JP2008105122A - Clamping force measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein it is utterly impossible to measure the clamping force generated by a clamping device for positioning and clamping an object to be clamped through a load cell in view of a positioning function and a load cell incorporating space. <P>SOLUTION: The clamping force measuring device has a measuring device main body, a fluid pressure cylinder mechanism provided in the measuring device main body and having a piston member mounting hole, a piston member mounted movably in the piston member mounting hole, and an annular fluid chamber in which the fluid pressurized by the piston member is sealed, and a fluid pressure measuring means for measuring pressure of the fluid in the fluid chamber. While clamping force acts on the piston member from a clamping force outputting part of the clamping device, pressure of the fluid is measured by the fluid pressure measuring means to measure the clamping force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a clamping force measuring device that measures a clamping force generated by a clamping device that can position a clamping object, and to a clamping force measuring device that can be applied to a clamping device in which it is difficult to measure the clamping force using a load cell. .

The workpiece to be used for machining is usually set on a work pallet, this work pallet is transported on the table of the machine tool, the work pallet is positioned on the table and clamped by the clamping device installed on the table side, The workpiece is machined.
In this kind of clamping device for fixing the work pallet, a ball lock type clamping device that has a positioning function for positioning the work pallet in two directions orthogonal to each other and clamps through a plurality of steel balls is widely adopted. Yes.

  For example, as disclosed in Patent Document 1, the above-described ball-lock type clamping device includes a clamp driving unit provided on the table side and a clamp passive unit provided on the work pallet side. . The clamp drive unit is movable to the outside in the radial direction through a main body member, a cylindrical shaft portion that protrudes upward from the main body member, a tapered cone that is movably attached to a lower portion of the cylindrical shaft portion, and a plurality of holding holes of the cylindrical shaft portion. A piston member including a plurality of steel balls mounted on the cylinder and a drive shaft portion movably inserted in the cylindrical shaft portion, a disc spring laminated body that clamps and drives the piston member downward, and a clamp release oil that raises the piston member It has a room.

  The clamp passive part is an engagement ring member provided at the lower part of the work pallet, a tapered engagement surface at the lower part of the center hole of the engagement ring member, and a part formed near the upper end of the center hole of the engagement ring member It has a cone-shaped taper receiving surface. The drive shaft portion includes a plurality of recesses for retreating a plurality of steel balls, and a plurality of inclined portions extending upward from the recesses for retraction. When setting the work pallet, the work pallet is lowered and the cylindrical shaft part is inserted into the center hole of the engagement ring in a state where the plurality of steel balls are retracted inward, and the drive shaft part is the disc spring laminate. Then, the plurality of steel balls are moved radially outward by the plurality of inclined portions of the drive shaft portion and engaged with the taper receiving surface to clamp the taper receiving surface downward. At this time, the taper engagement surface of the engagement ring is engaged with the taper cone for horizontal positioning, and the annular contact surface at the lower end of the engagement ring is brought into contact with the seating surface of the main body member in the vertical direction. Is positioned. Patent Document 2 also discloses a ball lock type clamping device that is substantially the same as described above.

  The ball lock type clamping device described in Patent Document 3 includes a clamp driving unit provided on the table side and a clamp passive unit provided on the work pallet side. The clamp drive unit includes a clamp body, a tapered cone protruding from the clamp body, a piston member movably mounted in the clamp body, and a plurality of movably held radially inward in a plurality of holding holes of the cylindrical rod portion of the piston member. Steel ball, an inclined guide surface formed on the peripheral wall portion where the cylindrical rod portion slides relative to each other, a hydraulic cylinder that clamps the piston member in the axial direction, and a disc spring that unclamps the piston member It has a laminate.

  The clamp passive part includes a socket member fixed to the work pallet, a taper socket formed on the socket member and engaged with the taper cone, and a pull stud protruding from the center hole of the taper socket. With the piston member held in the raised position and a plurality of steel balls retracted to the outside, the work pallet is lowered to engage the taper socket with the taper cone, and the hydraulic cylinder is operated to drive the piston member downward. Then, the plurality of steel balls are moved radially inward to engage with the pull stud, and the pull stud is pulled downward to be clamped. At this time, the positioning in the horizontal direction is performed by the engagement of the taper socket and the taper cone, and the positioning in the vertical direction is performed by bringing the lower end surface of the taper socket into contact with the annular seating surface of the taper cone.

  On the other hand, Patent Document 4 discloses a clamping device that clamps a tool on a spindle of a machine tool and a clamping force measurement device that measures a clamping force generated by the clamping device. This clamp device is composed of a draw bar arranged inside the main shaft, a disc spring laminated body for driving the draw bar to be clamped, and a ball lock type which is provided on the tip end side of the draw bar and engages / disengages the pull stud of the tool holder. It has an engagement / disengagement mechanism, an unclamping hydraulic cylinder attached to the rear end of the main shaft, and the like.

Clamping force measuring device is a load cell that is built into the rear end flange of the draw bar and receives unclamping force from the rod part of the hydraulic cylinder, a programmable controller that receives this load cell detection signal, and connected to the programmable controller to display the unclamping force A display device or the like. In this type of spindle clamping device, the tool holder flange is brought into contact with the tip of the spindle for positioning in the axial direction, and the taper shank of the tool holder is engaged with the taper fitting hole of the spindle. A clamp device of a type that performs positioning in a direction perpendicular to the axis by combining them is also widely adopted.
JP 2001-38564 A JP 2003-39264 A JP-A-8-155770 Japanese Patent Laid-Open No. 10-291105

The clamping devices disclosed in Patent Documents 1 and 2 are configured to generate a clamping force with a disc spring laminate, so that the elastic force of the disc spring laminate is attenuated and clamped during repeated use of the clamping device. Decreases. The plurality of steel balls are strongly driven radially outward by the boosting action of the inclined portion of the drive shaft portion, and press the taper receiving surface to clamp the work pallet.
Here, if the inclined portion of the drive shaft portion is worn or an indentation of a steel ball is generated on the inclined portion, the boosting factor of the boosting action is reduced. In addition, the clamping force also decreases when an indentation of the steel ball occurs on the tapered receiving surface on which the clamping force from a plurality of steel balls acts.

