Power transmission device

Abstract

The present invention provides a power transmission device that is advantageous in suppressing lubricant leakage caused by pump force by sealing the internal space with a sealing member. [Solution] A power transmission device comprising a pair of relative rotating bodies 16 that rotate relative to each other, and a sealing member 10 disposed between the pair of relative rotating bodies 16, wherein the sealing member 10 has a lip portion 28 that contacts a first relative rotating body 18, which is one of the pair of relative rotating bodies 16, and the lip portion 28 does not have a spring member attached to press the lip portion 28 toward the first relative rotating body 18, and the lip portion 28 has a first corner portion 28a provided at a position radially opposite to the first relative rotating body 18, and the axial contact length La of the lip portion 28 with respect to the first relative rotating body 18 on the axial side of the first corner portion 28a away from the internal space is longer than the axial contact length Lb of the lip portion 28 with respect to the first relative rotating body 18 on the axial side of the first corner portion 28a toward the internal space.

Description

Technical Field

[0001] The present disclosure relates to a power transmission device.

Background Art

[0002] Patent Document 1 discloses a power transmission device including a speed reducer. This power transmission device includes a pair of relative rotators that rotate relative to each other, and a seal member disposed between the pair of relative rotators.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power transmission device of Patent Document 1, as the seal member, a sealed member with a spring member attached to the seal member is used. The sealed member with a spring member locally deforms the lip portion by pressing the corner portion of the lip portion of the seal member against the contact partner by the spring member, and uses the pump force generated between the lip portion and the contact partner to seal the internal space of the power transmission device.

[0005] When sealing the internal space using such a pump force, there is a problem that the internal pressure of the internal space increases due to the air in the outer space on the opposite side of the seal member from the internal space being sucked in by the pump force, and lubricant leakage is likely to occur due to the pump force. Here, the lubricant leakage means that the lubricant enclosed in the internal space leaks into the outer space.

[0006] [[ID=II]] Therefore, one of the objects of the present disclosure is to provide a power transmission device that is advantageous for suppressing lubricant leakage caused by pump force in sealing the internal space with a seal member.

Means for Solving the Problems

[0007] The power transmission device of the present disclosure is a power transmission device equipped with a reduction gear, comprising: a pair of relative rotating bodies that rotate relative to each other; and a sealing member disposed between the pair of relative rotating bodies for sealing the internal space of the power transmission device, wherein the sealing member has a lip portion that contacts a first relative rotating body, which is one of the pair of relative rotating bodies, and the lip portion does not have a spring member attached to it that presses the lip portion toward the first relative rotating body, and the lip portion has a corner portion provided at a position radially opposite to the first relative rotating body, and the axial contact length of the lip portion with respect to the first relative rotating body on the axial side of the corner portion toward the internal space is longer than the axial contact length of the lip portion with respect to the first relative rotating body on the axial side of the corner portion toward the internal space. [Effects of the Invention]

[0008] The power transmission device of this disclosure is advantageous in suppressing lubricant leakage caused by pump force by sealing the internal space with a sealing member. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side cross-sectional view showing the seal member in a deformed state according to the first embodiment. [Figure 2] This is a side cross-sectional view showing the sealing member of the first embodiment in its undeformed state. [Figure 3] Figure 3(A) is a side cross-sectional view showing the seal member in a deformed state according to the second embodiment, and Figure 3(B) is an enlarged view of a part of Figure 3(A). [Figure 4] This is a side cross-sectional view showing a deformed sealing member of the third embodiment. [Figure 5] This is a side cross-sectional view showing the sealing member of the third embodiment in its undeformed state. [Figure 6] This is a side cross-sectional view showing a power transmission device according to the fourth embodiment. [Figure 7]This is a side cross-sectional view showing a power transmission device according to the fifth embodiment. [Figure 8] This is a side cross-sectional view showing a power transmission device according to the sixth embodiment. [Figure 9] This is a side cross-sectional view showing a power transmission device according to the seventh embodiment. [Figure 10] This is a side cross-sectional view showing a part of the power transmission device of the eighth embodiment. [Modes for carrying out the invention]

[0010] Embodiments for implementing the power transmission device of this disclosure are described below. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. For the sake of clarity, components are omitted, enlarged, or reduced in each drawing. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0011] (First Embodiment) Refer to Figure 1. First, the seal member 10 of the first embodiment will be described. The seal member 10 is used in a power transmission device 14 equipped with a reduction gear 12. In addition to the seal member 10, the power transmission device 14 includes a pair of relative rotating bodies 16 that rotate relative to each other. Details of the power transmission device 14 will be described later. Hereinafter, the direction along the rotation centerline (not shown) when the pair of relative rotating bodies 16 rotate relative to each other will be called the axial direction, and the radial and circumferential directions with respect to that rotation centerline will simply be called the radial direction and circumferential direction.

[0012] The pair of relative rotating bodies 16 includes a first relative rotating body 18, which is one of them, and a second relative rotating body 20, which is the other of them. The first relative rotating body 18 has a lip contact surface 18a to which the lip portion 28 of the sealing member 10 contacts. The second relative rotating body 20 has a fixed surface 20a to which the sealing member 10 is fixed. In this embodiment, the first relative rotating body 18 is radially inward relative to the second relative rotating body 20, but it may also be radially outward relative to the second relative rotating body 20.

[0013] The seal member 10 is disposed between the pair of relative rotators 16 and is used to seal the internal space 22 of the power transmission device 14. Hereinafter, the side on the internal space 22 side (the right side in the drawing of FIG. 1) in the axial direction with respect to the seal member 10 is referred to as the inner side in the axial direction, and the side opposite to the internal space 22 in the axial direction (the left side in the drawing of FIG. 1) is referred to as the outer side in the axial direction. The seal member 10 separates the outer space 24 on the outer side in the axial direction with respect to the seal member 10 from the internal space 22.

[0014] The seal member 10 includes a main body portion 26 and a lip portion 28 (first lip portion) provided on the main body portion 26. The main body portion 26 is fixed to the fixed surface 20a of the second relative rotator 20 by interference fit. In addition, the seal member 10 may include, as an optional configuration, a dust lip portion 30 (second lip portion) protruding from the lip portion 28.

[0015] The main body portion 26 of the present embodiment is made of an elastic material such as rubber. In addition, the main body portion 26 may be composed of a combination of a metal ring and an elastic material, or only a metal ring. The lip portion 28 is made of an elastic material such as rubber. The lip portion 28 of the present embodiment is made of the same elastic material as the main body portion 26.

[0016] The main body portion 26 of the present embodiment has an L shape in a cross section cut along the axial direction, but its specific shape is not particularly limited. The main body portion 26 of the present embodiment includes an axially extending portion 26a that extends in the axial direction and is fixed to the second relative rotator 20, and a radially extending portion 26b that extends from the axially outer end portion of the axially extending portion 26a toward the first relative rotator 18 side in the radial direction.

[0017] Refer to FIGS. 1 and 2. When the lip portion 28 of the seal member 10 is in contact with the first relative rotating body 18, it is in a deformed state deformed by the contact with the first relative rotating body 18 (see FIG. 1). On the other hand, when the lip portion 28 is not in contact with the first relative rotating body 18, it is in an undeformed state where it is not deformed (see FIG. 2). It is assumed that the seal member 10 is fixed to the second relative rotating body 20 regardless of whether the lip portion 28 is in the deformed state or the undeformed state. The undeformed state is also a state that can be obtained when the contact between the lip portion 28 and the first relative rotating body 18 is released while the seal member 10 is fixed to the second relative rotating body 20.

