Patent Description:
Conventionally, sealing devices are used to seal a gap between a rotating shaft and a through-hole into which the shaft is inserted. Some of such sealing devices are used for mechanisms such as differential mechanisms and hub bearings in vehicles that are exposed to foreign matter such as muddy water, rainwater, and dust. Some of such sealing devices have a side lip formed so as to extend to an open-air side to prevent entry of foreign matter. The side lip is in contact with a member such as a deflector extending radially from a shaft and thereby prevents foreign matter from entering the inside from the open-air side.

<FIG> is a cross-sectional view for illustrating a schematic configuration of a conventional sealing device <NUM> that is used, for example, for a differential mechanism. <FIG> is a cross-sectional view of the conventional sealing device illustrated in <FIG> in a state of being attached to a differential mechanism provided in a transaxle, for example. As illustrated in <FIG>, the conventional sealing device <NUM> includes an annular reinforcing ring <NUM> and an annular elastic body part <NUM> formed from an elastic body that is integrally formed with the reinforcing ring <NUM>, and the elastic body part <NUM> includes a seal lip <NUM>, a dust lip <NUM>, and a side lip <NUM>. As illustrated in <FIG>, the seal lip <NUM> in a usage state is in contact with an axle <NUM> of a differential mechanism <NUM> to thereby prevent lubricant in a housing <NUM> in which the differential mechanism <NUM> is housed from leaking out. The dust lip <NUM> is formed outside (at the open-air side of) the seal lip <NUM>, and is in contact with or adjacent to the axle <NUM> to thereby prevent foreign matter from entering into the housing <NUM> from the outer side. As illustrated in <FIG>, the side lip <NUM> extends toward the outer side on an outer periphery side of the dust lip <NUM>, and has a conical cylindrical shape that increases in diameter as progress toward an outer side. The shape of the side lip <NUM> is such that a distal end portion of the side lip <NUM> is bent inwardly. As illustrated in <FIG>, the side lip <NUM> in the usage state prevents foreign matter from entering from the outer side, with a distal end edge of the side lip <NUM> being in contact with a sliding surface 113a of an annular deflector <NUM> fixed to the axle <NUM>. The side lip <NUM> is elastically deformed and curved in a state of being in contact with the deflector <NUM>, and an inner peripheral surface of the distal end edge is formed so as to be in contact with the sliding surface 113a of the deflector <NUM>.

The sealing device <NUM> is attached between a through-hole <NUM> in the housing <NUM> in which the differential mechanism <NUM> is housed and the axle <NUM> inserted through the through-hole <NUM> in order to seal the through-hole <NUM>, thereby preventing the lubricant stored in the housing <NUM> from leaking out to the outer side, and preventing the foreign matter from entering into the housing <NUM> (for example, see Patent Literature <NUM>).

<CIT>, <CIT>, and <CIT> each disclose a sealing device for sealing between a through-hole and a shaft inserted through the through-hole, the sealing device comprising an annular elastic seal lip in which at least one roove is formed.

<CIT> and <CIT> each disclose a sealing device for sealing between a through-hole and a shaft inserted through the through-hole, the sealing device comprising an annular elastic seal lip in which a distal end portion is formed so as to decrease in thickness as progress toward a middle portion side of the seal lip.

In the conventional sealing device <NUM>, as described above, the distal end portion of the side lip <NUM> is bent. This prevents a contact pressure on the deflector <NUM> at a distal end of the side lip <NUM> in the usage state from decreasing and prevents the distal end of the side lip <NUM> from floating away from the sliding surface 113a of the deflector <NUM>. This configuration prevents foreign matter from entering the inner side. In this way, the conventional sealing device <NUM> has high performance in preventing the entry of foreign matter. However, due to a need for further improved fuel efficiency and the like in recent years and a need for a further improvement in durability of the side lip <NUM>, there has been a demand for a reduction in sliding torque caused by a sliding movement of the side lip <NUM>.

In view of the challenge described above, it is an object of the present invention to provide a sealing device capable of reducing sliding torque caused by a side lip. Solution to Problem.

A sealing device according to the present invention, accomplished to attain the object described above, is defined in claim <NUM>. The sealing device is for sealing between a through-hole and a shaft inserted through the through-hole, wherein the sealing device includes: a reinforcing ring formed annularly around an axis; and an elastic body part formed from an elastic body that is attached to the reinforcing ring and that is formed annularly around the axis, the elastic body part including: an annular seal lip, the seal lip being in contact with the shaft such that the shaft is slidable; an annular dust lip, the dust lip being provided on an outer side of the seal lip and extending toward the axis; and an annular side lip, the side lip extending toward the outer side on an outer periphery side of the dust lip, the side lip having: an annular middle portion, the middle portion increasing in diameter as progress toward the outer side in a direction of the axis; and an annular distal end portion, the distal end portion being a portion connected to and on the outer side of the middle portion, the distal end portion increasing in diameter as progress toward the outer side in the direction of the axis, wherein in the side lip, the distal end portion is bent to an inner periphery side from the middle portion, and wherein in the middle portion, at least one groove is formed annularly around the axis.

