JPS5847244A - Water content rate measuring apparatus for tire - Google Patents

Abstract

PURPOSE:To measure a content rate of water in a tire without hurting it quickly at a high accuracy by detecting output signals generated according to impedance between a pair of electrodes to which alternate current is applied. CONSTITUTION:A pair of electrode rods 1a and 1b mounted on a retaining member 2 are pressed against the inner surface of a tire 6 and a constant current of a high frequency are applied to the electrodes to detect a potential difference according to an impedance therebetween 1a and 1b. The impedance varies according to the content rate of water in rubber. A steel core 12 is buried into a carcass layer 10 inside the tire. But when the electrode rods 1a and 1b are brought into contact with the inner surface 7 of the tire not being inserted thereinto, the water content rate can be measured at a high accuracy free from the effect of the steel cord 12. This also eliminates hurting of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION In particular, the present invention relates to an apparatus for accurately measuring the moisture content of a rubber surface layer and/or carcass layer inside a tire without damaging the tire.

In recent years, in the tire industry, detailed studies have been conducted on the influence of the moisture content of rubber such as the tread, sidewall, and carcass layers that make up tires on tires. This has become necessary in order to more accurately understand the durability of tires used under harsh conditions and the characteristics of each tire. In general, the method of measuring moisture content is proposed by Hashira. It has also been applied to measure the moisture content of tire rubber. For example, a method can be considered in which two needle-shaped sensor electrodes are inserted into a tire, these electrodes are connected to a high-frequency circuit, and the dielectric constant, which changes as a function of the moisture content, is detected as an electrostatic capacitor between the electrodes. However, this method is 2
Since the needle-shaped sensor electrode is inserted into the tire, it has the disadvantage of damaging the tire, and it is not suitable for measuring the moisture content of the rubber surface layer on the outside of the tire such as the tread and sidewall. This method is used to measure the moisture content of the rubber surface layer and carcass layer inside tires such as tires, as the sensor electrode inserted from the inside of the tire is affected by the steel cord that reinforces the carcass layer, making accurate measurements difficult. There is a drawback that it cannot be done.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide a suitably constructed structure that allows the moisture content of the rubber surface layer and/or carcass layer inside the tire to be measured with high precision without damaging the tire. It is an object of the present invention to provide a tire moisture content measuring device.

The moisture content measuring device of the present invention includes a pair of electrodes, a *source circuit that applies an alternating current between these electrodes, and a detection circuit that generates an output signal according to the impedance between the pair of electrodes. The present invention is characterized in that the moisture content of the tire is measured based on the output signal of the detection circuit when a pair of electrodes are brought into contact with the tire surface.

The present invention will be described in detail below with reference to the drawings.

FIGS. 1A and 1B are a plan view and a bottom view showing an example of the configuration of an electrode section of the moisture content measuring device of the present invention. In this example, a pair of IEi? J/a and Ib are respectively mounted parallel to each other on the holding member λ so as to be displaceable in the axial direction, and these electrode rods /a and Ib are pushed out by biasing means such as a coil spring (not shown) provided in the holding member 2. to assist in the direction. The tip shape, cross-sectional area, and center distance l of these 'electrode rods/a and Ib are based on the following conditions: 1) The inner surface of the tire has a curvature, 2) When measuring a steel tire,
The steel cord that reinforces the carcass layer is visible from the inside surface! 3) Grooves provided in the muddy bladder for flushing and sludge in order to remove air between the inner surface of the tire and the muddy bladder during tire warming. Taking into account the fact that a ridge is formed on the inner surface due to this, various experiments were conducted, and the tip shape was a spherical shape with a slight curvature, the cross-sectional area was approximately less than gO + 1l 1112, and the center distance l was less than f. Preferably, it is /3 mtn.

With this configuration, the tips of the poles la, lb can be brought into contact with the inner 11111 surface 3a of the tire 3 as shown in FIG. 2, and the holding member 2 can be pressed toward the inner surface 3a. , electrode rod/a via energizing means.

The tip of Ib can be reliably brought into close contact with the inner surface 3a.

FIG. 3 is a block diagram showing an example of the configuration of a main part of a measuring circuit connected to the above-mentioned pair of electrode rods /a and Ib. Moisture content can also be determined by applying a high-frequency constant voltage between a pair of electrodes and measuring the current flowing between the electrodes, but the impedance of rubber is generally small and in this case, the impedance of the rubber is small and the contact between the electrode and the rubber surface Measured values may vary greatly depending on conditions, and accurate measurements may not be possible. Therefore, in this example, a high-frequency constant current is supplied between the pair of electrode rods /a and Ib from the power supply circuit, and the potentiometer 5 is used to measure the electrode rod /a.
The potential difference between a and Ib is detected according to the impedance. 'The power supply circuit t converts the high frequency output from the high frequency generation circuit pa, for example, j MH2, into a constant current drive amplifier <<b
A constant current of a predetermined value, for example 100 μA, is applied to a pair of 1!
! It is configured to be supplied through the pole 1aIlb.

