Rotary joint device, motor, and machine tool

Abstract

To provide a rotary joint device which can achieve both smooth reciprocating movement of a fixed side joint and simplification of a structure.SOLUTION: A rotary joint device includes: a cylindrical rotation side joint that is rotatable in a circumferential direction and has a first hole through which a liquid circulates; a fixed side joint which has an end face of one end facing one end face of the rotation side joint and has a cylindrical shape capable of reciprocating in an approaching / separating direction to / from the rotation side joint, and has a second hole communicating with the first hole when being brought into contact with the rotary side joint; an attachment that has a third hole through which the liquid is circulated, has the other end of the fixed side joint inserted into the third hole, and is used while being fixed to other member; a DLC film provided on the outer peripheral surface of the fixed side joint; and an elastic member which is airtightly interposed between the inner peripheral surface of the third hole and the DLC film, and is relatively slid to the DLC film when being moved in the approaching / separating direction of the fixed side joint, wherein the DLC film is provided in a contact range with which the elastic member is brought into contact, on the outer peripheral surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a rotary joint device, a motor, and a machine tool. [Background technology]

[0002] Conventionally, for example, machine tools have been equipped with rotary joint devices. When the rotary joint device includes a cylindrical rotating joint and a fixed joint, an end face of one end of the rotating joint and an end face of one end of the fixed joint face each other. The other end of the rotating joint is connected to a cylindrical rotating shaft of, for example, a motor. The attachment included in the rotary joint device is fixed to a stationary member included in the machine tool. The attachment has a through hole. The other end of the fixed joint is inserted into the through hole of the attachment. Coolant (liquid) is pumped by a pump of a coolant supply device installed outside the machine tool and flows through the through hole of the attachment. An elastic member is interposed between the inner peripheral surface of the through hole of the attachment and the outer peripheral surface of the fixed joint in a watertight manner (to prevent liquid leakage). The motor's rotating shaft rotates in the circumferential direction. The rotation of the rotating shaft is transmitted to the tool, which processes the workpiece. The tool has a nozzle.

[0003] The coolant flowing through the through-hole of the attachment presses against the fixed joint, causing it to come into contact with the rotating joint. The coolant flows through the through-hole of the attachment, the through-hole of the fixed joint, the through-hole of the rotating joint, and the through-hole of the rotating shaft in that order, and is sprayed toward the workpiece from a spray nozzle on the tool. When the supply of coolant to the through-hole of the attachment is stopped while the motor is rotating, the rotation of the rotating joint generates wind pressure that pushes against the fixed joint, or the biasing member of the rotary joint device pushes against the fixed joint, causing the fixed joint to move away from the rotating joint. For example, Patent Document 1 refers to this type of rotary joint device (referred to as "rotary joint" in the text).

[0004] The fixed joint moves back and forth in a direction toward and away from the rotating joint. The reciprocating movement of the fixed joint causes the elastic member to slide relative to the outer circumferential surface of the fixed joint. The rotary joint device described in Patent Document 1 has a supply hole formed between the outer circumferential surface of the fixed joint (hereinafter referred to as the "fixed shaft") and the elastic member (hereinafter referred to as the "O-ring") for supplying grease. The presence of grease ensures smooth reciprocating movement of the fixed joint. If the fixed joint does not come into contact with the rotating joint smoothly, there is a risk of coolant leaking between the fixed joint and the rotating joint. If the fixed joint does not separate from the rotating joint smoothly, there is a risk of unnecessary wear between the fixed joint and the rotating joint. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-218293 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the configuration of the rotary joint device described in Patent Document 1 is complicated since it requires a grease supply hole.

[0007] An object of the present disclosure is to provide a rotary joint device, a motor, and a machine tool that can achieve both smooth reciprocating movement of a fixed side joint and a simplified configuration. [Means for solving the problem]

[0008] a fixed-side joint having a second hole in the axial direction that communicates with the first hole when in contact with the rotating-side joint; a third hole through which the liquid flows, the second hole having a third hole through which the liquid flows, the second hole being in the axial direction and communicating with the first hole when the fixed-side joint is in contact with the rotating-side joint; an attachment having a third hole through which the liquid flows, the second hole being in contact with the third hole, the third hole being a third hole through which the liquid flows, the attachment being inserted into the third hole and being fixed to another member; a DLC (diamond-like carbon) film provided on the outer peripheral surface of the fixed-side joint; and an elastic member watertightly interposed between the inner peripheral surface of the third hole and the DLC film, the elastic member sliding relative to the DLC film when the fixed-side joint moves in the contact direction, the DLC film being provided in a contact area of ​​the outer peripheral surface where the elastic member comes into contact.

[0009] In the present disclosure, the rotary joint and the fixed joint each have a cylindrical shape. The rotating-side joint is rotatable in a circumferential direction. The fixed-side joint is reciprocatingly movable in a direction toward and away from the rotating-side joint. An end face of one end of the fixed-side joint faces one end face of the rotating-side joint. The fixed-side joint has a second hole in the axial direction.

