JPH028716A - Vibration meter - Google Patents

Abstract

PURPOSE:To enable accurate measurement of vibration over-coming stable condition of a surface to be measured by providing a detection rod elastically supportable being projected slightly from an attraction surface of a permanent magnet for fixing to mount a vibration sensor thereon. CONSTITUTION:An detection rod 21 elastically supportable is provided being projected slightly from an attraction surface of a permanent magnet 18 for fixing a vibration meter body 17 on a mechanical construction to mount a vibration sensor 1 at the tip thereof. The upper end of the detection rod 21 is supported elastically on the permanent magnet 18 with a plate spring 22 as elastic body through a mounting seat 23. With such an arrangement, a surface to be measured has a ruggedness and even when the attraction of the permanent magnet 18 is unstable, the vibration of the surface to be measured is transmitted to the vibration sensor 1 faithfully through the detection rod 21 irrelevant to the movement of the vibration meter body 17.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a vibration meter that detects vibrations of mechanical structures as electrical signals and measures vibration levels.

[Conventional technology]

Vibrations that occur during operation of mechanical structures such as electric motors are caused not only by unbalance caused by processing errors and assembly errors in the rotating body itself, but also by mechanical and electrical aging of the constituent members, such as loosening between members. It also responds accurately to gaps that occur due to dryness in the insulating layer within the motor's winding grooves. Therefore, measuring the vibrations of mechanical structures is essential for monitoring abnormalities. Generally, the vibration level of mechanical vibration is measured by electrically detecting the speed and acceleration of vibration, and inputting the detected electrical signal to a vibration meter. On the other hand, in large plants in industrial fields such as electric power, steel, and chemicals that use a large number of rotating machines, supervisors usually make regular patrols in order to improve plant availability and effectively carry out maintenance and repairs. vibrations are measured. However, general vibration measurement has the following problems. (1) Since the vibration sensor is attached and measured each time, the vibration measurement position and the method of installing the vibration sensor are not necessarily constant, resulting in individual differences. (2) Since the vibration sensor and the vibration meter body are separated, measurement requires labor and time. (3) Most of the objects to be measured are rotating machines, and since sensor installation and vibration measurement are performed while the machine is operating, the work may be dangerous, and sometimes measurements may not be possible. (4) Specialized skills and experience are required to operate the vibration meter. For this reason, for highly important machines, there is a tendency to use a centralized monitoring method in which only the vibration meter sensor is fixed to the part of the machine to be measured, and the vibration level is centrally measured from a distance to monitor machine abnormalities. be. However, if you want to measure near the machine, you will need a separate vibration meter because the machine only has a sensor attached. Therefore, as a device suitable for such applications, a compact vibration meter was proposed that integrates all the circuits necessary for measuring and displaying vibration levels, from a vibration sensor to a vibration level display circuit, in a case together with a power supply. Already filed by the same applicant (Special Patent No. 9J1 1986-205581)
. Furthermore, in order to make it easier to read the displayed vibration level, an application has been filed in which only the display device is removable from the main body case and can be moved to multiple predetermined positions on the main body case ((Patent application Showa 60-28973
No. 6). On the other hand, if a small vibration meter that can be used close to the machine is used for centralized monitoring instead of a conventional sensor, the following problems arise. First, an application has been filed for a vibration meter with an external output function that outputs an electrical signal at a level proportional to the vibration level of the machine (Japanese Patent Application No. 61-022255). In the case of intensive monitoring, the external output of each vibration meter attached to each machine is constantly monitored, as in the case of conventional intensive monitoring in which only a vibration sensor is attached to the part to be measured. Therefore, as in the past, huge costs are required for equipment, wiring work, etc. By the way, in large plants with many machines, vibration monitoring of most machines is performed by alarm management. This alarm management determines whether the machine is being operated within the vibration level set for each machine.For this purpose, it has a vibration level judgment function, and if the vibration level exceeds the preset level. An application has been filed for a vibration meter that emits an alarm by flashing a light emitting diode (Patent Application No. 18721-1982).
No. 1). If such a vibration meter is used for centralized monitoring, there will be no need for large-scale equipment or wiring work, but it is not possible to clearly identify machines that are causing abnormal vibrations by visually observing the flashing light emitting diodes from a distance. It is quite difficult. Therefore, an application has been filed for a vibration meter that can read the vibration level near the machine and inexpensively transmits only the presence or absence of machine abnormality to a central monitoring position via near-infrared light emitted by a near-infrared light emitting diode ( Patent application 1986-265282
issue).

