JP7460838B1 - Rotary seal mechanism and rotary joint in fluid delivery mechanism - Google Patents

Abstract

[Problem] To provide a rotary seal mechanism and a rotary joint in a fluid delivery mechanism capable of releasing pressure after the supply of a surface pressure adjusting fluid is stopped. [Solution] In a rotary joint 2 used in a fluid delivery mechanism that delivers multiple types of fluids supplied from a fluid supply source to a rotating part 2a that rotates around an axis via a fixed part 2b, a second shaft seal part 22 has an O-ring 22a freely attached to a mounting groove of the O-ring 22a, 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 part, and is pressed against the low-pressure side of the mounting groove with a total pressing force of 5N or more and a pressing force per crest of 25N or less by a pressing spring 26 which is a wave washer made of resin or elastomer and is provided in the mounting groove, and the residual pressure when the supply of surface pressure adjusting air from a pressurizing aperture 20 is stopped applies a force in the opposite direction to the pressing force of the pressing spring 26 to release pressure. [Selected Figure] Figure 2

Description

The present invention relates to a rotary seal mechanism in a fluid delivery mechanism for delivering fluid to a rotating part, and a rotary joint used in this rotary seal mechanism.

Used as a fluid coupling that connects fixed fluid supply piping to the flow path of the rotating part in a fluid delivery mechanism that supplies cooling coolant or other fluid to rotating parts that are rotating during operation, such as the main shaft of a machine tool. A rotary joint is used. A rotary joint consists of a rotary shaft that is connected to a rotating part and rotates, and a fixed shaft that is connected to a fluid feeding mechanism, arranged coaxially and facing each other in the axial direction, and a rotary seal attached to each opposing end surface. It has a structure that prevents fluid leakage by bringing the surfaces into close contact with each other.

In recent years, air has come to be 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 of providing appropriate cooling characteristics for the object being cooled, and reducing the environmental impact by eliminating the need for environmental measures such as wastewater treatment after use. When it is necessary to use both liquid coolant and air in the same device, the rotary joint used as a fluid coupling must be designed to be usable with both liquids and gases, which have different fluid properties, and rotary joints designed for such uses have been proposed (see, for example, Patent Document 1).

The example shown in Patent Document 1 is a rotary joint used in a fluid feeding mechanism that feeds multiple types of fluids supplied from a fluid supply source to a rotating part that rotates around an axis via a fixed part. When supplying a type of fluid that requires a low sealing surface pressure value by providing a stepped portion on the outer peripheral surface of the fixed shaft that fits into the fitting hole and moves in the axial direction, pressurized opening is required. Constructed so that the surface pressure adjusting fluid introduced through the hole acts on the stepped portion to apply a force in the opposite direction to the pressing force caused by the fluid pressure on the fixed seal portion, thereby reducing the seal surface pressure of the surface seal portion. This is what I did.

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 using 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.

JP2008-64274A

However, when the supply of the surface pressure adjusting air is stopped, the sealing properties of the first shaft seal portion and the second shaft seal portion are maintained. Therefore, internal pressure remains in the space between the first shaft seal part and the second shaft seal part, and this internal pressure causes the first shaft seal part and the second shaft seal part to tighten the fixed shaft part. This may cause the fixed shaft portion to be restrained, resulting in malfunction of the face seal portion.

The present invention aims to provide a rotary seal mechanism in a fluid delivery mechanism that can be depressurized after the supply of surface pressure adjustment fluid is stopped, and a rotary joint used in this rotary seal mechanism.

