Patent Description:
As a shock absorber used in a vehicle, for example, there is a structure that can be incorporated as one of two shock absorbers forming a front fork of a saddle-ride type vehicle on which an occupant rides. Such a shock absorber is known, for example, from Patent Literature <NUM>.

The shock absorber known in Patent Literature <NUM> has an outer tube, an inner tube fitted to the outer tube so that one end portion thereof can move forward and backward, a cylinder extending from the outer tube into the inner tube, a rod extending from the other end of the inner tube into the cylinder, and a piston provided on the rod as a basic structure.

This shock absorber is a kind of air spring type shock absorber which has two gas chambers with a piston as a boundary. A first gas chamber is a space where the inside of the cylinder is divided by the piston. A second gas chamber is a space outside the cylinder in a space surrounded by the outer tube and the inner tube. Therefore, the shock absorber functions as a suspension spring which elastically supports the vehicle body by the reaction force balance between an air spring by air enclosed in the first gas chamber and an air spring by air enclosed in the second gas chamber.

A first seal member, a second seal member, a third seal member, and a piston ring are provided in this order from a side closest to the first gas chamber to a far side on an outer peripheral surface of the piston. Respective sealing lips of the three seal members are slidably in contact with an inner peripheral surface of the cylinder. Three sealing members seal between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder.

When the piston performs a compression operation, the sealing lip of each seal member slides on the inner peripheral surface of the cylinder. Here, "compression operation" means that the piston moves in an approach direction (direction in which the air in the first gas chamber is compressed) with respect to the cylinder.

The sealing lip of the first seal member faces the first gas chamber. On the other hand, the sealing lips of the second and third seal members face away from the first gas chamber. Therefore, the second and third seal members can prevent abrasion powder of a piston ring from entering the first seal member.

Patent Literature <NUM> shows a suspension device for a vehicle comprising an upper side chamber of a first air spring positioned on the left side connected to a lower air chamber of a second air spring positioned on the right side through a supply air pressure supply/discharge pipe, an upper air chamber of the second air spring <NUM>' connected to a lower air chamber of the first air spring through a supply air pressure supply/discharge pipe.

Patent Literature <NUM> shows an air spring with a cylindrical body having upper and lower telescopic sleeves, and having a piston connected to or movable with one sleeve and slidingly engaging the other sleeve forming a main pressure chamber on one side of the piston, and a separate chamber on the opposite side of the piston, each of said chambers adapted to contain air and oil, and a packing carried by said piston including a plurality of flexible packing elements, one having its marginal portion turned upward, and another having its marginal portion turned downward.

However, in the shock absorber known from Patent Literature <NUM>, the first gas chamber has an oilless structure that is not filled with oil. The piston part is also almost oilless. In this way, even when the shock absorber is oilless and has a configuration in which the sealing lip slides on the inner peripheral surface of the cylinder, it has been required to secure the reaction force balance between the air springs to further enhance the steering stability and riding comfort of the vehicle.

An object of the invention is to provide a technology which can enhance the steering stability and riding comfort of a vehicle even when a gas chamber and a piston part are oilless in a shock absorber which can be adopted in the vehicle.

According to the invention, there is provided a shock absorber which includes,.

According to the invention, the lubricating member is provided on a side closest to the gas chamber in the outer peripheral surface of the piston. When the piston performs a compression operation, the lubricating member first slides on the inner peripheral surface of the cylinder along with the piston to apply a lubricating film to the inner peripheral surface (lubricate the sliding surface). Immediately after that, the sealing lips of the first seal member and the second seal member slide on the inner peripheral surface of the cylinder. That is, each sealing lip slides on the lubricating film.

Despite the oilless configuration of the gas chamber and the piston part, the sliding of each sealing lip against the inner peripheral surface of the cylinder is smooth. Therefore, the durability and sealability of each seal member can be improved. Since the piston can be operated smoothly with respect to the cylinder, as a result, the operation performance of the shock absorber can be improved. Since the shock absorber operates more smoothly, it is possible to further enhance the steering stability and riding comfort of the vehicle.

A mode for carrying out the invention will be described below with reference to the accompanying drawings.

A front fork <NUM> according to a first example and shock absorbers <NUM> and <NUM> used for the front fork <NUM> will be described with reference to <FIG>.