[0018] The lip portion 28 is used to prevent leakage of the lubricant enclosed in the internal space 22. The lip portion 28 extends from the axially outer portion of the main body portion 26 toward the axially inner side. As a whole, when the lip portion 28 is in the undeformed state, it extends so as to approach the first relative rotating body 18 side in the radial direction as it goes toward the axially inner side. When the lip portion 28 is in the deformed state, it is elastically bent and deformed so that the tip side thereof bends in the opposite direction to the first relative rotating body 18 in the radial direction compared to when it is in the undeformed state. A pressing force F1 that presses the lip portion 28 against the first relative rotating body 18 acts on the lip portion 28 in the deformed state. This pressing force F1 acts as a repulsive force resulting from the elastic bending deformation of the lip portion 28.

[0019] The lip portion 28 includes a first corner portion 28a provided at a position radially opposed to the first relative rotating body 18, a tip surface 28b continuous with the first corner portion 28a, a first side surface 28c continuous with the first corner portion 28a, a second corner portion 28d provided on the radially opposite side of the first corner portion 28a on the tip surface 28b, and a second side surface 28e continuous with the second corner portion 28d.

[0020] In this specification, the first corner 28a, unlike its usual meaning, refers to the portion of the lip 28 that is convex radially toward the first relative rotating body 18 in a cross-section along the axial direction when the lip 28 is in an undeformed state, and is located furthest radially toward the first relative rotating body 18. The first corner 28a can also be described as the point in a cross-section along the axial direction where an imaginary line parallel to the axial direction touches the lip 28 radially from the first relative rotating body 18 side. In considering the first corner 28a in this way, the existence of other lip portions extending from the lip 28 (for example, the dust lip portion 30 described later) is not considered. The first corner portion 28a is formed by a part of the first side surface 28c that extends radially toward the second relative rotating body 20 as it moves away from the internal space 22 in the axial direction from the point on the first relative rotating body 18 side of the lip portion 28, and a part of the tip surface 28b that extends radially toward the second relative rotating body 20 as it moves away from that point in the axial direction toward the internal space 22. In this embodiment, the first corner portion 28a is formed by the tip portion that is located on the first relative rotating body 18 side in the radial direction of the pointed portion that is convex radially toward the first relative rotating body 18 side when the lip portion 28 is in an undeformed state. Alternatively, the first corner portion 28a may be formed by the portion that is located on the first relative rotating body 18 side in the radial direction of the curved portion that is convex radially toward the first relative rotating body 18 side when the lip portion 28 is in an undeformed state.

[0021] The tip surface 28b faces the internal space 22 in the axial direction and is located furthest inward in the axial direction of the lip portion 28. In this embodiment, the tip surface 28b is positioned such that, when the lip portion 28 is in a deformed state, it is perpendicular to the lip contact surface 18a in the axial cross-section. Here, "perpendicular" includes not only cases where it is geometrically strictly perpendicular to the lip contact surface 18a, but also cases where it is approximately perpendicular. Here, "approximately perpendicular" includes, for example, cases where it is within ±10° of the position where it is strictly perpendicular to the lip contact surface 18a. The first side surface 28c is positioned radially opposite to the first relative rotating body 18, similar to the first corner portion 28a. The second side surface 28e faces radially opposite to the first side surface 28c.

[0022] The dust lip portion 30 is provided to prevent dust from entering the internal space 22 from the outer space 24. The dust lip portion 30 extends axially outward from the lip portion 28 and contacts the lip contact surface 18a of the first relative rotating body 18 with elastic deformation.

[0023] The lip portion 28 does not have a spring member attached to it that presses against the first relative rotating body 18. This spring member is, for example, an endless circumferentially continuous garter spring. This spring member is separate from the lip portion 28 and is attached to the second side surface 28e of the lip portion 28.

[0024] The axial contact length of the entire lip portion 28 with respect to the first relative rotating body 18 is called the contact length L0. Here, the axial contact length refers to the axial length of the contact points of the lip portion 28 with respect to the first relative rotating body 18. When considering the total contact length L0 of the lip portion 28, as shown in Figure 4, if the lip portion 28 is in contact with the first relative rotating body 18 at multiple contact points spaced apart in the axial direction, the sum of the axial lengths of the multiple contact points is used. For example, Figure 4 shows an example where the lip portion 28 is in contact with the first relative rotating body 18 at four contact points, and the contact lengths of the individual contact points are L0(1) to L0(4). In this case, the total contact length L0 of the lip portion 28 is the sum of the individual contact lengths L0(1) to L0(4). When considering the total contact length L0 of the lip portion 28, the axial length of the contact points of other lip portions protruding from the lip portion 28, such as the dust lip portion 30, with respect to the first relative rotating body 18 is not considered. The same concept described here applies to the outer contact length La and inner contact length Lb, which will be explained next.

[0025] The axial contact length of the lip portion 28 with respect to the first relative rotating body 18 at an axially outward position from the first corner portion 28a of the sealing member 10 is called the outer contact length La, and the contact length of the lip portion 28 with respect to the first relative rotating body 18 at an axially inward position from the first corner portion 28a is called the inner contact length Lb. The outer contact length La is also the contact length of the entire first side surface 28c with respect to the first relative rotating body 18. The inner contact length Lb is also the contact length of the entire tip surface 28b with respect to the first relative rotating body 18. The total contact length L0 of the lip portion 28 is the sum of the outer contact length La and the inner contact length Lb of the lip portion 28.

[0026] In this embodiment, the length condition is satisfied such that the outer contact length La of the lip portion 28 is longer than its inner contact length Lb. In satisfying this length condition, there are two cases: (1) when the inner contact length Lb of the lip portion 28 is zero, and (2) when the inner contact length Lb of the lip portion 28 is greater than zero. The embodiment in Figure 1 shows case (1). In this case, the length condition is satisfied regardless of the magnitude of the outer contact length La of the lip portion 28. In this case, the total contact length L0 of the lip portion 28 = the outer contact length La of the lip portion 28. In this case, with respect to the first relative rotating body 18, only the first side surface 28c of the lip portion 28 and the tip surface 28b of the lip portion 28 are in contact, and the tip surface 28b is not in contact (hereinafter referred to as the surface contact form).

[0027] Figures 3(A) and 3(B) show the sealing member 10 of the second embodiment, as described in (2) above. In Figure 3(B), the deformed lip portion 28 is shown by a solid line, and a part of the undeformed lip portion 28 is shown by a dashed line. In the case of (2) above, the lip portion 28, including the first corner portion 28a, is deformed to conform to the first relative rotating body 18, resulting in a contact configuration (hereinafter referred to as the corner contact configuration) where both the tip surface 28b and the first side surface 28c are in contact. In this case, the first corner portion 28a of the lip portion 28 appears to be flat in the axial direction, extending along the axial direction in a cross-section along the axial direction, together with the tip surface 28b and a part of the first side surface 28c of the lip portion 28. In other words, when the lip portion 28 is in a deformed state, the portion of the lip portion 28 including the first corner portion 28a does not appear to be convex radially toward the first relative rotating body 18. In Figure 3(B), for the sake of explanation, the position of the first corner 28a of the deformed lip portion 28 is indicated by a reference numeral.