The rotary seal mechanism of the present invention is a rotary seal mechanism in a fluid supply 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 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 rotating part that rotates around the axis via the fixed flow passage. The rotary seal mechanism comprises a rotary seal part provided in the rotating part and having a first seal surface with the rotary flow passage opening on its side end face, a fixed seal part having a fixed shaft part formed with a fixed flow passage penetrating in the axial direction, and 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, 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 provided with a shaft diameter that fits into the fitting hole and a small diameter portion provided with a shaft diameter smaller than that of the large diameter portion and adjacent 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 between the large diameter portion and the small diameter portion, respectively, when the fixed shaft portion is fitted into the fitting hole; and a hole opening in a gap between the small diameter portion and the inner peripheral surface of the fitting hole between the first shaft seal portion and the second shaft seal portion, and supplying a surface pressure adjusting fluid into the gaps. and a fluid supply means for selectively supplying one of a plurality of types of fluid from a plurality of fluid supply sources into the fitting hole and feeding the fluid to the rotary flow path via the fixed flow path, and feeding a surface pressure adjusting fluid to the pressurizing hole. The second shaft seal portion is configured such that an O-ring is freely attached to the attachment groove of the O-ring, and is arranged so as to be in contact with the low-pressure side surface of the attachment 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 attachment groove and presses against the low-pressure side surface of the attachment groove with an overall pressing force of 5 N or more and a pressing force per crest of 25 N or less. The pressure is released by applying a force in the opposite direction to the pressing force of the wave washer using the residual pressure when the supply of the surface pressure adjusting fluid is stopped, and 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, thereby applying a force in the opposite direction to the pressing force of the fluid pressure to the fixed seal portion, thereby reducing the seal surface pressure of the face seal portion.

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 a total 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 adjustment 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 adjustment fluid, thereby releasing the pressure, thereby achieving both moderate pressing and residual pressure release.

In addition, if the entire 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 part and the O-ring, and the side that holds the gap that seals the O-ring may not be able to be pressed against the wall of the mounting groove. In addition, if the pressing force per peak of the wave washer exceeds 25N, it becomes difficult to release the sealing property due to the residual pressure of the surface pressure adjustment fluid, and the hardness of the commonly used O-ring makes it difficult to release the sealing property of the wave washer. The deformation of the O-ring due to only the peak portions being pressed becomes excessive, and the sealing performance of the portions that are not pressed may be impaired, thereby impairing the sealing performance that should originally be achieved.

In addition, if the wave washer is made of metal, the material itself has a high elastic modulus, so if you try to obtain the desired pressing force, that is, the total pressing force is 5N or more and the pressing force per thread is 25N or less. It is necessary to make it thin, but if it is made thin, the O-ring will be damaged when it is installed or when the fixed shaft part is dragged and deformed and protrudes into the gap between the fixed shaft part and the wave washer. , the sealing performance may be impaired. Therefore, in the present invention, the wave washer is made of resin or elastomer to ensure a thickness that is difficult to deform when installed in order to obtain the desired pressing force. Even if the O-ring is damaged, the O-ring will not be damaged and the sealing performance will not be impaired.

The rotary joint of the present invention is a rotary joint used in a fluid supply 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 supplies a fluid supplied from a fluid supply source to the rotating flow passage of the rotating part that rotates around an axis via the fixed flow passage, and comprises a rotating seal part provided in the rotating part and having a first seal surface with the rotating flow passage opening on its side end face, a fixed shaft part with a fixed flow passage formed therethrough in the axial direction, and 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 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 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 peripheral surface of the fitting hole and the small diameter portion and between the small diameter portion and the large diameter portion, respectively, 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 increased 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 pressure applied by the fluid supply source into the fitting hole, which applies fluid pressure to the other side end surface of the fixed shaft portion and presses 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 by feeding a face pressure adjustment fluid into the gap through the pressurized opening and applying a face pressure adjustment fluid pressure to the step portion, a force in the opposite direction to the pressing force of the fluid pressure is applied to the fixed seal portion, thereby reducing the seal face pressure of the face seal portion.

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 a total 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 adjustment 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 adjustment fluid, thereby releasing the pressure, thereby achieving both moderate pressing and the release of residual pressure.

According to the present invention, since the pressure is released when the supply of the surface pressure adjustment fluid is stopped, it is possible to prevent the surface pressure from remaining applied, and the rotary seal mechanism and the rotary seal mechanism in the fluid feeding mechanism are free from malfunction. A rotary joint used in a rotary seal mechanism can be realized.

FIG. 2 is a configuration explanatory diagram of a fluid feeding mechanism in an embodiment of the present invention. 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. FIG. 2 is a structural explanatory diagram of a housing member of a rotary joint in an embodiment of the present invention. FIG. 2 is a structural explanatory diagram of a floating seat of a rotary joint in an embodiment of the present invention. 4 is a cross-sectional view showing the seal structure of a second shaft seal portion. FIG. It is a figure which shows a pressing spring, Comprising: (a) is a front view, (b) is a partially enlarged side view. It is an explanatory diagram of operation of a rotary joint in one embodiment of the present invention. It is an explanatory diagram of operation of a rotary joint in one embodiment of the present invention.

