JP6726565B2 - Machine tool spindle device - Google Patents

Description

The present invention relates to a spindle device for machine tools capable of suppressing vibrations generated during machining.

In a machine tool that performs machining while rotating a tool or a work, so-called chatter vibration occurs during machining, which causes problems such as deterioration in finishing accuracy of a machined surface, tool wear, and tool loss. As a method for suppressing such chatter vibration, for example, in Patent Document 1, when occurrence of chatter vibration is detected based on time-domain vibration detected by a vibration sensor or the like, it is optimal using k value and phase information. In addition to calculating the rotation speed, the type of chatter vibration is specified from the phase information, and when chatter vibration different from the specified chatter vibration occurs in the past, the invention changes the k value and recalculates the optimum rotation speed. It is disclosed. Further, in Patent Document 2, a mechanism for supplying oil to a gap between the housing and the main shaft from three or more circumferential positions is provided in a housing supporting the main shaft, and a radial vibration direction of the main shaft detected by a displacement sensor. There is disclosed an invention that suppresses the vibration of the main shaft by changing the oil pressure and the oil amount according to the above.

Japanese Patent No. 4734646 JP, 2011-235404, A

In the invention of Patent Document 1, since vibration suppression is accompanied by a change in processing conditions such as rotation speed, there is a possibility that the processing accuracy may be reduced and the processing time may be extended. In the invention of Patent Document 2, since the direction of hydraulic pressure supply is constant and cannot be changed, effective damping may not be performed depending on the generated vibration.

Therefore, an object of the present invention is to provide a spindle device of a machine tool that can effectively suppress vibration without changing machining conditions.

In order to achieve the above-mentioned object, the invention according to claim 1 includes a main shaft to which a tool is detachably attached and which is rotatably supported via a bearing in a housing, a motor for rotating the main shaft, and the motor. A spindle device of a machine tool including a control device for controlling,
A damping member that is housed in a hollow portion formed in the main shaft and is movable back and forth in the rotation axis direction of the main shaft, processing conditions including the rotation speed of the main shaft and the dimensions of the tool, and support rigidity of the bearing. And a vibration analysis means for analyzing a vibration form of the main shaft based on a bearing characteristic including a damping coefficient, and an NC device included in the control device. The vibration analysis means is formed based on an analysis result of the vibration analysis means. And a moving means for moving the member to a predetermined position in the rotation axis direction.
According to a second aspect of the present invention, in the structure of the first aspect, a vibration detection unit that detects vibration generated in the spindle during processing is further provided, and the vibration analysis unit detects the processing detected by the vibration detection unit. The internal vibration is analyzed, and the moving unit moves the damping member to a position different from the predetermined position based on an analysis result of the vibration analyzing unit.
According to a third aspect of the present invention, in the configuration of the first or second aspect, the damping member is housed in a hollow portion formed in the main shaft so as to be movable back and forth, and the moving unit is provided in the hollow portion. An urging means that is provided and urges the damping member to one of the front and rear sides, and a pressurizing chamber that is formed on the opposite side of the urging means with the damping member interposed therebetween and to which a fluid is supplied, And a fluid pressure adjusting mechanism capable of adjusting the fluid pressure to the pressurizing chamber.

According to the present invention, the vibration form of the spindle is analyzed based on the processing conditions and the bearing characteristics, and the vibration damping member is moved to a predetermined position based on the analysis result. Therefore, the vibration damping can be performed without changing the processing conditions. The damping effect of the member can be exerted to effectively suppress the vibration.
Especially, by analyzing the vibration generated during machining and moving the damping member to a position different from the predetermined position based on the analysis result, the natural frequency of the spindle can be continuously changed during machining to effectively vibrate the vibration. Can be suppressed.

It is explanatory drawing of the spindle device of a machine tool. It is a flow chart of position control of a damping color.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a spindle device provided in a machine tool such as a machining center. In the spindle device 1, 2 is a spindle, which is rotatably supported by a motor 3 in a housing (not shown) via bearings 4 and 4. The main shaft 2 is hollow, and a draw bar 5 is urged to the retracted position by a pressing mechanism 6 which is movable in the shaft center and which uses disc springs 7, 7... Installed at the rear portion of the main shaft 2. It is provided in the state where it was opened. This draw bar 5 clamps the tool holder 9 at the tip of the main spindle 2 by clamping the chuck mechanism 8 provided at the front of the main spindle 2 at the retracted position, and the chuck mechanism 8 is moved forward by a hydraulic mechanism (not shown). Perform unclamp operation. Reference numeral 10 is a cooling liquid supply passage provided at the axial center of the draw bar 5.

