JPH0625698Y2 - Tilting pad bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a tilting pad bearing, which is a type of dynamic pressure gas bearing.

[Prior Art] In a tilting pad bearing, a tilting pad having a partial arc shape is arranged between a rotary shaft and a bearing housing, and between the inner peripheral surface of the pad and the outer peripheral surface of the rotary shaft. By forming a gas film of a dynamic pressure gas, the rotating shaft is floatingly supported on the pad. As described above, the greatest feature of this bearing is that the rotating shaft can be supported by the pad in a non-contact manner, and since the structure is relatively compact, it is extremely useful as a bearing for supporting a high-speed rotating machine. .

By the way, in order to effectively form the above-mentioned gas film in the gap between the tilting pad and the rotary shaft, the outer peripheral surface of the rotary shaft and the inner peripheral surface of the pad have a gap of several micrometers to several tens of micrometers. The dimensions must be closely confronted.
At the same time, in order to change the setting of the preload (contact pressure to the shaft of the pad) according to the load capacity and to suppress the abnormal pressure fluctuation of the gas film,
It is essential that it be changeable within the above dimensions. For this reason, conventionally, the tilting pad is supported at a single point on its outer peripheral portion by a pivot or the like, and a portion deviated from the support point of the pivot is elastically supported by the bearing housing via a spring or the like. With such a configuration, even if the pressure of the gas film changes unevenly for some reason, the pad rotates about the pivot as a fulcrum and balances with the gas pressure counteracted by the spring action. However, since the angle or the position with respect to the rotating shaft is changed, the gas film can always be effectively formed, and the rotating shaft can be stably supported by the bearing housing in a floating manner. .

[Problems to be Solved by the Invention] By the way, an unbalanced external force or the like may temporarily act on the rotating shaft of the rotating machine at the time of starting or under load, and the shaft center may be eccentric. In this case, if the eccentricity of the rotary shaft is not sudden and the rotary shaft is relatively small, the pad can follow the displacement of the shaft by the deformation of the spring to change the posture. However, if the rotating shaft is large or something happens during high-speed rotation, the tilting pad has inertial weight, so if the pad is simply driven passively, There is a limit to the ability to follow displacement. Therefore, if the rotary shaft is suddenly decentered beyond such a limit, the pad can no longer follow it, and its inner peripheral surface comes into direct solid contact with the outer peripheral surface of the rotary shaft, resulting in damage to the pad. It is unavoidable that the bearing becomes unusable early.

The present invention aims to surely eliminate such a problem with a simple configuration.

[Means for Solving the Problems] In order to achieve the above object, the present invention supports the center of a tilting pad by a pivot, and at the same time, a portion that is displaced in one direction from the support point of the tilting pad is provided. A piezoelectric element is interposed between the bearing housing and the tilting pad so that the angle or position of the tilting pad can be changed.

[Operation] As is well known, the piezoelectric element can oscillate at several kilohertz, and has a very short response time until it expands and contracts when a drive voltage is applied. Therefore, if the tilting pad is supported by the bearing housing via this piezoelectric element, when a suitable drive voltage is applied to the piezoelectric element with respect to the sudden eccentricity of the rotating shaft, the piezoelectric element will fall within its response time. The pad will be forced to change its position by expanding and contracting. As a result, the followability of the pad is improved, and even if the rotary shaft is suddenly eccentric, the inner peripheral surface of the pad makes solid contact with the outer peripheral surface of the rotary shaft, or the pressure of the gas film fluctuates greatly. You don't have to make a mistake.

Particularly, in this device, the center of the tilting pad is supported by a pivot, and a portion deviated from the center in one direction is driven by a piezoelectric element. Therefore, the tilting pad as a whole can be tilted by a desired angle with respect to the rotation axis without providing piezoelectric elements at both ends of the tilting pad. Moreover, because of this, the gap formed between the tilting pad and the rotation shaft becomes gradually smaller in the rotation direction, and thus such a simplified configuration is suitable for forming a dynamic pressure gas film. It becomes a thing.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

The tilting pad bearing of this embodiment is configured as a journal bearing, and three tilting pads 3 are arranged along the inner circumference of a bearing housing 2 surrounding the rotary shaft 1. These pads 3 correspond to the rotary shaft 1
It has a partially arcuate shape substantially corresponding to the shape of the outer peripheral surface of, and these are closely enclosed along the rotating shaft 1. Then, the pivot 4 having the outer peripheral portion substantially central portion of each pad 3 protruding from the inner peripheral surface of the bearing housing 2 is provided.
It is rotatably supported at a point.