[0010] The attachment is fixed to another member for use. The attachment has a third hole. Liquid flows through the third hole. The other end of the fixed-side joint is inserted into the third hole, so that the third hole and the second hole of the fixed-side joint are in communication. A DLC film is provided on the outer peripheral surface of the fixed joint. An elastic member is watertightly interposed between the DLC film and the inner peripheral surface of the attachment's third hole. The elastic member slides relative to the DLC film when the fixed joint moves in the direction of approach or separation. Hereinafter, the relative sliding of the elastic member with respect to the DLC film will simply be referred to as the sliding of the elastic member.

[0011] The DLC film is provided in the contact area. This contact area is the area on the outer circumferential surface of the fixed joint where the elastic member comes into contact. The low friction of the DLC film against the elastic member allows the elastic member to slide smoothly. This allows the fixed joint to move smoothly toward and away from the rotating joint. The DLC film can be formed on the outer peripheral surface of the fixed joint using well-known DLC coating techniques, so there is no need to form a supply hole in the attachment for supplying grease, for example, and the structure of the rotary joint device is therefore simple. As a result of the above, smooth reciprocating movement of the fixed joint and a simplified configuration can both be achieved.

[0012] The rotating joint has a first hole in the axial direction. A fluid flows through the first hole. When the fixed joint is in contact with the rotating joint, the second hole of the fixed joint communicates with the first hole of the rotating joint. The liquid flows, for example, through the third hole of the attachment, the second hole of the fixed joint, and the first hole of the rotating joint in this order. Because the frictional force generated between the DLC film and the elastic member is small, the rotary joint device can be designed to increase the force with which the elastic member contacts the DLC film, thereby reliably preventing liquid leakage between the inner circumferential surface of the third hole in the attachment and the outer circumferential surface of the fixed joint.

[0013] The rotary joint device according to the present disclosure is characterized in that the DLC film is provided in the contact area and a non-contact area on the outer circumferential surface where the elastic member does not come into contact, and the non-contact area is located closer to the end face of the other end than the contact area.

[0014] In the present disclosure, the DLC film is provided in the contact area and the non-contact area. The non-contact area is an area on the outer circumferential surface of the fixed joint that does not come into contact with the elastic member, and is located closer to the end face of the other end of the fixed joint than the contact area. Some of the liquid flowing through the third hole of the attachment penetrates between the DLC film provided in the non-contact area and the inner surface of the third hole of the attachment. If foreign matter is mixed in the liquid, there is a risk that the foreign matter will penetrate between the inner surface of the third hole of the attachment and the DLC film. However, due to the low friction of the DLC film against foreign matter, there is no risk that the foreign matter will hinder the movement of the fixed joint in the contact / separation direction.

[0015] Even in the area on the outer peripheral surface of the fixed joint where the elastic member does not come into contact, there is no need to provide a DLC film in the area that is located closer to the end face of one end of the fixed joint than the contact area, because even if a DLC film is provided in this area, there is no risk of liquid (and therefore foreign matter mixed in the liquid) penetrating between the DLC film provided in this area and the inner peripheral surface of the third hole of the attachment.

[0016] The rotary joint device according to the present disclosure is characterized in that the elastic member is an O-ring made of fluororubber.

[0017] In the present disclosure, the elastic member is an O-ring made of fluororubber. The coefficient of friction between the O-ring made of fluororubber and the DLC film is sufficiently small, allowing the elastic member to slide more smoothly.

[0018] The motor according to the present disclosure includes a cylindrical rotating shaft that is rotatable in a circumferential direction and has a flow hole in an axial length direction through which a liquid flows, the rotating shaft including a cylindrical rotating-side joint that is rotatable in a circumferential direction and has a first hole in an axial length direction through which the liquid flows, a fixed-side joint that has an end face of one end thereof facing one end face of the rotating-side joint and is cylindrical and that is movable back and forth in a direction toward and away from the rotating-side joint, and has a second hole in an axial length direction that communicates with the first hole when the fixed-side joint is in contact with the rotating-side joint, a third hole through which the liquid flows, and the other end of the fixed-side joint is inserted into the third hole, and the fixed-side joint is movable back and forth in a direction toward and away from the rotating-side joint, and the fixed-side joint has ... in an axial length direction through which the liquid flows, and the fixed-side joint has a third hole in an axial length direction through which the liquid flows, and the fixed-side joint has a third hole in which the liquid flows, and the fixed-side joint has a third hole in which the liquid flows, and the fixed-side joint has a third hole in which the liquid flows, and the fixed-side joint has a third hole in which the liquid flows. the attachment is fixed to a material, a DLC (diamond-like carbon) film is provided on the outer peripheral surface of the fixed joint, and an elastic member is interposed watertightly between the inner peripheral surface of the third hole and the DLC film and slides relative to the DLC film when the fixed joint moves in the direction of approaching or separating, the DLC film rotates integrally with the rotating joint of the rotary joint device provided in a contact range on the outer peripheral surface where the elastic member comes into contact, and is connected to the other end of the rotating joint so that the flow hole and the first hole are in communication.

