Rotary seal mechanism of fluid feeding mechanism and rotary joint

Abstract

To provide a rotary seal mechanism of a fluid feeding mechanism which can be decompressed after a stop of the supply of a surface pressure adjustment fluid and a rotary joint.SOLUTION: A rotary joint 2 is used for a fluid feeding mechanism which feeds a plurality of kinds of fluids which are supplied from a fluid supply source to a rotation part 2a which rotates around an axial core via a fixed part 2b. In a second shaft seal part 22, an O-ring 22a is attached into an attachment groove of the O-ring 22a in a free state, arranged so as to be contactable over an entire periphery of a slide face between a side face of the attachment groove at a low-pressure side and a fixed shaft part, pressed to the side face of the attachment groove at the low-pressure side by a pressing force which is equal to or higher than 5 N, and a pressing force per one crest which is equal to or lower than 25 N by a pressing spring 26 being a resin-made or an elastomer-made wave washer arranged in the attachment groove, and decompressed by making a force in a direction opposite to the pressing force by the pressing spring 26 act thereon by remaining pressure at a stop of the supply of surface pressure adjustment air supplied from a pressurization open hole 20.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a rotary seal mechanism in a fluid supply mechanism for supplying a fluid to a rotating part, and a rotary joint used in the rotary seal mechanism. [Background technology]

[0002] In a fluid delivery mechanism that delivers a fluid such as a coolant for cooling to a rotating part that rotates during operation, such as the spindle of a machine tool, a rotary joint is used as a fluid coupling that connects a fixed fluid delivery pipe to a flow path in the rotating part. The rotary joint has a structure in which a rotating shaft that is coupled to the rotating part and rotates and a fixed shaft that is connected to the fluid delivery mechanism are coaxially arranged and opposed in the axial direction, and the sealing surfaces of rotary seals attached to the opposing end faces of each are brought into close contact with each other to prevent leakage of the fluid.

[0003] In recent years, air has been used as a cooling medium in addition to the water-based liquid coolant that has been commonly used in the past. The use of air has the advantage that appropriate cooling characteristics can be obtained according to the object to be cooled, and that environmental measures such as wastewater treatment after use are not required, thereby reducing the environmental impact. When it is necessary to use both liquid coolant and air in the same device, the rotary joint used as a fluid coupling needs to be designed so that it can be used with both liquid and gas, which have different fluid properties, and a rotary joint of a type designed for such use has been proposed (see, for example, Patent Document 1).

[0004] The example shown in Patent Document 1 is a rotary joint used in a fluid delivery mechanism that delivers multiple types of fluids supplied from a fluid supply source via a fixed part to a rotating part that rotates around an axis. A step is provided on the outer peripheral surface of the fixed shaft part that fits into a fitting hole in a housing member and moves in the axial direction, and when a type of fluid that requires a low seal surface pressure is supplied, a surface pressure adjusting fluid introduced via a pressurized opening is allowed to act on the step part, causing a force on the fixed seal part in the direction opposite to the pressing force due to the fluid pressure to be applied, thereby reducing the seal surface pressure of the face seal part.

[0005] In the rotary joint shown in Patent Document 1, the first and second shaft seal portions are generally sealed by squeezing them in the axial and radial directions with an O-ring or the like. When air is supplied as the surface pressure adjusting fluid, the surface pressure adjusting air is supplied between the first and second shaft seal portions to control the surface pressure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2008-64274 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the supply of the surface pressure adjusting air is stopped, the sealing performance of the first shaft seal and the second shaft seal is maintained, so that internal pressure remains in the space between the first shaft seal and the second shaft seal, and this internal pressure causes the first shaft seal and the second shaft seal to tighten the fixed shaft, restricting the fixed shaft and possibly causing the face seal to malfunction.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a rotary seal mechanism in a fluid feed mechanism that is capable of depressurizing after the supply of surface pressure adjusting fluid is stopped, and a rotary joint used in this rotary seal mechanism. [Means for solving the problem]

