Patent Description:
For maintaining sealability for a long period of time in a mechanical seal as one example of a sliding member, there is the technique of satisfying both of conflicting conditions of "sealing" and "lubrication. " For example, a technique has been known, in which at a pair of sliding members sliding relative to each other, a positive pressure generation groove is provided on a sealed fluid side of one sliding face and a negative pressure generation groove is provided on a leakage side, and each of the positive pressure generation groove and the negative pressure generation groove is communicated with the sealed fluid side and is separated from the leakage side by a seal face (see, e.g., <CIT>).

When the sliding members with the above-described configuration slide relative to each other, the sliding faces are pushed out by a positive pressure generated by the positive pressure generation groove provided on the sealed fluid side, and a fluid lubrication state in which a liquid film is interposed between the sliding faces is brought. Thus, sliding torque can be reduced. Moreover, pumping action for sucking fluid into a portion between the sliding faces from the leakage side is caused utilizing a negative pressure generated by the negative pressure generation groove provided on the leakage side, and therefore, a leakage amount can be extremely small. <CIT> discloses a sliding component having many features of claim <NUM>. <CIT>, <CIT> and <CIT> / <CIT> disclose further prior art.

However, in the above-described technique, the positive pressure generation groove needs to be provided on the sealed fluid side of the sliding face, and the negative pressure generation groove needs to be provided on the leakage side. This leads to a problem that a sliding face component is increased in size.

The present invention is intended to provide a compact sliding member configured so that sliding torque can be reduced and a sealing function can be maintained.

The above problem is solved by a pair of sliding members according to claim <NUM>. According to the invention, the sliding member is characterized by.

Accordingly, cavitation occurs due to pressure reduction in the negative pressure generation mechanism, and liquid is evaporated inside the cavitation and the cavitation is filled with gas with a small viscosity. Thus, sliding torque of the sliding member can be reduced. Moreover, a positive pressure is generated by a wedge effect of the land portion arranged in the negative pressure generation mechanism, and therefore, the sliding faces can be pushed out and fluid can be interposed between the sliding faces. Thus, the sliding torque can be further reduced. In addition, fluid is sucked into a portion between the sliding faces from the leakage side by means of a negative pressure generated by the negative pressure generation mechanism, and therefore, a leakage amount can be extremely small. Sliding torque reduction and sealability improvement as conflicting performances can be accomplished by the single negative pressure generation mechanism without the need for separately providing a positive pressure generation mechanism and a negative pressure generation mechanism as in a typical technique, and therefore, the sliding member can be compactified.

According to the invention, the land portion arranged in the negative pressure generation mechanism is surrounded by the negative pressure generation mechanism and is formed in an island shape.

Accordingly, the vicinity of the island-shaped land portion serves as a positive pressure region to exert a fluid lubrication function to reduce the sliding torque, and a portion apart from the island-shaped land portion serves as a gas phase region as a cavitation region to accomplish sliding torque reduction and sealability improvement by pumping action. Thus, sliding torque reduction and sealability improvement as the conflicting performances can be accomplished by the single negative pressure generation mechanism without the need for separately providing a positive pressure generation mechanism and a negative pressure generation mechanism.

According to the invention, the negative pressure generation mechanism includes a guide groove extending from a leakage side toward the land portion arranged in the negative pressure generation mechanism.

Accordingly, fluid in the negative pressure generation mechanism is efficiently guided from the leakage side to the land portion arranged in the negative pressure generation mechanism by the guide groove, and is held back by the land portion to generate the positive pressure. Thus, the sliding torque can be reduced.

Preferably, the negative pressure generation mechanism includes a guide groove extending from each of the leakage side and a sealed fluid side toward the land portion arranged in the negative pressure generation mechanism.

Accordingly, fluid in the negative pressure generation mechanism is efficiently guided from the leakage side and the sealed fluid side to the land portion arranged in the negative pressure generation mechanism by the guide groove, and is held back by the land portion to generate the positive pressure. Thus, the sliding torque can be reduced.

Preferably, the negative pressure generation mechanism includes a portion remaining after the land portion has been removed from the sliding face.

Accordingly, the negative pressure generation mechanism includes the portion remaining after the land portion has been removed from the sliding face. Thus, the area of the negative pressure generation mechanism can be large, and therefore, the area of contact between gas with a small viscosity and the sliding face can be large. Consequently, the sliding torque can be reduced.

Preferably, the negative pressure generation mechanism is arranged across the average diameter of the sliding face.

Accordingly, the negative pressure generation mechanism is arranged across both sides of the average diameter of the sliding face. Thus, the area of the negative pressure generation mechanism can be large, and therefore, the area of contact between gas with a small viscosity and the sliding face can be large. Consequently, the sliding torque can be reduced.

