JPH032606B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to an electric chuck device for chucking a workpiece in a lathe, etc., and particularly for chucking a long workpiece and responding to high-speed rotation. This invention relates to an electric chuck device capable of

``Prior Art'' In place of conventional hydraulic or pneumatic chuck drive devices for operating chucks for gripping workpieces in lathes, etc., electric chuck drive devices (for example, JP-A-51-1999 No. 45111, JP-A-53
−19830, Utility Model No. 54-5395, Utility Model 56-29050
However, these conventional electric chuck devices cannot steplessly adjust the gripping force of the chuck, so it is difficult to select the optimal gripping force for each type of workpiece. difficult to do. Secondly, it is not possible to quantitatively grasp or confirm the gripping force of the chuck, so even if the chuck's claws grip the workpiece unevenly, this cannot be detected. Thirdly, since the driving means such as the cylinder for driving the chuck is arranged coaxially with the main shaft (spindle shaft) of the lathe, etc., there is a problem that the gripping of a long object is immovable. It was hot.

For this reason, the applicant of the present invention proposed and filed an application for an electric chuck device (Japanese Patent Application No. 62-23886 ``Electric Chuck Device'') which can solve these problems.
FIG. 4 is a partial sectional view showing the main parts of the electric chuck device.

The electric chuck device opens and closes a chuck claw (not shown) (located on the right side of the figure) by reciprocating the traction shaft 32 in its axial direction by a drive means using an electric motor 31 as a drive source. Something,
The traction shaft 32 is formed into a hollow cylindrical shape, and the drive means (electric motor 3) is attached to the outer circumference of the traction shaft 32.
1), the output shaft 31a of the drive means and the traction shaft 32 are arranged with their axes different from each other, and the output shaft of the drive means A driving force transmission mechanism D is interposed between the screw nut 33 and the screw nut 33 to transmit the driving force from the driving means to the screw nut 33. The device is characterized in that a displacement measuring means 34 is provided for measuring the amount of displacement of the driving force transmitting mechanism D, and further, the driving force transmitting mechanism D has a thread carved on the inner circumferential surface thereof and the output shaft of the driving means. 31a, a spiral gear 36 which is screwed onto the inner circumferential surface of the rotary body 35 and slidably inserted into the outer periphery of the screw nut 33, and a spiral gear 36 which is inserted in the forward direction in the spiral direction of the spiral gear A clutch hub 37 is provided and screwed onto the outer periphery of the screw nut 33, and a side surface of the spiral gear 36 facing the clutch hub 37 is formed with unevenness extending in the circumferential direction. A side surface of the clutch hub 37 facing the spiral gear 36 is formed with projections and depressions that fit into the projections and depressions of the spiral gear 36, and an elastic member 38 is interposed between the spiral gear 36 and the clutch hub 37. It is.

Further, reference numeral 40 is a spindle shaft (main shaft), and reference numeral 39 is a frame that rotates integrally with the spindle shaft 40, the screw nut 33, etc. The frame 39 is attached to the screw nut 3.
3 is rotatably provided via bearings 41, 42, and has claws 39a formed on its outer peripheral surface.On the outside of this frame 39, as shown in FIG. A solenoid 43 is provided, and a lever 44 operated by the solenoid 43 is engaged with a pawl 39a of the frame 39, so that rotation of the frame 39 can be restrained. What restricts the rotation of the frame 39 is provided within the frame 39,
By changing the relative position of the flange portion 33a formed integrally with the screw nut 33 with respect to the frame 39, the disc springs 45 and 46 that bias the flange portion 33a from both sides are flexed, thereby This is to enable the tightening force to be maintained.

"Problems to be Solved by the Invention" By the way, in the above electric chuck device, the output shaft 31a of the drive means and the traction shaft 32 for opening and closing the chuck pawl are not coaxial, so the traction shaft 32 is hollow. It can be formed into a cylindrical shape, making it possible to grip long objects, and since it is provided with a displacement measuring means 34 that detects the amount of displacement of the screw nut 33 screwed onto the outer periphery of the traction shaft 32, it is possible to grasp a long object using a chuck claw. By constantly monitoring the amount of displacement of the screw nut 33 when gripping a workpiece, it becomes possible to quantitatively understand and confirm the gripping force of the chuck.
Although it has excellent effects such as being able to adjust the gripping force of the chuck steplessly,
The above-mentioned electric chuck device also had the following points to be improved.

