Workpiece ejection device and machine tool

Abstract

The spindle's functionality is improved while maintaining a compact design for the headstock, which also features a workpiece ejection function. [Solution] A workpiece discharge device in one embodiment comprises a pressing rod, which is coaxially arranged inside the spindle and operates in the axial direction to press the workpiece and discharge it from the spindle, and a cylinder, which is arranged inside the spindle and operates the pressing rod in the axial direction by the supply of fluid pressure. The pressing rod is formed with an internal passage through which coolant supplied from a coolant supply device flows, and is configured to supply coolant toward the workpiece held by the spindle.

Description

【Technical Field】 , , , 【0005】 , 【0001】 The present invention relates to a machine tool, and more particularly to a workpiece discharging device for discharging a workpiece held by the spindle of a machine tool. 【Background Art】 【0002】 Machine tools include turning centers that move tools relative to rotating workpieces, machining centers that move rotating tools relative to workpieces, and composite machine tools that combine these functions. A machine tool that functions as a machining center holds a workpiece by a chuck provided on a workpiece spindle, and machines the workpiece by moving the tool two-dimensionally or three-dimensionally while rotating the workpiece spindle. 【0003】 The machined workpiece is unloaded from the workpiece spindle and recovered. Some machine tools include a workpiece discharging device for discharging the workpiece from the workpiece spindle (see Patent Document 1). The machine tool of Patent Document 1 includes an air cylinder inside the spindle headstock. By operating the air cylinder to push out the workpiece from the inside of the spindle headstock, the workpiece can be discharged from the workpiece spindle. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2021-146468 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 By incorporating a fluid pressure cylinder such as an air cylinder in this way, it may be possible to compactly configure the spindle headstock having a workpiece discharging function. The inventor has arrived at the idea that by devising the structure of the fluid pressure cylinder incorporated in the spindle headstock while paying attention to this point, the functionality of the spindle can be improved. [[ID=4 【0006】 One aspect of the present invention is a workpiece ejection device. This workpiece ejection device is applied to a machine tool comprising a headstock that rotatably supports a hollow spindle that detachably grips a workpiece, and a coolant supply device that supplies machining coolant to the workpiece, and operates when ejecting a workpiece gripped by the spindle. This workpiece ejection device comprises a pressing rod coaxially arranged inside the spindle and operating in the axial direction to press the workpiece and eject it from the spindle, and a cylinder arranged inside the spindle that operates the pressing rod in the axial direction by the supply of fluid pressure. The pressing rod has an internal passage formed through it for the flow of coolant supplied from the coolant supply device, and is configured to supply coolant toward the workpiece gripped by the spindle. 【0007】 Another aspect of the present invention is a machine tool. This machine tool comprises a hollow spindle for detachably gripping a workpiece, a headstock for rotatably supporting the spindle, a pressing rod coaxially positioned inside the spindle and acting in the axial direction to press the workpiece and discharge it from the spindle, a cylinder positioned inside the spindle and acting to operate the pressing rod in the axial direction by the supply of fluid pressure, and a coolant supply device for supplying machining coolant. The pressing rod is configured to have an internal passage through which coolant supplied from the coolant supply device flows, and to be able to supply coolant toward the workpiece gripped by the spindle. [Effects of the Invention] 【0008】 According to the present invention, it is possible to improve the functionality of the spindle while constructing a compact headstock equipped with a workpiece ejection function. [Brief explanation of the drawing] 【0009】 [Figure 1] This is a perspective view showing the external appearance of the machine tool according to this embodiment. [Figure 2] This is a hardware configuration diagram of a machine tool. [Figure 3]This is a perspective view showing the internal structure of a machine tool. [Figure 4] This is a front view showing the internal structure of the containment chamber. [Figure 5] This diagram shows the positional relationship between the first workpiece spindle and the second workpiece spindle. [Figure 6] This is a schematic cross-sectional view showing the configuration of the workpiece discharge device and its surroundings. [Figure 7] This is an enlarged view of section A in Figure 6. [Figure 8] Figure 7 is an enlarged view of section B, showing the configuration and operation of the cylinder. [Figure 9] This is an enlarged view