[0009] The rotary seal mechanism of the present invention is a rotary seal mechanism in a fluid supply mechanism that comprises a rotary part provided with an axial rotary flow passage and a fixed part provided with an axial fixed flow passage, and selectively supplies two types of fluids, which are supplied from two fluid supply sources and have different ratios between the supply pressure and the appropriate seal surface pressure value, to the rotary flow passage of the rotary part that rotates around the axis via the fixed flow passage. The rotary seal mechanism comprises a rotary seal part provided in the rotary part and having a first seal surface with a rotary flow passage opening on a side end face, and a fixed shaft part formed with a fixed flow passage penetrating in the axial direction, and a second seal part with a fixed flow passage opening on one side end face. the fixed shaft portion is provided with a hole on a housing member constituting a main body of the fixed portion and into which the fixed shaft portion is fitted while allowing axial movement; a step portion dividing the fixed shaft portion into a large diameter portion having a shaft diameter that fits into the fitting hole and a small diameter portion having a shaft diameter smaller than the large diameter portion and provided close to the second seal surface side; a first shaft seal portion and a second shaft seal portion that seal gaps between the inner peripheral surface of the fitting hole and the small diameter portion and the large diameter portion, respectively, when the fixed shaft portion is fitted into the fitting hole; a pressurized aperture that is opened in a gap between the inner circumferential surface of the hole and supplies a surface pressure adjusting fluid into the gap; and a fluid supply means that selectively supplies one of a plurality of types of fluid from a plurality of fluid supply sources into the fitting hole and supplies it to the rotary flow path via the fixed flow path, and supplies the surface pressure adjusting fluid to the pressurized aperture. The second shaft seal portion is provided with an O-ring that is freely mounted in the mounting groove for the O-ring, and is arranged so as to be in contact with the low pressure side of the mounting groove and the entire circumference of the sliding surface with the fixed shaft portion, and is provided with a wave washer made of resin or elastomer that is disposed in the mounting groove. The low pressure side of the mounting groove is pressed with an overall pressing force of 5N or more and a pressing force per crest of 25N or less, and a force in the opposite direction to the pressing force by the wave washer is applied by the residual pressure when the supply of the surface pressure adjusting fluid is stopped, thereby releasing the pressure. The fluid pressure of the fluid supplied to the other side end face of the fixed shaft portion is applied to press the fixed seal portion against the rotating seal portion, thereby bringing the first seal surface and the second seal surface into close contact with each other to form a surface seal portion, and the surface pressure adjusting fluid is fed into the gap through the pressurized opening to apply the surface pressure adjusting fluid pressure to the step portion,The present invention is characterized in that a force in the opposite direction to the pressing force of the fluid pressure is applied to the stationary seal portion, thereby reducing the sealing surface pressure of the face seal portion.

[0010] According to the rotary seal mechanism of the present invention, the O-ring is moderately pressed against the low-pressure side of the mounting groove by a resin or elastomer wave washer with an overall pressing force of 5 N or more and a pressing force per crest of 25 N or less.When the supply of the surface-pressure adjusting fluid is stopped, the O-ring is pushed back against the pressing force of the wave washer by the residual pressure of the surface-pressure adjusting fluid, thereby depressurizing the O-ring, thereby achieving both moderate pressing and release of residual pressure.

[0011] If the total pressing force of the wave washer against the O-ring is less than 5N, the pressing force of the wave washer is too weak to overcome the frictional resistance between the fixed shaft and the O-ring, and it may not be possible to press the O-ring against the wall of the mounting groove on the side that has the gap to seal. Also, if the pressing force per crest of the wave washer exceeds 25N, it becomes difficult to release the seal due to the residual pressure of the surface pressure adjusting fluid, and with a commonly used hardness of O-ring, the deformation of the O-ring due to only the crest of the wave washer being pressed becomes excessive, compromising the sealing ability of the parts that are not pressed, which may impair the sealing ability that should be achieved.

[0012] Furthermore, when the wave washer is made of metal, the elastic modulus of the material itself is high, so in order to obtain the desired pressing force, i.e., a pressing force of 5N or more overall and 25N or less per crest, it needs to be made thin, but if it is made thin, the O-ring may be damaged and the sealing performance may be impaired when it is attached or when it is dragged when the fixed shaft part moves and the O-ring deforms and protrudes into the gap between the fixed shaft part and the wave washer. Therefore, in the present invention, the wave washer is made of resin or elastomer, ensuring a thickness that is less likely to deform when attached in order to obtain the desired pressing force, and as a result, even if it is dragged when the fixed shaft part moves, the O-ring is not damaged and the sealing performance is not impaired.

[0013] The rotary joint of the present invention is a rotary joint used in a fluid delivery mechanism that comprises a rotating part provided with an axial rotary flow passage and a fixed part provided with an axial fixed flow passage, and delivers a fluid supplied from a fluid supply source to the rotary flow passage of the rotating part that rotates around an axis, via the fixed flow passage, and includes a rotary seal part provided in the rotating part and having a first seal surface with the rotary flow passage opening on a side end face, and a fixed seal part having a fixed shaft part with a fixed flow passage formed therethrough in the axial direction, and having a second seal surface with the fixed flow passage opening on one side end face. a fitting hole provided in a housing member constituting a main body of the fixed portion and into which the fixed shaft portion is fitted while allowing movement in the axial direction; a step portion dividing the fixed shaft portion into a large diameter portion having a shaft diameter that fits into the fitting hole and a small diameter portion having a shaft diameter smaller than that of the large diameter portion and provided close to the second seal surface side; a first shaft seal portion and a second shaft seal portion that respectively seal gaps between the inner peripheral surface of the fitting hole and the small diameter portion and the large diameter portion when the fixed shaft portion is fitted into the fitting hole; and a pressurized opening for supplying a surface pressure adjusting fluid into the gap, and the second shaft seal portion is arranged so that an O-ring is freely attached to the attachment groove of the O-ring, and is capable of contacting the low-pressure side of the attachment groove and the entire circumference of the sliding surface with the fixed shaft portion, and is pressed against the low-pressure side of the attachment groove with a total pressing force of 5 N or more and a pressing force per crest of 25 N or less by a wave washer made of resin or elastomer provided in the attachment groove, and the pressing force by the wave washer is controlled by the residual pressure when the supply of the surface pressure adjusting fluid is stopped. The pressure is released by applying a force in the opposite direction to the pressing force due to the fluid pressure, in which fluid is supplied from a fluid supply source into the fitting hole to apply fluid pressure to the other side end face of the fixed shaft portion and press the fixed seal portion against the rotating seal portion, thereby bringing the first seal surface and the second seal surface into close contact with each other to form a face seal portion, and a face pressure adjusting fluid is supplied into the gap through a pressurized opening to apply a face pressure adjusting fluid pressure to the step portion, thereby applying a force on the fixed seal portion in the opposite direction to the pressing force due to the fluid pressure and reducing the seal face pressure of the face seal portion.

