JPH0641781Y2 - Machine tool spindle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a spindle of a machine tool such as a gear finishing machine, and particularly to a spindle of a motor body type.

<Prior Art> In recent years, a hardened gear finisher (hard gear finisher) for efficiently finishing a gear after heat treatment has been developed. The quenching gear finisher uses a gear-shaped CBN (cubic boron nitride) grindstone (hereinafter simply referred to as a grindstone), and this grindstone is meshed with the gear to be machined with an axial crossing angle, and the grindstone and the gear to be machined. And are driven synchronously to generate a slip in the tooth trace direction, and the grindstone is pressed against the gear to be processed to finish the grinding of the gear to be processed.

A mechanism for synchronizing the grindstone and the gear to be processed will be described with reference to FIG.

The output shaft 2 of the drive motor 1 is provided with a gear-shaped grindstone 3, and the output shaft 2 is provided with a master drive gear 4 having the same number of teeth as the grindstone 3. The output shaft 2 located between the grindstone 3 and the master drive gear 4 is provided with a coupling 5 for removing backlash. On the other hand, the driven shaft 6 is provided with a processed gear 7 that meshes with the grindstone 3 and a master driven gear 8 that has the same number of teeth as the processed gear 7 that meshes with the master drive gear 4. The output shaft 2 and the driven shaft 6 are provided with a predetermined axis crossing angle.

When the output shaft 2 is rotated by the drive of the drive motor 1, the grindstone 3 is rotated and the master drive gear 4 is rotated via the coupling 5. By the rotation of the master drive gear 4, the gear 7 to be processed is passed through the master driven gear 8 and the driven shaft 6.
The workpiece gear 7 is driven in synchronization with the rotation of the grindstone 3 via the master drive gear 4 and the master driven gear 8.

However, according to the synchronizing mechanism shown in FIG. 3, since the grindstone 3 and the work gear 7 are synchronized via the master drive gear 4 and the master driven gear 8, the grindstone 3 and the work gear 7 It was necessary to prepare the master drive gear 4 and the master driven gear 8 according to the type. In addition, the master drive gear 4 and the master driven gear 8 must be replaced every time the gear 7 to be processed is changed, resulting in a large amount of setup change. Further, since the output shaft 2 and the driven shaft 6 have an axial intersection angle, the meshing state of the grindstone 3 and the gear 7 to be processed, the master drive gear 4 and the master driven gear 8
It was difficult to achieve accurate synchronization because the meshing state with the was different.

Therefore, as shown in FIG. 4, a grindstone drive motor 9 and a work drive motor which are independent of the grindstone 3 and the processed gear 7 are provided.
There is considered a quenching gear finishing machine which is driven and rotated by 10 and drives the grindstone drive motor 9 and the work drive motor 10 by numerical control to synchronize the rotations of the grindstone 3 and the gear 7 to be processed. .

This quenching gear finishing machine is useful because it can process even stepped gears and has less restrictions on the target work and is highly flexible, and in this case, the cutter shaft and the work shaft each have 1000 It is also possible to rotate at ~ 4000 rpm or more.

However, in order to realize such synchronization at high speed rotation, it is necessary to increase the resolution of the rotation sensor for each axis to several tens of times that of the conventional method. In addition, it is important to improve the rigidity and suppress the vibration in the rotation direction of the shaft as much as possible.

By the way, the present applicant previously applied for a spindle suitable for the above-mentioned quenching gear finishing machine.

This will be described with reference to FIG. 5. First, the main shaft 11 is supported by the case 13 via the left and right bearings 12a and 12b, and is integrated with the motor. That is, a so-called built-in motor is formed by fixing the rotor 14 of the drive motor to the main shaft 11 and the stator 15 of the same motor to the inner circumference of the case 13, and the main shaft 11 is rotationally driven by the rotor 14 and the stator 15 without backlash. As it is done, its rigidity is increasing.

On the other hand, a disk 16 is fixed to a part of the main shaft 11 using a key or the like, and a cylinder 17 surrounds the disk 16 and has a left and right bearings 18a,
It is rotatably attached to the main shaft 11 by 18b.

The cylindrical body 17 has a structure in which the disc 16 is sandwiched with a gap 19 between them.
A viscous fluid 20 such as silicone oil is enclosed in 19. Since the disc 16 is sandwiched, the cylindrical body 17 has a divided structure on the left and right sides and inside and outside.

The operation is such that when the motor is energized, the main shaft 11 rotates and the disc 16 also rotates at the same time. At this time, the cylindrical body 17 is viscous fluid 20 enclosed in the gap 19 between the disc 16 and the disc 16. Rotate with 16 and with spindle 11.

Now, when the main shaft 11 changes in rotation due to a load change or the like, the viscous fluid 20 tries to change the cylinder 17 with a delay, and the inertia damper effect enhances the rigidity of the main shaft 11 in the rotational direction to suppress vibration.

When the main shaft 11 is used as, for example, a cutter shaft and a work shaft of a quenching gear finisher, a gear-shaped cutter or a work 23 is provided near one shaft end by a nut 21 and a tool retainer 22 as shown in the drawing. It is installed. Further, near the other shaft end, a high-resolution first encoder (for example, an electromagnetic displacement sensor) 24 used for synchronously rotating both shafts and also for aligning the tool on both shafts are provided. Second encoder used with a laser as a light source
25 and is installed. The cylindrical body 25a of the second encoder 25 is fixed to the inner circumference of the case 13, and the rotating body 25b is fixed to the main shaft 11 via a fixing member 25c.

