Shaft seal

Abstract

To provide a shaft seal that can downsize a device and can reduce rotation torque.SOLUTION: A shaft seal 1 is an annular shaft seal for sealing sealed fluid by being in close contact with an outer peripheral surface of a rotating shaft 6. A gap between the rotating shaft 6 and a housing 7 fitted with the shaft seal 1 is partitioned into a high-pressure side and a low-pressure side by the shaft seal 1. The shaft seal 1 comprises a seal lip part 2 extending to the high-pressure side and to be slid on the rotating shaft 6. A lip length L2 of the lip part 2 is 1.0 mm or more and less than 2.0 mm, and a lip thickness t2 is 0.3 mm or more and 0.7 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shaft seal for a rotating shaft, and more particularly to a shaft seal for a rotating shaft of a scroll compressor for an in-vehicle air conditioner. [Background technology]

[0002] In recent years, as the electrification of automobiles has progressed, there has been a demand for energy conservation in various devices. For example, there is a strong demand for a reduction in the electricity consumption of on-board air conditioners (car air conditioners). To achieve this, it is necessary to make the devices more compact and increase their efficiency by reducing the rotational torque, and measures covering every detail of the components are essential.

[0003] The compressors of vehicle air conditioners use seals to prevent leakage of refrigerant and refrigeration oil. For example, in scroll compressors that have a compression mechanism that combines a fixed scroll and a movable scroll that orbits relative to the fixed scroll, a shaft seal is attached to the rotating shaft that drives the compression mechanism.

[0004] Patent Document 1 discloses a shaft seal used in a scroll compressor for an automotive air conditioner. The shaft seal described in Patent Document 1 has a generally U-shaped cross section in the axial direction, and includes a seal lip portion extending toward the high-pressure side and sliding against the rotating shaft, and an outer lip portion provided radially outward of the seal lip portion. The document discloses that the inclination angle of the seal lip portion relative to the outer circumferential surface of the rotating shaft is 5° to 20°, and the length of the seal lip portion in the axial cross section of the shaft seal is 2.0 mm to 6.5 mm. This shaft seal can exert an appropriate tension force on the rotating shaft, reducing rotational torque and providing excellent sealing properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 117601 Summary of the Invention [Problem to be solved by the invention]

[0006] The shaft seal described in Patent Document 1 is said to be able to reduce rotational torque when the length of the seal lip portion is within the above-mentioned specified range. However, it has been pointed out that if the length of the seal lip portion is shortened, the seal lip portion will be less likely to flex and the tension force will increase, which could increase the rotational torque, which could pose a challenge when it comes to downsizing the device.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a shaft seal that can reduce the size of the device and reduce the rotational torque. [Means for solving the problem]

[0008] The shaft seal of the present invention is an annular shaft seal that fits tightly against the outer peripheral surface of a rotating shaft, and is characterized in that it has a seal lip portion that slides against the rotating shaft, and the lip length of the seal lip portion is 1.0 mm or more and less than 2.0 mm, and the lip thickness is 0.3 mm or more and 0.7 mm or less.

[0009] When the inner diameter of the shaft seal before the rotary shaft is assembled is d and the outer diameter of the rotary shaft is D, the interference (Dd) between the shaft seal and the rotary shaft is 0.1 mm to 0.8 mm.

[0010] The interference (Dd) is characterized in that it is 0.2 mm to 0.6 mm.

[0011] The shaft seal has a generally U-shaped cross section in the axial direction, has an outer lip portion provided radially outward of the seal lip portion, and is characterized in that the lip thickness of the seal lip portion is thinner than the lip thickness of the outer lip portion.

[0012] The shaft seal is a molded article of a thermoplastic elastomer composition, and is characterized by having a flexural modulus according to ASTM D790 of 200 MPa to 2400 MPa.

[0013] The shaft seal is a shaft seal that fits tightly against the outer peripheral surface of the rotating shaft to seal the sealed fluid, and is characterized in that the gap between the rotating shaft and the housing in which the shaft seal is attached is divided into a high-pressure side and a low-pressure side by the shaft seal, and the seal lip portion extends to the high-pressure side and slides against the rotating shaft.

[0014] The rotating shaft has an outer diameter of φ15 mm to φ30 mm.

