POWER TRANSMISSION DEVICE

Abstract

A force transmission device (14) is provided which is advantageous for suppressing lubricant leakage caused by a pump force when sealing an interior space (22) with a sealing element (10). The force transmission device (14) comprises: a pair of relative rotators (16) rotating relative to each other; and the sealing element (10) arranged between the pair of relative rotators (16), wherein the sealing element (10) includes a lip section (28) that comes into contact with a first relative rotator (18), which is one of the pair of relative rotators (16), the lip section (28) is not provided with a spring element for pressing the lip section (28) towards the first relative rotator (18), and the lip section (28) includes a first corner section (28a) provided at a position facing the first relative rotator (18) in a radial direction.and a contact length (La) of the lip section (28) with the first relative rotator (18) in an axial direction on a side axially opposite the interior (22) of the first corner section (28a) is greater than a contact length (Lb) of the lip section (28) with the first relative rotator (18) in the axial direction on a side of the interior in the axial direction of the first corner section (28a).

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

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

[0002] This application claims priority from Japanese patent application No. 2024-182206, filed on October 17, 2024, which is incorporated herein in its entirety by reference. Description of the state of the art

[0003] Japanese unexamined patent publication No. 2006-283981 discloses a power transmission device that includes a speed reducer. The power transmission device comprises a pair of relative rotators that rotate relative to each other and a sealing element arranged between the pair of relative rotators. SUMMARY OF THE INVENTION

[0004] In the power transmission device described in Japanese unexamined patent publication No. 2006-283981, a spring-loaded sealing element, in which a spring element is attached to a sealing element, is used as the sealing element. The spring-loaded sealing element can locally deform a lip section by pressing a corner section of the lip section of the sealing element with the spring element against a contact partner, and can seal an interior of the power transmission device by utilizing a pumping force generated between the lip section and the contact partner.

[0005] In a case where the interior is sealed in this way using pumping force, a problem arises because air in an outer chamber of the sealing element, on a side axially opposite the interior, is drawn into the interior by the pumping force. This increases the internal pressure of the interior and likely leads to lubricant leakage due to the pumping force. Lubricant leakage here means that the lubricant trapped in the interior escapes into the outer chamber.

[0006] Therefore, one object of the present disclosure is to provide a force transmission device which is advantageous in suppressing lubricant leakage caused by a pumping force when sealing an interior space with a sealing element.

[0007] According to the present disclosure, a power transmission device is provided which comprises: a speed reducer; a pair of relative rotators which rotate relative to each other;and a sealing element arranged between the pair of relative rotators and sealing an interior of the power transmission device, the sealing element comprising a lip section which comes into contact with a first relative rotator which is one of the pair of relative rotators, the lip section not being provided with a spring element for pressing the lip section towards the first relative rotator, the lip section comprising a corner section provided at a position facing the first relative rotator in a radial direction, and a contact length of the lip section with the first relative rotator in an axial direction on a side axially opposite the interior from the corner section is greater than a contact length of the lip section with the first relative rotator in the axial direction on a side of the interior in the axial direction from the corner section.

[0008] With a power transmission device of the present disclosure it is advantageous to suppress lubricant leakage caused by a pumping force when sealing an interior space with a sealing element. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 is a side section view showing a sealing element in a deformation state according to a first embodiment. Fig. Figure 2 is a side section view showing the sealing element in a non-deformed state according to the first embodiment. Fig. Figure 3A is a side section view showing a sealing element in a deformation state according to a second embodiment, and Fig. 3B is an enlarged view of a part in Fig. 3A. Fig. Figure 4 is a side section view showing a sealing element in a deformation state according to a third embodiment. Fig. Figure 5 is a side section view showing the sealing element in a non-deformed state according to the third embodiment. Fig. Figure 6 is a side section view showing a power transmission device according to a fourth embodiment. Fig. Figure 7 is a side section view showing a power transmission device according to a fifth embodiment. Fig. Figure 8 is a side section view showing a power transmission device according to a sixth embodiment. Fig. Figure 9 is a side section view showing a power transmission device according to a seventh embodiment. Fig. Figure 10 is a side section view showing part of a power transmission device according to an eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments for implementing a power transmission device of the present disclosure. The same or equivalent elements are designated by the same reference numerals, and any duplicate description thereof is omitted. In each drawing, components are, where necessary, omitted, enlarged, or reduced in size to simplify the description. The drawings are to be viewed in alignment with the orientation of the reference numerals.

[0010] (First embodiment) On Fig. Reference is made to Figure 1. First, a sealing element 10 according to a first embodiment is described. The sealing element 10 is used for a power transmission device 14, which includes a speed reducer 12. The power transmission device 14 includes a pair of relative rotators 16 that rotate relative to each other, in addition to the sealing element 10. Details of the power transmission device 14 are described below. Hereinafter, a direction along a centerline of rotation (not shown) when the pair of relative rotators 16 rotates relative to each other is referred to as an axial direction, and a radial direction and a circumferential direction with respect to the centerline of rotation are simply referred to as a radial direction and a circumferential direction, respectively.

[0011] The pair of relative rotators 16 comprises a first relative rotator 18, which is one of the pair of relative rotators 16, and a second relative rotator 20, which is the other of the pair of relative rotators 16. The first relative rotator 18 has a lip contact surface 18a with which a lip section 28 of the sealing element 10 comes into contact. The second relative rotator 20 has a fixed surface 20a to which the sealing element 10 is attached. In the present embodiment, the first relative rotator 18 is located inside the second relative rotator 20 in the radial direction, but may be located outside the second relative rotator 20 in the radial direction.

[0012] The sealing element 10 is arranged between the pair of relative rotators 16 and is used to seal an interior 22 of the power transmission device 14. The side of interior 22 (right side of the plane in) is shown below. Fig. 1) of the sealing element 10 in the axial direction is designated as an axial inner side, and a side axially opposite the interior 22 (left side of the plane in Fig. 1) is referred to as an axial outer surface. The sealing element 10 separates an outer space 24, which is located on the axial outer surface of the sealing element 10, and the inner space 22.

[0013] The sealing element 10 comprises a main body 26 and the lip section 28 (first lip section) provided on the main body 26. The main body 26 is press-fitted to the fixed surface 20a of the second relative rotator 20. Furthermore, the sealing element 10 may optionally include a dust lip section 30 (second lip section) projecting from the lip section 28.

[0014] In the present embodiment, the main body 26 is formed from an elastic material, such as rubber. Furthermore, the main body 26 can be formed from a combination of a metal ring and an elastic material, or from a metal ring alone. The lip section 28 is formed from an elastic material, such as rubber. In the present embodiment, the lip section 28 is formed from an elastic material common to the main body 26.

[0015] The main body 26 in the present embodiment has an L-shape in a cross-section cut along the axial direction, but the specific shape is not particularly restricted. The main body 26 in the present embodiment includes an axial extension section 26a extending in the axial direction and attached to the second relative rotator 20, and a radial extension section 26b extending radially from an end section on the axial outer side of the axial extension section 26a to the side of the first relative rotator 18.

[0016] On Fig. 1 and Fig. Reference is made to 2. When the lip section 28 of the sealing element 10 is in contact with the first relative rotator 18, the lip section 28 is in a deformation state in which the lip section 28 is deformed by the contact with the first relative rotator 18 (see Fig. 1) In contrast, if the lip section 28 is not in contact with the first relative rotator 18, the lip section 28 is in a non-deformation state in which the lip section 28 is not deformed (see Fig. 2) The sealing element 10 is assumed to be in a state where it is attached to the second relative rotator 20, regardless of whether the lip section 28 is in the deformation state or the non-deformation state. The non-deformation state is also a state that can be assumed when the sealing element 10 is in the state where it is attached to the second relative rotator 20 and the lip section 28 is disengaged from contact with the first relative rotator 18.