FIG. 1 is a configuration explanatory diagram of a fluid feeding mechanism according to an embodiment of the present invention, FIG. 2 is a sectional view of a rotary joint used in a rotary seal mechanism of a fluid feeding mechanism according to an embodiment of the present invention, and FIG. 3 4 is a structural explanatory diagram of a housing member of a rotary joint according to an embodiment of the present invention, FIG. 4 is a structural explanatory diagram of a floating seat of a rotary joint according to an embodiment of the present invention, and FIG. 6 is a cross-sectional view showing the seal structure, FIG. 6 is a view showing a pressing spring, (A) is a front view, (B) is a partially enlarged side view, and FIGS. 7 and 8 are one embodiment of the present invention. FIG. 3 is an explanatory diagram of the operation of the rotary joint in FIG.

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

The rotating part 2a is fastened to the fastening hole 4a of the spindle shaft 4. The spindle shaft 4 is driven to rotate by a motor built into the spindle and rotates around the axis A within an insertion hole 5a provided in the 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 cylindrical block-shaped casing 3. The fixed part 2b is arranged coaxially with the rotating part 2a by detachably fastening the casing 3 to the frame 5 by a fastening means such as a bolt (not shown).

The fluid supply section 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). Here, the air supplied from the second fluid supply source 7b may be general factory air, dry air obtained by treating factory air with a dryer, or oil mist-containing air mixed with a predetermined amount of oil mist. Various forms can be selected depending on the target.

The fluid supplied from the fluid supply section 7 is selectively supplied by a fluid supply circuit 6 including 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, it is possible to turn on and off the supply of liquid coolant supplied from the first fluid supply source 7a to the fixed part 2b.

Further, 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 on-off valve 6b and a check valve 6c. By opening and closing the second on-off valve 6b, it is possible to turn on and off the supply of air supplied from the second fluid supply source 7b to the fixed part 2b. The check valve 6c is provided to prevent backflow of fluid from the coolant pipe 8a side to the air pipe 8b. Further, an air pipe 8c branched downstream of the second on-off valve 6b is connected to a pressurizing hole 20 (see FIG. 2) provided in the fixed part 2b. When the fluid to be supplied is air, the air piping 8c is adapted to supply air as a surface pressure adjusting fluid to the fixed portion 2b, as will be described later.

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 adjustment fluid can be fed to the fixed part 2b. Therefore, the fluid supply circuit 6 shown in FIG. 1 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 serves as a fluid supply means for feeding the surface pressure adjustment fluid to the pressurized opening 20 (see FIG. 2). The rotary joint 2 and the fluid supply circuit 6 constitute a rotary seal mechanism having 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 rotating around the axis via the fixed flow path 15d of the fixed part 2b.

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 is mainly composed of a rotor 10 having a rotation flow passage 10a that penetrates the shaft center in the axial direction and a fastening screw part 10b on the outer surface. The rotor 10 is screwed to the spindle shaft 4 by screwing the fastening screw part 10b into the fastening hole 4a, and the screw fastening part 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.

An annular convex portion 10c is formed on the right side end surface of the rotor 10 (the side facing the fixed portion 2b) so as to surround the aperture surface of the rotation flow path 10a. A first seal ring 11 is fixed to a recess formed inside the annular protrusion 10c. The first seal ring 11 is made of a hard material with high wear resistance, such as ceramic, and is formed into an annular shape having an opening 11a in the center. The first seal ring 11 is fixed to the annular convex portion 10c with the first seal surface 11b finished as a smooth surface facing outward. In this state, the rotating flow path 10a communicates with the opening 11a and opens to the first sealing surface 11b. That is, the rotor 10 to which the first seal ring 11 is fixed is a rotary seal portion having a first seal surface 11b provided on the rotary portion 2a and having a rotary flow path 10a opened at a side end surface.