of section C in Figure 7. [Figure 10] This diagram illustrates the operation of the workpiece ejection device. [Modes for carrying out the invention] 【0010】 One embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the machine tool is equipped with multiple headstocks, and a workpiece ejection device is mounted on one of the headstocks. By coaxially arranging the air cylinder for workpiece ejection inside the workpiece spindle, the headstock can be made compact. Furthermore, by providing a coolant flow passage in the piston rod of the air cylinder, so-called through-spindle coolant is realized, improving the functionality of the workpiece spindle. The overall configuration of the machine tool will be described first, followed by a description of specific application examples of the workpiece ejection device. 【0011】 Figure 1 is a perspective view showing the external appearance of a machine tool according to this embodiment. For convenience, the vertical, horizontal, and left-right directions, as viewed from the front of machine tool 1, will be described below as the X, Y, and Z directions, respectively. 【0012】 The machine tool 1 is a turning center that processes a workpiece into a desired shape while appropriately changing tools. A machining chamber 4 is provided inside the housing 2 of the machine tool 1 (inside the machine). The machining chamber 4 is surrounded by a splash guard that forms the side surface of the housing 2. A machining device for machining the workpiece is provided in the machining chamber 4. An operation panel 6 for operating the machining device is provided on the front surface of the housing 2. 【0013】 Adjacent to the housing 2 of the machine tool 1, a coolant tank 8 (see FIG. 3) for storing coolant supplied to the machining chamber 4 is provided. The coolant is used as cutting oil for removing heat and lubricating the tool and the workpiece during machining, and is also used as a cleaning liquid for removing chips scattered in the machining chamber 4. Since the coolant becomes misty in the machining chamber 4, if it is discharged outside the machine as it is, it will cause pollution in the factory. For this reason, the machine tool 1 is provided with a mist collector 10 for collecting the atomized coolant (also referred to as "oil mist"). 【0014】 A door 7 for accessing the inside of the machining chamber 4 is provided on the front surface of the housing 2, and an opening 11 for connecting a bar feeder 46 (see FIG. 4) described later is provided on the left side surface of the housing 2. A cover 13 that can open and close the opening 11 is attached. 【0015】 FIG. 2 is a hardware configuration diagram of the machine tool 1. The machine tool 1 includes an information processing device 100, a machining control device 102, and a machining device 104. The machining control device 102 functions as a numerical control unit and outputs a control signal to the machining device 104 according to a machining program (NC program). The machining device 104 drives the workpiece spindle according to an instruction from the machining control device 102, moves the tool, and machines the workpiece. 【0016】 The processing device 104 includes a workpiece spindle drive unit 110, a tool post drive unit 112, a coolant supply device 114, a mist collector drive unit 116, and a workpiece discharge device 118. In the present embodiment, as will be described later, a first workpiece spindle and a second workpiece spindle are provided as workpiece spindles capable of gripping a workpiece. The workpiece spindle drive unit 110 includes a first spindle drive unit 120 that drives the first workpiece spindle and a second spindle drive unit 122 that drives the second workpiece spindle. The tool post drive unit 112 drives a turret-type tool post, which will be described later. 【0017】 The coolant supply device 114 supplies machining coolant to the machining chamber 4. The coolant supply device 114 is configured by arranging, in addition to the coolant tank 8 described above, a coolant discharge portion, a pump, and a control valve, which are not shown, in a coolant circulation path. The coolant discharge portion includes a nozzle that discharges coolant and an actuator that drives the nozzle, and discharges the coolant toward a set target position. The pump pumps up the coolant stored in the coolant tank 8 and supplies it to the coolant discharge portion. The control valve includes a plurality of on-off valves and appropriately switches the flow path of the coolant in the coolant circulation path. 【0018】 The mist collector drive unit 116 drives the mist collector 10 when coolant is discharged in the machining chamber 4. The mist collector drive unit 116 includes a motor that drives the fan of the mist collector 10. The workpiece discharge device 118 operates when unloading a workpiece that has completed machining from the second workpiece spindle (details will be described later). 【0019】 The information processing device 100 includes an operation panel 6 and outputs a control command to the machining control device 102 based on an operator's operation input. The information processing device 100 also controls the screen displayed on the monitor of the operation panel 6 according to the operator's operation input. 