Preferably, the negative pressure generation mechanism includes a fluid introduction groove communicated with the sealed fluid side and a groove portion having an opening communicated with the fluid introduction groove on a downstream side and a dead end portion surrounded by the land portion on an upstream side.

Accordingly, the negative pressure generation mechanism can be easily formed.

Preferably, the land portion surrounding the dead end portion includes a positive pressure generation mechanism having an opening communicated with the fluid introduction groove.

Accordingly, even when a fluid lubrication state at, e.g., start-up timing is not sufficiently brought, the positive pressure generation mechanism can generate the positive pressure to maintain the fluid lubrication state.

Preferably, the negative pressure generation mechanism includes multiple negative pressure generation mechanisms arranged at the sliding face.

Accordingly, the negative pressure generation mechanism and the land portion can be optimally arranged according to the size of the sliding face.

Preferably, the land portion arranged in the negative pressure generation mechanism includes multiple land portions arranged in the negative pressure generation mechanism.

Accordingly, the land portion can be optimally arranged in the negative pressure generation mechanism according to the size of the sliding face.

Hereinafter, modes for carrying out a sliding member according to the present invention will be described based on embodiments.

Hereinafter, an exemplary mode for carrying out this invention will be described based on an embodiment with reference to the drawings. Note that unless otherwise clearly described, the dimensions, materials, shapes, and relative arrangement of components described in this embodiment are not intended to limit the claims of the present invention.

A sliding member according to a first embodiment will be described with reference to <FIG> and <FIG>. Note that in the first embodiment, a mechanical seal as one example of the sliding member will be described. In the first embodiment, an outer peripheral side of the sliding member forming the mechanical seal will be described as a sealed fluid side (a high-pressure fluid side), and an inner peripheral side will be described as a leakage side (a low-pressure fluid side).

<FIG> is a longitudinal sectional view showing one example of the mechanical seal <NUM>, and shows an inside mechanical seal configured to seal sealed fluid tending to leak in an inner circumferential direction from the outer periphery of a sliding face and including a rotating-side cartridge and a stationary-side cartridge. The rotating-side cartridge includes a sleeve <NUM> fitted onto a rotary shaft <NUM>, an annular rotating-side seal ring <NUM> as one sliding member, and a packing <NUM> configured to seal a portion between the sleeve <NUM> and the rotating-side seal ring <NUM>, and rotates together with the rotary shaft <NUM>.

The stationary-side cartridge includes a housing <NUM> attached to a casing <NUM>, an annular stationary-side seal ring <NUM> as another sliding member, a bellows <NUM> configured to seal the stationary-side seal ring <NUM> and the housing <NUM>, and a coiled wave spring <NUM> configured to bias the stationary-side seal ring <NUM> to a rotating-side-seal-ring-<NUM> side through the bellows <NUM>, and is fixed to the casing <NUM> in a rotation direction and an axial direction.

The mechanical seal <NUM> having the above-described configuration prevents outflow of the sealed fluid from the outer peripheral side to the inner peripheral side due to sliding of a sliding face S of the rotating-side seal ring <NUM> and a sliding face S of the stationary-side seal ring <NUM> on each other. Note that <FIG> shows a case where the width of the sliding face S of the rotating-side seal ring <NUM> is wider than the width of the sliding face S of the stationary-side seal ring <NUM>, but the present invention is not limited to such a case. Needless to say, the present invention is also applicable to an opposite case.

The materials of the rotating-side seal ring <NUM> and the stationary-side seal ring <NUM> are selected from, e.g., silicon carbide (SiC) with excellent abrasion resistance and carbon with excellent self-lubricating properties. For example, both of these rings may be made of SiC, or a combination of the SiC rotating-side seal ring <NUM> and the carbon stationary-side seal ring <NUM> may be employed.

As shown in <FIG>, the sliding face S of the stationary-side seal ring <NUM> includes a negative pressure generation mechanism <NUM>. The negative pressure generation mechanism <NUM> is separated from the leakage side by a leakage-side land portion R2. The negative pressure generation mechanism <NUM> includes a fluid introduction groove <NUM> communicated with the sealed fluid side and an annular groove portion <NUM> having an opening <NUM> communicated with the fluid introduction groove <NUM> on a downstream side and a dead end portion <NUM> surrounded by a radial land portion R3 arranged between a sealed-fluid-side land portion R1 and the leakage-side land portion R2. With this configuration, the negative pressure generation mechanism <NUM> is separated from the sealed fluid side and the leakage side by the radial land portion R3 at which the upstream-side dead end portion <NUM> is arranged between the sealed-fluid-side land portion R1 and the leakage-side land portion R2, and the downstream-side opening <NUM> is communicated with the sealed fluid side. The depth of the groove portion <NUM> is <NUM> to <NUM>, the fluid introduction groove <NUM> is <NUM> to <NUM>, and the fluid introduction groove <NUM> is formed deeper than the groove portion <NUM>.