[0014] According to the rotary joint of the present invention, the O-ring is moderately pressed against the low-pressure side of the mounting groove by a resin or elastomer wave washer with an overall pressing force of 5 N or more and a pressing force per crest of 25 N or less. When the supply of the surface-pressure adjusting fluid is stopped, the O-ring is pushed back against the pressing force of the wave washer by the residual pressure of the surface-pressure adjusting fluid, thereby releasing the pressure, thereby achieving both moderate pressing and release of residual pressure. Effect of the Invention

[0015] According to the present invention, the pressure is released when the supply of the surface pressure adjusting fluid is stopped, thereby preventing the surface pressure from remaining applied, and it is possible to realize a rotary seal mechanism in a fluid delivery mechanism that is free of operational malfunctions, and a rotary joint used in this rotary seal mechanism. [Brief description of the drawings]

[0016] [Figure 1] 1 is a configuration explanatory diagram of a fluid delivery mechanism according to an embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a rotary joint used in a rotary seal mechanism of a fluid feed mechanism according to an embodiment of the present invention. [Diagram 3] 3A to 3C are explanatory views of the structure of a housing member of a rotary joint according to one embodiment of the present invention. [Figure 4] 1 is a structural explanatory diagram of a floating seat of a rotary joint in one embodiment of the present invention. FIG. [Diagram 5] FIG. 4 is a cross-sectional view showing the seal structure of a second shaft seal portion. [Figure 6] 1A and 1B are diagrams showing a pressing spring, in which FIG. 1A is a front view and FIG. [Figure 7] 5A to 5C are diagrams illustrating the operation of a rotary joint according to an embodiment of the present invention. [Figure 8] 5A to 5C are diagrams illustrating the operation of a rotary joint according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Figure 1 is an explanatory diagram of the configuration of a fluid supply mechanism in one embodiment of the present invention, Figure 2 is a cross-sectional view of a rotary joint used in the rotary seal mechanism of the fluid supply mechanism in one embodiment of the present invention, Figure 3 is an explanatory diagram of the structure of a housing member of a rotary joint in one embodiment of the present invention, Figure 4 is an explanatory diagram of the structure of a floating seat of a rotary joint in one embodiment of the present invention, Figure 5 is a cross-sectional view showing the seal structure of a second shaft seal portion, Figure 6 is a diagram showing a pressing spring, where (a) is a front view and (b) is a partially enlarged side view, and Figures 7 and 8 are explanatory diagrams of the operation of a rotary joint in one embodiment of the present invention.

[0018] First, the overall configuration of the fluid feed mechanism 1 will be described with reference to Fig. 1. In Fig. 1, the fluid feed mechanism 1 has a function of feeding a cooling fluid supplied from a fluid supply unit 7 to a rotating shaft such as a spindle of a machine tool. The fluid feed mechanism 1 mainly comprises a rotary joint 2 that is configured by coaxially arranging a rotating part 2a provided with an axial rotating flow passage and a fixed part 2b provided with an axial fixed flow passage.

[0019] The rotating part 2a is fastened to a fastening hole 4a of a spindle shaft 4. The spindle shaft 4 is driven to rotate by a motor built into the spindle and rotates about an axis A within an insertion hole 5a provided in a frame 5, and moves forward and backward in the axial direction by a clamp / unclamp cylinder. The fixed part 2b is mounted by fitting into a mounting hole 3a provided in a casing 3 having a cylindrical block shape. The fixed part 2b is arranged coaxially with the rotating part 2a by detachably fastening the casing 3 to the frame 5 by fastening means such as bolts (not shown).

[0020] The fluid supply unit 7 includes a first fluid supply source 7a and a second fluid supply source 7b. The first fluid supply source 7a supplies liquid coolant (first fluid), and the second fluid supply source 7b supplies air (second fluid). The air supplied from the second fluid supply source 7b can be selected from various forms depending on the object to be supplied, such as general factory air, dry air obtained by processing factory air with a dryer, or oil-mist-containing air in which a predetermined amount of oil mist has been mixed in.

[0021] The fluid supplied from the fluid supply unit 7 is selectively delivered by a fluid supply circuit 6 equipped with a first on-off valve 6a, a second on-off valve 6b and a check valve 6c. That is, the first fluid supply source 7a is connected to the flow passage hole 3b of the casing 3 via the first on-off valve 6a by a coolant pipe 8a made of a pressure-resistant pipe. By opening and closing the first on-off valve 6a, the delivery of the liquid coolant supplied from the first fluid supply source 7a to the fixed part 2b can be turned on and off.

