Drive system, position detection device and method

Abstract

To enable a drive system to be manufactured with a simple configuration at low cost, and enable a position of the drive system to be detected consecutively.SOLUTION: A drive system 100 comprises: an actuator 102; a driven member 122 driven by the actuator; and a position detection device 10 interposed between the actuator and the driven member. The position detection device 10 comprises: a housing 12; a movable body 14 movably provided in an internal space of the housing; a passage 16 opening to an inner surface of the housing; a tapered surface 20 formed on the movable body 14 so as to be able to face the passage 16; a pressure fluid source 110 that supplies pressure fluid to the passage 16; a sensor 120 that detects an amount of leakage of the pressure fluid; and a control device 106 that calculates the position of the movable body 14 in a movement direction relative to the housing based on the detected amount of leakage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drive system that drives a driven member by an actuator, and a position detection device and method for measuring the position of a moving body. [Background technology]

[0002] Actuators such as fluid pressure cylinders are used in a variety of fields to drive driven members, but in order to use the actuator, it is necessary to detect its position. For example, Patent Document 1 describes a clamping device driven by a hydraulic cylinder, in which the clamping position and unclamping position are detected by using pressurized air from an air pressure source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-072891 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the invention of Patent Document 1, a clamp confirmation flow path and an unclamping confirmation flow path are provided, and each flow path requires a pressure sensor as a clamp pressure confirmation means and a pressure sensor as an unclamping pressure means. Also, the clamp confirmation flow path and the unclamping confirmation flow path each have two clamp confirmation flow paths and two unclamping confirmation flow paths. When in the clamped position, the pressure in the unclamp confirmation flow path, which is formed by the two unclamping confirmation flow paths communicating with each other, is reduced to atmospheric pressure, which is detected by the clamp confirmation pressure sensor, and when in the unclamping position, the pressure in the unclamp confirmation flow path, which is formed by the two unclamping confirmation flow paths communicating with each other, is reduced to atmospheric pressure, which is detected by the clamp confirmation pressure sensor.

[0005] In the invention of Patent Document 1, the two confirmation flow paths are separated and independent sensors are used, which makes the configuration complicated and increases the manufacturing cost. Furthermore, the invention of Patent Document 1 has a problem that it can only confirm two positions, the clamped position and the unclamped position.

[0006] The present invention has as its technical object to solve the problems of the conventional technology, and aims to provide a drive system that has a simpler configuration, can be manufactured at low cost, and is capable of continuous position detection.

[0007] Another object of the present invention is to provide an apparatus and method for detecting the position of a moving object for use in such a drive system. [Means for solving the problem]

[0008] In order to achieve the above object, according to the present invention, there is provided a drive system comprising an actuator, a driven member driven in a predetermined direction by the actuator, and a position detection device interposed between the actuator and the driven member, The position detection device includes a housing having an inner surface that defines an internal space, a movable body that is movable in the predetermined direction within the internal space, a passage that opens to the inner surface of the housing, a tapered surface formed on the movable body that is capable of facing the passage, the tapered surface being formed so that the gap between the inner surface and the tapered surface gradually changes along the predetermined direction, a pressure fluid source that supplies pressure fluid to the passage, a sensor that detects the amount of leakage of the pressure fluid, and a calculation device that calculates the position of the movable body relative to the housing based on the detected amount of leakage.

[0009] According to the present invention, there is further provided a position detection device comprising: a housing having an inner surface defining an internal space; a movable body arranged to be movable in a predetermined direction within the internal space; a passage opening to the inner surface of the housing; a tapered surface formed on the movable body to be able to face the passage, the tapered surface being formed so that a gap between the inner surface and the tapered surface gradually changes along the predetermined direction; a pressure fluid source supplying pressure fluid to the passage; a sensor detecting an amount of leakage of the pressure fluid; and a calculation device calculating a position of the movable body relative to the housing based on the detected amount of leakage.

[0010] According to the present invention, there is further provided a method for measuring the position of a movable body provided to be movable in a predetermined direction within an internal space of a housing having an inner surface that defines the internal space, the housing having a passage that opens to the inner surface, the movable body having a tapered surface formed to be able to face the passage, the tapered surface being formed so that a gap between the inner surface and the tapered surface gradually changes along the predetermined direction, The measurement method provides a method for detecting the position of a moving body, comprising the steps of supplying pressurized fluid to the passage, detecting the amount of leakage of the pressurized fluid, and calculating the position of the moving body relative to the housing based on the detected amount of leakage. Effect of the Invention