The negative pressure generation mechanism <NUM> is arranged on both sides of the average diameter Rm of the sliding face S of the stationary-side seal ring <NUM> across the average diameter Rm. In this case, the average diameter Rm is (Ro + Ri)/<NUM> where Ro is the outer diameter of the sliding face S and Ri is the inner diameter of the sliding face S.

As shown in <FIG>, a predetermined number (six in the embodiment of <FIG>) of land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM>. The land portions <NUM> are surrounded by the groove portion <NUM>, and are formed in an island shape. The land portion <NUM> has wall portions 26a, 26b, 26c surrounding an internal space 26e and an opening 26d opening toward an upstream side, and the internal space 26e is communicated with the groove portion <NUM> through the opening 26d. A face at which the wall portions 26a, 26b, 26c of the land portions <NUM> slide on a partner-side sliding face S (the sliding face S of the rotating-side seal ring <NUM>) is smoothly finished with the substantially-same height as those of the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3 of the negative pressure generation mechanism <NUM>. Note that the outer shape of the land portion <NUM> is formed as a rectangular shape, but may be formed as a triangular shape or a polygonal shape of a pentagonal shape or more.

The negative pressure generation mechanism <NUM> includes a portion remaining after the island-shaped land portions <NUM>, the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3 have been removed from the sliding face S of the stationary-side seal ring <NUM>.

When a partner sliding member (the rotating-side seal ring <NUM>) rotates in a predetermined direction (a counterclockwise direction in <FIG>), fluid in the groove portion <NUM> of the negative pressure generation mechanism <NUM> moves, due to viscosity thereof, to the downstream side to follow a movement direction of the rotating-side seal ring <NUM>, and is discharged to the sealed fluid side through the downstream-side fluid introduction groove <NUM>. Thus, in the negative pressure generation mechanism <NUM>, fluid discharged from the groove portion <NUM> is greater than fluid supplied into the groove portion <NUM>, and for this reason, the inside of the negative pressure generation mechanism <NUM> is brought into a negative pressure and cavitation occurs. A cavitation region has a gas phase caused as a result of rupture of a liquid film due to an insufficient liquid flow rate. In the cavitation region, friction using gas with a small viscosity is dominant, and sliding torque can be reduced as compared to typical fluid lubrication with liquid. The negative pressure generation mechanism <NUM> described herein is arranged with a substantially-equal width on both sides of the average diameter Rm of the sliding face S of the stationary-side seal ring <NUM> across the average diameter Rm, and therefore, the cavitation region can be formed across a wide area from the leakage side to the sealed fluid side of the sliding face S. With this configuration, the sliding face S slides with the gas with the small viscosity across the wide area, and therefore, the sliding torque can be reduced.

However, when the cavitation region is formed across the wide area of the sliding face S, the sliding face S is entirely under the negative pressure, and the stationary-side seal ring <NUM> and the rotating-side seal ring <NUM> stick and contact each other. For this reason, a fluid lubrication state cannot be maintained. For this reason, the land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM> so that a positive pressure can be generated by a wedge effect generated by the land portions <NUM> to push out the sliding faces S and bring the sliding faces S into the fluid lubrication state. Note that the number of land portions <NUM> is not limited to that in the present embodiment as long as the sliding faces S can be pushed out and brought into the fluid lubrication state, and may be more or less than six.

As described above, the sliding member of the present embodiment provides the following advantageous effects.

A sliding member according to a second embodiment of the present invention will be described. <FIG> shows a sliding face S of the sliding member according to the second embodiment. <FIG> is different from the first embodiment in that a guide groove <NUM> is provided, but is the same as the first embodiment in other configurations. Hereinafter, the same reference numerals are used to represent the same members as those of the first embodiment, and overlapping description will be omitted.

As shown in <FIG>, a sliding face S of a stationary-side seal ring <NUM> includes a negative pressure generation mechanism <NUM>. The negative pressure generation mechanism <NUM> includes a fluid introduction groove <NUM> communicated with a sealed fluid side and an annular groove portion <NUM> having an opening <NUM> communicated with the fluid introduction groove <NUM> on a downstream side and a dead end portion <NUM> surrounded by a sealed-fluid-side land portion R1, a leakage-side land portion R2, and a radial land portion R3. With this configuration, in the negative pressure generation mechanism <NUM>, the upstream-side dead end portion <NUM> is separated from the sealed fluid side and a leakage side by the radial land portion R3 arranged between the sealed-fluid-side land portion R1 and the leakage-side land portion R2, and the downstream-side opening <NUM> is communicated with the sealed fluid side. The depth of the groove portion <NUM> is <NUM> to <NUM>, the fluid introduction groove <NUM> is <NUM> to <NUM>, and the fluid introduction groove <NUM> is formed deeper than the groove portion <NUM>.