Next, the structure of the fixed part 2b attached to the casing 3 will be described. The mounting surface 3c of the casing 3 has an attachment hole 3a that is connected to the flow passage hole 3b. The attachment hole 3a is fitted with an attachment protrusion 13b provided on a cylindrical housing member 13 that constitutes the main body of the fixed part 2b. As shown in FIG. 3, the housing member 13 is bolted to the casing 3 by screwing a plurality of evenly spaced bolts 14 into threaded holes 3d provided on the mounting surface 3c, and the fitting portion of the mounting protrusion 13b is sealed by an O-ring 16. A fitting hole 13a that penetrates in the axial direction is provided in the center of the housing member 13, and O-ring grooves 13c and 13d are provided on the inner peripheral surface of the fitting hole 13a.

In FIG. 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 where axial movement is permitted.

On the left side end surface of the flange portion 15a (the side facing the rotating portion 2a), a circular annular convex portion 15c is formed 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 molded into a circular 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 the outer surface. In this state, the fixed flow passage 15d communicates with the opening 17a and opens to the second seal surface 17b. In other words, 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 rotating flow passage 10a opening on the side end surface.

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 equal intervals corresponding to the positions of the bolts 14 shown in FIG. 3, and when the floating seat 15 is attached to the housing member 13, the housing member 13 can be bolted to the casing 3. In addition, 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. Note that 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 operating speed.

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

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 mounting the O-ring 21a. When the O-ring 21a is mounted in the O-ring groove 13c, it constitutes the first shaft seal portion 21.

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

The O-ring groove 13d is a groove for mounting the O-ring 22a. In addition to the O-ring 22a, the pressure spring 26 is mounted in the O-ring groove 13d. When the O-ring 22a and the pressure spring 26 are mounted in the O-ring groove 13d, they form the second shaft seal portion 22.

The O-ring groove 13d is formed so that when the O-ring 22a is attached, the outer periphery of the O-ring does not contact the groove bottom 13e, 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 when attached to the O-ring groove 13d, it makes full circumferential contact with the outer periphery of the large diameter portion 15f of the fixed shaft portion 15b. 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 Figure 5) of the O-ring groove 13d and the sliding surface of the fixed shaft portion 15b.

The pressing spring 26 of the O-ring 22a is used to press the O-ring 22a toward the low-pressure side of the O-ring groove 13d, that is, toward the rotor 10, thereby sealing the gap created on the low-pressure side and performing a sealing action. As shown in FIG. 6(a), the pressing spring 26 is formed by a spring material into a corrugated body portion 26a having approximately the same inner and outer diameters as the O-ring 22a and whose peripheral surface is corrugated in the axial direction. This is a ring-shaped wave washer. The number of wave periods is three or more.

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

Although the pressing spring 26 of this embodiment is manufactured using the resin PTFE (polytetrafluoroethylene (Teflon (registered trademark)) as a spring material, it may be made of other resin or elastomer. be able to.

Figure 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.

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 each seal the gap 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 inside the fitting hole 13a acts on the side end surface 15h with a pressure-receiving area of A1.

The housing member 13 is provided with a pressurized aperture 20 connected to the air pipe 8c shown in FIG. 1. The pressurized aperture 20 opens in the 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 as a surface pressure adjusting fluid into the annular gap 23. The pressure of the fluid in the annular gap 23 acts on the step portion 15g with a pressure receiving area A2.

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 rotating flow passage 10a that is rotating around 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 of the housing member 13, thereby guiding the axial movement of the floating seat 15 and preventing it from rotating around the axis.

When the rotary joint 2 is in operation, the sealing surface of the face seal portion 18 is brought into contact and separated by the advancing movement of the floating seat 15 due to the pressure of the supplied fluid and the movement of the spindle shaft 4 back and forth. That is, in a state where the floating sheet 15 is retreated and the first sealing surface 11b and the second sealing surface 17b are separated from each other, the fluid is fed into the fitting hole 13a through the channel hole 3b. As a result, the floating sheet 15 moves forward (in the direction of arrow a), and the first sealing surface 11b comes into contact with the second sealing surface 17b, forming a surface seal portion 18.

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 moving the spindle shaft 4 backward (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 state of contact 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 leakage the next time fluid is supplied. Note that if the pressing force of the pressing spring 26 exceeds 25N per peak, the O-ring 22a will be deformed due to excessive compression, causing a gap 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.

Next, with reference to FIGS. 7 and 8, the operation of the rotary joint 2 in the case of feeding a plurality of types of fluid will be described. FIGS. 7 and 8 show cases in which the fluids to be supplied are liquid coolant and air, respectively. First, a case where the supplied fluid is a liquid coolant will be described.