A hollow portion 12 partitioned by a partition plate 11 located at the front end of the pressing mechanism 6 is coaxially formed in the main shaft 2 on the front side of the pressing mechanism 6, and the vibration damping mechanism 13 is provided in the hollow portion 12. It is provided. The damping mechanism 13 includes a fixing collar 14 which is penetrated by the draw bar 5 and fixed to the front end of the hollow portion 12, and a damping collar which is a damping member which is movable axially through which the draw bar 5 penetrates behind. 15, a plurality of coned disc springs 16, 16 as biasing means interposed between the fixed collar 14 and the damping collar 15 to bias the damping collar 15 rearward, and the rear of the damping collar 15. And a pressure chamber 17 formed between the partition plate 11 and the partition plate 11. A pressure oil supply passage 18 having a front end communicating with the pressurizing chamber 17 is formed inside the drawbar 5 outside the cooling liquid supply passage 10 over the range of the stroke of the drawbar 5.
The vibration damping collar 15 is made of a cylindrical steel material, and ring-shaped grooves are formed on the inner circumference and the outer circumference, and resin-made sealing members 19 and 19 are incorporated in the respective grooves to form a pressurizing chamber 17. It is sealed.

The pressure oil supply passage 18 is connected to the hydraulic unit 21 via the control valve 20, and the pressure oil sent from the hydraulic unit 21 is supplied to the pressurizing chamber 17 via the pressure oil supply passage 18. Therefore, the front-rear position of the damping collar 15 is determined at the position where the urging force of the disc springs 16, 16... Balances the hydraulic pressure from the pressurizing chamber 17. By changing the hydraulic pressure from the pressurizing chamber 17, the damping collar 15 is moved back and forth in the axial direction, so that the bending rigidity and the damping characteristic of the main shaft 2 can be changed.

Next, the control system of the spindle device 1 will be described.
Reference numeral 22 denotes a control device, which is provided with an input device 23, a computing device 24, a storage device 25, and an NC device 26.
The input device 23 allows an operator to input processing conditions such as the rotation speed of the spindle 2 and the tool size, and a vibration detection signal from a vibration detection means such as a vibration sensor (not shown) provided in the housing. There is.
The calculation device 24 as a vibration analysis means determines the vibration form of the spindle 2 based on the processing conditions including the rotation speed and the tool size input from the input device 23 and the analysis data recorded in the storage device 25, which will be described later. The analyzed hydraulic form and the spring constant of the disc spring 16 are used to determine the hydraulic pressure to the pressurizing chamber 17 for moving the damping collar 15 to the position where the damping effect is maximized. In addition, the vibration from the vibration sensor is analyzed to determine whether chatter vibration has occurred.

The storage device 25 stores in advance analysis data such as the shape of the main shaft 2, the bearing rigidity including the support rigidity and damping coefficient of the bearing 4, the spring constant of the disc spring 16, and the hydraulic pressure determined by the arithmetic unit 24. Remember. The machining program is also stored.
The NC device 26 controls the motor 3 and the like in accordance with the machining program stored in the storage device 25, and also controls the control valve 20 so that the pressurizing chamber 17 has the hydraulic pressure stored in the storage device 25. Here, the pressure oil supply passage 18, the control valve 20, the hydraulic unit 21, and the NC device 26 are the fluid pressure adjusting mechanism of the present invention, and the structure including the disc spring 16 is the moving means of the damping collar 15. ..

In the spindle device 1 configured as described above, the control device 22 analyzes the vibration form of the spindle 2 based on the above-described analysis data, and based on the analyzed vibration form and the spring constant of the disc spring 16, the damping collar Position control is performed to move 15 to exert a damping effect. The position control of the damping collar 15 will be described below with reference to the flowchart of FIG.
First, in S1, the input device 23 inputs the rotation speed of the spindle 2 and the tool size to set machining conditions.
Next, in S2, the arithmetic unit 24 analyzes the vibration mode of the spindle 2 based on the processing conditions input from the input unit 23 and the analysis data stored in the storage unit 25, and stores it in the storage unit 25. To do.

Next, in S3, the hydraulic pressure applied to the pressurizing chamber 17 for moving the damping collar 15 to the position where the damping effect is maximized is calculated from the analyzed vibration form and the spring constant of the disc spring 16. , In the storage device 25.
Then, in S4, the NC device 26 sends a command to the control valve 20 so that the hydraulic pressure stored in the storage device 25 is reached, and moves the damping collar 15 to the initial position. This initial position is the position of the antinode of the maximum amplitude of the analyzed vibration.

After the damping collar 15 is moved to the initial position in this way, processing is started in S5.
When chatter vibration is detected during processing in S6, the computing device 24 performs FFT analysis of the vibration of the spindle 2 and additional information obtained from the vibration detection means to specify the chatter frequency, and then calculates the following formula (1). ), the specified chatter frequency f _chatter is multiplied by an arbitrary coefficient α to determine the fluctuation frequency f _{color of the} hydraulic pressure to be added to the damping collar 15.
f _color = α · f _chatter · · (1)
Next, in S8, the NC device 26, which has obtained the variable frequency of the additional hydraulic pressure from the arithmetic device 24, controls the control valve 20 based on the variable frequency to change the additional hydraulic pressure, and moves the damping collar 15 from the initial position. Slide it back or forth.
Since the vibration form changes due to the movement of the damping collar 15, the chatter vibration generated at the initial position is suppressed.

