Shaft seal

Abstract

Provided is 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, thereby suppressing the variation in rotational torque. [Solution] The shaft seal 5 is an annular shaft seal provided between a rotating shaft 6 and a housing 7, and comprises an inner lip 2 and an outer lip 1 provided on the outer diameter side of the inner lip 2, and in the shaft seal 5 in a free state, when the height of the outer lip 1 is L1 and the height of the inner lip 2 is L2, 0.5≦(L1 / L2)≦0.9 and the inclination angle of the outer lip 1 with respect to the axial direction is greater than 5°.

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 compressor for a car air conditioner. [Background technology]

[0002] As the electrification of automobiles progresses, the demand for electric compressors, including car air conditioners, is increasing year by year. One way to save energy in automobiles is to reduce the power loss of electric compressors. In order 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, it is easier to control the torque loss when the shaft seal is incorporated into the unit by suppressing the torque variation.

[0003] For example, Patent Document 1 discloses a shaft seal used in a scroll compressor of a car air conditioner. This shaft seal is inserted into a mounting groove of the shaft to seal the refrigerant oil between the shaft and the housing. The shaft seal expands in diameter when it receives 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 peripheral surface of the housing and the outer peripheral surface of the shaft, respectively.

[0004] The shaft seal of Patent Document 1 is disclosed as being substantially U-shaped in axial cross section, having 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 having an inclination angle of 5° to 20° with respect to the outer circumferential surface of the rotating shaft, and the inner lip having a length of 2.0 mm to 6.5 mm in axial cross section of the shaft seal. 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. [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] Incidentally, shaft seals are usually installed with an interference between the outer lip and the inner peripheral surface of the housing. When installed with an interference, the shaft seal shrinks in the inner radial direction. The amount of shrinkage of the shaft seal in the inner radial direction affects the pressing force of the inner lip against the outer peripheral surface of the shaft. The outer lip of the shaft seal is fixed to the inner peripheral surface of the housing and slides against the outer peripheral surface of the shaft, so the pressing force of the inner lip against the outer peripheral surface of the shaft affects the rotational torque. In other words, it is considered that the rotational torque can be stabilized by reducing the variation in the amount of shrinkage of the shaft seal in the inner radial direction due to the interference of the outer lip. Patent Document 1 considers the length of the inner lip, but does not consider the outer lip at all.

[0007] The present invention has been made in consideration of the above 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 variation in rotational torque. [Means for solving the problem]

[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 on the outer diameter side of the inner lip, the shaft seal being characterized in that, 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 against the outer peripheral surface of the rotating shaft while being in close contact with it, and the outer lip is fitted into the housing with an interference.

[0009] In the present invention, the "free state" refers to a state in which no external force is acting on the shaft seal, for example, 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 with respect to the axial direction refers to the angle between the outer peripheral surface of the outer lip and the axial direction.

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

[0011] The inclination angle is characterized by being 9° to 17°.

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

[0013] When the outer diameter dimension of the shaft seal in a free state is d and the inner diameter dimension of the housing is D, the interference (dD) 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, a lip thickness of the outer lip is thinner than a lip thickness of the inner lip.

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

[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 with respect to the axial direction is greater than 5°. Therefore, while ensuring low torque performance, the variation in the amount of inner diameter contraction when installed in a housing is reduced 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 (dD) between the shaft seal and the housing is 0.2 mm to 0.7 mm, making it easy to keep the press-fit force against the housing appropriate, which results in 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 than in the conventional configuration; however, by making the lip thickness of the outer diameter lip thinner than the lip thickness of the inner diameter lip in the shaft seal, for example, it is possible to prevent the press-fit force from becoming excessive, which results in ensuring sealing performance. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing an example of a shaft seal of the present invention mounted on a rotating shaft. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the shaft seal of FIG. 1 in a free state. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a compression mechanism of a scroll compressor. [Figure 4] 1 is a graph showing the relationship between L1 / L2 and the amount of change in inner diameter. [Diagram 5] 1 is a graph showing the relationship between L1 / L2 and press-in force, etc. [Figure 6] FIG. 1 is a schematic diagram of a measurement test of rotational torque. [Figure 7] 13 is a graph showing test results of rotational torque. [Figure 8] FIG. 1 is a diagram showing a configuration of a conventional shaft seal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0021] A compressor to which the shaft seal of the present invention is applied 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 substantially J-shaped cross-sectional view in the axial direction, and has an inner lip 2 on the inner diameter side of the seal extending to one side in the axial direction, and an outer lip 1 provided on the outer diameter side of the seal than 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 length of the inner lip 2 is longer than the length of 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 is provided with an insertion hole 7a through which the rotating shaft 6 is inserted, and an annular groove 8 is provided around the insertion hole 7a. The shaft seal 5 is fitted into this annular groove 8 with an interference, and the inner lip 2 slides on the rotating shaft 6 as the rotating shaft 6 rotates around the axis O.

