JPS6384833A - Automatic workpiece mounting device having variable clamp force - Google Patents

Abstract

PURPOSE:To make it possible to grip a workpiece with an optimum force, by providing a fluid circuit communicating a fluid pressure receiving section to a workpiece clamper, and a means for changing the pressure of accumulators in accordance with an external instruction signal. CONSTITUTION:An accumulator 90 has a cylinder 100 formed in its one end part with an adjusting screw 101 by which a spring retainer 102 is set at a predetermined position in the cylinder 100. Accumulators 90a, 90b are connected in parallel to a workpiece clamper hydraulic pipe line 84a through a high and low pressure change-over valve 86. The change-over valve 86 allows either one of the accumulators 90a, 90b to communicate with the pipe line 84a by pressing one of plungers 87a, 87b engaged with an actuating rod. Accordingly, the desired accumulators are selectively connected to the pipe line 84a by pressing the plungers 87a, 87b as necessary, thereby it is possible to change the gripping force for the workpiece by the workpiece clamper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a machining system in which a workpiece mounting table is sequentially exchanged between a machine tool and a stocker to machine the workpiece. On the side, workpiece mounting is related to a device at a workpiece setup station that attaches and detaches a workpiece to a table.

In particular, the present invention relates to an automatic workpiece mounting device with a variable clamping force that automatically clamps or unclamps a workpiece to a table using a workpiece clamper operated by fluid pressure.

[Conventional technology]

-i To attach or remove a workpiece from a table, first position the table at the workpiece setup station to install a workpiece that has a workpiece clamper operated by fluid pressure, and then connect a fluid pressure supply section to the table to attach a workpiece from the outside. The workpiece is attached to and removed from the table by loosening or tightening the clamper. For workpiece mounting, the fluid pressure supply section is disconnected from the table, and for workpiece mounting, the table is moved from the setup station to the machine tool. The workpiece clamper that has left the workpiece setup station is supplied with the fluid pressure accumulated in the accumulator built into the workpiece mounting table, and continues to hold the workpiece. After receiving the machining with the machine tool, the workpiece returned to the workpiece setup station is removed from the workpiece clamper and a new unprocessed workpiece is mounted there, as described above. During these operations, the gripping force of the workpiece clamper on the workpiece was always kept constant. In other words, the workpiece being machined needs to be gripped by the workpiece clamper with a gripping force that will not displace it from its mounting position due to the cutting force applied by the tool. A strong grip force was also set. However, if this gripping force is too strong, the workpiece may be deformed and the machining accuracy may be reduced. For example, in the case of finishing machining, it is necessary to perform precise machining, but the workpiece itself is deformed due to the strong gripping force, and this deformation is recovered immediately after being removed from the workpiece clamper after machining, resulting in the desired accuracy. In addition, in the case of thin-walled workpieces, a weak gripping force is required from the rough machining stage. In this way, it is necessary to minimize the amount of distortion of the workpiece by changing the gripping force by the workpiece clamper depending on the shape and dimensions of the workpiece and the progress of processing.

[Means for solving problems]

The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional workpiece mounting device, and to make the fluid pressure from the accumulator supplied to the workpiece clamper variable, thereby making it possible to suitably select the gripping force for the workpiece. Automatic workpiece mounting is what provides the device. This makes it possible to change the workpiece gripping force of the workpiece clamper to an optimal state depending on the machining situation.

The above purpose is an automatic workpiece mounting device that uses fluid pressure to attach a workpiece to a workpiece mounting tool at a workpiece setup station in a machining system. A workpiece mount having a workpiece clamper operated by fluid pressure is provided on the table, and the workpiece holder is provided with a workpiece clamper that is exchanged between the workpieces and the table, and the workpiece mount has a workpiece clamper operated by fluid pressure. a fluid pressure receiving section that engages with the pressure supply section; a fluid circuit that communicates from the fluid pressure receiving section to the workpiece clamper within the work mounting table; and a fluid circuit that is provided in the middle of the fluid circuit, and the work mounting section is provided when the work mounting table is connected to the workpiece setup station. The accumulator is equipped with an accumulator that backs up fluid pressure when the supply of fluid pressure is cut off due to movement and whose backup pressure is variable, and a pressure changing means that changes the pressure of the accumulator in accordance with an external command. Automatic workpiece mounting with variable clamping force is achieved by the device.

