Position detection device, air cylinder, workpiece unloader, and machine tool

Abstract

To provide a position detection device which can detect motion of various actuators, such as an air cylinder, provided at locations where electric wiring cannot be arranged and can be preferably used in, for example, a turret of a machine tool.SOLUTION: A position detection device detects a state that a moving body 32 which slides relative to a fixed body 31 is disposed at a predetermined position and includes: a fluid filling portion 33 that is formed in the fixed body 31 and open on a sliding surface of the fixed body 31; a pressure sensor P1 that detects a pressure of the fluid filling portion 33; and a detection recessed portion 35 that is formed in the moving body 32 so as to be aligned with an opening 34 of the fluid filling portion 33 when the moving body 32 is disposed at the predetermined position.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a position detection device that detects whether a moving body is placed at a predetermined position relative to a fixed body used in, for example, a machine tool. [Background technology]

[0002] As shown in Patent Document 1, the applicant has filed a patent application for a workpiece unloader that utilizes a turret on a machine tool to which various tools are attached and that can index the tools being used at a predetermined angle. This workpiece unloader includes a bucket that receives workpieces that have been machined on the workpiece spindle, a support that is fixed to the tool mounting surface and supports the bucket so that it can swing around a swing axis parallel to the turret's rotation axis, and an air cylinder that extends radially from a protruding portion on the inboard tip side of the turret so that a piston rod can advance and retreat with respect to an engagement hole formed in the bottom surface of the bucket.

[0003] When the tip of the piston rod advances and is inserted into the engagement hole, the bucket is locked and its swing is restricted. Conversely, when the tip of the rear piston rod retreats and leaves the engagement hole, the bucket is unlocked and can swing freely. Because the movement of this work unloader is controlled using a turret that applies a tool to the workpiece, it is necessary to obtain information on whether the bucket is locked or unlocked at each process.

[0004] For this reason, a part of the air cylinder is disposed inside the protruding portion of the turret, and a proximity sensor disposed inside the turret detects to what position the piston rod has advanced or retracted.

[0005] However, due to the demand for smaller and more sophisticated turrets, it is becoming increasingly difficult to place a portion of the piston rod, a proximity sensor, etc. inside the protruding portion of the turret. Even if it were possible to place them inside the protruding portion of the turret, the inside of the turret may be sealed to protect electronic devices, etc. from coolant, etc., and it is becoming increasingly difficult to run electrical wiring through such a part to acquire signals from the proximity sensor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-144850 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a position detection device that can detect the movement of various actuators, such as air cylinders, that are installed in places where electrical wiring cannot be passed, and that can be suitably used for, for example, the turret of a machine tool. [Means for solving the problem]

[0008] In other words, the position detection device of the present invention is a position detection device that detects when a movable body that slides relative to a fixed body is placed at a predetermined position, and is characterized by comprising: a fluid-filled section formed within the fixed body and opening onto the sliding surface of the fixed body; a pressure sensor that detects the pressure of the fluid-filled section; and a detection recess formed in the movable body so as to match the opening of the fluid-filled section when the movable body is placed at the predetermined position.

[0009] With this configuration, when the movable body is located at a position other than the predetermined position where the opening of the fluid-filled section is located, the pressure inside the fluid-filled section is maintained at a predetermined pressure, whereas when the movable body is located at the predetermined position and the opening of the fluid-filled section and the detection recess are aligned, fluid flows out of the fluid-filled section, reducing the pressure. Therefore, it is possible to determine that the movable body has been located at the predetermined position by a decrease in pressure detected by the pressure sensor. Furthermore, even if the fixed body and the movable body are located in a location where it is difficult to pass electrical wiring, the pressure sensor can be located in a remote location where it is in communication with the fluid-filled section and where the pressure is transmitted. This makes it possible to detect the position of the movable body even in locations where it is not possible to use a proximity sensor as in the past.

