Abstract
A positive pressure generating mechanism comprising a positive pressure generating groove is provided to a high-pressure side of one of two sliding surfaces that slide relative to each other in a pair of sliding components, and a negative pressure generating mechanism comprising a negative pressure generating groove is provided to a low-pressure side. The positive pressure generating groove and negative pressure generating groove are communicated with a high-pressure fluid side and separated from a low-pressure fluid side by a seal surface.
Claims
1. A sliding component comprising: a positive pressure generating mechanism including a Rayleigh step mechanism provided on a high-pressure fluid side of one of two sliding surfaces that slide relatively with each other in a pair of sliding components; a negative pressure generating mechanism including a reverse spiral groove provided on a low-pressure fluid side; and a pressure release groove provided between the Rayleigh step mechanism and the reverse spiral groove; wherein the Rayleigh step mechanism, the pressure release groove and the reverse spiral groove are communicated with the high-pressure fluid side and separated from the low-pressure fluid side by a seal surface.
2. The sliding component according to claim 1, wherein a radial-direction groove is provided to cause the Rayleigh step mechanism, the pressure release groove and the reverse spiral groove to communicate with the high-pressure fluid side.
3. The sliding component according to claim 2, wherein the radial-direction groove is provided on an upstream side of the positive pressure generating mechanism to communicate with the Rayleigh step mechanism.
4. The sliding component according to claim 1, wherein the width of an internal-peripheral-side seal surface can be varied.
5. The sliding component according to claim 1, wherein a radial-direction groove is shaped so as to be slanted from the internal peripheral side communicating with the negative pressure generating mechanism to an external peripheral side in the rotational direction of a counterpart sliding surface.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIGS. 1(a) and 1(b) illustrate a sliding surface of the sliding component according to Embodiment 1 of the present invention, wherein FIG. 1 (a) is a plan view of the sliding surface and FIG. 1 (b) is a perspective view showing an enlargement of part of the sliding surface;
(2) FIGS. 2(a) and 2(b) are a views showing a modification of FIG. 1;
(3) FIGS. 3(a)-3(f) illustrate a positive pressure generating mechanism composed of a Rayleigh step mechanism or the like and a negative pressure generating mechanism composed of a reverse Rayleigh step mechanism or the like, wherein FIG. 3 (a) shows a Rayleigh step mechanism, FIG. 3 (b) shows a reverse Rayleigh step mechanism, FIG. 3 (c) and FIG. 3(e) show modified Rayleigh step mechanisms, and FIG. 3(d) and FIG. 3(f) show modified reverse Rayleigh step mechanisms;
(4) FIGS. 4(a)-4(c) illustrate a positive pressure generating mechanism comprising a spiral groove, a positive pressure generating mechanism composed of a dimple, and a negative pressure generating mechanism composed of a reverse spiral groove, wherein FIG. 4(a) shows the case of a spiral groove, FIG. 4(b) shows the case of a dimple, and FIG. 4(c) shows the case of a reverse spiral groove;
(5) FIGS. 5(a) and 5(b) illustrate the results of a numerical analysis of pressure distribution in the sliding surface of the sliding component according to Embodiment 1 of the present invention, wherein FIG. 5(a) is a partial perspective view of the sliding surface and FIG. 5(b) is a pressure distribution drawing thereof;
(6) FIGS. 6(a) and 6(b) illustrate the sliding surface of the sliding component of the comparative example, wherein FIG. 6(a) is a plan view of the sliding surface and FIG. 6(h) is a perspective view showing an enlargement of part of the sliding surface;
(7) FIGS. 7(a) and 7(b) illustrate the results of a numerical analysis of pressure distribution in the sliding surface of the sliding component of the comparative example, wherein FIG. 7(a) is a partial perspective view of the sliding surface and FIG. 7(b) is a pressure distribution drawing thereof;
(8) FIGS. 8(a)-8(d) illustrate various examples of the numbers and combinations of Rayleigh step mechanisms as positive pressure generating mechanisms and reverse Rayleigh step mechanisms as negative pressure generating mechanisms according to Embodiment 1 of the present invention;
(9) FIGS. 9(a) and 9(b) illustrate examples of combinations of the spiral groove as a positive pressure generating mechanism and the reverse Rayleigh step mechanism as a negative pressure generating mechanism according to Embodiment 1 of the present invention;
(10) FIG. 10 illustrates an example in which a plurality of reverse Rayleigh step mechanisms are provided in the radial direction in a combination of Rayleigh step mechanisms as positive pressure generating mechanisms and reverse Rayleigh step mechanisms as negative pressure generating mechanisms according to Embodiment 1 of the present invention;
(11) FIG. 11 illustrates an example in which a positive pressure generating mechanism is provided to one sliding surface, and a negative pressure generating mechanism is provided to another sliding surface, in Embodiment 1 of the present invention;
(12) FIG. 12 is a chart showing the relationship between pressure and leakage rate in the examples (a) through (d) in Embodiment 1 of the present invention shown in FIG. 8 and in the comparative example shown in FIG. 6;
(13) FIGS. 13 (a) and 13(b) illustrate the sliding surface of the sliding component according to Embodiment 2 of the present invention, wherein FIG. 13(a) is a plan view of the sliding surface and FIG. 13(b) is a perspective view showing an enlargement of part of the sliding surface;
(14) FIGS. 14 (a) and 14(b) are drawings showing a modification of FIG. 13;
(15) FIGS. 15(a)-(f) illustrate various examples of combinations of Rayleigh step mechanisms and spiral grooves as positive pressure generating mechanisms, and reverse Rayleigh step mechanisms and reverse spiral grooves as negative pressure generating mechanisms, according to Embodiment 2 of the present invention;
(16) FIG. 16 illustrates an example in which a positive pressure generating mechanism is provided to one sliding surface and a negative pressure generating mechanism is provided to another sliding surface in Embodiment 2 of the present invention;
(17) FIG. 17 illustrates an example in Embodiment 2 of the present invention, in which a plurality of reverse Rayleigh step mechanisms as negative pressure generating mechanisms are provided in the radial direction;
(18) FIG. 18 shows a modification of FIG. 17, wherein a pressure release groove is provided between a plurality of reverse Rayleigh step mechanisms;
(19) FIG. 19 illustrates an example in Embodiment 2 of the present invention in which Rayleigh step mechanisms as positive pressure generating mechanisms and reverse Rayleigh step mechanisms as negative pressure generating mechanisms are staggered in the circumferential direction;
(20) FIG. 20 illustrates an example in FIG. 19 in which a plurality of reverse Rayleigh step mechanisms as negative pressure generating mechanisms are provided in the radial direction;
(21) FIGS. 21(a) and 21(b) are for describing the sliding surface of the sliding component according to Embodiment 3 of the present invention, wherein FIG. 21(a) is a plan view of the sliding surface and FIG. 21(b) is a perspective view showing an enlargement of part of the sliding surface;
(22) FIG. 22 is a cross-sectional view of a mechanical seal on which is mounted another sliding component paired with the sliding component, according to Embodiment 4 of the present invention; and
(23) FIG. 23 is a cross-sectional view of a thrust bearing on which is mounted another sliding component paired with the sliding component, according to Embodiment 5 of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
(24) The best mode for carrying out the sliding component according to the present invention is described in detail with reference to the drawings, but the present invention should not be interpreted as being limited to this mode; various alterations, revisions, and improvements can be made based on knowledge of those skilled in the art as long as there is no deviation from the scope of the present invention.
