Oil seal structure and manufacturing method thereof

Abstract

To provide an oil seal structure which can inhibit increase of a space needed for a boundary part between different kinds of oils enclosed in two storage parts communicating with each other at interiors while inhibiting mixing of the oils, and to provide a manufacturing method of the oil seal structure.SOLUTION: An oil seal structure S inhibits mixing of a first lubrication oil 7 and a second lubrication oil 20 in a boundary portion where a first housing part 6 and a second housing part 21 are fastened on a rotary shaft 4. The oil seal structure S includes: an oil seal 30 provided at the boundary portion; an insertion part 32 provided adjacent to the oil seal 30 and having a cylindrical insertion part 32c which extends into the first housing part 6 and into which the rotary shaft 4 is inserted while forming a predetermined clearance 34 in a radial direction of the rotary shaft 4, and fastening parts 32a, 32b fastened to the second housing part 21 at the boundary portion; and a trap mechanism 31 which is provided between the fastening parts 32a, 32b and the oil seal 30 in an axial direction and communicates with the predetermined clearance 34.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oil seal structure for preventing different types of oil from being mixed together, and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a throttle valve device for an internal combustion engine in which a metal member reinforcing the resin-molded portion of the throttle shaft is divided into a shaft portion and a pipe portion attached to the outer periphery of the shaft portion to prevent welds from forming in the resin-molded portion of the throttle shaft. In the device disclosed in Patent Document 1, the shaft portion and the pipe portion are set in a resin molding die used to manufacture the throttle shaft, and molten resin is poured through a gate into a cylindrical gap formed between the outer periphery of the shaft portion and the inner periphery of the pipe portion. This gap functions as a film gate, thereby preventing welds from forming. The device also includes an oil seal attached to the outer periphery of the throttle shaft to prevent oil from entering the throttle valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-251232 Summary of the Invention [Problem to be solved by the invention]

[0004] Oil seals have a pumping force (pump effect) that draws oil from the opposite side (outside) to the side (inside) where the oil is sealed. Therefore, at the boundary between two housing sections containing different types of oil, an oil seal is provided for each oil, and a predetermined gap where neither type of oil is present is sometimes left between the oil seals. This increases the amount of space required for the two oil seals and the predetermined gap, potentially resulting in inconveniences such as reduced space for arranging other components.

[0005] The present invention has been made with an eye on the above-mentioned technical problems, and aims to provide an oil seal structure and a manufacturing method thereof that can suppress the mixing of different types of oil sealed in two storage sections whose interiors are connected, while suppressing an increase in the space required at the boundary between the oils. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides an oil seal structure comprising a first storage section for storing a first lubricating oil, a second storage section fastened adjacent to the first storage section and for storing a second lubricating oil, and a rotating shaft passing through the fastened portions of the first storage section and the second storage section, the oil seal structure preventing the first lubricating oil and the second lubricating oil from mixing at the boundary portion on the rotating shaft where the first storage section and the second storage section are fastened, the oil seal provided at the boundary portion on the rotating shaft, and an insertion member provided adjacent to the oil seal and into which the rotating shaft is inserted, the insertion member having a cylindrical insertion portion extending into the first storage section and into which the rotating shaft is inserted with a predetermined gap in the radial direction of the rotating shaft, and a fastening portion adjacent to the oil seal and fastened to the second storage section at the boundary portion, the oil seal structure further comprising a trap mechanism provided between the fastening portion and the oil seal in the axial direction of the rotating shaft and communicating with the predetermined gap.

[0007] The insertion member may further have a tapered portion provided at an end of the insertion portion opposite the fastening portion in the axial direction, the tapered portion opening the insertion portion widely.

[0008] The tip of the tapered portion may be higher than the oil surface height of the accumulated first lubricating oil.

[0009] In addition, the insertion member may further have a secondary processing portion formed in a predetermined range on the end side opposite the fastening portion of the insertion portion, and having a smaller inner diameter dimensional error than other areas of the insertion portion.