【0020】 Each component of the information processing device 100 is realized by hardware including arithmetic units such as a CPU (Central Processing Unit) and various coprocessors, memory and storage devices, and wired or wireless communication lines connecting them, as well as software stored in the storage devices that supplies processing instructions to the arithmetic units. The computer program may consist of device drivers, an operating system, various application programs located at a higher layer, and libraries that provide common functions to these programs. 【0021】 Figure 3 is a perspective view showing the internal structure of machine tool 1. For ease of explanation, the front and left and right side covers (splash guards) of the housing 2 are shown removed. The machine tool 1 has a partition wall 12 that divides the space above the bed 3 (base) inside the housing 2 into a processing chamber 4 and a storage chamber 5. 【0022】 The machining apparatus 104 is configured by mounting a first headstock 14, a second headstock 16, and a tool post 18, etc., on the bed 3. The first headstock 14 is housed in the storage chamber 5, and the second headstock 16 and tool post 18 are housed in the machining chamber 4. The first headstock 14 rotatably supports the first workpiece spindle 20. The tip of the first workpiece spindle 20 penetrates the partition wall 12 and is exposed to the machining chamber 4. A chuck capable of gripping a workpiece is attached to the tip of the first workpiece spindle 20. The first workpiece spindle 20 is rotationally driven by the first spindle drive unit 120 described above. 【0023】 The second headstock 16 rotatably supports the second workpiece spindle 22. The second headstock 16 is covered with a dedicated cover 17 to prevent chips and coolant from entering. The second workpiece spindle 22 is exposed from the cover 17. A chuck capable of gripping a workpiece is attached to the tip of the second workpiece spindle 22. The second workpiece spindle 22 is rotationally driven by the second spindle drive unit 122 described above. The second workpiece spindle 22 can be replaced with a tailstock (not shown) as needed. 【0024】 The first work spindle 20 and the second work spindle 22 are arranged to face each other coaxially in the Z direction. The first headstock 14 and the second headstock 16 each have built-in spindle motors for rotating the work spindles. The second headstock 16 is movable in the Z direction by driving a moving mechanism (not shown). That is, the second headstock 16 can move the second work spindle 22 closer to or further away from the first work spindle 20, thereby adjusting the distance between the first work spindle 20 and the second work spindle 22. This moving mechanism is, for example, a screw feed mechanism using a ball screw. 【0025】 The tool post 18 is located in the machining chamber 4, further back in the depth direction than the second spindle head 16, and functions as a "tool holder." The tool post 18 comprises a turret base 24 and a turret 26. The turret base 24 has a rotation axis extending in the Z direction and rotatably supports the turret 26. The turret base 24 is equipped with a spindle motor for rotationally driving the turret 26. The turret 26 is provided with a plurality of clamping / unclamping mechanisms (not shown) along its periphery. These clamping / unclamping mechanisms allow for the attachment and detachment of multiple different types of tools (not shown). 【0026】 The turret base 24 is movable in the X, Y, and Z directions by driving a moving mechanism (not shown), allowing adjustment of the positional relationship between the workpieces gripped by each workpiece spindle and the tools held by the turret 26. This moving mechanism is, for example, a screw feed mechanism using a ball screw. 【0027】 With this configuration, the turret 26 is movable in the X, Y, and Z directions. Furthermore, the turret 26 is rotatable around an axis extending in the Z direction, thereby allowing for the switching of the tool used for machining. In other words, the turret 26 moves relative to the workpiece supported by one or both of the first workpiece spindle 20 and the second workpiece spindle 22 in three orthogonal axial directions, enabling cutting or turning of the workpiece using the tool. 【0028】 A coolant discharge unit is provided at a predetermined location in the machining chamber 4 (not shown). The coolant discharge unit discharges coolant toward the tool when machining the workpiece, and also discharges coolant to wash away chips scattered inside the machining chamber 4. Some or all of the tools supported by the turret 26 may also be equipped with the function of a so-called through-spindle coolant system. That is, an internal passage for circulating coolant may be provided in the tool, and this internal passage may be connected to a coolant circulation path. A discharge port is provided at the tip of the tool, forming one end of the internal passage and discharging coolant. By discharging coolant from the tip of the tool in this way during machining, it is possible to improve machining accuracy, shorten machining time, extend tool life, and improve chip evacuation performance. 