[0019] In the present disclosure, the rotary joint of the rotary joint device according to the present disclosure is connected to the rotary shaft, which allows for smooth reciprocation of the fixed joint while simplifying the configuration. The rotating shaft is cylindrical and rotatable in the circumferential direction. The rotating shaft has a flow hole in the axial direction. A fluid flows through the flow hole. The rotating shaft is connected to the other end of the rotating-side joint so that the rotating shaft and the rotating-side joint rotate integrally and the flow hole of the rotating shaft communicates with a first hole of the rotating-side joint.

[0020] The machine tool according to the present disclosure is a machine tool capable of machining a workpiece while using a tool having an outlet to discharge coolant from the outlet, the machine tool comprising: a cylindrical rotating joint that is rotatable in a circumferential direction and has a first hole in an axial direction through which liquid flows; a fixed joint having a cylindrical shape with one end surface facing one end surface of the rotating joint and capable of reciprocating in a direction of approaching and separating from the rotating joint, and having a second hole in an axial direction that communicates with the first hole when in contact with the rotating joint; an attachment having a third hole through which the liquid flows, and having the other end of the fixed joint inserted into the third hole; a DLC (diamond-like carbon) film provided on the outer peripheral surface of the fixed joint; and a watertight seal between the inner peripheral surface of the third hole and the DLC film. the rotary joint device includes a rotary joint device having an elastic member that slides relative to the DLC film when the fixed joint moves in the approaching or separating direction, a fixed member to which the attachment is fixed, and a motor including a rotary shaft that is rotatable in a circumferential direction and has a fourth hole through which the liquid flows, the rotary shaft rotates integrally with the rotary joint and is connected to the other end of the rotary joint so that the fourth hole and the first hole are in communication, the rotation of the rotary shaft is transmitted to the tool to rotate the tool, the liquid flows through the third hole, the second hole, the first hole, and the fourth hole in this order, and is sprayed out through the spray port, and the DLC film is provided in a contact area on the outer circumferential surface where the elastic member comes into contact.

[0021] In the present disclosure, an attachment of a rotary coupling device according to the present disclosure is fixed to a stationary member of a machine tool, and a rotating-side coupling of the rotary coupling device according to the present disclosure is connected to a rotating shaft of a motor of the machine tool, thereby achieving both smooth reciprocating movement of the stationary-side coupling and a simplified configuration. The rotating shaft is cylindrical and rotatable in a circumferential direction. The rotating shaft has a fourth hole in the axial direction. A fluid flows through the fourth hole. The rotating shaft is connected to the other end of the rotating-side joint so that the rotating shaft and the rotating-side joint rotate integrally and the fourth hole of the rotating shaft communicates with the first hole of the rotating-side joint.

[0022] The rotation of the rotary shaft is transmitted to the tool, which then rotates. The tool processes the workpiece. The rear part has a nozzle. When the fixed joint is in contact with the rotating joint, the second hole of the fixed joint is connected to the first hole of the rotating joint. The liquid flows through the third hole of the attachment, the second hole of the fixed joint, the first hole of the rotating joint, and the fourth hole of the rotating shaft in that order, and is sprayed out through the nozzle of the tool. The machine tool can machine the workpiece while spraying coolant from the nozzle of the tool. [Effects of the Invention]

[0023] According to the rotary joint device, motor, and machine tool of the present disclosure, smooth reciprocating movement of the fixed side joint and a simplified configuration can both be achieved. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view of a machine tool according to an embodiment; [Figure 2] FIG. 2 is a schematic cross-sectional view of a main part of a spindle head. [Figure 3] FIG. 2 is a schematic enlarged cross-sectional view of a main part of a spindle head. [Figure 4] FIG. 2 is a cross-sectional view of a rotary joint device. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present disclosure will be described below. In the following description, up / down, front / rear, and left / right directions are indicated by arrows in the drawings. As will be described later, in this embodiment, the upper side is the coolant (liquid) inlet side, and the lower side is the coolant outlet side.

[0026] 1 is a perspective view of a machine tool according to an embodiment. Hereinafter, the left-right direction, front-rear direction, and up-down direction of machine tool 1 are the X-axis direction, Y-axis direction, and Z-axis direction, respectively. The machine tool 1 comprises a base 11, a column 12, and a spindle head 13. The base 11 is a roughly rectangular parallelepiped iron base that is installed on the floor. The column 12 is provided at the rear of the upper part of the base 11. The spindle head 13 is provided in front of the column 12 so as to be movable in the vertical direction. The column 12 is equipped with a Z-direction motor (not shown) for moving the spindle head 13 in the Z direction.

[0027] 2 is a schematic cross-sectional view of a main part of the spindle head 13. The spindle head 13 is equipped with a motor 21. The motor 21 is equipped with a rotary shaft 22 and a rotor and a stator (not shown). The rotating shaft 22 is cylindrical. The rotating shaft 22 can rotate in the circumferential direction. The axial length direction of the rotating shaft 22 faces up and down. Because the rotating shaft 22 is cylindrical, it has a through hole coaxially in the axial length direction. This through hole is the fourth hole 220 (flow hole). When power is supplied to the motor 21 from the power source in the control box 17, the rotating shaft 22 rotates in the circumferential direction.