[0010] The manufacturing method of the present invention is a manufacturing method of an oil seal structure that prevents the first lubricating oil and the second lubricating oil from mixing at a boundary portion on the rotating shaft where the first and second storage portions are fastened, the manufacturing method comprising: a first storage portion that stores a first lubricating oil; a second storage portion that is fastened adjacent to the first storage portion and stores a second lubricating oil; a rotating shaft that passes through the fastened portion of the first storage portion and the second storage portion; and an oil seal provided at the boundary portion on the rotating shaft; and an insertion member that is provided adjacent to the oil seal and into which the rotating shaft is inserted, the insertion member being a member that passes through the first storage portion and the second storage portion. The rotating shaft is inserted into the rotating shaft with a predetermined gap in the radial direction of the rotating shaft, and a fastening portion is adjacent to the oil seal and fastened to the second accommodating portion at the boundary portion. The rotating shaft is further provided with a trap mechanism that is provided between the fastening portion and the oil seal in the axial direction of the rotating shaft and communicates with the predetermined gap. After assembling the first accommodating portion, the second accommodating portion, the oil seal, and the inserting member, the rotating shaft is inserted along the lower side of the inner surface of the inserting portion from the opposite side to the fastening portion, and assembled into the second accommodating portion.

[0011] After the inserting member is formed by press working, it may be subjected to cutting or polishing processing in a predetermined range on the end side of the inserting portion of the inserting member opposite the fastening portion, so that the dimensional error of the inner diameter is smaller than that of other ranges in the inserting portion. [Effects of the Invention]

[0012] This oil seal structure features two interconnected housings, each containing a different type of lubricating oil. An insertion member is provided at the boundary between the two housings, allowing insertion of a rotating shaft that passes through the boundary. The insertion member has an insertion portion through which the rotating shaft passes with a predetermined gap and a fastening portion attached to the boundary. A trap mechanism is provided between the fastening portion and the oil seal provided at the boundary, communicating with the predetermined gap. Therefore, even if lubricating oil enters the predetermined gap between the insertion portion and the rotating shaft, the trap mechanism can prevent or suppress the lubricating oil from reaching the oil seal. This means that a single oil seal can be installed on a rotating shaft that passes through two housings containing different oils, and the space required to accommodate the pumping force between the oil seals can be reduced, which would be required if two oil seals were installed. This reduces costs and the axial space required.

[0013] The insertion member is provided with a tapered portion at the end opposite the fastening portion of the insertion portion that widens the insertion portion, and the tapered portion is higher in the axial direction than the oil level of the lubricating oil, thereby preventing the lubricating oil from penetrating into the insertion portion.

[0014] According to this manufacturing method of the oil seal structure, the rotating shaft is assembled after assembling the first housing portion, the second housing portion, the oil seal, and the insertion member. At this time, the rotating shaft is inserted into the insertion portion along the lower side of the inner circumferential surface of the insertion portion, making it easy to insert the rotating shaft all the way into the second housing portion. Furthermore, a predetermined area on the end side of the insertion portion opposite the fastening portion is subjected to a removal process to reduce the dimensional error of the inner diameter compared to other areas of the insertion portion. Therefore, when the rotating shaft is inserted along the insertion portion, it is possible to prevent the rotating shaft from losing its position. This prevents or suppresses situations such as damage caused by the tip of the rotating shaft coming into contact with other parts, such as the oil seal, during insertion, which could reduce durability. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an example of a transaxle to which an oil seal structure according to an embodiment of the present invention is applied; [Figure 2] 2 is a diagram showing a state in which the drive shaft in FIG. 1 is being inserted into a guide portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention, and are not intended to limit the present invention.