Embodiment 1
(25) FIG. 1 illustrates a sliding surface 2 of a sliding component 1 according to Embodiment 1 of the present invention, wherein (a) is a plan view of the sliding surface 2 and (b) is a perspective view showing an enlargement of part of the sliding surface 2.
(26) In FIG. 1, the sliding component 1 is an annular body, wherein usually a high-pressure sealed fluid is present on either the internal or external periphery of the sliding surface 2 of the sliding component 1, and the other periphery is exposed to the atmosphere.
(27) This sealed fluid can be effectively sealed using the sliding component 1. The sliding component 1 is used in both a rotation sealing ring and a fixing sealing ring constituting a pair in a mechanical sealing device, for example. The sliding surface of the rotation sealing ring and the sliding surface of the opposing fixing sealing ring are brought in close contact, and a sealed fluid present on either the internal or external periphery of the sliding surface is sealed. The sliding component can also be used for a bearing that slides against a rotating shaft while lubricating oil is sealed in one side in the axial direction of a cylindrical sliding surface.
(28) In FIG. 1, for the sake of convenience in the description, a case is described in which the high-pressure sealed fluid is present on the external periphery.
(29) In FIG. 1, a counterpart sliding component rotates in a counterclockwise direction relative to the annular body sliding component 1. This holds true even if the sliding component 1 rotates in a clockwise direction.
(30) In the sliding surface 2 of the sliding component 1, the external periphery is provided with a positive pressure generating mechanism 3 composed of a Rayleigh step mechanism, a modified Rayleigh step mechanism, a spiral groove, a dimple, or another positive pressure generating groove; and the internal periphery is provided with a negative pressure generating mechanism 4 composed of a reverse Rayleigh step mechanism, a modified reverse Rayleigh step mechanism, a reverse spiral groove, or another negative pressure generating groove.
(31) The positive pressure generating mechanism 3, which is composed of a Rayleigh step mechanism, a modified Rayleigh step mechanism, a spiral groove, a dimple, or another positive pressure generating groove; and the negative pressure generating mechanism 4, which is composed of a reverse Rayleigh step mechanism, a modified reverse Rayleigh step mechanism, a reverse spiral groove, or another negative pressure generating groove; are described hereinafter.
(32) In FIG. 1, a Rayleigh step mechanism is described as an example of the positive pressure generating mechanism 3, and a reverse Rayleigh step mechanism is described as an example of the negative pressure generating mechanism 4.
(33) A plurality of Rayleigh step mechanisms 3 and reverse Rayleigh step mechanisms 4 are provided in parallel in the circumferential direction so as to constitute pairs and are formed so that as seen from the upstream side, the upstream end of a groove part 5 of an n.sup.th Rayleigh step mechanism 3(n) and the downstream end of a groove part 6 of an n−1.sup.th reverse Rayleigh step mechanism 4(n−1) substantially coincide in a position in the circumferential direction; and these groove parts 5, 6 are communicated with the high-pressure fluid side via a shared radial-direction groove 7 communicated directly with the high-pressure fluid side. The groove part 5 of the Rayleigh step mechanism 3 and the groove part 6 of the reverse Rayleigh step mechanism 4 are isolated from the low-pressure fluid side by a seal surface 8 on the internal peripheral side. Specifically, the radial-direction groove 7 is communicated with the high-pressure fluid side but is not communicated with the low-pressure fluid side.
(34) FIG. 2 is a drawing showing a modification of FIG. 1, and in FIG. 2, the same symbols as FIG. 1 indicate the same members as FIG. 1, and detailed descriptions are omitted.
(35) In FIG. 2, the means for communicating the groove parts 5, 6 with the high-pressure fluid side is different from that of FIG. 1, and a communication means 50 is configured from a radial-direction groove 51 and a communication hole 52 not communicated with the high-pressure fluid side due to the sliding surface 2. Specifically, the radial-direction groove 51 of FIG. 2 is not directly communicated with the high-pressure fluid side as is the radial-direction groove 7 of FIG. 1, but the radial-direction groove 51 itself is formed so as to not be communicated with the high-pressure fluid side due to the sliding surface 2, and the groove parts 5, 6 are communicated with the high-pressure fluid side by the communication hole 52 joining the radial-direction groove 51 and the high-pressure fluid side. The communication hole 52, being curved at a substantially right angle from the radial-direction groove 51 as shown in FIG. 2(b), is designed so as to be communicated with the high-pressure fluid side positioned on the external peripheral side of the sliding component 1, but is not limited to such; it may be provided facing outward at a slant. In cases in which the high-pressure fluid side is positioned on the internal peripheral side of the sliding component 1, the communication hole could be formed facing inward at a slant.
(36) The “positive pressure generating mechanism” and the “negative pressure generating mechanism” in the present invention are described herein.
(37) FIG. 3 is for describing a positive pressure generating mechanism composed of a Rayleigh step mechanism or another positive pressure generating groove and a negative pressure generating mechanism composed of a reverse Rayleigh step mechanism or another negative pressure generating groove, wherein (a) shows a Rayleigh step mechanism, (b) shows a reverse Rayleigh step mechanism, (c) and (e) show modified Rayleigh step mechanisms, and (d) and (f) show modified reverse Rayleigh step mechanisms.
(38) In FIG. 3(a), as shown by the arrows, the sliding component 1 rotatably moves in a clockwise direction, and another sliding component 10 rotatably moves in a counterclockwise direction. In the sliding surface 2 of the sliding component 1, a Rayleigh step 9 is formed perpendicular to the relative movement directions and facing upstream, and a groove part 5 is formed on the upstream side of the Rayleigh step 9. The sliding surface of the other sliding component 10 is flat.
(39) When the sliding components 1 and 10 move relative to each other in the directions shown by the arrows, fluid located between the sliding surfaces of the sliding components 1 and 10 acts due to its own viscosity as though to follow in the movement direction of the sliding component 1 or 10, at which time dynamic pressure (positive pressure) such as is shown by the dotted lines is therefore generated by the presence of the Rayleigh step 9.
