JP3071489B2 - Non-contact bearing overload detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type bearing device for detecting an overload state on a shaft.

[0002]

2. Description of the Related Art Generally, the load capacity of a non-contact type bearing such as a fluid bearing or a magnetic bearing is smaller than that of a rolling bearing. For this reason, when a large load is applied to the shaft due to overload or malfunction, the shaft comes into contact with the non-contact bearing, and seizure occurs on those contact surfaces.

[0003] As a countermeasure, a rolling bearing is incorporated between the load point of the shaft and the non-contact bearing, and the gap between the inner diameter of the inner ring of the rolling bearing and the outer diameter of the shaft is set smaller than that of the non-contact bearing. A composite bearing device has been proposed in which, when a large load is applied to a shaft, the shaft is supported by a rolling bearing before the shaft comes into contact with the non-contact bearing (issued on April 10, 1988, Japan Corporation). Chapter 4 “High-speed and high-rigidity with composite bearings” in “The cutting-edge technology of machine tools”, edited by the Japan Society of Mechanical Engineers and published by the Industrial Research Institute.

However, in the case of the above bearing device, when the rotation speed of the shaft is higher than the allowable rotation speed of the rolling bearing,
Rolling bearings seize and may be damaged. Also,
Even if the burn-in state does not occur, since the shaft is changed to the rolling motion support from the time when the shaft is supported by the rolling bearing, smooth rotation characteristics of the non-contact bearing cannot be obtained, which adversely affects the machining accuracy.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bearing device having a non-contact bearing and a rolling bearing, which detects an overload state on a shaft and takes necessary measures according to the overload state. is there.

[0006]

According to the present invention, there is provided a bearing device having a non-contact bearing and a rolling bearing, wherein an annular rotating body is attached to a rotating side portion of the rolling bearing in an inserted state with respect to the shaft. The clearance between the inner peripheral surface of any one of the rotating part and the rotating body of the rolling bearing and the outer peripheral surface of the shaft is set smaller than the clearance of the non-contact bearing, and the frictional resistance of air in the clearance between the shaft and the rolling bearing is set. Is detected by a rotation sensor, and the output of the rotation sensor can be detected by an F / V converter and a signal level detector.

If the shaft is overloaded and eccentric during rotation of the shaft, the frictional resistance increases in proportion to the amount of eccentricity.
The rotation speed of the rotating body increases. This rotation speed is detected by the rotation sensor, and the signal level of the F / V converter gradually increases. Thus, an overload state on the shaft can be detected. Therefore, in accordance with the overload state, a state where appropriate measures such as control of the support force of the non-contact bearing and control of the rotation speed of the shaft can be performed.

[0008]

1 and 2 show a non-contact bearing overload detecting apparatus 1 according to the present invention. The overload state detecting device 1 is configured on the premise of a composite type bearing device 2.

The bearing device 2 includes, for example, a main shaft 3 of a machine tool.
For example, a fluid type non-contact bearing 5 is provided inside the housing 4 in order to support the non-contact type. The non-contact bearing 5 is inserted into the shaft 3, and forms a gap 6 with an interval δ1 between the outer peripheral surface of the shaft 3 and the inner peripheral surface of the non-contact bearing 5. The shaft 3 can be held in a non-contact state by supplying a pressure fluid 8 from a fluid port 7 formed in the housing 4 toward the housing 3.

A cover 9 is attached to the opening side of the housing 4 so that a rolling bearing 10 for preventing seizure is attached to the non-rotational side support portion of the shaft 3, that is, the housing 4. On the other hand, it is installed in a non-contact insertion state. Note that this non-contact bearing 5
Are formed with pockets 18 and are connected to the discharge port 19.

The overload detecting device 1 of the present invention is incorporated in the bearing device 2 and includes a rotating body 11, a rotation sensor 12,
/ V converter 13 and comparator 14.

The rotating body 11 is made of copper or gunmetal, and is fixed to the inner ring 10 a on the rotating side of the rolling bearing 10 by press fitting or the like at a cylindrical portion. Gap 1 with an interval δ2 smaller than the interval δ1
6 are inserted into the shaft 3 in a state where they are formed, and the detection object 15 such as a reflection surface or a magnetic material having different irregularities or reflectivity according to the detection characteristics of the rotation sensor 12 at equal intervals along the circumference. have. A groove or the like having an equal pitch is formed on a portion of the outer peripheral surface of the shaft 3 facing the inner periphery of the rotating body 11 as necessary.

The rotation sensor 12 includes a cover 9
And is configured as a capacitive proximity sensor, an optical proximity sensor, or a magnetic proximity sensor corresponding to the unevenness, the reflection surface, or the magnetic material of the detection target 15, and an F / V converter. 13 is connected to one input terminal of a comparator 14. The comparator 14 is connected to the reference setting device 17 at the other input terminal.

