JP3500530B2 - Spindle device of machine tool and monitoring method thereof - 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 device for a machine tool in which a spindle is rotatably supported by a housing via a rolling bearing such as an angular ball bearing, and a monitoring method thereof.

[0002]

2. Description of the Related Art As a spindle device for machine tools, one shown in FIG. 5 is known. In this main spindle device, two sets of front and rear main spindles 2 are provided in a housing 1 (the left side in FIG. 5 is the front).
An electric motor 6 which is rotatably supported by the rolling bearings 3 and 4 and rotates the main shaft 2 is provided between the rolling bearings 3 and 4, and between the housing 1 and the rolling bearing 4 on the rear side. , The movable sleeve member 7 is fitted to the outer ring of the rolling bearing 4 and is slidably inserted in the axial direction of the main shaft 2 by the slide ball bearing 8, and is biased rearward by the preload spring 9 to preload the rolling bearing. It has a structure to apply. The housing 1 has a rear member (rear housing) 1a that is detachably fixed integrally with a bolt 11 at the rear end thereof, and the movable sleeve member 7 is fitted and inserted in the rear member 1a. The slide ball bearing 8 is used to prevent a large amount of thermal expansion between the rolling bearings 3 and 4 due to a temperature change of the motor 6 or the like, which is a heating element, and prevent rattling.

A spindle device for machine tools shown in FIGS. 6 and 7 is also known (Japanese Patent Laid-Open No. 10-225802). This spindle device includes a housing 1 (rear member 1a).
The oil inflow space Sa, the circulation gap g, and the oil outflow space Sb are alternately formed in the circumferential direction between the inner peripheral surface of the movable sleeve member 7 and the outer peripheral surface of the movable sleeve member 7. By flowing from the oil inflow space Sa to the oil outflow space Sb through the circulation gap g, the movable sleeve member 7 is floated and supported by the pressure of the hydraulic oil. Since the other structures are the same as those of the spindle device of FIG. 5, the same members are given the same reference numerals and the description thereof is omitted.

[0004]

In the former spindle device shown in FIG. 5, a preload is applied to the slide ball bearing 8 to prevent rattling, and a large radial thermal expansion force and cutting reaction force act. Therefore, a ball indentation may occur on the movable sleeve member 7 or the rear member 1a of the housing 1, and the indentation may slow down the movement of the movable sleeve member 7 and seize the rolling bearings 3 and 4.

The latter hydrostatic bearing type spindle device shown in FIGS. 6 and 7 has the following problems. (A) Since the structure in which the movable sleeve member is held in the center by hydraulic pressure, an oil circulation device 13 with a very large hydraulic oil pressure is required, and in order to suppress the temperature rise of the hydraulic oil due to pressurization, it is large. The large-sized temperature control device 14 having a cooling capacity commensurate with the oil circulation device 13 is required, and not only the manufacturing cost but also the operating cost becomes expensive. (B) In addition, since the oil inflow space Sa, the circulation gap g, and the oil outflow space Sb must be alternately formed in three (or four or more), the internal structure becomes complicated, and the cost is also increased in this respect. Become.

(C) In order to have a function as a hydrostatic bearing, pipe passages are provided from the oil circulation device 13 to the oil inflow space Sa and the oil outflow space Sb, respectively. The structure becomes more complicated, such as addition, and the cost becomes higher.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spindle device for a machine tool and a method for monitoring the same, in which the movable sleeve member can be smoothly moved in the axial direction and a large supporting rigidity and load capacity can be obtained. Another object of the present invention is to provide a spindle device of a machine tool capable of stabilizing the bearing preload and a monitoring method thereof.

[0008]

In order to achieve at least one of the above-mentioned objects, the invention according to claim 1 is a spindle device for machine tools, wherein a spindle is rotatably supported by a rolling bearing in a housing. , Between the housing and the rolling bearing, the movable sleeve member is fitted to the outer ring of the rolling bearing and is movably inserted in the axial direction of the main shaft, and the lower half of the inner peripheral surface of the horizontally arranged housing is , A hydraulic chamber for applying buoyancy to the movable sleeve member by hydraulic oil is formed between the lower surface of the outer peripheral surface of the movable sleeve member and the oil supply hole, and the upper part of the hydraulic chamber A throttle gap that resists the outflow of hydraulic oil is formed between the inner peripheral surface of the housing and the outer peripheral surface of the movable sleeve member so as to communicate with the oil discharge hole.

