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 for detecting that a moving body is disposed at a predetermined position with respect to a fixed body used, for example, in a machine tool.

Background Art

[0002] As shown in Patent Document 1, the applicant has filed an application for a workpiece unloader using a turret capable of indexing a tool to be used at a predetermined angle, to which various tools are attached in a machine tool. This workpiece unloader includes a bucket that receives a workpiece whose machining has been completed on a workpiece spindle, a support body that is fixed to a tool mounting surface and supports the bucket so as to be swingable around a swing axis parallel to the swing axis of the turret, and an air cylinder provided so as to extend radially from a protruding portion on the inner tip side of the turret so that a piston rod advances and retracts with respect to an engagement hole formed in the bottom surface portion of the bucket.

[0003] When the tip of the piston rod advances and is inserted into the engagement hole, the bucket is in a locked state where its swing is restricted. Conversely, when the tip of the rear piston rod retracts and exits from the engagement hole, the bucket is in an unlocked state where it can swing freely. Since the movement of this workpiece unloader is controlled using a turret that acts on a workpiece with a tool, it is necessary to acquire information as to whether the bucket is in a locked state or an unlocked state in 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 how far the piston rod has advanced or retracted.

[0005] By the way, since there are demands for miniaturization and high functionality of turrets, it is becoming difficult to arrange a part of a piston rod, a proximity sensor, etc. inside the protruding part of the turret. Further, even if it could be arranged inside the protruding part of the turret, the inside of the turret may be sealed in order to protect electronic devices and the like from a coolant or the like, and it is also becoming difficult to pass electrical wiring for acquiring signals from a proximity sensor through such a part.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the problems described above, and an object thereof is to provide a position detection device that can detect the movement of various actuators such as an air cylinder provided in a place where electrical wiring cannot be passed, and can be suitably used for, for example, a turret of a machine tool.

Means for Solving the Problems

[0008] That is, the position detection device according to the present invention is a position detection device that detects that a moving body that slides with respect to a fixed body is disposed at a predetermined position, and is formed inside the fixed body, and a fluid filling portion that opens to a sliding surface of the fixed body, a pressure sensor that detects the pressure of the fluid filling portion, and a detection recess formed in the moving body so as to coincide with the opening of the fluid filling portion when the moving body is disposed at the predetermined position.

[0009] In such a case, when the moving body is present outside the predetermined position at the opening of the fluid filling portion, the pressure inside the fluid filling portion is maintained at a predetermined pressure. On the other hand, when the moving body is disposed at the predetermined position and the opening of the fluid filling portion coincides with the detection recess, fluid can flow out from the fluid filling portion to the outside to reduce the pressure. Therefore, it is possible to determine that the moving body is disposed at the predetermined position based on the decrease in the pressure detected by the pressure sensor. Further, even if the fixed body and the moving body are provided in a place where it is difficult to pass through electrical wiring, the pressure sensor may be provided at a place separated from the fluid filling portion and communicating therewith so that the pressure is propagated. Thus, it is possible to detect the position of the moving body even in a place where a proximity sensor cannot be used as in the prior art.

[0010] As a specific mode of detecting the position of the moving body based on pressure, there is an example including a determination device that determines that the moving body is disposed at the predetermined position when the pressure detected by the pressure sensor becomes equal to or lower than a threshold value.

[0011] As a specific example to which the detection principle of the position of the moving body according to the present invention can be preferably applied, there is an air cylinder including the position detection device according to the present invention, the fixed body that is a cylinder tube, and the moving body that is a piston rod.

[0012] In order to easily cause a pressure change necessary for detecting the position of the tip of the piston rod, the fluid filling portion may be an internal pipe formed in 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] When it is arranged at a part where the air cylinder rotates and there is only a narrow and sealed space through which it is difficult to pass electrical wiring, in order to be able to detect the pressure of the fluid filling part with the pressure sensor provided at a remote location and increase the degree of freedom of the configuration, the internal pipe has a tip-side opening that opens to the sliding surface of the cylinder tube and a base-end side opening that opens to the end of the cylinder tube, and further includes a rotary joint provided between the pressure sensor and the base-end side opening, and the pressure sensor may be configured to detect the pressure inside the internal pipe via the rotary joint.