Furthermore, according to the invention, the distal end portion of the side lip is formed so as to decrease in thickness as progress toward the middle portion side.

In the sealing device according to one aspect of the present invention, the groove is formed in an inner peripheral surface of the middle portion.

In the sealing device according to one aspect of the present invention, a cross section of the groove along the axis has an outline of an arc having a fixed curvature.

In the sealing device according to one aspect of the present invention, the groove is not formed in a connection zone between the distal end portion and the middle portion.

In the sealing device according to one aspect of the present invention, a plurality of the grooves are formed, and a space between the grooves adjacent to each other is constant.

In the sealing device according to one aspect of the present invention, the middle portion is formed so as to have a fixed thickness.

In the sealing device according to one aspect of the present invention, the distal end portion has a conical cylindrical shape centered about the axis, and the middle portion has a conical cylindrical shape centered about the axis.

In the sealing device according to one aspect of the present invention, the side lip has a root portion formed annularly around the axis, and the middle portion is a portion that is connected to the root portion and that is on the outer side of the root portion.

The sealing device according to the present invention is capable of reducing sliding torque caused by the side lip.

Hereinafter, illustrative examples and embodiments of the present invention will be described with reference to the drawings.

<FIG> is a cross-sectional view taken along an axis x for illustrating a schematic configuration of a sealing device <NUM> according to a first illustrative example. <FIG> is a partial enlarged cross-sectional view of the sealing device <NUM> illustrated in <FIG>. The sealing device <NUM> according to the first illustrative example is used to seal a gap between a through-hole and a shaft inserted through the through-hole, in which the through-hole and the shaft rotate relative to each other. The sealing device <NUM> is used, for example, for a device provided with a differential mechanism for absorbing a difference in rotational speed between right and left driving wheels during turning of a vehicle, a general purpose machine, or the like. Examples of the device provided with the differential mechanism include transaxles and differential devices. In the present example, the sealing device <NUM> is used for a transaxle. Specifically, in the transaxle, the sealing device <NUM> is used for sealing between a through-hole formed in a housing and an axle as an output shaft of the differential mechanism that is rotatably inserted through the through-hole, as described later. A component to which the sealing device <NUM> is applied is not limited to this specific example. The sealing device can be applied to other rotating members in various machines.

Hereinafter, a direction directed by an arrow a in a direction of the axis x (see <FIG>) represents an outer side, and a direction directed by an arrow b in the direction of the axis x (see <FIG>) represents an inner side, for convenience of explanation. The outer side means a side facing the outside of a component to which the sealing device is applied, and the inner side means a side facing the inside of the component to which the sealing device is applied. More specifically, the outer side means a side facing the outside of the housing in the transaxle provided with a differential mechanism, and an atmosphere side, and the inner side means a side facing the inside of the housing in the transaxle. In a direction perpendicular to the axis x (hereinafter also referred to as a "radial direction"), a direction away from the axis x (a direction directed by an arrow c in <FIG>) represents an outer periphery side, and a direction approaching the axis x (a direction directed by an arrow d in <FIG>) represents an inner periphery side.

The sealing device <NUM> includes a reinforcing ring <NUM> formed annularly around the axis x and an elastic body part <NUM> formed from an elastic body that is attached to the reinforcing ring <NUM> and that is formed annularly around the axis x. The elastic body part <NUM> includes an annular seal lip <NUM> that is put into contact with a shaft of the component to which the sealing device is applied, such that the shaft is slidable, as described later, an annular dust lip <NUM> that is provided on the outer side (an arrow a direction side) of the seal lip <NUM> and that extends toward the axis x, and an annular side lip <NUM> that extends toward the outer side on the outer periphery side (an arrow c direction side) of the dust lip <NUM>. The side lip <NUM> has an annular middle portion <NUM> that increases in diameter as progress toward the outer side in the direction of the axis x and an annular distal end portion <NUM> that is a portion connected to and on the outer side of the middle portion <NUM> and that increases in diameter as progress toward the outer side in the direction of the axis x. In the side lip <NUM>, the distal end portion <NUM> is bent to the inner periphery side (an arrow d direction side) from the middle portion <NUM>. In the middle portion <NUM>, at least one groove <NUM> is formed annularly around the axis x. Hereinafter, a structure of the sealing device <NUM> will be described in detail.

As illustrated in <FIG> and <FIG>, the reinforcing ring <NUM> is an annular member centered about or substantially centered about the axis x and is made of metal. A shape of a cross section along the axis x (hereinafter simply referred to as a "cross section") of the reinforcing ring <NUM> is an L shape or a substantially L shape. The reinforcing ring <NUM>, for example, includes a cylindrical part <NUM> that is a cylindrical or substantially cylindrical portion extending in the direction of the axis x, and a disc <NUM> that is a hollow disc-shaped portion extending toward the inner periphery side from an outer end portion of the cylindrical part <NUM>. The cylindrical part <NUM> is formed such that the sealing device <NUM> is allowed to be fitted to an inner peripheral surface of the through-hole formed in the housing of the transaxle, as described later. The cylindrical part <NUM> may be directly in contact with the inner peripheral surface of the through-hole to be able to be fitted to the inner peripheral surface of the through-hole, or may be in contact with the inner peripheral surface of the through-hole through a portion of the elastic body part <NUM> to be able to be fitted to the inner peripheral surface of the through-hole.