Other objects and effects will become clearer from the following preferred embodiments of the invention.

〔Example〕

First, the positional relationship between the work setup station WSS and the machine tool according to the present invention will be explained with reference to FIG. The workpiece setup station WSS is installed with a pallet changer 19 sandwiched between the front bed 3 and the stocker 1 on the front side of the machine tool 2, and the workpiece consisting of a pallet 6a and a tombstone 7 fixed to its upper surface is mounted on the stand. A taper cone 5 provided on a swivel base on the stocker 1 is fitted into a taper hole on the lower surface of the pallet 6a to detachably hold it in a predetermined position. A work clamper (not shown) for removably fixing the work 8 is installed on the side surface of the tombstone 7. At this work setup station WSS, an unprocessed work is attached to the side of the tombstone 7 and is waiting. When replacing the pallet, the two pairs of changer arms 9, which were waiting oriented in the X direction, move 90 degrees in the Y direction when replacing the pallet, as shown in FIG. It gets under the upper pallet 6a and the pallet 6b on the table 10 of the front bed 3 and lifts them up.

Then, it is rotated 180 degrees in a horizontal plane with respect to the central axis, and the parefs 6a and 6b are replaced and placed. At the workpiece setup station WSS, the workpiece on the pallet 6b is removed and a new workpiece is mounted again. On the other hand, the table 10 can be moved on the front bed 3 in the horizontal plane in the X direction (in the direction perpendicular to the plane of the paper in FIG. 2) by a drive means (not shown), and the column 12 of the machine tool 2 can be moved on the rear bed 13 in Z in the horizontal plane by the axial remoter 14
The main shaft 15 attached to this column 12 is further movable in the Y direction (vertical direction in FIG. 2) by a Y transport remoter 16. Therefore, the tool 11 gripped and fixed on the tip of the main shaft 15
are these X, Y.

The movement in the Z direction makes it possible to perform desired cutting on the workpiece 8 placed on the pallet 6a on the table 10. The upper part of the table 10 can be rotated and indexed in a horizontal plane (not shown), and the workpieces 8 on each side of the tombstone 7 on the pallet 6a can be sequentially indexed toward the main shaft 15 and processed. When the processing of the workpiece 8 is completed, the arm 9 of the pallet changer 19 is operated again and the above-mentioned operation is repeated.

Next, the configuration of the work setup station WSS according to the present invention will be described.

In FIG. 1, the setup station WSS includes a swivel table 21 that is rotatably attached to the top of the pace 4 fixed on the floor via legs 26 and is rotatable about a vertical axis. Four taper cones 5 protrude at equal angular positions on the upper surface of the swivel table 21, and the pallet 6 is fitted with taper holes 5a drilled at corresponding positions on the lower surface thereof. It is placed. A four-sided tombstone 7 having a rectangular parallelepiped outer shape is integrally fixed to the upper surface of the pallet 6 with bolts or the like.