  As described above, when the clamping force of the clamping device for fixing the work pallet is lowered, the accuracy of machining the workpiece may be lowered. Therefore, there is a demand for periodically measuring the clamping force of the clamping device. Therefore, it is conceivable to employ a clamping force measuring device using a load cell in the clamping device as described in Patent Literatures 1 to 3, similarly to the clamping force measuring device of Patent Literature 4.

  However, in the case of a clamping device having a function of positioning a clamp object in two orthogonal directions as described in Patent Documents 1 to 3, the work pallet side contact surface in a state where the work pallet is positioned and clamped Therefore, it is essentially difficult to measure the clamping force for clamping the work pallet with the clamping device via the load cell. In order to incorporate the load cell, an installation space having a thickness of at least several mm is required, but it is extremely difficult to secure a space for installing the load cell. If the contact surface or seating surface is modified to incorporate the load cell, it cannot be used as a clamping device. In addition, the configuration in which the clamping force measuring device is incorporated in the clamping device is not preferable because the manufacturing cost of the clamping device is expensive.

  An object of the present invention is to provide a clamping force measuring device that can easily measure the clamping force of the clamping device without using a load cell, to provide a clamping force measuring device that can be attached to and detached from the clamping device, and the like.

  The clamping force measuring device according to claim 1 is a clamping force measuring device that measures a clamping force generated by a clamping device that positions and clamps an object to be clamped, and a measuring device main body that can be attached to and detached from the clamping device, A fluid pressure cylinder mechanism provided in the measuring device main body, wherein a piston member mounting hole, a piston member movably mounted in the piston member mounting hole, and an annular shape in which a fluid pressurized by the piston member is sealed A fluid pressure cylinder mechanism having a fluid chamber, and a fluid pressure measuring means capable of measuring the fluid pressure in the fluid chamber, wherein a clamping force is applied to the piston member from a clamping force output portion of the clamping device. The clamping force is measured by measuring the fluid pressure with the fluid pressure measuring means.

  This clamping force measuring device is not configured to measure the clamping force while the clamping device is in use, but can be measured by attaching the clamping force measuring device to the clamping device during maintenance of the clamping device. . When measuring the clamping force of the clamping device, if the clamping force is applied to the piston member of the fluid pressure cylinder mechanism of the clamping force measuring device from the clamping force output portion of the clamping device, the fluid enclosed in the annular fluid chamber by the piston member Is pressurized, the clamping force is measured by measuring the fluid pressure with the fluid pressure measuring means.

According to a second aspect of the present invention, there is provided a clamping force measuring apparatus according to the first aspect of the invention, further comprising a fluid pressure adjusting mechanism for adjusting an initial set pressure of the fluid sealed in the fluid chamber.
If the initial set pressure of the fluid sealed in the fluid chamber is adjusted to an appropriate pressure by the fluid pressure adjusting mechanism, the seal member of the fluid pressure cylinder mechanism is elastically deformed and becomes the same state as the seal member in the clamped state. The accuracy of measuring the clamping force is increased.

According to a third aspect of the present invention, there is provided the clamp force measuring device according to the first or second aspect, wherein the clamp device includes a clamp body, a cylindrical shaft portion projecting from the clamp body, and a plurality of cylindrical shaft portions formed on the cylindrical shaft portion. A plurality of steel balls that are movably held radially outward in the holding holes, a drive shaft member that is inserted through the cylindrical shaft portion so as to be movable in the axial direction and that can drive the plurality of steel balls radially outward, and this drive And a driving means for clamping the shaft member in the axial direction.
When clamping the clamping object with this clamping device, the cylindrical shaft part and the driving shaft member are inserted into the concave hole of the clamping object with the driving shaft member raised relative to the cylindrical shaft part. Then, when the drive shaft member is driven downward by the driving means, the plurality of steel balls are pushed outward in the radial direction and engaged with the object to be clamped, and a clamping force acts on the object to be clamped.

  According to a fourth aspect of the present invention, there is provided the clamp force measuring device according to the first or second aspect, wherein the clamp device includes a clamp body, a tapered cylindrical portion formed on the clamp body, and a piston movably mounted in the clamp body. A member, a plurality of steel balls movably held radially inward in a plurality of holding holes formed in a cylindrical rod portion of the piston member, and a peripheral wall portion of a clamp body on which the cylindrical rod portion slides relative to each other It is characterized by comprising a partial cone-shaped guide surface that is formed and guides a plurality of steel balls, and drive means that clamp-drives the piston member in the axial direction.

  When clamping the clamp object with this clamp device, the taper cylinder part and the cylindrical rod part of the piston member are connected to the socket member of the clamp object with the piston member raised relative to the taper cylinder part of the clamp body. When the piston member is driven downward with respect to the clamp body by the driving means while the taper tube portion is in close contact with the socket member, the plurality of steel balls are pushed radially inward and engaged with the object to be clamped. And clamp it.