As shown in <FIG> and <FIG>, a predetermined number (six in the embodiment of <FIG>) of island-shaped land portions <NUM> surrounded by the negative pressure generation mechanism <NUM> are arranged. The land portion <NUM> has wall portions 26a, 26b, 26c surrounding an internal space 26e and an opening 26d opening toward an upstream side, and the internal space 26e is communicated with the groove portion <NUM> through the opening 26d. A face at which the wall portions 26a, 26b, 26c of the land portions <NUM> slide on a partner-side sliding face S (a sliding face S of a rotating-side seal ring <NUM>) is smoothly finished with the substantially-same height as those of the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3. Note that the outer shape of the land portion <NUM> is formed as a rectangular shape, but may be formed as a triangular shape, a polygonal shape of a pentagonal shape or more, a semicircular shape, a semi-elliptical shape, etc..

The guide groove <NUM> is provided at a bottom portion of the negative pressure generation mechanism <NUM>. Multiple extremely-thin grooves shallower than the groove portion <NUM> of the negative pressure generation mechanism <NUM> are arranged to form the guide groove <NUM>. The guide groove <NUM> includes sealed-fluid-side guide grooves 29a arranged at substantially-equal intervals in a circumferential direction from the sealed-fluid-side land portion R1 toward a center portion (an average diameter Rm) of the sliding face S and leakage-side guide grooves 29b arranged at substantially-equal intervals in the circumferential direction from the leakage-side land portion R2 toward the center portion (the average diameter Rm) of the sliding face S. The sealed-fluid-side guide groove 29a and the leakage-side guide groove 29b are, as a whole, arranged to extend toward the opening 26d of the land portion <NUM>.

The negative pressure generation mechanism <NUM> includes a portion remaining after the land portions <NUM>, the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3 have been removed from the sliding face S of the stationary-side seal ring <NUM>.

As shown in <FIG> and <FIG>, when a partner sliding member (the rotating-side seal ring <NUM>) rotates in a predetermined direction (a counterclockwise direction in <FIG> and <FIG>), fluid in the groove portion <NUM> of the negative pressure generation mechanism <NUM> moves, due to viscosity thereof, to the downstream side to follow a movement direction of the rotating-side seal ring <NUM>, and is discharged to the sealed fluid side through the downstreammost-side fluid introduction groove <NUM>. Thus, in the negative pressure generation mechanism <NUM>, fluid discharged from the groove portion <NUM> is greater than fluid supplied into the groove portion <NUM>, and for this reason, the inside of the negative pressure generation mechanism <NUM> is brought into a negative pressure and cavitation occurs. A cavitation region is a gas phase region caused as a result of rupture of a liquid film due to an insufficient liquid flow rate. In the cavitation region, friction using gas with a small viscosity is dominant, and sliding torque can be reduced as compared to typical fluid lubrication with liquid. The negative pressure generation mechanism <NUM> described herein is arranged with a substantially-equal width on both sides of the average diameter Rm of the sliding face S of the stationary-side seal ring <NUM> across the average diameter Rm, and therefore, the cavitation region can be formed across a wide area from the leakage side to the sealed fluid side of the sliding face S. With this configuration, the sliding face slides with the gas with the small viscosity across the wide area, and therefore, the sliding torque can be reduced.

However, when the cavitation region is formed across the wide area of the sliding face S, the sliding face S is entirely under the negative pressure, and the stationary-side seal ring <NUM> and the rotating-side seal ring <NUM> stick and contact each other. For this reason, a fluid lubrication state cannot be maintained. For this reason, the land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM> so that a positive pressure can be generated by a wedge effect of the land portions <NUM> to push out a portion between the sliding faces S and bring the portion between sliding faces S into the fluid lubrication state. Note that the number of land portions <NUM> is not limited to that in the present embodiment as long as the portion between the sliding faces S can be pushed out and brought into the fluid lubrication state, and may be more or less than six.

The cavitation region is mainly the gas phase region, but a liquid flow is normally present inside the cavitation region. Such liquid is heavier than gas, and is gathered to the bottom portion of the negative pressure generation mechanism <NUM>. For this reason, the guide groove <NUM> is provided at the bottom portion of the negative pressure generation mechanism <NUM> so that the liquid in the cavitation region can be efficiently gathered to the land portions <NUM> arranged inside the negative pressure generation mechanism <NUM>. The liquid gathered to the openings 26d of the land portions <NUM> generate a high positive pressure by the wedge effect by the land portions <NUM>, and can push out the portion between the sliding faces S to maintain the fluid lubrication state.

