JPH02209619A - Bearing device for rotating shaft - Google Patents

Abstract

PURPOSE:To operate a rotating shaft at an optimum oscillating condition, and thereby contrive to increase the number of revolutions and to lengthen the life of it by letting a part of piezo-electric elements arranged between a bearing hold section and a support frame act as a detector, and letting the other ones of them act as a driver, and thereby applying voltage determined by the magnitude of oscillation to said driving elements. CONSTITUTION:Detecting piezo-electric elements 6a and 6b and driving piezo-electric elements 7a and 7b are provided between a bearing hold section 4 holding a bearing 4 and a support frame 3. The direction of rotating oscillation is judged by a judging section 10 based on signals from the detecting piezo-electric elements 6a and 6b, and operation is processed by a control section 11 together with a revolution detector 8 so as to be inputted into a voltage generating sections 12a and 12b together with signals from the detecting piezo-electric elements 6a and 6b while the out put is being inputted into the driving piezo-electric elements 7a and 7b so that the bearing hold section 4 is thereby driven. This permits, the damping force of the bearing to be changed in response to the number of revolutions to operate a rotating shaft at an optimum oscillating condition, thereby making it possible to increase the number of revolutions and also to lengthen the life of it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a bearing device for a rotating shaft in a rotating device that rotates at high speed.

[Background of the invention]

When a rotating body rotates at high speed, rotational energy and centrifugal force increase, so bearings that can rotate at higher speeds are required. However, when a rotating shaft rotates at high speed, the vibration increases when the rotation period of the rotating shaft and the natural frequency of the shaft system become close.
This may cause noise or damage the bearing device, so countermeasures are required. Traditionally, as a countermeasure,
A method of forming a gap between the rotating shaft and the support body, allowing oil to enter the gap to form an oil film, and using the damping force of the oil film to suppress vibrations, and bearings that support the rotating shaft and supports that support the bearings. A method has been used in which a viscoelastic material such as rubber is placed between the bodies and the vibration of the shaft is controlled using the viscosity of the material. In the latter method, the characteristics are determined by the properties of the rubber, so the characteristics cannot be changed depending on the operating conditions such as the rotation speed. -The characteristics of the six rotating shafts are that at rotational speeds close to the natural frequency of the rotating shaft system, the damping force of the bearing device is increased to suppress resonance, and when the rotational speed becomes even higher, the rotating shaft Since the bearing rotates around its center of gravity, it is necessary to reduce the damping force and reduce the load on the bearing in order to eliminate the cause of early failure of the bearing. In order to achieve the optimum vibration state when the rotational speed is changed in this way, the damping characteristics of the bearing device should be set to any number 1 or 2 depending on the rotational speed.
- Adjustment is necessary, which is difficult with the conventional method [Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to enable the rotational shaft to operate at higher speeds.

[Summary of the Invention] Generally, the equation of motion expressed from one direction of the bearing regarding the vibration of a rotating body is expressed as shown in the following equation.

m (d”x/dt2)+c (dx/dt)+k
x=Om(al"s i nwt where m is the mass of the rotating body, C is the damping coefficient of the bearing, k is the composite value of the spring constant of the bearing and shaft, and X is the vibration displacement (dx/dt
) is the vibration velocity, (d'x/dt2) is the vibration acceleration, e is the distance from the center of the rotation axis to the center of gravity, ω is the rotational angular velocity, t
is time.

Here, if X is expressed as asinOt, (dx/dt) is a
Ocoset, = aOgin (ot 10yc / 2
), and the damping force is a force whose phase is 90 degrees different from the displacement signal. In the case of rotational vibration, the displacement signal is detected at a position 90 degrees away from the detection position.

When the bearing is rocked with a force related to the displacement signal, it has been damped.

The present invention focuses on the fact that when a load is applied to a piezoelectric element, it generates a voltage and becomes a vibration sensor, and when a voltage is applied to a piezoelectric element, its dimensions change and can be used as a driving source. The above-mentioned piezoelectric element is used in the bearing holding part that holds the bearing, and the voltage controlled according to the signal of the piezoelectric element serving as a sensor and the rotation speed detected from the rotating shaft is driven at a position shifted by approximately 90 degrees. This device is designed to control the vibration of the rotating shaft by applying a voltage to the piezoelectric element that serves as the source.

[Embodiments of the invention]

An embodiment of the present invention will be described.