  According to a fifth aspect of the present invention, the clamp device is a main shaft clamp device for clamping a cutting tool to a main shaft of a machine tool, and the main body of the measurement device is attachable to and detachable from a tool holder mounting hole on the front end side of the main shaft. It is characterized by being mounted. Therefore, the clamping force measuring device does not need to be incorporated in the main shaft, and can be mounted on the tip side portion of the main shaft to measure the clamping force.

  According to the invention of claim 1, the clamping force measuring device includes a measuring device main body and a fluid pressure cylinder mechanism, and a fluid chamber in which a fluid pressurized by the piston member is sealed. A fluid pressure cylinder mechanism and a fluid pressure measuring means capable of measuring the fluid pressure in the fluid chamber, wherein the fluid pressure measuring means applies the clamping force to the piston member from the clamping force output portion of the clamping device. Since the clamping force is measured by measuring the pressure, the clamping force is converted into fluid pressure, and the fluid pressure is measured by the fluid pressure measuring means to accurately measure the clamping force. Can do.

In particular, since the fluid chamber is formed in an annular shape, it is possible to employ a structure in which the clamping force output portion of the clamping device is inserted in the center of the piston member or a structure in which a pull stud on the piston member side is disposed. It becomes possible, and it becomes suitable for measuring the clamping force of the ball lock type clamping device. Moreover, since it is an annular fluid chamber, even if the clamping force acts on the piston member in an unbalanced manner, the clamping force can be accurately converted into fluid pressure, so that the clamping force measurement accuracy can be increased. .
Moreover, since the measuring device main body that can be attached to and detached from the clamping device is employed, the clamping force measuring device becomes independent from the clamping device, so that the clamping force of a plurality of clamping devices can be obtained using a single clamping force measuring device. Since measurement is possible, the manufacturing cost of the clamping device does not become expensive.

  According to the clamp force measuring device of claim 2, since the fluid pressure adjusting mechanism for adjusting the initial set pressure of the fluid sealed in the fluid chamber is provided, the initial set pressure of the fluid sealed in the fluid chamber is appropriately set. By adjusting the pressure to an appropriate pressure, the sealing force of the fluid pressure cylinder mechanism can be elastically deformed so that the clamping force can be measured in the same state as the sealing member in the clamped state, thereby improving the accuracy of the clamping force device. it can.

According to the clamping force measuring device of the third aspect, it is possible to reliably measure the clamping force of a ball lock type clamping device of a type in which a plurality of steel balls are pushed and moved radially outward.
According to the clamp force measuring device of the fourth aspect, it is possible to reliably measure the clamp force of a ball lock type clamp device that clamps by pushing a plurality of steel balls radially inward.

  According to the clamping force measuring device of claim 5, the clamping device is a spindle clamping device for clamping a cutting tool to a spindle of a machine tool, and the measuring device main body is attached to and detached from a tool holder mounting hole on the tip side of the spindle. Since it is structured to be mounted, this clamping force measuring device does not need to be incorporated in the main shaft, and can be mounted in a tool holder mounting hole on the tip side of the main shaft so as to be detachable and measure the clamping force. .

  A clamping force measuring device for measuring a clamping force for clamping a clamped object with a clamping device according to the present invention causes a clamping force to act on a piston member of a fluid pressure cylinder mechanism from a clamping force output portion of the clamping device, and to a fluid chamber. The clamping force is measured by measuring the fluid pressure of the fluid enclosed and pressurized by the piston member with the fluid pressure measuring means.

A clamping device 1 according to the present embodiment and a clamping force measuring device 2 that measures a clamping force generated by the clamping device 1 will be described with reference to FIGS.
First, the clamp device 1 will be briefly described.

  As shown in FIGS. 1 to 2, the clamping device 1 is a pull-type clamping device that attracts and fixes a work pallet P for attaching a workpiece to be machined to a table of a machine tool. Is composed of a clamp driving portion 1A provided on the table side and a clamp passive portion 1B provided on the work pallet P. The clamp drive unit 1A is provided in a radial direction in a clamp body 3 fixed to the table T, a cylindrical shaft part 4 integrally formed with the clamp body 3 and protruding upward, and a plurality of holding holes 5 of the cylindrical shaft part 4 A plurality of steel balls 6 held movably, a piston member 8 including a drive shaft portion 7 inserted into the cylindrical shaft portion 4 so as to be movable up and down, and an annular disc spring laminated body 9 mounted in an annular spring accommodating chamber. And a disc spring laminated body 9 that elastically biases the piston member 8 downward, an oil chamber 10 that applies hydraulic pressure to the piston member 8, and a hydraulic pressure supply that supplies and discharges hydraulic pressure to the oil chamber 10 from a hydraulic supply device (not shown). It has an exhaust port 11, an air blow mechanism (14-20), and the like.

  The drive shaft portion 7 is formed with a plurality of recesses 12 for retreating a plurality of steel balls 6 and a plurality of inclined recesses 13 extending upward from the recesses 12 for retraction. When the hydraulic pressure is supplied to the chamber 10 and the piston member 8 is raised relative to the cylindrical shaft portion 4, the plurality of steel balls 6 are partially retracted into the plurality of recesses 12 for retraction. When the shaft portion 4 does not protrude outward from the outer peripheral surface, and the hydraulic pressure of the oil chamber 10 is removed from the state and the piston member 8 is lowered by the elastic biasing force of the disc spring laminated body 9, a plurality of steel balls 6 are provided. Is pushed outward in the radial direction by the inclined concave portion 13 and partially protrudes outward from the cylindrical shaft portion 4 so that the engagement ring 28 on the clamp passive portion 1B side is clamped.