According to this main shaft 11, since the basic structure is a built-in motor type, there is no rattling of the drive system, and since the inertia damper is provided, rigidity in the rotational direction is increased and vibration is suppressed, and thus the cutter shaft that requires synchronous rotation. And the work axis, respectively, the resolution of each rotation sensor described above can be increased to enable ultra-high speed synchronous operation.

<Problems to be Solved by the Invention> However, in the spindle 11 described above, the first and second encoders 24, 25, etc. are mounted near the shaft end on the side opposite to the cutter or the work 23, whereby the inertia damper is provided. Is located in the middle of the shaft, the
When a torsional vibration occurs in the shaft, there is a problem that the damping effect by the inertia damper is small and the torsional vibration of the main shaft becomes large in a certain specific vibration frequency range (from about 1.0 KHz to about 1.8 KHz).

Then, this invention aims at providing the spindle of the machine tool which can improve a torsional vibration characteristic in a wider frequency range.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the main shaft of the machine tool according to the present invention is supported between two bearings between the bearings of the main shaft integrated with the motor and the motor part. A first inertia damper using a viscous fluid is provided on a shaft close to the second inertia damper using a viscous fluid on the side of the shaft opposite to the side where the tool is mounted and protruding outward from the bearing. Is provided.

<Action> In addition to the vibration suppressing effect of the built-in motor itself and the damping action of the first inertia damper, the damping action of the second inertia damper effectively provided at the shaft end allows the first inertia damper to move as shown in FIG. The torsional vibration of the grindstone shaft in the vibration frequency range from about 1.0 KHz to 1.8 KHz, which could not be reduced in the case of only, is significantly reduced, and the torsional vibration characteristics are improved in a wide frequency range.

<Embodiment> An embodiment of the spindle of a machine tool according to the present invention will be described below with reference to FIGS. 1 and 2, and FIG.
The same members as those shown in the drawings are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, the left and right bearings 12a, 12 of the main shaft 11
1st inertia damper D ₁ provided between b (disk 16 and cylinder 17
In addition to the above), a second inertia damper D ₂ is provided near the shaft end located outside the second encoder 25.

The second inertia damper D ₂ is fixed to the main shaft 11 by shrink fitting or the like and has a slightly wide circular plate 26 having a slightly deep annular groove portion 26a formed near the outer periphery of one side surface, and the annular groove portion 2 described above.
An iron damper ring 28 housed with a gap 27 in 6a.
And a viscous fluid such as silicone oil sealed in the gap
29 and a cover plate 30 that closes the opening surface of the annular groove portion 26a, the same operational effect as the above-mentioned first inertia damper D ₁ is obtained.

With such a configuration, when the main shaft 11 of the present embodiment is used as, for example, a grindstone shaft of a hard gear finisher, first, vibration in a low frequency region that affects pitch accuracy is a vibration suppressing effect of the built-in motor itself. That is,
It is improved by improving the servo characteristics and centering accuracy of the fixture. Next, it is difficult to follow 100 with an electric servo.
Vibrations in the middle frequency range, which affect the tooth traces in the vicinity of about 200 Hz, are suppressed by the first inertia damper D ₁ . Next, since the vibration in the high frequency region of 700 Hz or more, which overlaps with the natural frequency of the shaft system in the main shaft 11, cannot be completely covered by only the first inertia damper D ₁ , the second inertia damper D ₂ provided at the shaft end is provided. Is suppressed by.

FIG. 2 shows the result of the experiment in which the second inertia damper D ₂ was added in this way.

FIG. 2 is a graph showing the frequency characteristics of compliance when the main spindle 11 is used as a grindstone shaft. The solid line in the figure is the torsional vibration characteristic when the second inertia damper D ₂ is provided, and the broken line is the first inertia damper. This is the torsional vibration characteristic when only D ₁ is provided. The alternate long and short dash line shows the vibration characteristic of bending when the second inertia damper D ₂ is provided.

As can be seen from the graph above, the torsional vibration in the frequency range from about 1.0 KHz to about 1.8 KHz, which could not be reduced in the past, is greatly reduced.

The mounting position of the second inertia damper D ₂ is not limited to the above-mentioned position, and a slightly large-diameter shaft portion to which the first encoder 24 is mounted may be mounted.

<Effect of the Invention> As described above, according to the present invention, in addition to the first inertia damper provided in the middle portion of the main shaft, the second inertia damper is provided at the shaft end opposite to the tool.
Especially in the built-in motor, the torsional vibration can be suppressed in a wider frequency range, so that the resolution of the rotation sensor can be improved and the ultra-high speed synchronous operation can be performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a spindle of a machine tool according to the present invention, FIG. 2 is a graph showing frequency characteristics of compliance of a grindstone shaft, FIG. 3 is a perspective view showing a conventional synchronizing mechanism, and FIG. FIG. 5 is a principle view of a quenching gear finishing machine, and FIG. 5 is a sectional view of a conventional main shaft. In the drawings, reference numeral 11 is a spindle, D ₁ is a first inertia damper, 23
Is a cutter or work, and D ₂ is a second inertia damper.

Claims (1)

[Scope of utility model registration request] 1. A first inertia damper using a viscous fluid is provided between the bearings of a main shaft which is supported by two bearings and is integrated with a motor, and on a shaft which is close to a motor part, and a tool or the like is mounted on the shaft. A spindle of a machine tool, characterized in that a second inertia damper using a viscous fluid is provided on the side opposite to the bearing side and near the shaft end protruding outward from the bearing.