[0014] As a preferred application example of the air cylinder according to the present invention, there is a turret swing type work unloader provided on a turret of a machine tool, which includes a bucket that receives a work held by a work spindle from a receiving port, a support that swingably supports the bucket in the swing direction of the turret from the tool mounting surface of the turret, a turret head protruding in the turning axis direction of the turret, and the air cylinder according to claim 3 provided between the bucket, and a work unloader configured such that the bucket can be switched between an unlocked state where it can freely swing and a locked state where the swing is restricted by the forward and backward movement of the piston rod of the air cylinder, and a machine tool using the same can be mentioned.

Advantages of the Invention

[0015] Thus, in the case of the position detection device according to the present invention, there is no need to provide a sensor that requires electrical wiring in the vicinity of the moving body, and it is possible to detect the position of the moving body even in a place where the space is narrow or sealed, such as inside the turret of a machine tool.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

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

[0018] In FIGS. 1 and 2, the machine tool 200 is a multi-tasking lathe (multi-tasking machine), which, when viewed from the front of the machine, has spindle heads arranged at both the left and right ends of the bed, and a tool post arranged between the left and right spindle heads so as to be movable in the X-axis direction and the Z-axis direction, and a machine body cover surrounding the outer peripheral portion of the lathe body.

[0019] The spindle head has a structure in which a spindle for gripping the work W is rotatably supported. This spindle is rotationally driven by a drive motor.

[0020] The tool rest includes a tool rest body supported movably by a bed, and a turret T mounted on the tool rest body. This turret T has a structure in which a turret head T2 having a substantially octagonal column shape with a plurality of tools mounted at predetermined intervals on the outer peripheral portion is supported by a swing indexing base T1 so as to be swing indexable, and a required tool is rotated and indexed to a machining position (work receiving position) vertically above and clamped at the machining position. In each figure, although tools are actually mounted on the tool mounting surface TA of the turret head T2, only the work unloader described orally is shown for simplicity, and the description of the tools is omitted.

[0021] The machine tool 200 is configured to perform predetermined machining on a work W held by a chuck of a main spindle by causing any one of the tools mounted on the turret T to act thereon.

[0022] This machine tool 200 is provided with a work discharging device for discharging the machined work W outside the machine. This discharging device includes a bucket 1 disposed on the turret T for receiving the machined work W held by the chuck at the work receiving position which is the machining position, and a storage box for swinging the work W in the bucket 1 to a work discharging position using the swing of the turret head T2 and storing it through a shooter.

[0023] The bucket 1 has a substantially V-shaped cross section with a receiving port and is supported by a support 2. This support 2 has an upward-facing U-shaped shape in front view, and one of the bottom plate portions thereof is bolted and fixed to the tool mounting surface TA of the turret head T2. Further, the other bottom plate portion of the support is fixed to an air cylinder 3 provided so as to project radially with respect to a protruding portion T3 of the turret head T2 described orally.

[0024] The bucket 1 is supported swingably with respect to the support 2. That is, it is supported swingably around a swing axis L2 parallel to the swing axis L1 of the turret head T2.

[0025] Furthermore, an engagement hole 11 is formed in the bottom surface portion of the bucket 1, and the tip of the piston rod 32 that slidably moves forward and backward with respect to the cylinder tube 31, which is a fixed body of the air cylinder 3, is configured to advance or retract into the engagement hole 11. When the tip of the piston rod 32 is inserted into the engagement hole 11 of the bucket 1, the rotation of the bucket around the swing axis L2 is restricted to a locked state. Therefore, in this locked state, even if the turret head T2 rotates around the rotation axis L1, as shown in FIG. 3, the opening direction of the bucket 1 is maintained in a state facing the outside in the radial direction of the turret head T2. On the other hand, when the piston rod 32 retracts and its tip extends outside the engagement hole 11 of the bucket 1, the bucket 1 is in an unlocked state where it can freely swing around the swing axis L2. In this state, as shown in FIG. 4, the opening of the bucket 1 is configured to be substantially upward while the turret head T2 rotates within a predetermined angle range. That is, within the rotation range of the turret 2 between the work receiving position and the work discharging position, the opening of the bucket 1 in the unlocked state is always upward so that the work does not naturally fall downward.