As illustrated in <FIG> and <FIG>, the elastic body part <NUM> is attached to the reinforcing ring <NUM>, and is integrally formed with the reinforcing ring <NUM> to cover the entire reinforcing ring <NUM> in the present example. The elastic body part <NUM>, as described above, includes the seal lip <NUM>, the dust lip <NUM>, and the side lip <NUM> and also includes an annular lip waist portion <NUM>. The seal lip <NUM> is formed so as to be in contact with an axle of the differential mechanism so that the axle is slidable, as described later, and the dust lip <NUM> is provided on the outer side of the seal lip <NUM> and formed so as to be in contact with the axle so that the axle is slidable. The side lip <NUM> is formed so as to be in contact with an annular deflector fixed to the axle so that the deflector is slidable, and extends toward the outer side on the outer periphery side of the dust lip <NUM> as described later. In the elastic body part <NUM>, the lip waist portion <NUM> is a portion positioned in the vicinity of an end portion on the inner periphery side of the disc <NUM> of the reinforcing ring <NUM>.

Specifically, the seal lip <NUM> is a portion that extends toward the inner side from the lip waist portion <NUM>, and an annular portion centered about or substantially centered about the axis x, and is formed by facing the cylindrical part <NUM> of the reinforcing ring <NUM>, as illustrated in <FIG> and <FIG>. The seal lip <NUM> has an annular lip distal end portion <NUM> at an inner end portion, the lip distal end portion <NUM> having a cross section formed in a wedge shape projecting toward the inner periphery side. A garter spring <NUM> is fitted at a position facing away from the lip distal end portion <NUM> on the outer periphery side of the seal lip <NUM>. The garter spring <NUM> presses the lip distal end portion <NUM> in a direction toward the axis x to apply a tensional force of a predetermined magnitude to the lip distal end portion <NUM> against the axle such that the lip distal end portion <NUM> follows a displacement of the axle. The lip distal end portion <NUM> is in contact with an outer peripheral surface of the axle to seal between the sealing device <NUM> and the axle, as described later. As illustrated in <FIG>, a plurality of screw projections 25b are formed at equal angle intervals in a circumferential direction on a taper surface 25a of a conical surface shape of the lip distal end portion <NUM> on the outer side, the screw projections 25b extending diagonally with respect to a distal end of the lip distal end portion <NUM> and projecting to the inner periphery side. The screw projections 25b generate air flow from the outside to the inner side when the axle is slid, to thereby prevent lubricant from leaking from the inside. The elastic body part <NUM> may not be provided with the screw projections 25b.

The dust lip <NUM> extends outwardly from the lip waist portion <NUM> and toward the axis x, more particularly, as illustrated in <FIG>, <FIG>, the dust lip <NUM> extends in a direction toward the outer side and the inner periphery side from the lip waist portion <NUM>. The dust lip <NUM> prevents foreign matter such as muddy water, sand, and dust from entering in a direction from the outer side toward the lip distal end portion <NUM>. In the dust lip <NUM>, in order that a negative pressure is not generated in a space between the dust lip <NUM> and the seal lip <NUM> in the usage state, a plurality of projections 22a projecting in the inner peripheral direction are formed at equal angle intervals in a circumferential direction so that a gap is formed by partially releasing the contact between the dust lip <NUM> and the axle to thereby suppress the generation of the negative pressure or eliminate the negative pressure. The dust lip <NUM> may be adjacent to the axle without being in contact with the axle, or may not have the projections 22a.

The elastic body part <NUM> includes a gasket part <NUM>, a rear cover part <NUM>, and a lining part <NUM>. In the elastic body part <NUM>, the gasket part <NUM> is a portion that covers the cylindrical part <NUM> of the reinforcing ring <NUM> from the outer periphery side. As described later, the thickness in the radial direction of the gasket part <NUM> is set so that, when, in the transaxle, the sealing device <NUM> is press-fitted into a through-hole through which the axle is inserted, the gasket part <NUM> is compressed between the through-hole and the cylindrical part <NUM> of the reinforcing ring <NUM> in the radial direction so that the gasket part <NUM> generates a fitting force of a predetermined magnitude in the radial direction. The rear cover part <NUM> is a portion that covers the disc <NUM> of the reinforcing ring <NUM> from the outer side. The lining part <NUM> is a portion that covers the reinforcing ring <NUM> from the inner side and the inner periphery side.

As illustrated in <FIG>, <FIG>, the side lip <NUM> has the distal end portion <NUM>, the middle portion <NUM>, and a root portion <NUM>. The root portion <NUM> is an annular portion extending in the direction of the axis x. The middle portion <NUM> is a portion that is connected to the root portion <NUM> and is on the outer side of the root portion <NUM>. The distal end portion <NUM> is a portion that is connected to the middle portion <NUM> and is on the outer side of the middle portion <NUM>. Specifically, in the elastic body part <NUM>, the side lip <NUM> extends outwardly from an outer side portion of the lip waist portion <NUM>, and the root portion <NUM> extends outwardly from the lip waist portion <NUM>. The middle portion <NUM> extends outwardly from an outer end portion of the root portion <NUM>, and the distal end portion <NUM> extends outwardly from an outer end portion of the middle portion <NUM>. Note that the side lip <NUM> may have no root portion <NUM>, and the middle portion <NUM> may extend from the lip waist portion <NUM>.