Workpiece attachment means for holding the workpiece 8 in a predetermined posture are installed on each of the four sides of the tombstone 7. The workpiece mounting means is a fixture plate 23 fixed at a predetermined position on each side of the tombstone 7 with bolts 22, extending horizontally and vertically.
A workpiece clamper 25a comprising two edge locators 24a, 24b and an actuating rod that operates perpendicularly to the direction of extension of the respective edge locators 24a, 24b to press the workpiece 8 against the edge locators 24a, 24b.
, 25b, and work 8 to fixture plate 2
Two workpiece clampers 2 for pressing against the surface of 3
It consists of 5c and 25d. The workpiece 8 is transported by a robot or the like (not shown) from a workpiece storage shelf (not shown) adjacent to the workpiece setup station WSS to the vicinity of one side of the tombstone 7, and is first moved against the horizontal edge locator 24a by the action of the workpiece clamper 25a. Then, by the action of the workpiece clamper 25b, the workpiece is positioned relative to the vertical edge locator 24b, and finally, the workpiece clamper 25C, 25d is used to position the workpiece so as not to lift it off the fixture plate 23, and fix it in a predetermined position. Ru. Once the workpiece has been installed on one side, the workpiece installation table is rotated 90 degrees around the vertical axis to face the new side into the robot's work area, and the above process is repeated to install the new workpiece. It will be done. This operation is performed sequentially on all sides of the tombstone 7.

Next, to mount the workpiece mentioned above, move the table at a predetermined angle (9 in this example).
The mechanism for turning the camera (in 0 degree increments) will be explained. As shown in FIG. 1 and FIG.
is placed on the annular rim 21a, and four rollers 31 and 32 are installed at equal angles on the annular rim 21a to engage and contact the top and side surfaces of the annular rim 4a of the base 4, thereby causing the rim 4 to
It is rotatable along a. Here roller 31
supports the vertical load acting on the swivel base 21, and the roller 32 supports the radial load acting on the swivel base 21. Four notches 33 are provided on the inner peripheral surface of the annular rim 21a of the swivel base 21 at exactly equal angles.

On the other hand, a motor 34 is fixed in the internal space of the base 4 with its output shaft facing vertically upward, and a pinion 34 is attached to the tip of the motor 34.
5 is installed. The binion 35 is configured to mesh with an internal gear 36 fixed along the inner circumference of the swivel base 21, and when the pinion 35 is rotated by the motor 34, the swivel base 21 is rotated via the internal gear 36. A cylinder 37 is positioned and fixed inside the base 4 so that an index roller 38 provided at the tip of its operating rod is directed toward the inner circumferential surface of the swivel base 21 . The index roller 38 is inserted into the notch 33 when the swivel base 21 is stopped.
It has a function of fitting into the swivel base 21 and holding the swivel base 21 in a fixed position. With this configuration, when it is necessary to turn the swivel table 21 by 90 degrees in order to attach or detach a workpiece to a new side surface of the tombstone 7, an actuation signal for retracting the actuating rod from the control device (not shown) is issued to the cylinder 37. The index roller 38 retreats and escapes from the notch 33, and an activation signal is sent to the motor 34, so that the swivel base 21 moves approximately 1/4
Then the cylinder 37 is given an actuation signal again, and the actuating rod moves forward to push the index roller 38 into the next notch 33 facing it, during which the motor 34 moves the swivel base 21. If the minute rotation is not accurate, the swivel base 21 is naturally displaced and indexed to the correct position under the action of the component force exerted on the index roller 38 by the forward movement of the actuating rod.

In order to attach and detach the work 8, the work clampers 25a~
The pressurized fluid that operates 25d is supplied from a conduit connected to a fluid pressure supply source extending through the hollow interior of the base 4 via a conduit provided on the workpiece clamper side.
As mentioned above, the work mounting table consisting of the tombstone 7 and the pallet 6 must be reciprocated between the work setup station WSS and the table 10 on the front bed 3 of the machine tool by the pallet changer 19. Even in the workpiece setup station WSS, 1/4 rotation is repeated in order to attach the workpiece to each side of the tombstone 7, so this fluid pressure supply pipe is secured between the base 4 and the workpiece mounting table. It is necessary to be configured so that it can be detached. Next, this binding/detachment mechanism will be explained.