[Problem to be solved by the invention]

These vibration meters are economically viable when used in a company larger than a certain size, and are effective in preserving machine stage 01δ, but many companies cannot afford to invest enough to install a vibration meter on each machine. be. In other words, there is a strong desire to measure the vibration conditions of multiple machines with a single vibration meter. As a solution to this problem, it has been proposed to integrate a permanent magnet into the vibration meter body to fix the vibration meter to the machine. This method has the advantage that it is easy to attach and detach from the machine, and the vibration meter can be instantly moved to a large number of measurement positions. However, if the mechanical surface of the part where the permanent magnet is attracted is smooth, accurate measurements can be made, but if the surface is uneven or curved, such as a casting surface, it becomes difficult to ensure a stable attraction state, and errors may occur. There is a risk of making incorrect measurements. FIG. 5 explains such a situation. When the vibration meter main body 31 is fixed to the uneven measurement surface 30 with a permanent magnet 32,
The vibration meter may vibrate between the solid line and the broken line in the diagram through the gap created between the contact surfaces, causing the vibration meter to move differently from the object to be measured. This invention provides a vibration meter that can be easily attached to and removed from the machine and that can reliably transmit machine vibrations to the vibration sensor regardless of the condition of the surface to be measured, when measuring the vibrations of a large number of machines with one vibrometer. The purpose is to provide the following.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a vibration sensor that detects the vibration of a mechanical structure as an electrical signal, a display circuit that digitally displays the vibration level, and a display circuit that converts the electrical signal of the vibration sensor into a digital signal. A vibration meter that integrates a control circuit to drive a vibration meter, an operating power supply, etc., includes a permanent magnet for fixing the vibration meter body to a mechanical structure, and an elastic body with the tip of the permanent magnet slightly protruding from its attraction surface. A vibration sensor is attached to the detection rod.

[For use]

Since the vibration meter is fixed to the surface to be measured using a permanent magnet, it is easy to attach and detach the vibration meter. In addition, since the vibration sensor is attached to a detection rod that is pressed against the surface to be measured by elastic force, even if the permanent magnet's attraction becomes unstable depending on the condition of the surface to be measured, the vibration of the surface to be measured will be detected by the vibration sensor. The vibration is faithfully transmitted to the vibration sensor regardless of the movement of the main body.

