JP2005324277A - Clamp device and clamping confirmation method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clamp device capable of easily and accurately determining whether a workpiece is normally clamped or not in a short period of time by a simple constitution. <P>SOLUTION: The workpiece W is clamped by driving a clamp arm 2 to be opened and closed by supplying a working fluid to a hydraulic cylinder 1 in the clamp device. The clamp device is provided with the clamp arm 2, the hydraulic cylinder 1, a working fluid supply source 3 for supplying operating oil to the hydraulic cylinder 1, a pressure sensor 4 for measuring the pressure P of the operating oil, and a control means 5 for controlling on the basis of the pressure P of the operating oil measured by the pressure sensor 4. A determining means 6 of the control means 5 determines whether the workpiece W is normally clamped or not by determining whether the pressure P of the working fluid reaches prescribed pressure P1 or not during a time in a prescribed range a-b from the supply start of the operating oil to the hydraulic cylinder 1 until the supply completion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a clamp device and a clamp confirmation method for fixing and holding a workpiece for machining, and in particular, a clamp device for clamping a workpiece by opening and closing a clamp member by supplying a working fluid to a fluid pressure cylinder, In addition, the present invention relates to a clamp confirmation method for determining whether or not the workpiece has been normally clamped in this clamp device.

For example, in a line in which workpieces are automatically conveyed and sequentially processed, a clamp device configured to automatically position and hold the conveyed workpiece in each machining step is provided.
The clamp device generally includes a clamp arm 2 as a clamp member that clamps a workpiece W, a fluid pressure cylinder 1 that drives the clamp arm 2 to open and close, and a working fluid supply source 3 that supplies a working fluid to the fluid pressure cylinder 1. (See FIG. 1). In such a clamping device, in order to detect whether or not the workpiece W is normally clamped, the working fluid pressure when the working fluid is supplied from the working fluid supply source to the fluid pressure cylinder and the workpiece is clamped. Pressure sensing means such as a pressure gauge, pressure switch, or pressure sensor is provided to detect whether (clamping force) is appropriate, and the amount of movement of the clamp member and fluid to detect whether the clamp member has been properly opened and closed In order to detect the drive stroke of the pressure cylinder, a limit switch, a proximity switch, an air switch, or a linear scale or an encoder (hereinafter referred to as switches) has been conventionally provided (for example, (See Patent Document 1).

JP-A-11-19837

  Patent Document 1 discloses a piston for simultaneously processing inner and outer peripheral surfaces of a workpiece by clamping a plurality of stacked workpieces with a hydraulic pressure supplied to a hydraulic cylinder provided on at least one of upper and lower workpiece support means. In a workpiece clamping device of a ring processing machine, a clamp detection means for detecting a clamping force of a workpiece from a hydraulic pressure supplied to the hydraulic cylinder, and a misclamping and clamping of the workpiece from a stroke of a piston provided in the hydraulic cylinder Further, there is disclosed a work clamp device for a piston ring processing machine, comprising: a work detection means for detecting unclamping; and a control means for judging normality / abnormality based on signals from the detection means. . Patent Document 1 describes that a clamp detection means including a pressure switch is provided, and the clamp detection means can detect a clamped or unclamped state of the workpiece (paragraph number 0024). In addition, it is described that a switch group including a mis-clamp detection amount limit switch, a clamp detection amount limit switch, and an unclamp detection switch is provided corresponding to the position of the lever of the workpiece detection means ( Paragraph numbers 0025, 0026).

  Also, in a clamping device using a fluid pressure cylinder, the pipe connecting the working fluid supply source and the fluid pressure cylinder expands, or the volume of the working fluid itself expands or contracts due to temperature, etc. Thus, immediately after the completion of clamping, the pressure of the working fluid is not stable, and it becomes difficult to detect the working fluid pressure when the workpiece is clamped by the pressure detecting means. For this reason, in the conventional clamping device, it has been conventionally performed to detect the pressure by the pressure detecting means when the pressure of the working fluid is stabilized after a predetermined time has elapsed since the completion of the clamping, for example, by providing a timer.