(40) In FIG. 3(b), as shown by the arrows, the sliding component 1 rotatably moves in a clockwise direction and another sliding component 10 rotatably moves in a counterclockwise direction, but in the sliding surface 2 of the sliding component 1, a reverse Rayleigh step 11 is formed perpendicular to the relative movement directions and facing downstream, and a groove part 6 is formed on the downstream side of the reverse Rayleigh step 11. The sliding surface of the other sliding component 10 is flat.
(41) When the sliding components 1 and 10 move relative to each other in the directions shown by the arrows, fluid located between the sliding surfaces of the sliding components 1 and 10 acts due to its own viscosity as though to follow in the movement direction of the sliding component 1 or 10, at which time dynamic pressure (negative pressure) such as is shown by the dotted lines is therefore generated by the presence of the reverse Rayleigh step 11.
(42) In FIG. 3(c), the Rayleigh step 9 of FIG. 3(a) has been altered in shape to a linear inclined surface 9-1, and in FIG. 3(e), the Rayleigh step 9 of FIG. 3(a) has been altered in shape to a curved inclined surface 9-2. With the configurations of FIGS. 3(c) and (e), substantially the same positive pressure as FIG. 3(a) is generated. In the present invention, the configurations of FIGS. 3(c) and (e) are referred to as modified Rayleigh step mechanisms.
(43) In FIG. 3(d), the reverse Rayleigh step 11 of FIG. 3(b) is altered in shape to a linear inclined surface 11-1, and in FIG. 3(f), the reverse Rayleigh step 11 of FIG. 3(b) is altered in shape to a curved inclined surface 11-2. With the configurations of FIGS. 3(d) and (f), substantially the same negative pressure as FIG. 3(b) is generated. In the present invention, the configurations of FIGS. 3(d) and (f) are referred to as reverse modified Rayleigh step mechanisms.
(44) FIG. 4 is for describing a positive pressure generating mechanism comprising a spiral groove, a positive pressure generating mechanism composed of a dimple, and a negative pressure generating mechanism composed of a reverse spiral groove, wherein (a) shows the case of a spiral groove, (b) shows the case of a dimple, and (c) shows the case of a reverse spiral groove.
(45) The positive pressure generating mechanism of FIG. 4(a), a spiral groove 12, is provided over the entire periphery of the sliding surface on the high-pressure side of the sliding component 1 so as to be directly communicated with the high-pressure fluid side. The spiral groove 12 generates positive pressure by relative rotational motion with the counterpart sliding surface.
(46) The positive pressure generating mechanism of FIG. 4(b), a dimple 13, is provided over the entire periphery of the sliding surface on the high-pressure side of the sliding component 1 without being directly communicated with the high-pressure fluid side. The dimple 13 generates positive pressure by relative rotational motion with the counterpart sliding surface.
(47) The negative pressure generating mechanism of FIG. 4(c), a reverse spiral groove 14, is provided over the entire periphery of the sliding surface of the sliding component 1 without being directly communicated with the low-pressure fluid side. The high-pressure side end of the reverse spiral groove 14 is communicated with a pressure release groove 15, and part of the pressure release groove 15 is connected to the high-pressure fluid side via the radial-direction groove 7. The reverse spiral groove 14 is not directly communicated with the low-pressure fluid side, but is isolated by a seal surface. By the relative rotational motion with the counterpart sliding surface, the reverse spiral groove 14 acts to generate negative pressure and draw in fluid leaking from the high-pressure-side fluid, and to push the fluid back to the high-pressure fluid side through the pressure release groove connected to the high-pressure fluid side.
(48) In the sliding surface 2 of the sliding component 1 shown in FIGS. 1 and 2, eight Rayleigh step mechanisms 3 and reverse Rayleigh step mechanisms 4 are provided in parallel in the circumferential direction so as to constitute pairs. There are many variations of the numbers and combinations of the Rayleigh step mechanisms 3 and the reverse Rayleigh step mechanisms 4, and preferred examples are described hereinafter.
(49) The depths and widths of the groove parts 5, 6 and the radial-direction grooves 7, 51, the diameter of the communication hole 52, and the width of an internal peripheral seal surface 8 are properties that are suitably determined according to the diameter of the sliding component 1, the sliding surface width, the relative movement rate, the conditions of sealing and lubrication, and other factors.
(50) As one example, in a case in which the diameter of the sliding component 1 is approximately 20 mm and the sliding surface width is approximately 2 mm, the widths of the groove parts 5 and 6 are 0.4 to 0.6 mm, the depths are several microns, the width of the internal peripheral seal surface 8 is 0.2 to 0.4 mm, the width of the radial-direction groove 7 (the angle in the circumferential direction) is approximately 6°, and the depth is several dozen microns.
(51) FIG. 5 shows the results of a numerical analysis of pressure distribution in the sliding surface of the sliding component according to Embodiment 1, wherein (a) is a partial perspective view of the sliding surface and (b) is a pressure distribution drawing.
(52) As shown in FIG. 5(b), positive pressure is generated in the sliding surface 2, but since the reverse Rayleigh step mechanism 4 is provided in the internal peripheral side, cavitation occurs as a result of negative pressure being generated by the reverse Rayleigh step mechanism 4. Since the cavitation internal pressure is a negative pressure lower than atmospheric pressure, the pressure gradient ∂p/∂r is negative in the low-pressure-side end, the fluid moves from the high-pressure side to the low-pressure side, and as a result, drawing in (pumping) occurs in the internal peripheral side of the sliding surface. To describe this phenomenon in further detail, in the low-pressure-side seal surface 8, the pressure in the reverse Rayleigh step mechanism 4 is lower than the low-pressure-side fluid pressure (atmospheric pressure). As a result, the fluid flows from the constant-pressure fluid side into the reverse Rayleigh step mechanism 4 via the low-pressure-side seal surface 8, and as a result of this, drawing in (pumping) occurs in the internal peripheral side of the sliding surface.
(53) To further clarify the effects caused by providing the reverse Rayleigh step mechanism 4 to the internal peripheral side of the sliding surface, an example of a sliding surface not provided with the reverse Rayleigh step mechanism 4 (a comparative example) is shown in FIG. 6.
(54) FIG. 6 is for describing the sliding surface of the comparative example, wherein (a) is a plan view of the sliding surface and (b) is a perspective view showing an enlargement of part of the sliding surface.
(55) In the comparative example, only a Rayleigh step mechanism 3 is provided to the external peripheral side of the sliding surface.
(56) Through relative movement with a counterpart sliding surface, dynamic pressure (positive pressure) is generated by the Rayleigh step mechanism 3.
(57) FIG. 7 shows the results of a numerical analysis of pressure distribution in the sliding component of the comparative example, wherein (a) is a partial perspective view of the sliding surface and (b) is a pressure distribution drawing.
