the resin composition forming the shaft seal of the present invention measured according to ASTM D790 is preferably 200MPa to 1800MPa, more preferably 400MPa to 1800MPa.

[0067] Hereinafter, first, a case where the shaft seal is a molded product of a resin composition will be described.

[0068] In the resin composition, there is no limitation on the resin (matrix resin) that serves as the main component, and polyamide (PA) resin, polyphenylene sulfide (PPS) resin, polyetheretherketone (PEEK) resin, polyamideimide (PAI) resin, polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, ethylene-tetrafluoroethylene copolymer (ETFE) resin, polyvinylidene fluoride resin, liquid crystal polymer, polyethersulfone resin, polysulfone resin, polyphenylsulfone resin, polyarylate resin, polyetherimide resin, polyimide resin, polyester resin, etc. can be used.

[0069] In the above-mentioned resin, preferably use the resin that is excellent in heat resistance, chemical resistance, flexibility and can be injection molded, i.e. PA resin, PFA resin, FEP resin, ETFE resin, polyvinylidene fluoride resin. These resins are excellent in chemical resistance and oil resistance, and are therefore suitable for the shaft seal of the rotating shaft of the compressor used in the presence of the fluid mixed with refrigerant and refrigerator oil. In particular, more preferably use ETFE resin or PFA resin. By making the resin combination with ETFE resin or PFA resin excellent in flexibility as the main component, even if the interference is ensured to a certain extent, it is also easy to prevent damage during installation. In addition, by ensuring the interference to a certain extent, even if the sealing lip is worn due to the use of the shaft seal 1, it is also possible to maintain sealing.

[0070] In the shaft seal, when ETFE resin is used as the matrix resin, the melt flow rate (MFR) of the resin composition based on ASTM D3159 is preferably 10 to 50 g / 10 minutes, and more preferably 30 to 50 g / 10 minutes. In addition, when PFA resin is used as the matrix resin, the MFR of the resin composition based on ASTM D3307 is preferably 10 to 80 g / 10 minutes, and more preferably 30 to 50 g / 10 minutes. The higher the MFR, the lower the melt viscosity of the resin composition, and the easier it is to form the sealing lip by injection molding.

[0071] The ETFE resin has a chemical structure represented by the following formula (1), and the copolymerization ratio is not particularly limited. Commercially available products of the ETFE resin that can be used in the present invention include Fluon C-88AP and C-88AXMP manufactured by AGC Corporation.

[0072] [Chemistry 1]

[0073]

[0074] When ETFE resin is used as the matrix resin, the ETFE resin is preferably contained in an amount of 70% by volume or more, more preferably 80% by volume or more, and particularly preferably 90% by volume or more, based on 100% by volume of the resin composition.

[0075] The PFA resin has a chemical structure represented by the following formula (2), and the copolymerization ratio is not particularly limited. fCommercially available products of PFA resins that can be used in the present invention include Fluon P-62XP manufactured by AGC Corporation, Neoflon AP-210 and AP-202 manufactured by Daikin Industries, Ltd., Teflon (registered trademark) 440HP-J, 420HP-J and 411HP-J manufactured by Mitsui Chemicals & Fluoropolymers, Inc., and Dyneon PFA6515 TZ and PFA6525 TZ manufactured by 3M Japan Co., Ltd.

[0076] [Chemistry 2]

[0077]

[0078] When PFA resin is used as the matrix resin, the PFA resin is preferably contained in an amount of 70% by volume or more, more preferably 80% by volume or more, and particularly preferably 90% by volume or more, based on 100% by volume of the resin composition.

[0079] In the resin composition used in the present invention, relative to 100 volume % of the resin composition, preferably at least one of 1 volume % to 20 volume % of carbon fiber, graphite, and PTFE resin, more preferably 1 volume % to 10 volume %. For example, by coordinating more than 1 volume % of the carbon fiber, it is easy to reduce the amount of wear and the deformation caused by pressure. In addition, graphite and PTFE resin are solid lubricants, and by coordinating more than 1 volume % of them, it is easy to reduce the dynamic friction coefficient of the molded body of the resin composition. Carbon fiber, graphite, and PTFE resin can be used alone, or more than 2 kinds can be used in combination. As a further preferred mode of the resin composition, relative to 100 volume % of the resin composition, it is included that the carbon fiber, graphite, and PTFE resin that add up to 1 volume % to 20 volume % (more preferably 1 volume % to 10 volume %).