[0017] FIG. 1 shows a transaxle 1 to which an oil seal structure S according to an embodiment of the present invention is applied. In the transaxle 1 shown in FIG. 1, a transmission 2 and a differential gear unit 3 are arranged side by side in the vehicle width direction. A pair of drive shafts 4, 5 extending in the vehicle width direction are connected to the differential gear unit 3. Wheels (not shown) are connected to the ends of the pair of drive shafts 4, 5 opposite the differential gear unit 3, and output torque from a driving power source (not shown) such as an engine or a motor is transmitted to the wheels via the transmission 2 and the differential gear unit 3. FIG. 1 shows an oil seal structure applied between the drive shaft 4, which extends to the right of the vehicle, the differential gear unit 3, and the transmission 2. Note that, below, when describing only the drive shaft 4 on the right side of the vehicle, it may be referred to simply as the drive shaft 4. In the following description, the left-right direction in FIG. 1 will be referred to as the left-right direction of the vehicle, and the up-down direction in FIG. 1 will be referred to as the up-down direction of the vehicle.

[0018] The transmission 2 is composed of gears, clutches, and the like, neither of which are shown. The gears and clutches are housed in a transmission case 6, which corresponds to a first housing in this embodiment of the present invention, and increase or decrease torque output from a driving power source (not shown), such as an engine or a motor, and transmit the torque to the differential gear unit 3. The gears and clutches are cooled and lubricated by a fluid 7 housed in the transmission case 6. The fluid 7 corresponds to a first lubricating oil in this embodiment of the present invention, and as shown by the dotted line in FIG. 1 , the fluid is stored in the transmission case 6 and is supplied to the gears and clutches by, for example, a scoop or an oil pump (not shown). The fluid 7 not only provides lubrication and cooling, but also functions to transmit power, suppress wear of a wet clutch, and act as a control hydraulic pressure to operate various components, and contains various mixtures to meet these functional performance requirements.

[0019] The differential gear unit 3 is configured in the same manner as a conventionally known multi-plate clutch type limited slip differential (LSD). The differential gear unit 3 mainly comprises a pair of differential side gears 10, 11 positioned coaxially facing each other, four differential pinion gears 12, 13 (only two of which are shown in FIG. 1 ) meshing with the pair of differential side gears 10, 11, a cross-shaped differential pinion shaft 14 having the differential pinion gears 12, 13 connected to each end thereof for relative rotation, a pair of pressure rings 15, 16 provided on the outer periphery of the differential pinion gears 12, 13 and operating in the axial direction in response to torque input to the differential pinion gears 12, 13, and a pressure ring 16 disposed outside the differential pinion gears 12, 13. The differential gear unit includes a differential case 19 that houses the differential side gears 10, 11, differential pinion gears 12, 13, differential pinion shaft 14, pressure rings 15, 16, and clutch mechanisms 17, 18, and a housing 21 that receives torque transmitted from the transmission 2 and houses differential oil 20 that cools and lubricates the gears and clutches that make up the differential case 19 and the differential gear unit, and is fastened to the transmission case 6. The differential oil 20 corresponds to the second lubricating oil in this embodiment of the present invention, and the housing 21 corresponds to the second housing portion in this embodiment of the present invention.

[0020] The differential gear unit 3 configured in this manner absorbs the difference in rotation speed between the left and right wheels and limits differential movement using the clutch mechanisms 17, 18 if one of the wheels spins or slips. Specifically, the differential gear unit 3 is a so-called torque-sensitive LSD, where the force with which the differential pinion gears 12, 13 press against the pressure rings 15, 16 increases as the input to the differential gear unit 3 increases. This increases the force with which the clutch mechanisms 17, 18 are pressed together, thereby limiting differential movement between the drive shafts 4, 5. Furthermore, as shown by the dashed-dotted line in FIG. 1 , differential oil 20 resides within the housing 21. The differential oil 20 cools and lubricates the components that make up the differential gear unit 3 and has different properties from the fluid 7 contained within the transmission case 6. In the following, when describing only the differential side gear 10 on the right side of the vehicle out of the pair of differential side gears 10, 11, it may be simply referred to as the differential side gear 10, and similarly, when describing only the clutch mechanism 17 on the right side of the vehicle out of the pair of clutch mechanisms 17, 18, it may be simply referred to as the clutch mechanism 17.

[0021] The drive shaft 4 on the right side of the vehicle shown in Fig. 1 is supported by passing through the transmission case 6, and is formed so that its outer diameter tapers in stages from one end on the wheel side to the other end on the differential gear unit 3 side. That is, the drive shaft has, in order from the part with the smallest diameter on the other end side, a first shaft portion 4a, a second shaft portion 4b, a third shaft portion 4c, and a fourth shaft portion 4d.

