JPWO2020171172A1 - Work gripping start point detection method, work gripping start point detection device and work gripping method in hydraulic clamp device, hydraulic clamp device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic clamping device capable of finding a work gripping start point for each work whose dimensions vary within a tolerance. SOLUTION: A hydraulic clamp device has a first peripheral surface, an outer peripheral surface 16A, and a second peripheral surface, in a portion where a main body 12 which is a first member and a cylindrical body 24 which is a second member overlap each other. The working liquid chamber 30 is defined by a recess 28 provided in at least one of the inner peripheral surfaces 24B which is a surface, and the cylindrical body 24 is elastically deformed by the pressure of the working liquid sealed in the working liquid chamber 30 to be covered. Clamp the clamp member W1. The hydraulic clamping device includes an arithmetic device that calculates a work gripping start point at which the clamped member W1 is started to be clamped by the cylindrical body 24. [Selection diagram] Fig. 1

Description

The present invention relates to a hydraulic clamping device that clamps (hereinafter, also referred to as gripping) a member to be clamped, which is used in the fields of machining and measurement, by applying pressure to a working liquid.

The hydraulic clamp device includes a main body including a thin-walled tubular portion that defines a working liquid chamber, and a pressurizing portion that is provided in the main body and pressurizes the working liquid that is sealed in the working liquid chamber. It is known that a thin-walled tubular portion clamps a member to be clamped (hereinafter, also referred to as a work) by elastically deforming in the radial direction by applying pressure to the working liquid sealed in the working liquid chamber (hereinafter, also referred to as a work). For example, see Patent Documents 1 to 3).

The expansion (or contraction) operation method of the hydraulic clamp device is roughly classified into manual and automatic (power). In the manual operation method, the thin-walled tubular portion is expanded (or contracted) by applying pressure to the working liquid by rotating the working screw of the hydraulic clamping device. In the power operation method, the piston rod of the hydraulic clamp device is pushed by a power cylinder or the like to apply pressure to the working liquid to expand (or contract) the thin-walled tubular portion.

Jitsukosho 58-21605 Gazette Jikkenhei 6-36709 Gazette Japanese Unexamined Patent Publication No. 2007-50478

The workpieces clamped by the conventional hydraulic clamping device are generally manufactured within the specified tolerance range, and therefore the actual dimensions of the clamp portion vary within the specified tolerance range.

Conventionally, for a work whose dimensions vary within the tolerance, a method of detecting a work gripping start point (zero point) where the work comes into contact with the expansion (or contraction) part of the thin-walled tubular part of the hydraulic clamp device. It is possible to control the gripping force generated when the thin-walled tubular part of the hydraulic clamping device expands (or contracts) and comes into contact with the work, and then further applies pressure to the working liquid. There wasn't. As a result, the gripping force is low for the work having the upper limit value of the tolerance, and is high for the work having the lower limit value of the tolerance.

Here, the gripping force will be described. In the hydraulic clamp device, the thin-walled cylindrical portion (expanded portion) is elastically deformed in the radial direction by applying pressure to the working liquid sealed in the working liquid chamber.

Since the work is fitted with the expanding portion of the hydraulic clamping device with a gap, when the expanding portion of the hydraulic clamping device is expanded, it comes into contact with the inner diameter (or outer diameter) of the member to be clamped. When pressure is applied to the working liquid after contact, the thin-walled cylindrical portion is less likely to undergo elastic deformation due to the wall thickness of the contacted work. As a method of applying pressure to the working liquid, there is a method of pushing the working liquid sealed in the working liquid chamber by a piston or the like. There is a difference between the pressure that expands the integrated state due to the increased thickness, and the difference in the pressure value becomes the gripping force that grips the work.

That is, when the work is clamped by using the hydraulic clamping device, the piston or the like is operated (pushed) in order to apply pressure to the working liquid. When the operating amount at this time is a constant amount (= pushing stroke), the work with the upper limit value within the tolerance has a small gripping force (= the deformation is small), and the work with the lower limit value within the tolerance has a large gripping force. (The deformation becomes large). Therefore, when the workpiece is machined and measured with high accuracy, the influence of such deformation becomes a problem.
The form described above is a case where the hydraulic clamping device expands to clamp the work, and when the hydraulic clamping device contracts to clamp the work, the relationship between the tolerance of the work and the gripping force is opposite. However, their characteristics are the same. Hereinafter, the operation when the hydraulic clamp device is expanded to grip the work will be described.

An object to be solved by the present invention is to provide a hydraulic clamping device capable of finding a work gripping start point for each member to be clamped having varying dimensions.

(1) In order to achieve such a problem, the hydraulic clamping device according to one embodiment of the present invention includes a first member having a first peripheral surface forming an outer peripheral surface or an inner peripheral surface, and the first member. The first member has a second member having a second peripheral surface forming an inner peripheral surface or an outer peripheral surface that overlaps the peripheral surface of the first member, and the first member and the second member overlap each other. The working liquid chamber is defined by a recess provided on at least one of the peripheral surface and the second peripheral surface, and the second member is elastically deformed by the pressure of the working liquid sealed in the working liquid chamber. , A hydraulic clamping device for clamping a member to be clamped, a pressure measuring device for measuring the pressure of the working liquid sealed in the working liquid chamber, and the working liquid chamber formed in the first member. A drive device including a communicating piston chamber, a piston rod for driving the piston provided in the piston chamber, and a calculation device for calculating a work gripping start point at which the second member starts clamping the member to be clamped. The computing device calculates the work gripping start point based on the pressure of the working liquid measured by the pressure measuring device and the measurement data of the stroke of the piston rod.

According to this configuration, the work gripping start point at which the clamped member starts to be clamped by the second member is calculated based on the pressure of the working liquid measured by the pressure measuring device and the measurement data of the stroke of the piston rod. By providing the arithmetic device, it becomes possible to find the work gripping start point for each member to be clamped whose dimensions vary within the tolerance. The computing device can calculate the gripping start point based on the pressure of the working liquid measured by the pressure measuring means and the measurement data of the stroke of the piston rod.

(2) In the hydraulic clamping device, preferably, the arithmetic device deforms the second member elastically based on measurement data showing the relationship between the pressure of the working liquid and the stroke of the piston rod. Two points in the first section from the start to the lower limit of the tolerance of the member to be clamped, and a second point from the point where the second member becomes the same as the upper limit of the tolerance of the member to be clamped to the most elastic deformation. Straight line data is created at each of the two points in the section, and the intersection of these two straight lines is set as the work gripping start point.

According to this configuration, the two points in the first section from the start of elastic deformation of the second member to the lower limit of the tolerance of the member to be clamped and the second member are the same as the upper limit of the tolerance of the member to be clamped. By creating straight line data at each of the two points in the second section from the point to the most elastic deformation and using the intersection of these two straight lines as the work gripping start point, it is possible to accurately calculate the work gripping start point. can.

(3) The hydraulic clamp device preferably starts the second member to elastically deform the measurement data showing the relationship between the pressure of the working liquid and the stroke of the piston rod. In each section of the first section from the time to the lower limit of the tolerance of the member to be clamped, and the second section from the point where the second member becomes the same as the upper limit of the tolerance of the member to be clamped to the most elastic deformation. Each straight line data is calculated by the straight line regression method, and the intersection of these two straight lines is set as the work gripping start point.

According to this configuration, the measurement data showing the relationship between the pressure of the working liquid and the stroke of the piston rod is obtained in the first section from the start of elastic deformation of the second member to the lower limit of the intersection of the member to be clamped. The straight line data is calculated by the linear regression method in each section of the second section from the point where the second member becomes the same as the upper limit of the tolerance of the member to be clamped to the most elastic deformation, and the intersection of these two straight lines. By setting the work gripping start point as, the work gripping start point can be accurately calculated.

(4) In the hydraulic clamp device, preferably, in the arithmetic device, the pressure of the working liquid and the stroke of the piston rod are correlated by a linear function after the second member starts elastic deformation. The point at which the pressure increase rate in the working liquid chamber of the measurement data showing the relationship changes is defined as the work gripping start point.

According to this configuration, after the second member starts elastic deformation, the point where the pressure increase rate in the working liquid chamber of the measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod has changed is the work. Since the gripping start point is used, the work gripping start point can be accurately calculated.

(5) The hydraulic clamping device preferably includes the pressure of the working liquid in the section from the start of elastic deformation of the second member to the lower limit of the tolerance of the clamped member. When the piston rod is stroked until the elastic deformation of the second member is maximized with respect to the first inclination of the measurement data showing the correlation between the stroke of the piston rod and the linear function, the linear function is used. The point at which the second inclination of the measurement data showing the correlation changes to be greater than or equal to the first inclination is defined as the work gripping start point.

According to this configuration, the measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod in the section from the start of elastic deformation of the second member to the lower limit of the tolerance of the member to be clamped by a linear function. The second inclination of the measurement data showing the correlation by the linear function when the piston rod is stroked until the elastic deformation of the second member is maximized with respect to the first inclination of the first inclination is the first inclination. Since the point changed as described above is set as the work gripping start point, the work gripping start point can be accurately calculated.

(6) The hydraulic clamping device is preferably a section from the start of elastic deformation of the second member to the most elastic deformation of the arithmetic device in a state where the clamped member is not attached. In the first measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod by a linear function, and the clamped member, the second member is the clamped member. Linear data is calculated from the second measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod by the linear function in the section from the point where it becomes the same as the upper limit of the tolerance of the above to the most elastic deformation. Then, the intersection of these two straight lines is set as the work gripping start point.

