Shaft seal

Abstract

Provided is a shaft seal capable of reducing the variation in the inner diameter contraction amount at the time of installation in a housing, while reducing the rotational torque of the shaft seal, thereby suppressing variation in the rotational torque. A shaft seal 5 is an annular shaft seal provided between a rotary shaft 6 and a housing 7, and is provided with an inner diameter lip 2, and an outer diameter lip 1 provided on the outer diameter side of the inner diameter lip 2. In the shaft seal 5 in a free state, when the height of the outer diameter lip 1 is L1 and the height of the inner diameter lip 2 is L2, 0.5 ≤ (L1 / L2) ≤ 0.9 is satisfied, and the inclination angle with respect to the axial direction of the outer diameter lip 1 is larger than 5°.

Description

Shaft seal

[0001] The present invention relates to a shaft seal for a rotating shaft, and more particularly to a shaft seal for a compressor for a car air conditioner.

[0002] As the electrification of automobiles progresses, the demand for electric compressors, including those in car air conditioners, is increasing year by year. One way to save energy in automobiles is to reduce the power loss of electric compressors. To achieve stable low power loss, it is necessary to accurately estimate the torque loss of the device at the unit design stage. Therefore, in addition to reducing the torque of the shaft seal, which is one of the components, reducing torque variation will make it easier to control torque loss when the shaft seal is incorporated into the unit.

[0003] For example, Patent Document 1 discloses a shaft seal used in a scroll compressor for a car air conditioner. This shaft seal is inserted into a mounting groove in the shaft to seal the refrigerant oil between the shaft and the housing. The shaft seal expands in diameter when subjected to hydraulic pressure (usually about 0.4 MPa) from the sealing side, and each lip seals the refrigerant oil by coming into close contact with the inner circumferential surface of the housing and the outer circumferential surface of the shaft, respectively.

[0004] The shaft seal in Patent Document 1 is disclosed as having a generally U-shaped cross section in the axial direction, an inner lip extending to the high-pressure side and sliding against the rotating shaft, and an outer lip provided on the outer diameter side of the inner lip, with the inner lip being inclined at an angle of 5° to 20° relative to the outer peripheral surface of the rotating shaft, and the length of the inner lip in the axial cross section of the shaft seal being 2.0 mm to 6.5 mm. This shaft seal is said to be able to exert an appropriate tension force on the rotating shaft, reduce rotational torque, and have excellent sealing properties.

[0005] International Publication No. 2021 / 117601

[0006] Shaft seals are typically installed with an interference between the outer lip and the inner peripheral surface of the housing. When installed with interference, the shaft seal shrinks inward. The amount of shrinkage of the shaft seal inward affects the pressing force of the inner lip against the outer peripheral surface of the shaft. Because the outer lip of a shaft seal is fixed to the inner peripheral surface of the housing and the inner lip slides against the outer peripheral surface of the shaft, the pressing force of the inner lip against the outer peripheral surface of the shaft affects the rotational torque. In other words, it is believed that stabilizing the rotational torque can be achieved by reducing the variation in the amount of shrinkage of the shaft seal inward due to the interference of the outer lip. While Patent Document 1 examines the length of the inner lip, it does not consider the outer lip at all.

[0007] The present invention has been made in consideration of these circumstances, and aims to provide a shaft seal that can reduce the rotational torque of the shaft seal while reducing the variation in the amount of inner diameter contraction when installed in a housing by optimizing the dimensions of the outer diameter lip, thereby suppressing the variation in rotational torque.

[0008] The shaft seal of the present invention is an annular shaft seal provided between a rotating shaft and a housing, the shaft seal comprising an inner lip and an outer lip provided radially outward of the inner lip, wherein, in the shaft seal in a free state, when the height of the outer lip is L1 and the height of the inner lip is L2, 0.5≦(L1 / L2)≦0.9, and the inclination angle of the outer lip with respect to the axial direction is greater than 5°. Also, in the shaft seal, the inner lip slides in close contact with the outer peripheral surface of the rotating shaft, and the outer lip is fitted into the housing with interference.

[0009] In the present invention, the term "free state" refers to a state in which no external force is acting on the shaft seal, such as a state in which a rotating shaft is not inserted and the seal is not attached to a housing. The inclination angle of the outer lip relative to the axial direction refers to the angle between the outer peripheral surface of the outer lip and the axial direction.