However, in Patent Document 1, it is necessary to provide a misclamp detection amount limit switch, a clamp detection amount limit switch, and an unclamp detection switch corresponding to the position of the lever of the workpiece detection means. There was a problem that the equipment cost was high. Even in other conventional techniques, it is necessary to provide switches such as a proximity switch and an air switch for confirming the opening and closing of the clamp member, and to detect the pressure of the working fluid in a stable state. Therefore, it is difficult to reduce the equipment cost. Furthermore, there is a problem that a program for processing signals transmitted by these switches becomes complicated. Furthermore, in the case where a timer is provided for detecting the pressure of the working fluid in a stable state, the time for detecting the pressure of the working fluid is determined when a predetermined time has elapsed since the completion of clamping. There was a problem that it took.
Furthermore, when a workpiece is clamped to perform cutting, generally coolant is supplied between the workpiece and the cutting tool, and chips are generated by the cutting. In the above conventional technology, when the coolant is applied to the switches or chips are attached, there is a problem that it is impossible to accurately determine whether or not the workpiece is normally clamped by inducing a malfunction of these switches, In order to avoid such a problem, it has been necessary to take measures to make the switches waterproof and prevent chips from adhering.
And in any of the above conventional techniques, even if it can be determined that none of the workpieces can be clamped normally, it is possible to specify what cause the workpiece could not be clamped normally. could not.

  The present invention has been made in view of the above-described problems, and can easily and accurately determine whether or not the workpiece has been normally clamped with a simple configuration, and can clamp the workpiece normally. It is an object of the present invention to provide a clamp apparatus and a clamp confirmation method that can specify to some extent what the cause is when it is determined that it cannot be performed.

In order to achieve the above object, a clamp device according to a first aspect of the present invention is a clamp device that clamps a workpiece by opening and closing a clamp member by supplying a working fluid to the fluid pressure cylinder. A pressure measuring means for measuring the pressure of the supplied working fluid, and a determination for determining whether or not the workpiece has been normally clamped based on a change with time of the pressure of the working fluid measured by the pressure measuring means Means.
In order to achieve the above object, the invention according to claim 2 is characterized in that, in the invention according to claim 1, the determination means has a predetermined range from the start of supply of the working fluid to the completion of supply to the fluid pressure cylinder. It is characterized by determining whether or not the work has been normally clamped by determining whether or not the pressure of the working fluid has reached a predetermined pressure over time.
According to a third aspect of the present invention, there is provided a clamp device that clamps a workpiece by opening and closing a clamp member by supplying a working fluid to a fluid pressure cylinder. A clamp confirmation method for determining whether or not a workpiece has been clamped normally, wherein the pressure of a working fluid supplied to a fluid pressure cylinder is measured, and the workpiece is measured based on a change over time of the measured pressure of the working fluid. It is characterized in that it is determined whether or not can be clamped normally.
In order to achieve the above object, the invention related to the clamp confirmation method of the clamp device according to claim 4 is characterized in that, in the invention according to claim 3, it is determined whether or not the workpiece has been normally clamped by operating the hydraulic cylinder. It is characterized in that it is determined whether or not the pressure of the working fluid has reached a predetermined pressure during a predetermined range of time from the start of supply of fluid to the completion of supply.

According to the first aspect of the present invention, when the working fluid is supplied to the fluid pressure cylinder and the clamp member is driven to close and clamp the workpiece, the pressure of the working fluid supplied to the fluid pressure cylinder is measured by the pressure measuring means. The measured pressure of the working fluid rises after the clamp member comes into contact with the workpiece and reaches a predetermined pressure. The determination means determines whether or not the workpiece has been normally clamped based on a change with time of the pressure of the working fluid.
According to a second aspect of the present invention, in the first aspect of the present invention, the determination means measures the time when the pressure of the working fluid reaches a predetermined value (threshold value) set in advance, and this time is determined by the fluid pressure cylinder. It is determined whether or not a predetermined range of time (time from the lower limit to the upper limit) is entered between the start of supply of the working fluid to the end of supply. Then, the determination means determines that the clamp has been normally performed when the measurement time reaching the threshold falls within a predetermined range of time, and if the measurement time does not fall within the predetermined range of time, that is, less than the lower limit time. If it is early or later than the upper limit time, it is determined as abnormal. If the time to reach the threshold value of the working fluid pressure is earlier than the lower limit time when it is determined to be abnormal, for example, chips are sandwiched between the clamp member and the workpiece, or the workpiece is properly clamped. If the cause can be assumed such as not being arranged to be clamped to the member and the time to reach the working fluid pressure threshold is slower than the upper limit time, for example, the fluid pressure cylinder and the working fluid pressure The cause can be assumed such as leakage of piping between the supply source and the workpiece cannot be clamped because the workpiece is not conveyed.
According to a third aspect of the invention, the work fluid is clamped by closing the clamp member by supplying the working fluid to the fluid pressure cylinder. At this time, when the pressure of the working fluid supplied to the fluid pressure cylinder is measured, the measured pressure of the working fluid rises after the clamp member comes into contact with the workpiece and becomes a predetermined pressure. Therefore, it is determined whether or not the workpiece has been normally clamped based on the change over time of the measured pressure of the working fluid.
According to a fourth aspect of the present invention, in the third aspect of the present invention, the time for the pressure of the working fluid to reach a predetermined value (threshold value) set in advance is measured, and this time is taken to the working fluid to the fluid pressure cylinder. Whether or not the workpiece has been clamped normally is determined by whether or not a predetermined range of time (time from the lower limit to the upper limit) is entered between the start of supply and the completion of supply. When the measurement time falls within a predetermined range, it can be determined that the clamp has been normally performed.When the measurement time does not fall within the predetermined range, that is, earlier than the lower limit time or higher than the upper limit time. If it is late, it can be determined as abnormal. If the time to reach the threshold value of the working fluid pressure is earlier than the lower limit time when it is determined to be abnormal, for example, chips are sandwiched between the clamp member and the workpiece, or the workpiece is properly clamped. If the time to reach the working fluid pressure threshold is slower than the upper limit time, for example, the fluid pressure cylinder and the working fluid pressure supply Causes can be assumed, such as leakage of piping between the source and the workpiece is not conveyed and the clamp member cannot be clamped.