[0080] When carbon fibers are added, they may be any of asphalt-based or PAN-based fibers classified by raw materials. There is no limitation on the firing temperature, and it may be any of graphitized products fired at a high temperature of 2000°C or higher, and carbonized products fired at about 1000-1500°C. There is no limitation on the fiber diameter, and carbon fibers with an average fiber diameter of about 5-20 μm may be used. In addition, it may be any of milled fibers or chopped fibers, but milled fibers are more preferred because they are short fibers and thus it is difficult to increase the MFR of the resin composition. The average fiber length of the milled fibers is particularly preferably 20-200 μm. As a method for measuring the average fiber length, there can be cited a method of measuring using an SEM image obtained by a scanning electron microscope (SEM), and the like.

[0081] As commercially available milled fibers that can be used in the present invention, pitch-based carbon fibers include KRECA M-101S, M-101F, and M-201S manufactured by Kureha Co., Ltd. In addition, PAN-based carbon fibers include HT M800 160MU and HT M100 40MU manufactured by Teijin Limited and TORAYCA MLD-30 and MLD-300 manufactured by Toray Industries, Ltd.

[0082] As graphite, any of natural graphite and artificial graphite can be used. As natural graphite, ACP manufactured by Nippon Graphite Industries, Ltd. can be listed, as artificial graphite, CGB-10, CGB-20, CGB-50 manufactured by Nippon Graphite Industries, Ltd., KS-6, KS-25, KS-44 manufactured by Imelis Japan Co., Ltd. can be listed.

[0083] As PTFE resin, any one of plastic powder produced by suspension polymerization, fine powder produced by emulsion polymerization, and regenerated PTFE can be used. In order to stabilize the fluidity of the resin composition, it is preferred to use regenerated PTFE that is difficult to be fibrotic by shearing during injection molding and difficult to reduce MFR. Regenerated PTFE refers to heat-treated (heat-treated) powders, powders irradiated with gamma rays or electron beams, etc. For example, there are powders that have been heat-treated with plastic powder or fine powder, powders that have been further irradiated with gamma rays or electron beams, powders that have been pulverized with molded bodies of plastic powder or fine powder, powders that have been irradiated with gamma rays or electron beams, and powders that have been irradiated with gamma rays or electron beams, and powders that have been irradiated with gamma rays or electron beams, etc.

[0084] Commercially available PTFE resins that can be used in the present invention include KTL-610, KTL-450, KTL-350, KTL-8N, and KT-400H manufactured by Kitamura Co., Ltd., Telfon (registered trademark) 7-J and TLP-10 manufactured by Mitsui Kemaz Fluoroproduce Co., Ltd., Fluon G163, L150J, L169J, L170J, L172J, and L173J manufactured by AGC Corporation, Polyflon M-15 and Lubron L-5 manufactured by Daikin Industries, Ltd., and Dyneon TF9205 and TF9207 manufactured by 3M Japan Co., Ltd. In addition, PTFE resins modified with a perfluoroalkyl ether group, a fluoroalkyl group, or other side chain groups having a fluoroalkyl group may also be used. Examples of the PTFE resin irradiated with gamma rays, electron beams, or the like include KTL-610, KTL-450, KTL-350, and KTL-8N manufactured by Kitamura Co., Ltd. and Fluon L169J, L170J, L172J, and L173J manufactured by AGC Corporation.

[0085] It should be noted that in the above resin composition, fibrous reinforcing materials such as aromatic polyamide fibers, spherical fillers such as spherical silica, flaky reinforcing materials such as mica, sliding reinforcing materials such as calcium phosphate and calcium sulfate, and micro-fiber reinforcing materials such as potassium titanate whiskers can be used to the extent that the effect of the present invention is not hindered. Colorants such as carbon black and iron oxide can also be added. These can be added alone or in combination.

[0086] In addition, for the purpose of reducing the elastic modulus of the resin composition, an elastomer can be used. As an elastomer, a fluororubber is preferred. There is no limitation on the type of fluororubber, and vinylidene fluoride system (FKM), tetrafluoroethylene-propylene system (FEPM), tetrafluoroethylene-perfluorovinyl ether system (FFKM) can be used. FKM can be any of a binary system and a ternary system.