[0011] According to the present invention, it is possible to continuously obtain the position of a moving body and / or an actuator using a single sensor based on the output value from the sensor. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic block diagram showing an embodiment of a drive system equipped with a position detection device of the present invention; [Diagram 2] 2 is an enlarged cross-sectional view of a portion indicated by a circle A in FIG. [Diagram 3]3 is a schematic partial side view of the moving body as seen in the direction of arrow III-III in FIG. 2. [Figure 4] 2 is a schematic diagram for explaining the operation of the position detection device according to the embodiment of FIG. 1, showing a moving body in which a starting point of a tapered surface faces a passageway. FIG. [Diagram 5] 6 is a schematic diagram for explaining the operation of a position detection device similar to that of FIG. 5, showing a moving body whose path faces between the start and end points of a tapered surface; [Figure 6] 6 is a schematic diagram for explaining the operation of a position detection device similar to that of FIG. 5, showing a moving body in which the end point of a tapered surface faces a passageway. [Figure 7] 13 is a view showing a tapered surface according to another example of the present invention, when the housing and the movable body are viewed in the axial direction. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 1, the drive system 100 includes an actuator 102 and a control device 106 that controls the actuator 102. The control device 106 can be composed of a computer and associated software including a CPU (Central Processing Unit), a memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), a storage device such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive), input / output ports for transmitting / receiving digital or analog signals, and a bidirectional bus for interconnecting these. The input / output ports may include terminals capable of outputting a drive current to another device.

[0014] When the drive system 100 is used in conjunction with a machine tool (not shown) or other machine, the control device 106 can be configured in software as part of a machine control device that controls an NC device (not shown) that controls a machine such as a machine tool, a tool magazine (not shown) of the machine tool, an automatic tool changer (not shown), a machining fluid supply device, an oil / air supply device, a compressed air supply device, and other related equipment of the machine tool.

[0015] The actuator 102 may be a linear actuator. The linear actuator may be a fluid pressure cylinder, such as a pneumatic cylinder or a hydraulic cylinder, or an electric actuator, such as a linear motor. The linear actuator may further be formed of a fluid pressure or electric rotary motor (not shown) having a ball screw (not shown), a nut that engages with the ball screw, and a rotary shaft (not shown) that is coupled to one end of the ball screw.

[0016] 1 shown as an example, the linear actuator is a pneumatic cylinder to which compressed air is supplied from an air pressure source 110 as a pressure fluid source via an outlet pipe 112 and a driving air supply pipe 114. The pneumatic cylinder as the actuator 102 includes a cylinder and a piston provided so as to be capable of reciprocating within the cylinder in the direction of a central axis Oa as a predetermined axis.

[0017] The air pressure source 110 may include, for example, a compressor (not shown) that pressurizes air, a tank (not shown) that stores the air pressurized by the compressor, a dryer (not shown) that dries the air output from the tank, a shutoff valve (not shown) provided in an outlet pipe 112 of the tank, and / or a pressure regulating valve (not shown) that adjusts the pressure in the outlet pipe 112 of the tank to a constant pressure. The compressor and the shutoff valve of the air pressure source 110 may be controlled by the control device 106.

[0018] More specifically, a driving air supply pipe 114 branching from the outlet pipe 112 is further branched into first and second branch pipes 114a, 114b by a switching valve 116, which are connected to a pneumatic cylinder serving as the actuator 102. In Fig. 1, the switching valve 116 is a two-position, four-port solenoid valve controlled by the control device 106, and in the first position shown in the figure, pressurized air is supplied from the pneumatic source 110 to the extension side port 102a of the pneumatic cylinder serving as the actuator 102, and in the second position not shown, pressurized air is supplied to the retraction side port 102b. The switching valve 116 may be a three-position switching valve further having a neutral position.

[0019] The actuator 102 also includes an action member 104 that is provided so as to be capable of reciprocating in the direction of the central axis Oa. If the actuator 102 is a fluid pressure linear actuator, the action member 104 may be a piston rod that is connected to a piston and protrudes from one end of a cylinder. If the actuator 102 is a linear motor, the action member 104 may be an armature on the moving side of the linear motor or a coupling member connected to the armature. If the actuator 102 is an assembly consisting of a ball screw, a nut, and an electric motor, the action member 104 may be a nut that engages with the ball screw or a coupling member connected to the nut.

[0020] In the present invention, a driven member 122 driven by the actuator 102 is coupled to the acting member 104 of the actuator 102 via the position sensing device 10. The driven member 122 can be various members that can be driven by the actuator 102. As an example, the driven member 122 can be a clamping device (not shown) that fixes a pallet (not shown) on which a workpiece (not shown) is attached to a table (not shown) of a machine tool (not shown).