[0010] When the outer diameter of the shaft seal in a free state is d and the inner diameter of the housing is D, the interference (d-D) between the shaft seal and the housing is 0.2 mm to 0.7 mm.

[0011] The tilt angle is 9° to 17°.

[0012] The shaft seal is characterized in that 0.5≦(L1 / L2)≦0.7.

[0013] When the outer diameter of the shaft seal in a free state is d and the inner diameter of the housing is D, the interference (d-D) between the shaft seal and the housing is 0.2 mm to 0.7 mm, the inclination angle is 9° to 17°, and 0.5≦(L1 / L2)≦0.7 is satisfied for the shaft seal.

[0014] In the shaft seal, the lip thickness of the outer lip is thinner than the lip thickness of the inner lip.

[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.

[0016] In the shaft seal of the present invention, the relationship between the outer lip height L1 and the inner lip height L2 is 0.5≦(L1 / L2)≦0.9, and the inclination angle of the outer lip relative to the axial direction is greater than 5°. This ensures low torque, while reducing the variation in the amount of inner diameter contraction when installed in a housing compared to conventional configurations where (L1 / L2) is 1 or more (see Figure 8), resulting in a shaft seal with reduced variation in rotational torque.

[0017] In the case of a shaft seal, if the outer diameter of the shaft seal in a free state is d and the inner diameter of the housing is D, the interference (d-D) between the shaft seal and the housing is 0.2 mm to 0.7 mm, which makes it easy to keep the press-fit force on the housing appropriate, which ultimately leads to ensuring sealing performance.

[0018] In the present invention, by setting (L1 / L2) within the above-mentioned range, the press-fit force (lip rigidity) tends to be larger compared to conventional configurations. However, for example, by making the lip thickness of the outer diameter lip thinner than the lip thickness of the inner diameter lip in the shaft seal, it is possible to prevent the press-fit force from becoming excessive, which results in ensuring sealing performance.

[0019] Fig. 2 is a diagram showing an example of a shaft seal of the present invention attached to a rotating shaft. Fig. 3 is an enlarged cross-sectional view of the shaft seal of Fig. 1 in a free state. Fig. 4 is a schematic cross-sectional view showing a compression mechanism part of a scroll compressor. Fig. 5 is a graph showing the relationship between L1 / L2 and the amount of change in inner diameter, etc. Fig. 6 is a graph showing the relationship between L1 / L2 and the press-fit force, etc. Fig. 7 is a schematic diagram of a measurement test of rotational torque. Fig. 8 is a graph showing the test results of rotational torque. Fig. 9 is a diagram showing the configuration of a conventional shaft seal.

[0020] The inventors of the present invention have conducted extensive research focusing on variations in rotational torque between shaft seals in order to stabilize the rotational torque of a rotating shaft supported by shaft seals installed in a housing. Surprisingly, they have found that the ratio of the outer lip height to the inner lip height affects the variations. The present invention is based on this finding.

[0021] A compressor incorporating a shaft seal according to 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. As shown in FIG. 1 , the shaft seal 5 is an annular member having a generally J-shaped cross-section. It includes an inner lip 2 extending axially to one side, located on the inner diameter side of the seal, and an outer lip 1 located on the outer diameter side of the seal relative to the inner lip 2. The inner lip 2 and the outer lip 1 each extend from a base end 3. In the shaft seal 5, the inner lip 2 is longer than the outer lip 1. The inner lip 2, the outer lip 1, and the base end 3 form a recessed groove 4. 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 5 is fitted into the annular groove 8 with interference. As the rotating shaft 6 rotates about axis O, the inner lip 2 slides along the rotating shaft 6.

[0022] In Figure 1, the shaft seal 5 is installed in the annular groove 8 so that the inner lip 2 and the outer lip 1 each extend toward the high-pressure side. In this case, the recessed groove 4 side corresponds to the high-pressure side, and the back surface 3a side of the base end 3 corresponds to the low-pressure side. When installed, the vicinity of the tip of the outer lip 1 of the shaft seal 5 contacts the side wall of the annular groove 8 so as to be non-rotatable, and the vicinity of the tip of the inner lip 2 contacts the outer peripheral surface of the rotating shaft 6 so as to be non-rotatable. In addition, the back surface 3a of the base end 3 is in close contact with the bottom wall of the annular groove 8. Meanwhile, spaces are formed between the outer lip 1 and the side wall, and between the inner lip 2 and the rotating shaft 6.