First, since the screw nut 33, clutch hub 37, frame 39, etc. rotate together with the spindle shaft (main shaft) 40 during workpiece machining, as the rotation speed of the spindle shaft 40 increases,
One reason is that it becomes difficult to maintain a high-precision balance.One reason is that the spindle shaft 40
One problem is that the moment of inertia of the clutch hub 37 increases, and when this chuck device is applied to a machine whose operation is automatically controlled, such as an NC lathe, the servo characteristics of the spindle shaft 40 are degraded.
Due to the action of
Although it is designed to prevent the transmission of information to the spindle shaft 40, the structure is complicated.
When the machine rotates, that is, when machining a workpiece, the chuck cannot be tightened or loosened.

"Means for Solving the Problems" The present invention provides an electric chuck device in which a chuck pawl is opened and closed by reciprocating a traction shaft in its axial direction by a drive means using an electric motor as a drive source. , the traction shaft is formed into a hollow cylindrical shape and divided into two parts, a drive side and a chuck side, and the chuck side traction shaft is coaxially and rotatably connected to the drive side traction shaft via a rolling bearing,
Further, a screw nut rotated by the drive means is screwed onto the outer periphery of the drive-side traction shaft, and the output shaft of the drive means and the traction shaft are arranged with their axes different from each other. , a driving force transmission mechanism for transmitting the driving force from the driving means to the screw nut is interposed between the output shaft of the driving means and the screw nut; A displacement measuring means for measuring the amount of displacement of the gear in the axial direction is provided near the gear that is coaxial and integral with the nut.

``Function'' The traction shaft is divided into two parts, the chuck side and the drive side, and the chuck side traction shaft and the drive side traction shaft can rotate relative to each other. The rotation of the chuck-side traction shaft may not be transmitted to the drive-side traction shaft.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a partial side cross-sectional view showing the configuration of the main parts of an electric chuck device according to an embodiment of the present invention.
Reference numeral 1 denotes an induction motor which is a driving means of this device, and the number of rotations of this induction motor 1 is detected by an optical rotation detector 2 and taken out as an electric signal.

A pinion gear 3 is attached to the output shaft 1a of the induction motor 1.
The pinion gear 3 meshes with and is connected to a large gear 5 via an idle gear 4, and the large gear 5 is keyed to a hollow cylindrical screw nut 6. the pinion gear 3;
Idle gear 4, large gear 5, output shaft 1 of the drive source
A driving force transmission mechanism D is configured to transmit the output torque of a to the screw nut 6.

The screw nut 6 has a female thread carved on its inner circumferential surface, and is a cylindrical draw bolt (drive side traction shaft).
It is screwed into a male screw formed on the outer periphery of the holder 9.
The draw bolt 9 is attached to a cylindrical draw tube (chuck-side traction shaft) 12 inserted into the hollow part of the spindle shaft 11, which is the main shaft of a lathe, etc., through a rolling bearing 17. The draw tubes 12 are connected in such a manner that they match and the draw tube 12 is rotatable. The rolling bearing 17 is preferably a double thrust bearing that can receive thrust forces in both directions.

The outer periphery of the base end 9a of the draw bolt 9 is spline-coupled to a fixed flange 14 fixed to the main body, so that movement in the rotational direction is restricted and only sliding in the axial direction is allowed. It's summery. As a result, when the screw nut 6 is rotated by the induction motor 1, the draw bolt 9 reciprocates in the axial direction, and the draw tube 12 also reciprocates in the axial direction via the rolling bearing 17. A chuck pawl (not shown) connected to the draw tube 12 moves in the radial direction of the chuck to grip the workpiece.

A cylindrical frame 15 with both ends closed is attached to the outer periphery of the intermediate portion of the screw nut 6 via angular bearings 7 and 8.
Further, this screw nut 6 is formed with a flange portion 6a that bulges in the radial direction, and a plurality of disc springs are arranged back to back between the flange portion 6a and the angular bearings 7, 8. Disc springs 20 and 21 are fitted therein. Flange part 6
Through holes are bored at intervals in the circumferential direction of a, and preload springs 2 are installed in the through holes.
2 is inserted, and the preload spring 22 eliminates the rattling of the disc springs 20, 21, and the aguilla bearings 7, 8 are pressed against their outer sides.