As illustrated in <FIG>, the front fork <NUM> is used, for example, in a vehicle, and is used in, for example, a motorcycle which is a kind of saddle-ride type vehicle on which an occupant rides. The front fork <NUM> has two shock absorbers <NUM> and <NUM> which are arranged parallel to each other and vertically.

One <NUM> of the two shock absorbers <NUM> and <NUM> is the shock absorber <NUM> with a damping force generating unit which has two damping force generating units <NUM> and <NUM> by hydraulic pressure built therein. The other <NUM> of the two shock absorbers <NUM> and <NUM> is the air spring type shock absorber <NUM> which does not have a damping force generating unit, but has a first gas chamber <NUM>, a second gas chamber <NUM>, and a first spring <NUM>. That is, the shock absorber <NUM> (air spring type shock absorber <NUM>) has a structure that can be incorporated as one of the two shock absorbers <NUM> and <NUM> which form the front fork <NUM> of the saddle-ride type vehicle.

First, the shock absorber <NUM> with the damping force generating unit will be described. Since the shock absorber <NUM> with the damping force generating unit has a known structure, only the outline will be described. As illustrated in <FIG>, the shock absorber <NUM> with the damping force generating unit includes a cylindrical outer tube <NUM> extending in a vertical direction, an inner tube <NUM> fitted to the outer tube <NUM> such that the upper half thereof can move forward and backward, a cylinder <NUM> extending from an upper end of the outer tube <NUM> into the inner tube <NUM>, a rod <NUM> extending from a lower end portion 22a of the inner tube <NUM> into the cylinder <NUM>, and a piston <NUM> provided on the rod <NUM> as basic components. As described above, the shock absorber <NUM> with the damping force generating unit has a telescopic type structure in which the inner tube <NUM> can be moved forward and backward with respect to the outer tube <NUM>.

More specifically, the upper end of the outer tube <NUM> is closed. The lower end of the inner tube <NUM> is closed by a bottom bolt <NUM> and is connected to a wheel side bracket <NUM>. The upper end of the cylinder <NUM> is fixed to the upper end of the outer tube <NUM> and is closed by a fork bolt <NUM>. The lower end portion of the rod <NUM> is connected to the lower end portion 22a of the inner tube <NUM> via the bottom bolt <NUM> and the wheel side bracket <NUM>. The piston <NUM> divides the inside of the cylinder <NUM> into a piston-side oil chamber <NUM> and a rod side oil chamber <NUM>. The piston-side oil chamber <NUM> is located in the upper half of the cylinder <NUM>. The outer tube <NUM> and the inner tube <NUM> are biased in an extension direction by a compression coil spring <NUM>.

The first damping force generating unit <NUM> is configured with the cylinder <NUM>, the rod <NUM>, and the piston <NUM>. The second damping force generating unit <NUM> is provided on the upper portion of the outer tube <NUM>. Lubricating oil J1 is stored in a lower portion of the inner tube <NUM>. In a space surrounded by the outer tube <NUM> and the inner tube <NUM>, a space outside the cylinder <NUM> and above the oil level of the lubricating oil J1 forms a gas chamber <NUM>. The air enclosed in the gas chamber <NUM> has the function of an air spring.

The first damping force generating unit <NUM> and the second damping force generating unit <NUM> generate a damping force for damping the expansion and contraction vibration of a compression coil spring <NUM> of the shock absorber <NUM> with the damping force generating unit, an air spring of the gas chamber <NUM>, the air spring of the air spring type shock absorber <NUM>, and the first spring <NUM> (compression coil spring <NUM>) due to the respective elastic forces.

Next, the air spring type shock absorber <NUM> will be described. As illustrated in <FIG> and <FIG>, the air spring type shock absorber <NUM> includes the outer tube <NUM>, the inner tube <NUM>, the cylinder <NUM>, the rod <NUM>, and the piston <NUM> as basic constituent elements. That is, this air spring type shock absorber <NUM> has a telescopic type configuration in which the inner tube <NUM> can be moved forward and backward with respect to the outer tube <NUM>.

The outer tube <NUM> (first tube <NUM>) is a cylindrical member which extends in the vertical direction and has its upper end closed. That is, the outer tube <NUM> has the upper end (one end) as a closed end 101a and the lower end (the other end) as an open end 101b.