After that, when it is confirmed in S9 that the processing is completed, the position control ends. If the processing is not completed, the process returns to S6 to determine the detection of chatter vibration, and if detected, the vibration frequency of the additional hydraulic pressure is determined again in S7, the additional hydraulic pressure is changed in S8, and the damping collar 15 is moved from the previous position to the front or rear. Slide to. If chatter vibration is not detected in S6, the end of machining is confirmed in S9. If not, the process returns to S6 to determine chatter vibration detection again. If the processing is finished, the position control is finished.

As described above, according to the spindle device 1 for a machine tool of the above-described embodiment, the vibration damping collar 15 provided in the spindle 2 and movable back and forth in the rotation axis direction of the spindle 2, the rotation speed of the spindle 2, and the size of the tool. The calculation device 24 for analyzing the vibration form of the main shaft 2 based on the processing conditions including the above and the bearing characteristics including the support rigidity and the damping coefficient of the bearing 4, and the damping collar 15 is rotated based on the analysis result of the calculation device 24. By providing a moving means (disc spring 16, pressurizing chamber 17, pressure oil supply path 18, control valve 20, hydraulic unit 21, NC device 26) for moving to a predetermined position (initial position) in the axial direction, processing Without changing the conditions, the damping effect of the damping collar 15 can be exerted to effectively suppress the vibration.

Particularly here, the chatter vibration generated during machining is analyzed by the arithmetic unit 24, and the damping collar 15 is moved to a position different from the initial position based on the analysis result, so that the natural frequency of the spindle 2 is changed during machining. The chatter vibration can be effectively suppressed by continuously changing the vibration.

In the above embodiment, the disc spring 16 as the urging means is arranged on the front side and the pressurizing chamber 17 is arranged on the rear side. A coil spring or the like can be used as the biasing means in addition to the disc spring. Further, the fluid supplied to the pressurizing chamber is not limited to oil, other fluids such as air and gas may be used, and the fluid supply path to the pressurizing chamber is not limited to the drawbar, but may be provided on the main shaft. Good.
The damping member is not limited to the damping collar of the above-described embodiment, but a metal other than steel or a combination of a plurality of metals can be used. Further, instead of a ring shape through which the drawbar penetrates, a plurality of hollow parts that accommodate vibration damping members such as spheres so as to be movable back and forth in the axial direction of the main shaft are provided on concentric circles around the drawbar, and for each hollow part. It is also possible to control the position of the damping member by providing a biasing means and a pressurizing chamber.

1・・Main spindle device, 2・・Main shaft, 3・・Motor, 4・・Bearing, 5・・Drawbar, 6・・Pressing mechanism, 7,16・・Disc spring, 12・・Hollow part, 13・・Control Vibration mechanism, 14・・Fixed collar, 15・・Vibration suppression collar, 17・・Pressurizing chamber, 18・・Pressure oil supply passage, 19・・Seal member, 20・・Control valve, 21・・Hydraulic unit, 22 ..Control device, 23..input device, 24..arithmetic device, 25..memory device, 26..NC device

Claims (3)

A spindle device for a machine tool, comprising a spindle in which a tool is detachable and rotatably supported in a housing via a bearing, a motor for rotating the spindle, and a controller for controlling the motor. ,
A damping member that is housed in a hollow portion formed in the main shaft and is movable back and forth in a rotation axis direction of the main shaft,
Vibration analysis means for analyzing a vibration form of the spindle based on machining conditions including the rotation speed of the spindle and the dimensions of the tool, and bearing characteristics including the support rigidity and damping coefficient of the bearing,
A machine including an NC device included in the control device, and a moving unit that moves the vibration damping member to a predetermined position in the rotation axis direction based on an analysis result of the vibration analysis unit. Machine spindle device. A vibration detecting means for detecting vibration generated on the spindle during processing is further provided, the vibration analyzing means analyzes vibration during processing detected by the vibration detecting means, and the moving means is the vibration analyzing means. The spindle device for a machine tool according to claim 1, wherein the vibration damping member is moved to a position different from the predetermined position based on the analysis result of 1. The vibration damping member is housed in a hollow portion formed in the main shaft so as to be movable back and forth, and the moving means is provided in the hollow portion and biases the vibration damping member forward or backward. A biasing unit, a pressurizing chamber formed on the opposite side of the biasing unit with the damping member interposed therebetween, to which a fluid is supplied, and a fluid pressure adjusting mechanism capable of adjusting the fluid pressure to the pressurizing chamber. The spindle device for a machine tool according to claim 1 or 2, comprising:

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