  An air blow mechanism for air-blowing the taper engagement surfaces 21 and 31 and air-blowing the annular contact surface 33 and the seating surface 22 includes air passages 14 and 15 to which pressurized air is supplied, and an air passage 16 in the piston member 8. -18, a plurality of air blow nozzles 19, a check valve 20, and the like. The steel ball of the check valve 20 is urged by a spring not shown. The air discharge mechanism for detecting the seating of the work pallet P includes air passages 14 and 15 to which pressurized air is supplied, a plurality of air discharge nozzles 23, and the like.

  A tapered engagement surface 21 having a smaller diameter is formed on the outer periphery of the lower portion of the cylindrical shaft portion 4, and the taper engagement of the annular engagement portion 32 of the engagement ring 28 on the work pallet P side is formed on the tapered engagement surface 21. By engaging the mating surface 31, the work pallet P is positioned in the horizontal direction. An annular seating surface 22 for receiving the annular contact surface 33 at the lower end of the engagement ring 28 and positioning the work pallet P in the vertical direction is provided at the upper end of the clamp body 3 on the outer peripheral side of the lower end of the taper engagement surface 21. Is formed.

  The clamp passive portion 1B on the work pallet P side includes an engagement ring 28 fitted and fixed with a shim 27 interposed in a concave hole 26 of the work pallet P, and a central hole formed in a central portion of the engagement ring 28. 29, a plurality of engaging recesses 30 formed in the vicinity of the upper end of the central hole 29 and capable of engaging with the plurality of steel balls 6, respectively, and a taper engagement that is an inner peripheral surface of the lower half of the central hole 29 Surface 31. In addition, the taper engagement surface 31 in this clamp passive part 1B and the annular engagement part 32 including the outer vicinity thereof are a taper ring 32a and a radial direction formed at equal intervals in the circumferential direction outside the taper ring 32a. It is configured to be elastically deformable radially outward through elastic deformation with the plurality of ribs 32b facing.

  When the work pallet P is fixed to the table T by the clamp device 1 as described above, as shown in FIG. 1, hydraulic pressure is supplied to the oil chamber 10 to switch the piston member 8 to the upper limit position and drive a plurality of steel balls 6. While the work pallet P is lowered in a state where it is partially retracted into the plurality of recesses 12 for retraction of the shaft portion 7, the engagement ring 28 is externally fitted to the cylindrical shaft portion 4. In parallel with the contact of the taper engagement surface 31 with the taper engagement surface 21 and the contact of the annular contact surface 33 with the seating surface 22, the oil pressure of the oil chamber 10 is released to allow the disc spring laminate 9 to be released. When the piston member 8 is lowered by the elastic urging force, the plurality of steel balls 6 are pushed outward in the radial direction by the plurality of inclined recesses 13 to engage with the plurality of engagement recesses 30 and the clamping force is applied to the engagement ring. 28, the work pallet P is clamped on the table T side It is fixed attracted to the body 3.

  The work pallet P is accurately positioned in the horizontal direction by the close contact of the taper engagement surfaces 21 and 31 through the elastic deformation of the annular engagement portion 32, and the work pallet by the close contact of the annular contact surface 33 and the seating surface 22. P is positioned accurately in the vertical direction, and the work pallet P is positioned and clamped in two orthogonal directions. In other words, the clamp device 1 is a two-surface constrained pull type clamp device.

Next, a clamping force measuring device 2 that measures a clamping force that clamps a clamping object (work pallet P) by the clamping device 1 will be described with reference to FIGS.
The clamping force measuring device 2 includes a measuring device main body 37, a hydraulic cylinder mechanism 38, a hydraulic pressure measuring device 40 capable of measuring the hydraulic pressure in an annular oil chamber 39 of the hydraulic cylinder mechanism 38, a hydraulic pressure adjusting mechanism 41, an air A drain valve 42 and a hydraulic pressure indicator 43 are provided.

  The hydraulic cylinder mechanism 38 includes a piston member mounting hole, a piston member 44 movably mounted in the piston member mounting hole, and an annular oil chamber 39 in which oil pressurized by the piston member 44 is enclosed. The measuring device main body 37 is configured as an annular block in which a vertical piston member mounting hole is formed at the center. The piston member mounting hole includes a lower-diameter small-diameter hole 45a and an upper-half large-diameter hole 45b. At the lower end of the measuring device main body 37, an annular contact surface 46 that contacts the annular seating surface 22 of the clamp drive unit 1 </ b> A of the clamp device 1 is formed.

  The piston member 44 includes a large-diameter piston portion 44a and a small-diameter rod portion 44b that is smaller in diameter than the piston portion 44a and extends downward (in the pull direction for attracting the work pallet P) from the lower end of the piston portion 44a. Is attached to the large-diameter hole 45b so as to be movable up and down, and the rod part 44b is attached to the small-diameter hole 45a so as to be movable up and down. The piston portion 44a and the clamp body 37 form an annular oil chamber 39 below the piston portion 44a, and the piston portion 44a can pressurize the oil enclosed in the oil chamber 39 and the oil passages 47a to 47c. The lower end of the rod portion 44 b is located above the annular contact surface 46. A seal member 48 that seals between the piston portion 44 a and the measurement device main body 37 and a seal member 49 that seals between the rod portion 44 b and the measurement device main body 37 are also provided.

  The piston member 44 is formed with an introduction hole 50 into which the cylindrical shaft portion 4 of the clamping device 1 can be introduced. The piston member 44 has an upper half of the cylindrical shaft portion 4 in the middle of the lower portion of the introduction hole 50. An annular inner collar portion 51 into which a portion can be introduced is formed, and a plurality of engagement recesses 52 into which a plurality of steel balls 6 can be engaged are formed on the upper portion of the annular inner collar portion 51. The engaging recess 52 is formed of an inclined partial cylindrical groove that becomes lower toward the center side. The ring member 53 on the upper side of the piston member 44 has a larger diameter than the piston member 44, is fixed to the clamp body 44 by screwing, and restricts the upper limit position of the piston member 44.