According to this configuration, the pressure of the working liquid and the stroke of the piston rod are primary in the section from the start of elastic deformation of the second member to the most elastic deformation in the state where the member to be clamped is not attached. The first measurement data showing the correlation by the function and the working liquid in the section from the point where the second member becomes the same as the upper limit of the tolerance of the clamped member to the most elastic deformation with the clamped member attached. Linear data is calculated from the second measurement data showing the correlation between the pressure of the piston rod and the stroke of the piston rod by a linear function, and the intersection of these two straight lines is set as the work gripping start point. Can be calculated accurately.

(7) The hydraulic clamping device is preferably a section from the start of elastic deformation of the second member to the most elastic deformation of the arithmetic device in a state where the clamped member is not attached. The maximum stroke of the piston rod with the clamped member attached to the inclination of the first measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod by a linear function. The point at which the inclination of the second measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod when the stroke is made to the above is changed to be greater than or equal to the inclination of the first measurement data. It is used as the work gripping start point.

According to this configuration, the pressure of the working liquid and the stroke of the piston rod are primary in the section from the start of elastic deformation of the second member to the most elastic deformation in the state where the member to be clamped is not attached. With respect to the inclination of the first measurement data showing the correlation by the function, the pressure of the working liquid and the stroke of the piston rod when the piston rod is stroked to the maximum stroke with the member to be clamped attached are 1. Since the work gripping start point is defined as the point where the inclination of the second measurement data showing the correlation by the next function changes to be equal to or greater than the inclination of the first measurement data, the work gripping start point can be accurately calculated. ..

(8) The hydraulic clamping device preferably elastically deforms the second member with reference to the work gripping start point, and obtains a predetermined gripping force with respect to the clamped member. A gripping force control device for controlling the pressure of the above is further provided.

According to this configuration, a gripping force control device that elastically deforms the second member with reference to the work gripping start point and controls the pressure of the working liquid so as to obtain a predetermined gripping force with respect to the clamped member is further provided. Therefore, the gripping force with respect to the member to be clamped can be set to a predetermined value. As a result, it becomes possible to clamp each member to be clamped whose dimensions vary within the tolerance with the same amount of gripping force.

(9) The hydraulic clamping device preferably has a first member having a first peripheral surface forming an outer peripheral surface or an inner peripheral surface, and an inner peripheral surface or an outer peripheral surface that overlaps the first peripheral surface. It has a second member having a second peripheral surface to form, and at least the first peripheral surface and the second peripheral surface at a portion where the first member and the second member overlap each other. A hydraulic clamping device that clamps a member to be clamped by defining a working liquid chamber by a recess provided on one side and elastically deforming the second member by the pressure of the working liquid sealed in the working liquid chamber. Therefore, the arithmetic device for calculating the work gripping start point at which the second member starts clamping the member to be clamped, and the second member are elastically deformed with reference to the work gripping start point, and the subject is covered. It is provided with a gripping force control device that controls the pressure of the working liquid so that a predetermined gripping force can be obtained with respect to the clamp member.

According to this configuration, a gripping force control device that elastically deforms the second member with reference to the work gripping start point and controls the pressure of the working liquid so as to obtain a predetermined gripping force with respect to the clamped member is further provided. Therefore, the gripping force with respect to the member to be clamped can be set to a predetermined value. As a result, it becomes possible to clamp each member to be clamped whose dimensions vary within the tolerance with the same amount of gripping force.

(10) In the work gripping start point detection method in the hydraulic clamping device according to one embodiment of the present invention, a clamp member provided with a working liquid chamber inside and a working liquid filled in the working liquid chamber are pressurized. The clamp member includes a piston, and has a wall body that defines the working liquid chamber on the inner surface side and the clamping surface on the outer surface side, and the wall is pressurized by the pressurization of the working liquid by the movement of the piston. When the clamp surface starts to come into contact with the clamped member in the hydraulic clamping device that clamps the clamped member by elastically deforming the body and pressing the clamped surface against the clamped member. This is a method of detecting the work gripping start point, which is based on the pressure change of the working liquid with respect to the moving position of the piston.

According to this method, the work gripping start point can be accurately detected.

(11) The work gripping start point is a time point at which the pressure rise rate of the working liquid with respect to the moving position of the piston changes with the clamped member attached to the hydraulic clamping device.

According to this method, the work gripping start point can be accurately detected.

(12) In the work gripping start point detecting method, preferably, the moving position of the piston and the pressure of the working liquid in the moving section of the piston, which is estimated that the clamp surface does not abut against the clamped member. According to an equation showing the relationship between the piston and the moving position of the piston in the moving section of the piston estimated that the clamp surface comes into contact with the member to be clamped, and an equation showing the relationship between the pressure of the working liquid and the pressure of the working liquid. The solution of the simultaneous equations is set as the work gripping start point.

According to this method, the work gripping start point can be accurately detected.

(13) The work gripping start point detection method preferably includes a pressure change of the working liquid with respect to a moving position of the piston in a state where the clamped member is not attached to the hydraulic clamping device, and the hydraulic clamping device. The work gripping start point is detected from the pressure change of the working liquid with respect to the moving position of the piston in the state where the clamped member is attached.

According to this method, the work gripping start point can be accurately detected.

(14) The work gripping start point detecting method preferably detects the pressure of the working liquid by a pressure sensor.

According to this method, the pressure of the working liquid required to detect the work gripping start point is accurately detected.

The work gripping start point detection method preferably detects the pressure of the working liquid from the measured value by the load cell that detects the load acting on the piston.

According to this method, the pressure of the working liquid required to detect the work gripping start point is detected from the outside.

(16) The work gripping start point detecting device in the hydraulic clamping device includes a clamping member provided with a working liquid chamber inside, and a piston for pressurizing the working liquid filled in the working liquid chamber, and the clamping member. Has a wall body that defines the working liquid chamber on the inner surface side and a clamp surface on the outer surface side, and the wall body is elastically deformed by pressurization of the working liquid by the movement of the piston, and the clamp In the hydraulic clamping device that clamps the clamped member by pressing the surface against the clamped member, the work gripping start point at the time when the clamped surface starts abutting against the clamped member is detected. The work gripping start point is detected based on the pressure change of the working liquid with respect to the moving position of the piston.

According to this configuration, the work gripping start point can be accurately detected.

(17) The work gripping method according to one embodiment of the present invention determines the moving position of the piston or the pressure of the working liquid at the work gripping start point detected by the work gripping start point detecting method in the hydraulic clamp device. The gripping force of the member to be clamped is set as a reference.

According to this method, even if the clamped member has a variation in dimensions, the clamped member can be gripped with a required gripping force.

(18) In the work gripping method using the hydraulic clamp device, the hydraulic clamp device preferably moves by screwing a first piston that moves by pressing from the outside and an operating screw member provided on the clamp member. The work gripping start point is detected by the movement of the first piston, and the work subject is detected by the movement of the second piston with reference to the pressure of the working liquid that has detected the work gripping start point. Set the gripping force of the clamp member.

According to this method, the member to be clamped can be gripped with a required gripping force by the outer setup.

According to the hydraulic clamping device according to the present invention, it is possible to find a work gripping start point for each member to be clamped whose dimensions vary.

Longitudinal sectional view showing the first embodiment of the hydraulic clamp device according to the present invention. A vertical sectional view showing a main part of the hydraulic clamp device according to the first embodiment. The block diagram which shows the control circuit of the hydraulic clamp device which concerns on Embodiment 1. A flowchart showing the operation of the control unit of FIG. A graph showing the relationship between the stroke (position) of the piston rod and the hydraulic pressure (pressure) in the hydraulic clamp device according to the first embodiment. A graph showing an example of calculating a work gripping start point based on measurement data in the first embodiment. A flowchart showing another example of calculating the work gripping start point based on the measurement data in the first embodiment. The block diagram which shows the control circuit of the hydraulic clamp device which concerns on Embodiment 2 of this invention. Longitudinal sectional view of the hydraulic clamp device according to the third embodiment of the present invention. Front view of the outer setup device used for carrying out the work gripping start point detection method and the work gripping method according to the present invention. Side view showing the mounting state of the hydraulic clamp device according to the third embodiment with respect to the machine tool. Longitudinal sectional view of the hydraulic clamp device according to the fourth embodiment of the present invention. Longitudinal sectional view of the hydraulic clamp device according to the fifth embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.

[Embodiment 1]
Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 5.

As shown in FIG. 1, the hydraulic clamp portion 10 is of the mandrel type and has a main body (first member) 12. The main body 12 includes a rod-shaped portion (mandrel) 22 made of a round bar having a first axial portion 16, a flange portion 18, and a second axial portion 20 on the same axis in order in the axial direction. The first shaft-shaped portion 16 and the second shaft-shaped portion 20 have the same outer diameter. The flange portion 18 has an outer diameter larger than that of the first axial portion 16 and the second axial portion 20, and extends outward in the radial direction with respect to the first axial portion 16 and the second axial portion 20. It is formed.

A cylindrical body (second member) 24 forming a thin-walled wall body is fitted on the outer periphery of the first shaft-shaped portion 16. The cylindrical body 24 is a cylindrical wall body that defines a working liquid chamber 30 described later on the inner surface side and a clamp surface on the outer surface side, and is an outer peripheral surface (clamp) that clamps the cylindrical member to be clamped W1. A surface) 24A and an inner peripheral surface (second peripheral surface) 24B that overlaps the outer peripheral surface (first peripheral surface) 16A of the first axial portion 16 are provided.

A peripheral groove-shaped recess 28 is formed on the outer peripheral surface 16A of the first shaft-shaped portion 16. A cross-sectional shape (a cross section orthogonal to the central axis) extending between the first axial portion 16 and the cylindrical body 24 over the entire circumference of the outer peripheral surface 16A of the first axial portion 16 by a recess 28. An annular working liquid chamber 30 is defined.

Thus, the cylindrical body 24 defines the working liquid chamber 30 on the inner surface side and the clamp surface (outer peripheral surface 24A) on the outer surface side.