With this means, when hydraulic oil is supplied from the oil supply hole to the hydraulic chamber, the hydraulic oil pressure in the hydraulic chamber increases due to the outflow resistance of the throttle gap, and buoyancy acts on the movable sleeve member. Therefore, the downward load on the movable sleeve member applied to the housing is reduced, and the axial frictional resistance between the housing and the movable sleeve member is reduced. Also, the hydraulic oil is
The housing and the movable sleeve member are cooled to suppress the temperature rise between them and maintain a proper gap between them.

In the spindle device for a machine tool according to claim 1, the movable sleeve member can be provided with a preload means (claim 2). With this configuration, the bearing preload is stabilized. The preloading means includes a constant preloading means using a spring or the like and a fixed position preloading means using hydraulic pressure or the like. These can be used alone or in combination.

In the spindle device for a machine tool according to claim 1 or 2, it is preferable that the linear expansion coefficient of the housing be larger than the linear expansion coefficient of the movable sleeve member (claim 3). With this configuration, even if there is a temperature difference in the direction in which the temperature of the movable sleeve member closer to the rolling bearing, which is the heat source, than the housing rises, the reduction in the gap between the housing and the movable sleeve member is reduced, so The gap can be set small. For example, the movable sleeve member may be made of steel, and the housing may be made of aluminum or brass having a larger linear expansion coefficient than steel.

In the spindle device for a machine tool according to any one of claims 1 to 3, it is preferable to form bearing gaps smaller than those in front and rear sides of the hydraulic chamber and the throttle gap, respectively. 4). With this configuration, the bearing gap is the smallest and the aperture gap is larger than this, so even if the movable sleeve member moves radially and its outer peripheral surface partially contacts the inner peripheral surface of the housing (contact The bearing clearance of the part is zero), and the throttle clearance is not closed.

In the spindle device for a machine tool according to claim 4, it is preferable that the front-back width of the throttle gap is smaller than the front-back width of the hydraulic chamber (claim 5). With this configuration, the change in the diaphragm function of the diaphragm gap due to the radial movement or expansion of the movable sleeve member can be suppressed.

In the spindle device for a machine tool according to a third aspect of the present invention, bearing gaps smaller than the hydraulic chamber and the front and rear sides of the throttle gap are respectively formed, and the housing and the movable sleeve member have the same minimum operating temperature range. It is preferable to set the bearing gap so as not to become zero when the temperature is reached (claim 6). In this configuration, if the housing and the movable sleeve member have the same temperature in the operating temperature range, the bearing gap can be surely secured due to the difference in linear expansion coefficient.

The invention according to claim 7 is the invention according to claims 1 to 6.
In the spindle device of the machine tool described in any one of 1, a monitoring sensor such as a flow sensor for detecting the flow rate of the hydraulic oil supplied to the hydraulic chamber or a temperature sensor for detecting the temperature of the housing is provided. The main spindle device is monitored by detecting the hydraulic oil flow rate and housing temperature.

In this means, for example, when the value detected by the monitoring sensor becomes abnormal, an alarm is issued or the spindle rotation is stopped. It is also possible to provide both a temperature sensor and a flow rate sensor as the monitoring sensor, and when the temperature is out of the set range, it can be determined from the detection signal of the flow rate sensor at that time whether or not the alarm is actually issued.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the accompanying drawings. 1 to 4 show an embodiment of a spindle device of a machine tool according to the present invention. Since the basic structure of the spindle device of the machine tool is the same as that of the spindle device of the machine tool of FIG. 5, the same members are designated by the same reference numerals and the description thereof is omitted.

A cover member 1b is integrally attached to the rear member 1a with a bolt 23, and a movable sleeve member 7 is provided.
A bearing retainer 7a and a spring retainer 7b are integrally attached to the front and rear ends of the with bolts 25 and 26, respectively. The rear member 1a has a temperature sensor 20. In addition, bolt 1
Although only one of each of 1, 2, 25, and 26 is shown in FIG. 1, a plurality of them are arranged in an annular shape.

Between the lower half of the inner peripheral surface of the rear member 1a of the housing 1 in a horizontal state and the lower half of the outer peripheral surface of the movable sleeve member 7 facing the rear member 1a, the hydraulic chamber Oa is connected to the oil supply hole 1c. And the housing 1
Between a substantially upper half of the inner peripheral surface of the rear member 1a and a substantially upper half of the outer peripheral surface of the movable sleeve member 7 facing the rear peripheral member 1a,
An oil discharge chamber Ob is formed in communication with the oil discharge hole 1d, and
A throttle gap t, t between the hydraulic chamber Oa and the oil discharge chamber Ob that creates a pressure difference between the oil discharge chamber Ob and the hydraulic pressure chamber Oa by resisting the outflow of hydraulic oil flowing from the hydraulic chamber Oa to the oil discharge chamber Ob. Are formed.