(58) In the case of the comparative example as shown in FIG. 7(b), positive pressure is generated in the sliding surface by the Rayleigh step 9, and the fluid pressure in the sliding surface is higher than in the low-pressure fluid side. Specifically, in the internal peripheral end of the sliding surface, the pressure gradient ∂p/∂r is positive and the fluid moves from the high-pressure side of the sliding surface to the low-pressure side; therefore, as a result, leakage occurs from the high-pressure fluid side to the low-pressure fluid side.
(59) FIG. 8 shows various examples of the numbers and combinations of Rayleigh step mechanisms 3 as positive pressure generating mechanisms and reverse Rayleigh step mechanisms 4 as negative pressure generating mechanisms in Embodiment 1 of the present invention.
(60) In FIG. 8(a), there are eight Rayleigh step mechanisms 3 and eight reverse Rayleigh step mechanisms 4, and in FIG. 8(b), there are three Rayleigh step mechanisms 3 and three reverse Rayleigh step mechanisms 4.
(61) In FIG. 8(c) there are three Rayleigh step mechanisms 3 and three reverse Rayleigh step mechanisms 4 and the width w of the internal-peripheral-side seal surface 8 is doubled, and in FIG. 8(d), there are three Rayleigh step mechanisms 3 and one reverse Rayleigh step mechanism 4 and the width w of the internal-peripheral-side seal surface 8 is doubled.
(62) FIG. 9 shows examples of combinations of the spiral groove 12 as a positive pressure generating mechanism and a reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism according to Embodiment 1 of the present invention.
(63) In FIG. 9(a), the spiral groove 12 is provided over the entire periphery, excluding the portion of the radial-direction groove 7, of the high-pressure side of the external peripheral side and is directly communicated with the high-pressure fluid, and one reverse Rayleigh step mechanism 4 is provided to the low-pressure side of the internal peripheral side.
(64) In FIG. 9(b), the spiral groove 12 is provided over the entire periphery, excluding the portion of the radial-direction groove 7, of the high-pressure side of the external peripheral side and is directly communicated with the high-pressure fluid, and four reverse Rayleigh step mechanisms 4 are provided to the low-pressure side of the internal peripheral side.
(65) FIG. 10 shows an example in which a plurality of reverse Rayleigh step mechanisms are provided in the radial direction in a combination of Rayleigh step mechanisms as positive pressure generating mechanisms and reverse Rayleigh step mechanisms as negative pressure generating mechanisms according to Embodiment 1 of the present invention.
(66) In the sliding surface 2 of the sliding component 1, positive pressure generating mechanisms 3 composed of Rayleigh step mechanisms or other positive pressure generating grooves are provided in the external peripheral side, and negative pressure generating mechanisms 4 composed of reverse Rayleigh step mechanisms or other negative pressure generating grooves are provided in the internal peripheral side. In FIG. 10, there are eight Rayleigh step mechanisms 3 in the external peripheral side, three rows of internal peripheral reverse Rayleigh step mechanisms 4 are provided in the radial direction; there are four radially outer reverse Rayleigh step mechanisms 4-1, two radially intermediate reverse Rayleigh step mechanisms 4-2, and one radially inner reverse Rayleigh step mechanism 4-3; and eight radial-direction grooves 7 are provided at equally spaced intervals in the circumferential direction.
(67) In the case of the present example, since a plurality of reverse Rayleigh step mechanisms 4 are provided in the radial direction, the result is a structure in which negative pressure is generated incrementally and leakage can be better prevented. Consequently, this approach is applicable to high-pressure, high-speed sealing.
(68) FIG. 11 shows an example in which a positive pressure generating mechanism is provided to one sliding surface, and a negative pressure generating mechanism is provided to another sliding surface, in Embodiment 1 of the present invention.
(69) In FIG. 11, in a pair of sliding components 1-1 and 1-2, a Rayleigh step mechanism 3 as a positive pressure generating mechanism is provided to the sliding surface 2-1 of one sliding component 1-1, and a reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism is provided to the sliding surface 2-2 of another sliding component 1-2.
(70) Thus, even in cases in which the Rayleigh step mechanism 3 as a positive pressure generating mechanism and the reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism are provided to separate sliding surfaces, there is no leakage when no motion is occurring, the pressure gradient ∂p/∂r of the low-pressure-side ends of the sliding surfaces can always be made negative including at the start of relative sliding, a pumping action occurs from the low-pressure side of the sliding surface toward the high-pressure fluid side, and the effect of significantly reducing the leakage rate can be achieved, similar to cases in which the Rayleigh step mechanism 3 as a positive pressure generating mechanism and the reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism are provided to the same sliding surface. In addition, since there is more space than in cases in which the Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4 are both provided to the same sliding surface, the mechanisms are more easily disposed in the sliding surfaces, and the machining timing can be shortened.
(71) In cases in which the external peripheral sides of the pair of sliding components are the high-pressure fluid sides and the internal peripheral sides are the low-pressure fluid sides, clue to positive pressure generating mechanisms for actuating the sliding surfaces in a state of fluid lubrication being provided to the static sides in the pair of sliding components 1-1 and 1-2, the fluid used in lubrication is less susceptible to the effects of centrifugal force from rotation, an appropriate amount of fluid can be ensured between the sliding surfaces, and a better state of fluid lubrication can therefore be achieved.
(72) FIG. 12 is a chart showing the relationship between pressure and leakage rate in the examples (a) through (d) in the embodiment of the present invention shown in FIG. 8 and in the comparative example shown in FIG. 6.
(73) The leakage rate of the comparative example was by far the highest, and the leakage rates of the examples (a) through (d) in the embodiment shown in FIG. 8 was low, from which it is clear that a reverse Rayleigh step mechanism contributes to reducing the leakage rate.
(74) In the examples (a) through (d) in the embodiment shown in FIG. 8, the leakage rate was the lowest in the case of example (d), in which there were three Rayleigh step mechanisms and one reverse Rayleigh step mechanism, and the width w of the seal surface on the internal peripheral side was doubled. It is also clear that the leakage rate was low even at a high pressure in the case of example (c), in which there were three Rayleigh step mechanisms and three reverse Rayleigh step mechanisms, and the width w of the seal surface on the internal peripheral side was doubled. In the case of example (a), in which there were eight Rayleigh step mechanisms and eight reverse Rayleigh step mechanisms, the leakage rate increased rapidly when the pressure increased. From the examples described above, it is clear that the fewer the radial-direction grooves 7 (the fewer the reverse Rayleigh step mechanisms) and the greater the width w of the seal surface on the internal peripheral side, the lower the leakage rate.
Embodiment 2
(75) FIG. 13 is for describing the sliding surface 2 of the sliding component 1 according to Embodiment 2 of the present invention, wherein (a) is a plan view of the sliding surface 2 and (b) is a perspective view showing an enlargement of part of the sliding surface 2.