【0029】 The mist collector 10 is positioned in the space above the first headstock 14 in the containment chamber 5. The partition wall 12 is provided with a mist intake port 28 that opens toward the machining chamber 4. The mist intake port 28 is connected to the mist collector 10 via piping 30. When the mist collector 10 is driven, oil mist in the machining chamber 4 is drawn into the mist intake port 28 and guided to the mist collector 10 through piping 30. The oil mist is collected inside the mist collector 10, and the purified air is discharged to the outside. Since the configuration of the mist collector 10 is publicly known, a detailed explanation thereof is omitted. 【0030】 Figure 4 is a front view showing the internal structure of containment chamber 5. A mist collector 10 is placed on a table 32 provided in the housing chamber 5. The first spindle head 14 is positioned towards the front in the depth direction of the housing chamber 5. The cover 13 is attached to the left side of the housing 2 (splash guard 2a) so that it is positioned opposite the first spindle head 14 and the first work spindle 20 in the axial direction. 【0031】 A bar feeder 46 can be installed on the outside of the splash guard 2a. The bar feeder 46 is a device that automatically supplies long workpieces W (bar stock) from behind the first work spindle 20. When connecting the bar feeder 46 to the machine tool 1, the cover 13 is removed to secure an insertion path for the workpieces W supplied from the bar feeder 46. The bar feeder 46 is equipped with a work stocker capable of accommodating workpieces W, a work feeder that takes workpieces W from the work stocker and sets them in a standby position, and a workpiece pushing mechanism that pushes the workpieces W set in the standby position toward the first work spindle 20. The configuration and operation of the bar feeder 46 are publicly known, as described in, for example, Japanese Patent Publication No. 7108148, so a detailed explanation is omitted. 【0032】 A chuck cylinder 48 is provided on the first spindle head 14. The chuck cylinder 48 drives a chuck 21 attached to the tip of the first workpiece spindle 20. In this embodiment, the chuck cylinder 48 is a hydraulic cylinder, but an air cylinder may also be used. The operation of the chuck cylinder 48 allows the chuck 21 to perform a gripping operation. The configuration and operation of such a chuck cylinder 48 are publicly known, as described in, for example, Japanese Patent Application Publication No. 2023-180634, so a detailed explanation is omitted. 【0033】 Figure 5 shows the positional relationship between the first workpiece spindle 20 and the second workpiece spindle 22. The first work spindle 20 and the second work spindle 22 are arranged to face each other in the Z direction. The axis L1 of the first work spindle 20 and the axis L2 of the second work spindle 22 coincide. The first work spindle 20 and the second work spindle 22 are rotationally driven around their axes. The second headstock 16 is movable in the Z direction, and the distance between the first work spindle 20 and the second work spindle 22 can be adjusted as appropriate. The second work spindle 22 has a chuck 23 for detachably gripping a workpiece W. The second headstock 16 is also provided with a chuck cylinder, similar to the first headstock 14, and the gripping operation of the chuck cylinder can be performed by operating the chuck cylinder. 【0034】 The turret 26 moves relative to the workpiece W in three orthogonal axial directions, and can cut or turn the workpiece W using any of the clamped tools T (T1, T2…). When turning the workpiece W, the workpiece spindle drive unit 110 drives the spindle motor to rotate one or both of the first workpiece spindle 20 and the second workpiece spindle 22. Subsequently, the servo motor is driven to feed the turret 26 and machine the workpiece W. 【0035】 After machining the workpiece W held by the first work spindle 20, the workpiece W can be transferred between the first work spindle 20 and the second work spindle 22. Specifically, after machining one end of the workpiece W while it is held by the first work spindle 20, the workpiece W is pushed out by the bar feeder 46, and that end of the workpiece W is held by the second work spindle 22. In this state, the workpiece W can be cut with the tool T and transferred to the second work spindle 22. After that, the other end of the workpiece W can be machined while it is held by the second work spindle 22. Alternatively, the two workpieces can be assembled by having both work spindles hold a workpiece and working in cooperation with both work spindles, and the resulting assembly (called the "workpiece assembly") can be subjected to secondary machining (finishing) while being held by one of the work spindles. 【0036】 Next, the workpiece discharge device of this embodiment will be described. Figure 6 is a schematic cross-sectional view showing the configuration of the workpiece discharge device 118 and its surroundings. Figure 7 is an enlarged view of section A in Figure 6. Figure 8 is an enlarged view of section B in Figure 7, showing the configuration and operation of the cylinder. Figure 9 is an enlarged view of section C in Figure 7. 