[0015] The shaft seal is characterized in that it is a shaft seal used for a rotating shaft in a scroll compressor for an in-vehicle air conditioner. [Effects of the Invention]

[0016] The shaft seal of the present invention has a lip length of the seal lip portion of 1.0 mm or more but less than 2.0 mm, and a lip thickness of 0.3 mm or more but 0.7 mm or less, which allows the device to be made more compact and appropriately reduces the tension force of the seal lip portion on the rotating shaft, thereby reducing the rotational torque.

[0017] The interference (Dd) between the shaft seal and the rotating shaft is 0.1 mm to 0.8 mm, so the rotational torque can be further reduced without compromising the sealing performance. In particular, the interference (Dd) is 0.2 mm to 0.6 mm, so it is easier to reduce the rotational torque while maintaining the sealing performance.

[0018] The shaft seal is a molded product of a thermoplastic elastomer composition, and has a flexural modulus of elasticity of 200 MPa to 2400 MPa according to ASTM D790, making it resistant to wear and providing excellent sealing properties. It also exerts a moderate tension, further contributing to low torque. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing an example of a shaft seal of the present invention attached to a rotating shaft. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the shaft seal of FIG. 1 before installation. [Figure 3] FIG. 2 is a schematic cross-sectional view showing a compression mechanism of the scroll compressor. [Figure 4] FIG. 1 is a schematic diagram of a measurement test of rotational torque. DETAILED DESCRIPTION OF THE INVENTION

[0020] A compressor incorporating the shaft seal of the present invention will be described with reference to FIG. 1. FIG. 1 shows an axial cross-sectional view of the shaft seal mounted on a rotating shaft. The shaft seal of the present invention is intended for mounting on a rotating shaft with a relatively small diameter. As shown in FIG. 1, the shaft seal 1 is an annular member having a generally U-shaped cross-section in the axial direction. The seal seal 1 has a seal lip portion 2 extending axially to one side on the inner diameter side of the seal and an outer lip portion 3 located on the outer diameter side of the seal lip portion 2. The seal lip portion 2 and the outer lip portion 3 each extend from a base end portion 4. The seal lip portion 2, the outer lip portion 3, and the base end portion 4 form a recessed groove 5. The housing 7 has an insertion hole 7a through which the rotating shaft 6 is inserted, and an annular groove 8 is formed around the insertion hole 7a. The shaft seal 1 is mounted in this annular groove 8, and as the rotating shaft 6 rotates around axis O, the seal lip portion 2 slides along the rotating shaft 6.

[0021] In FIG. 1, shaft seal 1 is installed in annular groove 8 so that seal lip portion 2 and outer lip portion 3 each extend toward high-pressure side H. In this case, the recessed groove 5 side corresponds to high-pressure side H, and the back surface 4a side of base end portion 4 corresponds to low-pressure side L. When installed, the tip end of outer lip portion 3 of shaft seal 1 contacts the side wall of annular groove 8 so as to be non-rotatable, and the tip end of seal lip portion 2 contacts the outer peripheral surface of rotating shaft 6 so as to be non-rotatable. In addition, back surface 4a of base end portion 4 is in close contact with the bottom wall of annular groove 8. Meanwhile, spaces are formed between outer lip portion 3 and the side wall, and between seal lip portion 2 and rotating shaft 6.

[0022] The inventors have discovered that it is possible to achieve both sealing performance and low torque while miniaturizing the device by optimizing the lip length L2 and lip thickness t2 of the seal lip portion 2 in the axial cross-section of the shaft seal 1. Specifically, the shaft seal 1 is characterized in that the lip length L2 of the seal lip portion 2 is 1.0 mm or more and less than 2.0 mm, and the lip thickness t2 is 0.3 mm or more and 0.7 mm or less.

[0023] The outer diameter D of the rotating shaft 6 on which the shaft seal 1 is mounted is not particularly limited, but from the viewpoint of miniaturizing the device, it is preferably φ15mm to φ30mm, more preferably φ16mm to φ26mm, and even more preferably φ17mm to φ22mm.