[0021] The position detection device 10 includes a hollow housing 12 and a movable body 14 disposed in the housing 12 so as to be movable in a predetermined direction. The movable body 14 is coupled to an actuator 102 at one end. In the embodiment of FIG. 1, the movable body 14 is coupled to an action member 104 of a pneumatic cylinder serving as the actuator 102 at a right end. The movable body 14 is coupled to a driven member 122 via a coupling member 108 provided at the opposite end (the left end in FIG. 1). The coupling member 108 may include a gripping mechanism such as a chuck (not shown) or a coupling mechanism that allows relative movement between the driven member 122 and the movable body 14, such as a swinging mechanism, a rotating mechanism, or a link mechanism (not shown).

[0022] The housing 12 has an inner surface 12a and an outer surface 12b that define an internal space of the housing 12. In this embodiment, the inner surface 12a is formed in a cylindrical surface shape having a central axis O. The movable body 14 is formed in a roughly columnar shape that is coaxial with the cylindrical inner surface 12a, and is capable of reciprocating along the central axis O along the inner surface 12a. That is, in this embodiment, the predetermined direction is a direction along the central axis O. Also, a passage 16 is formed that penetrates the housing 12 and extends from the outer surface 12b to the inner surface 12a. In the embodiment shown in FIG. 1, the central axis O of the position detection device 10 and the central axis Oa of the pneumatic cylinder as the actuator 102 are aligned, but the central axes O and Oa do not necessarily need to be aligned, and may be parallel to each other.

[0023] The passage 16 is supplied with pressurized air from the air pressure source 110 via a detection air supply line 118 branched off from an outlet line 112 of the tank of the air pressure source 110. A leak sensor 120 connected to the control device 106 is disposed in the detection air supply line 118. The leak sensor 120 detects the amount of air flowing through the detection air supply line 118, i.e., the amount of leakage. The amount of leakage can be the pressure, flow rate or flow velocity of the air flowing through the detection air supply line 118. Typically, the leak sensor 120 can be formed by a pressure transmitter that detects the pressure across the leak sensor 120. In this way, the amount of leakage of air flowing through the detection air supply line 118 is output to the control device 106.

[0024] A groove 18 extending in the axial direction is formed on the side surface 14b of the moving body 14. In the embodiment shown in Figs. 1 to 3, the groove 18 is disposed in the vicinity of the end of the moving body 14 that is coupled to the working member 104 of the actuator 102, and opens to the end surface 14a of the moving body 14 to form an open end 18a. The groove 18 has a tapered surface 20 that can face the passage 16. The tapered surface 20 is formed so that the gap δ between the inner surface 12a and the tapered surface 20 gradually changes in the moving direction, which in this embodiment is along the central axis O of the moving body 14. More specifically, the tapered surface 20 is inclined in the radial direction with respect to the central axis O so that the gap δ gradually becomes larger along the central axis O toward the open end 18a. The tapered surface 20 is preferably a flat surface. That is, the tapered surface 20 can be formed so that the gap δ between the inner surface 12a and the tapered surface 20 changes linearly along the central axis O.

[0025] In the embodiment of FIG. 1, the end point 20a of the tapered surface 20 where the gap δ is maximum is offset from the end face 14a of the movable body 14 along the central axis O. Thus, a parallel surface 22 is formed between the tapered surface 20 and the end face 14a, or between the end point 20a of the tapered surface 20 and the opening end 18a of the groove 18, where the gap with the inner surface 12a is a constant section. The parallel surface 22 is parallel to the central axis O. The tapered surface 20 can be formed so that the gap δ is maximum at the end face 14a of the movable body 14. In other words, the tapered surface 20 may be formed so that the end point 20a is located at the end face 14a of the movable body 14 or the opening end 18a of the groove 18.

[0026] The operation of this embodiment will now be described. When the control device 106 excites the solenoid 116a from the state shown in Fig. 4, the switching valve 116 moves to the first position shown in Fig. 1, and pressurized air is supplied from the air pressure source 110 to the extension side port 102a of the air cylinder serving as the actuator 102 via the first branch pipe 114a, and pressurized air from the retraction side port 102b of the air cylinder is exhausted to the outside via the second branch pipe 114b. As a result, the air cylinder extends, and the operating member 104 moves leftward in Fig. 1 along the central axis Oa, and therefore the moving body 14 of the position detection device 10 moves leftward in Fig. 1 along the central axis O together with the connecting member 108 (see Figs. 5 and 6). As a result, the driven member 122 is driven in a predetermined direction.