[0022] In FIG. 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 to 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. In the installed state, 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 not to rotate, and the vicinity of the tip of the inner lip 2 contacts the outer peripheral surface of the rotating shaft 6 so as not to rotate. 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, a space is 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 the variation in rotational torque while ensuring low torque characteristics by optimizing the ratio (L1 / L2) of the height L1 of the outer diameter lip 1 in the free state to the height L2 of the inner diameter lip 2 in the free state. As shown in FIG. 2, the height L1 of the outer diameter lip 1 in the free state is the distance in the height direction (axial direction X) between the back surface 3a of the base end portion 3 and the tip end portion 1a of the outer diameter lip 1. Further, the height L2 of the inner diameter lip 2 in the free state is the distance in the height direction (axial direction X) between the back surface 3a of the base end portion 3 and the tip end portion 2a of the inner diameter lip 2.

[0024] Details of the shaft seal 5 will be described with reference to FIG. 2. FIG. 2 shows an enlarged cross-sectional view of the shaft seal in a state before being mounted on the housing (free state). In the shaft seal 5, the outer diameter lip and the inner diameter lip are formed to be inclined in a direction in which the tip end portions 1a and 2a are separated from each other. In FIG. 2, the inner peripheral surface of the shaft seal 5 is formed so as to continuously reduce in diameter from the back surface 3a to the tip end portion 2a, and the outer peripheral surface of the shaft seal 5 is formed so as to continuously increase in diameter from the back surface 3a to the tip end portion 1a.

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

[0026] In the 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) in order 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 made 0.9 or less), which can reduce the variation in the inner diameter change of the shaft seal after the housing is pressed into it, as will be shown in the examples described later, and as a result, the variation in the rotational torque can be reduced. In other words, by making the height L1 of the outer lip 1 relatively small, the reproducibility of the state of the shaft seal after the housing is pressed into it is excellent, and the variation between the inner diameter dimensions of the shaft seal can be reduced. On the other hand, if L1 / L2 becomes too small, that is, if the height L1 of the outer lip 1 becomes too small relatively, the shaft seal may deform during assembly, and the amount of leakage may increase due to poor assembly. Therefore, L1 / L2 is set to 0.5 or more.

[0027] In the present invention, from the viewpoint of stabilizing the rotational torque, it is preferable that L1 / L2 is smaller. 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 in the above-mentioned range, the press-fitting force (rigidity of the lip) tends to be larger than that of the conventional configuration. Therefore, it is preferable to set the thickness of the outer lip, which affects the rigidity of the lip. Specifically, in the shaft seal 5, in order to prevent the rigidity of the outer lip from becoming too high, that is, to prevent the press-fitting force from becoming too large, it is preferable to make the lip thickness t1 of the outer lip 1 thinner than the lip thickness t2 of the inner lip 2. Furthermore, it is preferable to make the lip thickness t1 of the outer lip 1 thinner than the thickness t3 of the base end 3. The lip thickness 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 with respect to the axial direction is greater than 5°. By making the inclination angle θ greater than 5°, it is possible to ensure sealing performance as shown in the sealing performance test described later. 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, and 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 Fig. 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 Fig. 1, the shaft seal 5 has an inner lip 2 that is in close contact with the outer circumferential surface of the rotating shaft 6 and an outer lip 1 that is in close contact with the side wall of the annular groove 8, thereby preventing the fluid on the high pressure side from leaking to the low pressure side. 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 into the housing 7 with an interference. That is, the outer diameter d of the shaft seal 5 in a free state needs to be larger than the inner diameter D of the housing 7 (see FIG. 2).

[0034] The interference (dD) 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. By setting the interference (dD) in the above range, it becomes easier to make the press-fitting force appropriate, and therefore it becomes easier to ensure sealing performance.

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

[0036] In the compressor of Fig. 1, a compression mechanism is provided on the high pressure side of the housing 7. The compression mechanism may be of any type as long as it compresses the fluid by the rotation of the rotating shaft 6, and may be of a scroll type, a swash plate type, or the like. 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 the 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 engaged with each other to form a compression chamber 10 therebetween. The movable rotor 12 is directly or indirectly connected to the above-mentioned rotating shaft, and the compression chamber 10 moves toward the center of the spiral shape as the movable rotor 12 revolves around the axis of the fixed rotor 11, thereby 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 out into the refrigeration cycle. Then, the fluid of the refrigeration cycle (such as a 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, more preferably 200 MPa to 1800 MPa.