Furthermore, a photoelectric displacement sensor 18 is attached to the inner peripheral surface of the outer frame 16 that uniformly covers the large gear 5, the frame 15, the fixed flange 14, etc., at a position facing the side surface of the large gear 5. . This photoelectric displacement sensor 18 measures the distance between the side surface of the large gear 5 and the photoelectric displacement sensor 18.
It has a function of measuring the amount of displacement of the screw nut 6 in the axial direction.

Next, in FIG. 2, the output from the displacement sensor 18 is amplified by an amplifier 18a and sent to the CPU 2 via an interface (I/F) 23.
4. Further, an input device 25 is connected to an interface (I/ F) is connected to the CPU 24 via 26. Here, the input device 25 displays a keyboard and data input from the keyboard.
It consists of an LED display device. Further, a digital display device 27 is connected to the interface (I/F) 26, and the chuck gripping force is displayed numerically. The CPU 24 determines the magnitude of the current to be supplied to the induction motor 1 based on the input data and the feedback signal from the displacement sensor 18, and supplies this to the D/A converter 28. The D/A converter 28 converts the digital signal supplied from the CPU 24 into an analog signal and supplies it to the motor control device 29. Based on this analog signal, the motor control device 29 controls the firing angle of the bidirectional thyristor, controls the phase of the traffic power source, and controls the current supplied to the induction motor 1.

Next, the operation of this embodiment will be explained for each item.

Tightening and loosening operations of the chuck pawl: When the induction motor 1 is driven, this output torque is transmitted to the large gear 5 via the pinion gear 3 and the idle gear 4, and the screwdriver fitted with the large gear 5 The signal is transmitted to the nut 6. When the screw nut 6 rotates, the draw bolt 9 screwed into it moves in the axial direction since its base end 9a is splined to the fixed flange 14. As a result, the rolling bearing 17 at the base end 9a
The draw tube 12 connected through the draw tube 12 is moved in the axial direction, and a chuck claw (not shown) provided at the base end of the draw tube 12 is tightened or loosened. The conversion mechanism for transmitting the axial force of the draw tube 12 to the chuck pawl is the same as the conventional one, so illustration and description thereof will be omitted.

Here, the tightening and loosening operations of the chuck pawl are determined by the direction of rotation of the screw nut 6.
Therefore, depending on the rotation direction of the induction motor 1,
The chuck claw can be tightened or loosened. Further, at this stage, since no external force in the axial direction is applied to the screw nut 6, the screw nut 6 does not move in the axial direction due to the action of the disc springs 20 and 21.

Maintaining tightening force: When the induction motor 1 is rotated in the direction of tightening the chuck pawl and the screw nut 6 is rotated in one direction, the draw bolt 9 moves to the left in Fig. 1 and is connected to it. The drawn draw tube 12 is moved to the left.

When the chuck grips the workpiece, movement of the draw bolt 9 and the draw tube 12 is stopped. At this point, if a current is further applied to the induction motor 1 and an appropriate torque is continued to be applied to the screw nut 6, since the movement of the draw bolt 9 is restricted, the screw nut 6 will rotate and the first
It spirals to the right in the figure to deform the disc spring 21.
The amount of displacement of the screw nut 6 is detected by the photoelectric displacement sensor 18 on the side surface of the large gear 5 that moves together with the screw nut 6. At this point, if the current to the induction motor 1 is cut off, the friction torque of the male thread of the draw bolt 9 and the elastic force of the disc spring 21 compete with each other, and the deformation of the disc spring 21 is maintained. This allows the draw bolt 9
Since a tensile force to the left in FIG. 1 is applied due to the elastic force of the disc spring 21, the induction motor 1 continues to grip the workpiece without constantly applying torque to the screw nut 6. A torque corresponding to the amount of torque will be applied to the chuck pawl.