An inner peripheral surface 31a that is a surface on the inner periphery side of the distal end portion <NUM> and an inner peripheral surface 32a that is a surface on the inner periphery side of the middle portion <NUM> are connected at an inner peripheral connection portion c1 that forms an annular line. An outer peripheral surface 31b that is a surface on the outer periphery side of the distal end portion <NUM> and an outer peripheral surface 32b that is a surface on the outer periphery side of the middle portion <NUM> are connected at an outer peripheral connection portion c2 that forms an annular line. The inner peripheral surface 31a of the distal end portion <NUM> and the inner peripheral surface 32a of the middle portion <NUM> may be smoothly connected to each other. Similarly, the outer peripheral surface 31b of the distal end portion <NUM> and the outer peripheral surface 32b of the middle portion <NUM> may be smoothly connected to each other.

Specifically, the distal end portion <NUM> has a conical cylindrical or substantially conical cylindrical shape centered or substantially centered about the axis x. The middle portion <NUM> has a conical cylindrical or substantially conical cylindrical shape centered or substantially centered about the axis x, and the root portion <NUM> has a cylindrical or substantially cylindrical shape centered or substantially centered about the axis x. The root portion <NUM> may have a conical cylindrical or substantially conical cylindrical shape. As described above, the distal end portion <NUM> is bent to the inner periphery side from the middle portion <NUM> such that an angle (angle α) between a generating line of the inner peripheral surface 31a or the outer peripheral surface 31b of the distal end portion <NUM> and the axis x is smaller than an angle (angle β) between a generating line of the inner peripheral surface 32a or the outer peripheral surface 32b of the middle portion <NUM> and the axis x (see <FIG>).

As illustrated in <FIG>, a thickness w1 of the distal end portion <NUM>, i.e., a width between the inner peripheral surface 31a and the outer peripheral surface 31b of the distal end portion <NUM>, is a fixed thickness or a substantially fixed thickness, and a thickness w2 of the middle portion <NUM>, i.e., a width between the inner peripheral surface 32a and the outer peripheral surface 32b of the middle portion <NUM>, is a fixed thickness or a substantially fixed thickness. As illustrated in <FIG>, a thickness w3 of the root portion <NUM>, i.e., a width between the inner peripheral surface 33a and the outer peripheral surface 33b of the root portion <NUM>, is a fixed thickness or a substantially fixed thickness.

As illustrated in <FIG>, in a connection zone C that is a zone of connection between the distal end portion <NUM> and the middle portion <NUM>, the inner peripheral connection portion c1 of the inner peripheral surfaces 31a, 32a is positioned on the inner side of the outer peripheral connection portion c2 of the outer peripheral surfaces 31b, 32b in the direction of the axis x. In other words, in the distal end portion <NUM>, the inner peripheral surface 31a is longer than the outer peripheral surface 31b in the direction of the axis x. However, a form of the connection zone C is not limited to this example. The connection zone C may be formed such that the inner peripheral connection portion c1 and the outer peripheral connection portion c2 are positioned at identical or substantially identical positions in the direction of the axis x, for example.

As described above, in the middle portion <NUM> of the side lip <NUM>, at least one groove <NUM> is formed annularly around the axis x. The groove <NUM> is formed in the inner peripheral surface 32a of the middle portion <NUM> and is recessed from the inner peripheral surface 32a. In the present embodiment, a plurality of grooves <NUM> are formed. For example, as illustrated in <FIG> and <FIG>, five grooves <NUM> are formed. Specifically, the grooves <NUM> each extend in the shape of a circle or substantially circle centered or substantially centered about the axis x. The grooves <NUM> are mutually concentric or substantially concentric circles. As illustrated in <FIG>, a cross section of each of the grooves <NUM> along the axis x has an outline of an arc having a fixed curvature. The outline of the cross section of the groove <NUM> is a semicircle, for example. The outline of the cross section of the groove <NUM> may not be a semicircle but may be, for example, an arc smaller than the semicircle. The outline of the cross section of the groove <NUM> may be, for example, a combination of a curved line and a straight line, other than the arc having the fixed curvature. It is preferable that the outline of the cross section of each of the grooves <NUM> is a shape that facilitates warping of the side lip <NUM> to the outer periphery side, as described later.

A space between the grooves <NUM> adjacent to each other is constant or substantially constant and more particularly, in the middle portion <NUM> of the side lip <NUM>, the grooves <NUM> are arranged at equal or substantially equal intervals along the inner peripheral surface 32a of the middle portion <NUM>. No groove <NUM> is formed in the connection zone C between the distal end portion <NUM> and the middle portion <NUM>. In other words, no groove <NUM> is formed in the inner peripheral connection portion c1 between the distal end portion <NUM> and the middle portion <NUM>. The groove <NUM> positioned on the outer side of the middle portion <NUM> is formed inwardly apart from the inner peripheral connection portion c1.