Inside the tombstone 7, a large number of piping for pressurized fluid are arranged in sets of four workpiece clampers 25a to 25d installed on each side, and as shown in FIG. The end of the pipe fitting plug 40 protrudes downward from the bottom of the tombstone 7 toward a through hole provided in the center of the pallet 6. These 40 plugs 40 are thrown for each set of work clampers, for a total of 40 plugs.
(2 pipes each x 4 sets = 8 pipes) for supplying and returning pressurized fluid to each of the pipes. A pipe (one pipe) is used to replenish pressurized fluid to an accumulator for supplying a predetermined fluid pressure.The installation of the workpiece 8 on the side of the tombstone, which will also be described later, is for pressurized air used for posture checking. pipe, (1
(books) correspond to each. On the other hand, a vertically movable cylinder 41 is vertically fixed to the lower surface of the bottom wall of the base 4 with an operating rod 41a facing upward, and a holder 42 is attached to the tip of the rod 41a. A socket block 43 having a pipe fitting socket 45 fixed upwardly is loosely fitted into the upper part of the holder 42. A flexible rubber hose 44 is connected to the lower part of the socket block 43 and communicates with the socket 45, and extends to a pressurized fluid source (not shown). These sockets 45 are connected to the respective plugs so that workpieces can be sequentially attached and detached in correspondence with the set of plugs 40 attached to the workpiece clamper set that has occupied the workpiece attachment/detachment position by minute rotation of the swivel base 21. Only one set, ie, 10 pieces, are arranged on the same axis as 40.

Ten rubber hoses 44 are also provided, one corresponding to each socket 45. When the cylinder 41 is operated and its operating rod 41a is raised, each socket 45 is moved to its corresponding plug as shown by the phantom line. 40 is fitted. During this upward movement, the holder 42 slides through a through hole provided in a portion of the holder 42 through a bush 47 onto a pair of guide lofts 46 vertically erected with their lower ends supported by the bottom wall of the base 4. You will be guided around. The upper end of this guide rod 46 is held in a hole similarly provided in a part of the base 4 via an O-ring 48 so as to be able to swing about ±1 day. Further, the working loft 41a and the holder 42 are attached through a spherical washer 49, and the holder 42 is rotatably movable. Furthermore, the attachment between the socket block 43 and the holder 42 also allows for free movement of approximately ±1 in two horizontal axes directions. Accordingly, these flexible mountings allow some flexibility in the movement of the holder 42 by law. This flexible connection means allows each workpiece clamper provided corresponding to each side of the tombstone 7 used in the machining system to be used during centering operation using the centering pin 61 and the centering hole 62, which will be described later. set of plugs 40
Errors in position and angle between the socket 45 and the set of sockets 45 of the work setup station can be easily absorbed. Note that 28 and 29 are a limit switch for detecting a rise and a limit switch for detecting a fall, respectively, for confirming that the lifting and lowering operation of the holder 42 is completed.

Next, the fitting mechanism between the plug 40 and the socket 45 will be described in detail. These pipe fittings are self-sealed to prevent leakage of pressurized fluid when disconnected, and have a mechanism that automatically communicates when connected. 6th
As shown in the figure, in the socket 45, an inner cylinder 51 is slidably inserted into an outer cylinder 50, and a fixing rod 52 is further provided passing through the inner cylinder 51 in the axial direction. Fixed rod 5
The lower threaded part of No. 2 has a hole snap ring 50 in the outer cylinder 50.
penetrates a collar 52b regulated in the axial direction by a;
It is tightened to the collar 52b with a nut 52c. Therefore, the fixed rod 52 is immovable relative to the outer cylinder 50.