[0017] The lip section 28 is used to prevent lubricant trapped in the interior 22 from escaping. The lip section 28 extends from a section of the main body 26 on the axial outside to the axial inside. In the non-deformed state, the lip section 28 extends entirely toward the axial inside to approach the side of the first relative rotator 18 in the radial direction. In the deformed state, a tip end face of the lip section 28 is elastically bent more in the radial direction than in the non-deformed state in a direction opposite to the first relative rotator 18. When the lip section 28 is in the deformed state, a compressive force F1 acts, pressing the lip section 28 radially against the first relative rotator 18.The compressive force F1 acts as a repulsive force caused by the elastic bending deformation of the lip section 28.

[0018] The lip section 28 includes a first corner section 28a, which is provided at a position facing the first relative rotator 18 in the radial direction, a tip end surface 28b extending through to the first corner section 28a, a first side surface 28c extending through to the first corner section 28a, a second corner section 28d, which is provided on a side opposite the first corner section 28a in the radial direction at the tip end surface 28b, and a second side surface 28e extending through to the second corner section 28d.

[0019] In the present description, the first corner section 28a differs from its usual meaning and refers to a section that is radially closest to the side of the first relative rotator 18, which is a projection towards the side of the first relative rotator 18 in the radial direction of the lip section 28 in a cross-sectional area along the axial direction, when the lip section 28 is in the non-deformed state in the axial direction. The first corner section 28a can be described as a section where an imaginary line, parallel to the axial direction and coming from the side of the first relative rotator 18, is in radial contact with the lip section 28 in the cross-sectional area along the axial direction.When considering the first corner section 28a in this way, the presence of another lip section (for example, the dust lip section 30 described below) extending from the lip section 28 is not taken into account. The first corner section 28a is formed by a portion of the first side surface 28c, which extends radially from a section of the lip section 28 that is closest in the radial direction to the side of the first relative rotator 18 to the side of the second relative rotator 20 on the side axially opposite the interior 22, and by a portion of the tip end surface 28b, which extends radially from the section to the side of the second relative rotator 20 on the side of the interior 22 in the axial direction.In the present embodiment, the first corner section 28a is configured with a pointed section located radially closest to the side of the first relative rotator 18. This pointed section is a pointed projection on the side of the first relative rotator 18 in the radial direction when the lip section 28 is in the non-deformed state. Furthermore, the first corner section 28a can be configured with a section located radially closest to the side of the first relative rotator 18. This curved projection is a curved projection on the side of the first relative rotator 18 in the radial direction when the lip section 28 is in the non-deformed state.

[0020] The tip end surface 28b faces the side of the interior 22 in the axial direction and is located at the furthest axial inner side of the lip section 28. In the present embodiment, the tip end surface 28b is designed such that it is perpendicular to the lip contact surface 18a in the cross-sectional area along the axial direction when the lip section 28 is in the deformation state. Here, "perpendicular" includes not only a case where the angle is geometrically and strictly perpendicular to the lip contact surface 18a, but also a case where the angle is substantially perpendicular to the lip contact surface 18a. "Substantially perpendicular" here includes a case where the angle lies within a range of ±10° from a position that is, for example, strictly perpendicular to the lip contact surface 18a.The first side surface 28c is located at a position facing the first relative rotator 18 in the radial direction, as with the first corner section 28a. The second side surface 28e is a surface on a side opposite the first side surface 28c in the radial direction.

[0021] The dust lip section 30 is designed to prevent dust from entering the outer chamber 24 towards the side of the inner chamber 22. The dust lip section 30 extends from the lip section 28 towards the axial outer surface and comes into contact with the lip contact surface 18a of the first relative rotator 18 via elastic deformation.

[0022] A spring element that presses the lip section 28 towards the first relative rotator 18 is not attached to the lip section 28. The spring element is, for example, a ring spring that is continuous in the circumferential direction in an endless form. The spring element is a separate body from the lip section 28 and is attached to the second side surface 28e of the lip section 28.

[0023] The contact length of the entire lip section 28 with the first relative rotator 18 in the axial direction is referred to as the contact length L0. The contact length in the axial direction here refers to the axial length of the contact section of the lip section 28 with the first relative rotator 18. When considering the contact length L0 of the entire lip section 28, as described in Fig. Figure 4 shows a case where the lip section 28 is in contact with the first relative rotator 18 at several contact sections spaced apart in the axial direction, using a total value of the axial lengths of the several contact sections. Fig. Figure 4, for example, shows an instance where the lip section 28 is in contact with the first relative rotator 18 at four contact sections, and the contact lengths of the individual contact sections are L0(1) to L0(4). In this case, the contact length L0 of the entire lip section 28 is the sum of the individual contact lengths L0(1) to L0(4). For example, when considering the contact length L0 of the entire lip section 28, the axial length of the contact section with the first relative rotator 18 of another lip section, such as the dust lip section 30 projecting from the lip section 28, is not taken into account. The concept described here is the same for an outer contact length La and an inner contact length Lb, which are described next.

[0024] The contact length of the lip section 28 with the first relative rotator 18 in the axial direction on the axial outside of the first corner section 28a of the sealing element 10 is referred to as the outer contact length La, and the contact length of the lip section 28 with the first relative rotator 18 on the axial inside of the first corner section 28a is referred to as the inner contact length Lb. The outer contact length La is also a contact length of the entire first side surface 28c with the first relative rotator 18. The inner contact length Lb is also a contact length of the entire tip end surface 28b with the first relative rotator 18. The contact length L0 of the entire lip section 28 is the sum of the outer contact length La of the lip section 28 and the inner contact length Lb of the lip section 28.

[0025] In the present embodiment, the outer contact length La of the lip section 28 fulfills a length condition where the outer contact length La is greater than the inner contact length Lb. To fulfill the length condition, there are cases where (1) the inner contact length Lb of the lip section 28 is zero and (2) the inner contact length Lb of the lip section 28 is greater than zero. In the embodiment in Fig. Equation 1 is a case of (1). In this case, the length condition is satisfied regardless of the size of the outer contact length La of the lip section 28. In this case, the contact length L0 of the entire lip section 28 = the outer contact length La of the lip section 28. In this case, a contact mode is provided in which, of the tip end face 28b and the first side face 28c, only the first side face 28c of the lip section 28 comes into contact with the first relative rotator 18, and the tip end face 28b does not come into contact with the first relative rotator 18 (hereinafter referred to as a surface contact mode).

[0026] Fig. 3A and Fig. Figure 3B represents the sealing element 10 according to a second embodiment, which is a case of (2) described above. Fig. In 3B, the lip section 28 in a deformation state is represented by a solid line, and a portion of the lip section 28 in a non-deformation state is represented by a two-dot dashed line. In the case of (2) described above, a contact mode (hereinafter referred to as a corner contact mode) is established in which a section having the first corner section 28a of the lip section 28 is squeezed and deformed, causing both the tip end face 28b and the first side face 28c to come into contact with the first relative rotator 18. In this case, the first corner section 28a of the lip section 28 has a flat shape in a cross-sectional area along the axial direction, extending along the axial direction together with a portion of the tip end face 28b and the first side face 28c of the lip section 28.That is, when the lip section 28 is in the deformation state, a section containing the first corner section 28a of the lip section 28 is not obviously a projection towards the side of the first relative rotator 18 in the radial direction. Fig. 3B is, for the sake of simplicity, a position of the first corner section 28a of the lip section 28 in the deformation state, marked with a reference symbol.

[0027] In (1) above, the advantage of fulfilling the length condition described above by making the inner contact length Lb of lip section 28 zero is described, i.e., the advantage of the surface contact mode. In a case where the inner contact length Lb of lip section 28 is greater than zero, the advantage described in (1) is not present. Fig. 3A and Fig. The corner contact mode shown in Figure 3B is established. In this corner contact mode, means for increasing the contact length L0 of the entire lip section 28 are investigated. A first means is assumed, in which the bending deformation of the lip section 28 is increased during the installation process of the sealing element 10, and the first side surface 28c of the lip section 28 is strongly deformed to conform to the lip contact surface 18a of the first relative rotator 18. Furthermore, a second means is assumed, in which a compressive force is exerted on the lip section 28 by pressing it against the first relative rotator 18 using a spring element, thereby increasing the crush deformation of a section containing the first corner section 28a of the lip section 28.