Bearing clearances c are formed on both sides of the hydraulic chamber Oa, the throttle gap t, and the oil discharge chamber Ob over the entire inner and outer peripheral surfaces of the rear member 1a and the movable sleeve member 7.
A ring-shaped seal member 27 is attached to the rear member 1a to make the bearing gap c liquid-tight.

The rear member 1a is made of a material having a larger linear expansion coefficient than the movable sleeve member 7, for example, aluminum or brass when the movable sleeve member 7 is steel.
The front-rear width W3 of the throttle gap t is smaller than the front-rear width W2 of the hydraulic chamber Oa and the oil discharge chamber Ob. Further, the size δ1 of the bearing clearance c is set so as not to become zero under the condition that the rear member 1a and the movable sleeve member 7 are at the same temperature which is the lowest in the operating temperature range.
It is smaller (minimum) than the size of.

The oil supply hole 1c and the oil discharge hole 1d are formed in the rear member 1a of the housing 1. The oil supply hole 1c is connected to an oil cooler 29 with a pump by a supply pipe 28, and the oil discharge hole 1c. An oil drain pipe 31 having a flow rate sensor 30 is connected to 1d. The supply pipe 28 has an electromagnetic flow rate adjusting valve 32, and the branch pipe 33 of the supply pipe 28 is provided with an electromagnetic relief valve 34. Oil cooler with pump 29
May have a structure in which an oil pump and an oil cooler are separated from each other, or may be an oil pump only in some cases.

The electromagnetic flow rate adjusting valve 32 adjusts the flow rate of the working oil (cooling oil) supplied from the oil cooler 29 with a pump through the supply pipe 28 to the hydraulic chamber Oa. Further, in the electromagnetic relief valve 34, the buoyancy F expressed by the following equation (1) has a magnitude δ 1 of the throttle gap t and the bearing gap c,
It is used to set an upper limit on the hydraulic oil supply pressure so that it does not become too large due to fluctuations in δ2. F ≈ W1 x W2 x (PA-PB) (1) where, W1; vertical projection width PA of hydraulic chamber Oa; hydraulic oil pressure PB in hydraulic chamber Oa; hydraulic oil pressure in drain chamber Ob

The bearing gap c in the portion of the throttle gap t whose front-rear width W3 is smaller than the front-rear width W2 of the oil pressure chamber Oa and the oil discharge chamber Ob also functions as a throttle and resists the flow of hydraulic oil, but The load capacity between the member 1a and the movable sleeve member 7 and the fitting thereof are mainly determined, and the ratio of controlling the flow of the hydraulic oil is reduced.

Next, the operation of the spindle device of the machine tool configured as described above will be described. The relief valve 34 is set so that the buoyancy F is equal to or less than the supporting load applied to the point bearing 4 of the main shaft 2 including the movable sleeve member 7, and the oil cooler 29 with a pump is operated to supply hydraulic oil to the hydraulic chamber Oa. Then, the main shaft 2 is rotated by the motor 6 while being supplied to.

From the oil cooler 29 with a pump to the hydraulic chamber Oa
Of the hydraulic oil supplied to the oil discharge chamber Ob through the throttle gap t.
And the rear member 1a and the movable sleeve member 7 are cooled to reduce the temperature difference between them. At this time, the action of the throttle gap t causes a pressure difference between the hydraulic chamber Oa and the oil discharge chamber Ob to move the movable member. Since the buoyancy F acts on the sleeve member 7, the frictional resistance in the axial direction of the movable sleeve member 7 with respect to the rear member 1a is reduced. Therefore, when the main shaft 2 thermally expands due to the heat generation of the motor 6 or the like, the movable sleeve member 7 smoothly moves in the axial direction together with the main shaft 2 to prevent a trouble caused by the thermal expansion. Further, since the movable sleeve member 7 smoothly moves in the axial direction as described above, the preload spring 9 applies an appropriate preload to the rolling bearings 3 and 4 as designed.