[0028] The spindle head 13 further includes a fixed member 23 and a spindle 24. The fixed member 23 is, for example, cylindrical and has a bottom. The cylindrical fixed member 23 is arranged coaxially with the rotating shaft 22. The fixed member 23 is positioned above the motor 21 with the opening of the fixed member 23 facing downward. The fixed member 23 has a supply port 231. The supply port 231 is located on the peripheral wall of the fixed member 23, for example.

[0029] The main shaft 24 is located below the motor 21 and below the main shaft head 13. The axial length direction of the main shaft 24 faces up and down. The main shaft 24 has a through hole 240 coaxially therewith. The upper end of the main shaft 24 is coaxially and watertightly connected to the lower end of the rotating shaft 22 of the motor 21. For example, a coupling 25 connects the rotating shaft 22 and the main shaft 24 to each other. By connecting the rotating shaft 22 and the main shaft 24, the fourth hole 220 of the rotating shaft 22 and the through hole 240 of the main shaft 24 communicate with each other, and the main shaft 24 rotates in the circumferential direction as the rotating shaft 22 rotates.

[0030] In the figure, reference numeral 20 denotes a tool, which is, for example, an end mill for performing cutting processing on a workpiece W. The tool 20 is columnar. The tool 20 has a passage 201. The passage 201 extends from one end of the tool 20 to the other end. The axial length direction of the tool 20 faces up and down. The lower end of the main shaft 24 detachably and watertightly holds the upper end of the tool 20. As the main shaft 24 holds the tool 20, the through hole 240 of the main shaft 24 and the passage 201 of the tool 20 communicate with each other, and the tool 20 rotates in the circumferential direction as the main shaft 24 rotates. The tool 20 has at least one ejection port 202. The ejection port 202 is located at the lower end of the tool 20 and communicates with the passage 201.

[0031] As shown in FIG. 1, the machine tool 1 includes a tool changer 14 , a frame 15 , a table 16 , and a control box 17 . The tool changer 14 is equipped with a disk-shaped magazine 141. A pair of left and right frames 15 hold the magazine 141 on the front side of the column 12 so as not to interfere with the spindle head 13. The magazine 141 is equipped with a plurality of grip arms 142 arranged radially around its outer periphery. The grip arms 142 detachably hold tools 20 via tool holders (not shown). The tool changer 14 rotates the magazine 141 and positions a predetermined tool 20 at the tool change position. The tool changer 14 exchanges the tool 20 attached to the spindle 24 with the tool 20 at the tool change position. The tool change position is the lowest position of the magazine 141.

[0032] The table 16 is provided on the upper part of the base 11, in front of the column 12 and below the magazine 141. A user fixes a workpiece W to the table 16. The base 11 supports the table 16 so that it can move in both the X-axis and Y-axis directions. The table 16 moves in the X-axis and Y-axis directions by driving an X-axis motor and a Y-axis motor (not shown). The base 11 supports a control box 17 so as to be positioned on the rear side of the column 12. A control unit (not shown) provided in the control box 17 controls the operation of the machine tool 1.

[0033] The table 16 moves back and forth and left and right to adjust the front-rear and left-right position of the tool 20 held by the spindle 24. The spindle head 13 moves up and down to adjust the up and down position of the tool 20 held by the spindle 24. Machine tool 1 uses a rotating tool 20 to machine workpiece W. Tool 20 cuts workpiece W by coming into contact with workpiece W while rotating. When machining workpiece W, a coolant supply device (not shown) supplies coolant to the internal space of fixed member 23 through supply port 231, thereby increasing the lubrication between tool 20 and workpiece W and enabling efficient removal of chips.

[0034] The machine tool 1 further includes a rotary joint device 3 (see FIG. 2). FIG. 3 is a schematic enlarged cross-sectional view of a main part of the spindle head 13, mainly showing the rotary joint device 3. FIG. 4 is a cross-sectional view of the rotary joint device 3. As shown in FIGS. 2 to 4, the rotary joint device 3 includes an attachment 31, a fixed-side joint 32, and a rotary-side joint 33. The attachment 31 is cylindrical. Because the attachment 31 is cylindrical, it has a through hole coaxially extending in the axial direction. This through hole is the third hole 310. The attachment 31 has a flange 311 on the outer peripheral surface of one end. The attachment 31 is fixed to the fixing member 23.

[0035] For example, the attachment 31 has an axial length direction facing up and down, and has a flange 311 at its lower end. The attachment 31 is inserted into the fixed member 23 from below through an opening in the fixed member 23 in a watertight manner (see Figures 3 and 4). The flange 311 of the attachment 31 is in contact with the lower end surface of the fixed member 23. When the attachment 31 is inserted into the fixed member 23, the third hole 310 of the attachment 31 communicates with the supply port 231 through the internal space of the fixed member 23. The attachment 31 is positioned below the supply port 231 of the fixed member 23, and does not block the supply port 231.