[0023] Here, the shaft seal 5 of the present invention can suppress variations in rotational torque while ensuring low torque performance by optimizing the ratio (L1 / L2) of the height L1 of the outer lip 1 in the free state to the height L2 of the inner lip 2 in the free state. As shown in Figure 2, the height L1 of the outer lip 1 in the free state is the distance in the height direction (axial direction X) from the back surface 3a of the base end 3 to the tip end 1a of the outer lip 1. Furthermore, the height L2 of the inner lip 2 in the free state is the distance in the height direction (axial direction X) from the back surface 3a of the base end 3 to the tip end 2a of the inner lip 2.

[0024] Details of the shaft seal 5 will be described with reference to Figure 2. Figure 2 shows an enlarged cross-sectional view of the shaft seal before it is installed in the housing (free state). In the shaft seal 5, the outer diameter lip and the inner diameter lip are formed so as to be inclined in the direction in which the tip ends 1a, 2a move away from each other. In Figure 2, the inner circumferential surface of the shaft seal 5 is formed so as to continuously decrease in diameter from the back surface 3a to the tip end 2a, and the outer circumferential surface of the shaft seal 5 is formed so as to continuously increase in diameter from the back surface 3a to the tip end 1a.

[0025] In the shaft seal 5, the outer lip height L1 in the free state is defined as L1, and the inner lip height L2 in the free state is defined as L2. The outer lip height L1 is smaller than the inner lip height L2 (L1<L2). Specifically, the relationship is 0.5≦(L1 / L2)≦0.9. In FIG. 2, the back surface 3a and the bottom surface of the recessed groove are formed as flat surfaces that are approximately parallel to a plane perpendicular to the axis of the shaft seal 5.

[0026] In a conventional shaft seal 35 (see FIG. 8 ), the height L1 of the outer lip 31 is greater than the height L2 of the inner lip 32 (L1 > L2) to increase the pressure-receiving area relative to the housing. In contrast, in the shaft seal 5 of the present invention, as shown in FIG. 2 , L1 is made smaller than L2 (specifically, L1 / L2 is set to 0.9 or less). This reduces the variation in the inner diameter of the shaft seal after press-fitting into the housing, as will be shown in the examples below, and as a result, reduces the variation in rotational torque. That is, by making the height L1 of the outer lip 1 relatively small, the reproducibility of the shaft seal state after press-fitting into the housing is excellent and the variation in the inner diameter of the shaft seal can be reduced. On the other hand, if the L1 / L2 ratio is too small, i.e., if the height L1 of the outer lip 1 is too small relative to the housing, the shaft seal may deform during assembly, potentially resulting in increased leakage due to poor assembly. Therefore, the L1 / L2 ratio is set to 0.5 or greater.

[0027] In the present invention, from the viewpoint of stabilizing the rotational torque, it is preferable that L1 / L2 is as small as possible. Specifically, L1 / L2 is preferably 0.5≦(L1 / L2)≦0.8, more preferably 0.5≦(L1 / L2)≦0.7, and may be 0.5≦(L1 / L2)≦0.6.

[0028] The height L1 of the outer lip 1 is, for example, 1.0 mm to 2.5 mm, and the height L2 of the inner lip 2 is, for example, 2.0 mm to 4.0 mm.

[0029] By setting L1 / L2 within the above range, the press-fit force (lip rigidity) tends to be larger than that of the conventional configuration. Therefore, it is preferable to also set the thickness of the outer lip, which affects the lip rigidity. Specifically, in the shaft seal 5, in order to prevent the outer lip from becoming too rigid, that is, to prevent the press-fit force from becoming too large, the lip thickness t １ , the lip thickness t of the inner diameter lip 2 ２ Furthermore, it is preferable that the lip thickness t １ , the thickness t of the base end portion 3 ３ It is preferable that the lip thickness is thinner than t１ is, for example, 0.3 mm to 0.7 mm.

[0030] In the shaft seal 5, the inclination angle θ of the outer lip 1 relative to the axial direction is greater than 5°. By making the inclination angle θ greater than 5°, sealing performance can be ensured, as shown in the sealing performance test described below. The upper limit of the inclination angle θ is, for example, 25°. The inclination angle θ is preferably 7° to 20°, and may be 9° to 20°, or may be 9° to 17°.

