JPH01144374A - Controlling method for electroviscous fluid - Google Patents

Abstract

PURPOSE:To prevent obstacles such as dielectric breakdown and so on by alternately changing a code of voltage to be applied pulsatively between electrodes holding the electroviscous fluid. CONSTITUTION:An actuator is constituted by using the electroviscous fluid which is the liquid to disperse fine grains causing a dielectric polarization by impressed external field into the electric insulating oil. The actuator actuates the electroviscous fluid by impressing the voltage between electrodes holding said fluid. At this time, as impressed voltage, it is so constituted that the voltage changing a code alternately is pulsatively impressed. According to the constitution, the settling due to the charge of fine grains in the electoviscous fluid can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for electrically controlling the operation of electrorheological fluids, i.e. fluids whose viscosity changes significantly in response to the strength of an external electric field. It can be applied to new actuators for clutches, valves, shock absorbers, etc.

[Prior art] When an external electric field is applied to a fluid in which water-containing solid particles such as silica, starch, or cellulose are dispersed in an electrically insulating material such as spindle oil, transformer oil, or chlorinated paraffin, the viscosity of the fluid changes significantly. A phenomenon can be seen. This phenomenon has long been known as the Winslow effect, and its application to clutches, valves, vibration elements, etc. has been studied since the 1940s.

It has been known that electrorheological fluids change their viscosity in response to both direct current and alternating current; however, when a voltage is continuously applied, the voltage value gradually decreases (when a constant voltage is applied, the viscosity changes). There is a problem that there is a tendency for dielectric breakdown to occur easily, and that power consumption is also high. In contrast, British Patent No. 2125230 proposes a method of applying a DC pulse voltage, and states that when used in clutches and brakes, the above problem can be solved and slippage can be effectively controlled.

[Problems to be solved by the invention] Although British Patent 2+25230, which applies a DC pulse voltage, presents an effective method for improving the above-mentioned problem, the voltage value decreases after long-term use. , cannot be called an essential solution. In other words, even with the method of applying direct current in pulses, if used continuously, there is an unavoidable tendency for the applied voltage to decrease (viscosity decreases when constant voltage is applied) and dielectric breakdown, so long-term stable use is impossible. difficult.

[Means for Solving the Problems] The present invention was achieved as a result of underestimating the behavior of particles at the electrode portion and pursuing the causes of the above problems through detailed observation.

In other words, fine particles in an electrorheological fluid are aligned in the direction of the electric field when a voltage is applied, but when a DC voltage is applied, the fine particles tend to migrate to one or, in some cases, both electrode surfaces and deposit on the electrode surface over time. What do you do? The deposited fine particles gradually narrow the electrode spacing, and since the deposited particle portion has an electrical resistance value lower than the original electrical resistance of the electrorheological fluid, the substantial electrode spacing is electrically narrowed as well. Furthermore, it has been found that this deposition does not occur with a uniform thickness on the electrode surface, but often occurs in the form of partial protrusions, causing a more substantial reduction in the electrode spacing.

This phenomenon becomes severe when DC voltage is continuously applied. When a DC voltage is applied in a pulsed manner, it is alleviated to some extent, but the same phenomenon is observed over time.

The inventors of the present invention considered that this phenomenon is due to the chargeability of the fine particles, that is, their tendency to be charged either positively or negatively.

Therefore, it was thought that the occurrence of this phenomenon could be suppressed by alternating the sign of the voltage applied in a pulsed manner, and as a result of repeated experiments, the present invention was successfully demonstrated.

That is, the configuration of the present invention is a control method for actuating an electrorheological fluid by applying voltages of alternately different signs in pulses between electrodes sandwiching the fluid in an actuator using an electrorheological fluid. . .

The electrorheological fluid referred to in the present invention is a fluid in which fine particles that cause dielectric polarization upon application of an external electric field are dispersed in electrically insulating oil, and whose viscosity changes significantly upon application of an external voltage.