[0028] In a case where the corner contact mode is established, if the bending deformation of the lip section 28 is increased by using the first means, the tip end face 28b of the lip section 28 cannot come into contact with the first relative rotator 18, and the corner contact mode cannot be maintained. Therefore, in the corner contact mode, it is not realistic to use the first means to increase the contact length L0 of the entire lip section 28. Furthermore, in the present embodiment, the spring element is not attached to the lip section 28 of the sealing element 10. Therefore, the second means cannot be used. Thus, in a case where the corner contact mode is established, neither the first nor the second means can be used, and there is also a limit to increasing the contact length L0 of the entire lip section 28.

[0029] On the other hand, in the case of surface contact mode, it is not necessary to bring the tip end surface 28b of the lip section 28 into contact with the first relative rotator 18, as is the case in the corner contact mode. Therefore, in this case, the bending deformation amount of the lip section 28 can be slightly increased by using the first means, and accordingly, the contact length L0 of the entire lip section 28 can be slightly increased. As a result, the contact pressure of the lip section 28 to the first relative rotator 18 can be slightly reduced compared to the case of corner contact mode. Here, contact pressure refers to the force acting on a contact section of the lip section 28 with a contact partner per unit area.

[0030] Next, as described in (2) above, in a case where the inner contact length Lb of the lip section 28 is greater than zero, i.e., in the case of the corner contact mode, the advantage of fulfilling the length condition described above is described. In this case, the contact length L0 of the entire lip section 28 can be increased compared to a case where the outer contact length La of the lip section 28 is equal to the inner contact length Lb. Therefore, the contact pressure of the lip section 28 with the first relative rotator 18 can actually be reduced compared to a case where the outer contact length La is the same as the inner contact length Lb.

[0031] The above is summarized. To satisfy the length condition, a case where the inner contact length Lb of the lip section 28 is zero (a case of the surface contact mode), as in (1), is examined. In this case, the contact length L0 of the entire lip section 28 can be slightly increased compared to a case where the inner contact length Lb is greater than zero (in the case of the corner contact mode), and accordingly, the contact pressure of the lip section 28 with the first relative rotator 18 can be slightly reduced. In this case, compared to the case of the corner contact mode, it is possible to reduce the difficulty of increasing the contact length L0 of the entire lip section 28 and to reduce the difficulty of achieving a reduction in the contact pressure of the lip section 28.

[0032] Next, to satisfy the length condition, a case where the inner contact length Lb of lip section 28 is greater than zero, as in (2), is considered. In this case, compared to a case where the outer contact length La is equal to the inner contact length Lb, the contact length L0 of the entire lip section 28 can actually be increased, and accordingly, the contact pressure of the lip section 28 with the first relative rotator 18 can actually be reduced.

[0033] To satisfy the length condition, in each of the cases of (1) and (2) it can be said that it is advantageous to make the contact length L0 of the entire lip section 28 larger than in a specific case and to reduce the contact pressure of the lip section 28. The specific case here is one in which (1) the inner contact length Lb is greater than zero (a case of corner contact mode) and (2) the outer contact length La is the same as the inner contact length Lb.

[0034] The effect of the power transmission device 14, which uses the sealing element 10 described above, is described.

[0035] (A) It is known that the pumping force can be reduced by reducing the contact pressure acting on the contact section of the lip section 28 of the sealing element 10 with the contact partner. In the present embodiment, the sealing element 10 does not include a spring element attached to the lip section 28. Therefore, the contact pressure of the lip section 28 with the first relative rotator 18, which serves as a contact partner, can indeed be reduced compared to a spring-loaded sealing element. Furthermore, as described above, it is advantageous to reduce the contact pressure of the lip section 28 with the first relative rotator 18 by fulfilling the length condition described above. These factors are advantageous for significantly reducing the pumping force generated between the first relative rotator 18 and the lip section 28.The interior 22 is sealed primarily by applying the pressure force F1 through the lip section 28, without relying on the pump force. Therefore, an increase in the internal pressure of the interior 22 due to the pump force can be suppressed, which is advantageous for preventing lubricant leakage caused by the pump force.

[0036] (B) In a case where the spring-loaded sealing element is used, the contact pressure at the lip section 28 becomes extremely high due to the compressive force of the spring element. Consequently, when the power transmission device 14 performs high acceleration or deceleration operation, the lip section 28 is twisted relative to the first relative rotator 18, and thus a problem arises in that lubricant leakage is likely to occur. In this respect, according to the present embodiment as described above, it is advantageous to reduce the contact pressure of the lip section 28 with the first relative rotator 18.Therefore, when the power transmission device 14 performs high acceleration or deceleration operation, the lip section 28 is less likely to be twisted with respect to the first relative rotator 18, which is advantageous in suppressing lubricant leakage caused by the twisting.

[0037] (C) In the sealing element 10 of the present embodiment, only the first side surface 28c is in contact with the first relative rotator 18, and a surface contact condition can be provided as described above. Therefore, the bending deformation amount of the lip section 28 is increased compared to the case of a corner contact condition. In this way, the first side surface 28c of the lip section 28 is slightly deformed to follow the lip contact surface 18a of the first relative rotator 18, and accordingly, the contact length L0 of the entire lip section 28 can be slightly increased. Therefore, compared to the spring-loaded sealing element, the contact pressure of the lip section 28 with the first relative rotator 18 can be slightly reduced, which is advantageous for significantly reducing the pumping force generated between the first relative rotator 18 and the lip section 28.As a result, an increase in the internal pressure of the interior 22 due to the pumping force can be significantly suppressed, which is particularly advantageous for suppressing the lubricant leakage caused by the pumping force.

[0038] Next, other features of the sealing element 10 will be described. Fig. Reference is made to Section 2. An axial length L28b of the tip end face 28b of the lip section 28 is assumed when the lip section 28 is in a non-deforming state. The axial length L28b is a length in the axial direction from the first corner section 28a of the lip section 28 to a section of the tip end face 28b that is the most axially inward-facing section when the lip section 28 is in the non-deforming state. The contact length L0 may preferably be greater than the axial length L28b. The contact length L0 may further preferably be 2 times or more than the axial length L28b. An upper limit for the contact length L0 with respect to the axial length L28b is not particularly restricted and may, for example, be 20 times or less than the axial length L28b or may be reasonably adjusted within a realistic range during manufacturing.

[0039] (D) Accordingly, compared to the case where the contact length L0 is the axial length L28b or greater, the contact pressure of the lip section 28 with the first relative rotator 18 can be significantly reduced, and the pumping force described above can be significantly reduced. As a result, an increase in the internal pressure of the interior 22 due to the pumping force can be significantly suppressed, which is particularly advantageous in suppressing lubricant leakage caused by an increase in internal pressure. The contact length L0 can be equal to or less than the axial length L28b.

[0040] A minimum thickness T of the lip section 28 is assumed at a contact section of the lip section 28 with the first relative rotator 18. The minimum thickness T refers to a minimum thickness of the lip section 28 in the radial direction at a section that overlaps the contact section of the lip section 28 with the first relative rotator 18 in the radial direction. When considering the minimum thickness T, the thickness of the lip section 28 at a non-contact section of the lip section 28 with the first relative rotator 18 is not considered, as shown in Fig. 4 shown. The non-contact section of the lip section 28 refers here, for example, to a section that overlaps a groove section 34 in the radial direction, as in Fig. 4 shown. In the embodiment shown Fig. 2 the minimum thickness T will be obtained on a section that overlaps the first corner section 28a of the lip section 28 in the radial direction, but the minimum thickness T can be obtained on a section that differs from the above.

