Chucking devices and machine tools

Abstract

The present invention provides a chucking device, method, and machine tool that can maintain the chucking torque at an appropriate value and eliminate the need for constant pressurization. [Solution] Initially, the drawbar 200 moves forward and backward by the servo motor 510 to grip the workpiece W, and then the torque adjustment disc spring 420 expands and contracts to adjust the torque applied to the workpiece W. When the servo motor 510 rotates by a predetermined amount instructed by the torque data 504, the servo motor 510 stops and the clutch mechanism 530 turns OFF. However, the torque for gripping the workpiece W in the chucking mechanism 110 is well maintained, and there is no need to apply pressure constantly.

Description

Technical Field

[0001] The present invention relates to an improvement of a chuck device for chucking a workpiece to be processed in various machine tools such as a lathe and a machine tool equipped with the chuck device.

Background Art

[0002] As a conventional chuck device, for example, there is an "electric chuck device" described in Patent Document 1 below. By incorporating a load cell, it automatically adjusts the optimum gripping force in real time. The output of an induction motor is transmitted to a spline shaft through a speed reducer and an electromagnetic clutch, causing the screw nut to rotate. The tightening and loosening of the chuck are determined by this rotation direction. When the chuck jaws grip the workpiece and the induction motor continues to apply torque, the disc spring is deformed. The reaction force generated at this time is detected by the load cell, and the CPU controls the chuck gripping force to match the reference value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, conventional chuck devices use hydraulics or pneumatics, and these pressures must be constantly applied to the chuck device. In contrast, Patent Document 1 describes an electric chuck device in which the gripping force is controlled by an induction motor to a predetermined value. During workpiece processing, the induction motor is disconnected from the spindle shaft by an electromagnetic clutch, but the gripping force of the chuck jaws is maintained. In other words, the induction motor is not constantly driven like in hydraulic systems. However, because the optimal gripping force is adjusted automatically in real time, a load cell is incorporated, making the control of the gripping force complex.

[0005] The present invention focuses on this point and aims to provide a chucking device, method, and machine tool that can maintain the chucking torque at an appropriate value and does not require constant pressurization. [Means for solving the problem]

[0006] The present invention is a chucking device that grips a workpiece in a chucking mechanism by the movement of a drawbar in the axial direction, Torque setting sleeve that rotates by a rotary drive means, A drawbar reciprocating means is provided between the torque setting sleeve and the drawbar, and moves the drawbar forward and backward by the rotation of the torque setting means. Torque adjustment means provided between the torque setting sleeve and the housing, which adjusts the torque when the workpiece is gripped by the chucking mechanism by the reciprocating movement of the drawbar. It is characterized by having the following features.

[0007] In the primary embodiment, the rotational drive means uses a servo motor, and the torque for gripping the workpiece is set by its rotational speed. Furthermore, during workpiece processing, the transmission of rotation to the torque setting sleeve is interrupted by a clutch means, and constant pressure is not applied. In other embodiments, the drawbar advancement and retraction means is provided as a screw means (screw-in means) between the outer circumference of the drawbar and the inner circumference of the torque setting sleeve, and the torque adjustment means is provided on the outer circumference side of the torque setting sleeve, for example, as a disc spring. The rotational drive means rotates the servo motor based on torque data required for gripping the workpiece, which has been acquired in advance. The above and other objects, features, and advantages of the present invention will become clear from the following detailed description and accompanying drawings. [Effects of the Invention]

[0008] According to the present invention, the forward and backward movement of the drawbar in the axial direction is performed by a rotation mechanism using a screw mechanism for torque setting sleeve, and the rotation mechanism is disconnected after gripping the workpiece. As a result, the chucking torque can be maintained at an appropriate value, and constant pressure is not required. [Brief explanation of the drawing]

[0009] [Figure 1] This is a main cross-sectional view showing the state before workpiece gripping in an embodiment where the present invention is applied to a lathe chuck device. [Figure 2] This is a main cross-sectional view showing the state after the workpiece has been gripped in the above embodiment. [Figure 3] (A-1) and (B-1) are enlarged views of the torque setting mechanism in Figures 1 and 2. (A-2) and (B-2) are front views of the chuck portion. [Figure 4] This is a flowchart showing the workpiece gripping operation in the above embodiment. [Modes for carrying out the invention]

[0010] The best mode for carrying out the present invention will be described in detail below based on examples. [Examples]

[0011] Figures 1 and 2 show an example of applying the present invention to a lathe chuck device, with a cross-section along the spindle axis (left-right direction in the figure). Figure 1 shows the state before gripping the workpiece, which is the object to be machined, and Figure 2 shows the state after gripping the workpiece. The torque setting mechanism portion in Figures 1 and 2 is shown in enlargement in Figures 3(A-1) and (B-1), and the chuck portion is shown from the front in Figures 3(A-2) and (B-2), respectively. Figures 3(A-1) and (A-2) show the state before chucking the workpiece, and Figures 3(B-1) and (B-2) show the state after chucking the workpiece. Furthermore, in the following description, the chucking mechanism side (right side in the figure) will be referred to as the "front end," and the clutch mechanism side (left side in the figure) as the "rear end."