[0027] When the control device 106 deenergizes the solenoid 106a from the state shown in Fig. 6, the switching valve 116 is biased by the spring 116b and moves to the second position, and pressurized air is supplied from the air pressure source 110 to the retraction side port 102b of the air cylinder as the actuator 102 via the second branch pipe 114b, and pressurized air from the extension side port 102a of the air cylinder is exhausted to the outside via the first branch pipe 114a. As a result, the air cylinder retracts, and the operating member 104 moves to the right in Fig. 1 along the central axis Oa, and therefore the moving body 14 of the position detection device 10 moves to the right in Fig. 1 along the central axis O together with the connecting member 108 (see Figs. 5 and 4). As a result, the driven member 122 is driven in the opposite direction to the predetermined direction.

[0028] While the moving body 14 is moving as described above or while the moving body 14 is stationary, pressurized air is continuously supplied from the air pressure source 110 to the passage 16 through the detection air supply pipe 118. The amount of air leaking through the detection air supply pipe 118 is detected by the leak sensor 120, and a corresponding signal is output to the control device 106. Since the smaller the gap δ is, the greater the resistance of the air flow at the outlet of the passage 16 is, so that if the relationship between the position of the moving body 14 along the central axis O and the output value from the leak sensor 120 to the control device 106 is obtained in advance by experiment or the like, the position of the moving body 14 along the central axis O can be obtained based on the output value of the leak sensor 120. In this embodiment, the control device 106 constitutes a calculation device that stores in advance a table or a formula indicating the relationship between the position of the moving body 14 along the central axis O and the output value from the leak sensor 120 to the control device 106, and calculates the position of the moving body 14 based on the output value from the leak sensor 120.

[0029] The tapered surface 20 can be formed so that, for example, when the actuator 102 is at a retraction end point or retraction stroke end (X=Xr), the passage 16 faces a start point 20b of the tapered surface 20 as shown in Fig. 4, and when the actuator 102 is at an extension point or extension stroke end (X=Xe), the passage 16 faces an end point 20a of the tapered surface 20 as shown in Fig. 6. Here, X is the position coordinate of the movable body 14 along the central axis O.

[0030] By forming the tapered surface 20 so that the gap δ with the inner surface 12a changes linearly along the central axis O, the movement distance (X-Xr) of the movable body 14 along the central axis O becomes proportional to the output value from the leak sensor 120. Furthermore, by providing the groove 18 with the parallel surface 22, when the passage 16 faces the end point 20a of the tapered surface 20, it is possible to reduce eddies generated in the flow of air passing through the groove 18 or reduce turbulence, compared to when the end point 20a of the tapered surface 20 is formed on the end face 14a of the movable body 14.

[0031] In the embodiment described above, the tapered surface 20 is a plane inclined with respect to the central axis O formed on the side surface 14b of the movable body 14, but the present invention is not limited to this. The tapered surface may be formed in the circumferential direction on the outer surface of the movable body, as shown in Fig. 7. In other words, the movable body may be disposed in the housing so as to be rotatable around the central axis O as the predetermined direction.

[0032] In this case, the actuator 102 is a rotary motor, and the moving body 14' is coupled to a rotary shaft of the rotary motor and is rotatable around the central axis O. The tapered surface 20' is formed so that a gap δ' with respect to the inner surface 12a' of the housing 12' gradually changes in the circumferential direction around the central axis O. The tapered surface 20' is preferably formed so that the gap δ' changes linearly in the circumferential direction, that is, so that the gap δ' is proportional to the rotation angle θ of the moving body 14' around the central axis O from a starting point 20b' (θ=θ0) of the tapered surface 20'.

[0033] According to this embodiment, the control device 106 as a calculation device can determine the position of the moving body 14, that is, the position of the working member 104 or piston of the pneumatic cylinder as the actuator 102, steplessly, that is, continuously, based on the output value from the leak sensor 120, that is, the acquired leak amount. As a result, when the drive system 100 is used as a drive device for a clamp device that fixes a pallet on which a workpiece of a machine tool is attached to the table of the machine tool, it becomes possible to change the clamp position for each type of workpiece, detect incorrect setup, and automatically detect wear of touch parts. In addition, since pressurized air is used for position detection, it becomes possible to easily install it in the machining space of the machine tool.