The inner tube <NUM> (second tube <NUM>) is fitted in the outer tube <NUM> such that the upper half thereof can move forward and backward. The lower end of the inner tube <NUM> is connected to the wheel side bracket <NUM> and is closed by a removable bottom bolt <NUM>.

The cylinder <NUM> is provided inside the outer tube <NUM> and extends from the closed end 101a of the outer tube <NUM> into the inner tube <NUM>. More specifically, the cylinder <NUM> has a cylindrical shape whose upper end is closed by a removable fork bolt <NUM> and is fixed to the closed end 101a of the outer tube <NUM>.

An annular connecting member <NUM> is provided at the lower end portion of the cylinder <NUM>. The connecting member <NUM> is provided with a guide holder <NUM> extending downward. The guide holder <NUM> is a pipe having a diameter smaller than that of the cylinder <NUM> and has an annular holder portion <NUM> at the bottom.

The rod <NUM> extends from a lower end portion 102a of the inner tube <NUM> into the cylinder <NUM>. More specifically, a lower end portion 104a of the rod <NUM> is connected to the lower end portion 102a of the inner tube <NUM> via the bottom bolt <NUM> and the wheel side bracket <NUM>. The rod <NUM> is slidably supported by the holder portion <NUM>. An upper end portion 104b of the rod <NUM> is located above the holder portion <NUM>. A pipe-shaped piston holder <NUM> is provided on the upper end portion 104b. Specifically, the inner peripheral surface of the piston holder <NUM> is fitted and fixed to the upper end portion 104b.

The piston <NUM> is located inside the cylinder <NUM> and above the connecting member <NUM>. The piston <NUM> is provided on the rod <NUM> and divides the inside of the cylinder <NUM> to form a gas chamber <NUM>. Specifically, a shaft 105a extends downward from the lower end of the piston <NUM>. The shaft 105a is fitted and fixed in the piston holder <NUM>. As a result, the piston <NUM> is provided on the upper end portion 104b of the rod <NUM>. The gas chamber <NUM> is a space surrounded by the inside of the upper half of the cylinder <NUM> closed by the fork bolt <NUM> and the piston <NUM>. Hereinafter, the gas chamber <NUM> will be appropriately referred to as the "first gas chamber <NUM>" or the "inner air spring chamber <NUM>".

Lubricating oil J2 is stored in the lower portion of the inner tube <NUM>. In a space surrounded by the outer tube <NUM> and the inner tube <NUM>, a space outside the cylinder <NUM> and above the oil level of the lubricating oil J2 forms a gas chamber <NUM>. Hereinafter, the gas chamber <NUM> will be appropriately referred to as the "second gas chamber <NUM>" or the "outer air spring chamber <NUM>".

Compressed air is enclosed in the first gas chamber <NUM> and the second gas chamber <NUM>. The pressure of the first gas chamber <NUM> is set higher than the pressure of the second gas chamber <NUM>. The pressure of the second gas chamber <NUM> is almost atmospheric pressure. However, the second gas chamber <NUM> may be pressurized if necessary.

The air trapped in the first gas chamber <NUM> and the second gas chamber <NUM> has the function of an air spring. The compressed air in the first gas chamber <NUM> and the second gas chamber <NUM> functions as an air spring which exerts a reaction force according to the amount of compression of the outer tube <NUM> and the inner tube <NUM> in a longitudinal direction. This air spring functions as a suspension spring which elastically supports the vehicle body by constantly urging the outer tube <NUM> and the inner tube <NUM> in the extension direction. The amount of compression of the outer tube <NUM> and the inner tube <NUM> in the longitudinal direction is equal to the amount of compression of the air spring type shock absorber <NUM>. The air spring exerts a reaction force according to the compression amount of the air spring type shock absorber <NUM> and urges the air spring type shock absorber <NUM> in the extension direction.

The outer tube <NUM> and the inner tube <NUM> are biased in the extension direction by the first spring <NUM>. The first spring <NUM> is composed of a compression coil spring built in the inner tube <NUM>. The function of the air spring by the compressed air in the first gas chamber <NUM> and the second gas chamber <NUM> and the biasing force of the first spring <NUM> can absorb the impact force that the vehicle receives from the road surface.

