JP2003089026A - Main spindle device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rigidity or machining accuracy of a machine tool from decreasing by maintaining load carrying capacity of fluid bearings at a required value irrespective of a change in rotating speed of a spindle that is effected by a machining condition. SOLUTION: A spindle device for the machine tool comprises the main spindle 1 rotatably supported via the fluid bearings 2 and driven by a power source 6, a variable pressure control valve 13 for controlling pressure of pressure fluid supplied to the fluid bearings from a pump 10 driven by a power source 9, a rotating speed detecting means 5 for detecting the rotating speed of the main spindle, a load detecting means 14 for detecting load on the main spindle, and a controller 12 which controls the set value for the load carrying capacity based on a load detection signal from the load detecting means, has a relation between the rotating speed and the pressure of the fluid set in relation to the set value for the load carrying capacity of the fluid bearings and regulates the variable pressure control valve based on a rotating speed detection signal from the rotating speed detecting means and the load detection signal from the load detecting means to maintain the load carrying capacity of the fluid bearings at the specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device for machine tools, for example, a grindstone spindle device for a grinder.

[0002]

2. Description of the Related Art In a wheel head of a conventional grinding machine shown in FIG. 4, a wheel shaft 1 is rotatably supported via two fluid bearings 2 at the front and rear in the axial direction. A grinding wheel 3 is attached to the front end of the grindstone shaft 1, and a pulley 4 and an encoder 5 are attached to the rear end thereof. The pulley 7 attached to the motor shaft of the motor 6 and the pulley 4 of the grindstone shaft 1 are endless. The belt 8 is wound around. The discharge port of the pump 10 driven by the motor 9 and each fluid bearing 2 are connected by a pipe line / passageway 11 in which a fixed pressure control valve 15 is interposed.

In the grinder, a grindstone shaft 1 that is rotationally driven by a motor 6 via a belt transmission mechanism, that is, a grindstone wheel 3
When a workpiece (not shown) is ground by means of grinding, the load on the grindstone shaft 1 due to grinding resistance is that the pressure fluid from the pump 10 driven by the motor 9 passes through the fixed pressure control valve 15 and the pipeline / passage 11 Supported by fluid bearings 2, 2.

[0004]

The load capacity C of the fluid bearing 2 is determined by the fluid pressure P supplied to the fluid bearing 2 and the rotational speed N of the grindstone shaft 1. That is, when the fluid pressure P is constant, the rotational speed N of the grindstone shaft and the load capacity C of the fluid bearing 2 increase / decrease in a consistent manner.
When the rotational speed N of the grindstone shaft 1 is reduced under grinding conditions or the like, the load capacity C of the fluid bearing 2 is also reduced, that is, the rigidity is reduced,
As a result, the processing accuracy decreases (see FIG. 5). Therefore,
In one grinding machine, in order to avoid a decrease in rigidity, that is, a decrease in processing accuracy, the range of change in the rotational speed of the grindstone shaft, that is, the range of the workpiece / grinding condition, etc. is limited.

The present invention, in machining with a machine tool,
Regardless of changes in the rotation speed of the spindle due to workpieces, processing conditions, etc.,
The load capacity of the hydrodynamic bearing is maintained at a required value, rigidity, that is, deterioration of machining accuracy is suppressed, and machining of a wide range of workpieces, machining conditions, and the like is made possible.

[0006]

The spindle device of the present invention comprises:
A spindle of a machine tool that is rotatably supported by a fluid bearing and is rotatably driven by a power source, a variable pressure control valve that controls the pressure of pressure fluid supplied from a pump driven by a power source to the fluid bearing, a spindle. The rotation speed detecting means for detecting the rotation speed of the fluid bearing and the relationship between the rotation speed and the fluid pressure under the set value of the load capacity of the fluid bearing are set, and the load capacity of the fluid bearing is maintained at the set value. Thus, the controller for adjusting the variable pressure control valve based on the rotation speed detection signal from the rotation speed detection means is configured.