On the outer peripheral surface 16A of the first axial portion 16, O-rings 32 for ensuring the liquidtightness of the working liquid chamber 30 are mounted on both sides of the working liquid chamber 30 in the axial direction. The cylindrical body 24 may be liquidtightly joined to the first axial portion 16 by brazing or the like. In this case, the O-ring 32 becomes unnecessary.

The rod-shaped portion 22 has a piston chamber 34 extending in the axial direction along the central axis along the first axial portion 16. A piston 36 is fitted in the piston chamber 34 so as to be movable in the axial direction. One end of the piston chamber 34 communicates with the working liquid chamber 30 through an axial passage 38 and a plurality of radial passages 40 formed in the first axial portion 16.

The chamber space on the passage 38 side of the piston chamber 34 separated by the piston 36, the passages 38 and 40, and the working liquid chamber 30 form one closed space, and the closed space is filled with hydraulic oil which is a working liquid. Has been done.

A bush 42 is screwed to the second shaft-shaped portion 20 of the main body 12. The bush 42 is formed with a through hole 42A penetrating in the axial direction of the central portion. A push rod 44 is movably engaged with the through hole 42A in the axial direction. The axial movement of the push rod 44 is transmitted to the piston 36 via the steel ball 48.

The hydraulic clamp portion 10 is provided with a power cylinder portion 46, which is an example of a drive device, on the same axis as the push rod 44. The power cylinder unit 46 is a drive device including a piston rod 47 for driving the piston 36, and controls the stroke of the piston rod 47 by a control signal to the power cylinder unit 46. When the piston rod 47 moves to the right as seen in FIG. 1 by the above control signal, the push rod 44, the steel ball 48, and the piston 36 move in the same direction to pressurize the hydraulic oil in the working liquid chamber 30. As a result, the pressure in the working liquid chamber 30 is quantitatively pressure-controlled according to the stroke of the piston rod 47.

As the power cylinder unit 46, a hydraulic cylinder, a pneumatic cylinder, a hydraulic servo cylinder, an electric cylinder using a motor and a ball screw, or the like is generally used.

In the present embodiment, the pressurization of the hydraulic oil in the hydraulic fluid chamber 30 can be mechanized and automated by using the power cylinder unit 46.

In this way, the pressure structure of the piston rod 47 is configured, and the movement of the push rod 44 causes the piston 36 to move the piston chamber 34 to the passage 38 side (on the right side when viewed in FIG. 1). As a result, the hydraulic oil in the hydraulic fluid chamber 30 is pressurized, and the cylindrical body 24 is elastically deformed in the radial direction due to this pressurization, thereby expanding and deforming in the radial direction.

As a result, on the outer peripheral surface 24A of the cylindrical body 24, the outer peripheral surface 24A comes into contact with the inner peripheral surface of the central hole A of the clamped member (work) W1 under the enlarged diameter deformation of the cylindrical body 24. By being pressed against the inner peripheral surface, the member to be clamped W1 is clamped. More specifically, the member to be clamped W1 has a central hole A fitted to the outer periphery of the cylindrical body 24, and the cylindrical body is formed on the inner peripheral surface of the central hole A due to the enlarged diameter deformation of the cylindrical body 24. The outer peripheral surface 24A of the 24 is brought into close contact with the hydraulic clamp portion 10 to be gripped (clamped).

As described above, the hydraulic clamp portion 10 of the first embodiment controls and clamps the force for clamping the cylindrical member to be clamped W1.

A pressure sensor device (pressure measuring device) 60 is attached to the end surface 16B of the first shaft-shaped portion 16. As shown in FIG. 2, the pressure sensor device 60 includes a flange portion 62, a male screw portion 64 extending from the flange portion 62 to one side, and a hexagonal portion formed in order on the other side of the flange portion 62. It has 66, a housing 68, and a cap portion 70 attached to the free end (tip) of the housing 68.

The housing 68 is provided with a hydraulic pressure measuring unit (pressure measuring device) 72 including a pressure measuring element (not shown) and a circuit board in a state of being sealed with oil 69. The male threaded portion 64, the flange portion 62, and the hexagonal portion 66 are formed with a pressure introduction passage 74 that is opened at the tip of the male threaded portion 64 to guide the pressure to be measured to the hydraulic pressure measuring unit 72.

Since the hydraulic pressure measuring unit 72 is sealed with the oil 69, the insulation reliability of the hydraulic pressure measuring unit 72 is improved and it is less likely to be affected by the external environment, and the hydraulic pressure measuring unit 72 makes stable pressure measurement. Becomes possible.

The cap unit 70 outputs a signal indicating the pressure measured by the hydraulic pressure measuring unit 72 to the outside, and in the present embodiment, to a wireless reader 90 (see FIG. 1) arranged in the vicinity of the hydraulic clamping unit 10. It has a wireless communication unit 76 and a power receiving unit 78 that wirelessly receives power for the pressure sensor device 60 from the outside, and in the present embodiment, from the wireless reader 90 described above. The power receiving unit 78 is fed from the outside by a known electromagnetic induction or a radio wave in which an electric field and a magnetic field change from a wireless reader 90 using a built-in antenna (not shown) in a non-contact manner, and the hydraulic pressure measuring unit 72 And power is supplied to the wireless communication unit 76.

A radial bottomed screw hole 80 opened in the end surface 16B is formed in the first axial portion 16. The pressure sensor device 60 is fixed to the end surface 16B of the first shaft-shaped portion 16 by screw-engaging the male screw portion 64 with the screw hole 80.

As shown in FIG. 2, an annular concave groove 65 is formed on the male threaded portion 64 side of the flange portion 62. An annular rubber packing 67 is attached to the concave groove 65. The rubber packing 67 is elastically deformed by the male screw portion 64 being screw-engaged with the screw hole 80 and pressed against the end surface 16B of the first shaft-shaped portion 16, and is pressed against the first shaft-shaped portion 16 and the pressure sensor device 60. Perform a liquidtight seal between.

As shown in FIG. 1, the first axial portion 16 is formed with a passage 82 communicating with the screw hole 80 in the axial direction. The passage 82 communicates with the axial passage 38 and the plurality of radial passages 40 formed in the first axial portion 16.

The screw holes 80, passages 82, 40, and 38 are filled with hydraulic oil similar to that in the closed space as an expansion portion of the above-mentioned closed space, and these screw holes 80, passages 82, 40, and 38 are the working liquid chambers. The pressure of 30 is guided to the hydraulic pressure measuring unit 72. As a result, the same pressure as the pressure (hydraulic pressure) of the hydraulic oil in the hydraulic fluid chamber 30 acts on the hydraulic pressure measuring unit 72, and the hydraulic pressure measuring unit 72 measures the hydraulic pressure in the hydraulic fluid chamber 30.

To measure the hydraulic pressure in the working liquid chamber 30, a handy type wireless reader 90 is brought close to the pressure sensor device 60 of the hydraulic clamp portion 10 and started by pressing the measurement button 92 of the wireless reader 90. Will be done. When the measurement button 92 is pressed, the power receiving unit 78 of the pressure sensor device 60 is supplied with power from the wireless reader 90 in a non-contact manner, and the power receiving unit 78 supplies power to the hydraulic pressure measuring unit 72 and the wireless communication unit 76. .. As a result, the hydraulic pressure measuring unit 72 and the wireless communication unit 76 are activated, the hydraulic pressure measuring unit 72 measures the hydraulic pressure in the working liquid chamber 30, and the wireless communication unit 76 is measured by the hydraulic pressure measuring unit 72. The signal (radio wave) indicated by the hydraulic pressure is output to the outside. When the wireless reader 90 receives the radio wave output by the wireless communication unit 76, the hydraulic pressure of the working liquid chamber 30 is displayed on the display unit 94 of the wireless reader 90.

As a result, it is not necessary to replace the battery in the pressure sensor device 60 or connect the lead wire to the pressure sensor device 60, and the hydraulic pressure in the working liquid chamber 30 can be measured with good workability. Will come to be.

Although the example using the wireless reader 90 has been described in this embodiment, the measured value of the hydraulic pressure does not change even if the internal pressure measured by using the wired pressure sensor is transmitted to the outside.

Next, the control circuit of this embodiment will be described.

FIG. 3 is a block diagram showing a control circuit of the hydraulic clamp device according to the first embodiment. FIG. 4 is a flowchart showing the operation of the control unit of FIG. FIG. 5 is a graph showing the relationship between the stroke (position) of the piston rod 47 pushing the piston 36 and the hydraulic pressure (pressure) of the working liquid chamber 30 in the hydraulic clamping device according to the first embodiment.

Here, the operating characteristics of the hydraulic clamp portion 10 will be described.
That is, the following (1), (2), and (3) are known as the operating characteristics of the hydraulic clamp device.
(1) The amount of movement of the piston rod 47 for pressurizing the working liquid (= stroke of the piston rod 47) and the pressure of the working liquid are generally correlated by a linear function.
(2) The pressure of the working liquid and the expansion amount of the cylindrical body 24 of the hydraulic clamp portion 10 are generally correlated by a linear function.
(3) The relationship between the diameter of the cylindrical body 24 of the hydraulic clamp portion 10 and the stroke of the piston rod 47 can be obtained from the above correlation. Therefore, the stroke or hydraulic pressure of the piston rod 47 having the same diameter as the upper and lower diameters of the upper and lower limits of the tolerance of the clamped portion of the target member W1 to be clamped can be grasped as an eigenvalue of the hydraulic clamp portion 10. Is. This eigenvalue can be obtained either by actually measuring the diameter of the cylindrical body 24 of the hydraulic clamp portion 10 or by calculating from the design value of the hydraulic clamp portion 10.