In the side lip <NUM>, as described above, the distal end portion <NUM> is bent to the inner periphery side from the middle portion <NUM>. Thus, in the sealing device <NUM> in the usage state, as described later, the side lip <NUM> generates a contact pressure on the deflector at the distal end portion <NUM> with respect to a contact pressure on the deflector at the middle portion <NUM> such that the contact between a distal end <NUM> of the side lip <NUM> and the deflector is not released. In other words, when a position of contact of the side lip <NUM> with the deflector reaches the middle portion <NUM> beyond the distal end portion <NUM>, the contact pressure at the distal end portion <NUM> of the side lip <NUM> on the deflector is made larger than the contact pressure at the middle portion <NUM> on the deflector to prevent the distal end <NUM> of the side lip <NUM> from floating away from the deflector.

As described above, the grooves <NUM> are formed in the middle portion <NUM> of the side lip <NUM>, and this provides a reduction in rigidity (resistance) of the middle portion <NUM> to being warped (bent) to the outer periphery side. This allows the side lip <NUM>, as compared with a side lip having no grooves <NUM>, to reduce a pressure (pressing force) put on the deflector through a zone of contact of the distal end portion <NUM> with the deflector, or a reaction force put by the deflector through a zone of contact of the deflector with the distal end portion. This contributes to a reduction in sliding torque caused by the side lip <NUM>. On the other hand, in the side lip <NUM>, as described above, the distal end portion <NUM> is bent to the inner periphery side from the middle portion <NUM>. This configuration allows the side lip <NUM> to keep the contact pressure on the deflector at the distal end portion <NUM> larger than the contact pressure on the deflector at the middle portion <NUM>, prevent the distal end <NUM> of the side lip <NUM> from floating away from the deflector, and prevent foreign matter from entering the inside. Since the grooves <NUM> are provided in the middle portion <NUM>, the side lip <NUM> makes an area of contact of the middle portion <NUM> with the deflector small and the contact pressure at the middle portion <NUM> large as compared with a side lip having no grooves <NUM>. However, the distal end portion <NUM> is bent with respect to the middle portion <NUM> and hence in the side lip <NUM>, the contact pressure at the distal end portion <NUM> is larger than the contact pressure at the middle portion <NUM>. This enables the distal end portion <NUM> of the side lip <NUM> to be stably in contact with the deflector without floating away from the deflector.

In this way, the sealing device can reduce sliding torque caused by the side lip <NUM> while the side lip <NUM> is kept in a state of stable contact without letting the distal end portion <NUM> float away from the deflector.

Note that the elastic body part <NUM> is integrally formed of an elastic material, and the seal lip <NUM>, the dust lip <NUM>, the side lip <NUM>, the lip waist portion <NUM>, the gasket part <NUM>, the rear cover part <NUM>, and the lining part <NUM> are respective portions of the elastic body part <NUM> that is integrally formed of the elastic material.

The metal material for the reinforcing ring <NUM> is, for example, stainless steel or SPCC (a cold rolled steel sheet). Examples of the elastic body of the elastic body part <NUM> include various rubber materials. The various rubber materials are, for example, synthetic rubber such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), and fluororubber (FKM). The reinforcing ring <NUM> is manufactured by press working or forging, for example, and the elastic body part <NUM> is molded with a mold by cross-linking (vulcanization). During the cross-linking, the reinforcing ring <NUM> is placed in the mold, the elastic body part <NUM> is bonded to the reinforcing ring <NUM> by cross-linking bonding, and the elastic body part <NUM> is integrally molded with the reinforcing ring <NUM>.

Next, operation of the sealing device <NUM> having the above-described configuration will be described. <FIG> is a view for illustrating the sealing device <NUM> in a state of being attached to a transaxle <NUM> that is an example of a component to which the sealing device is applied, and a partial enlarged cross-sectional view along the axis x enlargedly illustrating the vicinity of the sealing device <NUM> in the transaxle <NUM>. Note that <FIG> illustrates a state where the sealing device <NUM> is attached to a desired position of the transaxle <NUM> (hereinafter referred to as an "initial state"). In other words, the sealing device <NUM> is attached to the transaxle <NUM> in such a manner that the distal end portion <NUM> of the side lip <NUM> is in contact with a sliding surface <NUM> of an annular deflector <NUM> by a desired contact width δ, the deflector <NUM> being fixed to an axle <NUM> as an output shaft of the differential mechanism (not illustrated) of the transaxle <NUM>. The transaxle <NUM> is a well-known transaxle (see <FIG>), and a detailed description of the configuration is omitted herein. Note that the deflector <NUM> may be formed of a member separate from the axle <NUM>, or the deflector <NUM> may be formed by forming a part of the axle <NUM> to be annularly projected toward the outer periphery side.