  The oil pressure measuring device 40 is fixed to the upper end portion of the measuring device main body 37 by screwing. The oil pressure measuring device 40 is supplied with oil pressure from the upper end portion of the oil passage 47c, and the oil pressure is measured by a built-in diffusion type semiconductor pressure sensor. Is measured. A hydraulic pressure indicator 43 formed of a small liquid crystal display is provided at the upper end of the hydraulic pressure measuring instrument 40. The hydraulic pressure measuring instrument 40 receives a signal from a pressure sensor, processes data, and controls the hydraulic pressure indicator 43. And an input / output interface.

  The hydraulic pressure adjusting mechanism 41 is for finely adjusting the initial set pressure of the hydraulic pressure sealed in the oil chamber 39 and the like. The hydraulic pressure adjusting mechanism 41 is sealed in the compression coil spring 54 and the oil chamber 39 and the like. A small-diameter piston 55 that can pressurize oil and is biased upward by a compression coil spring 54, a steel ball 56 above the small-diameter piston 55, and the small-diameter piston 55 through the steel ball 56 The operation member 57 has a position that can be finely adjusted. The operation member 57 is screwed into a screw hole of the measuring device main body 37. A tool is fitted into the hexagon hole of the operation member 57 and the operation member 57 is rotated. The position 57 is finely adjusted so that the initial set pressure of the oil sealed in the hydraulic chamber 39 or the like can be finely adjusted.

  The oil filling port at the end of the oil passage 47 a is sealed with a plug member 58, and the end of the oil passage 47 b is sealed with a plug member 59. An air vent valve 42 is also provided in communication with the oil passage 47c for venting the internal air when oil is filled from the oil filling port when the clamping force measuring device 2 is assembled.

Next, the operation and effect of the clamping force measuring device 2 will be described.
In the clamping force measuring device 2, the hydraulic pressure adjusting mechanism 41 is adjusted in advance to adjust the hydraulic pressure of the oil sealed in the oil chamber 39 or the like to an initial set pressure of several MPa (for example, 3 MPa). By applying this initial set pressure, the seal members 48 and 49 are sufficiently elastically deformed, and the oil pressure is filled in various minute gaps connected to the oil chamber 39. Therefore, when the clamping force is applied to the piston member 44 during the measurement of the clamping force, the clamping force can be accurately converted into an increase in hydraulic pressure.

  When the clamping force for clamping the work pallet P is measured by the clamp drive unit 1A of the clamp device 1, hydraulic pressure is supplied to the oil chamber 10 of the clamp drive unit 1A to hold the piston member 8 in the raised position, and a plurality of steels. The sphere 6 is partially retracted into the plurality of recesses 12 and held so as not to protrude outside the outer periphery of the cylindrical shaft portion 4. In this state, the clamping force measuring device 2 is lowered from above to introduce the introduction hole The drive shaft portion 7 and the cylindrical shaft portion 4 (corresponding to a clamping force output portion) are inserted into 50, and the annular contact surface 46 is seated on the seating surface 22.

  Next, before applying the clamping force, the hydraulic pressure measuring device 40 measures and stores the initial set pressure of the oil sealed in the oil chamber 39 and the like, and displays it on the hydraulic pressure display 43. Thereby, the initial set pressure can be checked. When the initial set pressure is insufficient, the operating member 57 of the hydraulic pressure adjustment mechanism 41 is operated to adjust the initial set pressure to an appropriate hydraulic pressure.

  Next, when the hydraulic pressure in the oil chamber 10 of the clamp drive unit 1A is released and the piston member 8 is lowered by the elastic biasing force of the disc spring laminated body 9, the plurality of steel balls 6 are pushed radially outward by the inclined recesses 13. It is moved and strongly engages with the plurality of engaging recesses 52 of the annular inner collar portion 51 to exert a downward clamping force on the piston member 44. As a result, since the piston member 44 pressurizes the oil sealed in the oil chamber 39 and the like, the oil pressure of the oil sealed in the oil chamber 39 and the like increases by an increase corresponding to the magnitude of the clamping force.

  Therefore, the hydraulic pressure of the oil sealed in the oil chamber 39 and the like is measured and stored by the hydraulic pressure measuring device 40 and displayed on the hydraulic pressure display 43. Further, the clamping force is calculated on the hydraulic pressure display 43 based on the hydraulic pressure increase corresponding to the clamping force and the clamping force calculation program stored in advance in the microcomputer. At this time, the hydraulic pressure indicator 43 displays the initial set pressure, the hydraulic pressure in the clamping force acting state, and the clamping force.

  Thus, since the clamping force generated by the clamping device 1 can be measured with high accuracy, the performance of the clamping device 1 can be confirmed, and for the clamping device 1 that cannot generate the desired clamping force, a disc spring laminated body is used. 9 and the seal member are replaced, and the unrepairable clamp device 1 is disabled.

  According to the clamping force measuring device 2, the clamping force can be accurately measured by converting the clamping force into an oil pressure and measuring the oil pressure with the oil pressure measuring device 40. In particular, since the piston member 44 is formed in a cylindrical shape and the oil chamber 39 is formed in an annular shape, a substantially cylindrical clamping force output portion (cylindrical shaft portion 4) of the clamping device 1 is formed at the center of the piston member 44. And a drive shaft portion 7) can be employed, which is suitable for measuring the clamping force of the ball lock type clamping device 1. In addition, since the annular oil chamber 39 is used, even if the clamping force acts on the piston member 44 in an unbalanced manner, the clamping force can be converted to hydraulic pressure with high accuracy. it can.