[0022] One end of the drive shaft 4 opposite the differential gear unit 3, i.e., the fourth shaft portion 4d, is held relatively rotatably by a wall portion of the transmission case 6 via a bearing 22. A first oil seal 23 is provided at one end of the drive shaft 4, closer to the interior of the transmission case 6 than the bearing 22. The first oil seal 23 is disposed between the transmission case 6 and the drive shaft 4, and prevents or suppresses leakage of the fluid 7 sealed inside the transmission case 6 to the outside.

[0023] A hollow section 4e is formed at one end of the drive shaft 4, and this hollow section 4e extends in the axial direction of the drive shaft 4 and opens toward the one end. The hollow section 4e gradually narrows toward the other end of the drive shaft 4, which is on the differential gear unit 3 side. That is, an inner drive shaft 24 is inserted into the hollow section 4e and connected, for example, by a spline, so that the inner drive shaft 24 can rotate integrally with the drive shaft 4. The end of the inner drive shaft 24 opposite the drive shaft 4 is connected to the rear wheel (not shown) on the right side of the vehicle.

[0024] The other end of the drive shaft 4 passes through the portion where the housing 21 and the transmission case 6 are fastened together, and is connected to the differential side gear 10 of the differential gear unit 3. Specifically, spline teeth 25 are formed on the outer peripheral surface of the first shaft portion 4a of the drive shaft 4, and by engaging with spline teeth 26 formed on the inner peripheral surface of the differential side gear 10, the drive shaft 4 and the differential side gear 10 are connected to rotate integrally. In other words, the torque of the differential gear unit 3 is transmitted to the drive shaft 4 by this spline engagement.

[0025] Additionally, a cylindrical portion 27 extending into the transmission case 6 is formed in the housing 21 of the differential gear unit 3. A fastening portion 28 of the transmission case 6 is disposed to cover the outer peripheral surface of the cylindrical portion 27, and by joining these together, the housing 21 and the transmission case 6 are fastened together. A second oil seal 30, a trap mechanism 31, and a guide mechanism 32 are provided at the boundary between the housing 21 and the transmission case 6, where the drive shaft 4 passes through.

[0026] As shown in FIGS. 1 and 2, the second oil seal 30 is interposed between the housing 21 and the drive shaft 4. Specifically, the second oil seal 30 is attached to the inner circumferential surface of a small-diameter portion 33 of the cylindrical portion 27 of the housing 21 that protrudes axially toward the guide mechanism 32. The second oil seal 30 is provided to slide against the third shaft portion 4c of the drive shaft 4 and mainly prevents or inhibits the differential oil 20 in the housing 21 from infiltrating to the outside, i.e., into the transmission case 6. Specifically, as shown in FIG. 2, the second oil seal 30 is provided so that its seal lip 30a is located inside the housing 21 in the axial direction of the drive shaft 4 and its dust lip 30b is located on the transmission 2 side. The second oil seal 30 corresponds to the oil seal in this embodiment of the present invention.

[0027] The trap mechanism 31 captures oil that has entered the guide mechanism 32. The trap mechanism 31 is provided outside the second oil seal 30 in the axial direction, i.e., on the transmission 2 side. The trap mechanism 31 is a gap between the second oil seal 30 and the guide mechanism 32 in the axial direction, and is formed in the shape of a ring that is long in the radial direction of the drive shaft 4. Specifically, as shown in FIG. 1 , the radial length of the trap mechanism 31 is approximately the length from the outer peripheral surface of the drive shaft 4 to the surface of the small diameter portion 33 facing the axial direction. The trap mechanism 31 forms a space surrounded by the second oil seal 30, the small diameter portion 33, and the guide mechanism 32.