1 and 2 show embodiments of the present invention, where ] is a rotating shaft extending perpendicular to the plane of the paper, 2 is a bearing such as a plastic bearing, oil-impregnated bearing, or ball bearing that supports the rotating shaft, and 3 is the rotating shaft. 4 is a bearing holding part which holds the bearing 11η and connects it to the support frame; 5 is a bearing holding part which connects the bearing holding part 4 and the support frame 3 and which holds the bearing; 6a and 6b are piezoelectric elements for detecting laminated state inserted between the support frame and the bearing holder; 8 is a rotation detection device that detects the number of rotations from a notch in the rotating shaft, etc. 10 is a determination unit that determines whether the direction of rotational vibration is the same as or opposite to the rotational direction 9 based on the signals from the detection piezoelectric elements 6a and 6b; 11 is a determination unit that calculates the rotational speed from the signal from the rotational detector and determines the preset rotation; Number control relationship J, S, A control section that determines the relationship between the magnitude of vibration and the control voltage, 12a and 12b are voltage generation sections that generate voltage based on the signal from the detection piezoelectric element and the signal from the control section, 7a and 7b. is a driving piezoelectric element that is displaced by the output voltage from the voltage generating section and moves the bearing holding section to drive the bearing. The bearing holder in which the detection piezoelectric element is involved and the bearing holder in which the drive piezoelectric element driven by the detected signal is involved are arranged at positions shifted by about 90 degrees with respect to the center of rotation.

In operation, when the bearing vibrates, the detection piezoelectric element generates a voltage proportional to the vibration. Depending on vibration factors, the rotating body may vibrate in the same direction as the rotating shaft (wobble) or in the opposite direction, and the 9 discrimination section determines the direction of vibration and rotation based on the signals from the two detection piezoelectric elements. The directional relationship is determined, and the forward/reverse direction of the instant voltage is controlled based on the positional relationship of the detection and drive piezoelectric elements. The control section detects the rotation speed using the signal from the rotation detector, and controls the voltage generation section 12a to increase the damping force when the rotation speed is close to the natural frequency of the shaft system.
The output of the voltage generator 12b is increased, and the rotation period component is controlled to be reduced in the output of the voltage generator so that the rotation axis can be rotated about the center of gravity in a high-speed rotation region. The drive piezoelectric element is displaced by a voltage controlled by the number of revolutions and the vibration of the rotating shaft, and drives the bearing holder to optimize the vibration of the rotating shaft. Note that a signal from a detection piezoelectric element can also be used to detect the rotation speed.

Other embodiments of the invention are shown in FIGS. 3 and 4.

3 is a front view, and FIG. 4 is a sectional view taken along the line IV-rV in FIG. 3. The difference from the embodiment is that the bearing holding part and the piezoelectric element are arranged parallel to the rotating shaft, and the control relationship is the same as that in FIG. 1, although not shown.

In this modification, the size of the support frame can be reduced, and the rotating device can be made smaller and lighter.

〔Effect of the invention〕

According to the present invention, not only the vibration state of the rotating shaft but also the damping force of the bearing can be changed depending on the rotation speed, so that the optimal vibration state of the rotating shaft can be achieved. can be done.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a rotating shaft bearing device according to the present invention. 4 is a bearing holding part, 6a and 6b are detection piezoelectric elements, 7a and 7b are driving piezoelectric elements, and 8 is a rotation detector.

Claims (1)

[Scope of Claims] 1. A device having a rotating shaft, a bearing that supports the rotating shaft, and a bearing holding part that holds the bearing and connects it to a supporting piece, in which a piezoelectric element is disposed between the bearing holding part and the supporting piece. A large number of sets of a bearing holding part and a piezoelectric element are arranged, some of the piezoelectric elements are used as detection piezoelectric elements, and the other parts are used as drive piezoelectric elements, and the vibration of the bearing is detected by the detection piezoelectric element. A bearing device for a rotating shaft, characterized in that a voltage controlled according to the magnitude of vibration is applied to a driving piezoelectric element, and the vibration of the bearing is controlled using the displacement of the driving piezoelectric element. 2. Claim 1, characterized in that the rotational speed is detected from the rotating shaft, and a voltage controlled by the relationship between the magnitude of vibration detected by the detection piezoelectric element and the rotational speed is applied to the driving piezoelectric element. Bearing device for the rotating shaft described. 3. The rotation according to claim 1, wherein the rotational direction of the vibration is determined from the signals of two or more detection piezoelectric elements, and a voltage controlled by the rotational direction of the vibration is applied to the driving piezoelectric element. Shaft bearing device.