【0037】 As shown in Figure 6, a workpiece discharge device 118 is provided on the second headstock 16. The workpiece discharge device 118 includes a pressing rod 50 for pushing out the workpiece W and a cylinder 52 (fluid pressure cylinder) for operating the pressing rod 50 in the axial direction. In this embodiment, an air cylinder is used as the cylinder 52. The second workpiece spindle 22 has a hollow structure and is rotationally driven around the axis L2 by a spindle motor 53 mounted on the second headstock 16. The pressing rod 50 and the cylinder 52 are arranged coaxially inside the second workpiece spindle 22. 【0038】 More specifically, a draw pipe 54 is coaxially positioned inside the second workpiece spindle 22. The draw pipe 54 can rotate integrally with the second workpiece spindle 22, and by moving relative to the second workpiece spindle 22 in the axial direction, it can open and close the chuck 23 and release the grip on the workpiece W. 【0039】 An operating member 56 is connected to the rear of the drawpipe 54. A chuck cylinder (not shown) is provided at the rear end of the second headstock 16 to drive the operating member 56 in the axial direction. In this embodiment, the chuck cylinder is a hydraulic cylinder, but it may also be an air cylinder. The second spindle drive unit 122 (see Figure 2) operates the chuck cylinder, thereby driving the drawpipe 54 in the axial direction via the operating member 56. This allows the chuck 23 to be opened and closed. Since the configuration and operation of such a chuck cylinder are well known, a detailed explanation thereof is omitted. 【0040】 The cylinder 52 includes an elongated housing 60 extending along the axis L2 of the second work spindle 22, and a piston rod 62 supported axially by the housing 60. The piston rod 62 constitutes part of the pressing rod 50. The housing 60 is constructed by coaxially connecting a front housing 64, a center housing 66, and a rear housing 68, and extends coaxially inward from the second work spindle 22. The rear housing 68 is a tubular member, and its base end is fixed to the second headstock 16 via a fixing member 70. The housing 60 is cantilevered by the fixing member 70. 【0041】 A disc-shaped pressing member 72 capable of pressing the workpiece W, which is gripped by the chuck 23, from the rear is fitted to the tip of the pressing rod 50. In this embodiment, the pressing member 72 is made of metal, but it may be made of an elastic material such as rubber. An internal passage 74 is formed so as to penetrate the pressing rod 50 in the axial direction. On the other hand, a guide hole 76 is provided so as to penetrate the rear housing 68 coaxially. The piston rod 62 that constitutes the rear end of the pressing rod 50 is inserted through the guide hole 76 and is supported by the rear housing 68 so as to be slidable in the axial direction. The guide hole 76 communicates with the internal passage 74 of the pressing rod 50 and has a connection port 78 that connects to the coolant supply device 114. 【0042】 As shown in Figure 7, the center housing 66 is constructed by assembling end members 82a and 82b to both ends of the cylinder tube 80. A pressure chamber 84 is formed inside the cylinder tube 80. The piston rod 62 penetrates the center housing 66 axially (i.e., through the pressure chamber 84), and a piston 86 is integrally provided in its middle section. The piston 86 is positioned in the pressure chamber 84. 【0043】 As shown in Figure 8, the piston 86 divides the pressure chamber 84 into a first pressure chamber 84a and a second pressure chamber 84b. A pipe 90a for supplying air to the first pressure chamber 84a is connected to the end member 82a. The end member 82a is provided with a connecting passage 88a that connects the pipe 90a to the first pressure chamber 84a. A pipe 90b for supplying air to the second pressure chamber 84b is connected to the end member 82b. The end member 82b is provided with a connecting passage 88b that connects the pipe 90b to the second pressure chamber 84b. The pipes 90a and 90b extend along the housing 60 inside the draw pipe 54 and are connected to an air supply source (not shown) installed outside the second headstock 16. By supplying air pressure from the air supply source to the first pressure chamber 84a or the second pressure chamber 84b, the piston rod 62 and thus the pressing rod 50 can be actuated in the axial direction. 【0044】 Specifically, by supplying air to the first pressure chamber 84a, the pressure in the first pressure chamber 84a becomes higher than the pressure in the second pressure chamber 84b, and this pressure difference causes the piston 86 to move backward. This allows the pressing rod 50 to be retracted (Figure 8(A)). At this time, the air in the second pressure chamber 84b is discharged through the piping 90b. 