(76) In FIG. 13, the same symbols as those of Embodiment 1 indicate the same members as Embodiment 1, and detailed descriptions are omitted. In FIG. 13, the rotational direction of the counterpart sliding component opposing the annular sliding component 1 is a counterclockwise direction. This is the same even if the sliding component 1 rotates in a clockwise direction.
(77) The external peripheral side of the sliding surface 2 of the sliding component 1 is provided with a positive pressure generating groove 3 composed of a Rayleigh step mechanism, a modified Rayleigh step mechanism, a spiral groove, a dimple, or the like; and the internal peripheral side is provided with a negative pressure generating mechanism 4 composed of a reverse Rayleigh step mechanism, a modified reverse Rayleigh step mechanism, a reverse spiral groove, or the like.
(78) The description on FIG. 13 uses a Rayleigh step mechanism as an example of a positive pressure generating mechanism 3, and a reverse Rayleigh step mechanism as an example of a negative pressure generating mechanism 4.
(79) A pressure release groove 15 is provided between the Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4. The pressure release groove 15 is for releasing the dynamic pressure (positive pressure) generated in the high-pressure-side positive pressure generating mechanism, e.g., the Rayleigh step mechanism 3 to the pressure of the high-pressure fluid, and thereby preventing fluid from flowing into the low-pressure-side negative pressure generating mechanism, e.g., the reverse Rayleigh step mechanism 4 and weakening the negative-pressure-generating capability of the negative pressure generating mechanism. Fluid attempting to flow to the low-pressure fluid side due to the pressure generated in the high-pressure-side positive pressure generating mechanism is led to the pressure release groove 15, which fulfills the role of letting the fluid into the high-pressure fluid side.
(80) The pressure release groove 15 is formed from a circular groove, and is disposed between the Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4 and separated from the two mechanisms by predetermined sliding surface widths. The depth of the circular groove is approximately the same depth as the radial-direction groove 7 and the width is sufficient to release high pressures, for example, and part of the groove is connected to the high-pressure fluid side. In FIG. 13, the Rayleigh step mechanism 3, the reverse Rayleigh step mechanism 4, and the pressure release groove 15 are communicated with the high-pressure fluid side via the radial-direction groove 7, and are separated from the low-pressure fluid side by the seal surface 8. Specifically, the radial-direction groove 7 communicates the Rayleigh step mechanism 3, the reverse Rayleigh step mechanism 4, and the pressure release groove 15 with the high-pressure fluid side but prevents their being communicated with the low-pressure fluid side.
(81) In FIG. 13, a plurality of Rayleigh step mechanisms 3 and reverse Rayleigh step mechanisms 4 are provided on either side of the pressure release groove 15 so as to be parallel in the circumferential direction and constitute pairs. As seen from the upstream side, the upstream end of the groove part 5 of the n.sup.th Rayleigh step mechanism 3 (n) and the downstream end of the groove part 6 of the n−1.sup.th reverse Rayleigh step mechanism 4 (n−1) are formed so as to substantially coincide in a position in the circumferential direction, and the groove parts 5, 6 and the pressure release groove 15 are communicated with the high-pressure fluid side via the shared radial-direction groove 7.
(82) FIG. 14 is a drawing showing a modification of FIG. 13, symbols in FIG. 14 that are the same as FIG. 13 indicate the same symbols as FIG. 13, and detailed descriptions are omitted.
(83) In FIG. 14, the means for communicating the groove parts 5, 6 with the high-pressure fluid side is different from that of FIG. 13, and the communication means 50 is configured from the radial-direction groove 51 and the communication hole 52 not communicated with high-pressure fluid side by the sliding surface 2. Specifically, the radial-direction groove 51 of FIG. 14 is not directly communicated with the high-pressure fluid side as is the radial-direction groove 7 of FIG. 13, the radial-direction groove 51 itself is formed so as to not be communicated with high-pressure fluid side by the sliding surface 2, and the groove parts 5, 6 are communicated with high-pressure fluid side by the communication hole 52 that joins the radial-direction groove 51 and the high-pressure fluid side. The communication hole 52, being curved at a substantially right angle from the radial-direction groove 51 as shown in FIG. 14(b), is designed so as to be communicated with the high-pressure fluid side positioned on the external peripheral side of the sliding component 1, but is not limited to such and may be provided facing outward at a slant. In cases in which the high-pressure fluid side is positioned on the internal peripheral side of the sliding component 1, the communication hole could be formed facing inward at a slant.
(84) FIG. 15 shows various examples of combinations of Rayleigh step mechanisms 3 and spiral grooves 12 as positive pressure generating mechanisms, and reverse Rayleigh step mechanisms 4 and reverse spiral grooves 14 as negative pressure generating mechanisms, according to Embodiment 2 of the present invention.
(85) In FIG. 15, the rotational direction of the counterpart sliding surface is the same counterclockwise direction as FIG. 13.
(86) In FIG. 15(a), there are eight Rayleigh step mechanisms 3 disposed on the external peripheral high-pressure side of the sliding component 1 and one reverse Rayleigh step mechanism 4 disposed on the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed.
(87) In FIG. 15(b), there are eight Rayleigh step mechanisms 3 disposed on the external peripheral high-pressure side of the sliding component 1 and eight reverse Rayleigh step mechanisms 4 disposed on the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed.
(88) In FIG. 15(c), there are eight Rayleigh step mechanisms 3 disposed on the external peripheral high-pressure side of the sliding component 1 and a reverse spiral groove 14 provided around the entire periphery of the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed.
(89) In FIG. 15(d), a spiral groove 12 is provided around the entire periphery of the external peripheral high-pressure side of the sliding component 1 and one reverse Rayleigh step mechanism 4 is disposed on the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed.
(90) In FIG. 15(e), a spiral groove 12 is provided around the entire periphery of the external peripheral high-pressure side of the sliding component 1 and eight reverse Rayleigh step mechanisms 4 are disposed on the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed.
(91) In FIG. 15(f), a spiral groove 12 is provided around the entire periphery of the external peripheral high-pressure side of the sliding component 1 and a reverse spiral groove 14 is provided around the entire periphery of the internal peripheral low-pressure side, between which the pressure release groove 15 is disposed. In this case, the pressure release groove 15 fulfills the role of releasing pressure to the high-pressure fluid side of the reverse spiral groove 14.
(92) In FIGS. 15(a), (b), (d), and (e), the leakage rate is low in (a) and (d) in which the number of reverse Rayleigh step mechanisms 4 is low.
(93) FIG. 16 shows an example in Embodiment 2 of the present invention, in which a positive pressure generating mechanism is provided to one sliding surface and a negative pressure generating mechanism is provided to another sliding surface.
(94) In FIG. 16, among a pair of sliding components 1-1 and 1-2, a Rayleigh step mechanism 3 as a positive pressure generating mechanism is provided to the sliding surface 2-1 of one sliding component 1-1, and a reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism is provided to the sliding surface 2-2 of the other sliding component 1-2.