[0024] Setting the lip length L2 to less than 2.0 mm reduces the space required to install the shaft seal 1, leading to further miniaturization of the device. The lip length L2 is preferably 1.2 mm or more and less than 2.0 mm, more preferably 1.3 mm or more and less than 1.9 mm, and even more preferably 1.4 mm or more and less than 1.8 mm.

[0025] On the other hand, if the lip length L2 is less than 2.0 mm, the seal lip portion 2 will not bend easily, resulting in a high tension force and a risk of increasing rotational torque, but in the present invention, the lip thickness t2 is set to 0.3 mm or more and 0.7 mm or less, thereby appropriately reducing the tension force of the seal lip portion 2 and reducing rotational torque. The lip thickness t2 is preferably 0.4 mm to 0.7 mm, and more preferably 0.5 mm to 0.7 mm.

[0026] The dimensions of the shaft seal 1 will be explained with reference to Figure 2. Figure 2 shows the shaft seal in a state (free state) before it is installed in the housing. In the shaft seal 1, the seal lip portion 2 and the outer lip portion 3 are formed so that their tip ends 2a, 3a are inclined away 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 Figure 2, the inner diameter dimension d indicates the distance between the tip ends 2a of the opposing seal lip portions 2. In Figure 2, the inner circumferential surface of the shaft seal 1 is formed so that its diameter continuously decreases from the back surface 4a to the tip end 2a, and the outer circumferential surface of the shaft seal 1 is formed so that its diameter continuously increases from the back surface 4a to the tip end 3a.

[0027] The seal lip portion 2 has a predetermined lip length L2 on its outer circumferential surface. As shown in FIG. 2, the lip length L2 is the linear length from a corner (on the seal lip portion 2 side) of the bottom surface 4b of the shaft seal 1 to the apex of the outer diameter side of the tip portion 2a of the seal lip portion 2. Also, in FIG. 2, the back surface 4a and the bottom surface 4b are formed as flat surfaces that are approximately parallel to a plane perpendicular to the axis of the shaft seal 1. This facilitates close contact with the bottom wall of the annular groove. The bottom surface 4b may be an inclined surface, and for example, the thickness t4 of the base end portion 4 may be reduced toward the seal lip portion 2. The corners of the bottom surface 4b may be curved to form an approximately arc-shaped surface.

[0028] 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 straight line length from a corner (on the outer lip portion 3 side) of the bottom surface 4b of the shaft seal 1 to the apex of the inner diameter side of the tip portion 3a of the outer lip portion 3. The lip length L3 is, for example, 1.5 mm to 2.5 mm.

[0029] Here, the lip length L3 of the outer lip portion 3 may be the same as the lip length L2 of the seal lip portion 2, but since the pressure-receiving area becomes larger, it is preferably longer than the lip length L2 of the seal lip portion 2. The ratio of the lip length L2 to the lip length L3 (L2 / L3) is, for example, 0.50 to 0.90, and preferably 0.60 to 0.80.

[0030] Furthermore, it is preferable that the lip thickness t2 of the seal lip portion 2 is thinner than the lip thickness t3 of the outer lip portion 3. In this case, the lip thickness t3 is, for example, 0.8 mm to 1.5 mm. Furthermore, in terms of the relationship between the lip thickness t2, the lip thickness t3, and the thickness t4 of the base end portion 4, it is preferable that t3≧t4>t2.

[0031] Returning to FIG. 1, the shaft seal 1 prevents fluid on the high-pressure side H from leaking to the low-pressure side L by having the seal lip portion 2 come into close contact with the outer circumferential surface of the rotating shaft 6. Examples of the fluid include refrigerant, oil, and a mixture of refrigerant and oil. The fluid pressure is, for example, 0.3 MPa to 1.0 MPa, or may be 0.5 MPa to 1 MPa. Even at a relatively high pressure of 0.5 MPa to 1 MPa, the shaft seal of the present invention can keep the rotational torque low.

[0032] Here, to ensure the sealing performance of the shaft seal, the inner diameter d (see Figure 2) of the shaft seal 1 before installation must be smaller than the outer diameter D of the rotating shaft 6. In other words, when the shaft seal 1 is assembled onto the rotating shaft 6, the shaft seal 1 must have some interference.