[0022] The second fluid supply source 7b is connected to the coolant pipe 8a by an air pipe 8b made of a resin tube or the like, via a second opening / closing valve 6b and a check valve 6c. By opening and closing the second opening / closing valve 6b, the supply of air from the second fluid supply source 7b to the fixed part 2b can be turned on and off. The check valve 6c is provided to prevent backflow of fluid from the coolant pipe 8a to the air pipe 8b. Furthermore, the air pipe 8c branched off downstream of the second opening / closing valve 6b is connected to a pressurizing opening 20 (see FIG. 2) provided in the fixed part 2b. When the fluid to be supplied is air, the air pipe 8c supplies air as a surface pressure adjusting fluid to the fixed part 2b as described later.

[0023] That is, in the above configuration, by switching the first opening / closing valve 6a and the second opening / closing valve 6b according to the workpiece in the machine tool, the type of cooling fluid to be fed can be selected and switched, and for a specific fluid, a surface pressure adjusting fluid can be fed to the fixed part 2b. Therefore, the fluid supply circuit 6 shown in FIG. 1 serves as a fluid supplying means that selectively supplies one of a plurality of types of fluid from a plurality of fluid supply sources to the fitting hole 13a described later, feeds the fluid to the rotary flow path 10a of the rotating part 2a via the fixed flow path 15d of the fixed part 2b, and feeds the surface pressure adjusting fluid to the pressurizing opening 20 (see FIG. 2). The rotary joint 2 and the fluid supply circuit 6 constitute a rotary seal mechanism that has the function of selectively feeding a plurality of types of fluid supplied from a plurality of fluid supply sources to the rotary flow path 10a of the rotating part 2a that rotates around the axis via the fixed flow path 15d of the fixed part 2b.

[0024] Next, the detailed structure of the rotary joint 2 will be described with reference to Figures 2, 3, and 4. In Figure 2, the rotating part 2a mainly consists of a rotor 10 having a rotation flow passage 10a penetrating axially through its axial center and a fastening screw portion 10b on its outer surface. The rotor 10 is screwed to the spindle shaft 4 by screwing the fastening screw portion 10b into a fastening hole 4a, and the screw fastening portion is sealed by an O-ring 12. As a result, the rotation flow passage 10a communicates with the flow passage hole 4b of the spindle shaft 4.

[0025] A ring-shaped annular protrusion 10c is formed on the side end surface of the right side (opposite the fixed part 2b) of the rotor 10 in an arrangement surrounding the opening surface of the rotary flow passage 10a. A first seal ring 11 is fixed to a recess formed inside the ring-shaped protrusion 10c. The first seal ring 11 is made of a hard material such as ceramic that is highly wear-resistant and is molded into a ring shape with an opening 11a in the center. The first seal ring 11 is fixed to the ring-shaped protrusion 10c with the first seal surface 11b, which is finished to a smooth surface, facing outward. In this state, the rotary flow passage 10a communicates with the opening 11a and opens to the first seal surface 11b. That is, the rotor 10 to which the first seal ring 11 is fixed is a rotary seal part having the first seal surface 11b, which is provided on the rotary part 2a and has the rotary flow passage 10a opening on the side end surface.

[0026] Next, the structure of the fixed part 2b mounted on the casing 3 will be described. A mounting hole 3a is provided in the mounting surface 3c of the casing 3 so as to communicate with the flow passage hole 3b. A mounting protrusion 13b provided on a cylindrical housing member 13 constituting the main body of the fixed part 2b is fitted into the mounting hole 3a. As shown in FIG. 3, the housing member 13 is bolted to the casing 3 by screwing a plurality of equally spaced bolts 14 into threaded holes 3d provided in the mounting surface 3c, and the fitting portion of the mounting protrusion 13b is sealed by an O-ring 16. A fitting hole 13a is provided in the center of the housing member 13, penetrating in the axial direction, and O-ring grooves 13c and 13d are provided on the inner peripheral surface of the fitting hole 13a.

[0027] 2, the floating seat 15 has a disk-shaped flange portion 15a on one side (the side facing the rotating portion 2a in the figure) and a fixed shaft portion 15b on the other side with a fixed flow passage 15d formed therethrough in the axial direction. The fixed shaft portion 15b fits into the fitting hole 13a of the housing member 13 in a state in which axial movement is permitted.

[0028] An annular convex portion 15c is formed on the left side end surface of the flange portion 15a (the side facing the rotating portion 2a) in an arrangement surrounding the opening surface of the fixed flow passage 15d. A second seal ring 17 is fixed to a recess formed inside the annular convex portion 15c. The second seal ring 17 is made of the same hard material as the first seal ring 11 and is formed in an annular shape with an opening 17a in the center. The second seal ring 17 is fixed to the annular convex portion 15c with the second seal surface 17b, which is finished to a smooth surface, facing outward. In this state, the fixed flow passage 15d communicates with the opening 17a and opens to the second seal surface 17b. That is, the floating seat 15 to which the second seal ring 17 is fixed has a fixed shaft portion 15b formed with the fixed flow passage 15d penetrating in the axial direction, and is a fixed seal portion having a second seal surface 17b with the rotary flow passage 10a opening on the side end surface.