[0012] In these figures, a chucking mechanism 110 for gripping a workpiece W (see Figure 3) is provided at the tip side (right side of the figure) of the chuck device 100. The chucking mechanism 110 is equipped with, for example, multiple jaws (four in Figure 3, 110A to 110D), and the workpiece W is gripped or held by the opening and closing of these jaws. Such a structure is well known. The main body of the chuck device 100, on which the chucking mechanism 110 is provided, is rotatably supported by a support housing 122 by a bearing 120.

[0013] Next, a drawbar 200 is provided at the center of the chuck device 100, along the axis of the main shaft. The jaws of the chucking mechanism 110 are opened and closed by the movement of this drawbar 200 in the left-right direction in the figure. A housing 300 that supports the drawbar 200 is provided on the outer circumference of the drawbar 200, and the housing 300 rotates together with the drawbar 200 during machining of the workpiece W. The bearing 120 described above is provided in front of the housing 300 (on the right side in the figure) between it and the support housing 122. The bearing 120 is held in a predetermined position between it and the housing 300 by a fixing or holder 124.

[0014] A space 310 is formed between the drawbar 200 and the housing 300 at the rear of the housing 300 (left side in the figure), and the torque setting mechanism 400 for workpiece gripping in the chucking mechanism 110 is provided in this space 310. The torque setting mechanism 400 is configured such that a servo motor 510 rotates based on a drive signal from the control panel (control device) 500, and this is transmitted via a transmission gear section 520 and a clutch mechanism 530. The clutch mechanism 530 has the function of sliding in conjunction with the sliding of the torque setting sleeve 410.

[0015] In this embodiment, a servo motor is used as a driving means capable of high-precision positioning, but a stepping motor may also be used. In this invention, both are referred to as "servo motor" without distinction.

[0016] The torque setting mechanism 400 includes a torque setting sleeve 410 that receives rotation from the servo motor 510 to set the chucking torque. The torque setting sleeve 410 is provided on the outer circumference of the drawbar 200 and moves back and forth in the direction of the main axis on the outer circumference of the drawbar 200. Bearings 412 and 414 are provided at both ends of the torque setting sleeve 410 in the direction of the main axis. Bearing 412 is provided between the key holding portion 320 fixed to the housing 300 and the torque setting sleeve 410, and bearing 414 is provided between the housing 300 and the key holding portion 320. As a result, the torque setting sleeve 410 is rotatably held relative to the housing 300.

[0017] Next, in the space 310 of the housing 300, a torque adjustment disc spring 420 for adjusting torque is provided between the key holding portion 320 and the side surface of the housing 300. The torque adjustment disc spring 420 has spring retainers 430 and 432 facing each other, and the spring retainers 430 and 432 are configured such that locking portions 440 and 442 provided in a flange shape on the outer periphery of the torque setting sleeve 410 abut thereon. With these configurations, as the distance between the spring retainers 430 and 432 changes according to the movement of the torque setting sleeve 410, the spring force of the torque adjustment disc spring 420 changes, and the torque for workpiece gripping in the chucking mechanism 110 is adjusted.

[0018] Next, an advancing / retreating screw portion 450 is provided between the torque setting sleeve 410 and the drawbar 200. The advancing / retreating screw portion 450 is constituted by screwing a screw 452 provided on the outer peripheral surface of the drawbar 200 and a screw 454 provided on the inner peripheral surface of the torque setting sleeve 410. When the torque setting sleeve 410 rotates, the drawbar 200 advances and retreats relative to the torque setting sleeve 410 in the main shaft direction by the action of the screw portion 450. In particular, when the drawbar 200 advances and retreats and the workpiece W is gripped, the torque setting sleeve 410 advances and retreats in the opposite direction.

[0019] Key grooves 210 and 220 are provided on the outer peripheral surface of the drawbar 200 with the advancing / retreating screw portion 450 interposed therebetween. A key 416 provided inside the torque setting sleeve 410 is fitted into the key groove 210, and a key 418 provided in the key holding portion 320 is fitted into the key groove 220. The connection between the torque setting sleeve 410 and the drawbar 200 is ensured by these key grooves 210 and 220 and the keys 416 and 418.