A second spring <NUM> (balance spring <NUM>) made of compression coil spring is interposed between the upper end surface of the connecting member <NUM> and the lower end surface of the piston <NUM>. A space <NUM> (spring chamber <NUM>) in which the second spring <NUM> is housed in the cylinder <NUM> communicates with the second gas chamber <NUM>. A third spring <NUM> (rebound spring <NUM>) made of compression coil spring is interposed between the upper end surface of the holder portion <NUM> and the lower end surface of the piston holder <NUM>.

As is clear from the above description, the air spring type shock absorber <NUM> includes,.

Next, a seal structure between an inner peripheral surface 103a of the cylinder <NUM> and an outer peripheral surface 105b of the piston <NUM> will be described with reference to <FIG> and <FIG>. A lubricating member <NUM>, a first seal member <NUM>, a second seal member <NUM>, and a piston ring <NUM> are provided on the outer peripheral surface 105b of the piston <NUM> in this order from the first gas chamber <NUM> side toward the second gas chamber <NUM> side. The lubricating member <NUM>, the first seal member <NUM>, the second seal member <NUM>, and the piston ring <NUM> can be in sliding contact with the inner peripheral surface 103a of the cylinder <NUM>.

Hereinafter, the lubricating member <NUM> will be referred to as "first lubricating member <NUM>" as appropriate. The first lubricating member <NUM> is provided in a portion of the outer peripheral surface 105b of the piston <NUM> closest to the first gas chamber <NUM>, that is, a portion closest to an end surface 105c in an advancing direction of the piston <NUM> with respect to the cylinder <NUM>. The first lubricating member <NUM> is a member containing a lubricant such as lubricating oil and slidably in contact with the inner peripheral surface 103a of the cylinder <NUM>. More specifically, the first lubricating member <NUM> is a ring-shaped member obtained by impregnating a material (for example, felt or non-woven fabric) having a high impregnation property with a lubricant with the lubricant. By sliding the first lubricating member <NUM> on the inner peripheral surface 103a of the cylinder <NUM>, a film of the lubricant can be applied to the inner peripheral surface 103a.

The first seal member <NUM> is provided at a position farther from the gas chamber <NUM> (first gas chamber <NUM>) than the first lubricating member <NUM>. A sealing lip 152a of the first seal member <NUM> faces the first gas chamber <NUM> and is slidably in contact with the inner peripheral surface 103a of the cylinder <NUM>. The first seal member <NUM> can enhance the airtightness of the first gas chamber <NUM>.

The second seal member <NUM> is provided at a position farther from the gas chamber <NUM> (first gas chamber <NUM>) than the first seal member <NUM>. A sealing lip 153a of the second seal member <NUM> is in an opposite direction to the first gas chamber <NUM> and slidably contacts the inner peripheral surface 103a of the cylinder <NUM>. The second seal member <NUM> can enhance the airtightness of the second gas chamber <NUM> and the second spring chamber <NUM>.

In this way, the first seal member <NUM> and the second seal member <NUM> enhance the sealability between the inner peripheral surface 103a of the cylinder <NUM> and the outer peripheral surface 105b of the piston <NUM>. Therefore, the function of the air springs (first air spring and second air spring) due to the compressed air in the first gas chamber <NUM> and the second gas chamber <NUM> can be maintained. Moreover, even when abrasion powder of the piston ring <NUM> is generated by sliding the piston ring <NUM> on the inner peripheral surface 103a of the cylinder <NUM>, the second seal member <NUM> can prevent the abrasion powder from entering the inside of the first gas chamber <NUM>.

The above description is summarized as follows. As illustrated in <FIG>, the shock absorber <NUM> (air spring type shock absorber <NUM>) of the first example includes,.

As described above, in the outer peripheral surface 105b of the piston <NUM>, the first lubricating member <NUM> is provided on the side closest to the first gas chamber <NUM>. When the piston <NUM> performs compression operation, the first lubricating member <NUM> first slides on the inner peripheral surface 103a of the cylinder <NUM> together with the piston <NUM> to apply a lubricating film to the inner peripheral surface 103a (lubricate the sliding surface). Immediately thereafter, the sealing lips 152a and 153a of the first seal member <NUM> and the second seal member <NUM> slide on the inner peripheral surface 103a of the cylinder <NUM>. That is, respective sealing lips 152a and 153a slide on the lubricating film.