[0028] Guide mechanism 32 corresponds to the insertion member in the embodiment of the present invention and is a member for guiding drive shaft 4 when it is attached to differential side gear 10. Guide mechanism 32 forms a gap serving as trap mechanism 31 between small diameter portion 33 and second oil seal 30. Guide mechanism 32 has large diameter portion 32a attached to the outer surface of housing 21, disk portion 32b extending radially inward from large diameter portion 32a, and cylindrical guide portion 32c extending axially from disk portion 32b to allow drive shaft 4 to pass therethrough. Large diameter portion 32a is attached so as to fit onto the outer peripheral surface of small diameter portion 33 of housing 21. Specifically, large diameter portion 32a is fastened to the axial surface of cylindrical portion 27 of housing 21 and the radially outward surface of small diameter portion 33. The disk portion 32b, continuing from the large diameter portion 32a, forms a surface facing the axial direction that, together with the second oil seal 30 and the small diameter portion 33, forms the trap mechanism 31. The disk portion 32b extends radially inward from the large diameter portion 32a, and the portion extending axially from the inner end of the disk portion 32b, which is its tip, forms the guide portion 32c. The large diameter portion 32a and the disk portion 32b correspond to the fastening portion in this embodiment of the invention, and the guide portion 32c corresponds to the insertion portion in this embodiment of the invention.

[0029] The guide portion 32c is cylindrical and extends to near the center of the transmission case 6 in the vehicle width direction. As will be described in detail later, the length of the guide portion 32c is set to prevent damage to the second oil seal 30 caused by the drive shaft 4 when the drive shaft 4 is inserted into the guide portion 32c and enters the housing 21. As shown in FIG. 2, the guide portion 32c is formed to create a small, predetermined gap 34 between the guide portion 32c and the drive shaft 4 so that the inner circumferential surface of the guide portion 32c and the outer circumferential surface of the drive shaft 4 do not slide against each other. A tapered portion 32d is formed at the end (tip) of the guide portion 32c opposite the large diameter portion 32a so that the opening widens in the axial direction.

[0030] The tapered portion 32d is formed to assist the leading end of the drive shaft 4 in being inserted into the guide portion 32c when the drive shaft 4 is inserted. As described above, the guide portion 32c extends to near the center of the transmission case 6 in the vehicle width direction, and the tapered portion 32d is formed at the leading end. As shown in FIG. 1, the leading end of the tapered portion 32d is located lower than the cylindrical portion 27 in the vehicle height direction, but is located higher than the liquid level (oil level in a stationary state) of the fluid 7 accumulated in the lower part of the transmission case 6. Furthermore, even if the liquid level of the accumulated fluid 7 changes due to a change in acceleration in the vehicle width direction that occurs when the vehicle is turning, for example, the leading end of the tapered portion 32d is located higher than the changed liquid level, i.e., the dynamic oil level.

[0031] The guide mechanism 32 also has a secondary processed portion 32e in a predetermined range from the end of the guide portion 32c on the tapered portion 32d side. The secondary processed portion 32e has an inner diameter with a smaller dimensional error than the other range of the guide portion 32c. The secondary processed portion 32e is provided to improve the assemblability of the drive shaft 4 while forming a predetermined gap 34 between the drive shaft 4 and the guide portion 32c. Specifically, the secondary processed portion 32e is designed to suppress contact between the tip of the other end of the drive shaft 4, particularly the spline teeth 25, and the second oil seal 30 when the drive shaft 4 is inserted through the guide portion 32c, while ensuring that the predetermined gap 34 is formed between the drive shaft 4 and the guide portion 32c when the drive shaft 4 is engaged with the differential side gear 10. The secondary processed portion 32e is a portion that is subjected to removal processing such as cutting and polishing after the guide mechanism 32 is formed by pressing or the like. That is, the secondary processed portion 32e is processed mainly to adjust the size of the inner diameter of the guide portion 32c, and the inner diameter is formed with higher precision than other portions of the guide portion 32c.

