JP2867373B2 - Spindle unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle unit capable of coping with heavy cutting in which dynamic stiffness of a spindle system is required from light cutting in a machine tool.

[0002]

2. Description of the Related Art Conventionally, a rolling bearing is used as a spindle 1 of a machine tool. However, the bearing 1 has a high bearing rigidity and is excellent in maintainability and cost. However, there is a disadvantage that the damping property is not sufficient. For this reason, in order to improve the chattering resistance, a sliding bearing 4 is provided between the front bearing 2 and the rear bearing 3 and almost at the center of the main shaft 1 to serve as a squeeze film damper as shown in FIG. is there.

[0003]

However, since this type uses a slide bearing, it generates heat when rotated at high speed. Also, it is difficult to adjust the clearance with the main shaft, and if there is misalignment at the time of assembling, the sliding bearing has a large width, so that there is a single contact. Further, since the slide bearing is farther from the front bearing which is most effective as a damping action against chatter, a sufficient effect cannot be obtained. Although the damping action is performed almost uniformly during the machining, the satisfactory effect for a wide range of machining has not been obtained since the support rigidity of the main shaft is not automatically adjusted in connection with the vibration. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to improve the damping of a rolling bearing, suppress chattering, and enable light cutting to heavy cutting. It is intended to provide a spindle unit.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a head unit in which a front shaft and a rear portion are supported by a headstock by rolling bearings. An intermediate housing is interposed therebetween, the intermediate housing is supported on the headstock member by radial and thrust hydrostatic bearings, a brake disk is provided concentrically on the intermediate housing, and the headstock member side has When the pressurized oil supply of the hydrostatic bearing is confirmed, the brake disc is actuated to rotate the intermediate housing.
An electromagnetic brake that stops the provided mounting a vibration meter for detecting the vibration of the headstock, adjusts the hydraulic pressure supplied to the hydrostatic bearing
Provide a pressure regulating valve to perform the processing of the vibration level of the vibrometer
Threshold value Vo and hydrostatic bearing, which are standards based on accuracy
Caution when the vibration level does not drop at the maximum supply pressure
Is provided with a storage circuit that stores the maximum value Vm in advance,
The threshold Vi stored as the level Vi and the alert threshold
Vm, and when Vo <Vi <Vm, the hydrostatic bearing receives Vi.
Activates the pressure regulating valve so that pressure oil corresponding to
A comparison circuit that outputs an alarm when Vi> Vm.
It is a mess .

[0005]

The pressure oil is supplied to the hydrostatic bearing, and after the confirmation, the disc brake is operated. When the vibration level of the vibrometer due to processing exceeds a certain threshold, the hydraulic pressure of the supply for static pressure is adjusted by the control means to improve the damping of the hydrostatic bearing and increase the dynamic rigidity of the spindle system.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. For example, a rear housing 1 is attached to a headstock 11 of a known lathe.
2 and the front housing 13 are provided concentrically, and the front housing 13 is formed with a small diameter portion 13a corresponding to the position of a rolling bearing 15 described later. An intermediate housing 14 in which a deep annular groove 14a is cut in the outer periphery corresponding to the small diameter portion 13a is concentrically provided. A main shaft 17 is rotatably supported by a rolling bearing 15 fitted to the intermediate housing 14 and a rolling bearing 16 fitted to the concentric rear housing 12. A rotor 1 of a built-in motor 19 is provided on a tapered portion extending rearward of the main shaft 17.
9B is fitted concentrically. The stator 19A has a motor housing 18 provided with a cooling jacket 18a on the outer periphery.
To the headstock 11.

More importantly, a hydrostatic bearing is formed between the annular groove 14a of the intermediate housing 14 and the small diameter portion 13a of the front housing 13. That is, a hydrostatic pad 21a is cut at an angular position on the inner peripheral surface of the small-diameter portion 13a of the front housing 13 in the circumferential direction at a position equal to the number of the circumferential grooves in the intermediate housing 14, and flows through the throttle 22a. It is connected to the road 23. In addition, intermediate housing 1 is provided on front and rear side surfaces 13b, 13c of the small diameter portion of front housing 13.
The static pressure pads 21b and 21c are cut in opposition to the side surfaces 14b and 14c of the fourth annular groove 14a and correspond to the static pressure pads 21a.
3 is connected. Further, a brake disc 25 is concentrically mounted on the inner end surface of the intermediate housing 14, and an electromagnetic brake 26 for applying a brake is provided on the headstock 11 side. A vibrometer 30 for detecting the vibration level of the headstock during processing is installed on the front housing of the headstock 11.