[0087] In view of the above circumstances, a particularly preferred embodiment of a shaft seal formed from a resin composition is as follows: relative to 100 volume % of the resin composition, it contains 90 volume % or more of ETFE resin or PFA resin, and contains a total of 1 volume % to 10 volume % of at least one of carbon fiber, graphite and PTFE resin, and the flexural modulus of the shaft seal based on ASTM D790 is 200 MPa to 1800 MPa.

[0088] Next, a case where the shaft seal is a molded product of a thermoplastic elastomer composition will be described.

[0089] In the thermoplastic elastomer composition, there is no limitation on the elastomer that is the main component, and polyolefin elastomers, polyester elastomers, polyamide elastomers, etc. can be used. From the aspects of heat resistance and chemical resistance, polyester elastomers are particularly preferred. Polyester elastomers include hard segments and soft segments, and the hard segments use polyester units, and the soft segments use polyether units or polyester units. Polyester elastomers are multi-block copolymers of polyester-polyether type or polyester-polyester type.

[0090] The polyester unit of the hard segment is preferably mainly composed of an aromatic polyester unit. The aromatic polyester unit is generally a polyester unit containing an aromatic dicarboxylic acid component and a diol component as polymerization components.

[0091] As the aromatic dicarboxylic acid component, for example, an aromatic dicarboxylic acid or its ester derivative can be used. As the aromatic dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid (for example, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid), 4,4'-biphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, etc. can be listed. As the ester derivative of the aromatic dicarboxylic acid, for example, alkyl esters (methyl ester, ethyl ester, etc.), aryl esters, carbonates, etc. of the above-mentioned aromatic dicarboxylic acids can be listed. The aromatic dicarboxylic acid component can be used alone or in combination of two or more.

[0092] In addition to the above-mentioned aromatic dicarboxylic acid components, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid and azelaic acid, and ester derivatives thereof may be used as other copolymerization components.

[0093] The total amount of the aromatic dicarboxylic acid component is preferably 80 mol% or more, more preferably 90 mol% or more, relative to the total molar number of all acid components (100 mol%). In addition, it is particularly preferred that the copolymer is substantially composed of the aromatic dicarboxylic acid component and substantially does not contain other copolymer components (acid components other than the aromatic dicarboxylic acid component).

[0094] As the diol component, for example, diol or its ester derivative can be used. As the diol, for example, aliphatic diols such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol, etc. can be listed. As the ester derivative of the diol, for example, acetyl bodies of the above diols can be listed. The diol component can be used alone or in combination of two or more.

[0095] In the hard segment, it is preferred that a naphthalene ring is included in the aromatic polyester unit. As a structural unit containing a naphthalene ring, a polybutylene naphthalate unit is particularly preferred. The polybutylene naphthalate unit can be obtained, for example, by using naphthalene-2,6-dicarboxylic acid as an aromatic dicarboxylic acid component and 1,4-butanediol as a diol component. The aromatic polyester unit having the polybutylene naphthalate unit can be formed only by the polybutylene naphthalate unit, and can also be formed by including other structural units (for example, polybutylene isophthalate units).

[0096] The polyether unit of the soft segment includes, for example, an aliphatic polyether unit. Examples of the aliphatic polyether unit include poly(ethylene oxide) glycol units, poly(propylene oxide) glycol units, poly(butylene oxide) glycol units, poly(hexylene oxide) glycol units, copolymers of ethylene oxide and propylene oxide, and the like. These structural units may contain one type alone or two or more types.

[0097] The polyester unit of the soft segment includes, for example, an aliphatic polyester unit. Examples of the aliphatic polyester unit include poly(ε-caprolactone) units, polyenantholactone units, polycapryllactone units, polybutylene adipate units, and polyethylene adipate units. These structural units may contain one type alone or two or more types.

[0098] Suitable commercial products of polyester elastomers include, for example, PELPRENE EN type (manufactured by Toyobo Co., Ltd.). PELPRENE EN type has a chemical structure represented by the following formula (3), wherein the hard segment is shown in the following formula (4), and the soft segment is shown in the following formula (5). As shown in the following formula (3), the structural unit of the hard segment and the structural unit of the soft segment are bonded with an ester bond or a carbonate bond. In PELPRENE EN type, the hard segment is composed only of aromatic polyester units, more specifically, only of polybutylene naphthalate units. Specific grades of PELPRENE EN type include EN-1000, EN-2000, EN-3000, EN-5000, EN-16000, etc. The ratio of the hard segment to the soft segment of each grade is different, and as shown in the examples described later, the physical properties (flexural modulus, etc.) are different.