[0033] The interference (Dd) between the shaft seal 1 and the rotating shaft 6, which is the difference between the outer diameter D and the inner diameter d, is not particularly limited, but is, for example, about 0.1 mm to 1.0 mm, and preferably 0.1 mm to 0.8 mm. By setting the interference (Dd) within the above range, it becomes easier to reduce the rotational torque without impairing the sealing performance. The interference (Dd) is more preferably 0.2 mm to 0.7 mm, and may be 0.2 mm to 0.5 mm, or may be 0.5 mm to 0.7 mm. Furthermore, the relationship (Dd) / D preferably satisfies 0.003 to 0.05, more preferably 0.004 to 0.05, and even more preferably 0.005 to 0.05. When (Dd) / D, obtained by dividing the interference (Dd) by the outer diameter dimension D of the rotating shaft, is within the above range, the rotational torque can be easily reduced without impairing the sealing performance.

[0034] In order to reduce the rotational torque, it is preferable to form a space between the seal lip portion 2 and the rotating shaft 6, as shown in Fig. 1. In this case, the base end portion 4 does not contact the rotating shaft 6 in the mounted state.

[0035] The shaft seal of the present invention is not limited to the configuration shown in FIG.

[0036] 1 and 2 show a shaft seal that is substantially U-shaped in cross section in the axial direction, but the shaft seal of the present invention is not limited to this. For example, the shaft seal may be provided with a lip portion other than the seal lip portion and the outer lip portion (such as a dust lip that slides against the rotating shaft), or the shaft seal may have a shape that does not have an outer lip portion (for example, a shape consisting of the seal lip portion 2 and a fixed portion without the outer lip portion 3).

[0037] In the compressor of Fig. 1, a compression mechanism is provided on the high-pressure side H of the housing 7. The compression mechanism may be of any type, such as a scroll type or a swash plate type, as long as it compresses the fluid by rotation of the rotary shaft 6. For example, in the case of a scroll type, the compression mechanism is configured by combining a fixed scroll and a movable scroll that orbits relative to the fixed scroll.

[0038] FIG. 3 shows a partial cross-sectional view of a scroll-type compression mechanism. As shown in FIG. 3, the compression mechanism 9 includes a fixed rotor 11 having a base plate 11a and a fixed scroll blade 11b standing upright on the base plate 11a, and a movable rotor 12 having a base plate 12a and a movable scroll blade 12b standing upright on the base plate 12a. The fixed rotor 11 and the movable rotor 12 are eccentrically meshed with each other, forming a compression chamber 10 therebetween. The movable rotor 12 is directly or indirectly connected to the rotating shaft. 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, compressing the fluid. The compressed fluid is discharged from a discharge pipe through a discharge port 13 at the center of the movable rotor 12 and flows into the refrigeration cycle. The refrigeration cycle fluid (such as refrigerant gas) is introduced into the compression chamber 10 through a suction port (not shown).

[0039] The shaft seal of the present invention is made of a thermoplastic elastomer composition or a resin composition. For example, the shaft seal is a molded article of the thermoplastic elastomer composition. In this case, the flexural modulus measured in accordance with ASTM D790 is preferably 200 MPa to 2400 MPa. When the flexural modulus is 200 MPa or more, the seal is less susceptible to wear and less prone to deterioration in sealing performance. When the flexural modulus is 2400 MPa or less, the tension force of the shaft seal on the rotating shaft tends to be low, making it easier to reduce rotational torque. The flexural modulus is preferably 200 MPa to 1800 MPa, more preferably 400 MPa to 800 MPa.

[0040] In the thermoplastic elastomer composition, the elastomer serving as the main component is not limited, and polyolefin elastomers, polyester elastomers, polyamide elastomers, etc. can be used. From the viewpoint of heat resistance and chemical resistance, polyester elastomers are particularly preferred. Polyester elastomers contain hard segments and soft segments, with polyester units used in the hard segments and polyether units or polyester units used in the soft segments. Polyester elastomers are polyester-polyether or polyester-polyester multiblock copolymers.

[0041] When the shaft seal is a molded body of a resin composition, the resin that is the main component (base resin) is not limited, and examples that can be used include polyamide (PA) resin, polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, polyamide imide (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, polyether sulfone resin, polysulfone resin, polyphenyl sulfone resin, polyarylate resin, polyetherimide resin, polyimide resin, and polyester resin.