[0029] The detailed shape of the floating seat 15 will be described with reference to FIG. 4. The flange portion 15a is provided with cutout portions 15j at equally spaced positions corresponding to the positions of the bolts 14 shown in FIG. 3, and the floating seat 15 can be bolted to the casing 3 of the housing member 13 when the floating seat 15 is attached to the housing member 13. The second seal surface 17b of the second seal ring 17 is formed with a plurality of recesses 17c for sealing surface lubrication. The recesses 17c have the function of guiding the fluid in the opening 17a to the sliding surface between the first seal surface 11b and the second seal surface 17b to improve lubrication when the second seal surface 17b is in close contact with the first seal surface 11b to form a surface seal portion. The recesses 17c are not essential, and may not be required depending on the sliding conditions such as the characteristics of the target fluid, the seal surface pressure value, and the rotational speed used.

[0030] Fixed shaft portion 15b is divided by step portion 15g provided in the middle portion in the longitudinal direction into small diameter portion 15e with outer diameter D1 provided at a position close to second seal ring 17 and large diameter portion 15f with outer diameter D2 larger than outer diameter D1 and sized to fit into fitting hole 13a. Here, the side area of ​​side end face 15h of large diameter portion 15f, that is, the side area obtained by removing fixed flow passage 15d with inner diameter d from the circle of outer diameter D2, is A1, and the side area obtained by removing the cross-sectional area of ​​small diameter portion 15e from the circle of outer diameter D2 at step portion 15g is A2.

[0031] As shown in Fig. 2, when the fixed shaft portion 15b is fitted into the fitting hole 13a, the O-ring grooves 13c and 13d (see Fig. 3) are located at the small diameter portion 15e and the large diameter portion 15f of the fixed shaft portion 15b, respectively. The O-ring groove 13c is a groove for fitting the O-ring 21a. When the O-ring 21a is fitted into the O-ring groove 13c, it constitutes the first shaft seal portion 21.

[0032] The O-ring groove 13c is formed to have a depth such that the outer periphery of the O-ring 21a does not contact the bottom of the groove when the O-ring 21a is attached, and a groove width that is appropriately wider than the cross-sectional thickness of the O-ring. The inner diameter of the O-ring 21a is large enough that the O-ring 21a makes contact with the outer periphery of the small diameter portion 15e of the fixed shaft portion 15b over the entire circumference when attached to the O-ring groove 13c.

[0033] The O-ring groove 13d is a groove for mounting the O-ring 22a. In addition to the O-ring 22a, a pressing spring 26 is mounted in the O-ring groove 13d. When the O-ring 22a and the pressing spring 26 are mounted in the O-ring groove 13d, the second shaft seal portion 22 is configured.

[0034] The O-ring groove 13d is formed so that the outer periphery of the O-ring does not contact the groove bottom 13e when the O-ring 22a is attached, and the groove width is appropriately wider than the cross-sectional thickness of the O-ring. The inner diameter of the O-ring 22a is large enough that the O-ring 22a contacts the outer periphery of the large diameter portion 15f of the fixed shaft portion 15b all around when attached to the O-ring groove 13d. In other words, the O-ring 22a is not set in a compressed state, but is set in a free state, and is simply made to contact the low-pressure side wall 13g (see FIG. 5) of the O-ring groove 13d and the sliding surface of the fixed shaft portion 15b.

[0035] The pressing spring 26 for the O-ring 22a presses the O-ring 22a against the low pressure side of the O-ring groove 13d, i.e., against the rotor 10, thereby sealing the gap that occurs on the low pressure side. As shown in Fig. 6(a), the pressing spring 26 is a wave washer formed of a spring material into a ring-shaped corrugated body portion 26a having substantially the same inner and outer diameters as the O-ring 22a and a peripheral surface corrugated in the axial direction. The number of wave periods is three or more.

[0036] The total pressing force of pressing spring 26 is set to 5 N or more so that the pressing force is higher than the external force caused by sliding resistance when the shaft slides. Also, O-ring groove 13d has a space that does not lose the wave shape of pressing spring 26 when O-ring 22a and pressing spring 26 are attached, and the tops of the waves of pressing spring 26 come into contact with O-ring 22a, but the spring constant of pressing spring 26 and the compression distance of the spring when attached are set so that the pressing force does not exceed 25 N per crest, that is, is 25 N or less per crest.

[0037] In addition, the pressing spring 26 in this embodiment is made using the resin PTFE (polytetrafluoroethylene (Teflon (registered trademark))) as the spring material, but it may be made of other resins or elastomers.

[0038] Fig. 5 shows the set state. The pressing spring 26 is set so as to press the side of the O-ring 22a from the high pressure side to the low pressure side, that is, on the higher pressure side than the O-ring 22a within the O-ring groove 13d. In this case, the corrugated body portion 26a presses the O-ring 22a with its back side in contact with the groove side wall, and the O-ring 22a is evenly attached to the low pressure side wall 13g of the O-ring groove 13d all around.