As shown in <FIG>, the liquid in the cavitation region is guided by the sealed-fluid-side guide grooves 29a and the leakage-side guide grooves 29b, and a band-shaped liquid phase region is formed at the center portion of the sliding face S. Further, the liquid phase region is guided to the openings 26d of the land portions <NUM> by rotation of the rotating-side seal ring <NUM>, and a high positive pressure is generated by the wedge effect by the land portions <NUM> so that the portion between the sliding faces S can be pushed out and the sliding faces S can be maintained in the fluid lubrication state.

Moreover, the cavitation region is formed on both sides of the liquid phase region, and friction using gas with a small viscosity is dominant. Thus, the sliding torque can be reduced as compared to typical fluid lubrication with liquid. Further, the cavitation region is a negative pressure region, and therefore, the negative pressure generation mechanism <NUM> can exert pumping action for sucking fluid into the portion between the sliding faces S from the leakage side by means of the negative pressure, thereby reducing leakage.

Note that in the present embodiment, the guide groove <NUM> includes the sealed-fluid-side guide grooves 29a and the leakage-side guide grooves 29b, but may include the sealed-fluid-side guide grooves 29a or the leakage-side guide grooves 29b.

As described above, the sliding member of the present invention provides the following advantageous effects.

A sliding member according to a third embodiment will be described. <FIG> shows a sliding face S of the sliding member according to the third embodiment. <FIG> is only different from the second embodiment in the shape of a land portion <NUM> and the configuration of a guide groove <NUM>, and is the same as the second embodiment in other configurations. Hereinafter, the same reference numerals are used to represent the same members as those of the second embodiment, and overlapping description will be omitted.

A predetermined number (six in the embodiment of <FIG>) of land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM>. The land portion <NUM> is formed in a substantially-L shape including an island-shaped land portion 36a and a bridge portion 36b connecting the island-shaped land portion 36a and the sealed-fluid-side land portion R1. An internal space 36e surrounded by the L-shaped land portion <NUM> and the sealed-fluid-side land portion R1 is communicated with the groove portion <NUM> of the negative pressure generation mechanism <NUM> through an opening 36d opening toward an upstream side of the negative pressure generation mechanism <NUM>. A face at which the island-shaped land portions 36a and the bridge portions 36b of the land portions <NUM> slide on a partner-side sliding face S (a sliding face S of a rotating-side seal ring <NUM>) is smoothly finished with the same height as those of the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3.

The guide grooves <NUM> are provided at a bottom portion of the negative pressure generation mechanism <NUM>. A predetermined number of guide grooves <NUM> include extremely-thin bar-shaped grooves shallower than the groove portion <NUM> of the negative pressure generation mechanism <NUM>, and are arranged at substantially-equal intervals in a circumferential direction from the leakage-side land portion R2 toward the sealed fluid side. The guide groove <NUM> is, as a whole, arranged to extend toward the opening 36d of the land portion <NUM>.

When a partner sliding member (the rotating-side seal ring <NUM>) rotates in a predetermined direction (a counterclockwise direction in <FIG>), fluid in the groove portion <NUM> of the negative pressure generation mechanism <NUM> moves, due to viscosity thereof, to the downstream side to follow a movement direction of the rotating-side seal ring <NUM>, and is discharged to the sealed fluid side through the downstream-side fluid introduction groove <NUM>. Thus, in the negative pressure generation mechanism <NUM>, fluid discharged from the groove portion <NUM> is greater than fluid supplied into the groove portion <NUM>, and for this reason, the inside of the negative pressure generation mechanism <NUM> is brought into a negative pressure and cavitation occurs. A cavitation region is a gas phase region, and therefore, friction using gas with a small viscosity is dominant. Thus, sliding torque can be reduced as compared to typical fluid lubrication with liquid.

However, when the cavitation region is formed across a wide area of the sliding face S, the sliding face S is entirely under the negative pressure, and the stationary-side seal ring <NUM> and the rotating-side seal ring <NUM> stick and contact each other. For this reason, a fluid lubrication state cannot be maintained. For this reason, the land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM> so that a positive pressure can be generated by a wedge effect caused by the land portions <NUM> to push out a portion between the sliding faces S and bring the portion between sliding faces S into the fluid lubrication state. Note that the number of land portions <NUM> is not limited to that in the present embodiment as long as the sliding faces S can be pushed out and brought into the fluid lubrication state, and may be more or less than six.