The inner cylinder 51 is connected to the opening 54 of the outer cylinder 50 by a spring 53.
The piston rod 52 is biased toward the side (upward in FIG. 6), thereby tightly engaging the gasket 55 fixed to the periphery of the tip with the large diameter portion 52a at the tip of the piston rod 52. Further, 56 is an O-ring installed between the inner and outer cylinders. With this configuration, the pressurized fluid supplied from the rubber hose (not shown) connected to the base of the outer cylinder 50 is
It passes through the inside of the outer cylinder 50 and the inner cylinder 51 and reaches the tip thereof, where it is self-sealed by the large diameter part 52a of the piston rod 52 to prevent leakage to the outside. On the other hand, the plug 40 has a piston rod 59 built therein so as to be slidable in the axial direction inside a cylindrical body 58 having a flange 57a with a tip opening 57 projecting inward. The piston rod 5
9 is guided through the cylindrical body 58 through a collar 58b which is regulated upward by a hole snap ring 58a, and is urged toward the tip opening 57 by a spring 60. This biasing force causes the large diameter portion 59 at the tip of the piston rod 59 to
a is tightly engaged with the inner surface of the flange 57a via a packing 59b. With this configuration, the pressurized fluid in the pressurized fluid conduit on the tombstone side connected to the base of the cylinder 58 passes through the inside of the cylinder 58 and reaches the tip opening 57, where the large diameter of the piston rod 59 is detected. The diameter portion 59a is self-sealed to prevent leakage to the outside. The above is an explanation of the self-sealing mechanism when both pipe joints are separated.

The inner diameter of the opening area of the outer cylinder 50 of the socket 45 is large enough to receive the top head of the cylinder 58 of the plug 40, and the flange 57a of the cylinder 58 is approximately the same as the top of the socket 45. have the same diameter. Therefore, as shown in FIG. 7, when the cylindrical body 58 of the plug 40 is inserted into the outer cylinder 50 of the socket 45, the cylindrical body 58 resists the urging force of the spring 53 and causes the inner cylinder 51 to retreat. Since the large diameter portion 52a of the fixed rod 52 is manufactured to have a smaller diameter than the opening 57 of the cylindrical body 58, as the cylindrical body 58 moves inside the socket while retracting the inner cylinder 51, the inside of the cylindrical body 58 conversely increases. The piston rod 59 on the plug side is moved backward against the biasing force of the spring 60. Through these series of operations, the large diameter portions 52a, 59a of both piston rods 52.59
The sealing action of is released, allowing pressurized fluid to flow between both pipe joints.

In order to smoothly perform the above-mentioned fitting operation between pipe fittings,
In the present invention, the socket block 43 is provided with a pair of centering pins 61 along with the socket 45, and a centering hole 62 corresponding to the plug 40 is also provided on the right side for mounting the workpiece.

With this configuration, when the socket block 43 rises, the centering pin 61 first enters the hole 62, and its tapered tip allows the two pipe joints to fit together accurately while self-correcting some positional errors.

During this fitting operation between the two pipe joints, a considerably large lifting force acts on the workpiece mounting table, and the workpiece mounting table tends to lift off from above the base 4.

A clamping device described below is provided to counteract this force. In FIG. 5, the left side of the center line shows the locked state, and the right side shows the unlocked state.

As shown in the figure, this device consists of a pair of L-shaped clamp levers 71, one end of which is rotatably pivoted at the top of the base 4, and when pivoted upward (as shown in FIG. On the left side), the other end of the hook shape is in locking contact with a locking step 72 provided annularly on the inner circumferential surface of the pallet 6 to lock it from rising, and when it rotates downward ( The right side in Fig. 5) is configured to release the lock.

This locking/unlocking operation is performed in conjunction with the lifting/lowering movement of the holder 42 of the socket block 43. That is, a pressing block 73 is fixed to a part of the holder 42, and a pressing pin 75, which is biased outwardly by a compression spring 74 and whose tip slightly protrudes outside the pressing block 73, is housed in its hollow interior. There is. The pressing block 73 and the pressing pin 75 are arranged at a position where they can come into secure contact with the back surface of the lever 71. When the pipe joint is disconnected with the holder 42 in the lower position, it is in the unlocked state shown on the right side of FIG. 5, and the lever 71 is supported so as to rest on the upper surface of the pressing block 73. When the holder 42 holding the socket 45 starts to rise in order to connect both pipe joints, the upper surface of the press block 73 and the sloped part 73a following it rise while contacting the back surface of the lever 71.
The lever 71 is gradually pushed up and rotated (counterclockwise on the left side in FIG. 5), and its tip is engaged with the locking step 72. When the fitting of both pipe joints is completed, a pressing force is further applied to the back of the lever 71 by the action of the pressing pin 75 to completely lock it. Conversely, when the holder 42 is lowered from this state, the lever 71 rotates in the opposite direction in the reverse order as described above, the locked state between the holding step 72 is released, and the workpiece is mounted between the table and the base 4. There is a free state between. This mechanism locks the mounting of the workpiece so that it does not come off the base 4 at the same time as the fitting operation of the pipe joints, and also assembles the workpiece at the same time as the disconnection operation.