(95) Thus, even in cases in which a Rayleigh step mechanism 3 as a positive pressure generating mechanism and a reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism are provided to separate sliding surfaces, there is no leakage when no motion is occurring, the pressure gradient ∂p/∂r of the low-pressure-side ends of the sliding surfaces can always be made negative including at the start of relative sliding, a pumping action occurs from the low-pressure side of the sliding surface toward the high-pressure fluid side, and the effect of significantly reducing the leakage rate can be achieved, similar to cases in which the Rayleigh step mechanism 3 as a positive pressure generating mechanism and the reverse Rayleigh step mechanism 4 as a negative pressure generating mechanism are provided to the same sliding surface. In addition, since there is more space than in cases in which the Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4 are both provided to the same sliding surface, the mechanisms are more easily disposed in the sliding surfaces, and the machining timing can be shortened.
(96) In cases in which the external peripheral sides of the pair of sliding components are the high-pressure fluid sides and the internal peripheral sides are the low-pressure fluid sides, due to positive pressure generating mechanisms for actuating the sliding surfaces in a state of fluid lubrication being provided to the static sides in the pair of sliding components 1-1 and 1-2, the fluid used in lubrication is less susceptible to the effects of centrifugal force from rotation, an appropriate amount of fluid can be ensured between the sliding surfaces, and a better state of fluid lubrication can therefore be achieved.
(97) FIG. 17 shows an example in Embodiment 2 of the present invention, in which a plurality of reverse Rayleigh step mechanisms as a negative pressure generating mechanism are provided in the radial direction.
(98) In FIG. 17, in the sliding surface 2 of the sliding component 1, the external peripheral side is provided with positive pressure generating mechanisms 3 composed of Rayleigh step mechanisms or other positive pressure generating grooves, and the internal peripheral side is provided with negative pressure generating mechanisms 4 composed of reverse Rayleigh step mechanisms or other negative pressure generating grooves. A pressure release groove 15 is provided between the Rayleigh step mechanisms 3 and the reverse Rayleigh step mechanisms 4. The pressure release groove 15 is for releasing the dynamic pressure (positive pressure) generated in the high-pressure-side positive pressure generating mechanisms, e.g., the Rayleigh step mechanisms 3 to the pressure of the high-pressure fluid, and thereby preventing fluid from flowing into the low-pressure-side negative pressure generating mechanisms, e.g., the reverse Rayleigh step mechanisms 4 and weakening the negative-pressure-generating capability of the negative pressure generating mechanisms. Fluid attempting to flow to the low-pressure fluid side due to the pressure generated in the high-pressure-side positive pressure generating mechanisms is led to the pressure release groove 15, which fulfills the role of letting the fluid into the high-pressure fluid side. In FIG. 17, there are eight Rayleigh step mechanisms 3 in the external peripheral side, three rows of internal peripheral reverse Rayleigh step mechanisms 4 are provided in the radial direction; there are four radially outer reverse Rayleigh step mechanisms 4-1, two radially intermediate reverse Rayleigh step mechanisms 4-2, and one radially inner reverse Rayleigh step mechanism 4-3; and eight radial-direction grooves 7 are provided at equally spaced intervals in the circumferential direction.
(99) In the case of the present example, since a plurality of reverse Rayleigh step mechanisms 4 are provided in the radial direction, the result is a structure in which negative pressure is generated incrementally and leakage can be better prevented. Consequently, this approach is applicable to high-pressure, high-speed sealing.
(100) FIG. 18 shows a modification of FIG. 17, wherein a pressure release groove is provided between a plurality of reverse Rayleigh step mechanisms.
(101) In FIG. 18, in the sliding surface 2 of the sliding component 1, the external peripheral side is provided with positive pressure generating mechanisms 3 composed of Rayleigh step mechanisms or other positive pressure generating grooves, and the internal peripheral side is provided with negative pressure generating mechanisms 4 composed of reverse Rayleigh step mechanisms or other negative pressure generating grooves. In FIG. 18, there are eight Rayleigh step mechanisms 3 in the external peripheral side, and three rows of internal peripheral reverse Rayleigh step mechanisms 4 are provided in the radial direction; there are four radially outer reverse Rayleigh step mechanisms 4-1, two radially intermediate reverse Rayleigh step mechanisms 4-2, and one radially inner reverse Rayleigh step mechanism 4-3; and eight radial-direction grooves 7 are provided at equally spaced intervals in the circumferential direction.
(102) Respective pressure release grooves 15 are provided between the Rayleigh step mechanisms 3 and the radially external reverse Rayleigh step mechanisms 4-1, between the radially external reverse Rayleigh step mechanisms 4-1 and the radially intermediate reverse Rayleigh step mechanisms 4-2, and between the radially intermediate reverse Rayleigh step mechanisms 4-2 and the radially internal reverse Rayleigh step mechanisms 4-3.
(103) Thus, since a plurality of reverse Rayleigh step mechanisms 4 as negative pressure generating mechanisms are provided in the radial direction and respective pressure release grooves 15 are provided between these mechanisms in the radial direction, negative pressure is generated incrementally, and in addition to the effect of better preventing leakage, also achieved is the effect of blocking the coming and going of fluid between the reverse Rayleigh step mechanisms 4 and impeding the occurrence of leakage.
(104) FIG. 19 shows an example in Embodiment 2 of the present invention in which Rayleigh step mechanisms as positive pressure generating mechanisms and reverse Rayleigh step mechanisms as negative pressure generating mechanisms are staggered in the circumferential direction.
(105) In FIG. 19, in the sliding surface 2 of the sliding component 1, positive pressure generating mechanisms 3 composed of Rayleigh step mechanisms or the like are provided in the external peripheral side, and negative pressure generating mechanisms 4 composed of reverse Rayleigh step mechanisms or the like are provided in the internal peripheral side. FIG. 19 shows a configuration in which there are eight external peripheral Rayleigh step mechanisms 3 and four internal peripheral reverse Rayleigh step mechanisms 4, and four radial-direction grooves 53 communicated with the reverse Rayleigh step mechanisms 4 are provided in positions that are circumferentially midway between each of the eight radial-direction grooves 7 communicated with the Rayleigh step mechanisms 3; wherein the Rayleigh step mechanisms 3 as positive pressure generating mechanisms and the reverse Rayleigh step mechanisms 4 as negative pressure generating mechanisms are staggered in the circumferential direction. Pressure release grooves 15 are also provided between the Rayleigh step mechanisms 3 and the reverse Rayleigh step mechanisms 4, and the four radial-direction grooves 53 are communicated with the eight radial-direction grooves 7 via the pressure release grooves 15. The radial-direction grooves 53 are disposed in the internal peripheral side and are not communicated directly with the high-pressure fluid side, but are communicated with the high-pressure fluid side via the pressure release grooves 15 and the radial-direction grooves 7. Thus, since the radial-direction grooves 53 communicated with the reverse Rayleigh step mechanisms 4 are not communicated directly with the high-pressure fluid side but are communicated with the high-pressure fluid side via the narrow pressure release grooves 15, the pressure of the radial-direction grooves 53 decreases and leakage from the radial-direction grooves 53 to the static-pressure fluid side is reduced.