Although the first gas chamber <NUM> and the piston <NUM> have an oilless structure, the sliding of the sealing lips 152a, 153a with respect to the inner peripheral surface 103a of the cylinder <NUM> is smooth. Therefore, it is possible to improve the durability and sealing performance of the respective seal members <NUM> and <NUM>. Since the piston <NUM> can be operated smoothly with respect to the cylinder <NUM>, the operation performance of the shock absorber <NUM> can be improved as a result. Since the shock absorber <NUM> operates more smoothly, it is possible to further enhance the steering stability and riding comfort of the vehicle.

In particular, smoothing the compression operation of the piston <NUM> can be an important factor in enhancing the riding comfort of the vehicle. In order to increase the airtightness of the gas chamber <NUM>, the sealing lip 152a of the first seal member <NUM> faces the gas chamber <NUM> side. Since the sealing lip 152a of the first seal member <NUM> slides on the inner peripheral surface 103a after the lubricating film is applied by the first lubricating member <NUM>, the sealing lip 152a can slide smoothly. Therefore, the riding comfort of the vehicle can be improved.

In addition, since the first gas chamber <NUM> and the piston <NUM> can be made oilless, the weight of the shock absorber <NUM> can be reduced and the maintenance of the shock absorber <NUM> is easy.

Furthermore, the shock absorber <NUM> (air spring type shock absorber <NUM>) of the first example is a so-called hybrid shock absorber combining an air spring and a mechanical spring, which includes,.

As described above, the lubricating oil is not stored inside the first gas chamber <NUM>. Here, it is assumed that lubricating oil comes out of the first gas chamber <NUM> when the fork bolt <NUM> is removed from the upper end of the cylinder <NUM> and the shock absorber <NUM> is turned upside down. In this case, the lubricating oil J2 stored in the lower portion of the inner tube <NUM> has leaked from between the inner peripheral surface 103a of the cylinder <NUM> and the first and second seal members <NUM> and <NUM>. Therefore, it can be easily determined that at least one of the first seal member <NUM> and the second seal member <NUM> is damaged.

Next, a modification example (a modified piston seal structure) of the seal structure between the inner peripheral surface 103a of the cylinder <NUM> and the outer peripheral surface 105b of the piston <NUM> will be described with reference to <FIG>. The modified piston seal structure is characterized in that a second lubricating member <NUM> is added to the seal structure illustrated in <FIG> and <FIG>, and since the other configurations are the same as those in the first embodiment, the description thereof will be omitted.

More specifically, the outer peripheral surface 105b of the piston <NUM> is provided with the second lubricating member <NUM> between the first seal member <NUM> and the second seal member <NUM>. Since the second lubricating member <NUM> has the same structure as the first lubricating member <NUM>, the description thereof will be omitted.

Thus, the shock absorber <NUM> (air spring type shock absorber <NUM>) further includes,
a second lubricating member <NUM>, which is provided between the first seal member <NUM> and the second seal member <NUM> in the outer peripheral surface 105b of the piston <NUM> so as to be capable of sliding contact with the inner peripheral surface 103a of the cylinder <NUM> and, which contains a lubricant.

Therefore, when the piston <NUM> reciprocates, the inner peripheral surface 103a of the cylinder <NUM> can be lubricated not only by the first lubricating member <NUM> but also by the second lubricating member <NUM>. Therefore, the sliding of respective sealing lips 152a and 153a of the first seal member <NUM> and the second seal member <NUM> with respect to the inner peripheral surface 103a of the cylinder <NUM> can be made even smoother.

Next, a seal structure between an inner peripheral surface 101c of the outer tube <NUM> and an outer peripheral surface 102b of the inner tube <NUM> will be described with reference to <FIG>, <FIG>, and <FIG>. On the inner peripheral surface 101c of the outer tube <NUM>, a first outer seal member <NUM>, an outer lubricating member <NUM>, a second outer seal member <NUM>, and a bush <NUM> are provided from the open end 101b to the closed end 101a side of the outer tube <NUM> (see <FIG>) in this order. The first outer seal member <NUM>, the outer lubricating member <NUM>, and the second outer seal member <NUM> can be in sliding contact with the outer peripheral surface 102b of the inner tube <NUM>.