【Example】

Hereinafter, the present invention will be explained in detail based on FIGS. 1 to 4. First, FIG. 2 shows an example of the circuit configuration of a vibration meter. In FIG. 2, vibrations of a mechanical structure are converted into electrical signals by a vibration sensor 1, and the vibration sensor 1 uses a piezoelectric vibration element (acceleration type). This vibration sensor 1 is attached to an elastically supported detection rod as will be described later. An electric signal proportional to the vibration acceleration detected by the expansion sensor 1 is amplified in the amplifier circuit 2. This amplified electrical signal is second-integrated by integrating circuits 3 and 4, but international standards such as VDI and ISO use vibration velocity and vibration displacement, and in order to evaluate the impact on machines and the human body. Because vibration acceleration is used, the number of integrations of the input electrical signal is determined depending on which vibration level is to be measured among the three types of vibration: acceleration, velocity, and displacement. Therefore, both the integrating circuits 3 and 4 are short-circuited, or only the integrating circuit 4 is short-circuited. Now, let the acceleration of the vibration be Ma, the velocity be λ, the displacement be X, the maximum displacement of the vibration be A, the angular velocity be ω, and the time be L. The relationship between the magnitude and phase of the signal in each circuit is as follows. In the integrating circuit 3, W = Aωzsinω is expressed as: x = 5idt = -Asinωt (in the integrating circuit 4, Since it is an AC signal, it is converted to a DC signal by a detection circuit 6 to which an amplifier circuit 5 is added.This DC signal is converted to a 256-bit digital signal by an A/D conversion circuit 7, and then sent to an LCD drive circuit 8 The LCD drive circuit 8 controls the digital display circuit 9 according to the A/D converted electric signal. At this time, sampling of data from the A/D conversion circuit 7 and display of the signal level are performed as follows. This is done at 2 second intervals.
The CD drive circuit 8 can be replaced by a microcomputer. The digital display circuit 9 includes a liquid crystal display device (L
Either a CD (CD) or a light emitting diode (LED) may be used, but in this embodiment, an LCD with the lowest power consumption is used. The power supply circuit that operates the control circuits 2 to 8 and the digital display circuit 9 described above includes a battery 10 serving as a power source, a field effect transistor (hereinafter referred to as FET) 11 constituting a switch, and an l? ET12,13,1
4. It is constructed using a timer capacitor 15, a touch switch 16 that generates an input signal, and the like. FIG. 1 shows an embodiment of the vibration meter of the present invention having the circuit configuration shown in FIG. 2, and is shown in a partially cutaway side view. In FIG. 1, 17 is a cylindrical vibration meter body. A disk-shaped permanent magnet 18 for fixing the vibration meter to a mechanical structure is mounted on the side of the vibration meter body 17 that is connected to the surface to be measured 30.
is integrated with the vibration meter main body 17. The structure of the permanent magnet 18 that also serves as a pedestal is that the N pole 18a and the S pole 18
b are provided concentrically, and an insulator such as aluminum is embedded in an annular groove 19 separating these two poles to prevent dust and iron chips from entering. A stepped through hole 20 is provided in the center of the permanent magnet 18,
A detection rod 22 is inserted into this through hole 20 with a gap in between. The detection rod 21 is elastically supported at its upper end by the permanent magnet 18 via a mounting seat 23 by a leaf spring 22 as an elastic body. At this time, the tip of the detection rod 21 formed in a spherical shape projects slightly (about 0.5 to 1.0+n+n) from the attraction surface of the permanent magnet 18 when not measuring. And the vibration sensor l is the detection rod 2
It is attached to the upper end of 1. Note that 24 is a sealing material made of silicone rubber that prevents dust from entering through the gap in the penetrating portion of the detection rod 2, and is bonded to the stepped portion of the permanent magnet 18. FIG. 1 shows the adsorption state, in which the temporary spring 22 is bent by the above-mentioned amount of protrusion of the detection rod 21, and as a result, the detection rod 21
is pressed against the surface to be measured 30 by the reaction force of the leaf spring 22. Therefore, the vibration of the surface to be measured 30 is transmitted to the vibration sensor 1 via the detection rod 21. Figure 3 shows the situation when the vibration meter shown in Figure 1 is attached to the uneven surface shown in Figure 5.
), the attraction surface of the permanent magnet 18 is caused by vibration to cause the surface to be measured 30 to
Figure 3 (B) shows the state in which it has returned to its original position. Even if the vibration meter makes such a movement, the vibration of the measurement surface 30 can be accurately measured by the vibration sensor 1 if the detection rod 21 and the surface to be measured 30 do not separate and are in contact with each other at point P in the figure. Therefore, a condition in which the entire vibration meter vibrates due to a gap caused by the unevenness of the surface to be measured 30 and the detection rod 21 moves away from the surface to be measured 30 will be described. This problem can be replaced by a chattering phenomenon in which the detection rod 21 dances on the surface to be measured 30 due to the vibration of the vibrometer, and experimentally it has been found that the tracking limit of the detection rod 21 in this case is expressed by the following formula. It is worth considering. α. -to-P/W-g where α. is the limit acceleration of the vibration meter body 17 (cm/s
ec"), P is the pressing force (kg) of the detection rod 21, W is the weight of the movable part (kg) that is the sum of the vibration sensor l, the detection rod 21, and a part of the elastic body 22, and g is the gravitational acceleration (980 cm).
/sec”).K is a coefficient, which is 0.95 for light dancing and 1.15 for complete dancing.In other words, the vibration acceleration of the vibration meter body 17 is α If the detection rod 21 exceeds . Even if the protrusion amount of the detection rod 21 from the suction surface exceeds the set amount, the detection rod 21 will separate from the surface to be measured 30 and accurate measurement will not be possible. The following limit will be explained. The attraction force of the permanent magnet 18 can easily be maintained at 10 kg on a smooth surface without using a special high-performance magnetic material. Since the surface is uneven, This is 1/10
(= l kg). On the other hand, the weight of the movable part 1W = 0.01 kg, the pressing force P due to the deflection of the elastic body 22 must be sufficiently smaller than the attractive force of the permanent magnet 19, and if P = 0.3 kg, the limit acceleration α. -28,
It becomes 5-34.5g. The vibration monitoring level for unbalance and misalignment of general rotating machines cannot exceed 1.0 g in terms of acceleration. Since the vibration level of the vibration meter body is considered to be about the same level as this, even if the adsorption state of the permanent magnet 18 at 3 degrees of the measured surface becomes extremely unstable, the above-mentioned limit acceleration α will be maintained in actual vibration measurement. It can be considered that there is sufficient margin for this, and the vibration of 3° on the surface to be measured is faithfully transmitted to the vibration sensor l. In addition, as shown in FIG. 4, if a permanent magnet 25 having a fixing hole 25a and directly connected to the vibration sensor 1 is separately prepared and used in place of the permanent magnet 18, the mechanical It can also easily be used when permanently fixed to a structure for monitoring.

【Effect of the invention】

According to this invention, it is easy to attach and detach the vibration meter to and from the surface to be measured, and even if the attachment becomes unstable depending on the condition of the surface to be measured, vibration measurement can be performed reliably. Therefore, the vibrations of many mechanical structures can be easily measured with one vibration device, and maintenance of mechanical equipment by vibration monitoring can be widely used.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing an embodiment of the present invention, FIG. 2 is a block diagram showing the circuit configuration of the vibration meter shown in FIG. 1, and FIGS. Figure 4 is a side view showing a permanent magnet that can be used in the vibration meter shown in Figure 1, and Figure 5 is a side view explaining the usage status of the conventional vibration meter. be. 1: vibration sensor, 2 to 8 control circuits, 9: digital display circuit, 10: operating power supply, 18: permanent magnet, 21: detection rod, 22: elastic body, 30: surface to be measured. Procedural Dispute Form (Method) Person who amends the name of the invention (vibrometer) (A) (B) Relationship to the case

Claims (1)

[Claims] 1) A vibration sensor that detects the vibration of a mechanical structure as an electrical signal, a display circuit that digitally displays the vibration level, a control circuit that converts the electrical signal of the vibration sensor into a digital signal and drives the display circuit, an operating power source, etc. A vibration meter that has an integral structure includes a permanent magnet for fixing the vibration meter body to a mechanical structure, and a detection rod supported by an elastic body with the tip of the permanent magnet slightly protruding from the attraction surface. , a vibration meter characterized by having a vibration sensor attached to this detection rod.