(106) FIG. 20 shows an example in FIG. 19 in which a plurality of reverse Rayleigh step mechanisms as negative pressure generating mechanisms are provided in the radial direction.
(107) In FIG. 20, in the sliding surface 2 of the sliding component 1, positive pressure generating mechanisms 3 composed of Rayleigh step mechanisms or other positive pressure generating grooves are provided in the external peripheral side, and negative pressure generating mechanisms 4 composed of reverse Rayleigh step mechanisms or other negative pressure generating grooves are provided in the internal peripheral side. In FIG. 20, there are eight external peripheral Rayleigh step mechanisms 3, three rows of internal peripheral reverse Rayleigh step mechanisms 4 are provided in the radial direction, four radially outer reverse Rayleigh step mechanisms 4-1 are provided, two radially intermediate reverse Rayleigh step mechanisms 4-2 are provided, and one radially inner reverse Rayleigh step mechanism 4-3 is provided.
(108) Respective pressure release grooves 15 are provided between the Rayleigh step mechanisms 3 and the radially outer reverse Rayleigh step mechanisms 4-1, between the radially outer reverse Rayleigh step mechanisms 4-1 and the radially intermediate reverse Rayleigh step mechanisms 4-2, and between the radially intermediate reverse Rayleigh step mechanisms 4-2 and the radially inner reverse Rayleigh step mechanism 4-3.
(109) The eight external peripheral Rayleigh step mechanisms 3 are respectively communicated with the eight radial-direction grooves 7 directly communicated with the high-pressure fluid side, the four radially outer reverse Rayleigh step mechanisms 4-1 are respectively communicated with four radial-direction grooves 54 provided in the same circumferential formation, the two radially intermediate reverse Rayleigh step mechanisms 4-2 are respectively communicated with two radial-direction grooves 55 provided in the same circumferential formation, the one radially inner reverse Rayleigh step mechanism 4-3 is communicated with one radial-direction groove 56 provided in the same circumferential formation, and the radial-direction grooves 7, 54, 55, 56 of each row are disposed so that their positions are staggered in the circumferential direction. Therefore, the four radially outer reverse Rayleigh step mechanisms 4-1 are communicated with the high-pressure fluid side via the four radial-direction grooves 54 provided in the same circumferential formation, the pressure release groove 15, and the radial-direction grooves 7; the two radially intermediate reverse Rayleigh step mechanisms 4-2 are communicated with the high-pressure fluid side via the two radial-direction grooves 55 provided in the same circumferential formation, the pressure release groove 15, the radial-direction grooves 54, and the radial-direction grooves 7; and the one radially inner reverse Rayleigh step mechanism 4-3 is communicated with the high-pressure fluid side via the one radial-direction groove 56 provided in the same circumferential formation, the pressure release groove 15, the radial-direction grooves 55, 54, and the radial-direction grooves 7.
(110) Thus, since the radial-direction grooves 7, 54, 55, 56 are provided in each row and the radial-direction grooves 7, 54, 55, 56 of each row are disposed so as to be staggered in the circumferential direction, the high-pressure fluid is not directly communicated with the internal peripheral side vicinity of the sliding surface via the radial-direction grooves, and leakage from the high-pressure fluid side to the low-pressure fluid side can therefore be better prevented.
Embodiment 3
(111) FIG. 21 is for describing the sliding surface 2 of the sliding component 1 according to Embodiment 3 of the present invention, wherein (a) is a plan view of the sliding surface 2 and (b) is a perspective view showing an enlargement of part of the sliding surface 2.
(112) In FIG. 21, the same symbols as those of Embodiments 1 and 2 indicate the same members as Embodiments 1 and 2, and detailed descriptions are omitted. In FIG. 21, the rotational direction of the counterpart sliding component opposing the annular sliding component 1 is a counterclockwise direction. This is the same even if the sliding component 1 rotates in a clockwise direction.
(113) In Embodiment 1 described above, the concept that the smaller the number of reverse Rayleigh step mechanisms 4 (the smaller the number of radial-direction grooves 7) and the greater the width w of the internal-peripheral-side seal surface 8, the lower the leakage rate, is as described in Embodiment 1 and so forth. Needless to say, however, the number of radial-direction grooves 7 cannot be zero, and there is a certain limit on the width w of the internal-peripheral-side seal surface 8.
(114) To reduce leakage from the radial-direction grooves 7 in Embodiment 3, whereas in Embodiments 1 and 2 the radial-direction grooves 7 were disposed in directions of 90° relative to the circumferential direction (the tangential direction), here the grooves are slanted in the rotational direction of the counterpart sliding surface and are disposed in a direction of expanding in a radial formation in the rotational direction of the counterpart sliding surface, as shown in FIG. 21.
(115) In FIG. 21, in the sliding surface 2 of the sliding component 1, Rayleigh step mechanisms 3 as positive pressure generating mechanisms are provided in the external peripheral side, reverse Rayleigh step mechanisms 4 as negative pressure generating mechanisms are provided in the internal peripheral side, and a pressure release groove 15 is provided between the Rayleigh step mechanisms 3 and the reverse Rayleigh step mechanisms 4.
(116) The groove parts 5 of the Rayleigh step mechanisms 3 and the groove parts 6 of the reverse Rayleigh step mechanisms 4 are communicated with the high-pressure fluid side via a shared radial-direction groove 7.
(117) The radial-direction groove 7 is shaped so as to be slanted in the rotational direction of the counterpart sliding surface from the internal peripheral side toward the external peripheral side, and when a plurality of radial-direction grooves 7 are disposed in the circumferential direction, the grooves are disposed in a direction of expanding in a radial formation in the rotational direction of the counterpart sliding surface.
(118) In the example of the radial-direction groove 7 shown in FIG. 21, the groove is shaped so as to be slanted in the rotational direction of the counterpart sliding surface from the internal peripheral side communicated with the groove parts 6 of the reverse Rayleigh step mechanisms 4 toward the pressure release groove 15 positioned in the external peripheral side, and in the portions of the Rayleigh step mechanisms 3 positioned in the outermost peripheral side of the radial direction, the groove is shaped facing in a direction 90° relative to the circumferential direction (the tangential direction). Therefore, fluid that flows from the groove parts 6 of the reverse Rayleigh step mechanisms 4 into the radial-direction groove 7 is expelled in the direction shown by the arrow 16.