In the above, the motor 6 and the rolling bearing 4
Even if the temperature of the movable sleeve member 7 and the rear member 1a rises due to the heat generated by, the linear expansion coefficient of the rear member 1a is made larger than the linear expansion coefficient of the movable sleeve member 7, and the temperature of the movable sleeve member 7 ≧ the rear member Since the temperature is 1a,
Since the bearing clearance c (δ1) becomes zero, the movable sleeve member 7
The outer peripheral surface of does not contact the inner peripheral surface of the rear member 1a.

By the way, in the present invention, the rear member 1
Although it is possible to manufacture a by using a material having a coefficient of linear expansion equal to or smaller than the linear expansion coefficient of the movable sleeve member 7, in such a case or for some reason, the outer peripheral surface of the movable sleeve member 7 has a rear member 1a. When it comes into contact with the inner peripheral surface of No. 3, the flow rate of the hydraulic oil decreases (however, the flow does not stop because the throttle gap t does not close). A measure is taken to stop the motor 6 by detecting this decrease in the amount of oil with the flow rate sensor 30 and issuing an alarm. Temperature sensor 20
In addition to detecting the temperature of the rear member 1a and issuing an alarm when the temperature is out of the set temperature range, whether or not to issue the alarm can be determined from the detection signal of the flow rate sensor 30 at that time.

Further, when the temperature of the hydraulic oil decreases and becomes supercooled, the outer ring side of the rolling bearing 4 is cooled and the preload rises or fluctuates in the conventional structure. Since the viscosity μ increases, the working oil flow rate Q is throttled by the following equation (2) in the throttle gap t (δ2), so that supercooling is automatically prevented. Q = δ2 ³ · W3 · (PA −PB) / (12 μ · L) (2) where L is the length of the aperture gap t

When the inner movable sleeve member 7 expands due to the heat generation of the rolling bearing 4 and the bearing gap δ1 becomes smaller, the flow rate of hydraulic oil decreases and its temperature rises. This heat is transmitted to the rear member 1a having a large linear expansion coefficient, and the inner diameter increases, so that the bearing clearance δ1 increases. If both parts touch,
The heat will be transferred more easily, and the gap will increase.

In the above, since the front-rear width W3 of the throttle gap t is narrowed and the throttle gap t (δ2) is increased by that amount, and a predetermined amount of hydraulic oil flows, the radial direction of the movable sleeve member is reduced. A change in the diaphragm function of the diaphragm gap t due to movement or expansion can be suppressed to a small level.

For preload, a constant pressure preload using a spring, hydraulic pressure, pneumatic pressure and a preload switching device using a hydraulic cylinder or the like is generally used to obtain a fixed position preload. In addition to the spring 9, it is possible to provide a hydraulic cylinder that enables a fixed position preload, but it is also possible to provide only a fixed position preload or, in some cases, to apply to a spindle device that has no preload. Further, the preload structure is not limited to the one shown in the drawing, and is optional. Further, although the spindle device shown in the drawing is a motor built-in type in which the motor 6 is provided in the housing 1, it can be applied to a spindle device not having a built-in motor. There are two or more hydraulic chambers Oa, or the throttle gap t is directly connected to the oil discharge hole 1d so that the oil discharge chamber O
It is also possible to eliminate b.

[0033]

As described above, according to the first aspect of the invention, the downward load on the movable sleeve member applied to the housing is reduced to reduce the axial frictional resistance between the housing and the movable sleeve member. It is also possible to cool the housing and the movable sleeve member with hydraulic oil to suppress the temperature rise between them, and to properly maintain the gap between them. Therefore, it is possible to obtain a spindle device for a machine tool which can absorb thermal expansion and prevent its adverse effect, and which has a large supporting rigidity and load capacity supported by a wide cylindrical surface and has a simple structure and is inexpensive. it can.

In the spindle device for a machine tool according to claim 1, when the movable sleeve member is provided with the preload means, the bearing preload is stabilized, and the main shaft is smoothly rotated in the entire range from the low speed to the high speed. It becomes possible to pressurize. Further, in the spindle device for a machine tool according to claim 1 or 2, when the linear expansion coefficient of the housing is made larger than the linear expansion coefficient of the movable sleeve member, even if the temperature of the movable sleeve member rises due to heat generation of the rolling bearing, Since the reduction of the gap between the housing and the movable sleeve member is alleviated, the above-mentioned gap can be reduced in advance to enhance the support rigidity.