[0039] With the above configuration, when the fixed shaft portion 15b is fitted into the fitting hole 13a, the first shaft seal portion 21 and the second shaft seal portion 22 seal the gaps 27 (see FIG. 5) between the inner circumferential surface of the fitting hole 13a and the small diameter portion 15e and the large diameter portion 15f. In this state, the pressure of the fluid in the fitting hole 13a acts on the side end surface 15h with a pressure-receiving area A1.

[0040] The housing member 13 is provided with a pressurized opening 20 connected to the air pipe 8c shown in Fig. 1. The pressurized opening 20 opens in an annular gap 23 between the small diameter portion 15e and the inner circumferential surface of the fitting hole 13a, between the first shaft seal portion 21 and the second shaft seal portion 22. In this state, air is supplied from the second fluid supply source 7b through the air pipe 8c, so that air is supplied into the annular gap 23 as a surface pressure adjusting fluid. The pressure of the fluid in the annular gap 23 acts on the step portion 15g having a pressure receiving area A2.

[0041] When the fluid to be supplied is fed into the flow passage hole 3b, the fluid pressure acts on the side end face 15h on the other side (opposite the second seal ring 17) of the fixed shaft portion 15b. As a result, the fixed shaft portion 15b slides toward the rotating portion 2a inside the fitting hole 13a, and the second seal ring 17 is pressed against the first seal ring 11. This pressing force brings the second seal surface 17b and the first seal surface 11b into close contact with each other, thereby forming a face seal portion 18 that prevents leakage of the fluid fed from the fixed flow passage 15d to the rotary flow passage 10a that is rotating about the axis. When the floating seat 15 slides, the bolt 24 screwed into the screw hole 15i (Figure 4) of the flange portion 15a and the cylindrical collar 25 surrounding the bolt 24 slide within the guide hole 13f provided in the axial direction in the housing member 13, thereby guiding the axial movement of the floating seat 15 and preventing it from rotating around the axis.

[0042] When the rotary joint 2 is in operation, the floating seat 15 advances due to the pressure of the fluid being fed, and the seal surfaces of the face seal portion 18 come into contact with and separate from each other due to the advancement and reciprocation of the spindle shaft 4. That is, when the floating seat 15 retreats and the first seal surface 11b and the second seal surface 17b are separated from each other, fluid is fed into the fitting hole 13a through the flow path hole 3b, causing the floating seat 15 to advance (in the direction of arrow a), and the first seal surface 11b comes into contact with the second seal surface 17b, thereby forming the face seal portion 18.

[0043] Then, as the spindle shaft 4 advances (in the direction of arrow d) relative to the fixed portion 2b, the floating seat 15 retreats (in the direction of arrow b), and the flange portion 15a returns to a position close to the housing member 13. Then, by relatively retreating (in the direction of arrow c) from this state, the first seal surface 11b and the second seal surface 17b return to a state in which they are separated from each other. At this time, the O-ring 22a is pressed by the pressing spring 26 and returns to a contact state between the fixed shaft portion 15b and the low-pressure side wall 13g of the O-ring groove 13d, so that good sealing can be ensured without causing leakage the next time fluid is supplied. Note that if the pressing force of the pressing spring 26 exceeds 25 N per peak, the O-ring 22a will be deformed due to excessive compression, causing a gap to be generated between the fixed shaft portion 15b and the low-pressure side wall 13g of the O-ring groove 13d, making it impossible to ensure good sealing.

[0044] Next, the operation of the rotary joint 2 when multiple types of fluids are fed will be described with reference to Figures 7 and 8. Figures 7 and 8 show the cases where the fed fluids are liquid coolant and air, respectively. First, the case where the supplied fluid is liquid coolant will be described.

[0045] In FIG. 7, by opening the first opening / closing valve 6a, liquid coolant (pressure P1) is supplied from the first fluid supply source 7a into the fitting hole 13a. This liquid coolant flows through the fixed passage 15d to the rotary passage 10a. At this time, the pressure P1 acts on the side end face 15h in the fitting hole 13a, and a fluid force F(L) corresponding to the pressure-receiving area A1 (see FIG. 4) of the side end face 15h acts on the fixed shaft portion 15b. Then, a pressing force F1, which is the fluid force F(L) minus the sliding resistances f1 and f2 of the first shaft seal portion 21 and the second shaft seal portion 22, acts on the face seal portion 18. The value obtained by dividing this pressing force F1 by the seal area where the first seal surface 11b and the second seal surface 17b contact each other, is the seal surface pressure value of the face seal portion 18.

[0046] Next, a case where the fluid to be supplied is air will be described. In Fig. 8, by opening the second opening / closing valve 6b, air (pressure P2) is supplied from the second fluid supply source 7b through the check valve 6c into the fitting hole 13a, and air (pressure P2) is also supplied to the pressurized opening 20. The air supplied into the fitting hole 13a flows into the rotary flow path 10a via the fixed flow path 15d. At this time, the pressure P2 acts on the side end surface 15h in the fitting hole 13a, and a fluid force F (G1) corresponding to the pressure-receiving area A1 (see Fig. 4) acts on the fixed shaft portion 15b.