(119) As shall be apparent, the radial-direction groove 7 may be shaped so as to be uniformly slanted in the rotational direction of the counterpart sliding surface from the internal peripheral side communicated with the groove parts 6 of the reverse Rayleigh step mechanisms 4 up to the external-peripheral-side ends, but essentially the groove is preferably shaped so as to be slanted in the rotational direction of the counterpart sliding surface from the internal peripheral side toward the external peripheral side.
(120) The greater the slanting angle of the radial-direction groove 7, the lesser the positive pressure gradient in the radial direction in the radial-direction groove 7 (a pressure gradient such that the pressure increases from the internal peripheral side toward the external peripheral side), and as a result, the lower the leakage rate from the radial-direction groove 7.
(121) Furthermore, the width of the radial-direction groove 7 may be shaped so as to gradually expand from the internal peripheral side toward the external peripheral side.
(122) Thus, due to the radial-direction groove 7 being disposed so as to be slanted in a direction of expanding in a radial formation in the rotational direction of the counterpart sliding surface, the internal peripheral side of the radial-direction groove 7 is closed off by the seal surface 8; therefore, the same negative pressure effect as with a reverse spiral groove occurs in the radial-direction groove 7, fluid leaking from the high-pressure side is drawn in, creating an action of pushing back to the high-pressure fluid side in a state of a lessened positive pressure gradient in the radial direction, and leakage from the radial-direction groove 7 is therefore reduced.
Embodiment 4
(123) FIG. 22 is a cross-sectional view of a mechanical seal on which is mounted another sliding component paired with the sliding component of the present invention.
(124) In a mechanical seal 20, the sliding component 1 of the present invention is mounted as a fixing sealing ring 21. The fixing sealing ring 21 is movably mounted via an O ring 24 in a holding ring 23 secured to a housing 30. A rotational sealing ring 26, whose sliding surface 29 is ground down to a flat surface, is made to face the fixing sealing ring 21. The fixing sealing ring 21 creates a seal between an internal side P2 and an atmosphere side P1 while a sliding surface 22 is pressed and held firmly against the opposing sliding surface 29 by a spring 25. In the sliding surface 22 of the fixing sealing ring 21, the external peripheral side is provided with a positive pressure generating mechanism 27 composed of a Rayleigh step mechanism, a modified Rayleigh step mechanism, a spiral groove, a dimple, or the like; and the internal peripheral side of the sliding surface 22 is provided with a negative pressure generating mechanism 28 composed of a reverse Rayleigh step mechanism, a modified reverse Rayleigh step mechanism, a reverse spiral groove, or the like. The effects achieved by this configuration are that there is no leakage when no motion is occurring, the frictional coefficient is low because the action of the external peripheral positive pressure generating mechanism 27 always takes place in a state of fluid lubrication including the beginning of rotation, and leakage can be reduced because the internal peripheral negative pressure generating mechanism 28 makes pumping possible from the low-pressure side to the high-pressure side. In cases in which the pressure release groove (not shown) of Embodiment 2 above is provided between the positive pressure generating mechanism 27 and the negative pressure generating mechanism 28, the dynamic pressure generated by the positive pressure generating mechanism 27 is released to the pressure of the high-pressure fluid, whereby the fluid does not flow into the low-pressure-side negative pressure generating mechanism 28, and loss of the negative pressure generating capability of the negative pressure generating mechanism can be prevented.
Embodiment 5
(125) FIG. 23 is a cross-sectional view of a thrust bearing on which is mounted another sliding component paired with the sliding component of the present invention.
(126) The number 40 indicates an entire thrust hearing, which is basically configured from a cylindrical housing 44 which is disposed so as to enclose the external peripheral surface of an annular ridged protrusion 42 provided to a rotating shaft 41, and which has an internal peripheral surface that faces the external periphery of the ridged protrusion 42 via a minuscule radial-direction gap 43; and thrust receivers 46, 47 which extend inward in the radial direction from both ends of the housing 44 and which face the end surfaces of the ridged protrusion 42 via tiny gaps 45 in the thrust direction; the bearing body being configured by the housing 44 and the thrust receivers 46, 47.
(127) The thrust receivers 46, 47 of the bearing body and the end surfaces of the ridged protrusion 42 are in rotatable slidable contact with each other in the axial direction. A lubricant is held by its own surface tension in the minuscule radial-direction gap 43 and the minuscule thrust-direction gaps 45.
(128) Furthermore, the external peripheral sides of the sliding surfaces of the thrust receivers 46, 47 are provided with positive pressure generating mechanisms 48 composed of Rayleigh step mechanisms, modified Rayleigh step mechanisms, spiral grooves, dimples, or the like, and the internal peripheral sides of the sliding surfaces are provided with negative pressure generating mechanisms 49 composed of reverse Rayleigh step mechanisms, modified reverse Rayleigh step mechanisms, reverse spiral grooves, or the like.
(129) The effects achieved by this configuration are that there is no leakage when no motion is occurring, the frictional coefficient is low because the action of the external peripheral positive pressure generating mechanisms 48 consistently takes place in a state of fluid lubrication including the beginning of rotation, and leakage can be reduced because the internal peripheral negative pressure generating mechanisms 49 make pumping possible from the low-pressure side to the high-pressure side.
(130) In cases in which the pressure release grooves (not shown) of Embodiment 2 above are provided between the positive pressure generating mechanisms 48 and the negative pressure generating mechanisms 49, the dynamic pressure generated by the positive pressure generating mechanisms 48 is released to the pressure of the high-pressure fluid, whereby the fluid does not flow into the low-pressure-side negative pressure generating mechanisms 49, and loss of the negative pressure generating capability of the negative pressure generating mechanisms can be prevented.
KEY
(131) 1 Sliding component 2 Sliding surface 3 Positive pressure generating mechanism (Rayleigh step mechanism) 4 Negative pressure generating mechanism (reverse Rayleigh step mechanism) 5 Groove part of Rayleigh step mechanism 6 Groove part of reverse Rayleigh step mechanism 7 Shared radial-direction groove 8 Internal-peripheral-side seal surface 9 Rayleigh step 10 Opposing sliding component 11 Reverse Rayleigh step 12 Spiral groove 13 Dimple 14 Reverse spiral groove 15 Pressure release groove 16 Arrow indicating fluid-expelling direction 20 Mechanical seal 21 Fixing sealing ring 22 Sliding surface 23 Holding ring 24 O ring 25 Spring 26 Rotational sealing ring 27 Positive pressure generating mechanism 28 Negative pressure generating mechanism 29 Sliding surface 30 Housing 40 Thrust bearing 41 Rotating shaft 42 Ridged protrusion 43 Radial-direction gap 44 Housing 45 Tiny gap 46 Thrust receiver 47 Thrust receiver 48 Positive pressure generating mechanism 49 Negative pressure generating mechanism 50 Communication means 51 Radial-direction groove 52 Communication hole 53-56 Radial-direction grooves
