[0018] The present invention proposes a fault diagnosis device for rotating equipment. The device uses piezoelectric effect and electrostatic induction to reflect the rotation during rotation on the surface charge of piezoelectric material. When a fault occurs, the different characteristics of the fault will cause Different amounts of charge are generated on the surface of the material, and the use of electrostatic sensors to collect charge signals can obtain real-time rotation information, which can be input to a PC for fault diagnosis. The device contains several piezoelectric conversion elements, electrostatic sensors, signal conditioning units and a PC for fault identification. The device fixes several piezoelectric conversion elements on a rotating object, and then performs non-contact measurement through an electrostatic sensor, and finally uses a signal conditioning unit to amplify and filter the signal, and finally sends it to a PC for fault diagnosis. The piezoelectric conversion element uses the centrifugal force during rotation to convert rotation information into charge information, uses an electrostatic sensor to induce charge information, and the signal is processed by the signal processing unit for fault diagnosis by the PC.
[0019] The implementation steps of this device are mainly as follows:
[0020] 1) Piezoelectric conversion element as attached figure 1 As shown, the metal base 1 is used to fix the entire element on the rotating shaft. The metal base contains piezoelectric material 2, mass 3, and pre-tension spring 4. The pre-tension spring makes the mass to maintain a certain amount of piezoelectric material in the static state. Acting force, the piezoelectric material is in a "convex" shape, one side is in contact with the mass, and the other side is clamped to the periphery of the base, so that the piezoelectric material is exposed to the outside air and the piezoelectric is converted according to the number of piezoelectric induction elements The components are evenly distributed and fixed on the rotating shaft under test through the base.
[0021] 2) The sensor structure is attached figure 2 As shown, the sensor is surrounded by a shielding cover 5, the sensing electrode 6 and the shielding cover are connected by insulating material, the sensing electrode is connected to the charge voltage conversion circuit 7, and the circuit output is connected to the outside by the shielding line 8. The circuit is located inside the shielding cover. Grounding to form an electrostatic shield, install a number of electrostatic sensors evenly on the periphery of the rotating shaft, and make the sensor and the piezoelectric conversion element on the same plane, according to the size of the measured shaft and the measurement environment, the distance between the sensor and the piezoelectric conversion element Choose between 2-6mm.
[0022] 3) The block diagram of the fault diagnosis system for rotating equipment is attached image 3 As shown, after the piezoelectric conversion element 9 and the electrostatic sensor 10 are installed, the sensor output is connected to a signal conditioning circuit. The conditioning circuit mainly realizes signal amplification and filtering. The output signal of the conditioning circuit is transmitted to the PC through the AD capture card to realize the signal Analysis and processing, so as to realize the fault diagnosis of rotating machinery.
[0023] The piezoelectric conversion element is characterized in that the piezoelectric material of the rotation sensitive element is lead zirconate titanate, which is a piezoelectric ceramic material with a length of 30 mm, a width of 4 mm, and a thickness of 3 mm. The quality part is made of lead material. The number of conversion elements can be 4-12 according to the requirements of the measurement object and environment.
[0024] In the electrostatic sensor, the sensing electrode is a thin row electrode. According to the size of the measurement object, the length is 20mm-30mm, and the width is 2mm-5mm. The electrode material is copper. The number can be 4-12 according to the requirements of measurement accuracy and environment. One.
[0025] Such as Figure 4 As shown, the force analysis of the piezoelectric conversion element is performed. When the rotational speed is ω, the piezoelectric conversion element is located at the angle θ, and the force analysis of the mass part is the first choice to obtain the following expression:
[0026] F support = F 0 +mω 2 R-mg sin(θ)
[0027] Where F support Is the supporting force provided by the piezoelectric material on the mass, F 0 Is the pre-tightening force, m is the mass of the mass, and R is the radius of rotation of the mass center of the mass.
[0028] Such as Figure 5 As shown, the force analysis of piezoelectric materials shows that:
[0029] F Branch 1 = F 1 +m 1 ω 2 R 1 -m 1 g sin(θ)
[0030] Where F Branch 1 Is the support provided by the base shell, that is, the pressure on the outer surface of the piezoelectric material, F 1 Is the pressure of the mass on the piezoelectric material that is the pressure on the inner surface of the piezoelectric material, m 1 Is the quality of piezoelectric material, R 1 Is the radius of rotation where the centroid of the piezoelectric material is located. Because F 1 Equal to F support , The pressure on the inner and outer surfaces of the piezoelectric material is as follows:
[0031] F Inside = F 0 +mω 2 R-mg sin(θ)
[0032] F outer = F Inside +m 1 ω 2 R 1 -m 1 g sin(θ)
[0033] Since the mass of the piezoelectric material is negligible relative to the mass of the mass, the pressure on the inner and outer surfaces is approximately equal. Then the charge on the surface of the piezoelectric material is:
[0034] Q=d 33 (F 0 +mω 2 R-mg sin(θ))
[0035] At the same time, considering that the vibration of the device will act on the mass, the charge on the surface of the piezoelectric material is:
[0036] Q=d 33 (F 0 +mω 2 R-mg sin(θ)+F v )
[0037] In the formula, F v Is the force acting on the surface of the piezoelectric material through the mass when the device vibrates, d 33 Is the piezoelectric coefficient of piezoelectric ceramics.
[0038] When the equipment fails, if the failure can significantly affect the radius of rotation, it will affect the mω in the pressure 2 The R component changes the amount of charge, such as unbalanced rotor, bent shaft, loose bearing, misalignment of shafting; if the fault affects the rotation speed, it will also affect the mω in the pressure. 2 The R component thus changes the amount of charge, such as rotating stalls; when equipment surges, structural resonance and other faults will affect F v Component, thereby changing the amount of charge.
[0039] Since the piezoelectric conversion element sequentially passes near the electrostatic sensor when rotating, the electrostatic signal presents a certain periodicity, which can be used for speed calculation. When the device fails, it will be reflected on the surface charge of the piezoelectric material, and the relevant signal can be collected by the electrostatic sensor installed nearby, which can be used for fault diagnosis of the rotating device.