As illustrated in <FIG>, the sealing device <NUM> is fitted to a through-hole <NUM> formed in a housing <NUM> of the transaxle <NUM>. The axle <NUM> is rotatably inserted through the through-hole <NUM>. Note that the transaxle <NUM> is provided with two through-holes and two axles for right and left wheels, but the through-holes and the axles corresponding to respective wheels have similar configurations, respectively, and the through-hole <NUM> and the axle <NUM> correspond to each of the right and left wheels, respectively.

In the through-hole <NUM> in the housing <NUM>, a space between an outer peripheral surface 51a of the axle <NUM> and an inner peripheral surface 55a of the through-hole <NUM> is sealed by the sealing device <NUM>. Specifically, the sealing device <NUM> is fitted to the through-hole <NUM>, the gasket part <NUM> of the elastic body part <NUM> is compressed between the cylindrical part <NUM> of the reinforcing ring <NUM> and the inner peripheral surface 55a of the through-hole <NUM> so that the gasket part <NUM> is in close contact with the inner peripheral surface 55a of the through-hole <NUM>, thereby sealing between the sealing device <NUM> and the through-hole <NUM> on the outer periphery side. The lip distal end portion <NUM> of the seal lip <NUM> of the elastic body part <NUM> is in contact with the outer peripheral surface 51a of the axle <NUM> so that the axle <NUM> is slidable, thereby sealing between the sealing device <NUM> and the axle <NUM> on the inner periphery side. Thus, the lubricant stored in the housing <NUM> is prevented from leaking out to the outside.

A distal end edge of the dust lip <NUM> is in contact with the outer peripheral surface 51a of the axle <NUM> so that the axle <NUM> is slidable, thereby preventing foreign matter from entering into the housing <NUM> from the outside. The dust lip <NUM> may not be in contact with the axle <NUM>. In the side lip <NUM>, a distal end edge in the inner peripheral surface 31a in a range of the contact width δ of the distal end portion <NUM> is in contact with the sliding surface <NUM> of the deflector <NUM>, thereby preventing the foreign matter from entering into the housing <NUM> from the outside.

<FIG> is an enlarged cross-sectional view of the side lip <NUM> for illustrating a state of the side lip <NUM> in the initial state. As illustrated in <FIG>, in the initial state, the distal end portion <NUM> of the side lip <NUM> is partially curved or is elastically deformed, and the inner peripheral surface 31a of the distal end portion <NUM> is in contact with the sliding surface <NUM> of the deflector <NUM> in a range of a contact width δ0 from the distal end <NUM>.

In the transaxle <NUM>, the axle <NUM> may be displaced inwardly in the direction of the axis x so that the sliding surface <NUM> of the deflector <NUM> may be displaced in the direction of the axis x, or the axle <NUM> may be inclined with respect to the axis x so that the sliding surface <NUM> of the deflector <NUM> may be inclined, due to dimensional tolerance and assembly errors of each configuration. When the transaxle <NUM> is operated, the axle <NUM> may be displaced in the direction of the axis x or displaced diagonally with respect to the axis x based on the gap between respective configurations. If such a displacement (looseness) occurs, the width δ of contact of the side lip <NUM> with the deflector <NUM> is increased as illustrated in <FIG>. In the side lip <NUM> in the sealing device <NUM>, the distal end portion <NUM> is bent from the middle portion <NUM> toward the inner periphery side as described above. Thus, even when the contact width δ is increased, the contact pressure at the distal end <NUM> on the deflector <NUM> is not reduced, and a difference between the contact pressure at the distal end <NUM> and the contact pressure on a root side does not become so small that the distal end <NUM> of the side lip <NUM> floats away from the sliding surface <NUM> of the deflector <NUM>.

Specifically, as illustrated in <FIG>, even when a considerable looseness occurs in the axle <NUM>, and the contact width δ is increased and becomes a contact width δ1 in which the side lip <NUM> contacts the sliding surface <NUM> of the deflector <NUM> at also the inner peripheral surface 32a of the middle portion <NUM> beyond the inner peripheral surface 31a of the distal end portion <NUM> toward the root side, the distal end <NUM> can be prevented from floating away from the sliding surface <NUM> of the deflector <NUM>. Even in a state of the large contact width δ1 as illustrated in <FIG>, the contact pressure at the distal end portion <NUM> of the side lip <NUM> is larger than the contact pressure at the middle portion <NUM> of the side lip <NUM>.

The grooves <NUM> are formed in the middle portion <NUM> of the side lip <NUM> and hence the side lip <NUM> readily bends at the middle portion <NUM> to the outer periphery side. As a result, when the side lip <NUM> is in a state of the large contact width as illustrated in <FIG>, a reaction force produced by the bent middle portion <NUM> is low and a pressure of the side lip <NUM> on the deflector <NUM> is lower than that of a side lip having no grooves <NUM>. Thus, the sealing device is able to reduce the pressing force of the side lip <NUM> as compared with conventional sealing devices, reduce a sliding resistance generated by the contact of the side lip <NUM> with the deflector <NUM>, and reduce sliding torque exerted by the side lip <NUM> on the axle <NUM>. On the other hand, this configuration, as described above, can maintain the contact pressure at the distal end portion <NUM> of the side lip <NUM> to be larger than the contact pressure at the middle portion <NUM> of the side lip <NUM> and prevent the distal end <NUM> of the side lip <NUM> from floating away from the sliding surface <NUM> of the deflector <NUM>.

