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This paper discusses a mechanism of a self-excited vibration of a cleaning blade in a laser printer. We present a coupled-mode flutter model using a finite element model. A stability analysis based on the proposed model is carried out. From this result, it is clarified that two modes couple each other with increasing coefficient of friction. At that time, the natural frequency of the coupled-mode is corresponding to the frequency of the self-excited vibration. This root locus reveals a typical argand diagram for coupled-mode flutter of an undamped system via so-called Hamiltonian-Hopf bifurcation. Furthermore, we discuss about the steady-state amplitude of the self-excited vibration. First, we present a nonlinear amplitude equation by extracting the unstable modes with introduction of the adjoint vector to the eigenvector of the system. Second, from consideration about the nonlinear term which is able to restrain an increasing of amplitude, we decide the nonlinear term referring to the Rayleigh's equation. Then, the unstable mode solution obtained by the method of multiple scales is reconstructed in 2-DOF system by referring to Herrmann and Roussellet's method in pipes conveying fluid. Finally, we present the theoretical equation of the steady-state amplitude. We reveal a validity of our study by a comparison between an experiment and a numerical simulation of some modified blades.

We study the mechanical characteristics of the bounce phenomena in an electrical switching system. The electrical switching system, which is called a card-relay, consists mainly of an electromagnet, an actuator, a traveling contact and a fixed contact. First, the bounce phenomena, which include the impacts and the residual vibrations of both contacts, are investigated experimentally by measuring their velocitieS. Second, such bounce phenomena are examined theoretically using the governing equation in which the electromagnetic elastic coupling in the electrical switching system is considered, and the first and second vibration modes of the traveling contact are taken into account in order to evaluate its complicated behavior. Finally we clarify the feature of the bounce phenomena by comparing the experimental results with the theoretical ones.

The purpose of this paper is to examine fluid flow around a wire electrode, induced by corona discharge in a system of wire and plate electrodes, in order to give some information for the self- excited lateral oscillation of the wire electrode. First, Maxwell's equations governing electrostatic field are calculated numerically in order to obtain the Coulomb force on the fluid particle, distributed throughout the space. Second, the Navier-Stokes equation with a term of external Coulomb force is calculated numerically by the finite difference method. The fluid flow around the wire electrode is obtained after the calculation of the fluid flow between the wire and plate electrodes. As a result, a symmetric pair of fixed vortexes is formed in the wake of the wire electrode. However, there is no vortex shedding from the wake caused by the corona discharge. Moreover, it is suggested that the fluid force on the wire electrode can not necessarily neglected as the excitation force if the wire oscillation is self-excited as the galloping type mechanism.

The purpose of this paper is to examine the induced oscillation of a wire electrode in a system of wire and plate electrodes for the case of an electrostatic field with corona discharge. First, we have shown from experiment that such an induced oscillation is a nonplanar lateral oscillation, of which both horizontal and vertical components are excited with the fundamental natural frequency. It is also shown that the amplitude of the horizontal component exceeds that of the vertical component. Second, the above scillation, which is called a self-excited oscillation, is analyzed theoretically under the assumption that it is excited by the galloping of the wire electrode due to the unsteady corona wind with a time lag. In addition, an experiment is conducted to investigate the effect of the damper, attached near the end of the wire electrode, on relaxation of the self-excited wire oscillation.