According to the first aspect of the present invention, the pressure measuring means and the determining means are provided, and the determination means has clamped the workpiece normally based on the change with time of the pressure of the working fluid measured by the pressure measuring means. Therefore, it is possible to provide a clamping device that has a simple configuration and can easily and accurately determine whether or not the workpiece has been normally clamped in a short time.
According to a second aspect of the present invention, in the first aspect of the present invention, the pressure of the working fluid is a predetermined pressure within a predetermined range of time from the start of supply of the working fluid to the completion of supply to the fluid pressure cylinder. Since it is determined whether or not the workpiece has been clamped normally by determining whether or not the workpiece has been reached, the configuration is simple, and whether or not the workpiece has been clamped normally is simple. It is possible to provide a clamping device that can be determined by time and that can determine to some extent what the cause is when it is determined that the workpiece cannot be clamped normally.
According to the invention of claim 3, the pressure of the working fluid supplied to the fluid pressure cylinder is measured, and it is determined whether or not the workpiece has been normally clamped based on the change over time of the measured pressure of the working fluid. Therefore, it is possible to provide a clamp confirmation method for a clamp device that has a simple configuration and can easily and accurately determine whether or not the workpiece has been normally clamped.
According to the invention of claim 4, in the invention of claim 3, the determination as to whether or not the workpiece has been normally clamped is a predetermined period between the start of supply of the working fluid to the fluid pressure cylinder and the completion of supply. Since it is performed based on whether the pressure of the working fluid has reached a predetermined pressure within a range of time, it is simple in structure, and it is determined in a short time whether the workpiece has been normally clamped easily and accurately. In addition, it is possible to provide a clamp confirmation method for a clamp device that can identify to some extent what the cause is when it is determined that the workpiece cannot be clamped normally.

The best mode for carrying out the clamping apparatus of the present invention will be described in detail with reference to FIGS. In the drawings, the same reference numerals are given to the same or corresponding parts.
The clamping device according to the present invention roughly clamps a workpiece W by opening and closing the clamping member 2 by supplying a working fluid to the fluid pressure cylinder 1, and includes a clamp arm 2 as a clamping member for clamping the workpiece W; The hydraulic cylinder 1 that opens and closes the clamp arm 2, the working fluid supply source 3 that supplies the working fluid to the fluid pressure cylinder 1, and the pressure of the working fluid that is supplied from the working fluid supply source 3 to the fluid pressure cylinder 1 The pressure measuring means 4 for measuring P and the control means 5 for controlling based on the pressure P of the working fluid measured by the pressure measuring means 4 are provided. Determination means 6 for determining whether or not the workpiece W has been normally clamped based on the change with time of the pressure P of the working fluid measured by the method, and a predetermined sequential control And a programmable logic controller (PLC) 7 for determining the pressure of the working fluid P during a predetermined range ab from the start of supply of the working fluid to the completion of supply to the fluid pressure cylinder 1. It is determined whether or not the workpiece W has been clamped normally by determining whether or not has reached a predetermined pressure P1.