[0099] [Chemistry 3]

[0100]

[0101] When a hard segment composed of an aromatic polyester containing a naphthalene ring in the molecule such as PELPRENE EN is used, the chemical resistance and oil resistance of the polyester elastomer can be improved compared to the case where no naphthalene ring is contained. Therefore, it is suitable for the shaft seal of the rotating shaft of the compressor used in the presence of a mixed fluid of a refrigerant or refrigeration oil.

[0102] In polyester elastomers, the ratio of hard segments to soft segments in copolymerization is not particularly limited, but as the ratio of the hard segments increases, the elastic modulus increases, so it is preferably adjusted so that the bending modulus of the thermoplastic resin elastomer composition is in the range of 200 MPa to 2400 MPa. In addition, since it is easy to make the bending modulus of the molded product in the desired range, it is preferred to use an elastomer having a bending modulus (ASTM D790) of 150 MPa to 1700 MPa for the polyester elastomer.

[0103] The elastomer (for example, polyester elastomer) as the main component is preferably contained in an amount of 60% by volume or more, more preferably 80% by volume or more, and even more preferably 90% by volume or more, based on 100% by volume of the thermoplastic elastomer composition.

[0104] In the thermoplastic elastomer composition used in the present invention, for the purpose of improving friction and wear characteristics, it is preferred to mix solid lubricants such as PTFE resin, graphite, and molybdenum disulfide. Specifically, relative to 100 volume % of the thermoplastic elastomer composition, it is preferred to contain 1 volume % to 40 volume % of solid lubricants. By mixing more than 1 volume % of solid lubricants, the dynamic friction coefficient of the molded body of the thermoplastic elastomer composition can be reduced. On the other hand, if the content of the solid lubricant exceeds 40 volume %, the elongation characteristics of the thermoplastic elastomer composition are reduced, and cracks may be generated when the shaft seal is assembled on the rotating shaft. As for the solid lubricant, relative to 100 volume % of the thermoplastic elastomer composition, it is more preferred to contain 1 volume % to 20 volume %, and it is further preferred to contain 1 volume % to 10 volume %. In addition, as a solid lubricant, PTFE resin is preferably used. It should be noted that the PTFE resin and graphite can use the substances described in the above-mentioned resin composition.

[0105] In addition, to the extent that the effects of the present invention are not impaired, fibrous reinforcing materials such as carbon fiber, glass fiber, and aromatic polyamide fiber, spherical fillers such as spherical silica, flaky reinforcing materials such as mica, sliding reinforcing materials such as calcium phosphate and calcium sulfate, and micro-fiber reinforcing materials such as potassium titanate whiskers may be used in the thermoplastic elastomer composition. Colorants such as carbon black and iron oxide may also be added. These may be added alone or in combination.

[0106] When carbon fibers are added, the content is preferably 5 to 20 volume % relative to 100 volume % of the thermoplastic elastomer composition. As the carbon fibers, those described above for the resin composition can be used.

[0107] In view of the above, a particularly preferred embodiment of a shaft seal formed from a thermoplastic elastomer composition is as follows: it is a molded product of the thermoplastic elastomer composition in which a PTFE resin is blended into a polyester elastomer, the polyester elastomer being a copolymer of a hard segment comprising a polybutylene naphthalate unit and a soft segment comprising an aliphatic polyether unit, the PTFE resin is contained in an amount of 1% to 10% by volume relative to 100% by volume of the thermoplastic elastomer composition, and the shaft seal has a flexural modulus of 200 MPa to 1800 MPa based on ASTM D790.

[0108] The shaft seal of the present invention can be used in a scroll compressor of a vehicle air conditioner. The scroll compressor can be either a belt drive using engine power or a motor drive not using engine power. In addition, the shaft seal of the present invention can be used in more than just compressors.

[0109] The shaft seal of the present invention is formed by injection molding using an injection molding machine for a general thermoplastic resin. After the various materials constituting the above-mentioned resin composition or the above-mentioned thermoplastic elastomer composition are mixed as needed using a Henschel mixer, a ball mill, a ribbon mixer, etc., melt-kneading is performed using a melt extruder such as a twin-screw compounding extruder to obtain pellets for molding. It should be noted that the input of the filler material can also be side-fed when melt-kneading is performed using a twin-screw extruder, etc. The shaft seal is molded by injection molding using the pellets for molding. It should be noted that when a PFA resin is used in the matrix resin of the resin composition, it is preferred to use an injection molding machine or a twin-screw compounding extruder with corrosion resistance specifications.