[0041] In this case, the contact length L0 of the entire lip section 28 can preferably be greater than the minimum thickness T. An upper limit for the contact length L0 is not particularly restricted with respect to the minimum thickness T and can, for example, be 10 times or less of the minimum thickness T, or can be appropriately set within a realistic range during manufacturing.

[0042] (E) Accordingly, the contact pressure of the lip section 28 against the first relative rotator 18 can be significantly reduced compared to a case where the contact length L0 is equal to or less than the minimum thickness T, and the pumping force described above can be significantly reduced. As a result, an increase in the internal pressure of the interior 22 due to the pumping force can be significantly suppressed, which is particularly advantageous in suppressing lubricant leakage caused by an increase in internal pressure. The contact length L0 can be equal to or less than the minimum thickness T.

[0043] The lubricant enclosed in the interior 22 can contain at least one type of Mo (molybdenum), S (sulfur), Ca (calcium), Zn (zinc), Ba (barium), Mg (magnesium), P (phosphorus), C (carbon), B (boron), and W (tungsten). The lubricant can, for example, be a general-purpose grease containing at least one of the above.

[0044] (F) In a case where such a lubricant is used, it is known that a deposit is generated due to heat generation. If the deposit is generated at the contact section of the lip section 28 with the first relative rotator 18 due to heat generation, a problem arises in that lubricant leakage is likely to occur due to the entrapment of the deposit between the contact section of the lip section 28 and the first relative rotator 18. In this respect, according to the present embodiment as described above, it is advantageous to reduce the contact pressure of the lip section 28 with the first relative rotator 18. Therefore, reducing the contact pressure is advantageous in suppressing heat generation at the contact section of the lip section 28 with the first relative rotator 18 and in suppressing the generation of the deposit caused by the heat generation.Consequently, even in a case where the lubricant is used that can generate the precipitate due to heat generation, it is advantageous in suppressing the lubricant leakage caused by the inclusion of the precipitate.

[0045] One type of lubricant is not particularly restricted, and the lubricant does not need to contain the various elements described above.

[0046] (Third embodiment) Other embodiments are described next. In subsequent embodiments (including the second embodiment), the same content as that of the first embodiment can be applied to the components described in the first embodiment that are not described below.

[0047] On Fig. 4 and Fig. Reference is made to section 5. The lip section 28 of the sealing element 10 includes a contact area 32, which comprises the entire contact area of ​​the lip section 28 with the first relative rotator 18. The contact area 32 extends in an axial direction from an inner end position on the axial inside to an outer end position on the axial outside over the entire contact area of ​​the lip section 28 with the first relative rotator 18. The contact area 32 is located on the first side surface 28c of the lip section 28 in this axial direction.

[0048] At least one groove section 34 is provided in the contact area 32. Although in the present embodiment several (in particular three) groove sections 34 are provided in the contact area 32, the number of groove sections 34 is not particularly limited and can be one, two, four, or more. A lubricant (not shown), such as grease, is applied to the contact area 32. The groove section 34 acts as a lubricant reservoir for storing the lubricant. The lubricant can be the same as the lubricant enclosed in the interior 22 or different from it.

[0049] The effects relating to the above features are described. A lubricating film is formed by a lubricant at a contact section of the lip section 28 with the first relative rotator 18. If the lubricating film is interrupted and lubrication failure occurs at the contact section, a problem arises in that lubricant leakage is likely to occur. In this respect, the groove section 34 is provided in the contact area 32 of the lip section 28 in the present embodiment. Therefore, by using the groove section 34 of the lip section 28 as a lubricant reservoir, it is possible to suppress lubrication failure at the contact section of the lip section 28 with the first relative rotator 18. Consequently, it is advantageous in suppressing lubricant leakage caused by the lubrication failure.

[0050] According to the present embodiment, foreign matter passing between the lip section 28 of the sealing element 10 and the first relative rotator 18 can be trapped in the groove section 34. Accordingly, it is possible to suppress the inclusion of foreign matter (in particular the abrasive powder to be described below) between the contact section of the lip section 28 and the first relative rotator 18, and this is advantageous in suppressing the lubricant leakage caused by the inclusion.

[0051] In a case where the starting frequency of the power transmission device 14 is high, or in a case where the power transmission device 14 is used for forward and reverse operation, the sliding speed of the sealing element 10 on the lip section 28 with respect to the first relative rotator 18 is slowed down or becomes zero, so that a lubrication condition likely to cause lubrication failure in boundary lubrication is likely to occur. According to the present embodiment, even in a case where such a lubrication condition likely to cause lubrication failure is likely to occur, it is advantageous to suppress the lubricant leakage caused by the lubrication failure by using the groove section 34 of the lip section 28 as the lubricant reservoir.

[0052] Furthermore, in the present embodiment, the power transmission device 14 also includes the components described in (A) to (F) above and can produce the effects corresponding to the description thereof.

[0053] Furthermore, in a case where the groove section 34 is provided on the lip section 28 as in the present embodiment, a lubricant with an NLGI consistency number of No. 2 to No. 6 can be applied to the contact area 32 of the lip section 28. The hard lubricant with a consistency number of No. 2 to No. 6 has poor flow properties and is likely to cause lubrication failure. According to the present embodiment, even in a case where such a lubricant, which is likely to cause lubrication failure, is used, the groove section 34 of the lip section 28 is used as a lubricant reservoir, so it is advantageous to suppress lubricant leakage caused by the lubrication failure.

[0054] On Fig. Reference is made to section 5. When the lip section 28 is in a non-deforming state, at least a portion of at least one groove section 34 can be arranged on the side of the first relative rotator 18 in the radial direction from the lip contact surface 18a of the first relative rotator 18. In the present embodiment, an entirety of at least one groove section 34 is arranged on the side of the first relative rotator 18 in the radial direction from the lip contact surface 18a of the first relative rotator 18. To satisfy this condition, at least two of the groove sections 34 can be arranged on the side of the first relative rotator 18 in the radial direction from the lip contact surface 18a of the first relative rotator 18.Accordingly, the bending deformation amount of the lip section 28 can be increased when the lip section 28 is in a deformation state, compared to a case where the condition is not met. As a result, the contact length L0 of the entire lip section 28 can be slightly increased, and the contact pressure of the lip section 28 can be reduced. In this way, it is particularly advantageous to suppress an increase in the internal pressure of the interior 22 caused by the pumping force.

[0055] Next, details of the power transmission device 14 are described. Here, the power transmission device 14 according to the fourth to seventh embodiments is described. Individual features of the power transmission device 14 according to these embodiments are described below, followed by features relating to the sealing element 10 described above. Furthermore, the content described for the power transmission device 14 according to these embodiments can be applied to the power transmission devices 14 of the first to third embodiments.

[0056] (Fourth embodiment) On Fig. Reference is made to Section 6. The power transmission device 14 in the present embodiment comprises only the speed reducer 12. The speed reducer 12 is capable of driving a driven component (not shown) by reducing the input rotation and outputting the rotation. Rotation is introduced into the speed reducer 12 from a drive machine (not shown), such as a motor or a machine. The driven component is, for example, at least one part of various machines, such as (1) an industrial machine, such as a machine tool and a construction machine, (2) a robot, such as an industrial robot and a service robot, (3) a transport machine, such as a conveyor, and (4) a vehicle.

[0057] The speed reducer 12 comprises a reduction mechanism 42, a speed reducer housing 44 in which the reduction mechanism 42 is arranged inside, and a counter-drive side element 46, at least one part of which is provided on a counter-drive side in the axial direction with respect to the reduction mechanism 42 and which is rotatable about a rotation centerline Ca with respect to the speed reducer housing 44.