In the block diagram of FIG. 1, 31 is a hydraulic pump, 32 is an oil temperature controller for adjusting the temperature of oil supplied to the built-in motor 19 and the static pressure pad, and 33 is an electromagnetic controller for adjusting oil pressure supplied to the static pressure pad. The proportional pressure regulating valve 34 is a safety relief valve. A control device 40 includes the following circuits. 41 is a hydraulic pressure P supplied to the hydrostatic pad to increase the damping of the spindle system when the vibration level reaches a certain value.
The threshold value V ₀ for increasing s and the warning threshold value Vm when the vibration level of the vibrometer 30 does not fall below the threshold value even at the maximum value Psm of the supply oil pressure of the hydrostatic bearing are input and stored by MDI or the like. Memory circuit. 42 is the vibration level V of the vibration meter 30
Alarm when i is, supplies the corresponding hydraulic fluid Ps to operate the electromagnetic proportional pressure control valve 33 when in the meantime by comparing whether between V ₀ and Vm, which Vi is greater than Vm Outputs a comparison circuit that stops the machine operation. 43
Is an electromagnetic brake actuation circuit that activates the disc brake when it is confirmed that hydraulic oil has been supplied to the hydrostatic bearing;
Reference numeral 4 denotes a drive circuit for the built-in motor 19, which includes these components.

[0009] In this way those configurations also fall vibration level raised to supply the maximum pressure Psm threshold V ₀ and hydrostatic bearing as a reference determined in relation to the pre-vibration level of machining accuracy When there is no warning threshold value Vm, it is determined and stored in the storage circuit 41. The workpiece is gripped by a chuck (not shown) at the tip of the main shaft 17, the built-in motor 19 is driven by the built-in motor drive circuit 44, and the main shaft 17 is rotated. The oil pressure is adjusted to an appropriate temperature by the oil temperature controller 32, and the pressure oil sent by the hydraulic pump 31 is statically moved from the oil passage 23 through the throttles 22 a, 22 b, 22 c at the initial oil pressure Ps ₁ determined by the electromagnetic proportional pressure regulating valve 33. The intermediate housing 1 is supplied to the pressure pad,
Bearing 4 When a confirmation that the supply pressure oil has been sent to the hydrostatic bearing is output, the electromagnetic brake operation circuit 43 sets the electromagnetic brake 2
6 is actuated to brake the brake disk 25 and stop the intermediate housing 14 from turning.

Further, the pressure oil is supplied to the cooling jacket 18a of the motor housing of the built-in motor 19 through the flow path 24.
To cool the stator 19A. In this state, the tool rest (not shown) is NC-controlled, and the workpiece held by the chuck fitted to the spindle 17 is processed. The vibrometer 30 installed on the headstock 11 by the cutting detects the vibration during the processing in-process, and the vibration level is input to the comparison circuit 42 of the control device 40 every moment. Comparison circuit 4
2, V ₀ <V between the storage value V ₀ · Vm of the storage circuit 41.
It is determined that Vi <Vm, and if V ₀ > Vi, the electromagnetic proportional pressure regulating valve 33 continues to be at the initial oil pressure Ps ₁ . Cutting becomes heavy cutting and the vibration level of the vibrometer 30 is V
If the comparison circuit 42 determines that the state of ₀ <Vi <Vm is satisfied,
Electromagnetic proportional pressure control valve acts to reduce the vibration level increases the attenuation of the static pressure bearings increases the supply pressure Ps ₂ correspond to the magnitude of the vibration level Vi. And the dynamic rigidity of the spindle system is increased by improving the damping property of the spindle system.
In the comparison circuit 42, if Vi> Vm, an alarm is output and the built-in motor driving circuit 44 controls the built-in motor to stop the rotation of the main shaft.

[0011]

As described above, the present invention has the following effects. The supply pressure of the hydrostatic bearing is changed according to the vibration level, so that the damping of the main shaft system is improved and the bearing rigidity is improved. In addition, vibration during machining of the headstock due to cutting can be detected in-process, and chatter can be suppressed, so that machining from light cutting to heavy cutting can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a spindle unit of the present invention.

FIG. 2 is an explanatory diagram of a conventional spindle unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Headstock 12 Rear housing 13 Front housing 14 Intermediate housing 15, 16 Rolling bearing 17 Main shaft 19 Built-in motor 21a, 21
b, 21c Static pressure pad 22a, 22b, 22c Throttle 25 Brake disk 26 Electromagnetic brake 30 Vibrometer 31 Hydraulic pump 32 Oil temperature controller 40 Control device

Claims (1)

(57) [Claims] In a spindle unit in which a front shaft is supported on a headstock by a rolling bearing at a front portion and a rear portion, an intermediate housing is interposed between the front rolling bearing and the headstock member, and the intermediate housing is mounted on the headstock. The bearing is supported by radial and thrust hydrostatic bearings on the member, a brake disk is provided concentrically on the intermediate housing, and the brake disk is provided on the headstock member side when the supply of pressurized oil from the hydrostatic bearing is confirmed. To rotate the intermediate housing
An electromagnetic brake that stops the provided mounting a vibration meter for detecting the vibration of the headstock, adjusts the hydraulic pressure supplied to the hydrostatic bearing
Provide a pressure regulating valve to perform the processing of the vibration level of the vibrometer
Threshold value Vo and hydrostatic bearing, which are standards based on accuracy
Caution when the vibration level does not drop at the maximum supply pressure
Is provided with a storage circuit that stores the maximum value Vm in advance,
The threshold Vi stored as the level Vi and the alert threshold
Vm, and when Vo <Vi <Vm, the hydrostatic bearing receives Vi.
Activates the pressure regulating valve so that pressure oil corresponding to
A comparison circuit that outputs an alarm when Vi> Vm.
Spindle unit, characterized in that only composed.