[0036] 3 and 4, the attachment 31 has a groove 312 on its outer peripheral surface. The groove 312 is continuous in the circumferential direction of the attachment 31. An O-ring 261 is housed in the groove 312. As shown in FIG. 3, the O-ring 261 is interposed over the entire circumference between the outer peripheral surface of the attachment 31 and the inner peripheral surface of the fixing member 23. This prevents liquid from leaking between the attachment 31 and the fixing member 23.

[0037] As shown in Figures 2 to 4, the fixed-side joint 32 and the rotating-side joint 33 are each cylindrical. The inner and outer diameters of the fixed-side joint 32 and the rotating-side joint 33 are approximately the same. The fixed-side joint 32 and the rotating-side joint 33 are each made of an iron-based material, such as stainless steel or chrome-molybdenum steel, or an aluminum-based metal. The axial length direction of the fixed-side joint 32 and the rotating-side joint 33 is vertical. The fixed-side joint 32 and the rotating-side joint 33 are arranged coaxially in this order from top to bottom. The fixed-side joint 32 can reciprocate vertically relative to the attachment 31 but does not rotate circumferentially (it is fixed). The rotating-side joint 33 can rotate circumferentially but does not move vertically relative to the attachment 31. Hereinafter, vertical movement relative to the attachment 31 will simply be referred to as vertical movement.

[0038] The rotating-side joint 33 is cylindrical and has a through-hole coaxially extending in the axial direction. This through-hole is the first hole 330. The rotating-side joint 33 is coaxially and watertightly connected to the upper end of the rotating shaft 22 of the motor 21. The connection between the rotating shaft 22 and the rotating-side joint 33 allows the fourth hole 220 of the rotating shaft 22 and the first hole 330 of the rotating-side joint 33 to communicate with each other, and the rotating-side joint 33 rotates in the circumferential direction as the rotating shaft 22 rotates.

[0039] For example, the rotating side joint 33 is inserted watertightly into the rotating shaft 22 from above through an opening on the upper end side of the rotating shaft 22, with the upper end of the rotating side joint 33 protruding upward from the rotating shaft 22. The rotating side joint 33 has a flange 331 on its outer circumferential surface (see FIGS. 3 and 4). The flange 331 contacts the upper end surface of the rotating shaft 22 from above. The flange 331 is fastened to the rotating shaft 22 with a screw (not shown), allowing the rotating side joint 33 to follow the rotation of the rotating shaft 22.

[0040] 3 and 4, the rotating side joint 33 has a groove 332 on its outer peripheral surface. The groove 332 is continuous in the circumferential direction of the rotating side joint 33. An O-ring 262 is housed in the groove 332. As shown in FIG. 3, the O-ring 262 is interposed over the entire circumference between the outer peripheral surface of the rotating side joint 33 and the inner peripheral surface of the rotating shaft 22. This prevents liquid from leaking between the rotating side joint 33 and the rotating shaft 22.

[0041] The fixed-side joint 32 is cylindrical and has a through-hole coaxially extending in the axial direction. This through-hole is the second hole 320. As shown in FIGS. 2 to 4, at least the upper end of the fixed-side joint 32 is inserted into the third hole 310 of the attachment 31 from below so that the fixed-side joint 32 is coaxial with the attachment 31. The lower surface of the fixed-side joint 32 faces the upper surface of the rotating-side joint 33.

[0042] As shown in Figure 3, a DLC film 35 is provided on the outer peripheral surface of the upper end of the fixed joint 32. The area where the DLC film 35 is provided will be described later. The DLC film 35 is a coating made of diamond-like carbon and is only a few microns thick, which is very thin compared to the thickness of the peripheral wall of the fixed joint 32. However, for ease of viewing the figure, the DLC film 35 shown in Figure 3 is thick. In order to obtain low friction characteristics with the elastic member 36, it is desirable that the hydrogen content of the DLC film 35 be 40 to 70 at.%.

[0043] 3 and 4, the third hole 310 of the attachment 31 has a groove 34 on its inner circumferential surface. The groove 34 is continuous in the circumferential direction of the attachment 31. An elastic member 36 is housed in the groove 34. The elastic member 36 is an O-ring made of fluororubber (preferably vinylidene fluoride rubber (FKM)). The elastic member 36 has a circular cross section. The elastic member 36 is interposed watertightly around the entire circumference between the inner surface of the third hole 310 of the attachment 31 and the DLC film 35 so that the DLC film 35 can slide up and down relative to the elastic member 36.

[0044] The coolant that flows into the internal space of the fixed member 23 through the supply port 231 shown in FIG. 2 flows from the internal space of the fixed member 23 into the third hole 310 of the attachment 31. The fixed-side joint 32 moves downward due to the hydraulic pressure of the coolant that has flowed into the third hole 310 of the attachment 31. When the fixed-side joint 32, which is separated from the rotating-side joint 33, moves downward, the lower surface of the fixed-side joint 32 approaches the upper surface of the rotating-side joint 33. The lower surface of the fixed-side joint 32 comes into contact with the upper surface of the rotating-side joint 33 from above, preventing the fixed-side joint 32, which has moved downward, from falling off the attachment 31.