[0110] The shaft seal of the present invention is not limited to the above Figure 1 to Figure 3 In the above Figure 1 to Figure 3 In the shaft seals 1 and 1', the inclination angle α of the sealing lip 2 is 5° to 20°, and the lip length L2 of the sealing lip 2 is 2.0 mm to 6.5 mm (referred to as method A). When the shaft seal is the following method B or method C, the numerical ranges of the inclination angle α and the lip length L2 may not be met.

[0111] The shaft seal of method B is an annular shaft seal that fits tightly against the outer peripheral surface of the rotating shaft and seals the sealing fluid, and is characterized in that the gap between the rotating shaft and the housing on which the shaft seal is installed is divided into a high-pressure side and a low-pressure side by the shaft seal; the shaft seal is roughly U-shaped in an axial cross-sectional view, and has a sealing lip extending toward the high-pressure side and sliding with the rotating shaft, and an outer lip arranged on the outer diameter side relative to the sealing lip; the shaft seal is a molded body of a resin composition with ETFE resin or PFA resin as the main component; when the inner diameter dimension of the shaft seal before assembling the rotating shaft is set to d, the outer diameter dimension of the rotating shaft is set to D, and the interference between the shaft seal and the rotating shaft is set to (Dd), (Dd) / D=0.005~0.06 is satisfied.

[0112] The shaft seal of method B is a molded body of a resin composition with ETFE resin or PFA resin as the main component. (Dd) / D obtained by dividing the interference (Dd) by the outer diameter D of the rotating shaft is within the above range, and the rotation torque can be reduced without damaging the sealing performance. In addition, the shaft seal is formed by a resin composition with molten fluororesin of ETFE resin or PFA resin as the main component, so it has excellent flexibility and can be injection molded. In addition, due to its excellent chemical resistance and oil resistance, it is suitable for environments in contact with fluids such as refrigerants and oils.

[0113] The shaft seal of method C is an annular shaft seal that is in close contact with the outer peripheral surface of the rotating shaft and seals the sealing fluid containing oil, and is characterized in that the shaft seal is roughly U-shaped in an axial cross-sectional view, and has a sealing lip portion that extends to one side in the axial direction and slides with the rotating shaft, and an outer lip portion that is arranged on the outer diameter side relative to the sealing lip portion; the shaft seal is a molded body of a thermoplastic elastomer composition with a polyester elastomer as a main component, and has a bending elastic modulus based on ASTM D790 of 200MPa to 2400MPa.

[0114] The shaft seal of method C is roughly U-shaped in an axial cross-sectional view, and includes a sealing lip portion extending to one side in the axial direction and sliding with the rotating shaft, and an outer lip portion provided on the outer diameter side relative to the sealing lip portion. It is a molded body of a thermoplastic elastomer composition with a polyester elastomer as a main component, and has a bending modulus of elasticity based on ASTM D790 of 200 MPa to 2400 MPa, so that a shaft seal that can reduce the rotational torque and has excellent sealing performance is obtained.

[0115] Example

[0116] <Test Example A>

[0117] Test Examples A1 to A11

[0118] A resin composition containing 20% ​​by volume of a solid lubricant PTFE resin (50% particle size: 20 μm) and the remainder being a polyamide 66 resin (viscosity number: 150 ml / g) was prepared using a twin-screw compounding extruder and pelletized. It should be noted that the viscosity number was measured using sulfuric acid solution in accordance with ISO 307. A shaft seal was obtained by injection molding using the obtained pellets. The shaft seal is Figure 1 11 types of shaft seals (inner diameter d 19.88 mm) with different inclination angles α and lip lengths L2 of the sealing lip were prepared in the shapes shown in Table 1. The flexural modulus of the resin composition forming these shaft seals measured in accordance with ASTM D790 was 2200 MPa.

[0119] (A-1) Rotational torque test

[0120] use Figure 5 The rotation torque tester shown in the figure was used to perform the rotation torque test under the following conditions to measure the rotation torque and oil leakage. The outer diameter D of the rotating shaft was 20 mm, the interference (Dd) between the shaft seal and the rotating shaft was 0.12 mm in diameter, and (Dd) / D=0.006.