Further, a load detecting means for detecting a load on the main shaft, for example, a displacement gauge for detecting a radial displacement of the main shaft in the fluid bearing or a means for detecting a power load of the drive means for the main shaft is provided, and the controller is The set value of the load capacity is controlled based on the load detection signal of the load detection means, and the relationship between the rotational speed and the fluid pressure under the set value of the load capacity of the fluid bearing is set. The variable pressure control valve may be adjusted based on the rotation speed detection signal from the rotation speed detection means and the load detection signal from the load detection means so that the load capacity is maintained at a predetermined value.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments of the present invention, a grindstone spindle device of a grinder is exemplified as a spindle device of a machine tool, and it will be described with reference to the drawings. In the first embodiment of the present invention shown in FIG. 1, a grindstone shaft 1 in a grindstone base of a grinder has a fluid bearing 2 at two front and rear positions in an axial direction.
It is rotatably supported via 2. A grinding wheel 3 is attached to the front end of the grindstone shaft 1, and a pulley 4 and an encoder 5 are attached to the rear end thereof. The pulley 7 attached to the motor shaft of the motor 6 and the pulley 4 of the grindstone shaft 1 are endless. The belt 8 is wound around.

The discharge port of the pump 10 driven by the motor 9 and each fluid bearing 2 are connected by a pipe line / passage 11, and in the pipe line 11, a controller 12 is connected to a controller 12.
The variable pressure control valve 13 controlled based on the control signal from the controller 2 is interposed, and the controller 12 is connected to the encoder 5 provided on the grindstone shaft 1 to detect the grindstone shaft rotation speed detection signal from the encoder 5. The variable pressure control valve 13 is adjusted based on the above.

In the controller 12, the relationship between the rotational speed N and the fluid pressure P under a predetermined value of the load capacity C of the fluid bearing 2 is set. That is, the controller 12 controls the fluid pressure P supplied to the fluid bearing 2 in accordance with the rotation speed N of the grindstone shaft 1 so that the load capacity C of the fluid bearing 2 set to a desired value is kept constant. It is like this.

As means for detecting the rotational speed N of the grindstone shaft 1, instead of the encoder 5 of the grindstone shaft 1, based on the output value of the motor 6 of the grindstone shaft 1 or the rotational speed data of the grindstone shaft 1 in the numerical control grinder. A detection means may be used. In the grinder, when a grindstone shaft 1 rotatably driven by a motor 6 via a belt transmission mechanism, that is, a grindstone 3 grinds a workpiece (not shown), a load on the grindstone shaft 1 due to grinding resistance is , Supported by the fluid bearing 2.

The fluid bearing 2 will be described with reference to FIG. As shown in FIG. 3, the bearing member 21 of the fluid dynamic bearing 2 includes a cylindrical inner sleeve 22 that rotatably supports the outer peripheral surface of the grindstone shaft 1 (not shown) on the inner peripheral surface of a cylindrical bearing casing 23. , And is fitted and integrated by press fitting, shrink fitting, or the like.

On the inner peripheral surface of the inner sleeve 22 which serves as a bearing surface, static pressure pockets 24 are appropriately formed in the circumferential direction at equal intervals. In the example shown in FIG. 3, the static pressure pocket has a quadrilateral shape, but the shape is not particularly limited in the present invention. The area other than the static pressure pockets 24 on the inner peripheral surface of the inner sleeve 22 becomes the land 25.

As shown in FIG. 3, the inner sleeve 22
A circumferential groove is formed on the outer peripheral surface over the entire circumference except for both side ends, and when the inner sleeve 22 is fitted in the bearing casing 23, the groove is inside the bearing casing 23. An oil supply circumferential passage 26 is formed together with the peripheral surface. A pipe line / passage 11 is connected to the refueling circumferential passage 26 as shown in FIG.
It is communicated with the central portion of the static pressure bocket 24 via.

The fluid discharged from the pump 10 is
It is supplied to the static pressure pocket 24 through the passage 11, the oil supply circumferential passage 26 and the oil supply hole 27. The fluid supplied to the static pressure pocket 24 is introduced into the gap between the adjacent land 25 and the grindstone shaft 1 (not shown), and the fluid leaking from this gap is discharged to the oil tank. Thus, the hydrodynamic bearing 2 functions as a hydrostatic bearing in the hydrostatic pocket 24, and the fluid existing in the gap between the land 25 and the outer peripheral surface of the grindstone shaft 1 is dynamically compressed by the wedge action in the rotation of the grindstone shaft 1. Occurs, and the dynamic pressure effect of the fluid bearing 2 is also added.