[0026] A position detection device for detecting the position of the tip of the piston rod in the air cylinder 3 includes a first pressure sensor and a second pressure sensor provided outside the turret, more specifically, near the CNC or the like, and the state of the piston rod is determined based on the output of each pressure sensor. That is, no sensors or the like that require electrical wiring are arranged inside the turret T.

[0027] First, the details of the position detection device for determining the position of the tip of the piston rod will be described with reference to FIG. 5. The cylinder tube 31 is a cylindrical body having a substantially annular cross section, and a sliding surface on which the tip of the piston rod slides is formed on at least a part of the inner surface. Further, inside the partition wall of the cylinder tube 31, a fluid filling portion 33 for allowing, for example, compressed air or the like to flow and being filled with compressed air is formed as, for example, a thin cylindrical internal pipe. The fluid filling portion 33 forms a narrow hole along the axial direction of the cylinder tube 31 and also forms a narrow hole in the radial direction of the cylinder tube in a region where the sliding surface is formed, and is formed by closing the opening on the outer peripheral surface side. That is, the fluid filling portion 33 is a space having a tip side opening 34 that opens to the sliding surface and a base end side opening 36 that opens to the end surface portion of the cylinder tube 31 disposed on the side opposite to the bucket 1. A predetermined amount of compressed air flows in from the base end side opening 36. Here, when the tip side opening 34 is blocked by the outer peripheral surface of the piston rod, the inside of the fluid filling portion 33 is pressurized. On the other hand, an annular groove is formed as a detection recess 35 in a part of the outer peripheral surface on the tip side of the piston rod. When the tip side opening 34 and the detection recess 35 coincide with each other, a part of the air comes out from the fluid filling portion 33, and in that case, the pressure inside the fluid filling portion 33 drops below the predetermined pressure.

[0028] In this embodiment, as shown in FIG. 1, the position detection device includes a pair of fluid filling portions 33, a first pressure sensor P1 and a second pressure sensor P2 that individually measure the respective pressures, and a determination mechanism J that determines the position of the tip of the piston rod 32 based on the outputs of the pressure sensors P1 and P2. Here, each pressure sensor is not provided inside or in the vicinity of the air cylinder 3 and the turret T, but is provided at a remote location that communicates with the fluid filling portion 33 and through which the pressure can be transmitted. Specifically, for example, the pressure sensors P1 and P2 are arranged on the ceiling portion of the machine tool, and the fluid filling portion 33 and the pressure sensors P1 and P2 are connected by a flow path. Here, as shown in FIG. 1, the protruding portion T3 of the turret T is a rotating portion and is a sealed space, so electrical wiring cannot be passed through. On the other hand, a rotary joint RJ is provided in the protruding portion T3, enabling the transport of fluid between the outside of the protruding portion T3 and the fluid filling portion of the air cylinder 3. That is, the pressure sensors P1 and P2 are configured to detect the pressure in the fluid filling portion 33 via the rotary joint RJ. Therefore, it is not necessary to provide a sensor for position detection in the protruding portion T3, nor is electrical wiring or the like required to output its signal.

[0029] Returning to FIG. 5 again, there are three tip-side openings 34, which are provided side by side in the axial direction of the air cylinder 3. Further, two detection recesses 35 are provided on the piston rod. The position detection device of the present embodiment is configured to be able to determine the position of the tip of the piston rod 32 in three ways by the combination of the state in which the three tip-side openings 34 and the two detection recesses 35 match. FIG. 5 detects the case where the piston rod 32 has retracted the most and the bucket 1 is in the unlocked state. That is, only the tip-side opening 34 of the fluid filling portion 33 on the left side in FIG. 5 and the detection recess 35 on the tip side of the piston rod 32 match, and the two tip-side openings 34 of the fluid filling portion 33 on the right side are blocked by the side surface of the piston rod. Therefore, the pressure detected by the first pressure sensor P1 becomes lower than the predetermined pressure and is in the OFF state, while the pressure detected by the second pressure sensor P2 is in the ON state above the predetermined pressure. When the first pressure sensor P1 is OFF and the second pressure sensor P2 is in the ON state, the determination unit J determines that the bucket 1 is in the unlocked state as shown in FIG. 5.