[0058] The speed reducer 12 in the present embodiment uses a bending-engagement reduction mechanism as the reduction mechanism 42. The speed reducer 12, which employs this mechanism, includes a shaft generator shaft 50 having a shaft generator 48, a bending gear 52 which is bent and deformed by the shaft generator 48, and engagement gears 54A and 54B which engage with the bending gear 52. The shaft generator shaft 50 in the present embodiment functions as a drive element into which rotation is introduced directly or indirectly from the outside. The bending gear 52 and the engagement gears 54A and 54B function as the reduction mechanism 42, which reduces the rotation introduced by the drive element. One of the bending gear 52 or the engagement gears 54A and 54B is an external gear, and the other is an internal gear.An example is described here in which the bending gear 52 is an external gear and the meshing gears 54A and 54B are internal gears. In this embodiment, the counter-drive element 46 acts as an output element that extracts the slowed rotation from the reduction mechanism 42 and outputs the rotation to the driven component. The output element can be the speed reducer housing 44 instead of the counter-drive element 46.

[0059] The wave generator shaft 50 includes, in addition to the wave generator 48, a wave section 58, which is provided on both sides of the wave generator 48 in the axial direction. A cross-section of an outer circumferential section of the wave generator 48 has an elliptical shape. A cross-section of an outer circumferential section of the wave section 58 has a circular shape. The cross-sectional shape here refers to a shape in a cross-section perpendicular to the axial direction of the wave generator 48. Here, "elliptical" is not limited to an ellipse in a geometrically strict sense and also includes an approximately elliptical shape.

[0060] The bending gear 52 is a tubular element that exhibits flexibility to be bent and deformed by the shaft generator 48 via a shaft generator bearing 60. The engagement gears 54A and 54B possess sufficient stiffness to prevent them from bending and deforming after rotation of the shaft generator 48. In the present embodiment, the engagement gears 54A and 54B comprise a first engagement gear 54A that engages teeth on a drive-side section of the bending gear 52, and a second engagement gear 54B that engages teeth on a counter-drive-side section of the bending gear 52. The first meshing gear 54A has a number of teeth (for example, 102) that differs from the number of teeth (for example, 100) of the bending gear 52, and the second meshing gear 54B has a number of teeth that is the same number as the number of teeth of the bending gear 52.

[0061] In the present embodiment, the speed reducer housing 44 also serves as the first engagement gear 54A. The speed reducer housing 44 in the present embodiment is configured with several housing elements that are coupled by bolts or the like. A bearing 62 is arranged between the speed reducer housing 44 and the shaft section 58 of the generator shaft 50. The counter-drive element 46 in the present embodiment also serves as the second engagement gear 54B. A bearing 64 is arranged between the counter-drive element 46 and the shaft section 58 of the generator shaft 50. The counter-drive element 46 in the present embodiment is configured with several elements that are coupled by means of a bolt or the like. A main bearing 66 is arranged between the speed reducer housing 44 and the counter-drive element 46.

[0062] An example of the operation of the power transmission device 14 according to the present embodiment is described. In the present embodiment, when the shaft generator shaft 50, which serves as a drive element, is rotated, the bending gear 52 is bent and deformed to form an elliptical shape corresponding to the shape of the shaft generator 48 of the shaft generator shaft 50. In a case where the bending gear 52 is bent and deformed in such a manner, the engagement position between the bending gear 52 and the engagement gears 54A and 54B changes in one direction of rotation of the shaft generator 48. At this point, each time the engagement position between the bending gear 52 and the first engagement gear 54A with different numbers of teeth rotates, the engagement teeth gradually shift in the circumferential direction.Consequently, in the present embodiment, the bending gear 52 is rotated, and its axial rotational component is extracted by the counter-drive-side element 46, which serves as an output element. In the present embodiment, the bending gear 52 and the second engagement gear 54B have the same number of teeth and are thus synchronized with each other. The axial rotational component of the bending gear 52 is extracted by the counter-drive-side element 46, which serves as an output element, through the second engagement gear 54B, which is synchronized with the bending gear 52. At this point, the output rotation, slowed down by a reduction ratio corresponding to the difference in the number of teeth between the bending gear 52 and the first engagement gear 54A, is extracted relative to the input rotation introduced into the shaft generator shaft 50.

[0063] (Fifth embodiment) On Fig. Reference is made to section 7. The speed reducer 12 in the embodiments in Fig. Figures 7 to 9 employ an eccentrically oscillating reduction mechanism as the reduction mechanism 42. In particular, the speed reducer 12 in the present embodiment uses an eccentrically oscillating reduction mechanism of the center crank type. The speed reducer 12 employing this mechanism includes a crankshaft 72 having an eccentric section 70, an oscillating gear 74 that oscillates by means of the eccentric section 70, and a meshing gear 76 that engages with the oscillating gear 74. The crankshaft 72 in the present embodiment acts as a drive element. 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.An example is described here in which the oscillating gear 74 is an external gear and the meshing gear 76 is an internal gear. In this embodiment, the counter-drive element 46 functions as an output element.

[0064] The counter-drive element 46 in the present embodiment comprises a flange section 46a, which is provided on the counter-drive side with respect to the reduction mechanism 42, and a shaft section 46b, which is provided on the counter-drive side with respect to the flange section 46a and has a diameter that is smaller than the diameter of the flange section 46a. A sleeve 78 is attached to the shaft section 46b of the present embodiment such that it is rotatably integral with the shaft section 46b.

[0065] In the present embodiment, the crankshaft 72 is positioned on the axis of rotation Ca. The crankshaft 72 includes at least one (here two) eccentric section 70. The eccentric section 70 has a circular shape that is eccentric with respect to an axis of rotation C72 of the crankshaft 72. In the present embodiment, the eccentric section 70 is provided separately from the other section of the crankshaft 72. However, as in the Fig. 8 and Fig. In the embodiments shown in Figure 9, the eccentric section 70 is integrally provided with the other section of the crankshaft 72 by the same element. The oscillating gear 74 is designed to correspond to the eccentric section 70 and is supported by the corresponding eccentric section 70 via an eccentric bearing 80.

[0066] In the present embodiment, the engagement gear 76 is provided on an inner circumferential section of the speed reducer housing 44. The engagement gear 76 comprises a gear body 76a, which also serves as the speed reducer housing 44, and a toothed section 76b provided on the gear body 76a. In the present embodiment, the toothed section 76b is configured with a roller 76d, which is designed to rotate freely on a bearing pin 76c supported by a gear body 76s. Furthermore, as in the embodiment in Fig. 8, the tooth section 76b may be configured with the bearing pin 76c, and the meshing gear 76 need not include the roller 76d. Furthermore, the tooth section 76b of the meshing gear 76 may be integrally formed with the same element as the main gear body 76a, as in the embodiment shown in Fig. 9 be provided.

[0067] In the present embodiment, a pin 82, which passes through the oscillating gear 74, projects from the counter-drive-side element 46. The pin 82 bears directly or indirectly against the oscillating gear 74 and can synchronize the axial rotational component of the oscillating gear 74 with the counter-drive-side element 46.

[0068] An example of the operation of the power transmission device 14 according to the present embodiment is described. When the crankshaft 72, which serves as a drive element, is rotated, the oscillating gear 74 oscillates by means of the eccentric section 70. As the oscillating gear 74 oscillates, the engagement position between the oscillating gear 74 and the engagement gear 76 changes in the circumferential direction. Accordingly, each time the crankshaft 72 is rotated, the oscillating gear 74 is rotated, and its axial rotational component is extracted by the counter-drive element 46, which serves as an output element, via the pin 82. At this point, the output rotation, slowed by a reduction ratio corresponding to the difference in the number of teeth between the oscillating gear 74 and the meshing gear 76, is extracted in relation to the input rotation introduced into the crankshaft 72.