Gripping force adjustment during workpiece processing (spindle shaft rotation): During workpiece processing, the spindle shaft 11 and the draw tube 12 are rotating together, but the draw bolt 9 screwed into the screw nut 6 Since it is prevented from rotating on the inner periphery of the fixed flange 14 via the rolling bearing 17, the tension generating side drive device can be operated regardless of the rotation of the spindle shaft 11. Therefore, the spindle shaft 11
Even during rotation, that is, during machining of a workpiece, the induction motor 1 is operated to move the draw bolt 9 to the left in FIG. The draw tube 12 can be moved in the direction of tightening the chuck pawl.

Detection of tensile force of draw tube 12: When the disc spring 21 (or disc spring 20, but in the following explanation, only the disc spring 21 will be explained. The same applies to the disc spring 20) is deformed. , the reaction force, that is, the elastic force of the disc spring 21 is,
As described above, the tensile force of the draw tube 12 is transmitted to the chuck pawl via the draw bolt 9, and this force grips the workpiece. Therefore, since the amount of deflection of the disc spring 21 is proportional to the tensile force of the draw bolt 9 (draw tube 12), if the amount of deflection of the disc spring 21, that is, the amount of displacement of the large gear 5 is measured by the proximity sensor 18, the draw The tensile force of the tube 12 can then be detected. The signal from the proximity sensor 18 is amplified by the amplifier 18a and then supplied to the CPU 24 via the interface 23. The CPU 24 compares this signal with a preset reference value to obtain an operation signal, calculates an operation signal based on this operation signal, and sends it to the D/A converter 28. is converted into an analog signal and sent to the motor control device 29, and the motor control device 29 performs phase control on the induction motor 1 based on the operation signal converted to the analog signal. thus,
The output torque of the induction motor 1 is feedback-controlled by the signal from the proximity sensor 18, and is automatically controlled so that the chuck gripping force matches a reference value. Note that the reference value is set using the input device 25.

Adjustment of tightening torque: As mentioned above, in this embodiment, the displacement sensor 1
The output torque of the induction motor 1 is controlled based on the output of the induction motor 8, and stepless feedback control is performed so that the chuck gripping force matches a predetermined reference value. A specific method of this control will be described below with reference to FIG.

When the induction motor 1 is started with a workpiece facing the chuck, the screw nut 6 rotates, pulling the draw tube 12 through the draw bolt 9 and moving the chuck claw until it comes into contact with the workpiece. . When the chuck jaws start gripping the workpiece,
The disc spring 21 is pressed and begins to bend. This is the third
This is between time t ₀ and t ₁ in the figure. Here, if the rotation speed of the induction motor 1 during the so-called idling rotation until the chuck claw comes into contact with the workpiece is higher than necessary, the moment of inertia of the rotating system will impact the disc spring 21, causing a slight impact. It is difficult to adjust the gripping force. For this reason, it is desirable that the idle rotation speed be as low as work efficiency allows, and therefore, the rotation speed of the induction motor 1 is adjusted by appropriately controlling the phase of the current supplied to the induction motor 1 by the motor control device 29. The need arises. The rotation detector 2 is provided for this purpose.

Now, the disk spring 21 starts to bend and the displacement sensor 18
When an output is generated, the CPU 24 detects this and temporarily turns off the current supplied to the induction motor 1 (c in the same figure). Induction motor 1 starts at time _t1 .
It rotates due to inertia during Ta and stops at time t ₂ .
During this time Ta, the deformation of the disc spring 21 progresses, and the pressing force increases slightly as shown in FIG.

Time t ₃ when time Tb has elapsed since induction motor 1 stopped
Then, the CPU 24 supplies current to the induction motor 1 again. As a result, a restraining torque is generated in the induction motor 1, the draw tube 12 is pulled, and the amount of displacement of the screw nut 6 increases. And the CPU
24 supplies current to the induction motor 1 while checking the feedback signal from the displacement sensor 18 until time _t4 when the gripping force of the chuck reaches a reference value. During this time, adjustment of the locking torque of the induction motor 1 is performed by the motor control device 29 performing phase control of the induction motor 1.

Therefore, according to the electric chuck device according to the present embodiment, the output shaft 1a of the induction motor 1 and the draw bolt 9 and the draw tube 12 for opening and closing the chuck pawl are not coaxially arranged. By forming the draw tube 12 into a hollow cylindrical shape, it is possible to grip a long workpiece, and the overall length of the chuck device itself can be shortened.