[0028] As described in (1) above, the advantage of satisfying the length condition mentioned above by having zero inner contact length Lb of the lip portion 28, that is, the advantage of the surface contact configuration, will be explained. If the inner contact length Lb of the lip portion 28 is greater than zero, the angular contact configuration shown in Figure 3 will be obtained. In the angular contact configuration, means to increase the overall contact length L0 of the lip portion 28 will be considered. As a means to do this, a first means is envisioned in which the amount of bending deformation of the lip portion 28 is increased during the assembly process of the seal member 10, and the first side surface 28c of the lip portion 28 is greatly deformed to follow the lip contact surface 18a of the first relative rotating body 18. In addition, a second means is envisioned in which a spring member is used to apply a pressing force to the lip portion 28 that presses the lip portion 28 against the first relative rotating body 18, thereby increasing the amount of crushing deformation of the portion of the lip portion 28 including the first corner 28a.

[0029] In this case, if an angular contact configuration is achieved, employing the first method would result in a large amount of bending deformation of the lip portion 28, which would prevent the tip surface 28b of the lip portion 28 from contacting the first relative rotating body 18, making it impossible to maintain the angular contact configuration. Therefore, employing the first method to increase the overall contact length L0 of the lip portion 28 is not practical when an angular contact configuration is achieved. Furthermore, in this configuration, since no spring member is attached to the lip portion 28 of the sealing member 10, the second method cannot be employed either. Consequently, when an angular contact configuration is achieved, neither the first nor the second method can be employed, and there are limits to how much the overall contact length L0 of the lip portion 28 can be increased.

[0030] In contrast, in the case of surface contact, it is not necessary to bring the tip surface 28b of the lip portion 28 into contact with the first relative rotating body 18, as is the case in the case of angular contact. Therefore, in this case, the amount of bending deformation of the lip portion 28 can be easily increased by employing the first means, and consequently, the overall contact length L0 of the lip portion 28 can be easily increased. As a result, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be easily reduced compared to the case of angular contact. Contact pressure here refers to the force per unit area acting on the contact point of the lip portion 28 with respect to the contact object.

[0031] Next, as described in (2) above, the advantage of satisfying the length condition described above when the inner contact length Lb of the lip portion 28 is greater than zero, that is, in the case of angular contact, will be explained. In this case, the total contact length L0 of the lip portion 28 can be made longer compared to the case where the outer contact length La of the lip portion 28 is the same as the inner contact length Lb. Therefore, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be actually reduced compared to the case where the outer contact length La is the same as the inner contact length Lb.

[0032] To summarize the above, in order to satisfy the length condition, we consider the case where the inner contact length Lb of the lip portion 28 is zero (surface contact form), as in (1). In this case, compared to the case where the inner contact length Lb is greater than zero (corner contact form), the overall contact length L0 of the lip portion 28 can be easily increased, and consequently, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be easily reduced. In this case, compared to the corner contact form, the difficulty of increasing the overall contact length L0 of the lip portion 28 can be reduced, and the difficulty of reducing the contact pressure of the lip portion 28 can also be reduced.

[0033] Next, in order to satisfy the length condition, we consider the case where the inner contact length Lb of the lip portion 28 is greater than zero, as in (2). In this case, compared to the case where the outer contact length La is the same as the inner contact length Lb, the total contact length L0 of the lip portion 28 can be made longer, and consequently, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be reduced.

[0034] In satisfying the length requirement, both cases (1) and (2) are advantageous in increasing the overall contact length L0 of the lip portion 28 and in reducing the contact pressure of the lip portion 28 compared to the specific case. The specific case here is, in (1), when the inner contact length Lb is greater than zero (in the case of angular contact), and in (2), when the outer contact length La is the same as the inner contact length Lb.

[0035] The effects of the power transmission device 14 using the above-described sealing member 10 will now be explained.

[0036] (A) It is known that the pumping force can be reduced as the contact pressure acting on the lip portion 28 of the sealing member 10 with respect to the contacting object is reduced. In this embodiment, the sealing member 10 does not have a spring member attached to the lip portion 28. Therefore, compared to a sealing member with a spring, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be actually reduced. In addition, satisfying the aforementioned length condition is advantageous in reducing the contact pressure of the lip portion 28 with respect to the first relative rotating body 18, as described above. These factors together are advantageous in greatly reducing the pumping force generated between the first relative rotating body 18 and the lip portion 28. The internal space 22 is sealed mainly by the pressing force F1 of the lip portion 28, without relying on pumping force. Therefore, the rise in internal pressure of the internal space 22 due to pumping force can be suppressed, which is advantageous in suppressing lubricant leakage caused by pumping force.

[0037] (B) When a spring-loaded seal member is used, the contact pressure at the lip portion 28 becomes very high due to the pressing force of the spring member. As a result, when the power transmission device 14 is operated at high acceleration and deceleration, the lip portion 28 twists relative to the first relative rotating body 18, which makes lubricant leakage more likely. In this respect, the present embodiment is advantageous in reducing the contact pressure of the lip portion 28 relative to the first relative rotating body 18, as described above. Therefore, when the power transmission device 14 is operated at high acceleration and deceleration, the lip portion 28 is less likely to twist relative to the first relative rotating body 18, which is advantageous in suppressing lubricant leakage caused by this.

[0038] (C) In this embodiment, only the first side surface 28c of the seal member 10 is in contact with the first relative rotating body 18, and as described above, it can be made into a surface contact state. Therefore, compared to the case of angular contact, by increasing the amount of bending deformation of the lip portion 28, it becomes easier to deform the first side surface 28c of the lip portion 28 to follow the lip contact surface 18a of the first relative rotating body 18, and consequently the overall contact length L0 of the lip portion 28 can be easily increased. For this reason, compared to a spring-loaded seal member, the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 can be easily reduced, which is advantageous in greatly reducing the pumping force generated between the first relative rotating body 18 and the lip portion 28. As a result, the rise in internal pressure of the internal space 22 due to the pumping force can be greatly suppressed, which is particularly advantageous in suppressing lubricant leakage caused by the pumping force.

[0039] Next, other features of the sealing member 10 will be described. Refer to Figure 2. Assume that the axial length L28b of the tip surface 28b of the lip portion 28 is in an undeformed state. This axial length L28b refers to the length in the axial direction from the first corner 28a of the lip portion 28 to the point on the tip surface 28b that is furthest inward in the axial direction, when the lip portion 28 is in an undeformed state. The contact length L0 may preferably be longer than the axial length L28b. This contact length L0 may more preferably be twice or more the axial length L28b. The upper limit of this contact length L0 is not particularly limited in relation to the axial length L28b, and may, for example, be 20 times or less the axial length L28b, or may be set appropriately within a realistic range for manufacturing.

[0040] (D) This significantly reduces the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 compared to the case where the contact length L0 is less than or equal to the axial length L28b, and thus significantly reduces the aforementioned pumping force. Consequently, the rise in internal pressure of the internal space 22 due to the pumping force can be greatly suppressed, which is particularly advantageous in suppressing lubricant leakage caused by this. Note that the contact length L0 may be less than or equal to the axial length L28b.

[0041] We assume a minimum thickness T of the lip portion 28 at the point of contact with the first relative rotating body 18. This minimum thickness T refers to the minimum radial thickness of the lip portion 28 at a point that radially overlaps with the point of contact with the first relative rotating body 18. When considering the minimum thickness T, we do not consider the thickness of the lip portion 28 at non-contact points with the first relative rotating body 18, as shown in Figure 4. A non-contact point of the lip portion 28 here refers to, for example, a point that radially overlaps with the groove portion 34, as shown in Figure 4. In the configuration of Figure 2, the minimum thickness T occurs at a point that radially overlaps with the first corner portion 28a of the lip portion 28, but the minimum thickness T may occur at a different point.