  Since the hydraulic pressure adjustment mechanism 41 for adjusting the initial set pressure of the oil sealed in the oil chamber 39 and the like is provided, the hydraulic pressure is adjusted by adjusting the initial set pressure of the oil sealed in the oil chamber 39 and the like to an appropriate pressure. The clamping force can be measured by elastically deforming the seal members 48 and 49 of the cylinder mechanism 38 or by filling the internal minute gap with oil under the same conditions as in the clamping state, thereby improving the accuracy of the clamping force measurement. Can do.

  In addition, since the measuring device main body 37 that can be attached to and detached from the clamp device 1 is employed and is configured to be attachable to and detachable from the clamp device 1, the clamp force measuring device 2 that is independent of the clamp device 1 is provided. Since the clamping force of the plurality of clamping devices 1 can be measured using the force measuring device 2, the manufacturing cost of the clamping device 1 does not become expensive. In addition, a contact surface 46 that contacts the seating surface 22 of the clamp driving unit 1A is formed on the measuring device main body 37, and the clamp force is measured in a state where the contact surface 46 is seated on the seating surface 22. The clamping force can be measured under the same conditions as those for clamping the object to be clamped at 1.

  Next, the clamp device 61 and the clamp force measuring device 62 according to the second embodiment will be briefly described with reference to FIGS.

First, the clamp device 61 will be described.
7 and 8, the clamp device 61 is a pull-type clamp device that attracts and fixes the work pallet P to the table T of the machine tool, and the clamp device 61 is a clamp drive provided on the table T side. It is comprised by the part 61A and the clamp passive part 61B provided in the work pallet P side. The clamp drive unit 61A includes a lower main body 63a and an upper main body 63b that form a clamp main body fixed to the table T.

  A piston member 64 is mounted inside the clamp body so as to be able to move up and down. The piston member 64 is strongly urged downward by a compression coil spring 65 and driven upward by hydraulic pressure supplied to the oil chamber 66. A plurality of steel balls 69 are movably mounted in the radial direction in a plurality of holding holes 68 formed in the vicinity of the upper end of the cylindrical rod portion 67 of the piston member 64. The cylindrical rod portion 67 is inserted into the cylindrical portion 70 of the lower main body 63a, and the piston member 64 is movable up and down with respect to the lower main body 63a. A partial cone-shaped guide surface 71 having a diameter decreasing downward is formed at the upper end portion of the cylindrical portion 70 of the lower main body 63a.

Inside the cylindrical rod portion 70 of the piston member 64, a steel ball restricting tool 72 made of a cylinder with an upper end wall is mounted so as to be movable up and down. The steel ball restricting tool 72 is urged upward by a compression coil spring 73, When the collar portion of the steel ball restricting tool 72 is locked to the stepped portion of the cylindrical rod portion 70, the upper limit position is reached.
A taper cylinder part 74 is formed on the upper main body 63b, and a taper engagement surface 75 having a smaller diameter toward the upper side is formed on the outer peripheral surface of the taper cylinder part 74. A horizontal annular seating surface 76 is formed on the outer peripheral side of the lower end of the tapered cylindrical portion 74.

Next, the clamp passive part 61B will be described.
The clamp passive portion 61B includes an engagement ring 82 that is fitted and fixed to the concave hole 80 of the work pallet P with a shim 81 interposed therebetween, and a lower portion that passes through the center hole of the engagement ring 82 and is fixed to the work pallet P. And a pull stud 83 projecting toward the top. The engagement ring 82 is formed with a taper engagement surface 84 that engages with the taper engagement surface 75 and an annular contact surface 85 that contacts the seating surface 76.

  When the work pallet P is fixed on the table T, as shown in FIG. 7, the piston member 64 is moved to the raised position, and the steel balls 69 are pushed outward by the steel ball restricting tool 72. Is partially protruded toward the guide surface 71 outside the outer peripheral surface of the cylindrical rod portion 67 and is held so as not to protrude inward from the inner peripheral surface of the cylindrical rod portion 67. In this state, the work pallet P is lowered to the clamping state shown in FIG.

  At this time, when the pull stud 83 is inserted into the cylindrical rod portion 67 from above and the hydraulic pressure of the oil chamber 66 is released and the piston member 64 is lowered by the elastic force of the coil spring 65, the plurality of steel balls 69 guide the guide surface 71. Due to the action, it moves toward the plurality of holding holes 68, engages with the pull stud 83, transmits a downward clamping force to the pull stud 83, and enters a clamped state. At this time, the work pallet P is positioned in the horizontal direction by the engagement of the taper engagement surfaces 75 and 84, and the work pallet P is positioned in the vertical direction by the contact between the annular contact surface 85 and the seating surface 76. That is, the clamp device 61 is a two-surface constrained pull type clamp device that positions and clamps the work pallet P in two orthogonal directions.

Next, the clamp measuring device 62 will be briefly described.
As shown in FIG. 9, the clamp measuring device 62 includes a measuring device main body 90, a hydraulic cylinder mechanism 91, a hydraulic pressure measuring device 93 capable of measuring the hydraulic pressure in the oil chamber 92 of the hydraulic cylinder mechanism 91, and the hydraulic pressure adjusting mechanism. 41 includes a hydraulic pressure adjusting mechanism (not shown) similar to 41, an air bleeding valve (not shown) similar to the air bleeding valve 42, a hydraulic pressure indicator (not shown) similar to the hydraulic pressure indicator 43, and the like. .