[0039] In the thermoplastic elastomer composition, the elastomer as the main component is not limited, and polyolefin-based elastomers, polyester-based elastomers, polyamide-based elastomers, etc. can be used. In terms of heat resistance and chemical resistance, polyester-based elastomers are particularly preferred. The polyester-based elastomers contain hard segments and soft segments, with polyester units being used in the hard segments and polyether units or polyester units being used in the soft segments. The polyester-based elastomers are polyester-polyether type or polyester-polyester type multiblock copolymers.

[0040] 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, polyvinylidene fluoride resin, liquid crystal polymer, polyethersulfone resin, polysulfone resin, polyphenylsulfone resin, polyarylate resin, polyetherimide resin, polyimide resin, polyester resin, and the like.

[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 the solid lubricant is preferably 1 to 40% by volume, 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 decrease, and cracks may occur when the shaft seal is assembled into the rotating shaft.

[0043] In addition, to the extent that the effect of the present invention is not impaired, 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. Colorants such as carbon black and iron oxide may also be blended. These may be blended 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 in-vehicle air conditioner. The scroll compressor may be either belt-driven using engine power or motor-driven without engine power. The shaft seal of the present invention can be used for more than just 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 are mixed, as necessary, in a Henschel mixer, a ball mixer, a 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 adopting a side feed when melt-kneading in a twin-screw extruder or the like. The molding pellets are then molded by injection molding into a shaft seal. EXAMPLES

[0046] [Examples 1-2, Comparative Examples 1-2] In Examples 1-2 and Comparative Examples 1-2, the outer lip height was changed to evaluate the variation in the inner diameter change amount, etc. First, the thermoplastic elastomer composition was pelletized by a twin-screw kneading extruder. The obtained pellets were used to manufacture shaft seals with four levels of outer lip height by injection molding. In Examples 1-2, the shape was as shown in FIG. 2, and (L1 / L2) was 0.52 and 0.70. In Comparative Example 1, (L1 / L2) was 0.91. In Comparative Example 2, the shape was as shown in FIG. 8, and (L1 / L2) was 1.09. Table 1 shows the initial (free state) nominal dimensions of each shaft seal.

[0047] [Table 1]

[0048] (1) Measurement of the change in inner diameter For each of Examples 1-2 and Comparative Examples 1-2, four shaft seals were used for each (four tests). The inner diameter of the shaft seal in the 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 by an image measuring device, and the inner diameter change amount (= the amount of contraction of the shaft seal in the inner diameter direction) due to the housing press-fitting was calculated from the difference. As the inner diameter dimension here, the distance between the tip portions 2a of the opposing inner diameter lips (the minimum inner diameter dimension) was measured. Figure 4(a) shows the relationship between the lip height ratio (L1 / L2) and the inner diameter change amount. As shown in Figure 4(a), there was a tendency that 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 amount.

[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> Hydraulic pressure: 1.0MPa Oil temperature: 100℃ Rotational speed: 7000 rpm Inner diameter tightening margin: 0.7 mm

[0050] Figure 4(b) shows the relationship between the lip height ratio (L1 / L2) and the running torque. Since the running torque is affected by the strength of contact between the inner lip of the shaft seal and the outer circumferential surface of the rotating shaft, a shaft seal with a large amount of inner diameter change will have stronger contact with the rotating shaft, and the running torque will tend to be large. Due to the smaller variation in the amount of inner diameter change, the smaller (L1 / L2) becomes, the smaller the variation in the running torque becomes (see Figure 4(b)).

[0051] [Examples 3 to 12, Comparative Examples 3 to 5] Next, the dimensions of the shaft seal were further examined. 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 pressed into the housing).

[0052] [Table 2]

[0053] (3) Embedded testing The press-in force was measured as an assembly test into the housing. The press-in force was measured using a push-pull gauge. The criterion for the press-in force was set to 300N or less as a reference range in which no malfunction occurs during assembly and operation of the shaft seal. If the force exceeds 300N, the shaft seal may deform during assembly, and the amount of leakage may increase due to poor assembly. There is no particular lower limit, but 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 circumferential surface of the shaft seal may wear out, leading to a decrease in sealing performance. In consideration of safety, the force is 40N, preferably 50N, and more preferably 60N, and 100N will increase safety even further.