In such a case, the tilting pad 3
A piezoelectric element 5 is provided between the bearing housing 2 and the bearing housing 2 so that the angle or position of the tilting pad 3 can be changed. That is, the piezoelectric elements 5 are fixed to the inner periphery of the bearing housing 2 at three locations in the circumferential direction at equal angular intervals, and the tips of the piezoelectric elements 5 are the outer peripheral portion of the pad 3 and the supporting points of the pivot 4. It is fixed to the end that is offset from. These piezoelectric elements 5 are expandable / contractible in the radial direction of the rotary shaft 1, and the pads 3 can be forced to follow during the expansion / contraction operation.
At this time, since the central portion of the pad 3 is point-supported by the pivot 4 as described above, when the piezoelectric element 5 expands and contracts, the pad 3 rotates while using the support point of the pivot 4 as a fulcrum. The angle and position will be changed. The position where the piezoelectric element 5 is fixed to the pad 3 is always located closer to the outer peripheral surface of the rotary shaft 1 than that of the pivot 4. In other words, the gap between the pad 3 and the rotary shaft 1 is gradually narrowed in the rotation direction of the rotary shaft 1, which is because the rotation of the rotary shaft 1 entrains the surrounding gas. This is because the original effect of the dynamic pressure gas bearing is to generate a high pressure dynamic pressure gas film in the narrowed portion.

On the other hand, each piezoelectric element 5 has an electrode (not shown) for applying a driving voltage, and each electrode has a piezoelectric element control power supply circuit (hereinafter, simply referred to as a power supply circuit) 6
It is connected to the. The power supply circuit 6 is capable of independently applying a drive voltage of a required magnitude to each of the piezoelectric elements 5 at any time. The power supply circuit 6 is operated by receiving a signal from the sensor 7. Each sensor 7 is paired with one of the piezoelectric elements 5 and is embedded in the inner circumference of the bearing housing 2 so as to be positioned in the advancing direction of the rotary shaft 1 with respect to the piezoelectric element 5. ing. When the axis of the rotating shaft 1 is eccentric, the amount of eccentricity is detected in a non-contact state with respect to the rotating shaft 1, and a signal corresponding to this amount of eccentricity is generated. Is input to the power supply circuit 6 via. Then, based on this signal, the power supply circuit 6 forms a pair with the sensor 7 and the piezoelectric elements 5 respectively.
A drive voltage is applied to.

The piezoelectric element 5 used here is generally used and can oscillate at several kilohertz. Therefore, the response time of the piezoelectric element 5 from application of voltage to expansion / contraction displacement is extremely short. For example, the rotary shaft 1 has tens of thousands to hundreds of thousands r
Considering the case of high speed rotation of pm, the number of revolutions per second of the rotating shaft 1 is about several hundreds to several thousands, but the rotating shaft 1 is eccentric and the driving voltage is applied to the piezoelectric element 5 almost at the same time. Even if applied, it is possible to end the response by expanding and contracting while the rotary shaft 1 makes one revolution.

With the above-described structure, the axis of the rotating shaft 1 is suddenly changed to one while the rotating shaft 1 is rotating while forming a gas film of the required dynamic pressure gas between the rotating shaft 1 and the tilting pad 3. When the pad 3 is eccentric to the eccentric direction, the pad 3 facing the eccentric direction unnecessarily narrows the gap with the rotary shaft 1. Then, the sensor 7 closest to the pad 3 detects this gap abnormality,
A signal is input to the power supply circuit 6 via the sensor amplifier 8.
In the power supply circuit 6, a drive voltage is applied to the piezoelectric element 5 forming a pair with the sensor 7 that has generated a signal, and the piezoelectric element 5 is degenerated. As a result, the pad 3 is forcibly repositioned with the pivot 4 serving as a fulcrum in the direction in which the gap between the pad 3 and the rotating shaft 1 is widened, and the inner peripheral surface of the pad 3 is kept at a constant distance from the approaching standard shaft 1. It is possible to avoid the solid contact with the outer peripheral surface of the rotating shaft 1 and effectively prevent the pressure of the gas film from unduly increasing.