  The hydraulic cylinder mechanism 91 has a piston member mounting hole, a piston member 94 movably mounted in the piston member mounting hole, and an annular oil chamber 92 in which oil pressurized by the piston member 94 is enclosed. The measuring device main body 90 is configured as an annular block in which a vertical piston member mounting hole is formed at the center. The piston member mounting hole includes a small-diameter hole 95a in the lower half and a large-diameter hole 95b in the upper half. An annular contact surface 96 that contacts the annular seating surface 76 of the clamp drive unit 61 </ b> A of the clamp device 61 is formed at the lower end of the measurement device main body 90.

  The piston member 94 includes a large-diameter piston portion 94a and a small-diameter rod portion 94b that is smaller in diameter than the piston portion 94a and extends downward from the lower end of the piston portion 94a (in the pull direction for attracting the work pallet P). Is attached to the large-diameter hole portion 95b to be movable up and down, and the rod portion 94b is attached to the small-diameter hole portion 95a to be movable up and down. The piston portion 94a and the measuring device main body 90 form an annular oil chamber 92 below the piston portion 94a, so that the oil sealed in the oil chamber 92 and the oil passages 98a to 98c can be pressurized by the piston portion 94a. The lower end of the rod portion 94 b is located above the annular contact surface 96. A seal member 99 that seals between the piston portion 94a and the measurement device main body 90 and a seal member 100 that seals between the rod portion 94b and the measurement device main body 90 are also provided.

  The rod portion 94 b is formed in a cylindrical shape, and a taper engagement surface 101 that engages with the taper engagement surface 75 is formed on the inner peripheral surface of the cylinder portion, and the piston member 94 is formed at the center of the piston member 94. A pull stud 102 protruding downward is fixed.

  FIG. 9 shows a state in which the clamp force measuring device 62 is attached to the clamp drive unit 61A and is clamped. In this state, the taper engagement surfaces 75 and 101 are in close contact, and the annular contact surface 96 is in close contact with the seating surface 76. The piston member 64 is elastically biased downward by the coil spring 65, and a plurality of steel balls 69 are engaged with the pull stud 102 to exert a clamping force. Since the method of measuring the clamping force generated by the clamping device 61 using the clamping force measuring device 62 is the same as that of the first embodiment, the description thereof is omitted. Since the operation and effect of the clamping force measuring device 62 are substantially the same as those of the first embodiment, the description thereof is omitted.

  Next, the clamp device 111 and the clamp force measuring device 112 according to the third embodiment will be briefly described with reference to FIG. The clamp device 111 is a pull-type clamp device that is mounted on a main shaft 110 of a machine tool and that pulls and clamps a tool holder (not shown) attached to the tip of the main shaft 110 toward the main shaft 110.

  As shown in FIG. 10, a taper fitting hole 113 a into which a tool holder to which a tool is attached is formed at the tip (front end) side portion of the main shaft 110. The clamping device 111 includes a cylindrical shaft 113 incorporated in the main shaft 110 and formed with a taper fitting hole 113a, a draw bar 114 incorporated in the cylindrical shaft 113, and a rear (see FIG. 10 to the right) and a disc spring laminate 115 through which the draw bar 114 penetrates, and a tip end of the draw bar 114 as a pull stud (not shown) of the tool holder. This is a general spindle clamping device having a chuck mechanism 116 that is releasably connected, and a hydraulic cylinder means (not shown) for clamping that is provided on the rear end side of the spindle 110.

  When the tool holder is positioned and clamped by the clamping device 111, the taper shank portion of the tool holder is positioned in a direction orthogonal to the main shaft 110 by engaging with the taper fitting hole 113a, and the tool holder has a bowl-shaped portion. By positioning the rear end surface in contact with the front end surface (front end surface) of the cylindrical shaft 113, the main shaft 110 is positioned in the axial direction. That is, this clamping device 111 is also a two-surface constrained pull type clamping device that positions and clamps the tool holder in two directions orthogonal to the main shaft 110.

  As shown in FIG. 10, the clamping force measuring device 112 that measures the clamping force generated by the clamping device 111 includes a measuring device main body 120, a hydraulic cylinder mechanism 121 provided inside the measuring device main body 120, A hydraulic pressure measuring device 122 similar to the hydraulic pressure measuring device 40, a hydraulic pressure indicator, a hydraulic pressure adjusting mechanism, an air vent valve, and the like are provided. However, the hydraulic pressure indicator, the hydraulic pressure adjustment mechanism, the air vent valve, and the like are the same as those in the first embodiment, and are not shown.

  The measuring apparatus main body 120 is formed by integrally forming an annular block body 120a and a taper fitting portion 120b that is taper fitted into the taper fitting hole 113 of the cylindrical shaft 113. An annular contact surface 120c is formed on the rear end surface of the annular block body 120a so as to contact the seating surface 113b which is the tip surface of the cylindrical shaft 113 in the clamped state. The hydraulic cylinder mechanism 121 includes a piston member 123 movably mounted in a piston member mounting hole formed in the measuring apparatus main body 120, an annular oil chamber 124, and a rear end portion (back end portion) of the piston member 123. A pull stud 125 fixed at the joint, a closing member 126 for closing the end of the piston member mounting hole, and the like are included.