[0042] In this case, the total contact length L0 of the lip portion 28 may preferably be longer than its minimum thickness T. The upper limit of this contact length L0 is not particularly limited in relation to the minimum thickness T, and may be, for example, 10 times or less of the minimum thickness T, or it may be set appropriately within a range that is practical for manufacturing.

[0043] (E) This significantly reduces the contact pressure of the lip portion 28 with respect to the first relative rotating body 18 compared to the case where the contact length L0 is less than or equal to the minimum thickness T, and thus significantly reduces the aforementioned pumping force. Consequently, the rise in internal pressure of the internal space 22 due to the pumping force can be greatly suppressed, which is particularly advantageous in suppressing lubricant leakage caused by this. Note that the contact length L0 may be less than or equal to the minimum thickness T.

[0044] The lubricant sealed in the internal space 22 may contain at least one of the following: Mo (molybdenum), S (sulfur), Ca (calcium), Zn (zinc), Ba (barium), Mg (magnesium), P (phosphorus), C (carbon), B (boron), and W (tungsten). The lubricant may be, for example, a general-purpose grease containing at least one of these.

[0045] (F) It is known that when such lubricants are used, precipitates are generated due to heat generation. When such precipitates are generated due to heat generation at the contact point of the lip portion 28 with the first relative rotating body 18, there is a problem that lubricant leakage is likely to occur due to the deposition getting stuck between them. In this respect, the present embodiment is advantageous in reducing the contact pressure of the lip portion 28 with the first relative rotating body 18, as described above. Therefore, by reducing the contact pressure, heat generation at the contact point of the lip portion 28 with the first relative rotating body 18 is suppressed, and this is also advantageous in suppressing the generation of precipitates caused by that heat generation. Consequently, even when using a lubricant that may generate precipitates due to heat generation, this is advantageous in suppressing lubricant leakage caused by the deposition getting stuck.

[0046] Furthermore, the type of lubricant is not particularly limited, and it does not need to contain the various elements mentioned above.

[0047] (Third Embodiment) Next, we will move on to describing other embodiments. In the following embodiments (including the second embodiment), the same content as in the first embodiment may apply to the components described in the first embodiment that are not described below.

[0048] Refer to Figures 4 and 5. The lip portion 28 of the sealing member 10 has a contact area 32 that includes the entire contact area of ​​the lip portion 28 with the first relative rotating body 18. The contact area 32 is provided in an axial range from the inner end position on the axial side to the outer end position on the axial side, within the entire contact area of ​​the lip portion 28 with the first relative rotating body 18. The contact area 32 is provided on the first side surface 28c of the lip portion 28 within this axial range.

[0049] The contact area 32 is provided with at least one groove 34. In this embodiment, the contact area 32 is provided with multiple (specifically three) grooves 34, but the number is not particularly limited and may be one, two, or four or more. A lubricant such as grease (not shown) is applied to the contact area 32. The grooves 34 function as lubricant reservoirs for holding the lubricant. This lubricant may be the same as or different from the lubricant sealed in the internal space 22.

[0050] The effects of the above features will now be explained. A lubricating film is formed by the lubricant at the contact point of the lip portion 28 with respect to the first relative rotating body 18. If the lubricating film breaks down at this contact point, there is a problem that lubricant leakage is likely to occur. In this regard, a groove 34 is provided in the contact area 32 of the lip portion 28 in this embodiment. Therefore, by utilizing the groove 34 of the lip portion 28 as a lubricant reservoir, lubricating failure at the contact point of the lip portion 28 with respect to the first relative rotating body 18 can be suppressed. This, in turn, is advantageous in suppressing lubricant leakage caused by such lubricating failure.

[0051] According to this embodiment, foreign matter passing between the lip portion 28 of the sealing member 10 and the first relative rotating body 18 can be captured in the groove portion 34. This suppresses the jamming of foreign matter (especially wear particles, described later) between the contact point of the lip portion 28 with the first relative rotating body 18 and the first relative rotating body 18, which is advantageous in suppressing lubricant leakage caused by such jamming.

[0052] When the power transmission device 14 is started frequently or used in forward and reverse operation, the sliding speed of the lip portion 28 of the sealing member 10 against the first relative rotating body 18 slows down or becomes zero, making it easy for boundary lubrication, which is prone to lubrication failure, to occur. According to this embodiment, even when such a lubrication condition prone to lubrication failure occurs, using the groove portion 34 of the lip portion 28 as a lubricant reservoir is advantageous in suppressing lubricant leakage caused by such lubrication failure.

[0053] In addition, the power transmission device 14 of this embodiment also has the components described in (A) to (F) above, and can obtain the effects corresponding to those descriptions.

[0054] Furthermore, when a groove 34 is provided in the lip portion 28 as in this embodiment, a lubricant with an NLGI consistency number of 2 to 6 may be applied to the contact area 32 of the lip portion 28. Hard lubricants with consistency numbers of 2 to 6 have poor conformability and are prone to lubrication failure. According to this embodiment, even when using such a lubricant that is prone to lubrication failure, the groove 34 of the lip portion 28 is used as a lubricant reservoir, which is advantageous in suppressing lubricant leakage caused by such lubrication failure.

[0055] Refer to Figure 5. When the lip portion 28 is in an undeformed state, at least a portion of at least one groove portion 34 may be located radially toward the first relative rotating body 18 than the lip contact surface 18a of the first relative rotating body 18. In this embodiment, the entirety of at least one groove portion 34 is located radially toward the first relative rotating body 18 than the lip contact surface 18a of the first relative rotating body 18. In order to satisfy this condition, at least two groove portions 34 may be located radially toward the first relative rotating body 18 than the lip contact surface 18a of the first relative rotating body 18. This makes it possible to increase the amount of bending deformation of the lip portion 28 when it is in a deformed state, compared to the case where this condition is not satisfied. Consequently, the contact length L0 of the entire lip portion 28 can be easily increased, and by reducing the contact pressure of the lip portion 28, it is particularly advantageous in suppressing the rise in internal pressure of the internal space 22 due to the pump force.

[0056] Next, the details of the power transmission device 14 will be described. Here, the power transmission devices 14 of the fourth to seventh embodiments will be described. Below, the individual features of the power transmission devices 14 of these embodiments will be described, followed by the features related to the sealing member 10 mentioned above. Furthermore, the contents described for the power transmission devices 14 of these embodiments may also be applied to the power transmission devices 14 of the first to third embodiments.

[0057] (Fourth Embodiment) Refer to Figure 6. The power transmission device 14 in this embodiment comprises only a reduction gear 12. The reduction gear 12 can drive a driven body (not shown) by reducing the input rotation and outputting that rotation. Rotation is input to the reduction gear 12 from a prime mover (not shown) such as a motor or engine. The driven body is, for example, at least a part of various machines such as (1) industrial machinery such as machine tools and construction machinery, (2) robots such as industrial robots and service robots, (3) transport equipment such as conveyors, and (4) vehicles.

[0058] The reducer 12 comprises a reduction mechanism 42, a reducer casing 44 in which the reduction mechanism 42 is arranged, and an anti-input side member 46 which is provided at least partially on the axial anti-input side with respect to the reduction mechanism 42 and is rotatable relative to the reducer casing 44 around the rotation centerline Ca.