[0121] <Test conditions>

[0122] Rotating axis: Material S45C

[0123] Speed: 7500min-1

[0124] Oil pressure: 0.3MPa

[0125] Oil temperature: 40℃

[0126] Refrigeration oil: polyalkylene glycol oil

[0127] Test time: 60 minutes

[0128] like Figure 5 As shown in , the housing of the test machine 14 is constructed by assembling an outer housing 17 and an inner housing 18. In the mating surfaces of these housings, an O-ring 19 is arranged in the outer peripheral groove of the inner housing 18 to prevent the refrigeration oil from leaking from the mating surface. The shaft seal 15 is in close contact with the rotating shaft 16 and is in sliding contact with the outer peripheral surface of the rotating shaft 16 through the rotation of the rotating shaft 16. The refrigeration oil is pressurized and supplied to the space inside the housing. Figure 5 As shown in the figure, the refrigeration oil flows in from the inlet passage 17b and flows out from the outlet passage 17c through the space inside the housing. The oil leakage amount is based on the amount of refrigeration oil leaking from between the rotating shaft 16 and the insertion hole 17a, and represents the average value of 50 to 60 minutes after the start of the test. In addition, the rotation torque represents the average value of 50 to 60 minutes after the start of the test. The results are shown in Table 1.

[0129] [Table 1]

[0130] Test Example A1 Test Example A2 Test Example A3 Test Example A4 Test Example A5 Test Example A6 Test Example A7 Tilt angle α,° 20 20 20 20 20 5 10 <![CDATA[Lip length L2, mm]]> 2.2 3.5 4.2 5.2 6.5 3.5 5.2 Rotational torque, N·m 0.11 0.11 0.1 0.09 0.07 0.09 0.08 Oil leakage, ml / min ≤1 ≤1 ≤1 ≤1 ≤1 ≤1 ≤1

[0131] ※(Dd) / D=0.006 for test examples A1 to A7

[0132] Test Example A8 Test Example A9 Test Example A10 Test Example A11 Tilt angle α,° 20 30 3 45 <![CDATA[Lip length L2, mm]]> 1.2 3.5 3.5 3.5 Rotational torque, N·m 0.16 0.15 0.09 0.17 Oil leakage, ml / min ≤1 ≤1 10 ≤1

[0133] ※(Dd) / D=0.006 for test examples A8~A11

[0134] As shown in Table 1, when comparing the results of the inclination angle α = 20°, when the lip length L2 = 2.2 mm to 6.5 mm (Test Examples A1 to A5), the rotational torque is a low torque of 0.07 to 0.11 N·m, while when the lip length L2 = 1.2 mm (Test Example A8), the rotational torque is 0.16 N·m, which is a relatively high torque. In the study of the inclination angle α, when α = 3° (Test Example A10), a significant increase in the amount of oil leakage was observed. In addition, when α = 30° and 45° (Test Examples A9 and A11), the rotational torque was 0.15 N·m and 0.17 N·m, and an increase in the rotational torque was observed as the inclination angle α increased. On the other hand, when α = 5° and 10° (Test Examples A6 to A7), low torque and low leakage were shown.

[0135] <Test Example B>

[0136] Next, the composition of the resin composition was changed to evaluate the rotation torque and the sealing property.

[0137] Test Examples B1 to B7

[0138] The raw materials of the resin composition used in each test example are collectively shown below.

[0139] (1) ETFE resin

[0140] AGC Co., Ltd.: Fluon C-88AXMP

[0141] (2) PFA resin

[0142] Daikin Industrial Co., Ltd.: Neoflon AP202

[0143] (3) Polyphenylene sulfide (PPS) resin

[0144] DIC Co., Ltd.: FZ-2100

[0145] (4) Carbon fiber (average fiber length: 150 μm)

[0146] (5) Graphite (50% particle size: 20 μm)

[0147] (6) PTFE resin (50% particle size: 20 μm)

[0148] Using the raw materials (1) to (6), the resin compositions shown in Test Examples B1 to B7 in Table 2 were prepared using a twin-screw kneading extruder and pelletized. The obtained pellets were injection molded to obtain Figure 1 The cross-sectional shape of the shaft seal and the molded body for the bending test are shown in FIG.

[0149] (B-1) Bending test

[0150] A bending test was carried out in accordance with ASTM D790 to measure the bending modulus.