[0069] (Sixth embodiment) On Fig. Reference is made to section 8. In the present embodiment, the power transmission device 14 comprises, in addition to the speed reducer 12, a drive motor 90, an adapter 92 that couples the drive motor 90 and the speed reducer 12, and a disk-shaped driven component 94 that is driven by the speed reducer 12. In this way, the power transmission device 14 can comprise only the speed reducer 12 or, in addition to the speed reducer 12, it can comprise one or more driven components 94 driven by the drive motor 90, the adapter 92, and the driven component 94.

[0070] The drive unit 90 in the present embodiment is a motor. The drive unit 90 comprises a drive unit housing 96 and a drive shaft 98 for outputting rotation generated within the drive unit 90. The drive unit housing 96 is coupled to the speed reducer housing 44 via the adapter 92.

[0071] The speed reducer 12 in the present embodiment uses as the reduction mechanism 42 the eccentrically oscillating reduction mechanism of the center crank type as in the embodiment in Fig. 7. In the present embodiment, the crankshaft 72 of the speed reducer 12 is coupled to the drive shaft 98 in such a way that it is integrally rotatable by the use of a key or the like. The crankshaft 72 of the present embodiment includes three eccentric sections 70. The speed reducer 12 of the present embodiment includes a support 100, which is provided on a drive side with respect to the reduction mechanism 42. The support 100 is integrally coupled to the counter-drive side element 46 by the pin 82. The main bearing 66 is arranged between the speed reducer housing 44 and the counter-drive side element 46 and is also arranged between the speed reducer housing 44 and the support 100.

[0072] (Seventh embodiment) On Fig. Reference is made to 9. The power transmission device 14 in the present embodiment also includes the drive motor 90, the adapter 92 and the driven component 94 in addition to the speed reducer 12, as in the embodiment in Fig. 8.

[0073] The speed reducer 12 in the present embodiment uses a distributed eccentrically oscillating reduction mechanism as the reduction mechanism 42. Several (only one is shown here) crankshafts 72 of the speed reducer 12, which uses the reduction mechanism 42, are provided at positions offset radially with respect to the centerline Ca. The crankshaft gear 102 is designed to be integrally rotatable with each of the several crankshafts 72. The crankshaft gear 102 engages with a drive pinion 106, which is provided on a countershaft 104. The countershaft 104 is coupled to the drive shaft 98 in such a way that it is integrally rotatable by the use of a key or the like. Rotation is introduced from the drive shaft 98, via the countershaft 104 and the crankshaft gear 102, into each of the several crankshafts 72.

[0074] Next, features relating to the sealing element 10 of the power transmission device 14, which was described in the fourth to seventh embodiments, are described. The features are described below, mainly with reference to Fig. 6 described. In each embodiment, several sealing elements 10, as described above, are provided, and several sets of a pair of relative rotators 16 are provided. To distinguish the several sealing elements 10 and the several sets of the pair of relative rotators 16 from one another, “-A”, “-B” and “-C” are added to the end of the reference numerals.

[0075] The reduction mechanism 42 in each embodiment is configured with a gear mechanism 110. The gear mechanism 110 includes a gear set 112, which contains several meshing gears. The gear set 112 in the embodiment shown Fig. 6 is configured with the bending gear 52 and the meshing gears 54A and 54B. The gear set 112 in the embodiment shown Fig. Parts 7 to 9 are configured with the oscillating gear 74 and the meshing gear 76. The gear set 112, for example, is made of a metal-based material, such as an iron-based or aluminum-based material, but can also be made of a resin-based material.

[0076] The power transmission device 14 comprises at least one set of a pair of relative rotators 16-A and 16-B, which rotate relative to each other about the centerline Ca when the power transmission device 14 is in operation. Operation of the power transmission device 14 here refers to a state when each power transmission element of the power transmission device 14 is in operation. A power transmission element here refers, for example, to a drive element, a part of the reduction mechanism 42 (the bending gear 52, the oscillating gear 74, or the like), an output element, and the like.

[0077] In the embodiments in Fig. Figures 6 to 9 contain at least one set of the pair of relative rotators 16-A and 16-B, comprising the pair of high-speed relative rotators 16-A rotating relative to each other at a first relative speed, and the pair of low-speed relative rotators 16-B rotating relative to each other at a second relative speed lower than the first relative speed. One of the pair of high-speed relative rotators 16-A is configured with a fixed body 114 attached to an external element (not shown) that supports the power transmission device 14, and the other of the pair of high-speed relative rotators 16-A is configured with a high-speed rotator 116A rotating relative to the fixed body 114. One of the pair of low-speed relative rotators 16-B is configured with the fixed body 114.The other of the pair of low-speed relative rotators 16-B is configured with a low-speed rotator 116B, which rotates at a lower speed relative to the fixed body 114 than the high-speed rotator 116A. Thus, one of the pair of relative rotators 16-A and 16-B is configured with rotators 116A and 116B. One of the fixed body 114 and the high-speed rotator 116A is the first relative rotator 18 described above, and the other is the second relative rotator 20. Furthermore, one of the fixed body 114 and the low-speed rotator 116B is the first relative rotator 18 described above, and the other of the fixed body 114 and the low-speed rotator 116B is the second relative rotator 20.

[0078] In the embodiment in Fig. 6 is the fixed body 114, the speed reducer housing 44, the high-speed rotator 116A is the shaft generator shaft 50, and the low-speed rotator 116B is the counter-drive element 46. Furthermore, in the embodiment in Fig. 7 the fixed body 114 the speed reducer housing 44, the high-speed rotator 116A is the crankshaft 72, and the low-speed rotator 116B is a combination of the counter-drive element 46 and the sleeve 78. In the embodiment in Fig. 8 The fixed body 114 is a combination of the speed reducer housing 44, the adapter 92, and the drive motor housing 96; the high-speed rotator 116A is a combination of the crankshaft 72 and the drive shaft 98; and the low-speed rotator 116B is a combination of the counter-drive element 46 and the driven component 94. In the embodiment shown Fig. 9, the fixed body 114 is a combination of the speed reducer housing 44, the adapter 92, and the drive motor housing 96; the high-speed rotator 116A is a combination of the countershaft 104 and the drive shaft 98; and the low-speed rotator 116B is a combination of the counter-drive element 46 and the driven component 94. In the embodiments in Fig. Figures 6 to 9 show an example where the high-speed rotator 116A and the low-speed rotator 116B are the first relative rotator 18, and the fixed body 114 is the second relative rotator 20. In this way, the specific examples of the fixed body 114, the high-speed rotator 116A, and the low-speed rotator 116B are not particularly limited.

[0079] In the embodiment in Fig. 6 to 8, the pair of relative high-speed rotators 16-A includes a speed-reducing drive shaft 118, which rotates during operation of the power transmission device 14 used for the speed reducer 12. For example, the speed-reducing drive shaft 118 is any shaft generator shaft 50 that drives the bending gear 52, as in the embodiment shown in Fig. 6 bends and deforms, and the crankshaft 72, which drives the oscillating gear 74 in the embodiments in Fig. 7 and Fig. 8 causes it to oscillate.

[0080] As in the embodiment in Fig. In embodiments 6 to 9, sealing elements 10-A to 10-C can include a first sealing element 10-A arranged between at least the pair of relative high-speed rotators 16-A. Furthermore, the sealing elements 10-A to 10-C can include a second sealing element 10-B arranged between the pair of relative low-speed rotators 16-B. In addition, as in the embodiment shown in Fig. 6, the sealing elements 10-A to 10-C include a third sealing element 10-C, which is arranged between the high-speed rotator 116A, which is one of the pair of relative high-speed rotators 16-A, and the low-speed rotator 116B, which is one of the pair of relative low-speed rotators 16-B. The features described in the first to third embodiments can be applied to the sealing elements 10-A to 10-C.