[0059] The reduction gear 12 in this embodiment uses a flexible meshing type reduction mechanism as the reduction mechanism 42. The reduction gear 12 using this mechanism comprises a vibrator shaft 50 having a vibrator 48, a flexible gear 52 that is deformed by the vibrator 48, and meshing gears 54A and 54B that mesh with the flexible gear 52. The vibrator shaft 50 in this embodiment functions as an input member to which rotation is input directly or indirectly from the outside. The flexible gear 52 and the meshing gears 54A and 54B function as a reduction mechanism 42 that reduces the rotation input from the input member. One of the flexible gear 52 and the meshing gears 54A and 54B is an external gear, and the other is an internal gear. Here, an example in which the flexible gear 52 is an external gear and the meshing gears 54A and 54B are internal gears will be described. The anti-input side member 46 in this embodiment functions as an output member that extracts the rotation reduced by the reduction mechanism 42 and outputs it to the driven body. The output member may be replaced with a gearbox casing 44 instead of the non-input side member 46.

[0060] The vibrator shaft 50 includes the vibrator 48, as well as shaft portions 58 provided on both sides of the vibrator 48 in the axial direction. The cross-sectional shape of the outer circumference of the vibrator 48 is elliptical. The cross-sectional shape of the outer circumference of the shaft portion 58 is circular. Here, the cross-sectional shape refers to the shape of the cross section perpendicular to the axial direction of the vibrator 48. Here, "elliptical" is not limited to a geometrically strictly elliptical shape, but also includes an approximate ellipse.

[0061] The flexible gear 52 is a cylindrical member with flexibility that is deformed by the vibrator 48 via the vibrator bearing 60. The meshing gears 54A and 54B have sufficient rigidity to not deform by bending in accordance with the rotation of the vibrator 48. The meshing gears 54A and 54B in this embodiment include a first meshing gear 54A that meshes with the teeth on the input side of the flexible gear 52, and a second meshing gear 54B that meshes with the teeth on the non-input side of the flexible gear 52. The first meshing gear 54A has a different number of teeth (e.g., 102) than the number of teeth of the flexible gear 52 (e.g., 100), and the second meshing gear 54B has the same number of teeth as the number of teeth of the flexible gear 52.

[0062] In this embodiment, the gearbox casing 44 also serves as the first meshing gear 54A. The gearbox casing 44 in this embodiment is constructed using multiple casing members connected by bolts or the like. A bearing 62 is positioned between the gearbox casing 44 in this embodiment and the shaft portion 58 of the vibrator shaft 50. The non-input side member 46 in this embodiment also serves as the second meshing gear 54B. A bearing 64 is positioned between the non-input side member 46 and the shaft portion 58 of the vibrator shaft 50. The non-input side member 46 in this embodiment is constructed using multiple members connected by bolts or the like. A main bearing 66 is positioned between the gearbox casing 44 and the non-input side member 46.

[0063] An example of the operation of the power transmission device 14 according to this embodiment will be described. In this embodiment, when the vibrator shaft 50, which is the input member, rotates, the flexible gear 52 is deformed to form an elliptical shape that matches the shape of the vibrator 48 on the vibrator shaft 50. When the flexible gear 52 deforms in this way, the meshing position between the flexible gear 52 and the meshing gears 54A and 54B changes in the direction of rotation of the vibrator 48. At this time, with each rotation of the flexible gear 52 and the first meshing gear 54A, which have different numbers of teeth, the meshing teeth of these gears shift in the circumferential direction. As a result, in this embodiment, the flexible gear 52 rotates on its own axis, and its rotational component is extracted by the anti-input side member 46, which is the output member. In this configuration, the flexible gear 52 and the second meshing gear 54B have the same number of teeth and are therefore synchronized. The rotational component of the flexible gear 52 is extracted by the non-input side member 46, which is the output member, through the second meshing gear 54B, which is synchronized with the flexible gear 52. At this time, the output rotation is extracted from the input rotation input to the vibrator shaft 50 at a reduction ratio corresponding to the difference in the number of teeth between the flexible gear 52 and the first meshing gear 54A.

[0064] (Fifth Embodiment) Refer to Figure 7. The gear reducer 12 in the embodiments shown in Figures 7 to 9 uses an eccentric oscillating gear reducer as the reduction mechanism 42. In particular, the gear reducer 12 in this embodiment uses a center crank type eccentric oscillating gear reducer. The gear reducer 12 using this comprises a crankshaft 72 having an eccentric portion 70, an oscillating gear 74 that oscillates due to the eccentric portion 70, and a meshing gear 76 that meshes with the oscillating gear 74. In this embodiment, the crankshaft 72 functions as an input member. The oscillating gear 74 and the meshing gear 76 function as the reduction mechanism 42. One of the oscillating gear 74 and the meshing gear 76 is an external gear, and the other is an internal gear. Here, we will describe an example in which the oscillating gear 74 is an external gear and the meshing gear 76 is an internal gear. In this embodiment, the anti-input side member 46 functions as an output member.

[0065] The non-input side member 46 in this embodiment comprises a flange portion 46a provided on the non-input side with respect to the reduction mechanism 42, and a shaft portion 46b provided on the non-input side with respect to the flange portion 46a and having a smaller diameter than the flange portion 46a. A collar 78 is attached to the shaft portion 46b in this embodiment so as to be able to rotate integrally with the shaft portion 46b.

[0066] In this embodiment, the crankshaft 72 is mounted on the rotational centerline Ca. The crankshaft 72 has at least one (two in this case) eccentric portion 70. The eccentric portion 70 has a circular shape that is eccentric with respect to the rotational centerline C72 of the crankshaft 72. In this embodiment, the eccentric portion 70 is mounted separately from the other parts of the crankshaft 72, but as shown in the embodiments of Figures 8 and 9, it may be mounted integrally with the other parts of the crankshaft 72 using the same material. The oscillating gear 74 is mounted corresponding to the eccentric portion 70 and is supported by the corresponding eccentric portion 70 via an eccentric bearing 80.

[0067] In this embodiment, the meshing gear 76 is provided on the inner circumference of the reduction gear casing 44. The meshing gear 76 comprises a gear body 76a, which is also the reduction gear casing 44, and teeth 76b provided on the gear body 76a. In this embodiment, the teeth 76b is composed of a roller 76d that is rotatably mounted on a support pin 76c supported by the gear body 76s. Alternatively, as shown in the embodiment of Figure 8, the meshing gear 76 may consist of a support pin 76c that constitutes the teeth 76b, and may not have a roller 76d. In addition, as shown in the embodiment of Figure 9, the teeth 76b of the meshing gear 76 may be integrally provided from the same material as the gear body 76a.

[0068] In this embodiment, a pin 82 protrudes from the anti-input side member 46, passing through the oscillating gear 74. The pin 82 directly or indirectly contacts the oscillating gear 74, enabling synchronization of the rotational component of the oscillating gear 74 with the anti-input side member 46.

[0069] An example of the operation of the power transmission device 14 according to this embodiment will be described. When the crankshaft 72, which is the input member, rotates, the oscillating gear 74 oscillates due to its eccentric portion 70. When the oscillating gear 74 oscillates, the meshing position between the oscillating gear 74 and the meshing gear 76 changes in the circumferential direction. Accordingly, with each rotation of the crankshaft 72, the oscillating gear 74 rotates on its own axis, and this rotational component is extracted via the pin 82 by the non-input side member 46, which is the output member. At this time, the output rotation is extracted with a reduction ratio corresponding to the difference in the number of teeth between the oscillating gear 74 and the meshing gear 76, relative to the input rotation input to the crankshaft 72.