[0010] A specific example of detecting the position of the moving body based on pressure is one that further includes a determiner that determines that the moving body has been placed at the specified position when the pressure detected by the pressure sensor becomes equal to or lower than a threshold value.

[0011] A specific example to which the principle of detecting the position of a moving body according to the present invention can be suitably applied is an air cylinder equipped with the position detection device according to the present invention, the fixed body being a cylinder tube, and the moving body being a piston rod.

[0012] To facilitate the generation of the pressure change required to detect the position of the tip of the piston rod, the fluid-filled portion may be an internal pipe formed within the partition wall of the cylinder tube, and the detection recess may be a ring-shaped groove formed on the side surface of the piston rod.

[0013] In order to increase the degree of freedom in configuration by enabling the pressure of the fluid-filled section to be detected by the pressure sensor installed in a remote location even when the air cylinder is arranged in a rotating location and there is only a narrow, sealed space where it is difficult to pass electrical wiring, the internal piping may have a tip-side opening that opens to the sliding surface of the cylinder tube and a base-side opening that opens to the end of the cylinder tube, and may further include a rotary joint installed between the pressure sensor and the base-side opening, and the pressure sensor may be configured to detect the pressure in the internal piping via the rotary joint.

[0014] A suitable application example of the air cylinder according to the present invention is a turret-swivel type work unloader mounted on the turret of a machine tool, comprising: a bucket that receives a workpiece held by a work spindle through a receiving port; a support that supports the bucket so that it can swing from the tool mounting surface of the turret in the rotation direction of the turret; and an air cylinder according to claim 3 that is mounted between the bucket and a turret head that protrudes in the rotation axis direction of the turret, and a work unloader configured so that the bucket can be switched between an unlocked state in which it can swing freely and a locked state in which its swing is restricted by moving the piston rod of the air cylinder back and forth, and a machine tool using the work unloader. [Effects of the Invention]

[0015] In this way, with the position detection device according to the present invention, there is no need to provide a sensor that requires electrical wiring near the moving body, and it is possible to detect the position of the moving body even in a narrow or sealed space such as inside the turret of a machine tool. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a workpiece unloader and a machine tool equipped with the same according to an embodiment of the present invention; [Figure 2] Schematic cross-sectional view taken along line AA in Figure 1. [Figure 3]FIG. 10 is a schematic diagram showing an example of movement when the bucket of the workpiece unloader is in a locked state. [Figure 4] FIG. 10 is a schematic diagram showing an example of movement when the bucket of the workpiece unloader is in an unlocked state. [Figure 5] 5A and 5B are schematic diagrams illustrating detection of the position of the tip of the piston rod when the bucket of the workpiece unloader is in an unlocked state. [Figure 6] 5A and 5B are schematic diagrams illustrating detection of the position of the tip of the piston rod when the bucket of the workpiece unloader is in a locked state. [Figure 7] 5A and 5B are schematic diagrams illustrating detection of the position of the tip of the piston rod when the bucket of the workpiece unloader is in an empty strike state. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a machine tool 200, a workpiece unloader 100, an air cylinder 3, and a position detection device according to one embodiment of the present invention will be described with reference to the respective drawings.

[0018] 1 and 2, machine tool 200 is a multi-tasking lathe (multi-tasking machine), which, when viewed from the front of the machine, has a headstock disposed at each of the left and right ends of the bed, and is equipped with a lathe body having a tool rest disposed between the left and right headstocks so as to be movable in the X-axis and Z-axis directions, and a machine body cover that surrounds the outer periphery of the lathe body.

[0019] The headstock has a structure that rotatably supports a spindle to which a chuck that grips a workpiece W is attached. This spindle is rotated by a drive motor.