In this way, the sealing device <NUM> according to the first embodiment of the present invention is capable of reducing sliding torque caused by the side lip <NUM>.

Next, a sealing device <NUM> according to a second illustrative example will be described. <FIG> is a partial enlarged cross-sectional view taken along the axis x for illustrating a schematic configuration of the sealing device <NUM> according to the second illustrative example. The sealing device <NUM> according to the second illustrative example differs in side lip structure from the sealing device <NUM> described above according to the first illustrative example. Hereinafter, components of the sealing device <NUM> according to the second illustrative example that are identical or similar in function to those of the sealing device <NUM> according to the first illustrative example are assigned the same reference signs, and descriptions thereof are omitted. Parts that differ between the sealing devices will be described.

In the sealing device <NUM>, as illustrated in <FIG>, a side lip <NUM>, which is different from the side lip <NUM> of the sealing device <NUM>, has no groove <NUM> and has a distal end portion <NUM> that differs in shape from the distal end portion <NUM>. The distal end portion <NUM> is formed so as to decrease in thickness as progress toward a middle portion <NUM> side. Specifically, an inner peripheral surface 41a and an outer peripheral surface 41b of the distal end portion <NUM> are not parallel to each other. The inner peripheral surface 41a and the outer peripheral surface 41b are inclined with respect to each other such that a distance between the inner peripheral surface 41a and the outer peripheral surface 41b decreases as progress from a distal end <NUM> toward the middle portion <NUM> side. Thus, a thickness of the distal end portion <NUM> at a connection zone C is smaller than a thickness w1' of the distal end portion <NUM> at the distal end <NUM>. The thickness w1' is, for example, equal to the thickness w1 of the distal end portion <NUM> of the side lip <NUM> of the sealing device <NUM>. In the sealing device <NUM>, a thickness w2' of the middle portion <NUM> and a thickness w3' of a root portion <NUM> are thinner than the thickness w2 of the middle portion <NUM> and the thickness w3 of the root portion <NUM> respectively of the sealing device <NUM>. An angle (a distal end angle θ) formed by the distal end <NUM> of the distal end portion <NUM> is acute. As illustrated in <FIG>, the distal end angle θ is an angle between an outer side surface 41c, a surface of the distal end portion <NUM> on the outer side, and the inner peripheral surface 41a on a cross section along the axis x.

Specifically, as illustrated in <FIG>, an angle (a bend angle y1) between the inner peripheral surface 41a of the distal end portion <NUM> and an inner peripheral surface 32a of the middle portion <NUM> is smaller than a (rear-side) angle (a bend angle γ2) between the outer peripheral surface 41b of the distal end portion <NUM> and an outer peripheral surface 32b of the middle portion <NUM>. In other words, in the sealing device <NUM>, the inner peripheral surface 41a of the distal end portion <NUM> of the side lip <NUM> is inclined more toward the inner periphery side than the inner peripheral surface 31a of the distal end portion <NUM> of the side lip <NUM> of the sealing device <NUM> described above is. In the sealing device <NUM>, the inner peripheral surface 41a of the distal end portion <NUM> may not be inclined more toward the inner periphery side than the inner peripheral surface 31a of the distal end portion <NUM> of the sealing device <NUM> is. In this case, in the sealing device <NUM>, the outer peripheral surface 41b of the distal end portion <NUM> is inclined more toward the outer periphery side than the outer peripheral surface 31b of the distal end portion <NUM> of the sealing device <NUM> is. In <FIG>, the thickness of the distal end portion <NUM> is a width in a direction orthogonal to the inner peripheral surface 41a. However, the thickness of the distal end portion <NUM> may be a width in a direction orthogonal to the outer peripheral surface 41b, or may be a thickness defined by another method.

The inner peripheral surface 41a of the distal end portion <NUM> is a conical or substantially conical surface centered or substantially centered about the axis x. The inner peripheral surface 41a may be a curved surface of other forms, such as a curved surface having a cross-sectional outline that is curved so as to be recessed to the outer periphery side, a curved surface having a cross-sectional outline that is curved so as to project to the inner periphery side, or a curved surface that combines these outlines. Similarly, the outer peripheral surface 41b of the distal end portion <NUM> is a conical or substantially conical surface centered or substantially centered about the axis x. The outer peripheral surface 41b may be a curved surface of other forms, such as a curved surface having a cross-sectional outline that is curved so as to be recessed to the inner periphery side, a curved surface having a cross-sectional outline that is curved so as to project to the outer periphery side, or a curved surface that combines these outlines.