[0070] (Sixth Embodiment) Refer to Figure 8. In this embodiment, the power transmission device 14 includes, in addition to the reduction gear 12, a prime mover 90, an adapter 92 connecting the prime mover 90 and the reduction gear 12, and a disc-shaped driven body 94 driven by the reduction gear 12. Thus, the power transmission device 14 may include only the reduction gear 12, or it may include one or more of the prime mover 90, adapter 92, and driven body 94 in addition to the reduction gear 12.

[0071] The prime mover 90 in this embodiment is a motor. The prime mover 90 comprises a prime mover casing 96 and a drive shaft 98 for outputting the rotation generated inside the prime mover 90. The prime mover casing 96 is connected to the gearbox casing 44 via an adapter 92.

[0072] In this embodiment, the reduction gear 12 uses a center crank type eccentric oscillating reduction mechanism 42, similar to the embodiment in Figure 7. The crankshaft 72 of the reduction gear 12 in this embodiment is connected to the drive shaft 98 so as to be able to rotate integrally with it using a key or the like. The crankshaft 72 in this embodiment has three eccentric portions 70. The reduction gear 12 in this embodiment includes a carrier 100 provided on the input side relative to the reduction mechanism 42. The carrier 100 is integrally connected to the non-input side member 46 by a pin 82. The main bearing 66 is positioned between the reduction gear casing 44 and the non-input side member 46, and also between the reduction gear casing 44 and the carrier 100.

[0073] (Seventh Embodiment) Refer to Figure 9. The power transmission device 14 in this embodiment, like the embodiment in Figure 8, includes a prime mover 90, an adapter 92, and a driven body 94 in addition to the reduction gear 12.

[0074] The reduction gear 12 in this embodiment uses a distribution-type eccentric oscillation reduction mechanism 42. Multiple crankshafts 72 (only one is shown here) of the reduction gear 12 using this reduction mechanism 42 are provided at positions radially offset with respect to the rotation centerline Ca. A crankshaft gear 102 is provided on each of the multiple crankshafts 72 so as to be able to rotate together. The crankshaft gear 102 meshes with an input pinion 106 provided on an intermediate shaft 104. The intermediate shaft 104 is connected to the drive shaft 98 so as to be able to rotate together using a key or the like. Rotation is input to each of the multiple crankshafts 72 from the drive shaft 98 via the intermediate shaft 104 and the crankshaft gear 102.

[0075] Next, we will describe the features related to the sealing member 10 of the power transmission device 14 described in the fourth to seventh embodiments. The following description will mainly refer to Figure 6. In each embodiment, there are multiple sealing members 10 and multiple pairs of relative rotating bodies 16. To distinguish these multiple sealing members 10 and multiple pairs of relative rotating bodies 16, the designations "-A", "-B", and "-C" are added to the end of their reference numerals.

[0076] Each form of the reduction mechanism 42 is composed of a gear mechanism 110. The gear mechanism 110 includes a gear set 112 composed of multiple gears that mesh with each other. The gear set 112 in the form of Figure 6 is composed of a flexible gear 52 and meshing gears 54A and 54B. The gear set 112 in the forms of Figures 7 to 9 is composed of an oscillating gear 74 and meshing gears 76. The gear set 112 is composed of a metallic material such as an iron-based material or an aluminum-based material, but it may also be composed of a resin-based material.

[0077] The power transmission device 14 includes at least one pair of relative rotating bodies 16-A and 16-B that rotate relative to each other around the rotation centerline Ca when the power transmission device 14 is in operation. When the power transmission device 14 is in operation, it means when each power transmission element of the power transmission device 14 is in operation. The power transmission elements here refer to, for example, an input member, a part of the reduction mechanism 42 (flexible gear 52, oscillating gear 74, etc.), an output member, etc.

[0078] In the configurations shown in Figures 6 to 9, at least one pair of relative rotating bodies 16-A and 16-B includes a pair of high-speed relative rotating bodies 16-A that rotate relative to each other at a first relative rotational speed, and a pair of low-speed relative rotating bodies 16-B that rotate relative to each other at a second relative rotational speed slower than the first relative rotational speed. One of the pair of high-speed relative rotating bodies 16-A is composed of a fixed body 114 that is fixed to an external member (not shown) that supports the power transmission device 14, and the other of the high-speed relative rotating bodies 16-A is composed of a high-speed rotating body 116A that rotates relative to the fixed body 114. One of the pair of low-speed relative rotating bodies 16-B is composed of a fixed body 114, and the other of the low-speed relative rotating bodies 16-B is composed of a low-speed rotating body 116B that rotates at a lower speed than the high-speed rotating body 116A relative to the fixed body 114. Thus, one of the pair of relative rotating bodies 16-A and 16-B is composed of rotating bodies 116A and 116B. One of the stationary body 114 and the high-speed rotating body 116A becomes the aforementioned first relative rotating body 18, and the other becomes the second relative rotating body 20. Also, one of the stationary body 114 and the low-speed rotating body 116B becomes the aforementioned first relative rotating body 18, and the other of them becomes the second relative rotating body 20.

[0079] In the configuration shown in Figure 6, the stationary body 114 is the gearbox casing 44, the high-speed rotating body 116A is the exciter shaft 50, and the low-speed rotating body 116B is the anti-input side member 46. Also, in the configuration shown in Figure 7, the stationary body 114 is the gearbox casing 44, the high-speed rotating body 116A is the crankshaft 72, and the low-speed rotating body 116B is a combination of the anti-input side member 46 and the collar 78. In the configuration shown in Figure 8, the stationary body 114 is a combination of the gearbox casing 44, the adapter 92, and the prime mover casing 96, the high-speed rotating body 116A is a combination of the crankshaft 72 and the prime mover shaft 98, and the low-speed rotating body 116B is a combination of the anti-input side member 46 and the driven body 94. In the configuration shown in Figure 9, the stationary body 114 is a combination of a reduction gear casing 44, an adapter 92, and a prime mover casing 96; the high-speed rotating body 116A is a combination of an intermediate shaft 104 and a prime mover shaft 98; and the low-speed rotating body 116B is a combination of an anti-input side member 46 and a driven body 94. In the configurations shown in Figures 6 to 9, the high-speed rotating body 116A and the low-speed rotating body 116B become the first relative rotating body 18, and the stationary body 114 becomes the second relative rotating body 20. Thus, the specific examples of the stationary body 114, the high-speed rotating body 116A, and the low-speed rotating body 116B are not particularly limited.

[0080] In the configurations shown in Figures 6 to 8, the pair of high-speed relative rotating bodies 16-A are used in the reduction gear 12 and include a reduction gear rotating shaft 118 that rotates when the power transmission device 14 is in operation. This reduction gear rotating shaft 118 is either, for example, a vibrator shaft 50 that causes a flexible gear 52 to bend and deform, as in the configuration of Figure 6, or a crankshaft 72 that causes an oscillating gear 74, as in the configurations of Figures 7 and 8.

[0081] As shown in the embodiments of Figures 6 to 9, the sealing members 10-A to 10-C may include a first sealing member 10-A positioned between at least a pair of high-speed relative rotating bodies 16-A. In addition, the sealing members 10-A to 10-C may include a second sealing member 10-B positioned between a pair of low-speed relative rotating bodies 16-B. Furthermore, as shown in the embodiment of Figure 6, the sealing members 10-A to 10-C may include a third sealing member 10-C positioned between a high-speed rotating body 116A which is one of the pair of high-speed relative rotating bodies 16-A and a low-speed rotating body 116B which is one of the pair of low-speed relative rotating bodies 16-B. The features described in the first to third embodiments may be applied to these sealing members 10-A to 10-C.