[0020] The tool rest includes a tool rest main body movably supported by the bed, and a turret T mounted on the tool rest main body. The turret T has a structure in which a turret head T2, which is roughly octagonal and has a plurality of tools attached to its outer periphery at predetermined intervals, is supported by a swivel indexing table T1 so that the turret T can swivel and index the required tool to a machining position (workpiece receiving position) vertically above, and then clamp it at that machining position. Note that, although tools are actually attached to the tool mounting surface TA of the turret head T2 in each drawing, for simplicity, only the workpiece unloader described below is shown, and the tools are not shown.

[0021] The machine tool 200 is configured to perform predetermined machining by applying any of the tools attached to the turret T to a workpiece W held in a chuck of the spindle.

[0022] This machine tool 200 is equipped with a workpiece ejection device that ejects machined workpieces W outside the machine. This ejection device is arranged on the turret T and includes a bucket 1 that receives the machined workpiece W held by the chuck at a workpiece receiving position, which is a machining position, and a storage box that rotates the workpiece W in the bucket 1 to the workpiece ejection position using the rotation of the turret head T2 and stores the workpiece W via a chute.

[0023] Bucket 1 has a generally V-shaped cross section with a receiving opening and is supported by support body 2. This support body 2 has an upward U-shape when viewed from the front, and one of its bottom plate portions is fixed by bolts to tool mounting surface TA of turret head T2. The other bottom plate portion of the support body is fixed to air cylinder 3 provided so as to protrude radially from protrusion T3 of turret head T2.

[0024] The bucket 1 is supported so as to be swingable relative to the support body 2. That is, the bucket 1 is supported so as to be swingable about a swing axis L2 that is parallel to the rotation axis L1 of the turret head T2.

[0025] Furthermore, an engagement hole 11 is formed in the bottom surface of the bucket 1, and the tip of a piston rod 32, which slides freely relative to a cylinder tube 31, which is the fixed body of the air cylinder 3, is configured to advance or retreat into or from the engagement hole 11. When the tip of the piston rod 32 is inserted into the engagement hole 11 of the bucket 1, the bucket is locked and its rotation around the swing axis L2 is restricted. Therefore, in this locked state, even when the turret head T2 swings around the swing axis L1, the opening of the bucket 1 remains facing radially outward of the turret head T2, as shown in Figure 3. On the other hand, when the piston rod 32 retreats and its tip protrudes outside the engagement hole 11 of the bucket 1, the bucket 1 is unlocked and can swing freely around the swing axis L2. In this state, the opening of the bucket 1 faces approximately upward while the turret head T2 swings within a predetermined angle range, as shown in Figure 4. In other words, in the rotation range of the turret 2 between the workpiece receiving position and the workpiece discharging position, the opening of the unlocked bucket 1 always faces upward, so that the workpiece does not naturally fall downward.

[0026] The position detection device that detects the position of the tip of the piston rod in the air cylinder 3 is equipped with a first pressure sensor and a second pressure sensor that are provided outside the turret, more specifically, near the CNC, and the state of the piston rod is determined based on the output of each pressure sensor. In other words, no sensors that require electrical wiring are provided inside the turret T.

[0027] First, with reference to FIG. 5 , the position detection device for determining the position of the tip of the piston rod will be described in detail. The cylinder tube 31 is a cylindrical body with a generally annular cross section, and at least a portion of its inner surface forms a sliding surface along which the tip of the piston rod slides. A fluid-filled section 33, which allows, for example, compressed air to flow and is filled with compressed air, is formed within the partition wall of the cylinder tube 31 as, for example, a thin cylindrical internal conduit. The fluid-filled section 33 is formed by forming a narrow hole along the axial direction of the cylinder tube 31 and a narrow hole in the radial direction of the cylinder tube in the region where the sliding surface is formed, and closing the opening on the outer circumferential surface. That is, the fluid-filled section 33 is a space including a tip-side opening 34 that opens to the sliding surface and a base-side opening 36 that opens to the end face of the cylinder tube 31 located opposite the bucket 1. A predetermined amount of compressed air flows in through the base-side opening 36. When the tip-side opening 34 is closed by the outer circumferential surface of the piston rod, the fluid-filled section 33 is pressurized. Meanwhile, an annular groove is formed on part of the outer peripheral surface of the tip end of the piston rod as a detection recess 35. When the tip end opening 34 and the detection recess 35 are aligned, some air will escape from the fluid-filled portion 33 to the outside, and in that case the pressure inside the fluid-filled portion 33 will drop below a predetermined pressure.