In this way, the two seal members <NUM> and <NUM> and the one lubricating member <NUM> are located further on the radially outer side than the piston <NUM> and are provided on the inner peripheral surface 101c of the outer tube <NUM>. Therefore, the names of those members <NUM>, <NUM>, and <NUM> are given "outer" and they are respectively referred to as the first outer seal member <NUM>, the outer lubricating member <NUM>, and the second outer seal member <NUM>.

The first outer seal member <NUM> is provided at the open end 101b in the inner peripheral surface 101c of the outer tube <NUM>. A sealing lip 161a of the first outer seal member <NUM> faces the outer side in the longitudinal direction of the outer tube <NUM> and is slidably in contact with the outer peripheral surface 102b of the inner tube <NUM>. The first outer seal member <NUM> can prevent dust from entering the outer tube <NUM> from the outside.

The outer lubricating member <NUM> is provided closer to the closed end 101a side than the first outer seal member <NUM> in the inner peripheral surface 101c of the outer tube <NUM> and slidably in contact with the outer peripheral surface 102b of the inner tube <NUM>. More specifically, as similar to the first lubricating member <NUM>, the outer lubricating member <NUM> is a ring-shaped member obtained by impregnating a material (for example, felt or non-woven fabric) having a high impregnation property with a lubricant with the lubricant. By the outer lubricating member <NUM> sliding on the outer peripheral surface 102b of the inner tube <NUM>, a lubricant film can be applied to the outer peripheral surface 102b.

The second outer seal member <NUM> is provided closer to the closed end 101a side than the outer lubricating member <NUM> in the inner peripheral surface 101c of the outer tube <NUM> and slidably in contact with the outer peripheral surface 102b of the inner tube <NUM>. A sealing lip 163a of the second outer seal member <NUM> has a so-called double lip structure which faces both sides in the longitudinal direction of the inner tube <NUM>. The second outer seal member <NUM> can prevent dust from entering the outer tube <NUM> from the outside and enhance the airtightness of the second gas chamber <NUM>.

The bush <NUM> slidably supports the outer peripheral surface 102b of the inner tube <NUM>.

Thus, the shock absorber <NUM> (air spring type shock absorber <NUM>) further includes,.

Since the first outer seal member <NUM> is located at the open end 101b of the outer tube <NUM>, it functions as a dust seal. The second outer seal member <NUM> functions as an air seal between the outer tube <NUM> and the inner tube <NUM>. The outer peripheral surface 102b of the inner tube <NUM> is in a relatively dry state without a lubricating film.

On the other hand, when the outer tube <NUM> and the inner tube <NUM> expand and contract with each other, the outer lubricating member <NUM> slides on the outer peripheral surface 102b of the inner tube <NUM>, and thus a lubricating film is applied to the outer peripheral surface 102b (lubricate the sliding surface). Immediately after that, the sealing lip 161a of the first outer seal member <NUM> and the sealing lip 163a of the second outer seal member <NUM> slide on the outer peripheral surface 102b of the inner tube <NUM>. That is, each sealing lip 161a and 163a slides on the lubricating film.

The sliding of respective sealing lips 161a and 163a with respect to the outer peripheral surface 102b of the inner tube <NUM> is smooth. It is possible to enhance the durability and sealing performance of respective seal members <NUM> and <NUM>. Since the expansion and contraction operation of the outer tube <NUM> and the inner tube <NUM> can be made smooth, as a result, the operation performance of the shock absorber <NUM> can be improved. Since the shock absorber <NUM> operates more smoothly, it is possible to further enhance the steering stability and riding comfort of the vehicle.

A shock absorber <NUM> (air spring type shock absorber <NUM>) according to a second example will be described with reference to <FIG> and <FIG>. An air spring type shock absorber <NUM> of the second example does not have a member corresponding to the first spring <NUM> (see <FIG>) in contrast to the air spring type shock absorber <NUM> of the first example illustrated in <FIG>. That is, the air spring type shock absorber <NUM> is characterized in that it functions as a suspension spring which elastically supports the vehicle body only by the function of the air spring by the air enclosed in a first gas chamber <NUM> and a second gas chamber <NUM>.