  As shown in FIG. 1, in this embodiment, the workpiece W is conveyed on the rail 10, stopped at a predetermined position, and predetermined processing is performed. The clamping device according to this embodiment is configured such that one end of the clamp arm 2 is brought into contact with and clamps the work W conveyed, and a bracket 11 that rotatably supports an intermediate portion of the clamp arm 2; And a hydraulic cylinder 1 as a fluid pressure cylinder having a piston rod 15 connected to the other end of the clamp arm 2. The hydraulic cylinder 1 is configured such that a hydraulic supply source 3 such as a hydraulic pump is connected by a pipe line 17 via a switching valve 16 and its piston rod 15 is driven to be extendable / retractable. Therefore, in this embodiment, when the piston rod 15 of the hydraulic cylinder 1 is driven to extend, one end of the clamp arm 2 is clamped so as to press the work W. The clamping device is not limited to this embodiment. For example, the fluid pressure cylinder 1 can adopt an air cylinder instead of the hydraulic cylinder, or can clamp a pallet holding the workpiece W. In addition, the present invention can be applied as long as it is driven by supplying a working fluid to the fluid pressure cylinder 1, such as one that opens and closes a pair of clamp arms.

The pressure measuring means 4 is constituted by a pressure sensor such as a hydraulic gauge interposed in a pipe line 17 between the hydraulic cylinder 1 and the switching valve 16.
The determination unit 6 of the control unit 5 includes an A / D converter 8 that converts an analog hydraulic signal output from the pressure sensor 4 into a digital signal, and a calculation unit 9 that performs a calculation according to the procedure described below. .

Here, based on FIGS. 2-4, the clamp confirmation method of the clamp apparatus of this invention is demonstrated below with the control content of the clamp apparatus comprised as mentioned above.
When the workpiece W is conveyed on the rail 10 and stopped at a predetermined position, a clamp command (ON) is automatically or manually output from the PLC 7 to the switching valve 16 (S1 in FIG. 4), and the hydraulic pressure supply source 3, hydraulic oil is supplied to the hydraulic cylinder 1, the piston rod 15 of the hydraulic cylinder 1 is driven to extend, and the clamp arm 2 starts clamping the workpiece W. At this time, the hydraulic sensor 4 measures the hydraulic pressure P of the hydraulic oil supplied to the hydraulic cylinder 1 and outputs an analog hydraulic signal corresponding to the pressure P. In the A / D converter 8, the analog hydraulic signal is converted into a digital signal and output to the arithmetic unit 9. Further, a clamp command (ON) signal from the PLC 7 is also output to the determination means 6.

The calculation unit 9 includes a pressure (threshold value) P1 when one end of the clamp arm 2 is actually in contact with the workpiece W and starts clamping, and a pressure when the clamp arm 2 actually completes clamping the workpiece W. A predetermined range of time (lower limit time a, upper limit time b) is set in P2 and the time T from the start of supply of hydraulic oil to the hydraulic cylinder 1 until the clamping is completed. It is input and stored via an input device such as a keyboard.
The calculation unit 9 measures an arrival time t from when the clamp command is turned on until the value of the pressure P output from the pressure sensor 4 reaches the pressure P1, which is a threshold value (see FIG. 4). S2), it is determined whether the measured arrival time t is later than the set lower limit time a (S3 in FIG. 4). When the arrival time t is before the lower limit time a (in the case of NO in S3 of FIG. 4, that is, when a ≧ t), as shown in FIG. )), The clamping has been started earlier. For example, chips are sandwiched between the clamp arm 2 and the workpiece W, or the workpiece W is properly clamped to the clamp arm 2. It can be assumed that the cause is a clamp abnormality. Therefore, the determination unit 6 outputs a clamp abnormality signal and causes the control unit 5 to take a countermeasure such as issuing a warning or stopping the operation of the entire facility (S7 in FIG. 4).

  If the measured arrival time t is later than the set lower limit time a (if YES in S3 of FIG. 4, that is, if a <t), then the measured arrival time t is set. It is determined whether it is earlier than the upper limit time b (S4 in FIG. 4). When the time t for reaching the threshold value P1 of the pressure P of the working fluid is later than the upper limit time b, for example, the leakage of the pipe 17 between the hydraulic cylinder 1 and the working fluid pressure supply source 3 or the workpiece W is predetermined. The cause can be assumed, for example, the clamp arm 2 cannot be clamped without being conveyed to the position. Therefore, the determination unit 6 outputs an abnormal pressure signal and causes the control unit 5 to take a countermeasure such as issuing a warning or stopping the operation of the entire facility (S8 in FIG. 4).