[0045] For example, the hydraulic pressure of the coolant supplied from a coolant supply device (not shown) is 7 MPa, and the coolant presses the lower surface of the fixed-side joint 32 against the upper surface of the rotating-side joint 33. At this time, the lower surface of the fixed-side joint 32 and the upper surface of the rotating-side joint 33 are in close contact with each other, preventing liquid from leaking between the lower surface of the fixed-side joint 32 and the upper surface of the rotating-side joint 33.

[0046] When the lower surface of the fixed-side joint 32 is in contact with the upper surface of the rotating-side joint 33, the second hole 320 of the fixed-side joint 32 communicates with the first hole 330 of the rotating-side joint 33. The coolant that flows into the third hole 310 of the attachment 31 flows from the third hole 310 of the attachment 31 through the second hole 320 of the fixed-side joint 32, the first hole 330 of the rotating-side joint 33, the fourth hole 220 of the rotating shaft 22 of the motor 21, and the through-hole 240 of the main shaft 24, in this order. The coolant that flows through the through-hole 240 of the main shaft 24 flows into the flow path 201 of the tool 20. The coolant that flows into the flow path 201 of the tool 20 is sprayed outward through the spray port 202. When the workpiece W is machined, the coolant reduces friction between the tool 20 and the workpiece W and washes away chips generated during machining of the workpiece W from the workpiece W.

[0047] If the supply of coolant is stopped while the motor 21 is rotating, wind pressure generated by the rotation of the rotating-side joint 33 will push the fixed-side joint 32 upward, causing the fixed-side joint 32 to move upward. Note that the rotary joint device 3 may be provided with a biasing member that biases the fixed-side joint 32 upward. The force with which the biasing member biases the fixed-side joint 32 upward is smaller than the force with which the coolant presses the fixed-side joint 32 downward. When the fixed-side joint 32, which is in contact with the rotating-side joint 33, moves upward, the lower surface of the fixed-side joint 32 moves away from the upper surface of the rotating-side joint 33, as shown in Figure 3. The distance by which the lower surface of the fixed-side joint 32 moves away from the upper surface of the rotating-side joint 33 is, for example, about several mm, but is exaggerated in Figure 3 for ease of viewing.

[0048] 4, the fixed-side joint 32 has a guided portion 322. The guided portion 322 is, for example, a notch provided on the outer edge of a flange portion of the fixed-side joint 32. A cylindrical guide 313 passes through the guided portion 322. The guide 313 is screwed to the attachment 31 so that its axial direction faces up and down and hangs down from the underside of the flange 311 of the attachment 31. The inner surface of the guided portion 322 comes into contact with the outer peripheral surface of the guide 313, so that the guide 313 also functions as a stopper that prevents circumferential rotation of the fixed-side joint 32. Therefore, even when the lower surface of the fixed-side joint 32 comes into contact with the upper surface of the rotating-side joint 33, the fixed-side joint 32 can be prevented from rotating in conjunction with the rotation of the rotating-side joint 33.

[0049] During rotation of the rotating joint 33 , the upper surface of the rotating joint 33 slides against the lower surface of the fixed joint 32 in the circumferential direction. In order to reduce friction and wear during sliding, sliding auxiliary members 321, 333 may be provided on the periphery of the opening in the lower surface of the fixed joint 32 and the periphery of the opening in the upper surface of the rotating joint 33. Each of the slide assist members 321, 333 has an annular shape that is flat in the axial direction, and is coaxial with the fixed-side joint 32 and the rotating-side joint 33. Contact between the lower surface of the fixed-side joint 32 and the upper surface of the rotating-side joint 33 means contact between the slide assist member 321 and the slide assist member 333. Each of the slide assist members 321, 333 is wear-resistant and is made of, for example, silicon carbide.

[0050] The reciprocating movement of the fixed-side joint 32 in the vertical direction causes the elastic member 36 to slide vertically relative to the DLC film 35. Hereinafter, the relative vertical sliding movement of the elastic member 36 with respect to the DLC film 35 will be simply referred to as the sliding movement of the elastic member 36. Here, the range in which the DLC film 35 is provided will be described. As shown in FIG. 3, the DLC film 35 is provided in the contact area 3a and the non-contact area 3b. The contact range 3a is the range on the outer circumferential surface of the fixed-side joint 32 that comes into contact with the elastic member 36. The low friction of the DLC film 35 against the elastic member 36 allows the elastic member 36 to slide smoothly. This allows the fixed-side joint 32 to move smoothly in the vertical direction relative to the rotating-side joint 33. The contact range 3a is located midway in the axial length direction of the fixed-side joint 32.