[0030] FIG. 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, since the tip-side opening 34 of the fluid filling portion 33 on the left side is blocked by the outer surface of the piston rod 32, the pressure measured by the first pressure sensor P1 becomes higher than the threshold pressure and is in the ON state. On the other hand, since the lower tip-side opening 34 of the fluid filling portion 33 on the right side matches the detection recess 34, a pressure drop occurs, and the pressure detected by the second pressure sensor P2 becomes below the threshold pressure and is in the OF state. In the case of this combination of outputs of the pressure sensors P1 and P2, the determination device J determines that the bucket 1 is in the locked state.

[0031] Finally, as shown in FIG. 7, when the piston rod 32 has advanced to the maximum while the bucket 1 is swinging and fails to be inserted into the engagement hole 11 and goes into a state of hitting the air, the tip-side openings 34 of the left and right fluid filling portions 33 respectively coincide with separate detection recesses 35. In this case, both the first pressure sensor P1 and the second pressure sensor P2 are in the OFF state. In the case of such an output combination, the discriminator J generates an alert to the PLC or the like, assuming that an abnormal air-striking has occurred.

[0032] As described above, in the workpiece unloader 100 of this embodiment, even if the air cylinder 3 is provided at a location where it is difficult to pass electrical wiring in the turret T, 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 surely unlocked during the operation of discharging the processed workpiece W, or to surely lock the bucket 1 so as not to interfere with the processing by the tool attached to the turret T during the processing of the workpiece W.

[0033] Other embodiments will be described. Although a gas such as compressed air is preferably filled in the fluid filling portion, a liquid may also be used. Further, a gas-liquid mixture may be used. The air cylinder and the position detection device according to the present invention are not limited to application to the workpiece unloader, and may be used for other purposes in a machine tool. The shape of the detection recess is not limited to an annular groove. In short, it may be a cavity such as a recess that causes a pressure drop in the fluid filling portion when the tip-side opening and the detection recess are in alignment. In addition, various modifications and combinations of embodiments may be made as long as they do not depart from the spirit of the present invention.

Explanation of Reference Numerals

[0034] 200... Machine tool, 100... Workpiece unloader, 1... Bucket, 2... Support. 3... Air cylinder, 31... Cylinder tube (fixed body) 32... Piston rod (movable body), 33... Fluid filling portion, 34... Tip-side opening, 35... Detection recess

Claims

1. A position detection device for detecting that a moving body that slides relative to a fixed body is disposed at a predetermined position, comprising: a fluid filling portion that is formed within the fixed body and opens to a sliding surface of the fixed body; a pressure sensor that detects the pressure of the fluid filling portion; and a detection recess formed in the moving body so as to coincide with the opening of the fluid filling portion when the moving body is disposed at the predetermined position.

2. The position detection device according to claim 1, further comprising a determination unit that determines that the moving body is disposed at the predetermined position when the pressure detected by the pressure sensor becomes equal to or less than a threshold value.

3. An air cylinder comprising the position detection device according to claim 1 or 2, the fixed body that is a cylinder tube, and the moving body that is a piston rod.

4. The air cylinder according to claim 3, wherein the fluid filling portion is an internal pipe formed within a partition wall of the cylinder tube, and the detection recess is a ring-shaped groove formed on a side surface of the piston rod.

5. The internal pipe includes a tip-side opening that opens to a sliding surface of the cylinder tube and a base-end side opening that opens to an end portion of the cylinder tube, further comprising a rotary joint provided between the pressure sensor and the base-end side opening, and the pressure sensor is configured to detect the pressure within the internal pipe via the rotary joint.

6. A turret-swing type workpiece unloader provided on a turret of a machine tool, comprising: a bucket that receives a workpiece held by a workpiece spindle from a receiving port; a support that swingably supports the bucket in a swing direction of the turret from a tool mounting surface of the turret; and the air cylinder according to claim 3 provided between a turret head protruding in a turning axis direction of the turret and the bucket, wherein the workpiece unloader is configured such that an unlocking state in which the bucket can freely swing and a locking state in which swinging is restricted are switched by forward and backward movement of the piston rod of the air cylinder.

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

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