Typical fine particles used for this purpose include water-containing fine particles such as silica, starch, and ion exchange resin, and poly(acene).
Semiconductor fine particles such as quinone), aniline black, etc., metal fine particles having an electrically insulating surface such as aluminum whose lip surface is aluminized, and metal silicon whose surface is silicon nitride.

Typical electrical insulating oils include silicone oil, spindle oil, and chlorinated paraffin.

Furthermore, the pulse-like application of voltages with alternating signs as used in the present invention refers to a method in which the polarity of the applied voltage is alternately changed according to a certain rule, as shown in FIG.
and, as in A-2, - a method of changing the polarity for each pulse; as in B, - a method of alternating polarity within a pulse; and a method of changing the polarity at a certain time interval as in C. , can be mentioned.

The pulse width and pulse peak-to-valley ratio (duty ratio) are arbitrary, and the pulse shape is not necessarily a square wave, but may be a sine wave, or in some cases a triangular wave.

The response speed of an electrorheological fluid is generally on the order of a millimeter, and the pulse width responds to the signal within a few milliseconds or more, but in method B, the polarity change (frequency) within one pulse is The higher the value, the greater the power loss; 100
It is preferably Hz or less, particularly 6011z or less.

In short, any waveform may be used as long as it serves the purpose of preventing deposition of fine particles in the electrorheological fluid by alternating the polarity of the voltage applied in a pulsed manner.

Deposition of fine particles on the electrode surface is severe when the fine particles are water-containing or have a small particle size, but even in such cases, the method of the present invention is highly effective, and methods A and B are particularly effective.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. In addition, each component described in the examples! 1 (part) is a part by weight.

Example 1 An electrorheological fluid made by dispersing 30 parts of spherical silica with a particle size of 5 μm (water content 9 νt%) in 70 parts of dimethyl silicone oil (50 cst) was applied to a metal cylinder with an inner diameter of 40+nLQ having the same central axis and a metal with an outer diameter of 38 mm. Rotor gap (1
, On+m). 200sec-' for this fluid
A constant voltage (P-P) with the waveform shown in Table 1 and Figure 2 is applied at a shear rate of was measured.

Note that the viscosity reduction rate is the value immediately before dielectric breakdown, and is the value in Experiment No.
, 1 to No. 4 indicate examples, and 5 to No. 7 indicate comparative examples.

Table 1 1; see Figure 2, m2. Zero-peak voltage, lI3:N
o, 1 to No., and 4 are 4 g [Values after hrl Example 2 In order to investigate the deposition state of silica particles at the electrode part, a tanzak-shaped copper plate electrode (length 50 + am, width 6 cm) was placed on a glass plate.
, thickness 1 aua) were arranged with an electrode gap of 1 hm, and the electrorheological fluid of Example 1 was cast between the electrodes, and the behavior of the particles due to voltage application was investigated. Voltage application is as in Example 1
It was carried out under the same conditions. The results are shown in Table 2.

Table 2 East 1: Experiment No. of Example 1 and Correspondence C Effects of the Invention According to the present invention, one of the major problems when using an electrorheological fluid is that fine particles sink to the electrode surface. , prevents problems such as voltage drop and dielectric breakdown during continuous operation,
This enables stable operation over long periods of time, making a major contribution to the practical application of actuators such as clutches and valves that use electrorheological fluids.

[Brief explanation of the drawing]

FIGS. 1A-1 to 1C show models of applied voltage waveforms. Second figures to G show voltage waveforms applied in Example 1 and Example 2. In each drawing, the horizontal axis shows time and the vertical axis shows voltage. t,...period of voltage application, t6...continuous application time,
t6... continuous release time, t+ and t2... peak and trough times of each pulse. Patent applicant Asahi Kasei Industries Co., Ltd. agent Patent attorney Hide Komatsu

Claims (1)

[Claims] 1. A method for controlling an electrorheological fluid in an actuator using an electrorheological fluid, which comprises applying voltages of alternating signs in pulses between electrodes sandwiching the fluid to actuate the fluid.