[0032] The predetermined range where the secondary processed portion 32e is located is a range where the guide portion 32c and a third shaft portion 4c (described later) overlap radially when the drive shaft 4 is inserted into the guide portion 32c and the tip of the drive shaft 4 is axially positioned at the dust lip 30b of the second oil seal 30. The secondary processed portion 32e is formed so that when the third shaft portion 4c is placed axially parallel to the inner circumferential surface of the secondary processed portion 32e in the guide portion 32c, the spline teeth 25 of the drive shaft 4 are positioned higher in the height direction than the lower seal lip 30a and dust lip 30b of the second oil seal 30. The secondary processed portion 32e is preferably thicker than other portions of the guide portion 32c when formed by press working, for example, so that the strength of the guide portion 32c can be ensured even if the inner diameter is adjusted by removal processing such as cutting or grinding.

[0033] When assembling the oil seal structure S configured in this manner, the differential gear unit 3 and the transmission 2 are first assembled and then fastened together, after which the drive shaft 4 is inserted into the transmission case 6 using, for example, a jig. Note that the second oil seal 30 and the guide mechanism 32 are attached to the housing 21 at the above-mentioned positions when the differential gear unit 3 is assembled.

[0034] When assembling the drive shaft 4, first, the first shaft portion 4a of the drive shaft 4 is inserted into the opening in which the bearing 22 of the transmission case 6 is provided. Because the drive shaft 4 is inserted after the transaxle 1 is assembled, the tip of the drive shaft 4 is difficult to see; however, because the tip of the guide portion 32c is tapered portion 32d and the drive shaft 4 becomes gradually thinner toward the tip on the other end side, the drive shaft 4 can be easily inserted into the guide portion 32c.

[0035] Next, the second shaft portion 4b and the third shaft portion 4c are inserted into the guide portion 32c. At this time, the drive shaft 4 is inserted while aligning the lower outer peripheral surface of the drive shaft 4 with the lower inner peripheral surface of the guide portion 32c. At this time, as shown in FIG. 2, when the third shaft portion 4c is inserted, there is an axial gap between the tip of the first shaft portion 4a, i.e., the first shaft portion 4a of the drive shaft 4, and the first shaft portion 4a has not yet reached the position of the second oil seal 30. In other words, the combined axial dimension of the first shaft portion 4a and the second shaft portion 4b is shorter than the guide portion 32c or the combined axial dimension of the guide portion 32c and the trap mechanism 31.

[0036] Furthermore, the outer diameter of the third shaft portion 4c is larger than the outer diameters of the first shaft portion 4a and the second shaft portion 4b. Specifically, the difference between the radius of the first shaft portion 4a and the radius of the third shaft portion 4c is larger than the difference between the radius of the inner circumferential surface of the guide portion 32c and the radius of the inner circumferential portion of the second oil seal 30. Therefore, when the third shaft portion 4c is inserted parallel to the guide portion 32c, a radial gap is generated between the first shaft portion 4a and the second oil seal 30, preventing the tip of the first shaft portion 4a from contacting the second oil seal 30. Although this radial difference between the first shaft portion 4a and the second oil seal 30 is small, this configuration is possible because the inner diameter of the guide portion 32c is formed with higher precision in the axial range from when the third shaft portion 4c is inserted into the guide portion 32c to when the first shaft portion 4a reaches the second oil seal 30 compared to other ranges. Furthermore, since the outer periphery of the tip of the first shaft portion 4a is chamfered, even if the third shaft portion 4c is inserted at an angle relative to the guide portion 32c, it is possible to avoid a situation in which the tip of the first shaft portion 4a comes into contact with and damages the seal lip 30a or dust lip 30b of the second oil seal 30.

[0037] Thereafter, the drive shaft 4 is further inserted while inserting the radially lower outer peripheral surface of the third shaft portion 4c along the lower inner peripheral surface of the guide portion 32c. Then, the drive shaft 4 is inserted while adjusting so that the spline teeth 25 formed on the outer peripheral surface of the first shaft portion 4a mesh with the spline teeth 25 formed on the inner peripheral surface of the differential side gear 10, and the drive shaft 4 is connected to the differential gear unit 3.