A liquid flow is also normally present inside the cavitation region. Such liquid is heavier than gas, and is gathered to the bottom portion of the negative pressure generation mechanism <NUM>. Thus, the guide grooves <NUM> are provided at a bottom portion of the groove portion <NUM> of the negative pressure generation mechanism <NUM> so that the liquid in the cavitation region can be efficiently gathered to the openings 36d of the land portions <NUM> arranged inside the negative pressure generation mechanism <NUM>. The liquid gathered to the openings 36d of the land portions <NUM> generate a high positive pressure by the wedge effect by the land portions <NUM>, and can maintain the fluid lubrication state.

Specifically, in a case where the rotary shaft <NUM> rotates at high speed, the liquid inside the cavitation region is susceptible to centrifugal force, and tends to be gathered to the outside in a radial direction of the sliding face S. Thus, in a case where the rotating-side seal ring <NUM> rotates at high speed, the land portion <NUM> is formed in the substantially-L shape extending from the sealed-fluid-side (outer-diameter-side) land portion R1 so that the liquid inside the cavitation region can be efficiently gathered to the land portions <NUM> and a high positive pressure can be generated by the wedge effect by the land portions <NUM>.

As described above, the sliding member of the third embodiment provides the following advantageous effects.

A sliding member according to a fourth embodiment will be described. <FIG> shows a sliding face S of the sliding member according to the fourth embodiment. <FIG> is only different from the third embodiment in the shape of a land portion <NUM>, and is the same as the third embodiment in other configurations. Hereinafter, the same reference numerals are used to represent the same members as those of the third embodiment, and overlapping description will be omitted.

A predetermined number (six in the embodiment of <FIG>) of land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM>. The land portion <NUM> is formed in an arc shape including a pointed island-shaped land portion 46a and a bridge portion 46b connecting the land portion 46a and the sealed-fluid-side land portion R1. The land portion <NUM> has an internal space 46e surrounded by the sealed-fluid-side land portion R1 and an opening 46d opening toward an upstream side of the negative pressure generation mechanism <NUM>, and is communicated with the groove portion <NUM> of the negative pressure generation mechanism <NUM> through the opening 46d. A face at which the pointed island-shaped land portions 46a and the bridge portions 46b of the land portions <NUM> slide on a partner-side sliding face S (a sliding face S of a rotating-side seal ring <NUM>) is smoothly finished with the same height as those of the sealed-fluid-side land portion R1, the leakage-side land portion R2, and the radial land portion R3 of the negative pressure generation mechanism <NUM>.

Guide grooves <NUM> are provided at a bottom portion of the negative pressure generation mechanism <NUM>. A predetermined number of guide grooves <NUM> include extremely-thin bar-shaped grooves shallower than the groove portion <NUM>, and are arranged at substantially-equal intervals in a circumferential direction from the leakage-side land portion R2 toward the sealed fluid side. The guide groove <NUM> is, as a whole, arranged to extend toward the opening 46d of the land portion <NUM>.

When a partner sliding member (the rotating-side seal ring <NUM>) rotates in a predetermined direction (a counterclockwise direction in <FIG>), fluid in the groove portion <NUM> of the negative pressure generation mechanism <NUM> moves, due to viscosity thereof, to follow a movement direction of the rotating-side seal ring <NUM>, and is discharged to the sealed fluid side through the downstream-side fluid introduction groove <NUM>. Thus, in the negative pressure generation mechanism <NUM>, fluid discharged from the groove portion <NUM> is greater than fluid supplied into the groove portion <NUM>, and for this reason, the inside of the negative pressure generation mechanism <NUM> is brought into a negative pressure and cavitation occurs. A cavitation region is a gas phase region, and therefore, friction using gas with a small viscosity is dominant. Thus, sliding torque can be reduced as compared to typical fluid lubrication with liquid.

However, when the cavitation region is formed across a wide area of the sliding face S, the sliding face S is entirely under the negative pressure, and the stationary-side seal ring <NUM> and the rotating-side seal ring <NUM> stick and contact each other. For this reason, a fluid lubrication state cannot be maintained. For this reason, the land portions <NUM> are arranged inside the negative pressure generation mechanism <NUM> such that a positive pressure is generated at the periphery of the land portions <NUM> by a wedge effect to push out a portion between the sliding faces S and bring the portion between sliding faces S into the fluid lubrication state. Note that the number of land portions <NUM> is not limited to that in the present embodiment as long as the portion between the sliding faces S can be pushed out and brought into the fluid lubrication state, and may be more or less than six.

The cavitation region is the gas phase region, but a liquid flow is also normally present inside the cavitation region. Such liquid is heavier than gas, and is gathered to the bottom portion of the negative pressure generation mechanism <NUM>. Thus, the guide grooves <NUM> are provided at the bottom portion of the negative pressure generation mechanism <NUM> so that the liquid in the cavitation region can be efficiently gathered to the openings 46d of the land portions <NUM> arranged inside the negative pressure generation mechanism <NUM>. The liquid gathered to the openings 46d of the land portions <NUM> generate a high positive pressure by the wedge effect by the land portions <NUM>, and can maintain the fluid lubrication state.