In this way, the air spring type shock absorber <NUM> of the second example has the same basic configuration as the air spring type shock absorber <NUM> of the first embodiment except that it does not have a member corresponding to the first spring <NUM>. Therefore, with respect to the constituent elements of the air spring type shock absorber <NUM> of the first example, the constituent elements substantially equivalent are replaced with the reference numerals in the <NUM> series to the reference numerals in the <NUM> series, and detailed description thereof will be omitted.

The air spring type shock absorber <NUM> has an outer tube <NUM> (first tube <NUM>), an inner tube <NUM> (second tube <NUM>), a cylinder <NUM>, a rod <NUM>, and a piston <NUM> as basic constituent elements.

The outer tube <NUM> is a cylindrical member which extends vertically and has its upper end closed.

The inner tube <NUM> is fitted in the outer tube <NUM> such that the upper half of the inner tube <NUM> can move forward and backward. The lower end of the inner tube <NUM> is connected to the wheel side bracket <NUM> and is closed by a removable bottom bolt <NUM>.

The cylinder <NUM> is provided inside the outer tube <NUM> and extends from an upper end 201a (closed end 201a) of the outer tube <NUM> into the inner tube <NUM>. The cylinder <NUM> has its upper end closed by a removable fork bolt <NUM> and is fixed to the closed end 201a of the outer tube <NUM>. An annular holder portion <NUM> is provided at the lower end of the cylinder <NUM>.

The rod <NUM> extends from a lower end portion 202a of the inner tube <NUM> into the cylinder <NUM>. More specifically, a lower end portion 204a of the rod <NUM> is connected to the lower end portion 202a of the inner tube <NUM> via a bottom bolt <NUM> and a wheel side bracket <NUM>. The upper end portion of the rod <NUM> is located above the holder portion <NUM> and is slidably supported by the holder portion <NUM>.

The piston <NUM> is located above the holder portion <NUM> inside the cylinder <NUM>. The piston <NUM> is provided on the upper end of the rod <NUM> and divides the inside of the cylinder <NUM> to form a gas chamber <NUM>. The gas chamber <NUM> is a space surrounded by the inside of the upper half of the cylinder <NUM> closed by the fork bolt <NUM> and the piston <NUM>. Hereinafter, the gas chamber <NUM> will be referred to as "first gas chamber <NUM>" or "inner air spring chamber <NUM>" as appropriate.

Lubricating oil J2 is stored in the lower portion of the inner tube <NUM>. In a space surrounded by the outer tube <NUM> and the inner tube <NUM>, a space outside the cylinder <NUM> and above the oil level of the lubricating oil J2 forms a gas chamber <NUM>. Hereinafter, the gas chamber <NUM> will be referred to as "second gas chamber <NUM>" or "outer air spring chamber <NUM>" as appropriate.

Compressed air is enclosed in the first gas chamber <NUM> and the second gas chamber <NUM>. The enclosed air has a function of an air spring (first air spring and second air spring). The air spring functions as a suspension spring which elastically supports the vehicle body by constantly urging the outer tube <NUM> and the inner tube <NUM> in the extension direction.

A balance spring <NUM> is interposed in the space surrounded by the outer tube <NUM> and the inner tube <NUM>. A rebound spring <NUM> is interposed between a lower end surface of the piston <NUM> and an upper end surface of the holder portion <NUM>. A space 203b which contains the rebound spring <NUM> in the cylinder <NUM> communicates with the second gas chamber <NUM> via one or both of a communication hole 203c formed in the cylinder <NUM> and a communication hole 223a formed in the holder portion <NUM>.

A first lubricating member <NUM>, a first seal member <NUM>, a second seal member <NUM>, and a piston ring <NUM> are provided on an outer peripheral surface 205b of the piston <NUM> in this order from the first gas chamber <NUM> side to the second gas chamber <NUM> side. Each of the members <NUM>, <NUM>, <NUM>, and <NUM> can be in sliding contact with an inner peripheral surface 203a of the cylinder <NUM>.