As shown in FIG. 3, the control circuit of the hydraulic clamp device has a control unit 50. The control unit 50 inputs pressure measurement data from the hydraulic pressure measurement unit 72 of the pressure sensor device 60 in the hydraulic clamp unit 10, and also inputs measurement data of the stroke of the piston rod 47 from the power cylinder unit 46.

The control unit 50 includes a microcomputer and the like, and has an arithmetic unit (arithmetic unit) 52 and a gripping force control unit 54 as a gripping force control device.

The calculation unit 52 calculates the work gripping start point at which the clamped member W1 is started to be clamped by the cylindrical body 24. The work gripping start point referred to here corresponds to the zero point of the work clamp, and is the time when the outer peripheral surface 24A of the cylindrical body 24 starts contacting the inner peripheral surface of the member W1 to be clamped, that is, the cylindrical body 24 is clamped. It is specified by the stroke of the piston rod 47 and the pressure (hydraulic pressure) in the working liquid chamber 30 at the time when the contact with the member W1 is started.

As a result, the calculation unit 52 uses the stroke of the piston rod 47 and the inside of the working liquid chamber 30 at the time when the outer peripheral surface 24A of the cylindrical body 24 starts contacting the inner peripheral surface of the clamped member W1 as the work gripping start point. The pressure (hydraulic pressure) is specified from these measured values. That is, the calculation unit 52 sets the work gripping start point (hereinafter, also referred to as zero point) based on the measurement data of the stroke of the piston rod 47 and the measurement data of the pressure in the working liquid chamber 30 measured by the hydraulic pressure measurement unit 72. calculate.

This is a power type in which the push rod 44 of the hydraulic clamp portion 10 is pushed by the piston rod 47 of the power cylinder portion 46 on the mounting machine side. When the piston rod 47 is pushed, pressure is applied to the hydraulic oil in the hydraulic chamber 30 of the hydraulic clamp portion 10, and the cylindrical body 24 is expanded and deformed. A pressure sensor device 60 is connected to the working liquid chamber 30 through passages 40, 82, and screw holes 80, and a pressure change inside the working liquid chamber 30 is measured by the hydraulic pressure measuring unit 72 of the pressure sensor device 60. ..

The stroke of the piston rod 47 and the moving position of the piston 36 are equivalent. In this embodiment, the stroke of the piston rod 47, which can be easily measured from the outside, is detected as the moving position of the piston 36.

The stroke of the piston rod 47 of the power cylinder unit 46 is detected by attaching a movement amount measuring device such as a length measuring device or a displacement meter to the piston rod 47 and measuring the movement amount of the piston rod 47 with this movement amount measuring device. .. When an electric cylinder is used for the power cylinder unit 46, the stroke of the piston rod 47 can be detected by calculating the amount of movement from the rotation angle of the motor and the lead of the ball screw.

The gripping force control unit 54 sets the pressure in the working liquid chamber 30 to a predetermined pressure based on the pressure in the working liquid chamber 30 at the work gripping start point detected by the calculation unit 52 (zero point). That is, the stroke of the piston rod 47 is controlled so as to obtain a predetermined gripping force. This gripping force can be replaced with the hydraulic pressure when the pressure in the working liquid chamber 30 is further increased from the work gripping start point.

Specifically, when the hydraulic oil sealed in the hydraulic fluid chamber 30 of the hydraulic clamp portion 10 is pressurized, the cylindrical body 24 is expanded and deformed. As described above, since the pressure (internal pressure) in the working liquid chamber 30 and the diameter-expanding deformation amount, and the cylinder stroke for pressurization and the diameter-expanding deformation amount are generally correlated by a linear function, the member to be clamped. When W1 is gripped, the gripping force can be grasped by the hydraulic pressure corresponding to the amount of diameter expansion deformation from the work gripping start point. A specific calculation method for obtaining the work gripping start point will be described later.

Next, the operation of the control unit 50 will be described with reference to FIGS. 4 and 5.

First, the member to be clamped W1 is attached to the hydraulic clamp portion 10 (step S11). Specifically, the clamped member W1 is mounted on the outer peripheral surface 24A of the cylindrical body 24.

Next, expansion (diameter expansion deformation) of the hydraulic clamp portion 10 is started (step S12). Specifically, the expansion of the cylindrical body 24 is started. In the process of step S12, the control unit 50 displays the stroke measurement data (measured value) of the piston rod 47 and the pressure measurement data (measured value) in the working liquid chamber 30 measured by the hydraulic pressure measuring unit 72 in chronological order. Monitor.

Then, the cylindrical body 24 is expanded (step S13).

Further, the calculation unit 52 of the control unit 50 determines the work gripping start point (zero point) from the stroke measurement data of the piston rod 47 and the pressure measurement data in the working liquid chamber 30 measured by the hydraulic pressure measurement unit 72. Calculate (step S14).

Next, the control unit 50 performs feedback control so that the pressure becomes a predetermined pressure based on the work gripping start point calculated in step S14 (step S15). Specifically, the gripping force control unit 54 of the control unit 50 refers to the working liquid from the measurement data of the stroke of the piston rod 47 and the measurement data of the pressure in the working liquid chamber 30 shown in FIG. 5 with reference to the work gripping start point. A control signal is output to the power cylinder unit 46 so that the pressure in the chamber 30 becomes a predetermined pressure. The power cylinder unit 46 inputs the control signal, and sets the stroke value of the piston rod 47 so that the pressure in the working liquid chamber 30 becomes a predetermined pressure.

As a result, the hydraulic clamp portion 10 elastically deforms (diameter-expands deformation) the cylindrical body 24 based on the stroke value, and controls the clamped member W1 to have a predetermined pressure (grip force). Will be done.

Here, it will be described that the member W1 to be clamped is controlled so as to have a predetermined pressure (grip force). Further, the predetermined gripping force is an arbitrary value set in advance when carrying out this control.

Since the plurality of clamped members W1 vary within the tolerance, when the cylindrical body 24 is elastically deformed (diameter-expanded deformation), the outer peripheral surface 24A of the cylindrical body 24 becomes the center hole A of the clamped member W1. The amount of diameter expansion deformation until contact with the inner peripheral surface varies. When the stroke of the piston rod 47 and the pressure in the working liquid chamber 30 at the time of contact, that is, the work gripping start point is not known, the shape is cylindrical so as to be surely larger than the inner diameter of the central holes A of the plurality of clamped members W1. Since the diameter of the body 24 is determined to be expanded and clamped, when a plurality of members W1 to be clamped are clamped, the gripping force varies.

Therefore, in the present embodiment, measurement data is obtained from the work gripping start point where the outer peripheral surface 24A of the cylindrical body 24 contacts and grips the inner peripheral surface of the central hole A of the clamped member W1. Therefore, based on this measurement data, it can be seen, for example, how much the stroke is from the work gripping start point and what pressure is used for gripping. Therefore, it is possible to control each member to be clamped W1 so as to have a predetermined pressure (grip force).

Further, after the machining is completed, the power cylinder unit 46 is returned to the origin which is the original position (step S16), and a series of processing of the control unit 50 is completed.

Next, six specific methods for calculating the work gripping start point in step S14 will be described.

(First work gripping start point calculation method)
FIG. 6 is a graph showing an example of calculating the work gripping start point based on the measurement data in the first embodiment.

Based on the stroke measurement data of the piston rod 47 obtained by the present embodiment and the pressure measurement data in the working liquid chamber 30 measured by the hydraulic pressure measuring unit 72, the calculation unit 52 is as shown in FIG. Two points (in FIG. 6) of a section a (first section) from the start of expansion (elastic deformation) of the cylindrical body 24 of the hydraulic clamp portion 10 to the expansion to the value of the lower limit of the tolerance of the member W1 to be clamped. The section b (second section) from the point where the clamped member W1 expands to the upper limit of the tolerance to the maximum expansion (most elastic deformation) of the cylindrical body 24 of the hydraulic clamp portion 10). ) (Points indicated by Δ in FIG. 6) to create linear data. The intersection of these two straight lines is defined as the work gripping start point (zero point).

After the work gripping start point is detected, feedback control is performed so that the pressure in the working liquid chamber 30 becomes a predetermined pressure with respect to the work gripping start point. The control target at this time may be based on either the stroke or the pressure. The reference for this control target is the same for the following work gripping start point calculation method.

(Second work gripping start point calculation method)
Based on the stroke measurement data of the piston rod 47 obtained by the present embodiment and the pressure measurement data in the working liquid chamber 30 measured by the hydraulic pressure measuring unit 72, the calculation unit 52 of the section a and the section b Each measurement data is converted into two-line data by the linear regression method. The intersection of these two straight lines is set as the work gripping start point.

After the work gripping start point is detected, feedback control is performed so that the pressure becomes a predetermined pressure with respect to the work gripping start point in the same manner as described above.

(Third work gripping start point calculation method)
The inclination of the hydraulic clamp portion 10 can be obtained from the measurement data showing the correlation between the pressure of the working liquid before the hydraulic clamp portion 10 comes into contact with the clamped member W1 and the stroke of the piston rod 47. This inclination is determined by the linear proportional constant of the pressure of the working liquid and the stroke of the piston rod 47, and corresponds to the ratio of the pressure increase in the working liquid chamber 30 to the stroke amount of the piston rod 47 (pressure increase rate). do.

When the hydraulic clamp portion 10 comes into contact with the clamped member W1 and the piston rod 47 is further stroked to expand the hydraulic clamp portion 10, the pressure increase rate in the working liquid chamber 30 contacts the clamped member W1. It rises above the rate of increase in pressure. The change point at which the pressure increase rate changes is defined as the work gripping start point.

After the work gripping start point is detected, feedback control is performed so that the pressure becomes a predetermined pressure with respect to the work gripping start point in the same manner as described above.