[0031] The outer diameter d of the shaft seal 5 is, for example, 35 mm or less, or 27 mm or less, or may be 23 mm or less. In the present invention, the outer diameter d of the shaft seal 5 refers to the maximum outer diameter of the shaft seal 5 in a free state, and in Figure 2, it indicates the distance between the outer edges of the tip portions 1a of the opposing outer diameter lips 1.

[0032] As shown in Figure 1, the shaft seal 5 prevents the high-pressure fluid from leaking to the low-pressure fluid by having the inner lip 2 tightly contact the outer circumferential surface of the rotating shaft 6 and the outer lip 1 tightly contact the side wall of the annular groove 8. 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, and 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.

[0033] Here, the shaft seal 5 is fitted with an interference fit into the housing 7. That is, the outer diameter d of the shaft seal 5 in a free state must be larger than the inner diameter D of the housing 7 (see FIG. 2).

[0034] The interference (d-D) between the shaft seal 5 and the housing 7, which is the difference between the outer diameter d of the shaft seal and the inner diameter D of the housing, is not particularly limited, but is, for example, about 0.1 mm to 1.0 mm, preferably 0.2 mm to 0.7 mm, and may be 0.4 mm to 0.7 mm. Setting the interference (d-D) within the above range makes it easier to apply an appropriate press-fit force, which in turn makes it easier to ensure sealing performance.

[0035] The shaft seal of the present invention is not limited to the configuration shown in Fig. 2. For example, while the bottom surface of the recessed groove in Fig. 2 is configured as a flat surface, the bottom surface may be arc-shaped. Also, the corners of the shaft seal (including the tip of each lip) may be provided with an inclined surface such as a chamfer.

[0036] In the compressor of Figure 1, a compression mechanism is provided on the high-pressure side 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.

[0037] 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 fixed scroll blades 11b standing upright on the base plate 11a, and a movable rotor 12 having a base plate 12a and movable scroll blades 12b standing upright on the base plate 12a. The fixed rotor 11 and the movable rotor 12 are eccentrically meshed with each other to form 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 a refrigeration cycle. A refrigeration cycle fluid (e.g., refrigerant gas) is introduced into the compression chamber 10 through a suction port (not shown).

[0038] 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, and more preferably 200 MPa to 1800 MPa.

[0039] 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.

[0040] When the shaft seal is a molded product 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, polyvinylidene fluoride resin, liquid crystal polymer, polyethersulfone resin, polysulfone resin, polyphenylsulfone resin, polyarylate resin, polyetherimide resin, polyimide resin, and polyester resin.

[0041] 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.

[0042] The amount of solid lubricant blended is preferably 1 to 40% by volume, and more preferably 1 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 thermoplastic elastomer composition or resin composition may be reduced, and cracks may occur when the shaft seal is assembled into the rotating shaft.

[0043] 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.

[0044] 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 engine power. The shaft seal of the present invention can be used in applications other than compressors.

[0045] 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.

[0046] [Examples 1-2, Comparative Examples 1-2] In Examples 1-2 and Comparative Examples 1-2, the outer lip height was varied to evaluate variations in inner diameter change and other factors. First, the thermoplastic elastomer composition was pelletized using a twin-screw kneading extruder. The resulting pellets were injection molded to produce shaft seals with four different outer lip heights. In Examples 1-2, the seals had the shape shown in Figure 2, with (L1 / L2) ratios of 0.52 and 0.70. In Comparative Example 1, the seals had the shape shown in Figure 8, with (L1 / L2) ratio of 1.09. Table 1 shows the initial (free state) nominal dimensions of each seal.

[0047]

[0048] (1) Measurement of Inner Diameter Change For each of Examples 1 and 2 and Comparative Examples 1 and 2, four shaft seals (four tests) were press-fitted into housings. The inner diameter of each shaft seal in its free state and the inner diameter of the shaft seal after press-fitting into a housing with an inner diameter of 27.5 mm were measured using an image measuring device. The difference between these measurements was used to calculate the inner diameter change due to housing press-fitting (i.e., the amount of contraction of the shaft seal toward the inner diameter). The inner diameter measured here was the distance between the tips 2a of the opposing inner diameter lips (minimum inner diameter). Figure 4(a) shows the relationship between the lip height ratio (L1 / L2) and the inner diameter change. As shown in Figure 4(a), the smaller the lip height ratio (in this case, the smaller the outer diameter lip height), the smaller the variation in the inner diameter change.