[0081] The reduction mechanism 42 is arranged in the interior 22 of the power transmission device 14, which is sealed by the sealing elements 10-A to 10-C. The interior 22 in each embodiment in Fig. 6 to 9 is formed at least on a section that is surrounded by the fixed body 114 (speed reducer housing 44), the high-speed rotator 116A, and the low-speed rotator 116B (counter-drive element 46). In the embodiments in Fig. 6 to 9, at least one of the speed reducer housing 44 and the counter-drive element 46 also serves as a component of the reduction mechanism 42 (for example, the meshing gears 54A and 54B and the meshing gear 76). That is, a space-forming body that forms the interior space 22 also serves as a partial component of the reduction mechanism 42. In this case, to satisfy a condition in which the reduction mechanism 42 is arranged in the interior space 22, at least one component of the reduction mechanism 42, which differs from the component that also serves as the space-forming body (for example, the bending gear 52 or 74), can be arranged in the interior space 22.

[0082] A lubricant (not shown) is enclosed in the interior 22. The lubricant is used to lubricate a section where each component of the reduction mechanism 42 is in sliding or rolling contact with one another. The section where sliding or rolling contact occurs refers, for example, to an engagement section of several gears that form the gear set 112. The lubricant in the embodiment shown Fig. 6 to 9 is grease, but the specific example is not particularly restricted and could be, for example, a lubricating oil or the like. The interior 22 is sealed by at least one sealing element 10. In addition to the sealing element 10, a sealing element, such as an oil seal, which differs from the sealing element 10, may be used to seal the interior 22. The number of sealing elements 10 sealing the interior 22 is not particularly restricted, and the number and type of sealing elements are not particularly restricted and may be appropriately modified according to the type of power transmission device 14.

[0083] The effects of the sealing element 10 in relation to the features of the power transmission device 14 described above are described.

[0084] Consider a case in which the interior space 22 is sealed by a spring-loaded sealing element using a pumping force. In this case, the present inventors have newly discovered that the pumping force is more likely to increase at a location of the first sealing element 10-A than at a location of the second sealing element 10-B, and that lubricant leakage is likely to occur as a result. This is considered to be caused by the sliding speed of the first sealing element 10-A with respect to the first relative rotator 18 (high-speed rotator 116A), which is one of the pair of high-speed relative rotators 16-A, being faster than the sliding speed of the second sealing element 10-B with respect to the first relative rotator 18 (low-speed rotator 116B), which is one of the pair of low-speed relative rotators 16-B.In this respect, according to the present embodiment, the sealing element 10-A described above, which is advantageous for suppressing lubricant leakage caused by the pumping force, is used between the pair of relative high-speed rotators 16-A. Therefore, it is advantageous to suppress lubricant leakage caused by the pumping force by significantly reducing the pumping force at the section where the pumping force is likely to increase, which is the location of the first sealing element 10-A.

[0085] The sealing element 10-A in the present embodiment fulfills the length condition described above, and thus, as described above, it is advantageous to make the contact length L0 of the entire lip section 28 with the first relative rotator 18 long. Therefore, by increasing the contact length L0, even if foreign matter is trapped between the lip section 28 and the first relative rotator 18, it is easy to maintain a condition in which the lip section 28 is in contact with the first relative rotator 18 at a position that is axially displaced with respect to the trapping position of the foreign matter. This is therefore advantageous in suppressing lubricant leakage caused by the trapping of the foreign matter.In particular, in a case where the reduction mechanism 42 is configured with the gear mechanism 110, it is likely that abrasive powder is generated in the interior 22 of the power transmission device 14 by the engagement of each gear forming the gear set 112. According to the present embodiment, it is effective in suppressing the lubricant leakage caused by the incorporation of the abrasive powder in the power transmission device 14, which uses the gear mechanism 110 where the abrasive powder is likely to be generated in this way.

[0086] The rotator 116A, which contains the speed reducer drive shaft 118, can accommodate a radial load generated within the speed reducer 12. This is, for example, (1) a case where the speed reducer drive shaft 118 is the shaft generator shaft 50, or (2) a case where the speed reducer drive shaft 118 is the crankshaft 72. In case (1), during a process in which the shaft generator 48 of the shaft generator shaft 50 bends and deforms the bending gear 52, a radial load is introduced from the bending gear 52 into the shaft generator shaft 50. In case (2), during a process in which the oscillating gear 74 oscillates, a radial load is introduced from the oscillating gear 74 into the eccentric section 70 of the crankshaft 72.

[0087] The present inventors have newly discovered that in a case where the rotator 116A accepts the radial load in this manner, an axial deviation of the rotator 116A is likely to occur, and consequently, lubricant leakage at the location of the sealing element 10-A between the pair of relative rotators 16-A containing the rotator 116A is likely to occur. This is because, due to the axial deviation of the rotator 116A, partial abrasion occurs at the lip section 28 of the sealing element 10-A, and thus a sealing property of the sealing element 10-A is likely to be impaired. Here, axial deviation means that the position of the rotator 116A's centerline of rotation deviates in the radial direction or that the centerline of rotation deviates at an angle.

[0088] In the present embodiment, the sealing element 10-A fulfills the length condition described above and is advantageous in reducing the contact pressure of the lip section 28, as described above. Therefore, reducing the contact pressure makes it more difficult for partial abrasion of the lip section 28 to occur due to the axial deviation of the rotator 116A, which is advantageous in maintaining the sealing properties of the sealing element 10-A. Thus, even in a case where the rotator 116A is likely to cause the axial deviation due to absorbing the radial load, it is advantageous in suppressing the lubricant leakage caused by the axial deviation.

[0089] Furthermore, the specific example of the speed reducer rotary shaft 118 is not particularly restricted and can be something other than the shaft generator shaft 50 and the crankshaft 72.

[0090] (Eighth embodiment) On Fig. Reference is made to 10. The power transmission device 14 in the present embodiment contains only the speed reducer 12, as in the embodiment in Fig. 6. One configuration of the speed reducer 12 is the same as the configuration in the embodiment in Fig. 6, and the description of it is omitted.

[0091] The pair of relative rotators 16 includes one rotator 134, which transmits a torque between rotator 134 and the other rotator 132 via a torque transmission mechanism 130. In the present embodiment, rotator 134 includes, for example, the wave generator shaft 50, which serves as a drive element, but may also include the crankshaft 72 or the like. In the present embodiment, the other rotator 132 includes the drive shaft 98, but need not include the drive shaft 98.

[0092] In the present embodiment, the rotator 134 accepts a radial load when it transmits a torque between the rotator 134 and the other rotator 132. It can also be said that the torque transmission mechanism 130 is configured to exert the radial load on the rotator 134 when transmitting the torque between the other rotator 132 and the rotator 134. When exerting the radial load on the rotator 134 in this way, the torque transmission mechanism 130 in the present embodiment is configured to use a transmission belt 136. In particular, the torque transmission mechanism 130 in the present embodiment includes a first pulley 138, which is integrally rotatable with the other rotator 132, a second pulley 140, which is integrally rotatable with the rotator 134, and a transmission belt 136, which is tensioned between the first pulley 138 and the second pulley 140.The transmission belt 136 transmits a torque between the first pulley 138 and the second pulley 140.

[0093] The rotator 134, which in the present embodiment comes into contact with the sealing element 10, experiences a radial load when it transmits a torque between the rotator 134 and the other rotator 132. In this case, as in the case described above, axial deviation of the rotator 134 is likely to occur, and lubricant leakage is likely to occur at a location of the sealing element 10 between the pair of relative rotators 16 containing the rotator 134.

[0094] In this respect, the sealing element 10 in the present embodiment fulfills the length condition described above and is advantageous in reducing the contact pressure of the lip section 28 with the first relative rotator 18, as described above. Therefore, the reduction of the contact pressure makes it more difficult for partial abrasion to occur on the lip section 28 due to axial deviation of the rotator 134, which is advantageous in maintaining the sealing properties of the sealing element 10. Thus, even in a case where the rotator 134 is likely to cause the axial deviation due to absorbing the radial load, it is advantageous in suppressing the lubricant leakage caused by the axial deviation.