[0047] Furthermore, the air fed to the pressurized opening 20 acts on the step 15g within the annular gap 23, and a fluid force F (G2) commensurate with the pressure-receiving area A2 (see FIG. 4) acts in the opposite direction to the fluid force F (G1). A pressing force F2, which is the fluid force F (G1) minus the sliding resistances f1, f2 and the fluid force F (G2), acts on the face seal portion 18. In this case, the value obtained by dividing the pressing force F2 by the seal area is the seal face pressure value.

[0048] Here, the seal surface pressure in a rotary joint will be described. In a rotary seal mechanism that seals a fluid by bringing rotating sliding surfaces into close contact, it is necessary to set an appropriate seal surface pressure value according to the characteristics and supply pressure of the target fluid. For example, as in this embodiment, when the target is liquid coolant, which is often supplied at a relatively high supply pressure (for example, 1 MPa to 20 MPa), a seal surface pressure value is set at approximately the same level as the supply pressure to prevent leakage from the seal surface as much as possible.

[0049] On the other hand, when air is used at a low supply pressure (for example, 0.1Mpa to 1Mpa), the seal surface pressure must be less than half the supply pressure in order to prevent wear caused by sliding on the seal surface as much as possible. This is because, when liquid is supplied, a thin film of liquid that penetrates the seal surface acts as a lubricating film that lubricates the sliding surface, whereas air generally does not have such a lubricating effect, except in cases where lubrication measures such as mixing in oil mist are taken.

[0050] In this way, when fluids with different supply pressures or desired seal surface pressure values ​​are to be supplied, the ratio of the seal surface pressure value to the supply pressure must be changed according to the fluid. Here, since the seal area of ​​the face seal portion is the same for all fluids, in order to change the ratio of the seal surface pressure value to the supply pressure, the pressure-receiving area on which the fluid pressure acts must be made different according to the type of fluid. In this embodiment, as shown in FIG. 8, when air, which requires a low seal surface pressure value, is used, the substantial pressure-receiving area that generates the pressing force acting on the face seal portion 18 is (A1-A2), which is different from the pressure-receiving area A1 when liquid coolant is used.

[0051] That is, in the case shown in Figure 8, air as a surface pressure adjusting fluid is supplied into the annular gap 23 through the pressurized opening 20 to apply air pressure (surface pressure adjusting fluid pressure) to the step portion 15g, thereby applying a fluid force F (G2) in the opposite direction to the pressing force F (G1) due to the fluid pressure acting on the side end face 15h to the floating sheet 15, which is the fixed seal portion, thereby reducing the sealing surface pressure of the face seal portion 18.

[0052] When designing rotary joint 2, the dimensions of each part are set so that the seal surface pressure value of face seal portion 18 due to pressing force F1 shown in Fig. 7 is an appropriate value for the liquid coolant at pressure P1, and the seal surface pressure value of face seal portion 18 due to pressing force F2 shown in Fig. 8 is an appropriate value for air at pressure P2. That is, diameter dimensions D1, D2 of small diameter portion 15e and large diameter portion 15f, diameter dimension d of fixed flow path 15d, etc. are determined based on the above-mentioned pressures P1, P2, appropriate seal surface pressure values ​​for each fluid, the above-mentioned sliding resistances f1, f2, etc., which are given design numerical data.

[0053] In the rotary joint 2 shown in this embodiment, when the supply of surface pressure adjustment air is stopped, O-ring 22a, which is pressed against low-pressure side wall 13g of O-ring groove 13d by pressing spring 26, is depressurized by being pushed back by a force in the opposite direction to the pressing force of pressing spring 26 due to the residual pressure of the surface pressure adjustment air, which is higher than the pressing force of pressing spring 26. Therefore, it is possible to prevent internal pressure from remaining applied when the supply of surface pressure adjustment air is stopped, and it is possible to eliminate malfunction of face seal portion 18 due to residual pressure in first shaft seal portion 21 and second shaft seal portion 22. [Industrial Applicability]

[0054] The rotary seal mechanism and rotary joint in the fluid supply mechanism of the present invention have the characteristic of being able to rationally adjust surface pressure, and are useful for supplying liquid coolant and air to rotating parts such as the spindle of a machine tool. [Explanation of symbols]

[0055] 1 Fluid feeding mechanism 2 Rotary joint 2a Rotating part 2b Fixed part 4 Spindle Axis 6 Fluid supply circuit 7 Fluid supply section 7a First fluid supply source 7b Second fluid source 10 Rotor 10a Rotating channel 11 First seal ring 11b first seal surface 13 Housing material 13a Fitting hole 13d O-ring groove 13e groove bottom 13g Low pressure side wall 15 Floating Seat 15a Flange part 15b Fixed shaft part 15d Fixed channel 15e Small diameter section 15f Large diameter section 15g Step 16 O-ring 17 Second seal ring 17b Second sealing surface 18 Face seal part 20 Pressurized opening 21 First shaft seal 21a O-ring 22 Second shaft seal 22a O-ring 23 Annular gap 26 Pressing spring