The work setup station of the present invention further includes a mechanism for checking the posture of the work 8 attached to each side of the tombstone 7. This checking mechanism is performed using pressurized air supplied from one of the fluid pressure supply pipes mentioned above. That is, as shown in FIG. 8, this pressurized air pipe 80 branches and opens facing the workpiece 8 through a gap provided between each edge locator 24a, 24b and the fixed chair plate 23. . Therefore, if work 8
If the workpiece 8 and the edge locator 24 are not held in the correct posture on the fixture plate 23,
a, 24b or the fixture plate 23, and the pressurized air leaks through this, reducing the back pressure in the piping. The system is configured to detect this pressure drop with an appropriate sensor and issue an alarm to prevent accidents caused by mistakes.

Next, regarding workpiece mounting, the accumulator 90 built into the table and the associated fluid pressure supply circuit will be explained. As mentioned above, when the fluid pressure supply section provided at the work setup station WSS and the piping to the work clampers 25a to 25d are disconnected, the accumulator continues to supply fluid pressure to the latter. It has a function to continue gripping the workpiece.

FIG. 9 shows a plan view of the inside of the tombstone 7 with the top M1a removed. In the center of the inside of the tombstone 7, there is a plug 40 of piping for supplying fluid pressure to the work clampers on the four sides. are shown in four sets of 10 each, for a total of 40 (each set is surrounded by a chain double-dashed line to make the drawing easier to understand).

There are a total of four centering holes 62 between each pair of plugs.
It is provided at equal angle positions. All of these are fixed to the tombstone 7, so when the workpiece is mounted, when the table is indexed at 90 degrees and rotated, each set of plugs 40 and centering holes 62 will also rotate accordingly, and new ones will be installed one after another. occupy a position. One of these positions is a position that can be engaged with the socket 45 described above. Therefore, the pair of centering holes 62 that happen to occupy the lockable position fit into the pair of centering pins 61. A plunger 82 is inserted into each centering six 62 to open and close an accumulator circuit cutoff valve 81 for each set of workpiece clampers. On the other hand, when one of the pair of centering pins 61 engages with the centering hole 62, it pushes up the plunger 82 and causes the accumulator circuit disconnection valve 8
1, the workpiece clamper on the side of the tombstone, which assumes the indexing position when the two engage, is cut off from the accumulator and is instead connected to the fluid pressure supply circuit pipe of the base 4, as will be described later. supply. As long as the plunger 82 of the intermittent valve 81 is not pressed by the centering bin 61, fluid pressure from the accumulator 90 acts on the workpiece clamper. Here, the other of the pair of centering bottles 61 is hollow, and when it is fitted into the centering bottle 62, the plunger 82 enters the hollow part and does not operate the shut-off valve 81, but only works as a fluid pressure supply part. Performs only centering action with the fluid pressure receptor.

Fig. 10 shows an example of the fluid pressure supply piping circuit to the workpiece clampers. Fig. 10 shows a circuit leading to one set of workpiece clampers on the first side of the tombstone 7; The circuit is also connected in parallel to this.