[0049] (2) Measurement of rotational torque For each of Examples 1 and 2 and Comparative Examples 1 and 2, four shaft seals were used to measure the rotational torque under the following test conditions: <Test conditions> Oil pressure: 1.0 MPa Oil temperature: 100°C Rotation speed: 7000 rpm Inner diameter interference: 0.7 mm

[0050] Figure 4(b) shows the relationship between the lip height ratio (L1 / L2) and running torque. Because running torque affects the strength of contact between the inner lip of the shaft seal and the outer surface of the rotating shaft, a shaft seal with a large amount of inner diameter change tends to have stronger contact with the rotating shaft, resulting in a large running torque. As the variation in the amount of inner diameter change becomes smaller, the variation in running torque also becomes smaller as (L1 / L2) becomes smaller (see Figure 4(b)).

[0051] [Examples 3 to 12, Comparative Examples 3 to 5] Next, the dimensions of the shaft seals were further investigated. The above pellets were used to produce the shaft seals shown in Table 2 by injection molding. The dimensions in Table 2 are in the free state (before being press-fit into the housing).

[0052]

[0053] (3) Assembly Test The press-fit force was measured as an assembly test into the housing. The press-fit force was measured using a push-pull gauge. The criterion for the press-fit force was set at 300 N or less, as a reference range within which no malfunctions would occur during assembly or operation of the shaft seal. If the press-fit force exceeds 300 N, the shaft seal may deform during assembly, potentially resulting in an increase in leakage due to assembly defects. While no lower limit is specifically set, it is desirable that the shaft seal does not rotate relative to the housing when the rotating shaft rotates. If the shaft seal rotates relative to the housing when the rotating shaft rotates, the outer surface of the shaft seal may wear, potentially leading to a decrease in sealing performance. From a safety perspective, the press-fit force is set to 40 N, preferably 50 N, and even more preferably 60 N. A force of 100 N would provide even greater safety.

[0054] The combinations of verification details for the press-fitting force are as follows: Examples 3, 4, 5, Comparative Example 3: Relationship between L1 / L2 and the press-fitting force Examples 6, 7, 8, 9: Relationship between the outer diameter interference and the press-fitting force Examples 10, 11, 12, Comparative Example 4: Relationship between the lip angle and the press-fitting force

[0055] (3-1) Relationship between L1 / L2 and Press-fit Force As shown in Figure 5(a), the larger the L1 / L2, the smaller the press-fit force. In the present invention, L1 / L2 is set to 0.5 or more and 0.9 or less. If L1 / L2 is less than 0.5, the rigidity of the outer lip increases, causing the press-fit force to exceed, for example, 300 N, which may affect the assembly and sealing performance of the shaft seal. On the other hand, if L1 / L2 is greater than 0.9, as shown in Figure 4(b) above, the variation in rotational torque between shaft seals tends to increase. Furthermore, the rigidity of the outer lip decreases, causing the press-fit force to be smaller than, for example, 100 N.

[0056] (3-2) Relationship between Outer Diameter Interference and Press-fit Force As shown in Figure 5(b), the larger the outer diameter interference (d-D), the larger the press-fit force. If the outer diameter interference (d-D) is greater than 0.7 mm, the rigidity of the outer lip increases, and the press-fit force may exceed 300 N, for example, which may affect the assembly and sealing performance of the shaft seal. On the other hand, if the outer diameter interference (d-D) is less than 0.2 mm, the press-fit force tends to be less than 100 N, for example.

[0057] (3-3) Relationship between Lip Angle and Press-In Force As shown in Figure 5(c), the larger the lip angle of the outer lip, the smaller the press-in force tends to be. In the present invention, the lip angle is set to be greater than 5°. Referring to Figure 5(c), for example, if the lip angle is less than 9°, the contact area with the housing during press-in increases, resulting in a press-in force exceeding 300 N, which may affect the assembly and sealing performance of the shaft seal. On the other hand, if the lip angle is greater than 17°, the rigidity of the outer lip decreases, and the press-in force tends to be less than 100 N, for example.