At this time, in the pad 3 located on the side opposite to the eccentric direction of the rotating shaft 1, the rotating shaft 1 is rapidly moved away, and the clearance dimension is unduly widened. Then, the sensor 7 closest to this position detects a gap abnormality and inputs a signal to the power supply circuit 6 via the sensor amplifier 8. In the power supply circuit 6, a drive voltage is applied to the piezoelectric element 5 that operates in pair with the sensor 7 that has generated a signal, and the piezoelectric element 5 is expanded. As a result, the pad 3 is forcibly repositioned with the pivot 4 serving as a fulcrum in a direction in which the gap between the pad 3 and the rotating shaft 1 is narrowed, and a constant distance is maintained between the pad 3 and the rotating shaft 1 which separates from each other, thereby maintaining the pressure of the gas film. Can be effectively prevented from decreasing.

The driving of the pad 3 by these piezoelectric elements 5 is extremely quick as described above, and the rotary shaft 1 moves from tens of thousands to hundreds of thousands of r.
It can be effectively performed even when rotating at high speed in pm. Therefore, in the case of such a tilting pad bearing, when the conventional elastic support is used, there is a problem that the pad is solidly contacted with the eccentric rotating shaft due to the follow-up delay of the elastic support and is damaged. , Can be surely prevented.

Particularly, in this device, the center of the tilting pad 3 is supported by the pivot 4, and the end portion deviated from the center in one direction is driven by the piezoelectric element 5. Therefore, the number of attached piezoelectric elements 5 is 1 for each tilting pad 3.
Even if it is only one, the tilting pad 3 as a whole can be tilted by a desired angle with respect to the rotary shaft 1, and the number of parts can be reduced and the structure can be simplified. In addition, the gap formed between the tilting pad 3 and the rotating shaft 1 is gradually reduced in the rotating direction, and thus such a configuration reduces the number of parts and simplifies the structure. Not only is it effective, but on the contrary, it is suitable for forming a dynamic pressure gas film.

An arithmetic circuit for calculating the optimum displacement amount by displacement analysis may be provided between the sensor amplifier 8 and the power supply circuit 6. Further, in the above embodiment, the three tilting pads 3 and the three piezoelectric elements 5 are used, but the number of these elements is not particularly limited.
Furthermore, although the present invention is used as a journal bearing here, the same effect as in the above embodiment can be obtained by using it as a thrust bearing.

[Advantage of the Invention] The present invention has the structure in which the tilting pad is supported on the piezoelectric element as described above, and the angle or position of the pad is forcibly changed by utilizing the responsiveness of the piezoelectric element. Since it is possible to improve the followability of the pad and reliably avoid the problem that the pad comes into solid contact with the rotating shaft even when the rotating shaft is eccentric at the time of start or overload,
It is possible to provide a tilting pad bearing that can be suitably applied to a large-sized rotating machine at a higher speed and that can be used with peace of mind even under a condition in which an external force such as vibration is large.

In particular, in the present invention, the center of the tilting pad is supported by the pivot, and the portion deviated in one direction from the center is driven by the piezoelectric element, so the number of piezoelectric elements is reduced and the structure is simplified. , More appropriate operation can be secured.

[Brief description of drawings]

The drawing is a schematic sectional view showing an embodiment of the present invention. 1 ... Rotary shaft, 2 ... Bearing housing. 3 ... Tilting pad 4 ... Pivot 5 ... Piezoelectric element 6 ... Piezoelectric element control power supply circuit 7 ... Sensor 8 ... Sensor amplifier

Claims (1)

[Scope of utility model registration request] 1. A rotating shaft is supported by a bearing housing via a tilting pad, the center of the tilting pad is supported by a pivot, and the tilting pad is supported in one direction from a supporting point of the tilting pad. A tilting pad bearing, wherein a piezoelectric element is provided between the offset portion and the bearing housing so as to change the angle or position of the tilting pad.