  The piston member 123 includes a large-diameter piston portion 123a and a smaller-diameter rod portion 123b. The rod portion 123b is formed behind the piston portion 123a (pull direction for attracting the tool holder). The piston member mounting hole has a cylinder hole 127a in which the piston portion 123a is mounted and a rod insertion hole 127b in which the rod portion 123b is mounted. The pull stud 125 is formed by integrally forming a pull stud main body 125a, a base shaft portion 125b, and a screw portion 125c, and the screw portion 125c is screwed into a screw hole in a rear end portion of the rod portion 123b of the piston member 123 to thereby form a base shaft portion. 125b is in contact with the rear end of the rod portion 123b. FIG. 10 shows a state in which the clamping force measuring device 112 is attached to the main shaft 110 and the draw bar 114 is connected to the pull stud 125 by the chuck mechanism 116 of the clamping device 111 to apply the clamping force.

  The piston portion 123a of the piston member 123 and the measuring device main body 120 form an annular oil chamber 124 on the rear side of the piston portion 123a, and oil is sealed in the hydraulic pressure 124 and the like. As in the first embodiment, the oil pressure of the oil sealed in the oil chamber 124 or the like can be measured by the oil pressure measuring device 122. When a backward clamping force is applied to the pull stud 125 of the clamping force measuring device 112 by the clamping device 111 of the main shaft 110, the hydraulic pressure of the hydraulic pressure 124 increases. Therefore, the hydraulic pressure should be measured as in the first embodiment. Can be used to measure the clamping force. Since the operation and effect of the clamping force measuring device 62 are substantially the same as those of the first embodiment, the description thereof is omitted.

  The clamp device and the clamp force measuring device are only three examples, but those skilled in the art will be able to use various pull-type clamp devices of two-sided restraint type without departing from the spirit of the present invention. Alternatively, the present invention can be applied to a clamping force measuring device that measures the clamping force of various pull-type clamping devices that are not two-surface constraining types.

It is sectional drawing of the clamp apparatus (unclamped state) of Example 1 of this invention. It is sectional drawing of the said clamp apparatus (clamp state). It is sectional drawing of the clamp force measuring apparatus (unclamped state) of Example 1. FIG. It is sectional drawing of the said clamp force measuring apparatus (clamp state). It is a perspective view of the said clamping force measuring apparatus. It is a top view of the said clamping force measuring apparatus. It is sectional drawing of the clamp apparatus (unclamped state) of Example 2. FIG. It is sectional drawing of the clamp apparatus (clamp state) of FIG. It is sectional drawing of the clamp force measuring apparatus (clamp state) of Example 2. FIG. It is sectional drawing of the clamp apparatus of Example 3, and a clamp force measuring apparatus.

Explanation of symbols

P Work pallet 1 Clamping device 2 Clamping force measuring device 3 Clamp body 4 Cylindrical shaft portion 5 Holding hole 6 Steel ball 7 Drive shaft portion 9 Belleville spring laminated body 10 Oil chamber 37 Measuring device body 38 Hydraulic cylinder mechanism 39 Oil chamber 40 Hydraulic pressure Measuring device 44 Piston member 45a Small diameter hole 45b Large diameter hole 61 Clamping device 62 Clamping force measuring device 63a Lower body (clamp body)
63b Upper body (Clamp body)
64 Piston member 65 Coil spring 66 Oil chamber 67 Cylindrical rod portion 68 Holding hole 69 Steel ball 71 Guide surface 90 Measuring device main body 91 Hydraulic cylinder mechanism 92 Oil chamber 93 Hydraulic measuring device 94 Piston member 95a Small diameter hole portion 95b Large diameter hole portion 111 Clamping device 112 Clamping force measuring device 120 Measuring device body 121 Hydraulic cylinder mechanism 122 Hydraulic measuring device 123 Piston member 124 Oil chamber

Claims (5)

A clamping force measuring device that measures a clamping force generated by a clamping device that positions and clamps a clamping object,
A measuring device main body detachable from the clamping device;
A fluid pressure cylinder mechanism provided in the main body of the measuring device, the piston member mounting hole, a piston member movably mounted in the piston member mounting hole, and an annular shape in which fluid pressurized by the piston member is enclosed A fluid pressure cylinder mechanism having a fluid chamber;
Fluid pressure measuring means capable of measuring the fluid pressure in the fluid chamber,
The clamping force is measured by measuring the fluid pressure with the fluid pressure measuring means in a state in which a clamping force is applied to the piston member from a clamping force output portion of the clamping device. Clamping force measuring device.   The clamp force measuring device according to claim 1, further comprising a fluid pressure adjusting mechanism for adjusting an initial set pressure of the fluid sealed in the fluid chamber.   The clamp device includes a clamp main body, a cylindrical shaft portion protruding from the clamp main body, a plurality of steel balls movably held radially outward in a plurality of holding holes formed in the cylindrical shaft portion, and a cylinder And a drive shaft member that is movably inserted in the axial direction in the shaft portion and capable of driving a plurality of steel balls radially outward, and a drive means that clamps the drive shaft member in the axial direction. The clamping force measuring device according to claim 1 or 2.   The clamp device includes a clamp main body, a tapered cylindrical portion formed in the clamp main body, a piston member movably mounted in the clamp main body, and a plurality of holding holes formed in a cylindrical rod portion of the piston member. A plurality of steel balls movably held radially inward, a partial cone-shaped guide surface formed on a peripheral wall portion of a clamp body on which the cylindrical rod portion slides relative to each other, and a piston member; The clamping force measuring device according to claim 1, further comprising: a driving unit that clamps the shaft in an axial direction.   The clamp device is a main shaft clamp device for clamping a cutting tool to a main shaft of a machine tool, and the measuring device main body is detachably mounted in a tool holder mounting hole on a tip side of the main shaft. The clamp measuring apparatus according to 1 or 2.

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