The internal space 46e of the land portion <NUM> is a flow path narrowed toward the downstream side from the upstream-side opening 46d, and therefore, the liquid, which has been guided to the land portion <NUM>, in the cavitation region can generate a higher positive pressure by a throttle effect by the narrowed flow path and the wedge effect by the land portion <NUM>.

As described above, the sliding member according to the fourth embodiment provides the following advantageous effect in addition to the advantageous effects of the third embodiment:
the land portion <NUM> is formed as the flow path narrowed toward the downstream side from the upstream-side opening 46d, and therefore, the liquid, which has been guided to the land portion <NUM>, in the cavitation region can generate a much higher positive pressure than those of the second and third embodiments by a pressure increase effect by the throttle effect by the narrowed flow path and the wedge effect by the land portion <NUM>.

A sliding member according to a fifth embodiment will be described. <FIG> shows a sliding face S of the sliding member according to the fifth embodiment. <FIG> is different from the fourth embodiment in that multiple negative pressure generation mechanisms <NUM> of the fourth embodiment are provided at the sliding face S. Other configurations are the same as those of the fourth embodiment. Hereinafter, the same reference numerals are used to represent the same members as those of the fourth embodiment, and overlapping description will be omitted.

As shown in <FIG>, a sliding face S of a stationary-side seal ring <NUM> is configured such that a predetermined number (three in <FIG>) of negative pressure generation mechanisms <NUM> are arranged in a circumferential direction with a radial land portion R3 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM>, the negative pressure generation mechanism <NUM> including a predetermined number (two in the embodiment of <FIG>) of land portions <NUM> and a guide groove <NUM> in a groove portion <NUM>. Note that the number of negative pressure generation mechanisms <NUM> arranged in the circumferential direction with the radial land portion R3 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM> is not limited to that in the embodiment, and may be two, four, five, or six or more.

In the fifth embodiment, three negative pressure generation mechanisms <NUM> each configured such that the multiple land portions <NUM> are arranged are provided in the circumferential direction with the radial land portion R3 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM>, and therefore, fluid is supplied to the sliding face S from multiple locations by the fluid introduction grooves <NUM>. Thus, even when a fluid lubrication state is not sufficient in a low-speed rotation state such as start-up timing, the fluid supplied from the fluid introduction grooves <NUM> can contribute to lubrication of the sliding face S.

As described above, the sliding member according to the fifth embodiment provides the following advantages effect in addition to the advantageous effects of the fourth embodiment:
the multiple fluid introduction grooves <NUM> are provided such that the fluid is supplied from the fluid introduction grooves <NUM> to the sliding face S at multiple locations in the circumferential direction, and therefore, even when the fluid lubrication state is not sufficient in the low-speed rotation state such as the start-up timing, the fluid equally supplied from the multiple fluid introduction grooves <NUM> in the circumferential direction can contribute to lubrication of the sliding face S.

A sliding member according to a sixth embodiment will be described. <FIG> shows a sliding face S of the sliding member according to the sixth embodiment. <FIG> is different from the fifth embodiment in the number of land portions <NUM>, but other configurations are the same as those of the fifth embodiment. Hereinafter, the same reference numerals are used to represent the same members as those of the fifth embodiment, and overlapping description will be omitted.

As shown in <FIG>, a sliding face S of a stationary-side seal ring <NUM> is configured such that a predetermined number (three in <FIG>) of negative pressure generation mechanisms <NUM> are arranged in a circumferential direction with a radial land portion R3 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM>, the negative pressure generation mechanism <NUM> including a single land portion <NUM> and a guide groove <NUM> in a groove portion <NUM>. Note that the number of negative pressure generation mechanisms <NUM> arranged in the circumferential direction with the radial land portion R3 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM> is not limited to that in the embodiment, and may be two, four, five, or six or more.

A flow in the negative pressure generation mechanism <NUM> can be concentrated to the single land portion <NUM> provided on a downstream side, and therefore, a higher positive pressure than that in the case of providing the multiple land portions <NUM> in the single negative pressure generation mechanism <NUM> can be generated. This is suitable for a case for generating a high pressure on the sliding face S by a small sliding member.

As described above, the sliding member according to the sixth embodiment provides the following advantages effect in addition to the advantageous effects of the fifth embodiment:
each of the multiple negative pressure generation mechanisms <NUM> is provided with the single land portion <NUM> on the downstream side so that a fluid flow in a cavitation region can be concentrated to the single land portion <NUM>, and therefore, a high positive pressure can be generated by a pressure increase effect by a narrowed flow path and a wedge effect by the land portion <NUM>.