[0151] (B-2) Rotational torque test

[0152] use Figure 5 The rotary torque tester shown in the figure was used to perform the rotary torque test under the above test conditions to measure the rotary torque and oil leakage. The dimensions of the rotary shaft and the shaft seal of the rotary torque tester were set to the outer diameter dimension D of the rotary shaft = 20.5 mm, the inner diameter dimension d of the shaft seal = 20 mm, the interference (Dd) = 0.5 mm, and (Dd) / D = 0.024. In addition, the inclination angle α = 5° and the lip length L2 = 3.5 mm.

[0153] [Table 2]

[0154]

[0155] 1) ASTM D790

[0156] ※(Dd) / D=0.024 for test examples B1 to B7

[0157] ※Test examples B1 to B7 have an inclination angle α = 5° and a lip length L2 = 3.5 mm

[0158] As shown in Table 2, the bending modulus of the shaft seals of Test Examples B1 to B6 is in the range of 200 MPa to 2400 MPa, indicating low torque and low oil leakage. On the other hand, the bending modulus of the shaft seal of Test Example B7 is relatively high (3330 MPa), and the rotational torque is 0.20 N·m, indicating relatively high torque. According to the results of Table 2, a rough correlation is observed between the magnitude of the bending modulus and the magnitude of the rotational torque.

[0159] Test Examples B8 to B11

[0160] A shaft seal formed of the same resin composition as in Test Example B2 (ETFE resin: 94 volume %, carbon fiber: 3 volume %, PTFE resin: 3 volume %) was used to evaluate the rotational torque and sealing performance using four interference settings. It should be noted that the test conditions for the rotational torque test were the same as those described above.

[0161] [Table 3]

[0162] Example B8 Example B9 Example B10 Example B11 The outer diameter of the rotating shaft D, mm 20 20 20 20 Inner diameter of shaft seal d, mm 19.9 19 19.98 18.6 Interference (Dd), mm 0.1 1 0.02 1.4 (Dd) / D 0.005 0.05 0.001 0.07 Rotational torque, N·m 0.07 0.14 0.05 0.26 Oil leakage, ml / min ≤1 ≤1 51 ≤1

[0163] ※Test examples B8 to B11 have an inclination angle α of 5° and a lip length L2 of 3.5 mm

[0164] As shown in Table 3, in the study of the dimension ratio (Dd) / D, when (Dd) / D becomes smaller, the oil leakage increases (Test Example B10), and when (Dd) / D becomes larger, an increase in torque is observed (Test Example B11). According to Table 3, when (Dd) / D=0.05 to 0.005, low torque and low leakage are shown (Test Examples B8 and B9).

[0165] <Test Example C>

[0166] Next, the rotation torque and sealing properties of the injection-molded article of the thermoplastic elastomer composition were evaluated as a shaft seal.

[0167] Test Examples C1 to C8

[0168] The raw materials of the thermoplastic elastomer composition used in each test example are shown below. TPE-1 to TPE-4 all have the chemical structure represented by the above formula (3).

[0169] (1) Polyester elastomer [TPE-1]

[0170] Toyobo Co., Ltd.: EN-1000 (flexural modulus 120 MPa)

[0171] (2) Polyester elastomer [TPE-2]

[0172] Toyobo Co., Ltd.: EN-3000 (flexural modulus 270 MPa)

[0173] (3) Polyester elastomer [TPE-3]

[0174] Toyobo Co., Ltd.: EN-5000 (flexural modulus 480 MPa)

[0175] (4) Polyester elastomer [TPE-4]

[0176] Toyobo Co., Ltd.: EN-16000 (flexural modulus 1630 MPa)

[0177] (5) PTFE resin (50% particle size: 20 μm)

[0178] (6) Carbon fiber

[0179] Kureha Corporation: M-107T (fiber diameter 18 μm, average fiber length 0.4 mm)

[0180] Thermoplastic elastomer compositions shown in Test Examples C1 to C8 in Table 4 were prepared using raw materials (1) to (6) using a twin-screw kneading extruder and pelletized. The obtained pellets were injection molded to obtain Figure 1 The cross-sectional shape of the shaft seal and the molded body for the bending test are shown in FIG.

[0181] (C-1) Bending test

[0182] A bending test was carried out in accordance with ASTM D790 to measure the bending modulus.