[0038] According to the embodiment described above, the housing 21 containing the differential oil 20 and the transmission case 6 containing the fluid 7 are adjacently fastened in the vehicle width direction, and the second oil seal 30, the trap mechanism 31, and the guide mechanism 32 are provided at the boundary between them, where the drive shaft 4 passes. The second oil seal 30 prevents or inhibits the differential oil 20 from reaching the transmission case 6. The trap mechanism 31 is a gap between the inside of the guide mechanism 32 and the second oil seal 30. The guide mechanism 32 is fixed to the housing 21 and extends to near the center of the transmission case 6 in the vehicle width direction. In addition, a tapered portion 32d that widens the opening area of ​​the guide mechanism 32 is provided on the side of the guide portion 32c opposite the trap mechanism 31. The tip of the tapered portion 32d is formed so as to be higher than the so-called dynamic oil level of the fluid 7 that accumulates vertically below it.

[0039] Therefore, even if the acceleration in the vehicle width direction changes due to turning, etc., it is possible to prevent the fluid 7 from entering the inside of the guide portion 32c. Furthermore, even if the point where the changed fluid level is highest becomes higher than the tip of the tapered portion 32d, the highest fluid level is likely to occur on both sides in the vehicle width direction within the transmission case 6, that is, on the side of the large diameter portion 32a or the side of the first oil seal 23. In other words, the fluid level of the fluid 7 corresponding to the lower part of the tapered portion 32d in the vertical direction changes relatively little, so it is possible to prevent or suppress the fluid 7 accumulating at the tip of the tapered portion 32d from reaching the tip of the tapered portion 32d or the fluid 7 from entering the inside of the guide portion 32c.

[0040] Even if fluid 7 splashes and adheres to the drive shaft 4, for example, and enters the guide portion 32c, the trap mechanism 31 captures the fluid 7, preventing or suppressing the fluid 7 from reaching the second oil seal 30. Therefore, even if the pumping force of the second oil seal 30 is generated, the fluid 7 is not drawn in, preventing or suppressing the fluid 7 from entering the housing 21. In other words, without providing two oil seals on the drive shaft 4 at the boundary between the housing 21 and the transmission case 6, mixing of the differential oil 20 and the fluid 7 can be prevented or suppressed. This eliminates the need for one oil seal on the rotating shaft that penetrates between the housings containing different oils, and also eliminates the need to provide a space between the two oil seals to account for the pumping force of the oil seal. This reduces costs and the required axial space.

[0041] Furthermore, since the guide portion 32c is a component that primarily guides the drive shaft 4 to the differential side gear 10 during assembly, it is preferable that the outer peripheral surface of the drive shaft 4 and the inner peripheral surface of the guide portion 32c be formed to have a predetermined gap 34 between them so that they do not slide when assembled. Furthermore, when the drive shaft 4 is inserted into the guide portion 32c and engaged with the differential side gear 10, it is necessary to prevent the spline teeth 25 of the drive shaft 4 from contacting and damaging the second oil seal 30. Therefore, to satisfy these requirements, the inner diameter of the guide portion 32c needs to be formed with high precision. On the other hand, considering that the drive shaft 4 tapers gradually toward the other end and that at least the axial ends of the spline teeth 25 need not contact the seal lip 30a or dust lip 30b of the second oil seal 30, the portion of the guide portion 32c that actually requires a high degree of inner diameter precision may be limited. However, when forming high-precision components by press working, it is necessary to design the mold used mainly when forming the workpiece with high precision, which becomes a factor in increasing costs.

[0042] Therefore, in the oil seal structure according to the embodiment of the present invention, the guide mechanism 32 is formed while maintaining the precision of the press working, and then a secondary removal process is performed only on a predetermined range of the guide portion 32c where high precision is required for the inner diameter. Therefore, compared to forming the guide mechanism 32 by press working with high precision, it is possible to form the predetermined range of the guide portion 32c so that it has a highly precise inner diameter while suppressing increases in cost.