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

[0055] (3-1) Relationship between L1 / L2 and press-in force As shown in FIG. 5(a), the larger L1 / L2 is, the smaller the press-in force tends to be. In the present invention, L1 / L2 is set to 0.5 or more and 0.9 or less. Here, if L1 / L2 is smaller than 0.5, the rigidity of the outer lip increases, so the press-in force exceeds, for example, 300 N, which may affect the assembly and sealing properties of the shaft seal. On the other hand, if L1 / L2 is larger than 0.9, as shown in FIG. 4(b) above, there is a tendency for the variation in rotational torque between shaft seals to increase. In addition, the rigidity of the outer lip decreases, so the press-in force becomes 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 outside diameter interference (dD), the larger the press-in force tends to be. If the outside diameter interference (dD) is greater than 0.7 mm, the rigidity of the outside lip increases, and the press-in 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 outside diameter interference (dD) is less than 0.2 mm, the press-in force tends to be less than 100 N, for example.

[0057] (3-3) Relationship between lip angle and press-in force As shown in Fig. 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°. In Fig. 5(c), for example, if the lip angle is smaller than 9°, the contact area with the housing during press-in becomes large, and the press-in force exceeds, for example, 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, for example, 100 N.

[0058] (4) Initial performance test A rotational torque test was carried out on the shaft seals of Example 3 and Comparative Example 5 under the following conditions using a rotational torque tester shown in Fig. 6. The rotational torque was calculated as an average value for one minute after the start of the test. The results are shown in the graph of Fig. 7. <Test conditions> Hydraulic pressure: 0.3MPa, 0.5MPa, 1.0MPa Oil temperature: 100℃ Rotation speed: 3000 rpm, 7000 rpm Inner diameter tightening margin: 0.4 mm Rotating shaft: Material: S45C Refrigeration oil: Polyalkylene glycol oil Test time: 1 minute

[0059] 7, in all cases of oil pressure, 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 the rotational torque.

[0060] (5) Sealing performance test A rotation torque test was performed under the above conditions using a rotation torque tester shown in FIG. 6 to measure the amount of oil leakage. As shown in FIG. 6, the housing of the tester 14 is formed by assembling an outer housing 17 and an inner housing 18. At the mating surface of these housings, an O-ring 19 is arranged in the outer circumferential 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 the inner lip slides against the outer circumferential surface of the rotating shaft 16 due to the rotation of the rotating shaft 16. The refrigeration oil was pumped and supplied to the space inside the housing. As shown in FIG. 6, the refrigeration oil flows in from the inlet passage 17b, passes through the space inside the housing, and flows out from the outlet passage 17c. The amount of oil leakage is based on the amount of refrigeration oil leaking from between the rotating shaft 16 and the insertion hole 17a, and indicates the amount of leakage for one minute after the start of the test. The results are shown in Table 3.

[0061] [Table 3]

[0062] It is desirable to have a small amount of oil leakage because it is believed that this will lead to a longer product life, and it is preferable that the amount does not exceed 1.0 ml / min. In all of the examples, the amount of oil leakage was small and high sealing performance was demonstrated. In particular, even Example 3, which had the smallest L1 / L2 (shortest outer lip), 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 suppresses variation in rotational torque while ensuring low torque performance. [Industrial Applicability]

[0064] The shaft seal of the present invention can reduce the variation in the amount of contraction of the outer lip while reducing the rotational torque of the shaft seal, thereby suppressing the variation in rotational torque, and can therefore be widely used as a shaft seal that seals a sealed fluid while making sliding contact with the outer circumferential surface of a rotating shaft. It is particularly suitable as a shaft seal for a rotating shaft that rotates a compression mechanism of a scroll-type refrigerant compressor in an in-vehicle air conditioner. [Explanation of symbols]

[0065] 1 Outer Lip 2 Inner Lip 3 Base end 4 Groove 5 Shaft seal 6 Rotation Axis 7. Housing 8 Annular groove 9. Compression mechanism 10 Compression chamber 11 Fixed rotor 12 Movable 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 provided between a rotating shaft and a housing, The shaft seal includes an inner lip and an outer lip provided on an outer diameter side of the inner lip, 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°.

2. The shaft seal according to claim 1, characterized in that, when the outer diameter dimension of the shaft seal in a free state is d and the inner diameter dimension 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 or 2, characterized in that the inclination angle is 9° to 17°.

4. 3. The shaft seal according to claim 1, wherein the relationship 0.5≦(L1 / L2)≦0.7 is satisfied in the shaft seal.

5. The shaft seal according to claim 1, characterized in that, when the outer diameter dimension of the shaft seal in a free state is d and the inner diameter dimension 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 in the shaft seal.

6. 3. The 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. 3. The shaft seal according to claim 1, wherein the shaft seal is used for a rotating shaft of a scroll compressor for an in-vehicle air conditioner.

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