What is shown at the bottom of the figure are the ten sockets 45 provided on the base 4 side, and the hydraulic oil pipes include a reciprocating pipe 84a for supplying and returning fluid pressure for each workpiece clamper; 84b are paired and configured to be switchable by the directional switching valve 83, and the supply side pipe 84a is connected when a workpiece is being gripped, and the return side pipe 84b is connected when the workpiece is released. The pipe 84C is used to supply fluid pressure to an accumulator 90, which will be described later. Regarding the pressurized air piping 80, a compressor 8 that is a pressurized air source is provided on the base side.
5, and there is a back pressure drop detection sensor 8 in the middle of the pipe.
6 is installed. As described above, this sensor 86 is used to check the posture of the workpiece.

In the illustrated state in which the socket 45 and the plug 40 are disconnected, the hydraulic fluid pressure is supplied from the accumulator 90 to the work clampers 25a to 25d. This makes it possible to continue to reliably grip the workpiece even when the workpiece mounting table is removed from the workpiece setup station and transferred to the machine tool side. Next, at the work setup station, when the socket and plug are connected by the aforementioned locking operation, fluid pressure is directly applied to the workpiece clamper 25 through the socket-plug connection.
a to 25d. At the same time, the accumulator circuit disconnection valve 81 is switched under the action of the centering bin 61, cutting off fluid pressure from the accumulator. However, this switching is performed only for the work clamper on the first surface, and the fluid pressure from the accumulator continues to be supplied to the work clampers on the other surfaces. By operating the direction switching valve 83 in this state, it becomes possible to attach and detach only the workpiece on the first surface.

Furthermore, in the illustrated embodiment, two types of accumulators 90 are installed: one for high pressure 90a and one for low pressure 90b. As mentioned above, the reason for this is that the workpiece being machined needs to be gripped by the workpiece clamper with such gripping force that it will not be displaced from its mounting position due to cutting resistance. However, if this gripping force is too strong, the workpiece will be deformed, and if the workpiece is unclamped after machining, the desired accuracy may not be achieved. That is, it is desirable that the workpiece be gripped with the minimum necessary force that does not cause such deformation. However, this suitable gripping force varies depending on the progress of machining the workpiece, and in the case of rough machining, it is not necessary to have such precision, but rather it is desirable to grip with a strong gripping force to withstand large cutting forces. On the other hand, in the case of finishing machining, the cutting force is small and machining accuracy is required, so a weak gripping force is desirable. Two types of accumulators, ie, a high pressure accumulator 90a and a low pressure accumulator 90b, are provided so that this gripping force can be used properly, and are configured to be switchable depending on the situation.

This will be explained below.

As shown in FIG. 10, both accumulators 90a.

90b are connected to the work clamper pressure oil pipes 84a in parallel with each other via a high/low pressure switching valve 86. The switching valve 86 closes the accumulator 90a by pushing either of the two plungers 87a, 87b that engage its actuating rod.

It has a function of communicating one of the pipes 90b with the pipe 84a and blocking the other. Therefore, by pressing the plunger 87 as necessary to selectively communicate a desired accumulator with the pipe 84a, it is possible to change the gripping force of the workpiece by the workpiece clamper. As shown in the figure, limit switches 88a and 88b are installed to sense the operation of each of the plungers 87a and 87b, and a signal from this is provided in the fluid pressure supply piping 84c to the accumulator on the base 4 side. The pressure is transmitted to the high pressure/low pressure setting valve 89.

The setting valve 89 receives this signal and changes the fluid pressure supplied to the pipe to match that of the selected accumulator, so that the next time the socket 45 of the fluid pressure supply section and the plug 40 of the fluid pressure receiving section are engaged. When this happens, a predetermined fluid pressure is supplied to the accumulator. Plunger 87a or 8 for switching high and low pressure switching valve 86
The operation of pushing in 7b may be performed by a workpiece exchange robot at the workpiece setup station, or may be performed by an operator. Furthermore, on the machine tool side, it is also possible to perform relative movement between the main spindle and the workpiece based on an NG command.

Next, the internal structure of the accumulator 90 will be explained.