[0051] The non-contact area 3b is an area on the outer peripheral surface of the fixed-side joint 32 that does not come into contact with the elastic member 36. The non-contact area 3b is continuous with the contact area 3a, and extends from the upper end of the contact area 3a to the upper end of the fixed-side joint 32. Note that the non-contact area 3b only needs to be above the contact area 3a, and does not have to be provided up to the upper end of the fixed-side joint 32. When the outer edge of the upper surface of the fixed-side joint 32 is chamfered as shown in FIG. 4, a DLC film 35 may or may not be provided on the chamfered portion of the fixed-side joint 32.

[0052] To allow the fixed joint 32 to move smoothly in the vertical direction, a gap exists between the inner surface of the third hole 310 of the attachment 31 and the DLC film 35. This gap is exaggerated in FIG. 3 . Some of the coolant that flows into the third hole 310 of the attachment 31 penetrates into the gap between the inner surface of the third hole 310 of the attachment 31 and the DLC film 35 in the non-contact area 3b. Although the gap between the inner surface of the third hole 310 of the attachment 31 and the DLC film 35 is narrow, if fine foreign matter is mixed in the coolant, the foreign matter may enter between the inner surface of the third hole 310 of the attachment 31 and the DLC film 35. However, due to the low friction of the DLC film 35 against foreign matter, there is no risk that the foreign matter will impede the vertical movement of the fixed joint 32.

[0053] The DLC film 35 can be provided on the outer peripheral surface of the fixed joint 32 by well-known DLC coating technology, so there is no need to form a supply hole in the attachment 31 for supplying grease between the outer peripheral surface of the fixed joint 32 and the elastic member 36. Therefore, the configuration of the rotary joint device 3 is simple. As a result of the above, smooth reciprocating movement of the fixed side joint 32 and a simplified configuration can both be achieved. Moreover, the DLC film 35 is highly resistant to coolant and wear, and is therefore maintenance-free.

[0054] Because the frictional force generated between the DLC film 35 and the elastic member 36 is small, the rotary joint device 3 can be designed so that the force with which the elastic member 36 contacts the DLC film 35 is large. Because the elastic member 36 is an O-ring, the compressibility of the elastic member 36 can be increased so that the force with which the elastic member 36 contacts the DLC film 35 is large. Therefore, liquid leakage from between the inner circumferential surface of the third hole 310 of the attachment 31 and the outer circumferential surface of the fixed-side joint 32 can be reliably prevented. It is desirable that the crushing rate of the elastic member 36 is 10 to 30%. When the wire diameter of the elastic member 36 is 1.9 mm, the inner diameter of the third hole 310 of the attachment 31 is 12 mm, and the outer diameter of the fixed side joint 32 is 9 mm, the crushing rate is approximately 21% (= {1.9 - (12 - 9) / 2} ÷ 1.9 × 100).

[0055] On the outer peripheral surface of the fixed-side joint 32, it is not necessary to provide the DLC film 35 in the range from the lower end of the contact area 3a to the lower end of the fixed-side joint 32. This is because even if the DLC film 35 is provided in this range, there is no risk of coolant (and thus foreign matter mixed in the coolant) penetrating into the gap between the DLC film 35 and the inner peripheral surface of the third hole 310 of the attachment 31 provided in this range. It is desirable that the surface roughness (arithmetic mean roughness Ra) of at least the contact area 3a and non-contact area 3b on the outer peripheral surface of the fixed joint 32 be 0.2 or less. If the arithmetic mean roughness exceeds 0.2, the low friction properties of the DLC film 35 may be insufficient due to the influence of the surface roughness of the contact area 3a and non-contact area 3b.

[0056] Now, let us consider providing a diamond coating on the outer peripheral surface of the fixed joint 32 instead of the DLC coating 35. The diamond coating has even better wear resistance than the DLC coating 35.

[0057] However, the temperature during deposition of a CVD diamond coating using a hot filament method, which can also be applied to the outer peripheral surface of the joint shape, is generally higher than the temperature during deposition of the DLC film 35. The fixed joint 32 is prone to distortion when exposed to the high temperatures (approximately 600 to 700°C) during diamond coating deposition. On the other hand, the fixed joint 32 is less likely to distort when exposed to the low temperatures (below 200°C) during DLC ​​film 35 deposition. Furthermore, while controlling the thickness of a diamond coating is difficult, controlling the thickness of the DLC film 35 is easy. In other words, employing the DLC film 35 contributes to improving the precision of the rotary joint device 3. Furthermore, diamond coatings are more expensive than the DLC film 35. In other words, employing the DLC film 35 contributes to reducing the manufacturing costs of the rotary joint device 3.

[0058] Furthermore, if foreign matter mixed in the coolant does not enter the gap between the inner surface of the third hole 310 of the attachment 31 and the outer surface of the fixed side joint 32 and hinder the vertical movement of the fixed side joint 32, there is no need to provide a DLC film 35 in the non-contact area 3b. The elastic member 36 is not limited to an O-ring made of fluororubber, but may be any member that satisfies the requirements of having a small coefficient of friction with the DLC film 35, being resistant to erosion by coolant, and being usable as a packing.