[0082] A reduction gear 42 is arranged in the internal space 22 of the power transmission device 14, which is sealed by sealing members 10-A to 10-C. In each of the embodiments shown in Figures 6 to 9, the internal space 22 is formed in a location surrounded by at least a stationary body 114 (reducer casing 44), a high-speed rotating body 116A, and a low-speed rotating body 116B (anti-input side member 46). In the embodiments shown in Figures 6 to 9, at least one of the reducer casing 44 and the anti-input side member 46 also serves as a component of the reduction gear 42 (for example, meshing gears 54A, 54B, and meshing gear 76). In other words, the space-forming body that forms the internal space 22 also serves as a component of the reduction gear 42. In this case, in order to satisfy the condition that the reduction gear 42 is arranged in the internal space 22, it is sufficient that at least one component of the reduction gear 42 that is different from the component that the space-forming body serves as (for example, flexible gears 52 and 74) is arranged in the internal space 22.

[0083] The internal space 22 is filled with a lubricant (not shown). The lubricant is used to lubricate the points where sliding or rolling contact occurs between the components of the reduction mechanism 42. The points where sliding or rolling contact occurs refer, for example, to the meshing points of the multiple gears that make up the gear set 112. The lubricant in the forms shown in Figures 6 to 9 is grease, but the specific example is not particularly limited, and for example, lubricating oil may also be used. The internal space 22 is sealed by at least one sealing member 10. In addition to the sealing member 10, a sealing member such as an oil seal other than the sealing member 10 may be used in combination to seal the internal space 22. The number of sealing members 10 that seal the internal space 22 is not particularly limited, nor are the number and type of sealing members particularly limited, and may be appropriately changed depending on the type of power transmission device 14.

[0084] The effects of the sealing member 10 in relation to the features of the power transmission device 14 described above will now be explained.

[0085] Let's consider the case where the internal space 22 is sealed by a spring-loaded seal member using pump force. In this case, the inventors of the present invention have newly recognized that the pump force tends to increase more easily at the location where the first seal member 10-A is located than at the location where the second seal member 10-B is located, and that this makes lubricant leakage more likely. This is thought to be due to the fact that the sliding speed of the first seal member 10-A relative to the first relative rotating body 18 (high-speed rotating body 116A), which is one of the pair of high-speed relative rotating bodies 16-A, is faster than the sliding speed of the second seal member 10-B relative to the first relative rotating body 18 (low-speed rotating body 116B), which is one of the pair of low-speed relative rotating bodies 16-B. In this regard, the present embodiment uses the aforementioned seal member 10-A, which is advantageous in suppressing lubricant leakage caused by pump force between the pair of high-speed relative rotating bodies 16-A. Therefore, by significantly reducing the pumping force at the location where the first sealing member 10-A is positioned, where the pumping force tends to increase, it is advantageous in suppressing lubricant leakage caused by the pumping force.

[0086] The sealing member 10-A in this embodiment satisfies the aforementioned length condition, which is advantageous in increasing the overall contact length L0 of the lip portion 28 with respect to the first relative rotating body 18, as described above. Therefore, by increasing the contact length L0, even if foreign matter gets caught between the lip portion 28 and the first relative rotating body 18, it becomes easier to maintain contact between the lip portion 28 and the first relative rotating body 18 at a position axially offset from the point of foreign matter involvement. This is advantageous in suppressing lubricant leakage caused by foreign matter involvement. In particular, when the reduction mechanism 42 is composed of a gear mechanism 110, wear particles are easily generated in the internal space 22 of the power transmission device 14 due to the meshing of each gear constituting the gear set 112. According to this embodiment, in a power transmission device 14 using a gear mechanism 110 that is prone to generating wear particles, it is effective in suppressing lubricant leakage caused by the involvement of such wear particles.

[0087] The rotating body 116A, which is equipped with the reduction gear rotating shaft 118, may be subjected to radial loads generated inside the reduction gear 12. This occurs, for example, when (1) the reduction gear rotating shaft 118 is the vibrator shaft 50, or (2) the reduction gear rotating shaft 118 is the crankshaft 72. In case (1), a radial load is input from the flexible gear 52 to the vibrator shaft 50 during the process in which the vibrator 48 of the vibrator shaft 50 causes the flexible gear 52 to bend and deform. In case (2), a radial load is input from the oscillating gear 74 to the eccentric portion 70 of the crankshaft 72 during the process in which the oscillating gear 74 is oscillated.

[0088] The inventors of this application have newly recognized that when the rotating body 116A is subjected to a radial load, axial misalignment of the rotating body 116A is likely to occur, and as a result, lubricant leakage is likely to occur at the location where the sealing member 10-A is positioned between the pair of relative rotating bodies 16-A, including the rotating body 116A. This is thought to be because the axial misalignment of the rotating body 116A causes uneven wear on the lip portion 28 of the sealing member 10-A, thereby impairing the sealing performance of the sealing member 10-A. Here, axial misalignment refers to the rotational centerline of the rotating body 116A being shifted radially or to being tilted.

[0089] Here, the sealing member 10-A in this embodiment satisfies the aforementioned length condition, which is advantageous in reducing the contact pressure of the lip portion 28, as described above. Therefore, the reduction in contact pressure makes uneven wear on the lip portion 28 due to axial misalignment of the rotating body 116A less likely, which is advantageous in maintaining the airtightness of the sealing member 10-A. For this reason, even when axial misalignment is likely to occur due to radial load on the rotating body 116A, it is advantageous in suppressing lubricant leakage caused by this.

[0090] The specific example of the reduction gear rotating shaft 118 is not particularly limited and may be other than the vibrator shaft 50 and the crankshaft 72.

[0091] (Eighth Embodiment) Refer to Figure 10. The power transmission device 14 in this embodiment includes only a reduction gear 12, similar to the embodiment in Figure 6. The configuration of the reduction gear 12 is the same as in the embodiment in Figure 6, and its description is omitted.

[0092] The pair of relative rotating bodies 16 include a rotating body 134 that transmits torque to the other rotating body 132 via a torque transmission mechanism 130. In this embodiment, the rotating body 134 includes, for example, a vibrator shaft 50 that serves as an input member, but may also include a crankshaft 72 or the like. In this embodiment, the other rotating body 132 includes a drive shaft 98, but may not include a drive shaft 98.

[0093] In this embodiment, the rotating body 134 receives a radial load when transmitting torque to another rotating body 132. The torque transmission mechanism 130 can also be said to be configured to apply a radial load to the rotating body 134 when transmitting torque between the other rotating body 132 and the rotating body 134. In applying this radial load to the rotating body 134, the torque transmission mechanism 130 in this embodiment is configured using a transmission belt 136. Specifically, the torque transmission mechanism 130 in this embodiment comprises a first pulley 138 that can rotate integrally with the other rotating body 132, a second pulley 140 that can rotate integrally with the rotating body 134, and a transmission belt 136 stretched between the first pulley 138 and the second pulley 140. The transmission belt 136 transmits torque between the first pulley 138 and the second pulley 140.

[0094] In this embodiment, the rotating body 134 that the sealing member 10 contacts is subjected to a radial load when transmitting torque with other rotating bodies 132. In this case, as described above, axial misalignment of the rotating body 134 is likely to occur, and lubricant leakage is likely to occur at the location where the sealing member 10 is positioned between the pair of relative rotating bodies 16, including the rotating body 134.