[0028] In this embodiment, as shown in FIG. 1 , the position detection device includes a pair of fluid-filled sections 33, a first pressure sensor P1 and a second pressure sensor P2 that measure the pressures of the respective fluid-filled sections 33 individually, and a determiner J that determines the position of the tip of the piston rod 32 based on the outputs of the pressure sensors P1 and P2. The pressure sensors are not located within or near the air cylinder 3 or turret T, but are instead located in a remote location that communicates with the fluid-filled section 33 and where the pressure can propagate. Specifically, the pressure sensors P1 and P2 are located, for example, on the ceiling of the machine tool, and the fluid-filled section 33 and the pressure sensors P1 and P2 are connected by a flow path. As shown in FIG. 1 , the protruding section T3 of the turret T is a rotating section and an enclosed space, so electrical wiring cannot be passed through it. Meanwhile, a rotary joint RJ is located within the protruding section T3, allowing fluid to be transported between the outside of the protruding section T3 and the fluid-filled section of the air cylinder 3. In other words, the pressure sensors P1 and P2 are configured to detect the pressure within the fluid-filled section 33 via the rotary joint RJ. Therefore, there is no need to provide a sensor for detecting the position inside the protrusion T3, and there is no need for electrical wiring or the like for outputting the signal.

[0029] Returning to FIG. 5 , there are three tip-side openings 34, arranged side by side in the axial direction of the air cylinder 3. Two detection recesses 35 are also provided on the piston rod. The position detection device of this embodiment is configured to determine three different positions of the tip of the piston rod 32 based on the combination of alignment states between the three tip-side openings 34 and the two detection recesses 35. FIG. 5 shows a state where the piston rod 32 is fully retracted and the bucket 1 is in an unlocked state. That is, only the tip-side opening 34 of the fluid-filled portion 33 on the left side of FIG. 5 is aligned with the detection recess 35 on the tip side of the piston rod 32, while the two tip-side openings 34 of the fluid-filled portion 33 on the right side are blocked by the side of the piston rod. Therefore, the pressure detected by the first pressure sensor P1 is lower than the predetermined pressure and is in the OFF state. Meanwhile, the pressure detected by the second pressure sensor P2 is higher than the predetermined pressure and is in the ON state. When the first pressure sensor P1 is in the OFF state and the second pressure sensor P2 is in the ON state, the determinator J determines that the bucket 1 is in the unlocked state, as shown in FIG. 5 .

[0030] 6 shows a state in which the tip of the piston rod 32 is inserted into the engagement hole 11 of the bucket 1. In this case, the tip opening 34 of the left-side fluid-filled portion 33 is blocked by the outer surface of the piston rod 32, so the pressure measured by the first pressure sensor P1 exceeds the threshold pressure, resulting in an ON state. On the other hand, the lower tip opening 34 of the right-side fluid-filled portion 33 matches the detection recess 34, so a pressure drop occurs and the pressure detected by the second pressure sensor P2 falls below the threshold pressure, resulting in an OFF state. When the outputs of the pressure sensors P1 and P2 are combined as described above, the determiner J determines that the bucket 1 is in a locked state.

[0031] Finally, as shown in Figure 7, if the piston rod 32 advances to its maximum extent while the bucket 1 is swinging and is not inserted into the engagement hole 11, resulting in a state of abrupt impact, the tip-end openings 34 of the left and right fluid-filled sections 33 will each match with different detection recesses 35. In this case, both the first pressure sensor P1 and the second pressure sensor P2 will be in the OFF state. With this type of output combination, the determiner J will detect abrupt impact abnormality and issue an alert to the PLC or the like.