Claims

1. A rotary seal mechanism in a fluid supply mechanism, which comprises a rotary part provided with an axial rotary flow passage and a fixed part provided with an axial fixed flow passage, and which selectively supplies two types of fluid, which are supplied from two fluid supply sources and have different ratios between supply pressure and appropriate seal surface pressure value, to the rotary flow passage of the rotary part rotating about an axis, via the fixed flow passage, a rotary seal portion provided on the rotary portion and having a first seal surface on a side end surface of the rotary flow path; a stationary seal portion having a stationary shaft portion with the stationary flow passage formed therethrough in the axial direction and having a second seal surface on one side end surface of the stationary flow passage opening thereto; a fitting hole provided in a housing member constituting a main body of the fixed portion, into which the fixed shaft portion is fitted while allowing movement in the axial direction; a step portion that divides the fixed shaft portion into a large diameter portion having a shaft diameter that fits into the fitting hole and a small diameter portion having a shaft diameter smaller than that of the large diameter portion and provided close to the second seal surface side; a first shaft seal portion and a second shaft seal portion that seal gaps between an inner circumferential surface of the fitting hole and the small diameter portion and between the inner circumferential surface of the fitting hole and the large diameter portion when the fixed shaft portion is fitted into the fitting hole; a pressurizing hole that is opened in a gap between the small diameter portion and an inner circumferential surface of the fitting hole between the first shaft seal portion and the second shaft seal portion and that supplies a surface pressure adjusting fluid into the gap; a fluid supply means for selectively supplying any one of the plurality of types of fluid from the plurality of fluid supply sources into the fitting hole and feeding the fluid to the rotary flow path via the fixed flow path, and for feeding a surface pressure adjusting fluid to the pressurizing opening, the second shaft seal portion is configured such that an O-ring is freely mounted in the mounting groove of the O-ring, and is arranged so as to be in contact with the low-pressure side of the mounting groove and the entire circumference of the sliding surface with the fixed shaft portion, and a resin or elastomer wave washer is provided in the mounting groove and presses against the low-pressure side of the mounting groove with an overall pressing force of 5 N or more and a pressing force per crest of 25 N or less, and the residual pressure when the supply of the surface pressure adjusting fluid is stopped applies a force in the opposite direction to the pressing force of the wave washer to release the pressure, a fluid pressure of the supplied fluid is applied to the other side end surface of the stationary shaft portion to press the stationary seal portion against the rotary seal portion, thereby bringing the first seal surface and the second seal surface into close contact with each other to form a face seal portion; A rotary seal mechanism in a fluid supply mechanism, characterized in that the surface pressure adjustment fluid is supplied into the gap through the pressurized opening, and a surface pressure adjustment fluid pressure is applied to the step portion, thereby applying a force to the fixed seal portion in the opposite direction to the pressing force due to the fluid pressure, thereby reducing the sealing surface pressure of the face seal portion.

2. A rotary joint used in a fluid supply mechanism that comprises a rotating part having an axial rotary flow passage and a fixed part having an axial fixed flow passage, the rotary joint being used in a fluid supply mechanism that supplies a fluid supplied from a fluid supply source to the rotary flow passage of the rotating part that rotates about an axis, via the fixed flow passage, the rotary joint comprising: a rotary seal portion provided on the rotary portion and having a first seal surface on a side end surface of the rotary flow path; a stationary seal portion having a stationary shaft portion with the stationary flow passage formed therethrough in the axial direction and having a second seal surface on one side end surface of the stationary flow passage opening thereto; a fitting hole provided in a housing member constituting a main body of the fixed portion, into which the fixed shaft portion is fitted while allowing movement in the axial direction; a step portion that divides the fixed shaft portion into a large diameter portion having a shaft diameter that fits into the fitting hole and a small diameter portion having a shaft diameter smaller than that of the large diameter portion and provided close to the second seal surface side; a first shaft seal portion and a second shaft seal portion that seal gaps between an inner circumferential surface of the fitting hole and the small diameter portion and between the inner circumferential surface of the fitting hole and the large diameter portion when the fixed shaft portion is fitted into the fitting hole; a pressurizing hole that is opened in a gap between the small diameter portion and an inner circumferential surface of the fitting hole between the first shaft seal portion and the second shaft seal portion and that supplies a surface pressure adjusting fluid into the gap, the second shaft seal portion is configured such that an O-ring is freely mounted in the mounting groove of the O-ring, and is arranged so as to be in contact with the low-pressure side of the mounting groove and the entire circumference of the sliding surface with the fixed shaft portion, and a resin or elastomer wave washer is provided in the mounting groove and presses against the low-pressure side of the mounting groove with an overall pressing force of 5 N or more and a pressing force per crest of 25 N or less, and the residual pressure when the supply of the surface pressure adjusting fluid is stopped applies a force in the opposite direction to the pressing force of the wave washer to release the pressure, a fluid supply source for supplying the fluid into the fitting hole to apply fluid pressure to the other side end surface of the fixed shaft portion and to press the stationary seal portion against the rotary seal portion, thereby bringing the first seal surface and the second seal surface into close contact with each other to form a face seal portion; A rotary joint characterized in that the surface pressure adjusting fluid is supplied into the gap through the pressurized opening, and a surface pressure adjusting fluid pressure is applied to the step portion, thereby applying a force to the fixed seal portion in the opposite direction to the pressing force due to the fluid pressure, thereby reducing the sealing surface pressure of the face seal portion.

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