[0042] Among the above resins, it is preferable to use PA resin, PFA resin, FEP resin, ETFE resin, or vinylidene fluoride resin, which are excellent in heat resistance, chemical resistance, and flexibility and can be injection molded. Because these resins have excellent chemical resistance and oil resistance, they are suitable for shaft seals for the rotating shaft of a compressor used in the presence of a fluid containing a mixture of refrigerant and refrigeration oil, for example.

[0043] The above-mentioned thermoplastic elastomer composition and resin composition may be blended with a solid lubricant such as PTFE resin, graphite, or molybdenum disulfide for the purpose of improving friction and wear properties.

[0044] The amount of solid lubricant blended is preferably 1 to 40% by volume, more preferably 1 to 20% by volume, and even more preferably 10 to 20% by volume, relative to 100% by volume of the thermoplastic elastomer composition or resin composition. If the amount exceeds 40% by volume, the elongation properties of the resin composition or thermoplastic elastomer composition may be reduced, and cracks may occur when the shaft seal is assembled into the rotating shaft.

[0045] The thermoplastic elastomer composition or resin composition may contain fibrous reinforcing materials such as carbon fiber, glass fiber, and aramid fiber, spherical fillers such as spherical silica, scaly reinforcing materials such as mica, sliding reinforcing materials such as calcium phosphate and calcium sulfate, and microfiber reinforcing materials such as potassium titanate whiskers, to the extent that the effects of the present invention are not impaired. Colorants such as carbon black and iron oxide may also be added. These may be added alone or in combination.

[0046] The shaft seal of the present invention can be used for the rotating shaft (main shaft) of a scroll compressor for an automotive air conditioner. The scroll compressor may be belt-driven using engine power or motor-driven without using engine power. The shaft seal of the present invention can be used in applications other than compressors.

[0047] The shaft seal of the present invention is molded by injection molding, for example, using a general injection molding machine for thermoplastic resins. The materials constituting the thermoplastic elastomer composition or the resin composition can be mixed, as needed, using a Henschel mixer, ball mixer, ribbon blender, or the like, and then melt-kneaded in a melt extruder such as a twin-screw kneading extruder to obtain molding pellets. The filler may be added by side feeding during melt-kneading in a twin-screw extruder, or the like. The molding pellets are then injection molded to form a shaft seal. [Example]

[0048] Examples 1 to 4, Comparative Examples 1 to 4 In Examples 1 to 4 and Comparative Examples 1 to 4, shaft seal performance tests were conducted by varying the lip thickness, interference, and material. First, the thermoplastic elastomer composition was pelletized using a twin-screw kneading extruder. The resulting pellets were injection-molded to form shaft seals with the shape shown in Figure 2. Comparative Examples 1 and 3 were used directly in the rotational torque test, while Examples 1 to 4 were machined to have the lip thicknesses shown in Table 1. For Comparative Examples 2 and 4, PTFE shaft seals were fabricated with the same shape and dimensions as Comparative Examples 1 and 3. In Examples 1 and 2 and Comparative Examples 1 and 2, a rotating shaft with an outer diameter D of 20.0 mm was used, while in Examples 3, 4 and Comparative Examples 3 and 4, a rotating shaft with an outer diameter D of 19.6 mm was used, thereby varying the interference. The thermoplastic elastomer composition used in Example 1 and other examples was also molded for a bending test to measure the flexural modulus. Details of each sample are shown in Table 1.

[0049] [Table 1]

[0050] <Bending test> The molded article of the thermoplastic elastomer composition was subjected to a bending test in accordance with ASTM D790 to measure the bending modulus of elasticity. As a result, the bending modulus of the molded article of the thermoplastic elastomer composition was found to be 500 MPa.

[0051] <Rotational torque test> Performance test 1 The shaft seals of Examples 1 and 2 and Comparative Examples 1 and 2, each with an inner diameter d of 19.4 mm, were attached to a rotating shaft with an outer diameter D of 20.0 mm, and a rotational torque test was conducted with the interference (Dd) between the shaft seal and the rotating shaft adjusted to 0.6 mm in diameter, to examine the lip thickness and material.