[0020] Next, the torque for gripping the workpiece W in the chucking mechanism 110 is controlled by a control panel (control device) 500. In the memory 502 of the control panel 500, the relationship between the workpiece W and the optimum tightening torque is obtained in advance and stored as torque data 504. The torque data 504 is a, Material of the workpiece W b, Shape of the workpiece W (diameter size and whether it is hollow or not) c, Mode of processing on the workpiece W (rough machining or finish machining, chuck opening and closing distance, etc.) Depending on factors such as these, the chucking conditions or modes (chucking patterns), such as rough machining only, finish machining only, or from rough machining to finish machining, are determined for each case.

[0021] The torque data 504 instructed by the operator on the control panel 500 is output to the servo motor 510, and the servo motor 510 rotates according to the input data. The rotation of the servo motor 510 is transmitted to the torque setting sleeve 410 via the transmission gear unit 520 and the clutch mechanism 530.

[0022] Next, referring also to the flowchart of FIG. 4, the overall operation of the above embodiment will be described. In the states of FIGS. 1 to 3 (A-1), (A-2) before chucking the workpiece, a, The drawbar 200 is located on the chucking mechanism 110 side (right side of the figure), and in this state, the claws 110A to 110D of the chucking mechanism 110 are open. b, Also, the torque adjustment disc spring 420 is in an open state with the spring retainer 432 located on the left side of the figure.

[0023] In this state, the operator attaches the workpiece W to be processed to the chucking 110 (step SA). Then, the operator selects the chucking pattern of the workpiece W on the control panel 500 (step SB). Then, when an operation start is instructed, the torque data 504 of the chucking pattern selected from the control panel 500 is read from the memory 502 (step SC) and output to the servo motor 510. On the other hand, an ON signal is output from the control panel 500 to the clutch mechanism 530 (step SD).

[0024] Next, the servo motor 510 is driven when torque data 504 is input (step SE), and rotates to the torque specified in the torque data 504. This rotation is transmitted to the torque setting sleeve 410 of the torque setting mechanism 400 via the transmission gear section 520 and the clutch mechanism 530, causing the torque setting sleeve 410 to rotate. As a result, the drawbar 200 moves towards the rear end (to the left in the figure) due to the action of the screw section 450 (see arrow F1 in Figure 3 (A-1)). This causes the chucking mechanism 110 to grip the workpiece W with a predetermined torque by the jaws 110A to 110D (step SF, see Figure 3 (B-2)).

[0025] On the other hand, when the workpiece W is gripped and further rotated by the servo motor 510, the torque attempts to increase rapidly. However, in the torque setting mechanism 400, the torque setting sleeve 410 now rotates relative to the drawbar 200 by the screw portion 450. As a result, the torque setting sleeve 410 moves in the opposite direction to the drawbar 200 (see arrow F2 in Figure 3 (B-1)).

[0026] As the torque setting sleeve 410 moves in the direction of arrow F2, the locking portions 440 and 442 of the torque setting sleeve 410 also move in the direction of arrow F2. As a result, the spring retainer 430 comes into contact with the key holding portion 320 and stops moving, while the spring retainer 432 on the opposite side pushes the torque adjustment disc spring 420, causing the torque adjustment disc spring 420 to move from an open state (Figures 1 and 3 (A-1)) to a closed state (Figures 2 and 3 (B-1)). Therefore, the spring force from the torque adjustment disc spring 420 acts from the torque setting sleeve 410 to the drawbar 200. This adjusts the torque applied to the workpiece W by the rotation of the servo motor 510 and suppresses a sudden increase in torque.

[0027] In other words, the servo motor 510, a. Initially, the drawbar 200 moves back and forth to grip the workpiece W. b. Next, the torque adjustment disc spring 420 expands and contracts (or opens and closes) to adjust the torque on the workpiece W.

[0028] When the servo motor 510 rotates by a predetermined amount instructed by the torque data 504, the servo motor 510 stops (step SG), and then the clutch mechanism 530 turns OFF (step SH). However, the torque for gripping the workpiece W in the chucking mechanism 110 is maintained well.

[0029] After the chucking of the workpiece W is completed as described above, the clutch mechanism 530 is turned OFF, and the chucking mechanism 110 is rotated by a spindle motor (not shown). That is, when the clutch mechanism 530 is turned OFF, the drive means from the servo motor 510 to the clutch mechanism 530 is disconnected, and the part indicated by the dashed line RW rotates relative to the support housing 122 by the bearing 120, and the workpiece W is machined. When the machining of the workpiece W is finished, the clutch mechanism 530 is turned ON, and the servo motor 510 is rotated in reverse to remove the workpiece W from the chucking mechanism 110.