[0032] As described above, with the workpiece unloader 100 of this embodiment, even if the air cylinder 3 is provided in a location on the turret T where it is difficult to pass electrical wiring, it is possible to detect the position of the tip of the piston rod 32 based on the pressure of the fluid. Therefore, it is possible to determine that the bucket 1 is reliably unlocked when unloading a machined workpiece W, and to reliably lock the bucket 1 when machining the workpiece W so as not to interfere with machining by a tool attached to the turret T.

[0033] Other embodiments will be described. The fluid-filled section is preferably filled with a gas such as compressed air, but may also be a liquid. A gas-liquid mixture may also be used. The air cylinder and position detection device according to the present invention are not limited to use in workpiece unloaders, but may also be used for other applications in machine tools. The shape of the detection recess is not limited to an annular groove. In other words, it may be a cavity such as a recess that causes a drop in pressure within the fluid-filled section when the positions of the tip-end opening and the detection recess are aligned. Various modifications and combinations of the embodiments may also be made as long as they do not deviate from the spirit of the present invention. [Explanation of symbols]

[0034] 200...machine tool, 100...workpiece unloader, 1...bucket, 2...support, 3...air cylinder, 31...cylinder tube (fixed body), 32...piston rod (moving body), 33...fluid-filled portion, 34...tip-side opening, 35...detection recess

Claims

1. A position detection device that detects that a moving body that slides relative to a fixed body is placed at a predetermined position, a pair of fluid-filled portions formed within the fixed body and each opening individually onto a sliding surface of the fixed body; a first pressure sensor and a second pressure sensor that individually detect the pressures of the pair of fluid-filled sections; a plurality of the predetermined positions are set, and a pair of detection recesses are formed on the movable body so as to align with at least one of the openings of the pair of fluid-filled portions when the movable body is placed at any of the predetermined positions; one of the pair of fluid-filled portions has an opening at one location on the sliding surface of the fixed body, The other of the pair of fluid-filled portions has two openings aligned in the sliding direction of the movable body on the sliding surface of the fixed body.

2. The position detection device of claim 1, further comprising a determiner that determines that the moving body is located at one of the predetermined positions based on a combination of the detection results when the pressure detected by the first pressure sensor or the second pressure sensor becomes below a threshold value.

3. a position detection device according to claim 1 or 2; the fixed body being a cylinder tube; the moving body being a piston rod.

4. the pair of fluid-filled portions are a pair of internal pipes individually formed within the partition walls of the cylinder tube, 4. An air cylinder according to claim 3, wherein the detection recess is a ring-shaped groove formed on the side surface of the piston rod.

5. the pair of fluid-filled portions are a pair of internal pipes individually formed within the partition walls of the cylinder tube, each of the pair of internal pipes has a tip-side opening that opens to a sliding surface of the cylinder tube and a base-side opening that opens to an end of the cylinder tube; a rotary joint provided between the first pressure sensor and the base end opening, and a rotary joint provided between the second pressure sensor and the base end opening, 4. The air cylinder according to claim 3, wherein the first pressure sensor and the second pressure sensor are configured to detect the pressures in the pair of internal pipes via the rotary joint, respectively.

6. A turret-swivel type workpiece unloader provided on a turret of a machine tool, a bucket that receives the workpiece held by the workpiece spindle through a receiving port; a support body that supports the bucket so that the bucket can swing from a tool mounting surface of the turret in a rotation direction of the turret; the air cylinder according to claim 3, which is provided between a turret head protruding in the direction of the rotation axis of the turret and the bucket; The workpiece unloader is configured so that the bucket can be switched between an unlocked state in which it can swing freely and a locked state in which its swing is restricted by advancing and retreating the piston rod of the air cylinder.

7. A machine tool equipped with the workpiece unloader according to claim 6.

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