[0052] Using the rotational torque tester shown in FIG. 4, a rotational torque test was carried out under the following conditions to measure the amount of oil leakage and the rotational torque. <Test conditions> Rotating shaft: Material: S45C Rotation speed: 3000 rpm, 7000 rpm Hydraulic pressure: 0.3MPa, 0.5MPa, 1.0MPa Oil temperature: 100℃ Refrigerant oil: Polyalkylene glycol oil Test duration: 5 minutes

[0053] As shown in Figure 4, the housing of the testing machine 14 is composed of an outer housing 17 and an inner housing 18. At the mating surface of these housings, an O-ring 19 is placed in the outer groove of the inner housing 18 to prevent refrigeration oil from leaking from the mating surface. The shaft seal 15 is in close contact with the rotating shaft 16 and slides against the outer surface of the rotating shaft 16 as the rotating shaft 16 rotates. Refrigeration oil was pumped and supplied to the space inside the housing. As shown in Figure 4, the refrigeration oil flows in through the inlet passage 17b, passes through the housing interior, and flows out through the outlet passage 17c. The oil leakage amount is based on the amount of refrigeration oil leaking between the rotating shaft 16 and the insertion hole 17a, and is the average value for five minutes after the start of the test. The rotational torque is the average value for five minutes after the start of the test. The results are shown in Table 2.

[0054] [Table 2]

[0055] As shown in Table 2, in both the Examples and Comparative Examples, the interference with the rotating shaft was 0.6 mm, which resulted in strong adhesion to the rotating shaft and very little oil leakage of 1 ml / min or less. Meanwhile, when comparing the results of rotational torque between shaft seals made of thermoplastic elastomer, when the lip thickness t2 was 0.3 mm to 0.7 mm (Examples 1 and 2), the rotational torque was 0.03 N·m to 0.08 N·m, whereas when the lip thickness t2 was 1.0 mm (Comparative Example 1), the rotational torque was 0.06 N·m to 0.12 N·m, meaning that Examples 1 and 2 had relatively low torque.

[0056] Even when compared to a shaft seal made of PTFE, which slides more easily than a shaft seal made of thermoplastic elastomer, and with a lip thickness t2 of 1.0 mm (Comparative Example 2), Examples 1 and 2 generally had lower torque. Thus, Examples 1 and 2, in which the lip thickness t2 of the seal lip portion is 0.3 mm to 0.7 mm, tended to have lower torque than Comparative Examples 1 and 2, in which the lip thickness t2 was 1.0 mm.

[0057] Furthermore, when comparing Example 1 and Example 2, Example 1, which has a smaller lip thickness t2, resulted in lower torque. In both Examples 1 and 2, the rotational torque tended to increase as the oil pressure increased.

[0058] Performance test 2 The shaft seals of Examples 3 and 4 and Comparative Examples 3 and 4, each with an inner diameter d of 19.4 mm, were attached to a rotating shaft with an outer diameter D of 19.6 mm, and a rotational torque test was conducted with the interference (Dd) between the shaft seal and the rotating shaft adjusted to 0.2 mm in diameter to examine the lip thickness and material. Apart from the interference, the test was conducted using the same testing machine and under the same conditions as in Performance Test 1.

[0059] [Table 3]

[0060] As shown in Table 3, in Performance Test 2, the interference was smaller than in Performance Test 1, which is thought to result in a decrease in adhesion with the rotating shaft. However, in Examples 3 and 4, the oil leakage amount was 1 ml / min or less, just like in Performance Test 1. In contrast, in Comparative Example 3, the oil leakage amount increased significantly compared to Performance Test 1. This oil leakage amount tended to increase as the oil pressure decreased. The oil leakage amount in Comparative Example 4 was 1 ml / min or less.

[0061] From Table 3, it was found that Examples 3 and 4, which have thinner seal lip portions than Comparative Examples 3 and 4, tended to have smaller oil leakage amounts and reduced rotational torque. The reason why the oil leakage amount in Comparative Example 3 was significantly greater than in Performance Test 1 is thought to be that the seal lip portion of Comparative Example 3 was thicker than the seal lip portions of Examples 3 and 4, which increased the rigidity of the seal lip portion and reduced adhesion to the rotating shaft under conditions where the interference was relatively small.