[0095] In this respect, the sealing member 10 of this embodiment, by satisfying the aforementioned length condition, is advantageous in reducing the contact pressure of the lip portion 28 with respect to the first relative rotating body 18, as described above. Therefore, the reduction in contact pressure makes uneven wear on the lip portion 28 due to axial misalignment of the rotating body 134 less likely, which is advantageous in maintaining the airtightness of the sealing member 10. For this reason, even when axial misalignment is likely to occur due to radial load on the rotating body 134, it is advantageous in suppressing lubricant leakage caused by this.

[0096] Thus, when the rotating body 134 is subjected to a radial load, lubricant leakage is likely to occur due to uneven wear of the sealing member 10 that contacts the rotating body 134. An example of a case where the rotating body 134 is subjected to a radial load is when a power transmission device 14 is incorporated into the joint of a robot. In this case as well, adopting the aforementioned configuration of the sealing member 10 has the advantage of suppressing lubricant leakage caused by axial misalignment of the rotating body 134.

[0097] Furthermore, if the rotating body 134 is prone to misalignment, it is advisable to provide a groove 34 in the contact area 32 of the lip portion 28, as shown in the configuration of Figure 4. By utilizing the groove 34 as a lubricant reservoir, the amount of lubricant present between the first relative rotating body 18 and the lip portion 28 can be increased. This suppresses uneven wear due to misalignment of the rotating body 134 and is advantageous in suppressing lubricant leakage caused by such misalignment.

[0098] The specific example of the torque transmission mechanism 130 for applying a radial load to the rotating body 134 is not particularly limited. To achieve this, the torque transmission mechanism 130 may be configured using, for example, a gear set such as a bevel gear set or a helical gear set that meshes with each other. Furthermore, the rotating body 134 does not need to receive a radial load when transmitting torque with other rotating bodies 132.

[0099] Next, we will explain the transformation forms of each component described so far.

[0100] The specific examples of the reduction mechanism 42 used in the reducer 12 are not particularly limited. If the reduction mechanism 42 is a gear mechanism, the gear mechanism may be an eccentric oscillating type reduction mechanism, a deflection meshing type reduction mechanism, or, for example, a simple planetary gear mechanism, a right-angle gear mechanism, a parallel-axis gear mechanism, etc. Furthermore, the specific type of deflection meshing type reduction mechanism is not particularly limited, and in addition to the cylindrical type as shown in Figure 6, it may be a top hat type, a cup type, etc. The specific type of eccentric oscillating type reduction mechanism is not particularly limited, and may be a center crank type, a distribution type, etc., as mentioned above. Furthermore, the reduction mechanism 42 may be a friction transmission mechanism (traction drive), etc., in addition to a gear mechanism.

[0101] The sealing member 10 to which the features of this disclosure are applied only needs to be placed between at least one pair of relative rotating bodies 16, and does not need to be placed between multiple pairs of relative rotating bodies 16. In this case, the sealing member 10 to which the features of this disclosure are applied can be placed between one pair of relative rotating bodies 16, and other sealing members such as oil seals (for example, spring-loaded sealing members) to which the features of this disclosure are not applied can be placed between the other pairs of relative rotating bodies 16. Alternatively, the sealing member 10 to which the features of this disclosure are applied can be placed only between a pair of high-speed relative rotating bodies 16-A, or between a pair of low-speed relative rotating bodies 16-B.

[0102] The contents of each component described in the embodiments above are illustrative. The abstract technical ideas derived from these should not be interpreted restrictively to the contents of this specification. Many design changes, such as modifications, additions, and deletions, are possible for the contents of each component described in the embodiments. Such modifications are emphasized with the notations "this form" and "embodiment." However, design changes are also permitted for contents without such notations. The hatching applied to the cross-sections in the drawings does not limit the material to which the hatching is applied. The structures and numerical values ​​mentioned in the embodiments and modified forms naturally include those that can be considered identical when considering manufacturing tolerances, etc. Any combination of the above components is also valid. For example, any explanatory items from other embodiments may be combined with an embodiment, and any explanatory items from an embodiment and other modified forms may be combined with a modified form. Components composed of a single member in the description in this specification may be composed of multiple members. Similarly, components composed of multiple members may be composed of a single member. [Explanation of Symbols]

[0103] 10...Seal member, 12...Gear reducer, 14...Power transmission device, 16, 16-A, 16-B...Pair of relative rotating bodies, 16-A...Pair of high-speed relative rotating bodies, 16-B...Pair of low-speed relative rotating bodies, 18...First relative rotating body, 20...Second relative rotating body, 22...Internal space, 24...Outer space, 28...Lip portion, 28a...Corner portion, 28b...Tip surface, 32...Contact area, 34...Groove portion, 42...Reduction mechanism, 48...Vibrator, 50...Vibrator shaft, 72...Crankshaft, 74...Oscillating gear, 118...Gear reducer rotating shaft, 130...Torque transmission mechanism, 134...Rotating body.

Claims

1. A power transmission device equipped with a reduction gear, A pair of relative solids of revolution rotating relative to each other, A sealing member is positioned between the pair of relative rotating bodies to seal the internal space of the power transmission device, The sealing member has a lip portion that contacts the first relative rotating body, which is one of the pair of relative rotating bodies. The lip portion does not have a spring member attached to it that presses the lip portion toward the first relative rotating body. The lip portion includes a corner portion provided at a position radially opposite to the first relative rotating body, A power transmission device in which the axial contact length of the lip portion with the first relative rotating body on the axial side of the corner portion away from the internal space is longer than the axial contact length of the lip portion with the first relative rotating body on the internal space side of the corner portion.

2. The lip portion comprises a tip surface continuous with the corner and a side surface continuous with the corner. The power transmission device according to claim 1, wherein the lip portion is in contact with the first relative rotating body, with respect to only the side surface of the tip surface and the side surface.

3. The lip portion has a tip surface that is continuous with the corner portion, The power transmission device according to claim 1, wherein the axial contact length of the entire lip portion with respect to the first relative rotating body is longer than the axial length of the tip surface when the lip portion is in an undeformed state.

4. The power transmission device according to claim 1, wherein the axial contact length of the entire lip portion with respect to the first relative rotating body is longer than the minimum thickness of the lip portion at the point of contact with the first relative rotating body.

5. The lip portion includes a contact region that includes the entire contact area of ​​the lip portion with respect to the first relative rotating body. The power transmission device according to claim 1, wherein at least one groove is provided in the contact area.

6. The pair of relative rotating bodies includes a pair of high-speed relative rotating bodies that rotate relative to each other at a first relative rotational speed, and a pair of low-speed relative rotating bodies that rotate relative to each other at a second relative rotational speed slower than the first relative rotational speed. The power transmission device according to claim 1, wherein the sealing member is disposed at least between the pair of high-speed relative rotating bodies.

7. The power transmission device according to claim 1, wherein the reduction gear comprises a reduction mechanism configured by a gear mechanism.

8. The aforementioned internal space is filled with a lubricant. The power transmission device according to claim 1, wherein the lubricant contains at least one of Mo, S, Ca, Zn, Ba, Mg, P, C, B, and W.

9. The pair of relative rotating bodies includes a rotating body that transmits torque to other rotating bodies via a torque transmission mechanism. The power transmission device according to claim 1, wherein the rotating body is subjected to a radial load when transmitting torque between itself and the other rotating body.

10. The aforementioned pair of relative rotating bodies includes a rotating body equipped with a reduction gear rotating shaft, The power transmission device according to claim 1, wherein the rotational shaft of the reduction gear is either a crankshaft that oscillates an oscillating gear, or a vibrator shaft that causes a flexible gear to bend and deform.

Images