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 flow path 15d to the rotary flow path 10a. At this time, pressure P1 acts on the side end surface 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 surface 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.

Next, we will explain the case where the fluid supplied is air. 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 rotating flow path 10a via the fixed flow path 15d. At this time, pressure P2 acts on the side end surface 15h inside the fitting hole 13a, and a fluid force F (G1) commensurate with the pressure-receiving area A1 (see FIG. 4) acts on the fixed shaft portion 15b.

The air fed to the pressurized opening 20 acts on the step 15g within the annular gap 23, and a fluid force F (G2) corresponding to 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 aforementioned 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 aforementioned seal area is the seal face pressure value.

Here, we will explain the seal surface pressure in a rotary joint. 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 shown in this embodiment, when the target is liquid coolant, which is often supplied at a relatively high supply pressure (e.g., 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.

On the other hand, when targeting air used at low supply pressures (for example, 0.1Mpa to 1Mpa), the seal surface pressure should be less than half of the supply pressure to prevent wear and tear on the seal surface due to sliding. That is required. When supplying liquid, the thin film of liquid that enters the seal surface acts as a lubricating film that lubricates the sliding surface, whereas when supplying air, oil mist is mixed in to lubricate the sliding surface. This is generally due to the absence of such lubrication, unless countermeasures are taken.

In this way, when fluids with different supply pressures and desired seal surface pressure values are to be supplied, it is necessary to change the ratio of the seal surface pressure value to the supply pressure depending on the fluid. Here, since the seal area of the face seal part is the same for all fluids, in order to change the ratio of the seal face pressure value to the supply pressure, the pressure receiving area on which the fluid pressure acts must be changed depending on the type of fluid. It needs to be different. In the present embodiment, as shown in FIG. 8, when the target is air for which a low seal surface pressure value is required, the substantial pressure receiving area that generates the pressing force acting on the surface seal portion 18 is (A1- A2), which is different from the pressure receiving area A1 in the case of liquid coolant.

In the case shown in FIG. 8, air is fed into the annular gap 23 as a surface pressure adjusting fluid 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) to the floating sheet 15, which is the fixed seal portion, in the opposite direction to the pressing force F (G1) due to the fluid pressure acting on the side end surface 15h, thereby reducing the sealing surface pressure of the face seal portion 18.

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

In the rotary joint 2 shown in this embodiment, when the supply of surface pressure adjustment air is stopped, the O-ring 22a pressed against the low-pressure side wall 13g of the O-ring groove 13d by the pressing spring 26 is moved by the pressing spring 26. The remaining pressure of the surface pressure adjusting air, which is higher than the pressing force of the pressing spring 26, is pushed back by a force in the opposite direction to the pressing force of the pressing spring 26, and the pressure is released. Therefore, it is possible to prevent the internal pressure from remaining applied when the supply of surface pressure adjustment air is stopped, and the surface seal portion 18 operates due to the residual pressure of the first shaft seal portion 21 and the second shaft seal portion 22. Defects can be resolved.

The rotary seal mechanism and rotary joint in the fluid feeding mechanism of the present invention have the feature that surface pressure can be adjusted rationally, and are used to feed liquid coolant and air to rotating parts such as the main shaft of a machine tool. Useful for applications.

1 Fluid supply mechanism 2 Rotary joint 2a Rotating part 2b Fixed part 4 Spindle shaft 6 Fluid supply circuit 7 Fluid supply part 7a First fluid supply source 7b Second fluid supply source 10 Rotor 10a Rotating flow path 11 First seal Ring 11b First sealing surface 13 Housing member 13a Fitting hole 13d O-ring groove 13e Groove bottom 13g Low pressure side wall 15 Floating seat 15a Flange portion 15b Fixed shaft portion 15d Fixed flow path 15e Small diameter portion 15f Large diameter portion 15g Step portion 16 O-ring 17 Second seal ring 17b Second seal surface 18 Face seal part 20 Pressure opening 21 First shaft seal part 21a O-ring 22 Second shaft seal part 22a O-ring 23 Annular gap 26 For pressing spring

Claims (2)

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 fluids, 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 corrugated in the axial direction, 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. 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 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 corrugated in the axial direction, 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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