Since a displacement sensor 18 is provided to detect the amount of displacement of the screw nut 6, the gripping force of the chuck can be quantitatively determined by constantly monitoring the amount of displacement of the screw nut 6 when gripping a workpiece with the chuck pawl. It becomes possible to grasp and confirm, and the grasping force of the chuck can be adjusted steplessly. In addition to the above effects, the traction shaft has draw bolt 9 and draw tube 1.
2, the rotation of the spindle shaft 11 is transmitted only to the draw tube 12, so that drive mechanisms such as the screw nut 6 and disc springs 20, 21 can be rotated during normal machining. As a result,
It is possible to balance vibrations etc. with high precision, and not only can the speed of the spindle shaft be increased, but also the moment of inertia of the spindle shaft 11 can be reduced, and the servo control of the spindle shaft 11 during automatic control can be made smaller. Characteristics can be improved.

Even while the spindle shaft 11 is rotating, that is, the draw tube 12 is rotating, the draw bolt 9
does not rotate, and the driving force transmission mechanism D can apply an axial force to the draw tube 12 via the draw bolt 9, making it possible to adjust the gripping force even during machining of a workpiece. It can produce excellent effects such as:

Note that the following modifications can be considered to this embodiment.

A storage device such as a floppy disk device can be connected to the CPU 24 to store processed data.

It can be interfaced to work with other automated equipment.

By pursuing the optimum chuck gripping force, CAM
It has the potential to develop into a component of a computer aided manufacturing (Computer Aided Manufacturing) system.

"Effects of the Invention" As explained above, according to the present invention, since the output shaft of the induction motor and the traction shaft (draw bolt and draw tube) for opening and closing the chuck pawl are not coaxial, these traction shafts can be By forming it into a hollow cylindrical shape, it is possible to grip long workpieces, and the overall length of the entire device can be shortened.Furthermore, it is equipped with a displacement sensor that detects the amount of displacement of the screw nut. Therefore, when a workpiece is gripped by the chuck claw, the displacement of this screw nut is constantly monitored to quantitatively grasp and confirm the gripping force of the chuck, and the gripping force of the chuck can be adjusted steplessly. In addition, since the traction shaft is divided into the draw bolt and draw tube, the rotation of the spindle shaft is not transmitted to the drive mechanism, and as a result, it is possible to balance vibrations etc. with high precision. This not only makes it possible to reduce the moment of inertia of the spindle axis, improves the servo characteristics of the spindle axis during automatic control, but also makes it possible to adjust the chuck gripping force even while machining the workpiece. It has various excellent effects such as.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the main parts of an electric chuck device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the electrical configuration of the same electric chuck device.
Fig. 3 is a time chart for explaining the tightening torque adjustment operation of the electric chuck device, Fig. 4 shows a conventional example, Fig. 4a is a partial sectional view of the electric chuck device; Figure b is a left side view with the same part cut away. 1... Induction motor (drive means), 1a... Output shaft, 5... Large gear (gear), 6... Screw nut, 9... Draw bolt (drive side traction shaft), 1
2...Draw tube (chuck side traction shaft), 1
7...Rolling bearing, 18...Photoelectric displacement sensor (displacement measurement means), D...Driving force transmission means.

Claims (1)

[Claims] 1. In an electric chuck device in which a chuck pawl is opened and closed by reciprocating a traction shaft in its axial direction by a drive means using an electric motor as a drive source, the traction shaft is formed into a hollow cylinder and has a drive side. and a chuck side, and the chuck side traction shaft is coaxially and rotatably connected to the drive side traction shaft via a rolling bearing, and the outer periphery of the drive side traction shaft has the A screw nut rotated by a driving means is screwed together,
The output shaft of the drive means and the traction shaft are arranged with their axes different from each other, and a screw is connected between the output shaft of the drive means and the screw nut to transmit the driving force from the drive means. A driving force transmission mechanism for transmitting the screw nut to the screw nut is interposed, and a displacement mechanism for measuring the axial displacement of the gear is provided near the gear that constitutes the driving force transmission mechanism and is coaxial and integral with the screw nut. An electric chuck device characterized by being provided with a measuring means.