【0045】 Conversely, by supplying air to the second pressure chamber 84b, the pressure in the second pressure chamber 84b becomes higher than the pressure in the first pressure chamber 84a, and this pressure difference causes the piston 86 to move forward. This allows the pressing rod 50 to be advanced (Figure 8(B)). At this time, the air in the first pressure chamber 84a is discharged through the pipe 90a. 【0046】 Returning to Figure 7, the front housing 64 is assembled so as to pass through the tip of the end member 82a in the center housing 66, and the rear housing 68 is assembled so as to pass through the rear end of the end member 82b. A bearing unit 92 is provided between the draw pipe 54 and the front housing 64. The cylinder 52 has a two-point support structure in which the housing 60 is supported by the bearing unit 92 and the fixing member 70 (see Figure 6). Due to the presence of the bearing unit 92, the rotation of the draw pipe 54 is not transmitted to the cylinder 52. 【0047】 A support unit 94 for stably supporting the pressing rod 50 is assembled to the tip of the front housing 64 (details will be described later). The support unit 94 functions as a "support part". The pressing rod 50 includes a rod body 96 that is assembled coaxially to the tip of the piston rod 62, and a pressing element 98 connected to the tip of the rod body 96. The rod body 96 has a stepped cylindrical shape, and the tip of the piston rod 62 is inserted through and fixed to its rear end. An annular connecting member 99 is externally fitted and fixed to the tip of the rod body 96. 【0048】 The pressing element 98 is a tubular member and has a flange portion 98a extending radially outward at its rear end. The flange portion 98a is fixed to the connecting member 99 via a screw, thereby coaxially assembling the pressing element 98 to the rod body 96. A pressing member 72 is assembled to the tip of the pressing element 98. The internal passage 74 passes through multiple members constituting the pressing rod 50 (pressing element 98, rod body 96, and piston rod 62) in the axial direction. Furthermore, by making the pressing element 98 detachably assembled to the rod body 96, it is possible to replace it with a pressing element of a different length. 【0049】 As shown in Figure 9, the bearing unit 92 has a bottomed cylindrical body 130 and a plurality of bearings 132 assembled inside the body 130. The body 130 is fixed to the inner circumferential surface of the draw pipe 54, and a seal ring 140 (O-ring) is interposed between the outer circumferential surface of the body 130 and the inner circumferential surface of the draw pipe 54. An insertion hole 134 is provided at the bottom of the body 130 for passing through the front housing 64. 【0050】 The inner ring of the bearing 132 is fixed to the outer circumferential surface of the front housing 64, and the outer ring of the bearing 132 is fixed to the inner circumferential surface of the main body 130. The main body 130 rotates integrally with the draw pipe 54. A seal ring 142 (V-ring) is interposed between the outer circumferential surface of the front housing 64 and the bottom surface of the main body 130 to prevent coolant and foreign matter from entering the bearing unit 92 through the gap of the insertion hole 134. 【0051】 The support unit 94 has a cylindrical support body 150 and a cylindrical self-lubricating bush 152 positioned inside the support body 150. The rear end of the support body 150 is screw-connected to the front end of the front housing 64. A seal ring 144 (O-ring) is interposed between the outer circumferential surface of the front end of the front housing 64 and the inner circumferential surface of the support body 150. 【0052】 The self-lubricating bush 152 is fitted to the inner circumferential surface of the support body 150 and supports the rod body 96 so that it can slide in the axial direction. By interposing the self-lubricating bush 152 between the support body 150 and the rod body 96 in this way, vibration damping function can be achieved when the pressing rod 50 is in operation. A seal ring 146 (V-ring) is fitted to the inner circumferential surface of the tip of the support body 150. The seal ring 146 is interposed between the inner circumferential surface of the support body 150 and the outer circumferential surface of the rod body 96 and prevents coolant and foreign matter from entering the support unit 94. The seal rings 140 to 146 function as "seal members" that prevent coolant that has bounced back from the workpiece W from flowing back into the housing 60. 【0053】 Figure 10 is a diagram illustrating the operation of the workpiece discharge device 118. Figure 10(A) shows the operation during machining, and Figure 10(B) shows the operation when unloading the workpiece W after machining. During machining of the workpiece W, the pressing rod 50 retracts into the back of the chuck 23 (Figure 10(A)). The workpiece discharge device 118 functions as a coolant supply mechanism (through-spindle coolant device). That is, coolant is supplied through the internal passage 74 of the pressing rod 50 and discharged toward the workpiece W. In the illustrated example, boring is performed on the workpiece W, and coolant is discharged toward the inner circumferential surface of the workpiece W for lubrication during machining. 