[0058] (4) Initial Performance Test A rotational torque test was conducted on the shaft seals of Example 3 and Comparative Example 5 under the following conditions using the rotational torque tester shown in Figure 6. The rotational torque was calculated as the average value for one minute after the start of the test. The results are shown in the graph in Figure 7. <Test conditions> Oil pressure: 0.3 MPa, 0.5 MPa, 1.0 MPa Oil temperature: 100°C Rotation speed: 3000 rpm, 7000 rpm Inner diameter interference: 0.4 mm Rotating shaft: Material S45C Refrigerating machine oil: Polyalkylene glycol oil Test time: 1 minute

[0059] 7, for all oil pressures, the rotational torque of Example 3 was lower than the rotational torque of Comparative Example 5. Furthermore, the higher the oil pressure, the greater the reduction in rotational torque.

[0060] (5) Sealing Performance Test: A rotational torque test was conducted under the above conditions using the rotational torque tester shown in Figure 6 to measure the amount of oil leakage. As shown in Figure 6, the housing of the tester 14 is composed of an outer housing 17 and an inner housing 18 assembled together. 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 as the rotating shaft 16 rotates, the inner lip slides against the outer surface of the rotating shaft 16. Refrigeration oil was pumped and supplied into the housing interior. As shown in Figure 6, the refrigeration oil flowed in through the inlet passage 17b, passed through the housing interior, and flowed out through the outlet passage 17c. The oil leakage amount was based on the amount of refrigeration oil leaking from between the rotating shaft 16 and the insertion hole 17a, and represents the amount of leakage within one minute after the start of the test. The results are shown in Table 3.

[0061]

[0062] A small oil leakage rate is desirable because it is believed that this will extend the product life, and it is desirable that the rate not exceed 1.0 ml / min. All examples showed small oil leakage rates and high sealing performance. In particular, Example 3, which had the smallest L1 / L2 ratio (the shortest outer lip diameter), also showed sufficient sealing performance.

[0063] As described above, in the present invention, by optimizing the dimensions of the outer lip of the shaft seal (the ratio of the outer lip height to the inner lip height, the outer interference, the lip angle, etc.), it is possible to realize a shaft seal that ensures low torque performance while suppressing variation in rotational torque.

[0064] The shaft seal of the present invention can reduce the rotational torque of the shaft seal while reducing the variation in the amount of contraction of the outer lip, thereby suppressing the variation in rotational torque, and is therefore widely usable as a shaft seal that seals a sealed fluid while making sliding contact with the outer 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-type refrigerant compressor in an automotive air conditioner.

[0065] REFERENCE SIGNS LIST 1 outer diameter lip 2 inner diameter lip 3 base end portion 4 groove 5 shaft seal 6 rotating shaft 7 housing 8 annular groove 9 compression mechanism portion 10 compression chamber 11 fixed rotor 12 moving rotor 13 discharge port 14 testing machine 15 shaft seal 16 rotating shaft 17 outer peripheral housing 18 inner peripheral housing 19 O-ring

Claims

1. An annular shaft seal provided between a rotating shaft and a housing, the shaft seal comprising an inner lip and an outer lip provided on the outer diameter side of the inner lip, wherein, in a free state, when the height of the outer lip is L1 and the height of the inner lip is L2, 0.5≦(L1 / L2)≦0.9, and the inclination angle of the outer lip with respect to the axial direction is greater than 5°.

2. A shaft seal as described in claim 1, characterized in that, when the outer diameter of the shaft seal in a free state is d and the inner diameter of the housing is D, the interference (d-D) between the shaft seal and the housing is 0.2 mm to 0.7 mm.

3. The shaft seal according to claim 1, wherein the inclination angle is between 9° and 17°.

4. The shaft seal according to claim 1, characterized in that 0.5≦(L1 / L2)≦0.7 is satisfied in said shaft seal.

5. A shaft seal as described in claim 1, characterized in that, when the outer diameter of the shaft seal in a free state is d and the inner diameter of the housing is D, the interference (d-D) between the shaft seal and the housing is 0.2 mm to 0.7 mm, the inclination angle is 9° to 17°, and 0.5≦(L1 / L2)≦0.7 for the shaft seal.

6. A shaft seal according to claim 1, wherein the lip thickness of the outer lip is thinner than the lip thickness of the inner lip.

7. The shaft seal according to claim 1, characterized in that the shaft seal is used for a rotating shaft in a scroll compressor for an in-vehicle air conditioner.

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