[0059] The rotary joint device 3 is not limited to a configuration provided in the machine tool 1. The attachment 31 is not limited to a configuration fixed to the fixed member 23. The rotating-side joint 33 is not limited to a configuration connected to the rotating shaft 22 of the motor 21. The direction in which the fixed-side joint 32 and the rotating-side joint 33 face each other is not limited to the vertical direction. The reciprocating direction of the fixed-side joint 32 is not limited to the vertical direction.

[0060] The embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is intended to include not only the above-mentioned meaning but also the meaning equivalent to the claims and all modifications within the scope of the claims. Independent and dependent claims may be combined with each other in any and all combinations, regardless of the reference format. Furthermore, while the claims may be written in a format in which a claim references two or more other claims (multiple claim format), this is not a limitation. Multiple claims that reference at least one other multiple claim (multiple multiple claim format) may also be written. [Explanation of symbols]

[0061] 1 Machine tools 20 Tools 202 spout 21 Motor 22 Rotation axis 220 Fourth hole (flow hole) 23 Fixing members (other members) 3 Rotary joint device 31 Attachment 310 Third hole 32 Fixed side joint 320 Second hole 33 Rotating side joint 330 First hole 34 Groove 35 DLC membrane 36 Elastic member (O-ring) 3a Contact area 3b Non-contact range

Claims

1. a cylindrical rotary joint that is rotatable in a circumferential direction and has a first hole in an axial direction through which a liquid flows; a fixed-side joint having a cylindrical shape with one end surface facing one end surface of the rotating-side joint, reciprocating in a direction of approaching and separating from the rotating-side joint, and having a second hole in an axial direction that communicates with the first hole when the fixed-side joint is in contact with the rotating-side joint; an attachment having a third hole through which the liquid flows, the other end of the fixed joint being inserted into the third hole and being fixed to another member; a DLC (diamond-like carbon) film provided on the outer peripheral surface of the fixed joint; an elastic member that is interposed watertightly between an inner circumferential surface of the third hole and the DLC film, and that slides relative to the DLC film when the fixed-side joint moves in the contact and separation directions; Equipped with The rotary joint device is characterized in that the DLC film is provided on the outer circumferential surface in a contact area with the elastic member.

2. the DLC film is provided in the contact area and in a non-contact area of ​​the outer circumferential surface that is not in contact with the elastic member, 2. The rotary joint device according to claim 1, wherein the non-contact area is located closer to the end face of the other end than the contact area.

3. 3. The rotary joint device according to claim 1, wherein the elastic member is an O-ring made of fluororubber.

4. a cylindrical rotating shaft that is rotatable in a circumferential direction and has a flow hole in an axial direction through which a liquid flows, The rotation axis is a cylindrical rotating joint that is rotatable in the circumferential direction and has a first hole in the axial direction through which the liquid flows; a fixed joint that has an end face of one end facing one end face of the rotating joint, is cylindrical and can move back and forth in a direction toward and away from the rotating joint, and has a second hole in the axial direction that communicates with the first hole when in contact with the rotating joint; an attachment that has a third hole through which the liquid flows, into which the other end of the fixed joint is inserted and that is used by fixing it to another member; a DLC (diamond-like carbon) film provided on the outer peripheral surface of the fixed joint; and an elastic member that is watertightly interposed between the inner peripheral surface of the third hole and the DLC film and slides relative to the DLC film when the fixed joint moves in the direction toward and away from the rotating joint, the DLC film rotating integrally with the rotating joint of the rotary joint device and is provided in a contact range on the outer peripheral surface where the elastic member comes into contact; The flow hole and the first hole are connected to each other, a motor connected to the other end of the rotary joint;

5. A machine tool capable of machining a workpiece while discharging coolant from a tool having a coolant outlet, a cylindrical rotary joint that is rotatable in a circumferential direction and has a first hole in an axial direction through which a liquid flows; a fixed-side joint having a cylindrical shape with one end surface facing one end surface of the rotating-side joint, capable of reciprocating in a direction of approaching and separating from the rotating-side joint, and having a second hole in an axial direction that communicates with the first hole when the fixed-side joint is in contact with the rotating-side joint; an attachment having a third hole through which the liquid flows, and the other end of the fixed-side joint being inserted into the third hole; A DLC (diamond-like carbon) film provided on the outer peripheral surface of the fixed joint, and an elastic member that is interposed watertightly between an inner peripheral surface of the third hole and the DLC film, and that slides relative to the DLC film when the fixed joint moves in the contact and separation directions; a rotary joint device having a fixing member to which the attachment is fixed; a motor including a rotating shaft that is rotatable in a circumferential direction and has a fourth hole through which the liquid flows; and, Equipped with the rotating shaft rotates integrally with the rotating joint and is connected to the other end of the rotating joint such that the fourth hole and the first hole communicate with each other; The rotation of the rotation shaft is transmitted to the tool, causing the tool to rotate; the liquid flows through the third hole, the second hole, the first hole, and the fourth hole in this order, and is ejected through the ejection port; The machine tool is characterized in that the DLC film is provided in a contact area on the outer circumferential surface where the elastic member comes into contact.

Images