【0054】 On the other hand, when machining is complete, the workpiece discharge device 118 is activated and the pressing rod 50 moves toward the workpiece W (Figure 10(B)). At this time, the chuck cylinder is activated and the chuck 23 is opened, releasing the grip on the workpiece W. Therefore, the pressing rod 50 moves axially and the pressing member 72 presses the workpiece W from the rear, discharging the workpiece W from the second workpiece spindle 22. In other words, the contact between the chuck 23 and the workpiece W is released, and the workpiece W is detached from the chuck 23. The discharged workpiece W is received by a workpiece unloader (not shown) installed below the chuck 23. In a modified example, the gripping force of the workpiece W by the second workpiece spindle 22 (chuck 23) may be maintained to the extent that it is overcome by the thrust of the pressing rod 50, and the workpiece W may be discharged by activating the pressing rod 50 while the workpiece W is gripped by that gripping force. 【0055】 The machine tool has been described above based on the embodiments. In this embodiment, the cylinder 52 of the workpiece ejection device 118 is built into the second headstock 16. By arranging the cylinder 52 coaxially inside the draw pipe 54, the second headstock 16 can be made compact. Furthermore, by providing a coolant flow path so that the pressing rod 50, including the piston rod 62, passes through in the axial direction, through-spindle coolant can be realized, improving the functionality of the second workpiece spindle 22. 【0056】 Furthermore, the assembly of the pressing rod 50 and the cylinder 52 extends inside the second work spindle 22, and one end is fixed to the second headstock 16 via a fixing member 70. Thus, the elongated assembly is cantilevered at one end, but by providing a bearing unit 92 inside the draw pipe 54, the support rigidity can be increased, and the assembly can be supported stably. In addition, by providing a support unit 94 at the tip of the housing 60 and slidably supporting the pressing rod 50 with a self-lubricating bush 152, the stable operation of the pressing rod 50 can be maintained while exhibiting a vibration damping effect. 【0057】 [Differentiation] Although not described in the above embodiment, the workpiece discharge device 118 may also be provided with a function to supply cleaning air to the workpiece W (through-spindle air blow function). Specifically, the internal passages of the pressing rod 50 and cylinder 52 are connected to an air supply source via piping or the like. The piping connected to the internal passages may be branched into a path connected to a coolant tank and a path connected to an air supply source, and the system may be configured to allow switching between the two paths using a control valve or the like. By performing an air blow after the machining is completed, chips and coolant adhering to the workpiece W can be removed. 【0058】 In the above embodiment, an example was shown in which an air cylinder was used as the cylinder 52, but a hydraulic cylinder may also be used. Hydraulic pressure may be supplied instead of air pressure as the fluid pressure. 【0059】 In the above embodiment, an example was shown in which a hollow material was bored out as the workpiece W, but the workpiece may also be processed as a solid material. For example, a space (gap) may be provided between the workpiece and the chuck, and coolant may be discharged from the tip of the pressing rod towards that space to supply coolant to the outer surface of the workpiece. 【0060】 In the above embodiment, a first work spindle 20 and a second work spindle 22 are provided as work spindles, and the second work spindle 22 is configured to be movable in the Z direction. An example is shown in which both work spindles are arranged coaxially opposite each other in the Z direction. In a modified example, both the first work spindle 20 and the second work spindle 22 may be configured to be movable in the Z direction. Regardless of which work spindle is moved, both work spindles may be positioned closer together or further apart. 【0061】 Furthermore, at least one of the first headstock 14 and the second headstock 16 can be moved in the Y direction, allowing both workpiece spindles to be placed on the same axis, or even offset from each other. 【0062】 In the above embodiment, an example was shown in which multiple work spindles (first work spindle 20 and second work spindle 22) are provided, but a single work spindle may also be used. In that case as well, the above work ejection device can be applied to that work spindle. 【0063】 In the above embodiment, the machine tool 1 was described as a turning center, but it may also be a combined machining center that combines the functions of both a turning center and a machining center. It may also be a turning center-based combined machining center capable of milling and turning. 