On the other hand, if YES (a <t> can be determined in S3 of FIG. 4 and YES (t <b) can be determined in S4 of FIG. 4, that is, the measured arrival time t is the lower limit time a and the upper limit time. 3), it can be determined that the workpiece W can be clamped in a normal state as shown in FIG. Therefore, subsequently, it is determined whether or not the pressure P has reached the set value P2 (S5 in FIG. 4). If not (NO), the hydraulic cylinder 1 is maintained until the pressure P reaches P2. The supply of hydraulic oil to the engine is continued, and it is repeatedly determined whether the pressure P has reached the set value P2. When it is determined that the pressure P has reached the set value P2 (in the case of YES in S5 in FIG. 4), the clamping is completed (S6 in FIG. 4), and predetermined machining for the clamped workpiece W is started. Is possible. Note that the pressure P2 for determining the completion of clamping is not necessarily set to the highest pressure as long as the clamping force sufficient to process the workpiece W can be obtained.
After performing predetermined machining on the workpiece W, the control means 5 outputs a clamp release signal to the PLC 7 to control the switching valve 16 so that the piston rod 15 of the hydraulic cylinder 1 is retracted.

  In the present invention, since there is no need to provide switches in the vicinity of the clamp arm 2 and the hydraulic cylinder 1 as in the prior art, the equipment cost can be reduced, and the time measured by the pressure sensor 4 can be reduced. The clamp can be confirmed accurately and in a short time only by inputting a simple program for determining based on the change to the determining means 6. In addition, even when the workpiece W is cut, it is not affected by supply of coolant necessary for cutting or generation of chips, and the clamp of the workpiece W can be confirmed stably. be able to. Furthermore, in the present invention, even if an abnormality occurs, the cause can be assumed to some extent, so that it is easy to deal with the above.

It is the block diagram shown in order to demonstrate one Embodiment of the clamp apparatus of this invention. It is the ladder figure shown in order to demonstrate control of the clamp device of the present invention. It is a graph which shows the relationship between the measured pressure and time which showed the normal state and the state which abnormality generate | occur | produced, in order to demonstrate the clamp confirmation method of the clamp apparatus of this invention. It is the flowchart which showed the control content in order to demonstrate the clamp confirmation method of the clamp apparatus of this invention.

Explanation of symbols

W: Workpiece, 1: Hydraulic cylinder (fluid pressure cylinder), 2: Clamp arm (clamp member), 3: Hydraulic pump (working fluid supply source), 4 Pressure sensor (pressure measuring means), 5: Control means, 6: Judgment means, 7: PLC, 8: A / D converter, 9: calculation unit, P: pressure of hydraulic oil (working fluid), P1: clamp start pressure (threshold), P2: clamp completion pressure, a: Lower limit time, b: upper limit time, t: threshold arrival time

Claims (4)

A clamping device that clamps a workpiece by driving a clamp member to open and close by supplying a working fluid to a fluid pressure cylinder,
Pressure measuring means for measuring the pressure of the working fluid supplied to the fluid pressure cylinder;
Determination means for determining whether or not the workpiece has been normally clamped based on a change with time of the pressure of the working fluid measured by the pressure measuring means;
A clamping device comprising: The determination means normally clamps the workpiece by determining whether or not the pressure of the working fluid has reached a predetermined pressure during a predetermined range of time from the start of supply of the working fluid to the completion of supply to the fluid pressure cylinder. The clamping device according to claim 1, wherein it is determined whether or not it has been performed. In a clamp device that clamps a work by driving a clamp member to open and close by supplying a working fluid to a fluid pressure cylinder, a clamp confirmation method for determining whether or not the work has been normally clamped,
Measure the pressure of the working fluid supplied to the fluid pressure cylinder,
A clamp confirmation method for a clamp device, characterized in that it is determined whether or not the workpiece has been normally clamped based on the measured change in pressure of the working fluid over time. Whether or not the workpiece has been clamped normally is determined by whether or not the working fluid pressure has reached a predetermined pressure within a predetermined range of time from the start of supply of the working fluid to the fluid pressure cylinder until the completion of the supply. The clamp confirmation method for a clamp device according to claim 3, wherein:

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