[0034] In the embodiment described above, the movable body 14 is a cylindrical member, but the present invention is not limited thereto. The movable body may be a member having a prismatic shape such as a square prism whose cross-sectional shape perpendicular to the central axis O as the predetermined direction does not change along the central axis O, as long as it is movable in a predetermined direction within the housing. When the movable body is formed into a square prism, a groove can be preferably formed on one side of the square prism. [Explanation of symbols]

[0035] 10 Position detection device 12. Housing 12a Inside 12b External surface 14 Mobile 14a End face 14b Side 16 Aisle 18 groove 18a Open end 20 Tapered surface 20a End point 20b Starting point 22 Parallel Planes 100 Drive System 102 Actuator 102a Extension port 102b Retraction port 104 Working member 106 Control device 106a Solenoid 108 Connecting member 110 Air pressure source 110 Pressure fluid source 112 Outlet pipe 114 Drive air supply line 114a first branch pipe 114b Second branch pipe 116 Switching valve 116a Solenoid 118 Detection air supply line 120 Leak Sensor 122 Driven member

Claims

1. In the drive system, An actuator; a driven member that is driven in a predetermined direction by the actuator; a position detection device interposed between the actuator and the driven member, The position detection device is a housing having an interior surface defining an interior space; a movable body provided in the internal space so as to be movable in the predetermined direction; a passageway opening to an inner surface of the housing; a tapered surface formed on the moving body so as to be able to face the passage, the tapered surface being formed so that a gap between the inner surface and the tapered surface gradually changes along the predetermined direction; a pressure fluid source for supplying pressure fluid to the passage; a sensor for detecting a leakage amount of the pressure fluid; a calculation device that calculates a position of the movable body relative to the housing based on the detected amount of leakage; A drive system comprising:

2. 2. The drive system according to claim 1, wherein the inner surface is formed into a cylindrical surface having a central axis, and the movable body is formed into a generally columnar shape coaxial with the cylindrical surface of the inner surface.

3. 3. The drive system according to claim 2, wherein the actuator is a direct acting fluid pressure cylinder including a cylinder and a piston reciprocally disposed within the cylinder, and the movable body is coupled to the piston and reciprocally movable together with the piston in the direction of the central axis.

4. 4. The drive system according to claim 3, wherein the tapered surface is formed so that the gap becomes gradually larger in the axial direction toward the end of the moving body.

5. 5. The drive system of claim 4, wherein said tapered surface causes said gap to vary linearly in the axial direction.

6. 3. The drive system according to claim 2, wherein the actuator is a rotary motor having a rotary shaft, and the movable body is coupled to the rotary shaft and is rotatable about the central axis.

7. The drive system according to claim 6 , wherein the tapered surface is formed so that the gap gradually changes in a circumferential direction about the central axis.

8. The drive system of claim 7 , wherein the tapered surface has a gap that varies linearly in a circumferential direction.

9. In the position detection device, a housing having an interior surface defining an interior space; A movable body provided so as to be movable in a predetermined direction within the internal space; a passageway opening to an inner surface of the housing; a tapered surface formed on the moving body so as to be able to face the passage, the tapered surface being formed so that a gap between the inner surface and the tapered surface gradually changes along the predetermined direction; a pressure fluid source for supplying pressure fluid to the passage; a sensor for detecting a leakage amount of the pressure fluid; a calculation device that calculates a position of the movable body relative to the housing based on the detected amount of leakage; A position detection device comprising:

10. 10. The position detection device according to claim 9, wherein the inner surface is formed into a cylindrical surface having a central axis, and the movable body is formed into a generally columnar shape coaxial with the inner cylindrical surface.

11. The position detection device according to claim 10, wherein the movable body is movable in the direction of the central axis.

12. 12. The position detection device according to claim 11, wherein the tapered surface is formed so that the gap becomes gradually larger in the axial direction toward the end of the moving body.

13. The position sensing device according to claim 12 , wherein the tapered surface causes the gap to vary linearly in the axial direction.

14. 11. The position detection device according to claim 10, wherein the movable body is rotatable about the central axis.

15. The position detection device according to claim 14 , wherein the tapered surface is formed so that the gap changes in a circumferential direction about the central axis.

16. The position detection device according to claim 15 , wherein the tapered surface has a gap that changes linearly in a circumferential direction.

17. A method for measuring the position of a movable body provided movable in a predetermined direction within an internal space of a housing having an inner surface defining the internal space, comprising: the housing has a passageway opening to the inner surface, the movable body has a tapered surface formed to be able to face the passageway, and the tapered surface is formed so that a gap between the inner surface and the tapered surface gradually changes along the predetermined direction, The measurement method includes: supplying a pressurized fluid to the passage; detecting a leakage amount of the pressure fluid; calculating a position of the movable body relative to the housing based on the detected amount of leakage; A method for detecting the position of a moving object, comprising:

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