[0183] (C-2) Rotational torque test

[0184] use Figure 5 The rotation torque tester shown in the figure is used to perform the rotation torque test under the above test conditions to measure the rotation torque and oil leakage. The dimensions of the rotating shaft and the shaft seal of the rotation torque tester are set to the outer diameter of the shaft seal = 40 mm, the inner diameter of the shaft seal d = 20 mm, and the interference (Dd) = 0.3 mm.

[0185] [Table 4]

[0186]

[0187] 1) ASTM D790

[0188] 2) The test was not carried out because the shaft seal was damaged when assembled to the rotating shaft.

[0189] As shown in Table 4, for the shaft seals of Test Examples C1 to C5, the bending modulus is in the range of 200 MPa to 2400 MPa, showing low torque and low oil leakage. For the shaft seal of Test Example C6, the bending modulus is relatively low (bending modulus 111 MPa), and the oil leakage is 10 ml / min, which is a worse result than that of Test Examples C1 to C5. For the shaft seal of Test Example C7, the proportion of PTFE resin is as high as 45% by volume, the elongation at break is small, and damage occurred during assembly to the rotating shaft. For the shaft seal of Test Example C8, the bending modulus is relatively high (bending modulus 3937 MPa), and the rotational torque is 0.19 N·m, showing a relatively high torque.

[0190] As described above, in the present invention, as one mode, by optimizing the inclination angle and lip length of the seal lip relative to the outer peripheral surface of the rotating shaft, low torque and low leakage are achieved. In addition, as another mode, by optimizing the composition and interference setting of the resin composition, low torque and low leakage are achieved. Furthermore, as another mode, by optimizing the composition and bending modulus of the thermoplastic elastomer composition, low torque and low leakage are achieved. By appropriately combining the above-mentioned modes with appropriate structures, further low torque and low leakage can be achieved.

[0191] Industrial Applicability

[0192] The shaft seal of the present invention can reduce the rotation torque and has excellent sealing performance, so it can be widely used as a shaft seal that seals the sealing fluid while sliding in contact with the outer peripheral surface of the rotating shaft. It is particularly suitable for the shaft seal of the rotating shaft that rotates the compression mechanism of the scroll refrigeration compressor of the car air conditioner.

[0193] Description of Reference Numerals

[0194] 1. 1' shaft seal

[0195] 2 Sealing lip

[0196] 3 Outer lips

[0197] 4 Base end

[0198] 5 Grooves

[0199] 6 Rotation axis

[0200] 7 Housing

[0201] 8 Annular groove

[0202] 9 Compression mechanism

[0203] 10 Compression chamber

[0204] 11 Fixed rotor

[0205] 12 Movable rotor

[0206] 13 Exhaust port

[0207] 14 Testing Machine

[0208] 15 Shaft seal

[0209] 16 Rotation axis

[0210] 17 Outer peripheral side housing

[0211] 18 Inner peripheral side shell

[0212] 19 O-ring

Claims

1. A shaft seal, which is an annular shaft seal that is in close contact with the outer peripheral surface of a rotating shaft to seal a sealing fluid, characterized in that: The gap between the rotating shaft and the housing on which the shaft seal is installed is divided into a high-pressure side and a low-pressure side by the shaft seal; The shaft seal is an injection molded body that is substantially U-shaped in an axial cross-sectional view, and includes a sealing lip portion that extends toward the high-pressure side and slides with the rotating shaft, and an outer lip portion that is provided on the outer diameter side relative to the sealing lip portion; The sealing lip has an inclination angle of 5° to 20° relative to the outer peripheral surface of the rotating shaft, and in the axial cross-sectional view of the shaft seal, the length of the sealing lip is 2.0 mm to 6.5 mm. The shaft seal has a bending elastic modulus of 200 MPa to 2400 MPa based on ASTM D790.

2. The shaft seal according to claim 1, characterized in that: The inner peripheral surface of the shaft seal is formed to continuously reduce in diameter from the back surface to the front end portion, and the outer peripheral surface of the shaft seal is formed to continuously expand in diameter from the back surface to the front end portion.

3. The shaft seal according to claim 1 or 2, characterized in that: The shaft seal is formed of a resin composition or a thermoplastic elastomer composition.

4. The shaft seal according to claim 1 or 2, characterized in that: The shaft seal is formed of a resin composition containing an ethylene-tetrafluoroethylene copolymer resin or a tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin as a main component.

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