A sliding member according to a seventh embodiment will be described. <FIG> shows a sliding face S of the sliding member according to the seventh embodiment. <FIG> is different from the sixth embodiment in that a positive pressure generation mechanism <NUM> is provided in a radial land portion R4 of a negative pressure generation mechanism <NUM>, but other configurations are the same as those of the sixth embodiment. Hereinafter, the same reference numerals are used to represent the same members as those of the sixth embodiment, and overlapping description will be omitted.

As shown in <FIG>, a sliding face S of a stationary-side seal ring <NUM> is configured such that a predetermined number (three in <FIG>) of negative pressure generation mechanisms <NUM> are arranged in a circumferential direction with the radial land portion R4 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM>, the negative pressure generation mechanism <NUM> including a predetermined number (one in an example of <FIG>) of land portions <NUM> and a guide groove <NUM> in a groove portion <NUM>. The guide grooves <NUM> covering the substantially entire area of the negative pressure generation mechanism <NUM> is arranged to extend toward the single land portion <NUM> provided on a downstreammost side. Note that the number of negative pressure generation mechanisms <NUM> arranged in the circumferential direction with the radial land portion R4 being interposed between adjacent ones of the negative pressure generation mechanisms <NUM> is not limited to that in the embodiment, and may be two, four, five, or six or more. Moreover, the number of land portions <NUM> provided at each of the negative pressure generation mechanisms <NUM> is not limited to that in the present embodiment as long as a portion between the sliding faces S can be pushed out and brought into a fluid lubrication state, and may be two or three or more.

As shown in <FIG>, the positive pressure generation mechanism <NUM> is provided in the radial land portion R4 between a sealed-fluid-side land portion R1 and a leakage-side land portion R2. The positive pressure generation mechanism <NUM> is a bottomed groove portion in a rectangular shape as viewed in an axial direction, and has an opening 47a communicated with a fluid introduction groove <NUM>. A portion other than the opening 47a is surrounded by the radial land portion R4.

When a partner sliding member (a rotating-side seal ring <NUM>) rotates in a predetermined direction (a counterclockwise direction in <FIG>), fluid flows into the positive pressure generation mechanism <NUM> from the fluid introduction groove <NUM> through the opening 47a. The fluid having flowed into the positive pressure generation mechanism <NUM> is held back in the positive pressure generation mechanism <NUM>, and a positive pressure is generated by a wedge effect. With this positive pressure, even when a fluid lubrication state is not sufficient in a low-speed rotation state such as start-up timing, liquid film formation at the start-up timing can be supported.

As described above, the sliding member according to the seventh embodiment provides the following advantageous effect in addition to the advantageous effects of the sixth embodiment:
the positive pressure generation mechanism <NUM> is provided in the radial land portion R4 of the negative pressure generation mechanism <NUM>, and therefore, even when the fluid lubrication state is not sufficient in the low-speed rotation state such as the start-up timing, liquid film formation at the start-up timing can be supported by the positive pressure generated by the positive pressure generation mechanism <NUM>.

Note that the positive pressure generation mechanism <NUM> is in the rectangular shape as viewed in the axial direction, but is not limited to such a shape. The positive pressure generation mechanism <NUM> may be a triangular shape, a polygonal shape of a pentagonal shape etc., a semicircular shape, or a semi-elliptical shape, for example.

The embodiments of the present invention have been described above with reference to the drawings, but specific configurations are not limited to these embodiments. The present invention also includes changes and additions made without departing from the scope of the invention as defined by the appended claims.

In the above-described embodiments, the outer peripheral side has been described as the sealed fluid side, and the inner peripheral side has been described as the leakage side. However, the present invention is not limited to above, and is also applicable to a case where the inner peripheral side is the sealed fluid side and the outer peripheral side is the leakage side.

Claim 1:
A pair of sliding members (<NUM>, <NUM>) which, in use, are sliding relative to each other at sliding faces (S), wherein
one of the sliding faces (S) includes a negative pressure generation mechanism (<NUM>) separated from a leakage side by a leakage-side land portion (R2), separated from a sealed-fluid-side by a sealed-fluid-side land portion (R1), the one of the sliding faces further including a land portion (<NUM>) that excludes any bridge portion extending to the leakage-side land portion and that excludes any bridge portion extending to the sealed-fluid-side land portion, the land portion (<NUM>) being arranged in the negative pressure generation mechanism (<NUM>), wherein
the land portion (<NUM>) arranged in the negative pressure generation mechanism (<NUM>) is an island-shaped land portion (<NUM>) surrounded by the negative pressure generation mechanism (<NUM>), wherein
the negative pressure generation mechanism (<NUM>) includes a guide groove (<NUM>) extending from a leakage side toward the land portion (<NUM>) arranged in the negative pressure generation mechanism (<NUM>).