When the shaft 3 rotates at a high speed, a pressure fluid 8 is supplied to a fluid port 7 of the non-contact bearing 5 and injected into the gap 6. Thus, the non-contact bearing 5 supports the shaft 3 in a non-contact state. The pressure fluid 8 flowing out of the gap 6 enters the inside of the pocket 18 and is sent from the discharge port 19 to the circulation system.

When the shaft 3 rotates, the rolling bearing 10 is moved to the inner race 10 by the frictional resistance between the shaft 3 and the air in the gap.
a, the ball 10b and the outer ring 10c rotate at a certain rotational speed in which the rolling friction resistance and the air friction resistance force are balanced.

Here, if the shaft 3 is overloaded, the shaft 3 is eccentric, and the frictional resistance at that portion increases in inverse proportion to the decrease in the gap 16, as shown in FIG.
The frictional resistance of the entire outer peripheral portion of the rolling bearing 10 increases, and as a result, the inner race 10c of the rolling bearing 10 and the rotating
Gradually increases. Finally, when the shaft 3 comes into contact with the inner peripheral surface of the rotating body 11, the inner ring 10 a of the rolling bearing 10 rotates at the same rotation speed as the rotation of the shaft 3 at this point.

During this time, the rotation sensor 12 detects the object 15 to be detected, generates a rectangular output signal at the time of the detection, and sends it to the F / V converter 13 as shown in FIG. . Of course, the frequency of the output signal from the rotation sensor 12 increases in proportion to the rotation speed of the rotating body 11.

Then, the F / V converter 13 converts the frequency of the output signal from the rotation sensor 12 into a voltage level,
The signal is sent to one input terminal of the comparator 14. The comparator 14
The other input terminal compares the output voltage with the reference voltage set by the reference setting device 17 and, when the output signal level ≧ the reference voltage level, generates an output signal of, for example, “H” level.

Therefore, depending on the presence or absence of this output signal, an overload state on the shaft 3 can be confirmed from the outside, and the output signal controls the pressure of the pressure fluid 8 or the number of revolutions of the shaft 3. In addition, seizure of the non-contact bearing 5 and the rolling bearing 10 can be prevented beforehand.

[0020]

Other Embodiments In the above embodiment, a gap 16 is formed between the inner peripheral surface of the cylindrical shaft portion of the rotating body 11 and the outer peripheral surface of the shaft 3, but the rotating body 11 is The gap 16 is formed by the inner peripheral surface of the shaft 3 and the inner peripheral surface of the inner race 10a if it can be fixed to the side surface of the shaft by means such as bonding.

Further, in the above embodiment, since the rolling bearing 10 is arranged on the outer portion of the shaft 3, the rotating body 11
Is fixed to the inner ring 10a, but the shaft 3 is cylindrical, and the rolling bearing 10 is inserted into the cylindrical shaft 3, and the outer ring 10c faces the inner peripheral surface of the shaft 3. In the case of the supporting form described above, the portion of the outer ring 10c is on the rotating side co-rotating with the shaft 3, so that the rotating body 11 is attached to the portion of the outer ring 10c.

[0022]

According to the present invention, when an overload is applied to a shaft, the rotating body is rotated by an effect of dynamic pressure from the shaft before the circumferential surface of the shaft comes into contact with the circumferential surface of a non-contact type bearing. The number of rotations, which can be detected by the F / V converter and the comparator, makes it possible to detect an overload state on the shaft. Therefore, it is possible to prevent the rolling bearing from burning due to the influence of the high-speed rotation of the shaft.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a non-contact bearing overload detection device of the present invention together with a bearing device.

FIG. 2 is a front view of a rotating body.

FIG. 3 is a graph showing an output signal from a rotation sensor as time on a horizontal axis and a voltage level on a vertical axis.

FIG. 4 is a graph showing a change in frictional resistance with respect to an eccentric amount of a shaft.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Non-contact bearing overload state detecting device 2 Bearing device 3 Shaft 4 Housing 5 Non-contact bearing 6 Gap 7 Fluid port 8 Pressure fluid 9 Cover 10 Rolling bearing 11 Rotating body 12 Rotary sensor 13 F / V converter 14 Comparator 15 Detected object 16 Gap 17 Reference setter

Claims (2)

(57) [Claims] 1. A bearing device in which a shaft is supported by a non-contact bearing, and a rolling bearing for preventing seizure is incorporated in a non-rotation side supporting portion of the shaft in a non-contact state with respect to the shaft. The ring-shaped rotating body is attached to the shaft in a state of being inserted into the shaft, and the gap formed between one of the rotating surface of the rolling bearing and the circumferential surface of the rotating body and the circumferential surface of the shaft is defined as the circumferential surface of the shaft. It is set smaller than the gap formed by the peripheral surface of the non-contact bearing, and a rotation sensor at a fixed position is opposed to the rotating body, and this rotation sensor is connected to the F / V converter and the signal level detector sequentially. An overload state detection device for a non-contact bearing, comprising: 2. The overload state of the non-contact bearing according to claim 1, wherein the rotation sensor is constituted by a proximity sensor, and a detection object corresponding to a detection characteristic of the proximity sensor is incorporated around the rotation body. Detection device.