The first lubricating member <NUM> is provided at a portion (a portion closest to the end surface 205c of the piston <NUM>) of the outer peripheral surface 205b of the piston <NUM> closest to the first gas chamber <NUM>. The first seal member <NUM> is provided at a position farther from the first gas chamber <NUM> than the first lubricating member <NUM>. A sealing lip 252a of the first seal member <NUM> faces the first gas chamber <NUM>. The second seal member <NUM> is provided at a position farther from the first gas chamber <NUM> than the first seal member <NUM>. A sealing lip 253a of the second seal member <NUM> is opposite to the first gas chamber <NUM>.

Furthermore , a second lubricating member (corresponding to the second lubricated member <NUM> illustrated in <FIG>) is provided between the first seal member <NUM> and the second seal member <NUM> on the outer peripheral surface 205b of the piston <NUM>.

On an inner peripheral surface 201c of the outer tube <NUM>, a first outer seal member <NUM>, an outer lubricating member <NUM>, a second outer seal member <NUM>, and a bush <NUM> are provided in this order from an open end 201b of the outer tube <NUM> toward the closed end 201a. The respective members <NUM>, <NUM>, <NUM>, and <NUM> can be in sliding contact with an outer peripheral surface 202b of the inner tube <NUM>.

The first outer seal member <NUM> is provided at the open end 201b in the inner peripheral surface 201c of the outer tube <NUM>. A sealing lip 261a of the first outer seal member <NUM> faces the outer side in the longitudinal direction of the outer tube <NUM>. The outer lubricating member <NUM> is provided closer to the closed end 201a than the first outer seal member <NUM> in the inner peripheral surface 201c of the outer tube <NUM>. The second outer seal member <NUM> is provided closer to the closed end 201a side than the outer lubricating member <NUM> in the inner peripheral surface 201c of the outer tube <NUM>. A sealing lip 263a of the second outer seal member <NUM> faces both sides in the longitudinal direction of the inner tube <NUM>. The bush <NUM> slidably supports the outer peripheral surface 202b of the inner tube <NUM>.

The operation and effect of the air spring type shock absorber <NUM> of the second example are basically the same as those of the air spring type shock absorber <NUM> of the first example except for the operation by the first spring <NUM> (see <FIG>), and thus description thereof will be omitted.

The front fork <NUM> (including the shock absorbers <NUM>, <NUM>, and <NUM>) according to the invention is not limited to the examples as long as the effects and advantages of the invention are exhibited. For example, in the invention, the front fork <NUM> may be adopted in a vehicle. Further, the front fork <NUM> can also be used in a motor tricycle of a saddle-ride type vehicle.

Claim 1:
A shock absorber (<NUM>), comprising:
a cylindrical outer tube (<NUM>) with one end as a closed end and the other end as an open end;
an inner tube (<NUM>) partially fitted to the outer tube (<NUM>) so as to be able to move forward and backward;
a cylinder (<NUM>) provided inside the outer tube (<NUM>) and extending inside the inner tube (<NUM>);
a rod (<NUM>) extending from an end portion of the inner tube (<NUM>) exposed from the outer tube (<NUM>) to an inside of the cylinder (<NUM>);
a piston (<NUM>) which is provided on the rod (<NUM>) and divides the inside of the cylinder (<NUM>) to form a gas chamber (<NUM>);
a first lubricating member (<NUM>), which is provided on a side closest to the gas chamber (<NUM>) in an outer peripheral surface of the piston (<NUM>) so as to be capable of sliding contact with an inner peripheral surface of the cylinder (<NUM>), and which contains a lubricant;
a first seal member (<NUM>), which is provided at a position farther from the gas chamber (<NUM>) than the first lubricating member (<NUM>) in an outer peripheral surface of the piston (<NUM>), and in which a sealing lip (152a) slidably in contact with the inner peripheral surface of the cylinder (<NUM>) faces the gas chamber (<NUM>);
a second seal member (<NUM>), which is provided at a position farther from the gas chamber (<NUM>) than the first seal member (<NUM>) in the outer peripheral surface of the piston (<NUM>), and in which a sealing lip (153a) slidably in contact with the inner peripheral surface of the cylinder (<NUM>) is directed opposite to the gas chamber (<NUM>);
characterized by
a second lubricating member (<NUM>), which is provided between the first seal member (<NUM>) and the second seal member (<NUM>) in the outer peripheral surface of the piston (<NUM>) so as to be capable of sliding contact with the inner peripheral surface of the cylinder (<NUM>) and, which contains a lubricant.