In the spindle device for a machine tool according to any one of claims 1 to 3, when a bearing gap smaller than the hydraulic chamber and the front and rear sides of the throttle gap are formed, the movable sleeve member is reduced in diameter. Even if the movable sleeve member moves in the direction and comes into contact with the housing, the diaphragm gap is not closed. Therefore, buoyancy is always applied to the movable sleeve member regardless of radial movement or expansion of the movable sleeve member, and Etc. can be cooled. Further, in the spindle device of the machine tool described above, when the front-rear width of the throttle gap is made smaller than the front-rear width of the hydraulic chamber, the change in the throttle function of the throttle gap due to the radial movement or expansion of the movable sleeve member is suppressed. Therefore, a predetermined buoyancy can be applied to the movable sleeve member accurately and stably.

In the spindle device of a machine tool according to a third aspect of the present invention, bearing gaps smaller than those are formed in front and rear sides of the hydraulic chamber and the throttle gap, respectively, and the housing and the movable sleeve member have the same minimum operating temperature range. When the bearing gap is set so as not to become zero when the temperature reaches the temperature, the bearing gap is always secured, and contact between the housing and the movable sleeve member due to normal thermal expansion is prevented.

According to the invention described in claim 7, it is possible to detect an abnormality at an early stage by the detection signal of the monitoring sensor and prevent a larger accident.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a spindle device of a machine tool according to the present invention.

FIG. 2 is a horizontal sectional view of a spindle device of the machine tool of FIG.

FIG. 3 is a diagram showing a relationship among a hydraulic chamber, a throttle gap, and an oil discharge chamber.

FIG. 4 is a diagram showing a relationship between a hydraulic chamber and a throttle clearance.

FIG. 5 is a cross-sectional view of a conventional spindle device of a machine tool.

FIG. 6 is a cross-sectional view of another conventional spindle device of a machine tool.

7 is a sectional view of a (VII-VII) portion of the spindle device of the machine tool of FIG.

[Explanation of symbols]

1 Housing 1a Rear Member (Rear Housing) 1c Oil Supply Hole 1d Oil Discharge Hole 2 Spindle 4 Rolling Bearing 6 Motor 7 Movable Sleeve Member 9 Preload Spring (Preload Means) 20 Temperature Sensor 30 Flow Sensor Oa Hydraulic Chamber Ob Oil Discharge Chamber t Throttle Gap c Bearing gap

Claims (7)

(57) [Claims] 1. A spindle device of a machine tool, wherein a main shaft is rotatably supported by a rolling bearing in a housing, wherein a movable sleeve member is fitted to an outer ring of the rolling bearing between the housing and the rolling bearing. Approximately the lower half of the inner peripheral surface of the housing, which is inserted so as to be movable in the axial direction of the main shaft and is horizontally arranged,
A hydraulic chamber for applying a buoyant force to the movable sleeve member by hydraulic oil is formed in communication with the oil supply hole between the lower surface of the outer peripheral surface of the movable sleeve member and a housing above the hydraulic chamber. A spindle device for machine tools, characterized in that a throttle gap for resisting the outflow of hydraulic oil is formed between the inner peripheral surface of and the outer peripheral surface of the movable sleeve member so as to communicate with the oil discharge hole. 2. A spindle device for a machine tool according to claim 1, wherein the movable sleeve member is provided with a preload means. 3. The spindle device for a machine tool according to claim 1, wherein the linear expansion coefficient of the housing is larger than the linear expansion coefficient of the movable sleeve member. 4. A spindle device for a machine tool according to claim 1, wherein bearing gaps smaller than the hydraulic chamber and the front and rear sides of the throttle gap are formed respectively. . 5. The spindle device for a machine tool according to claim 4, wherein the front-back width of the throttle gap is smaller than the front-back width of the hydraulic chamber. 6. The spindle device for machine tools according to claim 3, wherein bearing gaps smaller than the hydraulic chamber and the front and rear sides of the throttle gap are respectively formed, and the housing and the movable sleeve member have a minimum operating temperature range. The spindle device of a machine tool, wherein the bearing clearance is set so as not to become zero when the same temperature is reached. 7. A spindle sensor for a machine tool according to claim 1, wherein a flow rate sensor for detecting a flow rate of hydraulic fluid supplied to a hydraulic chamber, a temperature sensor for detecting a temperature of a housing, and the like. The monitoring method of the spindle device, wherein the monitoring device is provided, and the spindle sensor is monitored by detecting the hydraulic oil flow rate and the housing temperature by the monitoring sensor.