In the third work gripping start point calculation method, the gripping point can be detected by the first work gripping start point calculation method and the second work gripping start point calculation method with the change point at which the pressure increase rate changes as a boundary. It is possible.

(Fourth work gripping start point calculation method)
From the measurement data showing the correlation between the pressure of the working liquid in the section a and the stroke of the piston rod 47, the unique inclination of the hydraulic clamp portion 10 at that time (inclination of the individual for each hydraulic clamp portion 10). Is obtained. This inherent inclination is determined by the amount of pressure increase in the working liquid chamber 30 with respect to a certain amount of the stroke of the piston rod 47 (hereinafter, referred to as an inherent inclination).

When the hydraulic clamp portion 10 comes into contact with the clamped member W1 and the piston rod 47 is further stroked to expand the hydraulic clamp portion 10, the amount of pressure increase in the working liquid chamber 30 comes into contact with the clamped member W1. It rises from the amount of increase up to. The change point at which the amount of pressure increase changes is defined as the work gripping start point.

That is, in this calculation method, when the piston rod 47 is stroked until the elastic deformation of the cylindrical body 24 of the hydraulic clamp portion 10 is maximized, the inclination of the measurement data showing the correlation is greater than or equal to the inherent inclination. The changed point is set as the work gripping start point. In the same manner as described above, feedback control is performed so that the pressure becomes a predetermined pressure with respect to the work gripping start point.

(Fifth work gripping start point calculation method)
FIG. 7 is a flowchart showing another example of calculating the work gripping start point based on the measurement data in the first embodiment. The fifth work gripping start point calculation method uses measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod 47 in a state where the clamped member W1 is not attached to the hydraulic clamp portion 10. Hereinafter, a specific description will be given.

As shown in FIG. 7, the clamped member W1 is not attached to the hydraulic clamp portion 10 (not attached to the hydraulic clamp device) (step S1). Specifically, the clamped member W1 is not mounted on the outer peripheral surface 24A of the cylindrical body 24.

Next, expansion (diameter expansion deformation) of the hydraulic clamp portion 10 is started (step S2). In the process of step S2, the control unit 50 monitors the stroke measurement data of the piston rod 47 and the pressure measurement data in the working liquid chamber 30 measured by the hydraulic pressure measurement unit 72. Then, the piston rod 47 of the hydraulic clamp portion 10 is stroked until it reaches the maximum stroke (step S3).

In the present embodiment, the peculiar inclination of the hydraulic clamp portion 10 is detected from the measurement data (first measurement data) showing the correlation between the stroke measurement data at this time and the pressure in the working liquid chamber 30. be able to.

Next, the member to be clamped W1 is attached to the hydraulic clamp portion 10, and expansion (diameter expansion deformation) of the hydraulic clamp portion 10 is started (steps S11 and S12). In the process of step S12, the control unit 50 monitors the measurement data of the stroke of the piston rod 47 and the measurement data of the pressure in the working liquid chamber 30 measured by the hydraulic pressure measuring unit 72. Then, the piston rod 47 is stroked to the maximum stroke of the hydraulic clamp portion 10 (step S13).

In steps S11 to S13, when the hydraulic clamp portion 10 is expanded in the mounted state, the cylindrical body 24 comes into contact with the clamped member W1. Further, by stroking the piston rod 47 to increase the pressure of the working liquid, the pressure in the working liquid chamber 30 and the piston rod 47 after the cylindrical body 24 of the hydraulic clamp portion 10 comes into contact with the member W1 to be clamped. Measurement data (second measurement data) showing the correlation with the stroke is obtained. Therefore, from this measurement data, the inclination of the member to be clamped W1 after being clamped can be detected. The work gripping start point calculation method at this time is the same as the first and second work gripping start point calculation methods, and the intersection of these two straight lines of inclination is set as the work gripping start point.

After the work gripping start point is detected, feedback control is performed so that the pressure becomes a predetermined pressure with respect to the work gripping start point in the same manner as described above. Other processes are the same as the flowchart shown in FIG. 4, and the description thereof will be omitted.

In the fifth work gripping start point calculation method, after obtaining the measurement data showing the relationship between the first measurement data of the stroke in the state of not being mounted on the clamped member W1 and the pressure in the working liquid chamber 30. , The measurement data in the set state is continuously obtained, but the measurement data in the non-set state may be obtained in advance.

(6th work gripping start point calculation method)
In this work gripping start point calculation method, the cylindrical body 24 of the hydraulic clamping portion 10 is expanded without clamping the clamped member W1. By this operation, the peculiar inclination of the hydraulic clamp portion 10 can be detected.

Next, by mounting and clamping the member to be clamped W1, the inclination of the member to be clamped W1 after being clamped can be detected.

The point at which the inclination obtained by clamping the member W1 to be clamped changes more than the inclination obtained without the member W1 to be clamped is defined as the work gripping start point. That is, with respect to the inclination of the first measurement data obtained without the clamped member W1 attached, the pressure of the working liquid when the piston rod 47 is stroked to the maximum stroke with the clamped member W1 attached. In relation to the stroke of the piston rod 47, a point that changes more than the inclination of the first measurement data is defined as a work gripping start point. After the detection of the work gripping start point, feedback control is performed so that the pressure becomes a predetermined pressure with respect to the work gripping start point in the same manner as described above. In this work gripping start point calculation method, the expansion step of step S13 shown in FIG. 7 becomes unnecessary.

By the way, in the fourth and sixth work gripping start point calculation methods, since the hydraulic clamp portion 10 is gradually expanded and the point where the pressure changes above the specified pressure is set as the work gripping start point, the member to be clamped. No unnecessary force is applied to W1.

In the fifth and sixth work gripping start point calculation methods, there are two movements (motion): an operation in a non-set state in which the clamped member W1 is not clamped, and an operation in a set state in which the clamped member W1 is clamped. Is required. The inherent inclination of the hydraulic clamp portion 10 obtained by this operation has an effect that the reliability of the data is improved because the number of measurement data is larger than that of the first and second work gripping start point calculation methods. ..

As described above, according to the present embodiment, by providing the calculation unit 52 that calculates the work gripping start point at which the clamped member W1 is started to be clamped by the cylindrical body 24, each clamped member W1 whose dimensions vary within the tolerance. It becomes possible to find the work gripping start point.

Further, according to the present embodiment, the calculation unit 52 calculates the work gripping start point based on the pressure of the working liquid measured by the hydraulic pressure measuring unit 72 and the measurement data of the stroke of the piston rod 47. , The work gripping start point can be calculated.

Further, according to the present embodiment, the gripping force control unit 54 makes the elastic deformation amount (expansion amount) of the cylindrical body 24 a predetermined gripping force with respect to the clamped member W1 with reference to the work gripping start point. Therefore, even if the clamped member W1 has dimensional variations, the gripping force with respect to the clamped member W1 can be set to a predetermined value.

[Embodiment 2]
FIG. 8 is a block diagram showing a control circuit of the hydraulic clamp device according to the second embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals, and different configurations and operations will be described.

As shown in FIG. 8, in the present embodiment, instead of the pressure sensor device 60 of the first embodiment, a load cell 85 as a pressure measuring device is attached to the tip of the power cylinder unit 46.

In the present embodiment, the stroke of the power cylinder unit 46 and the pressure of the load cell 85 are calculated to obtain the work gripping start point (zero point) as in the first embodiment.

As described above, according to the present embodiment, by using the load cell 85 as the pressure measuring device, the structure can be simplified as compared with the hydraulic pressure measuring unit 72 as in the first embodiment.

In the present embodiment, the load cell 85 is attached to the tip of the power cylinder portion 46, but the present invention is not limited to this, and the load cell 85 may be incorporated in the piston rod 47 or the hydraulic clamp portion 10. Since other configurations and operations are the same as those in the first embodiment, the description thereof will be omitted.

[Embodiment 3]
Next, the hydraulic clamp device 100 of the third embodiment will be described with reference to FIG. In the third embodiment, the description of substantially the same part as that of the first embodiment will be omitted.

The hydraulic clamp device 100 is of a mandrel type, and includes a clamp member 106 including a substantially round bar-shaped main body (first member) 102 and a cylindrical body (second member) 104 forming a thin-walled wall body. Have.

The main body 102 has a first axial portion 108, a flange portion 110, and a second axial portion 112 on the same axis in order in the axial direction. The flange portion 110 has an outer diameter larger than that of the first axial portion 108 and the second axial portion 112, and extends outward in the radial direction with respect to the first axial portion 108 and the second axial portion 112. It is formed. A peripheral groove-shaped recess 114 is formed on the outer periphery of the first shaft-shaped portion 108.

The cylindrical body 104 is fitted on the outer periphery of the first axial portion 108, and the inner peripheral surface 104A (inner surface side) corresponding to the recess 114 defines the working liquid chamber 116 having an annular cross-sectional shape. O-rings 118 for ensuring the liquidtightness of the working liquid chamber 116 are mounted on both sides of the outer peripheral surface 108A of the first axial portion 108 in the axial direction across the working liquid chamber 116. The cylindrical body 104 defines a clamp surface for clamping the member to be clamped (work) W2 (see FIG. 11) including the cylindrical portion by the outer peripheral surface (outer surface side) 104B.

A cylindrical portion 120A of the outer tubular body 120 is fitted on the outer periphery (outer peripheral surface 108A) of the first axial portion 108. The outer tubular body 120 includes a flange portion 120B formed on one shaft end side of the cylindrical portion 120A, and the flange portion 120B is fixed to the flange portion 110 by a bolt 122. The cylindrical portion 120A includes a thin-walled portion that overlaps the outer periphery of the cylindrical body 104. The outer tubular body 120 positions the clamped member W2 in the axial direction by abutting the clamped member W2 on the tip of the cylindrical portion 120A.