In this way, when supplying a high-frequency constant current between the electrodes and detecting the potential difference between them, the potential difference depending on the impedance of the rubber, which changes depending on the moisture content, is determined by the contact state between the electrode and the rubber surface. The moisture content can be measured with high precision based on this potential difference.

Next, a measurement mode using the above-mentioned measuring device will be explained with reference to FIG. Tire O shown in the figure is a steel-reinforced truck/bus tire.
The L and outer surface layers are sequentially IJI 112. The carcass layer /θ is located at a depth of approximately 2 to 3 gates from the inner surface 7, and the steel cord /2 is buried in this layer. In this example, in order to measure the moisture content of the inner surface layer 9 of a part of the shoulder of the tire B, a pair of electrode rods/a
, /b are tightly connected to the inner surface 7 as explained in FIG. Measure the potential difference between iws/a and zb. In this way, a pair of electrode rods /a, /
If b is brought into contact with the inner surface 7 and a constant current is supplied without inserting the inner surface layer 9 into the tire t, the inner surface layer 9
The steel cord 12 in the carcass layer 1O near the tire is not affected by the side part of the steel cord 12, and the tire is not damaged.

Note that the present invention is not limited to the above-mentioned example, and can be modified or changed in many ways.

For example, the shape of the tips of the pair of electrode rods /a, /b is not limited to a spherical shape, but may be flat. Further, in the embodiment described above, the pair of electrode rods /a, /i) are separated and the holding member 2
However, as shown in Figure S A, a pair of electrode rods/a
, /b may be coaxially integrated with an insulating member 13 interposed therebetween, or an insulating member may be provided between a pair of i=salary/a and /b that are separately attached as shown in FIG. 5B. It is also possible to insert a /3 and configure these as one. In addition, in these FIGS. A and B, the tip shape of the integrated electrode may be flat, or the entire tip may be formed into a spherical shape.

Further, the pair of electrodes /a and /b are not necessarily displaced 'rT in the axial direction (it is not necessary to attach them to the holding member 2;
It may be fixedly attached to the holding member 2, or it may be attached as shown in FIG.
In the case of an integral structure as shown in B and B, no holding member is used and the outer periphery of the electrode, except for the tip end surface that is brought into contact with the tire, may be insulated. Also, in Fig. 9, it was explained that the moisture content of the inner surface layer 9 was measured, but the moisture content of the inner surface layer 9 and the carcass layer/θ was
Since the correlation between the i' ratios is generally high, it is also possible to calculate the moisture content of the carcass layer/θ based on the measured value of the moisture content of the inner surface layer 9 and display it together. However, it is also possible to display only the moisture content of the carcass layer/θ determined in this way.

As described above, in the present invention, the moisture content can be measured by bringing a pair of electrodes into contact with the tire surface without inserting them into the tire, so the moisture content can be measured without damaging the tire. It is possible to measure the moisture content of the rubber surface layer and/or carcass layer inside the tire with high accuracy and in a short time without being affected by the steel cord in the carcass layer.

[Brief explanation of the drawing]

Figures 1A and B are side and bottom views showing an example of the structure of the electrode part of the moisture content measuring device of the present invention, and Figure 2 is a diagram showing the structure of the electrode part shown in Figures 1A and B on the inner surface of the tire. A diagram for explaining the contact mode, FIG. 3 is a block diagram showing an example of the circuit configuration of part e of the moisture content measuring device of the present invention,
Figure 1 shows a measurement mode using the moisture content measuring device of the present invention.
ft. Diagrams for illustrating FIG. J, FIG. /a, /b... Electrode rod, 2... Holding member, 3...
・Tire, 3a...Inner surface, q...Power circuit, t
la...high frequency generation circuit, sub...constant current drive amplifier, S...potentiometer, t...tire, 7...
Inner surface, g...outer 11111 cinnabar surface, 9...inner (1
Surface layer, /θ... Carcass layer l/... Outer surface layer, 7.2... Steel cord, /3... Insulating member. Patent applicant: Ridgyo Electric Co., Ltd. Same applicant: Brideston Tire Co., Ltd. Figure 1 Mf (1k)

Claims (1)

[Scope of Claims] L comprises a pair of electrodes, a power supply circuit that applies an alternating current between these electrodes, and a detection circuit that generates an output signal according to the impedance between the pair of electrodes; A tire moisture content measuring device, characterized in that the tire moisture content measuring device is configured to measure the tire moisture content based on the output signal of the detection circuit when the tire is brought into contact with the tire surface. 2. What is the cross-sectional area of the tips of the pair of electrodes that contact the tire surface? The invention is characterized in that the pair of chisel frame rods are arranged parallel to each other and displaceable in the axial direction, with a center spacing of less than 20 vm, and a pair of chisel frame rods are attached to the holding member in parallel to each other so as to be displaceable in the axial direction. A device for measuring the moisture content of tires as described in Scope 1. 3. The power supply circuit is configured with a constant current source that supplies a high frequency constant current between the pair of electrodes, and the detection circuit is configured with a potentiometer that measures the potential difference between the pair of electrodes. A tire moisture content measuring device according to claim 1 or 2.