【0064】 When machine tool 1 is a multi-tasking machine, a tool spindle is provided instead of a turret (tool post). The tool spindle functions as a "tool holder" and is rotatably supported on the spindle head. The spindle head is driven in the X, Y, and Z directions by a moving mechanism. The multi-tasking machine is further provided with a tool storage unit and a tool changing unit. The tool storage unit includes a magazine for storing tools. The tool changing unit includes an ATC (Automatic Tool Changer) and, according to a change instruction from the machining control device 102, retrieves a tool from the tool storage unit and replaces it with the tool on the tool spindle. 【0065】 It should be noted that the present invention is not limited to the embodiments and modifications described above, and the components can be modified and implemented without departing from the spirit of the invention. Various inventions may be formed by appropriately combining the multiple components disclosed in the embodiments and modifications described above. In addition, some components may be deleted from all the components shown in the embodiments and modifications described above. [Explanation of symbols] 【0066】 1 Machine tool, 2 Housing, 4 Machining chamber, 6 Control panel, 8 Coolant tank, 10 Mist collector, 12 Partition wall, 14 First headstock, 16 Second headstock, 18 Tool post, 20 First work spindle, 21 Chuck, 22 Second work spindle, 23 Chuck, 26 Turret, 46 Bar feeder, 48 Chuck cylinder, 50 Pressing rod, 52 Cylinder, 53 Spindle motor, 54 Draw pipe, 56 Actuating member, 60 Housing, 62 Piston rod, 70 Fixing member, 72 Pressing member, 74 Internal passage, 76 Guide hole, 78 Connection port, 80 Cylinder tube, 84 Pressure chamber, 84a First pressure chamber, 84b Second pressure chamber, 86 Piston, 90a Piping, 90b Piping, 92 Bearing unit, 94 Support unit, 96 Rod body, 98 Pressing element, 99 Connecting member, 102 Machining control device, 104 Machining device, 110 Work spindle drive unit, 112 Tool post drive unit, 114 Coolant supply device, 118 Work discharge device, 120 First spindle drive unit, 122 Second spindle drive unit, 130 Main body, 132 Bearing, 134 Through hole, 140 Seal ring, 142 Seal ring, 144 Seal ring, 146 Seal ring, 150 Support, 152 Self-lubricating bush, T Tool, W Workpiece.

Claims

[Claim 1] A workpiece ejection device is applied to a machine tool comprising a headstock that rotatably supports a hollow spindle that grips a workpiece and to which a workpiece can be attached and detached, and a coolant supply device that supplies machining coolant to the workpiece, and which operates when ejecting a workpiece gripped by the spindle, A pressing rod is coaxially positioned inside the main spindle and operates in the axial direction to press the workpiece and discharge it from the main spindle. The system includes a cylinder located inside the main shaft, which operates the pressing rod in the axial direction by supplying fluid pressure, The pressing rod is configured to have an internal passage through which coolant supplied from the coolant supply device flows, and to be able to supply coolant towards the workpiece held by the spindle, in the workpiece discharge device. [Claim 2] The cylinder is A housing extending into the main shaft and having a pressure chamber in the middle where a piston operates, The piston is integrally provided with the piston rod, which penetrates the pressure chamber in the axial direction, The piston rod constitutes a part of the pressing rod, and the internal passage penetrates the piston rod in the axial direction. The housing has a guide hole through which the piston rod is slidably inserted, The workpiece discharge device according to claim 1, wherein the guide hole communicates with the internal passage of the pressing rod and has a connection port connected to the coolant supply device. [Claim 3] A support portion is provided at the tip of the housing for slidably supporting the pressing rod. The workpiece discharge device according to claim 2, wherein the support portion has a sealing member that prevents coolant from flowing back into the housing. [Claim 4] The workpiece discharge device according to claim 3, wherein the support portion includes a self-lubricating bush that slidably supports the pressing rod. [Claim 5] A hollow spindle that grips the workpiece and allows the workpiece to be attached and detached, A spindle head that rotatably supports the aforementioned spindle, A pressing rod is coaxially positioned inside the main spindle and operates in the axial direction to press the workpiece and discharge it from the main spindle. A cylinder is positioned inside the main shaft and operates the pressing rod in the axial direction by supplying fluid pressure, It includes a coolant supply device that supplies coolant for machining, A machine tool wherein the pressing rod has an internal passage formed through it for the flow of coolant supplied from the coolant supply device, and is configured to supply coolant toward a workpiece held by the spindle. [Claim 6] The system further comprises a draw pipe that is coaxially arranged inside the main spindle, is rotatable integrally with the main spindle, and can release the grip of the workpiece by the main spindle by moving relative to the main spindle in the axial direction, The machine tool according to claim 5, wherein the pressing rod is arranged coaxially inside the draw pipe.

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