A first piston chamber 130 extending in the axial direction on the central axis is formed in the second axial portion 112 of the main body 102. A second piston chamber 132 extending in the radial direction is formed in the flange portion 110 of the main body 102. The first piston chamber 130 and the second piston chamber 132 communicate with each other in the main body 102. The first piston chamber 130 is provided with the first piston 134 so as to be movable in the extending direction of the first piston chamber 130. A second piston 136 is provided in the second piston chamber 132 so as to be movable in the extending direction of the second piston chamber 132.

One end of the first piston chamber 130 (on the right side when viewed in FIG. 9) communicates with the working liquid chamber 116 through an axial passage 138 and a plurality of radial passages 140 formed in the main body 102. ..

The passage 138 side of the first piston chamber 130 separated by the first piston 134, the first piston chamber 130 side of the second piston chamber 132 separated by the second piston 136, the passages 138, 140 and the working liquid chamber 116 are It forms a closed space, and the closed space is filled and sealed with hydraulic oil, which is a working liquid.

A bush 142 is screwed to the second axial portion 112 of the main body 102, which is the other side of the first piston 134 (left side when viewed in FIG. 9). The bush 142 is formed with a through hole 142A that penetrates the central portion in the axial direction. A push rod 144 is coaxially engaged with the first piston 134 in the through hole 142A so as to be movable in the axial direction. The push rod 144 advances the first piston 134 via the steel ball 146 by moving toward the first piston 134 (moving to the right as seen in FIG. 9). By advancing the first piston 134, the working liquid in the working liquid chamber 116 is quantitatively pressurized according to the amount of advancing of the first piston 134. The first piston 134 moves forward by being pressed from the outside by the push rod 144.

Since the push rod 144 has the enlarged diameter portion 144A at the end on the steel ball 146 side, the movement to the left as seen in FIG. 9 is restricted and the push rod 144 is prevented from coming off.

The flange portion 110 is formed with a screw hole 148 having an outer end opened on the outer peripheral surface of the flange portion 110 and an inner end communicating with the second piston chamber 132 on the side opposite to the first piston chamber 130. An operating screw member 150 is screw-engaged with the screw hole 148. The operating screw member 150 advances the second piston 136 via the steel ball 152 by screwing (moving upward as seen in FIG. 9). By advancing the second piston 136, the working liquid in the working liquid chamber 116 is quantitatively pressurized according to the amount of advancing of the second piston 136.

In the hydraulic clamping device 100, when the working liquid in the working liquid chamber 116 is pressurized by the first piston 134 or the second piston 136, the diameter of the cylindrical body 104 is expanded by elastic deformation, and the outer circumference of the cylindrical body 104 is expanded. The surface 104B is pressed against the inner peripheral surface of the cylindrical portion of the member to be clamped W2 set on the outer periphery of the cylindrical body 104 to clamp (grip) the member to be clamped W2.

A pressure sensor device (pressure measuring device) 160 is attached to the flange portion 110. The pressure sensor device 160 is equivalent to the pressure sensor device 60 described above, and the pressure (hydraulic pressure) of the working liquid in the working liquid chamber 116 is exerted from the pressure propagation passage 154 filled with the working liquid, and the hydraulic pressure is concerned. To measure.

Next, an embodiment of the work gripping start point detection method and the work gripping method in gripping the clamped member W2 using the hydraulic clamping device 100 will be described with reference to FIG.

An outer setup device 200 is provided in order to efficiently carry out the work gripping start point detection method and the work gripping method.

The outer setup device 200 presses the main body 202, the chuck device 204 that detachably fixes the hydraulic clamping device 100 to the main body 202, and the push rod 144 in order to move the first piston 134 of the hydraulic clamping device 100 forward. Hydraulic or electric linear actuator 206, a piston movement position detection device 208 that detects the movement position (stroke) of the first piston 134 from the drive amount of the linear actuator 206, and a sequence that controls the drive of the linear actuator 206. It has a control device 210.

Along with the outer setup device 200, a work gripping start point detecting device 212 for carrying out the work gripping start point detecting method according to the present embodiment is provided. The work gripping start point detection device 212 is an electronically controlled device including a microcomputer, and a signal (measurement data) indicating the pressure of the working liquid in the working liquid chamber 116 is input from the pressure sensor device 160 of the hydraulic clamping device 100. Then, a signal (measurement data) indicating the moving position of the first piston 134 is input from the piston moving position detecting device 208, and the moving position of the first piston 134 is driven forward by the sequence control device 210 to drive the linear actuator 206. The work gripping start point is detected based on the pressure change of the working liquid of the working liquid chamber 116 with respect to.

The pressure of the working liquid in the working liquid chamber 116 can be detected from the measured value by measuring the load acting on the first piston 134 by the load cell 207 attached to the linear actuator 206.

The work gripping start point referred to here is the moving position of the first piston 134 and the operation of the working liquid chamber 116 when the outer peripheral surface 104B of the cylindrical body 104 starts to contact the inner peripheral surface of the clamped member W2. It is specified by the pressure of the liquid.

Therefore, in the detection of the work gripping start point by the work gripping start point detecting device 212, the outer peripheral surface 104B of the cylindrical body 104 is covered based on the pressure change of the working liquid in the working liquid chamber 116 with respect to the moving position of the first piston 134. The time when the contact with the inner peripheral surface of the clamp member W2 is started is specified, and the moving position of the first piston 134 and the pressure of the working liquid in the working liquid chamber 116 at that time are detected. The detection result of the work gripping start point is displayed on the monitor 214.

The work gripping start point detection device 212 detects the work gripping start point by any one of the embodiments (A) to (C) or a combination thereof.

(A) The work gripping start point is a time point at which the pressure rise rate of the working liquid in the working liquid chamber 116 with respect to the moving position of the first piston 134 changes with the clamped member W2 attached to the hydraulic clamping device 100. The embodiment (A) corresponds to the above-mentioned third work gripping start point calculation method.

(B) The moving position of the first piston 134 and the working liquid chamber in the moving section of the first piston 134, which is presumed that the outer peripheral surface 104B of the hydraulic clamping device 100 does not abut against the inner peripheral surface of the member W2 to be clamped. The equation (Equation 1) showing the relationship with the pressure of the working liquid of 116 and the first piston in the moving section of the first piston 134 estimated that the outer peripheral surface 104B abuts on the inner peripheral surface of the clamped member W2. The solution of the simultaneous equations based on the equation (Equation 2) showing the relationship between the moving position of 134 and the pressure of the working liquid in the working liquid chamber 116 is set as the work gripping start point.

Assuming that the moving position of the first piston 134 is X and the pressure of the working liquid in the working liquid chamber 116 is Y, (Equation 1) is represented by Y = mX + A, and (Equation 2) is represented by Y = nX + B. However, A and B are intercepts, respectively.

M and n in (Equation 1) and (Equation 2) are proportional constants, and m <n. The proportionality constants m and n correspond to the slopes of the straight lines according to the straight line data of the intervals a and b. The solution of the simultaneous equations by (Equation 1) and (Equation 2) is the intersection of two straight lines. The embodiment (B) corresponds to the first and second work gripping start point calculation methods described above.

The moving section of the first piston 134 in which the outer peripheral surface 104B does not abut on the inner peripheral surface of the clamped member W2 and the moving section of the first piston 134 in which the outer peripheral surface 104B abuts on the inner peripheral surface of the clamped member W2. If the tolerance of the clamped member W2 is known, the estimation can be made in consideration of the tolerance.

That is, in the moving section of the first piston 134 in which the outer peripheral surface 104B does not abut against the inner peripheral surface of the clamped member W2, the outer diameter of the outer peripheral surface 104B becomes the lower limit of the tolerance of the clamped member W2 from the initial position. The section up to the position where it expands to the corresponding outer diameter. The moving section of the first piston 134 in which the outer peripheral surface 104B abuts on the inner peripheral surface of the clamped member W2 is outside the outer peripheral surface 104B from a position where it expands to an outer diameter corresponding to the lower limit of the tolerance of the clamped member W2. The section up to the position where the diameter reaches the maximum allowable value.

(C) The pressure change of the working liquid in the working liquid chamber 116 with respect to the moving position of the first piston 134 in a state where the clamped member W2 is not attached to the hydraulic clamping device 100, and the clamped member W2 is attached to the hydraulic clamping device 100. The work gripping start point is detected from the mutual difference between the pressure change of the working liquid in the working liquid chamber 116 with respect to the moving position of the first piston 134 in the mounted state.

In the embodiment (C), similarly to the embodiment (B), the moving position of the first piston 134 and the pressure of the working liquid in the working liquid chamber 116 in a state where the clamped member W2 is not attached to the hydraulic clamping device 100 And the equation (Equation 1) showing the relationship between the moving position of the first piston 134 and the pressure of the working liquid in the working liquid chamber 116 when the clamped member W2 is attached to the hydraulic clamping device 100 (Equation 1). The solution of the simultaneous equations according to Equation 2) is set as the work gripping start point.

In the embodiment (C), as compared with the embodiment (B), the moving position of the first piston 134 and the operation of the working liquid chamber 116 in the state where the clamped member W2 is not attached to the hydraulic clamping device 100 and in the state where the clamped member W2 is attached are respectively. Since the section showing the relationship with the pressure of the liquid is large, it can be expected that the detection accuracy of the work gripping start point will be improved as compared with the embodiment (B).

The work gripping method according to the present embodiment is carried out in the following manner after the work gripping start point detection work described above.

With the work gripping start point (moving position of the first piston 134 and pressure of the working liquid in the working liquid chamber 116) displayed on the monitor, the linear actuator 206 is driven backward, the first piston 134 is returned to the initial position, and the hydraulic pressure type. With the member W2 to be clamped attached to the clamping device 100, the pressure of the working liquid in the working liquid chamber 116 at the work gripping start point is increased by the screwing of the working screw member 150 by the tool 220, and the working liquid chamber at the work gripping start point. The pressure is increased under monitoring by a monitor display or the like until the value obtained by adding the pressure required to obtain the required workpiece gripping force to the pressure of the working liquid of 116 is reached.