The load capacity C of the fluid bearing 2 changes depending on the working pressure generated at this time. That is, if the fluid pressure P supplied to the static pressure pocket 24 is constant, the wedge action in the rotation of the grindstone shaft 1 increases as the rotational speed of the grindstone shaft 1 increases, so that the outer peripheral surfaces of the land 25 and the grindstone shaft 1 are increased. That is, the dynamic pressure generated in the gap between and increases, and the load capacity C of the fluid bearing 2 increases.

The load capacity C of the fluid bearing 2 is determined by the fluid pressure P supplied to the fluid bearing 2 and the rotational speed N of the grindstone shaft 1. That is, when the fluid pressure P is constant, the rotational speed N and the load capacity C coincide with each other and thus increase or decrease. Therefore, when the rotational speed N of the grindstone shaft 1 is changed due to the workpiece / grinding conditions, etc. The speed N is detected by the detection means (encoder 5, etc.), and the detection signal is input to the controller 12.

Then, in the controller 12, the fluid pressure corresponding to the detected rotation speed N is determined based on the relationship between the rotation speed N and the fluid pressure P under a preset constant load capacity C. Since the control signal is input to the variable pressure control valve 13 so as to become P, the variable pressure control valve 13 is adjusted by it.

Thus, the fluid pressure P of the fluid supplied from the pump 10 driven by the motor 9 to each fluid bearing 2 via the conduit / passage 11 is adjusted up and down by the adjusted variable pressure control valve 13. Even if the rotational speed N of the grindstone shaft 1 changes, the load capacity C of the fluid bearing 2 is maintained at the set predetermined value (see FIG. 5). Therefore, in the grinding process, it is possible to prevent a decrease in processing accuracy due to a change in the load capacity of the grindstone shaft 1.

In another embodiment shown in FIG. 2, the spindle device of the embodiment shown in FIG. 1 is further provided with load detecting means for detecting a load on the grinding wheel 3, that is, the grinding wheel shaft 1, and the load detecting means. Is connected in parallel with the encoder 5 for inputting the rotation speed signal so as to input the load detection signal to the controller 12.

As the load detecting means for detecting the load on the grinding wheel 3, that is, the grindstone shaft 1, for example, note that the load on the grindstone shaft 1 corresponds to the radial position of the grindstone shaft 1 in the fluid bearing 2. The displacement gauge 14 for detecting the radial position of the grindstone shaft 1 in the fluid bearing 2 is the fluid bearing 2
It is provided at the site. The displacement gauge 14 is, for example, an eddy current type displacement gauge or the like for non-contact detection.

The controller 12 adjusts the variable pressure control valve 13 so as to control the fluid pressure P supplied to the fluid bearing 2 in accordance with the rotational speed N of the grindstone shaft 1 and the load of the grindstone shaft 1. It is supposed to do. That is, in the controller 12, the set value of the fluid pressure P is adjusted to the minimum pressure increase tendency required to maintain the position detection signal at the neutral position.

As a means for detecting the load on the grindstone shaft 1 by treating the load on the grindstone wheel 3, that is, the grindstone shaft 1 as the power load of the motor 6 of the grindstone shaft 1, instead of the displacement meter 14,
A means for detecting the power load of the motor 6 of the grindstone shaft 1 (for example, a current sensor for detecting the load current of the motor 6) may be used.

Even under the same rotation of the grinding wheel 3, the load on the grinding wheel 3, that is, the grindstone shaft 1 is different depending on the processing conditions. Therefore, in the above-described embodiment, the fluid bearing 2 is operated in the processing condition range. Sufficient load capacity C is set.
In addition, the load capacity C must be changed and set according to the change in the processing conditions.