[0095] In this way, if the rotator 134 bears a radial load, the partial abrasion of the sealing element 10, which comes into contact with the rotator 134, makes lubricant leakage likely. For example, a case in which the rotator 134 bears the radial load in this way is assumed to be one in which the power transmission device 14 is installed in a joint section of a robot. In this case, too, an advantage is that the lubricant leakage caused by the axial deviation of the rotator 134 can be suppressed by using the sealing element 10 configuration described above.

[0096] In a case where axial deviation of the rotator 134 is likely to occur, the groove section 34 can be positioned in the contact area 32 of the lip section 28 as in the embodiment shown in Fig. 4. By using the groove section 34 as a lubricant reservoir, the amount of lubricant present between the first relative rotator 18 and the lip section 28 can be increased. Accordingly, it is possible to suppress partial wear caused by the axial deviation of the rotator 134, and it is advantageous to suppress lubricant leakage caused by the axial deviation.

[0097] When applying a radial load to the rotator 134, the specific example of the torque transmission mechanism 130 is not particularly restricted. To achieve this, the torque transmission mechanism 130 can be configured to use, for example, a gear set, such as a bevel gear set and a helical gear set, meshing with each other. Furthermore, the rotator 134 does not need to bear a radial load when it transmits torque to the other rotator 132.

[0098] Next, modification examples for each component described above will be described.

[0099] A specific example of the reduction mechanism 42 used for the speed reducer 12 is not particularly restricted. In a case where the reduction mechanism 42 is a gear mechanism, the gear mechanism can, for example, be a simple planetary gear mechanism, a gear mechanism with a perpendicular shaft, or a gear mechanism with a parallel shaft, in addition to the eccentrically oscillating reduction mechanism and the bending-engage reduction mechanism. Furthermore, a specific type of bending-engage reduction mechanism is not particularly restricted and can be a tubular type, as in the embodiment shown in Fig.6, a top hat type, a pot type, or the like. The specific type of eccentrically oscillating reduction mechanism is not particularly restricted, and the central crank type, distribution type, or the like described above may be used. In addition, the reduction mechanism 42 may be a friction drive mechanism (traction drive) in addition to the gear mechanism.

[0100] The sealing element 10, to which the feature of the present disclosure is applied, may be arranged between at least one set of the pair of relative rotators 16, and it may not be arranged between the multiple sets of the pair of relative rotators 16. In this case, the sealing element 10, to which the feature of the present disclosure is applied, may be arranged between the set of the pair of relative rotators 16, and another sealing element (for example, a spring-loaded sealing element), such as an oil seal, to which the feature of the present disclosure is not applied, may be arranged between another set of the pair of relative rotators 16.Furthermore, the sealing element 10 to which the feature of the present disclosure is applied can only be arranged between the pair of relative rotators 16-A with high rotational speed or only between the pair of relative rotators 16-B with low rotational speed.

[0101] The contents of each component described in the embodiments above and the like are merely examples. The technical idea abstracted from these contents should not be interpreted in a restrictive manner in the contents of this description. The contents of each component described in the embodiments or the like may be modified, supplemented, deleted, or otherwise altered, and many design changes may be made. The description is emphasized by adding the designations "the present embodiment" and "the embodiment" to the contents where such a design change may be made. However, the design change is permissible even if there is no designation for the contents. Hatching applied to the cross-sections in the drawings does not restrict a material of a hatched object.Structures and numerical values, as mentioned in the embodiments and modification examples, naturally include those that can be considered equivalent, taking into account manufacturing defects and the like. Any combination of the above components is also valid. For example, any description of other embodiments can be combined with the embodiment described, or the modification examples can be combined with any description of the embodiments and modification examples. The components configured with a single element in the description presented here can be configured with multiple elements. Similarly, the components configured with multiple elements can be configured with a single element. Brief description of the reference symbols 10 sealing element 12 speed reducers 14 Power transmission device 16, 16-A, 16-B pair of relative rotators 16-A pair of high-speed relative rotators 16-B pair of low-speed relative rotators 18 first relative rotator 20 second relative rotator 22 Interior 24 Outdoor area 28 Lip section 28a Corner section 28b Tip end face 32 Contact area 34 Groove section 42 Reduction mechanism 48 wave generator 50 shaft generator shaft 72 Crankshaft 74 oscillating gear 118 Speed ​​reducer rotary shaft 130 Torque transmission mechanism 134 Rotator QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2024-182206

[0002] JP 2006-283981 [0003, 0004]

Claims

[1] Power transmission device (14) comprising: a speed reducer (12); a pair of relative rotators (16) that rotate relative to each other; and a sealing element (10) arranged between the pair of relative rotators (16) and sealing an interior (22) of the power transmission device (14), wherein the sealing element (10) includes a lip section (28) which comes into contact with a first relative rotator (18) which is one of the pair of relative rotators (16), the lip section (28) is not attached with a spring element for pressing the lip section (28) towards the first relative rotator (18), the lip section (28) includes a corner section (28a) which is provided at a position facing the first relative rotator (18) in a radial direction, and a contact length (La) of the lip section (28) with the first relative rotator (18) in an axial direction on a side of the corner section (28a) axially opposite the interior (22) is greater than a contact length (Lb) of the lip section (28) with the first relative rotator (18) in the axial direction on a side of the interior in the axial direction of the corner section (28a). [2] Power transmission device (14) according to claim 1, wherein the lip section (28) includes a tip end surface (28b) which is continuous with the corner section (28a), and a side surface (28c) which is continuous with the corner section (28a), and the lip section (28) with the first relative rotator (18) is in contact only at the side surface (28c) of the tip end surface (28b) and the side surface (28c). [3] Power transmission device (14) according to claim 1, wherein the lip section (28) contains a tip end surface (28b) which is continuous with the corner section (28a), and a contact length (L0) of the entire lip section (28) with the first relative rotator (18) in the axial direction is greater than an axial length (L28b) of the tip end face (28b) when the lip section (28) is in a non-deformation state. [4] Power transmission device (14) according to claim 1, wherein a contact length (L0) of the entire lip section (28) with the first relative rotator (18) in the axial direction is greater than a minimum thickness of the lip section (28) at a contact section of the lip section (28) with the first relative rotator (18). [5] Power transmission device (14) according to claim 1, wherein the lip section (28) contains a contact area (32) which includes an entire contact section of the lip section (28) with the first relative rotator (18), and the contact area (32) is provided with at least one groove section (34). [6] Power transmission device (14) according to claim 1, wherein the pair of relative rotators (16) comprises a pair of high-speed relative rotators (16-A) rotating relative to each other at a first relative speed, and a pair of low-speed relative rotators (16-B) rotating relative to each other at a second relative speed which is lower than the first relative speed, and the sealing element (10) is arranged at least between the pair of relative high-speed rotators (16-A). [7] Power transmission device (14) according to claim 1, wherein the speed reducer (12) includes a reduction mechanism (42) configured with a gear mechanism (110). [8] Power transmission device (14) according to claim 1, wherein a lubricant is enclosed in the interior (22), and the lubricant contains at least one type of Mo, S, Ca, Zn, Ba, Mg, P, C, B and W. [9] Power transmission device (14) according to claim 1, wherein the pair of relative rotators (16) includes a rotator (134) which transmits a torque between the rotator (134) and the other rotator (132) via a torque transmission mechanism (130), and the rotator (134) accepts a radial load when it transmits the torque between the rotator (134) and the other rotator (132). [10] Power transmission device (14) according to claim 1, wherein the pair of relative rotators (16) includes a rotator (16-A) which contains a speed reducer rotating shaft (118), and the speed reducer rotary shaft (118) is a crankshaft (72) which causes an oscillating gear (74) to oscillate, or a shaft generator shaft (50) which flexibly deforms a bending gear (52).

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