As a result, the detection of the work gripping start point and the external setup of the work gripping are completed. The hydraulic clamp device 100 for which the outer setup has been completed is attached to the chuck device 232 of the machine tool 230 as shown in FIG. 11 while holding the clamped member W2.

[Embodiment 4]
Next, the hydraulic clamp device 300 of the fourth embodiment will be described with reference to FIG. In FIG. 12, the portion corresponding to FIG. 1 is designated by the same reference numeral as that shown in FIG. 1, and the description thereof will be omitted.

The hydraulic clamp device 300 is of a chuck type, and is a clamp including a substantially round bar-shaped cylindrical main body (first member) 302 and a cylindrical body (second member) 310 forming a thin-walled wall body. It has a member 308.

The main body 302 has a first tubular portion 304 and a second tubular portion 306 on the same axis in the axial direction. The second tubular portion 306 has a larger diameter than the first tubular portion 304 and forms a flange portion expanded in the radial direction.

The cylindrical body 310 is fitted on the inner circumference of the main body 302. The cylindrical body 310 includes an inner peripheral surface 310A that clamps the round bar-shaped member to be clamped W3 and an outer peripheral surface (second peripheral surface) 310B that overlaps the inner peripheral surface (first peripheral surface) 302A of the main body 302. ing.

A peripheral groove-shaped recess 312 is formed on the outer peripheral surface 310B of the cylindrical body 310. The main body 302 and the cylindrical body 310 define an annular working liquid chamber 314 having a cross section (cross section orthogonal to the central axis) extending over the entire circumference of the inner peripheral surface 302A of the main body 302 by a recess 312. ing.

Thus, the cylindrical body 310 forming the wall body defines the working liquid chamber 314 on the inner surface side and the clamp surface (inner peripheral surface 310A) on the outer surface side.

On the inner peripheral surface 302A of the main body 302, O-rings 316 for ensuring the liquidtightness of the working liquid chamber 314 are mounted on both sides of the working liquid chamber 314 in the axial direction.

A piston chamber 318 extending in the axial direction is formed in the main body 302. A piston 320 is fitted in the piston chamber 318 so as to be movable in the axial direction. One end of the piston chamber 318 communicates with the working liquid chamber 314 by a radial passage 322 formed in the second tubular portion 306.

The chamber space, the passage 322, and the working liquid chamber 314 on the passage 322 side of the piston chamber 318 separated by the piston 320 form one closed space, and are filled with hydraulic oil such as grease.

The main body 302 is formed with a screw hole 324 that extends in the axial direction, communicates with the other end of the piston chamber 318, and opens in the end surface 304A of the first tubular portion 304. A working screw member 326 with a hexagonal hole is screw-engaged with the screw hole 324. A steel ball 328 is arranged between the working screw member 326 and the piston 320. The operating screw member 326 is screwed into the screw hole 324 toward the piston chamber 318, and the screwing moves the piston 320 forward through the steel ball 328.

In this way, the pressure structure is configured, and the piston 320 moves the piston chamber 318 to the passage 322 side (left side when viewed in FIG. 12) by screwing the working screw member 326, so that the hydraulic oil in the working liquid chamber 314 is released. When pressure is applied, the cylindrical body 310 is radially inwardly reduced due to elastic deformation in the radial direction.

As a result, the member W3 to be clamped is clamped on the inner peripheral surface 310A of the cylindrical body 310 under the reduced diameter deformation of the cylindrical body 310. More specifically, the member to be clamped W3 is fixed (clamped) to the hydraulic clamping device 300 by bringing the inner peripheral surface 310A of the cylindrical body 310 into close contact with the outer peripheral surface due to the reduced diameter deformation of the cylindrical body 310. ..

A pressure sensor device 60 is attached to the second tubular portion 306. The pressure sensor device 60 is the same as that of the first embodiment, and the pressure (hydraulic pressure) of the working liquid in the working liquid chamber 314 is exerted from the pressure propagation passage 330 formed in the main body 302, and the hydraulic pressure is applied. taking measurement. The hydraulic pressure of the working liquid chamber 314 measured by the pressure sensor device 60 is displayed on the display unit 94 of the wireless reader 90 by wireless communication as in the first embodiment.

Also in this chuck type hydraulic clamp device 300, based on the measurement of the hydraulic pressure of the working liquid chamber 314 and the movement amount of the piston 320 by the pressure sensor device 60, the above-mentioned mandrel type hydraulic clamp portion 10 and the hydraulic pressure type The work gripping start point can be detected and the work can be gripped by the same method as the work gripping start point detection method and the work gripping method in the clamp device 100.

[Embodiment 5]
Next, the hydraulic clamp device 400 of the fifth embodiment will be described with reference to FIG. In FIG. 13, the parts corresponding to FIGS. 1, 9 and 12 are designated by the same reference numerals as those given in FIGS. 1, 9 and 12, and the description thereof will be omitted.

The hydraulic clamp device 400 is of a chuck type, and is a clamp including a cylindrical body (first member) 402 having a substantially round bar shape and a cylindrical body (second member) 412 forming a wall body having a thin wall structure. It has a member 420.

The main body 402 has a first axial portion 404, a flange portion 406, and a second axial portion 408 on the same axis in order in the axial direction. The flange portion 406 has an outer diameter larger than that of the first axial portion 404 and the second axial portion 408, and extends outward in the radial direction with respect to the first axial portion 404 and the second axial portion 408. It is formed.

At the center of the first axial portion 404, a bottomed hole 410 having a circular cross-sectional shape is formed on the right end surface of the first axial portion 404 as seen in FIG.

The cylindrical body 412 is fitted into the bottomed hole 410, and a circumferential groove-shaped recess 414 formed on the outer peripheral surface defines an annular cross-sectional shape working liquid chamber 314 between the cylindrical body 412 and the main body 402. The main body 402 and the cylindrical body 412 are joined to each other on both sides of the working liquid chamber 314 in the axial direction by continuous brazing (not shown) or the like in the circumferential direction of the main body 402 and the cylindrical body 412, respectively. The liquidtightness of the working liquid chamber 314 is ensured. The cylindrical body 412 defines a clamp surface for clamping the member to be clamped (work) W3 by an inner peripheral surface (outer surface side) 412A.

Thus, the cylindrical body 412 forming the wall body defines the working liquid chamber 314 on the inner surface side and the clamp surface (inner peripheral surface 412A) on the outer surface side.

Similar to the third embodiment, the main body 402 includes the first piston chamber 130, the first piston 134, the push rod 144, and the like, and the hydraulic pressure of the working liquid chamber 314 is increased by pushing the push rod 144 from the outside. A second pressurizing mechanism, which includes the piston chamber 318, the piston 320, the working screw member 326, and the like, and raises the hydraulic pressure of the working liquid chamber 314 by screwing the working screw member 326, as in the fourth embodiment. A pressure mechanism is provided.

Similar to the first and fourth embodiments, the flange portion 406 is equipped with a pressure sensor device 60 for measuring the pressure (hydraulic pressure) of the working liquid in the working liquid chamber 314.

Also in this chuck type hydraulic clamp device 400, the above-mentioned mandrel type hydraulic clamp is also measured based on the measurement of the hydraulic pressure of the working liquid chamber 314 and the movement amount of the first piston 134 and the piston 320 by the pressure sensor device 60. The work gripping start point can be detected and the work can be gripped by the same method as the work gripping start point detection method and the work gripping method in the portion 10 and the hydraulic clamp device 100.

Although each embodiment of the present invention has been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

In each of the above embodiments, an example in which hydraulic oil is used as the hydraulic liquid has been described, but water or a gel-like substance can also be used in addition to this.

Further, in the present invention, the one provided with the tapered collet is also applicable. Specifically, a tapered collet is provided instead of the cylindrical body 24, a columnar main body having a tapered outer peripheral surface is provided in the tapered collet, and the outer peripheral surface of the tapered collet is clamped. It is inserted into the inner peripheral surface of W1 so that the cylindrical body is pulled from the tapered collet. As a result, the stroke (axial position) of the columnar main body changes, so that the pressure on the clamped member W1W2 changes.