However, when the load capacity C is set to one and the load during machining is reduced, useless fluid pressure is supplied to the fluid bearing 2. However, the embodiment shown in FIG. In the above, since the detection signal corresponding to the load from the load detecting means (displacement meter 14 or the like) is input to the controller 12, it is necessary to maintain the detection position at the neutral position or the power load at a predetermined value. Since the set value of the fluid pressure P is adjusted to the lowest pressure increasing tendency, useless fluid pressure is not supplied, and the power consumption of the motor 9 that drives the pump 10 is saved.

[0026]

In the spindle device according to the present invention, the fluid pressure of the fluid supplied to the fluid bearing is increased / decreased by the variable pressure control valve adjusted by the controller, so that the rotational speed of the spindle changes. The load capacity of the fluid bearing is maintained at a predetermined value set in the controller (see FIG. 5). Therefore, problems such as machining errors due to changes in the load capacity of the spindle do not occur, and further, machining of workpieces, machining conditions, etc. in a wide range is made possible.

Furthermore, under one set value of the load capacity,
When the load is reduced during machining, useless fluid pressure is supplied to the fluid bearing, but the fluid pressure tends to be the minimum pressure increase necessary to maintain a predetermined value based on the load detected by the load detection means. Since the set value of the pressure is adjusted, useless supply of fluid pressure, that is, power is saved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a spindle device of a grinding machine according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a spindle device of a grinding machine according to another embodiment of the present invention.

FIG. 3 is a cross-sectional perspective view of a radial shaft device of a main shaft device of a grinding machine according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a spindle device of a grinding machine in a conventional technique.

FIG. 5 is a graph showing the relationship between the fluid pressure / load capacity of the fluid bearing of the spindle device of the grinder and the rotational speed of the grindstone shaft.

[Explanation of symbols]

1 wheel axis 2 fluid bearing 3 grinding wheel 4 pulley 5 encoder 6 motor 7 pulley 8 Endless belt 9 motors 10 pumps 11 pipelines / passages 12 Controller 13 Variable pressure control valve 14 Displacement meter

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[Procedure amendment]

[Submission date] October 29, 2001 (2001.10.
29)

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

Continued front page    (72) Inventor Toshihiko Shima             1-1 Asahi-cho, Kariya city, Aichi             Machine Co., Ltd. (72) Inventor Ryohei Mukai             1-1 Asahi-cho, Kariya city, Aichi             Machine Co., Ltd. F-term (reference) 3C034 AA20 BB07 CA17 CB06 CB18                 3C048 CC07 DD13 EE07                 3J102 AA02 BA03 BA17 CA11 CA32                       CA36 EA03 EA06 EA09 EB01                       EB03 EB07 GA07

Claims (4)

[Claims] 1. A rotatably supported bearing via a fluid bearing,
A main shaft rotated by a power source, a variable pressure control valve for controlling the pressure of pressure fluid supplied from a pump driven by a power source to a fluid bearing, a rotation speed detection means for detecting the rotation speed of the main shaft, and a fluid bearing The relationship between the rotational speed and the fluid pressure under the set value of the load capacity of is set, and the rotational speed detection signal from the rotational speed detection means is set so that the load capacity of the fluid bearing is maintained at the set value. Machine tool spindle device consisting of a controller that adjusts a variable pressure control valve based on. 2. A rotatably supported via a fluid bearing,
A spindle driven by a power source, a variable pressure control valve that controls the pressure of the pressure fluid supplied from a pump driven by a power source to a fluid bearing, a rotation speed detection unit that detects the rotation speed of the spindle, and a load on the spindle. The load detecting means for detecting the load capacity and the load capacity setting value are controlled based on the load detecting signal of the load detecting means, and the relationship between the rotational speed and the fluid pressure under the load capacity setting value of the fluid bearing is Is set,
A controller for adjusting the variable pressure control valve based on the rotation speed detection signal from the rotation speed detection means and the load detection signal from the load detection means so that the load capacity of the fluid bearing is maintained at a predetermined value. Machine tool spindle device. 3. The spindle device for a machine tool according to claim 2, wherein the load detecting means is a displacement gauge that detects a radial displacement of the spindle in the fluid bearing. 4. The spindle device for a machine tool according to claim 2, wherein the load detection means is means for detecting a power load of the drive means for the spindle.