As shown in FIG. 10, the accumulator 90
An adjustment screw 101 is provided at one end of the cylindrical body 1oo, thereby allowing the spring receiver 102 to be set at a predetermined position inside the cylindrical body 1oo. Also, inside the cylinder 100 is a piston 103.
is slidably installed along the inner wall, is introduced from an inlet boat 104 provided at the other end of the cylindrical body 100, and is pushed upward by fluid pressure. The spring receiver 10
A compression spring 105 is interposed between the piston 103 and the piston 103, and urges the piston 103 downward. With this configuration, when fluid pressure is introduced into the cylindrical body 100 from the inlet boat 104, the piston 103 is pushed upward and compresses the compression spring 105, thereby balancing its biasing force with the fluid pressure.

Therefore, even if the plug 40 is removed from the socket 45 and the fluid pressure supply source is disconnected, the fluid pressure in the pipe connected to the inlet port 1o4 is maintained at its original value.

It is possible to change the set pressure by adjusting the adjusting screw 101.

In the illustrated embodiment, two accumulators for high pressure and low pressure are provided and used by switching between them as appropriate, but only one accumulator is provided and the set pressure can be changed as necessary as described above. You can also get the same effect.

〔Effect of the invention〕

As described in detail above, according to the present invention, the fluid pressure supplied from the accumulator to the workpiece clamper can be arbitrarily selected and/or set, so that it can be optimized depending on the shape and dimensions of the workpiece and the progress of machining. It has become possible to grip the workpiece with a strong gripping force, and machining accuracy has been dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an embodiment of the work setup station according to the present invention, FIG. 2 is a side view showing the positional relationship between the work setup station and the machine tool, and FIG. 3 is a side view showing the operation of the pallet changer. m in figure 2
4 is a cross-sectional view taken along line IV-IV in FIG.
6 is a side sectional view showing the state of the pipe joint in the self-sealing state; FIG. 7 is a side sectional view showing the state of the pipe joint in the communicating state; Figure 8 is a side view showing the air piping for checking the posture of the workpiece, Figure 9 is a plan view of the device with the top cover of the tombstone shown in Figure 1 opened, and Figure 10 is the workpiece clamper. 1 is an example of a fluid pressure supply circuit for the. 1--Stocker 4-Base 6--Pallet 7--Tombstone 21--Swivel base 24a, 24b-Edge locator 253-25d-Work clamper 40--Plug 45--Socket 42-- -Holder 43--Socket block 61-Centering pin 62-Centering hole 86-Height/lower switching valve

Claims (1)

[Claims] 1. An automatic workpiece mounting device that uses fluid pressure to attach a workpiece to a workpiece fixture at a workpiece setup station in a machining system, which is used to position and place a workpiece on a machine tool and setup station, or to use a transport device. A workpiece mounting table having a workpiece clamper which is exchanged between the workpieces and is operated by fluid pressure, and which is provided on the workpiece mounting table to supply fluid pressure when the workpiece mounting table is positioned and placed on the workpiece setup station. a fluid pressure receiving part that engages with the workpiece clamper; a fluid circuit that communicates from the fluid pressure receiving part to the workpiece clamper within the workpiece mounting base; A clamping force comprising an accumulator that backs up fluid pressure when the fluid pressure supply is cut off and whose backup pressure is variable, and a pressure changing means that changes the pressure of the accumulator in accordance with an external command. Variable automatic workpiece mounting device. 2. The accumulator is comprised of at least two accumulators, a high-pressure accumulator and a low-pressure accumulator, and the supply of fluid pressure from each accumulator is switched by a command from the pressure changing means. Automatic workpiece mounting device with variable clamping force. 3. The pressure changing means includes two plungers protruding from the workpiece mounting surface of the workpiece mounting base. When one of the plungers is pressed, the fluid pressure supply circuit of the high pressure accumulator is activated, and when the other is pressed, the fluid pressure supply circuit of the high pressure accumulator is activated. The automatic workpiece mounting device with variable clamping force as claimed in claim 2, further comprising an alternating switching type directional switching valve operated by the fluid pressure supply circuit of the accumulator.