The sealing device <NUM> can produce effects owing to a bend between the distal end portion <NUM> and the middle portion <NUM> of the side lip <NUM> in a similar way that the sealing device <NUM> does as described above owing to a bend between the distal end portion <NUM> and the middle portion <NUM> of the side lip <NUM>. In the side lip <NUM>, the distal end portion <NUM> decreases in thickness as progress toward a root side (from the outer side to the inner side). The middle portion <NUM> and the root portion <NUM> are made thinner, resulting in a reduction in rigidity of both the middle portion <NUM> and the root portion <NUM>. This allows the side lip <NUM> in the usage state to reduce a pressing force put on a deflector <NUM> or a reaction force put by the deflector <NUM> through a zone of contact of the distal end portion <NUM> with the deflector <NUM>. Thus, the sealing device is able to reduce a sliding resistance generated by the contact of the side lip <NUM> with the deflector <NUM> and reduce sliding torque exerted by the side lip <NUM> on an axle <NUM>. On the other hand, the distal end angle θ formed by the distal end <NUM> of the distal end portion <NUM> of the side lip <NUM> is acute. This configuration provides a decrease in the width of contact of the distal end portion <NUM> with the deflector <NUM> and thus can inhibit or prevent a reduced pressing force on the deflector <NUM> or a reduced reaction force put by the deflector <NUM> from causing a reduction in contact pressure at the distal end <NUM>. This can improve sealing performance at the distal end <NUM> of the side lip <NUM> and can improve performance in preventing the entry of foreign matter. In other words, this can inhibit or prevent a reduction in sealing performance at the distal end <NUM> of the side lip <NUM> and can inhibit or prevent a reduction in performance in preventing the entry of foreign matter.

In this way, the sealing device <NUM> according to the second illustrative example is capable of reducing sliding torque caused by the side lip <NUM>.

Next, a sealing device <NUM> according to a first embodiment of the present invention will be described. <FIG> is a partial enlarged cross-sectional view taken along the axis x for illustrating a schematic configuration of the sealing device <NUM> according to the first embodiment of the present invention. The sealing device <NUM> according to the first embodiment of the present invention differs in side lip structure from the sealing device <NUM> described above according to the first illustrative example. Hereinafter, components of the sealing device <NUM> according to the first embodiment of the present invention that are identical or similar in function to those of the sealing device <NUM> according to the first illustrative example are assigned the same reference signs, and descriptions thereof are omitted. Parts that differ between the sealing devices will be described.

In the sealing device <NUM>, as illustrated in <FIG>, a side lip <NUM>, which is different from the side lip <NUM> of the sealing device <NUM>, has a distal end portion <NUM> of a sealing device <NUM> as described above that differs from the distal end portion <NUM>. The distal end portion <NUM> is, as described above, formed so as to decrease in thickness as progress toward a middle portion <NUM> side.

The sealing device <NUM> can produce effects in a similar way that the sealing device <NUM> and the sealing device <NUM> do as described above. Specifically, in the side lip <NUM> of the sealing device <NUM>, the middle portion <NUM> has grooves <NUM>, and the distal end portion <NUM> is bent to the inner periphery side with respect to the middle portion <NUM> and is formed so as to decrease in thickness as progress toward the middle portion <NUM> side. This configuration provides an increase in contact pressure at the distal end portion <NUM> while enabling the side lip <NUM> to be readily bent at the middle portion <NUM>. In other words, this configuration can inhibit or prevent a reduction in contact pressure at the distal end portion <NUM> while enabling the side lip <NUM> to be readily bent at the middle portion <NUM>. As a result, even when the side lip <NUM> contacts a sliding surface <NUM> of a deflector <NUM> at also the middle portion <NUM>, the sealing device is able to prevent a distal end <NUM> of the side lip <NUM> from floating away from the sliding surface <NUM> of the deflector <NUM> and reduce sliding torque exerted by the side lip <NUM> on an axle <NUM>.

Although the embodiments of the present invention have been described above, the present invention is not limited to the sealing device <NUM> according to the embodiment of the present invention, and includes any modes falling within the scope of the claims of the present invention. Respective configurations may be appropriately selectively combined to solve at least part of the above-described problems and achieve at least part of the above-described effects. For example, in the above-described embodiments, the shape, material, arrangement, size and the like of each component can be appropriately changed according to a specific use mode of the present invention.

Claim 1:
A sealing device (<NUM>) for sealing between a through-hole and a shaft inserted through the through-hole, the sealing device comprising:
a reinforcing ring (<NUM>) formed annularly around an axis (x); and
an elastic body part (<NUM>) formed from an elastic body that is attached to the reinforcing ring and that is formed annularly around the axis,
the elastic body part including:
an annular seal lip (<NUM>) for being in contact with the shaft such that the shaft is slidable;
an annular dust lip (<NUM>), the dust lip being provided on an outer side (a) of the seal lip and extending toward the axis; and
an annular side lip (<NUM>), the side lip extending toward the outer side on an outer periphery side (c) of the dust lip,
the side lip having:
an annular middle portion (<NUM>), the middle portion increasing in diameter as progress toward the outer side in a direction of the axis; and
an annular distal end portion (<NUM>), the distal end portion being a portion connected to and on the outer side of the middle portion, the distal end portion increasing in diameter as progress toward the outer side in the direction of the axis,
wherein,
in the side lip, the distal end portion is bent to an inner periphery side (d) from the middle portion,
characterized in that;
the distal end portion of the side lip is formed so as to decrease in thickness as progress toward the middle portion side; and,
in the middle portion, at least one groove (<NUM>) is formed annularly around the axis.