[0030] As described above, the following effects can be obtained according to this embodiment. a. By using a servo motor 510, the drawbar 200 is moved forward and backward by the screw portion 450 of the torque setting sleeve 410 to grip the workpiece W, and the torque is adjusted by the expansion and contraction of the torque adjustment disc spring 420, so that the workpiece W can be chucking with an appropriate torque. b. After the workpiece W is chucking, the servo motor 510 is disengaged by the clutch mechanism 530 and the servo motor 510 stops, so power is not required to maintain torque during workpiece processing. c) Even if a power outage occurs, the chucking state of the workpiece W is maintained, so there is no risk of the workpiece W falling. d. The bearing that rotates the chucking mechanism 110 during workpiece processing is not subjected to the load and reaction force of spindle rotation, thus improving its durability. e. During workpiece processing, the entire chuck device rotates, thus suppressing heat generation. f. As the clutch mechanism 530, a ball-type clutch that can move straight (slide) is used, so there is no pulsation like in a hydraulic system and no resonance occurs. g. The control panel 500 allows selection of torque amount, chuck opening / closing distance, chucking pattern, etc., resulting in improved work efficiency.

[0031] <Other Embodiments> The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, the following are also included. (1) The shapes and dimensions of the parts shown in the above embodiment are examples only, and the design can be modified to perform similar functions. For example, the direction of movement of the drawbar and the direction of opening and closing of the jaws in the chucking mechanism may be changed as appropriate. (2) The gripping of the workpiece by opening and closing the jaws in the chucking mechanism may be either internal gripping or external gripping. (3) Although a servo motor was used in the above embodiment, any driving means capable of accurate positioning may be used. For example, a stepping motor may be used. (4) In the above embodiment, the drawbar 200 slides in the direction of arrow F1 and the torque setting sleeve 410 slides in the direction of arrow F2, but a structure in which they slide in opposite directions is also possible. (5) The chuck device of the present invention can be used with various machine tools in addition to lathes, such as machining centers, NC (numerical control) machines, CNC (computer numerical control) machines, milling machines, and laser cutting machines. [Industrial applicability]

[0032] As described above, according to the present invention, the advancement and retraction of the drawbar in the axial direction is performed by a rotation mechanism using a screw means for torque setting sleeve, and the rotation mechanism is disconnected after gripping the workpiece. Therefore, the chucking torque can be maintained at an appropriate value, constant pressure is not required, and it is suitable for chucking devices of various machine tools such as lathes. [Explanation of Symbols]

[0033] 100: Chuck device 110: Chucking mechanism 110A~110D: Claws 120: Bearings 122: Support housing 124: Fixing or holding device 200: Drawba 210,220: Keyway 300: Housing 310: Space 320: Key retention section 400: Torque setting mechanism 410: Torque setting sleeve 412,414: Bearings 416,418: Key 420: Torque adjustment disc spring 430, 432: Spring retainer 440, 442: Locking part 450: Retractable screw section 452,454: Screws 500: Control Panel 502: Memory 504: Torque Data 510: Servo motor 520: Transmission gear section 530: Clutch mechanism W: Work

Claims

1. A chucking device in which a workpiece is gripped by a chucking mechanism by the movement of a drawbar in the direction of the main axis, Torque setting sleeve that rotates by a rotary drive means, A drawbar reciprocating means is provided between the torque setting sleeve and the drawbar, and moves the drawbar forward and backward by the rotation of the torque setting means. Torque adjustment means provided between the torque setting sleeve and the housing, which adjusts the torque when the workpiece is gripped by the chucking mechanism by the reciprocating movement of the drawbar, A chuck device characterized by having the following features.

2. The chuck device according to claim 1, characterized in that the rotational drive means uses a servo motor and is equipped with a clutch means for interrupting the transmission of rotation to the torque setting sleeve when the workpiece is being processed.

3. The chuck device according to claim 1, characterized in that the torque setting sleeve is provided on the outer circumference side of the drawbar.

4. The chuck device according to claim 3, characterized in that the drawbar advancement means is a screw means provided on the outer circumference of the drawbar and the inner circumference of the torque setting sleeve.

5. The chuck device according to claim 1, characterized in that the torque adjustment means is provided on the outer circumference of the torque setting sleeve.

6. The chuck device according to claim 5, characterized in that the torque adjustment means is a disc spring that expands and contracts in accordance with the advancement and retraction of the torque setting sleeve in the main axis direction.

7. The chuck device according to claim 1, characterized in that the rotational drive means rotates the torque setting sleeve based on torque data necessary for gripping the workpiece, which has been acquired in advance.

8. A chucking method for chucking a workpiece using a chucking device according to any one of claims 1 to 7, The workpiece is gripped by the movement of the drawbar by the rotational drive means, After gripping the workpiece, the torque applied to the workpiece is adjusted using the torque adjustment means. A chuck method characterized by the following features.

9. A machine tool comprising a chuck device according to any one of claims 1 to 7, characterized in that it chucking the workpiece using the chuck method according to claim 8.

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