10: Hydraulic clamp part 12: Main body (first member)
16: First axial portion 16A: Outer peripheral surface (first peripheral surface)
16B: End face 18: Flange portion 20: Second shaft-shaped portion 22: Rod-shaped portion 24: Cylindrical body (second member)
24A: Outer peripheral surface 24B: Inner peripheral surface (second peripheral surface)
28: Recess 30: Working liquid chamber 32: O-ring 34: Piston chamber 36: Piston 38: Passage 40: Passage 42: Bush 42A: Through hole 44: Push rod 46: Power cylinder portion (drive device)
47: Piston rod 48: Steel ball 50: Control unit 52: Arithmetic unit (arithmetic unit)
54: Gripping force control unit (grip force control device)
60: Pressure sensor device 62: Flange part 64: Male thread part 65: Recessed groove 66: Hexagonal part 67: Rubber packing 68: Housing 69: Oil 70: Cap part 72: Hydraulic pressure measuring part (pressure measuring device)
74: Pressure introduction passage 76: Wireless communication unit 78: Power receiving unit 80: Screw hole 82: Passage 85: Load cell (pressure measuring device)
90: Wireless reader 92: Measurement button 94: Display 100: Hydraulic clamp device 102: Main body 104: Cylindrical body (second member)
104A: Inner peripheral surface 104B: Outer peripheral surface (clamp surface)
106: Clamp member 108: First axial portion (first member)
108A: Outer peripheral surface 110: Flange portion 112: Second axial portion 114: Recessed portion 116: Working liquid chamber 118: O ring 120: Outer cylinder 120A: Cylindrical portion 120B: Flange portion 122: Bolt 130: First piston chamber 132 : Second piston chamber 134: First piston 136: Second piston 138: Passage 140: Passage 142: Bush 142A: Through hole 144: Push rod 144A: Expanded diameter portion 146: Steel ball 148: Screw hole 150: Actuating screw member 152: Steel ball 154: Pressure propagation passage 160: Pressure sensor device 200: External setup device 202: Main body 204: Chuck device 206: Linear actuator 207: Load cell 208: Piston movement position detection device 210: Sequence control device 212: Work gripping start Point detection device 214: Monitor 220: Tool 230: Machine machine 232: Chuck device 300: Hydraulic clamp device 302: Main body (first member)
302A: Inner peripheral surface (first peripheral surface)
304: First tubular portion 304A: End face 306: Second tubular portion 308: Clamp member 310: Cylindrical body (second member)
310A: Inner peripheral surface (clamp surface)
310B: Outer peripheral surface (second peripheral surface)
312: Recessed 314: Working liquid chamber 316: O-ring 318: Piston chamber 320: Piston 322: Passage 324: Screw hole 326: Working screw member 328: Steel ball 330: Pressure propagation passage 400: Hydraulic clamp device 402: Main body ( 1st member)
404: First axial portion 406: Flange portion 408: Second axial portion 410: Bottomed hole 412: Cylindrical body (second member)
412A: Inner peripheral surface (clamp surface)
414: Recessed portion 420: Clamp member

Claims (18)

A first member having a first peripheral surface forming an outer peripheral surface or an inner peripheral surface, and a second member having a second peripheral surface forming an inner peripheral surface or an outer peripheral surface overlapping the first peripheral surface. And have
In the portion where the first member and the second member overlap each other, the working liquid chamber is defined by recesses provided in at least one of the first peripheral surface and the second peripheral surface, and the working liquid chamber is defined. A hydraulic clamping device that clamps a member to be clamped by elastically deforming the second member due to the pressure of the working liquid enclosed in the clamp.
A pressure measuring device for measuring the pressure of the working liquid sealed in the working liquid chamber, and a pressure measuring device.
A piston chamber formed in the first member and communicating with the working liquid chamber,
It is provided with a driving device provided in the piston chamber and provided with a piston rod for driving the piston, and an arithmetic unit for calculating a work gripping start point at which the clamped member is started to be clamped by the second member.
The arithmetic device is a hydraulic clamp device that calculates the work gripping start point based on the measurement data of the pressure of the working liquid and the stroke of the piston rod measured by the pressure measuring device. Based on the measurement data showing the relationship between the pressure of the working liquid and the stroke of the piston rod, the arithmetic unit has a number from the start of elastic deformation of the second member to the lower limit of the tolerance of the member to be clamped. Straight line data is created from the two points in the section 1 and the two points in the second section from the point where the second member becomes the same as the upper limit of the tolerance of the member to be clamped to the most elastic deformation. The hydraulic clamping device according to claim 1, wherein the intersection of the two straight lines is set as the work gripping start point. The computing device obtains measurement data indicating the relationship between the pressure of the working liquid and the stroke of the piston rod, from the first elastic deformation of the second member to the lower limit of the intersection of the clamped member. In each section of the second section from the point where the second member becomes the same as the upper limit of the tolerance of the member to be clamped to the most elastic deformation, each linear data is calculated by the linear regression method, and these The hydraulic clamping device according to claim 1, wherein the intersection of the two straight lines is set as the work gripping start point. In the computing device, after the second member starts elastic deformation, the pressure in the working liquid chamber increases in the measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod by a linear function. The hydraulic clamping device according to claim 1, wherein the point at which the rate changes is set as the work gripping start point. In the arithmetic device, the pressure of the working liquid and the stroke of the piston rod in the section from the start of elastic deformation of the second member to the lower limit of the tolerance of the member to be clamped are correlated by a linear function. The second inclination of the measurement data showing the correlation by the linear function when the piston rod is stroked until the elastic deformation of the second member is maximized with respect to the first inclination of the measurement data shown. The hydraulic clamping device according to claim 1, wherein a point changed to the first inclination or more is set as the work gripping start point. In the computing device, the pressure of the working liquid and the stroke of the piston rod are used in the section from the start of the second member to the most elastic deformation in the state where the clamped member is not attached. Is most elastically deformed from the point where the first measurement data showing the correlation by the linear function and the second member become the same as the upper limit of the tolerance of the clamped member in the state where the clamped member is attached. In the section up to, linear data is calculated from the second measurement data showing the correlation between the pressure of the working liquid and the stroke of the piston rod by the linear function, and the intersection of these two straight lines is the work gripping start point. The hydraulic clamping device according to claim 1, wherein the hydraulic clamping device is characterized. In the computing device, the pressure of the working liquid and the stroke of the piston rod are measured in the section from the start of the second member to the most elastic deformation in the state where the clamped member is not attached. With respect to the inclination of the first measurement data showing the correlation by the linear function, the pressure of the working liquid and the pressure when the piston rod is stroked to the maximum stroke with the clamped member attached. The claim is characterized in that the work gripping start point is a point at which the inclination of the second measurement data indicating the correlation between the stroke of the piston rod and the stroke by a linear function changes to be equal to or greater than the inclination of the first measurement data. The hydraulic clamping device according to 1. Further provided is a gripping force control device that elastically deforms the second member with reference to the work gripping start point and controls the pressure of the working liquid so that a predetermined gripping force is obtained with respect to the clamped member. The hydraulic clamp device according to any one of claims 1 to 7. A first member having a first peripheral surface forming an outer peripheral surface or an inner peripheral surface, and a second member having a second peripheral surface forming an inner peripheral surface or an outer peripheral surface overlapping the first peripheral surface. And have
In the portion where the first member and the second member overlap each other, the working liquid chamber is defined by recesses provided in at least one of the first peripheral surface and the second peripheral surface, and the working liquid chamber is defined. A hydraulic clamping device that clamps a member to be clamped by elastically deforming the second member due to the pressure of the working liquid enclosed in the clamp.
An arithmetic unit that calculates a work gripping start point at which the second member starts clamping the member to be clamped, and an arithmetic unit.
It is provided with a gripping force control device that elastically deforms the second member with reference to the work gripping start point and controls the pressure of the working liquid so that a predetermined gripping force is obtained with respect to the clamped member. A hydraulic clamp device characterized by the fact that. A clamp member provided with a working liquid chamber inside and a piston for pressurizing the working liquid filled in the working liquid chamber are provided, and the clamp member defines the working liquid chamber on the inner surface side and is on the outer surface side. The wall body defines the clamp surface, and the wall body is elastically deformed by the pressurization of the working liquid by the movement of the piston, and the clamp surface is pressed against the clamped member to press the clamped surface against the clamped member. This is a method of detecting a work gripping start point at a time when the clamp surface starts abutting against the member to be clamped in the hydraulic clamping device for clamping.
A method for detecting a work gripping start point in a hydraulic clamp device that detects a work gripping start point based on a pressure change of the working liquid with respect to a moving position of the piston. The hydraulic clamp according to claim 10, wherein the work gripping start point is a time point at which the pressure rise rate of the working liquid with respect to the moving position of the piston changes with the member to be clamped attached to the hydraulic clamp device. A method for detecting a work gripping start point in an apparatus. An equation showing the relationship between the moving position of the piston in the moving section of the piston, which is presumed that the clamp surface does not abut against the member to be clamped, and the pressure of the working liquid, and the clamp surface being the clamped surface. The claim that the solution of the simultaneous equation by the equation showing the relationship between the moving position of the piston and the pressure of the working liquid in the moving section of the piston estimated to come into contact with the member is set as the work gripping start point. 10. The method for detecting a work gripping start point in the hydraulic clamp device according to 10. The pressure change of the working liquid with respect to the moving position of the piston in the state where the clamped member is not attached to the hydraulic clamping device, and the movement of the piston in the state where the clamped member is attached to the hydraulic clamping device. The work gripping start point detecting method in the hydraulic clamp device according to claim 10, wherein the work gripping start point is detected from the pressure change of the working liquid with respect to the position. The method for detecting a work gripping start point in the hydraulic clamp device according to any one of claims 10 to 13, wherein the pressure of the working liquid is detected by a pressure sensor. The work gripping start point detecting method in the hydraulic clamp device according to any one of claims 10 to 13, wherein the pressure of the working liquid is detected from a measured value by a load cell that detects a load acting on the piston. A clamp member provided with a working liquid chamber inside and a piston for pressurizing the working liquid filled in the working liquid chamber are provided, and the clamp member defines the working liquid chamber on the inner surface side and is on the outer surface side. The wall body defines the clamp surface with, and the wall body is elastically deformed by the pressurization of the working liquid by the movement of the piston, and the clamp surface is pressed against the clamped member to press the clamped surface against the clamped member. In the hydraulic clamping device that clamps the A work gripping start point detecting device in a hydraulic clamping device that detects the work gripping start point based on a pressure change. The movement position of the piston at the work gripping start point detected by the work gripping start point detecting method in the hydraulic clamp device according to any one of claims 10 to 15 or the pressure of the working liquid is used as a reference. A work gripping method using a hydraulic clamping device that sets the gripping force of a member to be clamped. The hydraulic clamp device has a first piston that moves by pressing from the outside and a second piston that moves by screwing of an operating screw member provided on the clamp member.
The work gripping start point is detected by the movement of the first piston, and the gripping force of the clamped member is set by the movement of the second piston with reference to the pressure of the working liquid that has detected the work gripping start point. The work gripping method using the hydraulic clamp device according to claim 17.

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