[0043] Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples and may be modified as appropriate within the scope of achieving the object of the present invention. For example, in the above-described embodiment, the trap mechanism 31 is configured to retain the fluid 7 therein. However, a hole for discharging the retained fluid 7 within the trap mechanism 31 may be formed. When forming such a hole, it is preferable to form it in a position that takes into consideration the liquid level of the fluid 7 retained within the transmission case 6. Furthermore, in the above-described embodiment, an LSD is used as the differential gear unit 3. However, the oil seal structure S in the embodiments of the present invention is not limited to LSDs and can also be applied to general differential gear units that do not have a limited slip differential mechanism. [Explanation of symbols]

[0044] 4 Drive shaft (rotating shaft) 6 Transmission case (first housing section) 7 Fluid (primary lubricant) 20 Differential oil (secondary lubricant) 21 Housing (second housing section) 28 Fastening part 30 No. 2 oil seal 31 Trap mechanism 32 Guide mechanism (insertion member) 32a Large diameter section (fastening section) 32b Disc part (fastening part) 32c Guide part (insertion part) 32d tapered section 32e Secondary processing section 34 Prescribed gap S Oil seal structure

Claims

1. a first storage portion that stores a first lubricating oil; a second housing portion fastened adjacent to the first housing portion and configured to house a second lubricant; a rotation axis passing through the fastened portions of the first housing portion and the second housing portion, An oil seal structure that suppresses mixing of the first lubricating oil and the second lubricating oil at a boundary portion where the first accommodating portion and the second accommodating portion on the rotating shaft are fastened, an oil seal provided at the boundary portion on the rotating shaft; an insertion member provided adjacent to the oil seal and into which the rotating shaft is inserted, The insertion member is a cylindrical insertion portion extending into the first accommodating portion and into which the rotating shaft is inserted with a predetermined gap in the radial direction of the rotating shaft; a fastening portion adjacent to the oil seal and fastened to the second accommodating portion at the boundary portion, The oil seal is provided with a trap mechanism in the axial direction of the rotary shaft between the fastening portion and the oil seal, the trap mechanism communicating with the predetermined gap. An oil seal structure characterized by the above.

2. 2. The oil seal structure according to claim 1, The insertion member further has a tapered portion that is provided at an end of the insertion portion opposite the fastening portion in the axial direction and that widens the opening of the insertion portion. An oil seal structure characterized by the above.

3. The oil seal structure according to claim 2, The tip of the tapered portion is higher than the oil level of the accumulated first lubricating oil. An oil seal structure characterized by the above.

4. The oil seal structure according to any one of claims 1 to 3, The insertion member further has a secondary processed portion formed in a predetermined range on the end side of the insertion portion opposite the fastening portion, the secondary processed portion having a smaller dimensional error of the inner diameter than other areas of the insertion portion. An oil seal structure characterized by the above.

5. a first storage portion that stores a first lubricating oil; a second housing portion fastened adjacent to the first housing portion and configured to house a second lubricant; a rotation axis passing through the fastened portions of the first housing portion and the second housing portion, A manufacturing method of an oil seal structure that suppresses mixing of the first lubricating oil and the second lubricating oil at a boundary portion on the rotating shaft where the first accommodating portion and the second accommodating portion are fastened, comprising: an oil seal provided at the boundary portion on the rotating shaft; an insertion member provided adjacent to the oil seal and into which the rotating shaft is inserted, The insertion member is a cylindrical insertion portion extending into the first accommodating portion and into which the rotating shaft is inserted with a predetermined gap in the radial direction of the rotating shaft; a fastening portion adjacent to the oil seal and fastened to the second accommodating portion at the boundary portion, a trap mechanism provided between the fastening portion and the oil seal in the axial direction of the rotating shaft and communicating with the predetermined gap, After assembling the first accommodating portion, the second accommodating portion, the oil seal, and the inserting member, the rotating shaft is inserted along the lower side of the inner circumferential surface of the inserting portion from the opposite side to the fastening portion of the inserting portion, and is assembled to the second accommodating portion. A method for manufacturing an oil seal structure.

6. A manufacturing method of the oil seal structure according to claim 5, The inserting member is formed by press working, and then a predetermined range on the end side of the insertion portion of the inserting member opposite the fastening portion is subjected to cutting or grinding so that the dimensional error of the inner diameter is smaller than that of other ranges in the insertion portion. A method for manufacturing an oil seal structure.

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