[0062] Comparing Example 3 and Example 4, similar to Performance Test 1, Example 3, which has a smaller lip thickness t2, resulted in a lower torque.

[0063] Furthermore, in Examples 1 to 4, when the interference was 0.2 mm (Performance Test 2) and 0.6 mm (Performance Test 1), the smaller the interference was, the lower the torque was.

[0064] As described above, in the present invention, for a shaft seal to be attached to a rotating shaft with a relatively small diameter (for example, an outer diameter of 15 mm to 30 mm), the lip length and lip thickness (and also interference, etc.) of the seal lip portion of the shaft seal are optimized, thereby enabling the device to be made smaller while achieving both sealing performance and low torque. [Industrial Applicability]

[0065] The shaft seal of the present invention can reduce the size of the device and rotational torque, and therefore can be widely used as a shaft seal that seals a sealed fluid while sliding against the outer circumferential surface of a rotating shaft, and is particularly suitable as a shaft seal for a rotating shaft that rotates the compression mechanism of a scroll compressor for an automotive air conditioner. [Explanation of symbols]

[0066] 1 Shaft seal 2 Seal lip 3 Outer lip 4 Proximal end 5 groove 6 Rotation Axis 7. Housing 8 Annular groove 9 Compression mechanism 10 Compression Chamber 11 Fixed rotor 12 Moving rotor 13 Outlet 14 Testing Machine 15 Shaft seal 16 Rotation Axis 17 Outer housing 18 Inner housing 19 O-ring

Claims

1. An annular shaft seal that fits tightly against the outer circumferential surface of a rotating shaft, The shaft seal is an annular member having a substantially U-shaped cross section in the axial direction, and extends from a base end to one side in the axial direction. The shaft seal includes a seal lip portion on the seal inner diameter side that slides against the rotating shaft, and an outer lip portion provided on the seal outer diameter side of the seal lip portion, The lip length of the seal lip portion is 1.0 mm or more and less than 2.0 mm, and the lip thickness is 0.3 mm or more and 0.7 mm or less, A shaft seal, characterized in that the relationship between the thickness t 2 of the seal lip portion, the thickness t 3 of the outer lip portion, and the thickness t 4 of the base end portion satisfies t 3 ≧t 4 >t 2 .

2. 2. The shaft seal according to claim 1, wherein the shaft seal is a molded article of a thermoplastic elastomer composition, and has a flexural modulus of elasticity of 200 MPa to 2400 MPa according to ASTM D790.

3. The shaft seal is a shaft seal that comes into close contact with an outer peripheral surface of the rotating shaft to seal in a sealed fluid, 3. The shaft seal according to claim 1, wherein the gap between the rotating shaft and the housing in which the shaft seal is mounted is divided into a high-pressure side and a low-pressure side by the shaft seal, and the seal lip portion extends to the high-pressure side and slides against the rotating shaft.

4. 4. The shaft seal according to claim 1, wherein the outer diameter of the rotary shaft is 15 mm to 30 mm.

5. 5. The shaft seal according to claim 1, wherein the shaft seal is used for a rotary shaft of a scroll compressor for an in-vehicle air conditioner.

6. An annular shaft seal that seals a sealed fluid by adhering to the outer peripheral surface of a rotating shaft, The shaft seal has a seal lip portion that slides against the rotating shaft, and the seal lip portion has a lip length of 1.0 mm or more and less than 2.0 mm and a lip thickness of 0.3 mm or more and 0.7 mm or less, A shaft seal characterized in that the gap between the rotating shaft and the housing in which the shaft seal is mounted is divided into a high-pressure side and a low-pressure side by the shaft seal, and the seal lip portion extends to the high-pressure side and slides against the rotating shaft.

7. An annular shaft seal that fits tightly against the outer circumferential surface of a rotating shaft, The shaft seal has a seal lip portion that slides against the rotating shaft, and the seal lip portion has a lip length of 1.0 mm or more and less than 2.0 mm and a lip thickness of 0.3 mm or more and 0.7 mm or less, The shaft seal is characterized in that it is a shaft seal used for a rotating shaft in a scroll compressor for an in-vehicle air conditioner.

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