JPH10132790A - Apparatus for measuring concentration of magnetic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic powder concentration-measuring apparatus which can easily and correctly measure the concentration of magnetic powder without a manual adjustment, even when the ambient temperature of the apparatus changes. SOLUTION: The apparatus is constituted so that a sample with a magnetic powder mixed therein can be inserted to at least either of an exciting coil L1 and a detecting coil L3 arranged at a magnetic path of the exciting coil L1. A concentration of the magnetic powder included in the sample is obtained on the basis of an induced voltage induced to the detecting coil L3. A temperature-sensitive element showing an NTC characteristic (having a negative temperature coefficient whereby a resistance value decreases when a temperature rises) is connected in series to the coil L1, so that a current value flowing in the coil L1 is maintained constant irrespective of the ambient temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention indirectly diagnoses deterioration such as abrasion damage of bearings of various machines by measuring the concentration of magnetic powder such as iron powder mixed in lubricant such as lubricating oil or grease. More specifically, the magnetic powder concentration measuring device is configured so that a sample mixed with magnetic powder can be inserted into at least one of an excitation coil or a detection coil disposed in a magnetic path of the excitation coil, and the sample is induced by the detection coil. The present invention relates to a magnetic powder concentration measuring device using an electromagnetic induction method for obtaining the concentration of magnetic powder contained in a sample based on an induced voltage.

[0002]

2. Description of the Related Art Conventionally, a magnetic powder concentration measuring apparatus employs a simple electromagnetic induction method in which a single excitation coil and a single detection coil are arranged in a common magnetic path, and a pair of serially connected magnetic powders. Equivalent excitation coils were arranged on a common axis so that the magnetic fields of the respective excitation coils faced each other, and a detection coil was arranged on the common axis at a position where the combined magnetic field of the pair of excitation coils became zero. Some employ a magnetic balance type electromagnetic induction method, and some employ a differential detection coil type electromagnetic induction method in which a single excitation coil is sandwiched between a pair of detection coils on a common axis.

[0003]

In the conventional magnetic powder concentration measuring apparatus described above, the zero point adjustment and the span adjustment are performed in advance by measuring a reference sample or the like. Due to the change of the zero point and / or the output span even after the adjustment, the reliability of the measured value cannot be compensated unless readjusted before the measurement. Is
When a sample lubricant to be sampled is sampled from a rotating machine or the like, since the temperature of the lubricant is higher than the ambient temperature, there is an inconvenience that the measured value is not stable for a long time until the temperature drops to the ambient temperature. Was. Therefore, conventionally, an extremely troublesome operation of manually re-adjusting every measurement is required, and the operation is often forgotten. For example, as a mechanism for zero point correction, a circuit that adjusts the reference voltage of an operational amplifier that amplifies the output from the detection coil, or the data of the output stage when no sample is inserted, is obtained from actual measurement data. There are those provided with storage means for storing as zero-point correction data for subtraction, and a manual operation unit such as a volume or a switch for operating those mechanisms is provided, and readjustment is performed by manual operation of the operation unit. It is. The object of the present invention, in view of the above-mentioned conventional problems,
It is an object of the present invention to provide a magnetic powder concentration measurement device that does not require manual adjustment even when the ambient temperature of the device changes, and enables easier and more accurate measurement.

[0004]

In order to achieve this object, a first characteristic configuration of the magnetic powder concentration measuring device according to the present invention is as described in claim 1 of the claims. A sample mixed with magnetic powder is inserted into at least one of the detection coils arranged in the magnetic path of the exciting coil, and the concentration of the magnetic powder contained in the sample is determined based on an induced voltage induced in the detection coil. A magnetic powder concentration measuring device to be sought, wherein a temperature-sensitive element exhibiting NTC characteristics is connected in series to the coil, and the current value flowing through the coil is kept constant regardless of the ambient temperature. . A second characteristic configuration is that, as described in claim 2 of the claims, a sample mixed with magnetic powder can be inserted into at least one of the excitation coil and the detection coil arranged in the magnetic path of the excitation coil. A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in the sample based on an induced voltage induced in the detection coil, wherein a power supply for excitation to the excitation coil is constituted by a constant current source. There is a point. The third characteristic configuration is claim 3 in the claims section.
As described in, the excitation coil or the detection coil arranged in the magnetic path of the excitation coil is configured to be able to insert a sample mixed with magnetic powder into at least one of the detection coil, based on the induced voltage induced in the detection coil A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in a sample, wherein the coil is formed using a wire having a temperature coefficient of a resistance component of 5 × 10 ⁻⁵ or less. The fourth characteristic configuration is such that, as described in claim 4 of the claims, a sample mixed with magnetic powder can be inserted into at least one of the excitation coil and the detection coil arranged in the magnetic path of the excitation coil. A magnetic powder concentration measuring device for obtaining the concentration of magnetic powder contained in the sample based on an induced voltage induced in the detection coil, wherein the exciting current source to the exciting coil outputs a square wave current And the detection coil forms a resonance circuit.

The operation will be described below. Generally, the resistance component R of a coil is represented by the following equation. R = R ₀ (1 + αΔT) Here, R ₀ is a resistance value of the coil at a specific temperature, α is a temperature coefficient of the coil, and ΔT indicates a temperature change. Therefore, according to the first characteristic configuration, the coil is NTC
If a temperature-sensitive element exhibiting characteristics (a characteristic having a negative temperature coefficient in which the resistance value decreases as the temperature increases), for example, a thermistor is connected in series, the coil resistance increases as the coil temperature increases, but the resistance of the temperature-sensitive element increases. Since the value becomes small, the resistance value can be kept constant as a whole, and in that case, the current value flowing through the coil can be kept constant. According to the second characteristic configuration, since the excitation power supply to the excitation coil is configured by the constant current source, the coil current can be maintained constant even if the resistance changes due to the temperature rise of the excitation coil. is there. According to the third characteristic configuration, the temperature coefficient of the resistance value is extremely small, for example, a manganin wire (Mn-Ni-Cu).
By using a wire such as an alloy), it is possible to minimize the influence of temperature under normal use conditions. According to the fourth characteristic configuration, for example, a capacitance element and a resistance element are connected in parallel to the detection coil while the excitation current source for the excitation coil is configured by an inexpensive square wave output power supply that outputs a square wave current. To form a resonance circuit,
If the output is taken out, it is possible to obtain a sine wave output while avoiding generation of noise due to parasitic vibration appearing in the output of the detection coil alone.

[0006]

Therefore, according to the first to third features, even when the ambient temperature is changed or the lubricant at a high temperature is measured as a sample, the operator does not need to perform any readjustment operation. Even without performing, zero point and output span adjustment are performed automatically,
It is possible to provide a magnetic powder concentration measurement device that can always measure in a stable state, and according to the fourth characteristic configuration, it is possible to accurately generate noise while suppressing the generation of noise while using an inexpensive power supply. It has become possible to provide a magnetic powder concentration measuring device that can be measured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic powder concentration measuring device according to the present invention will be described below. As shown in FIG. 1, the magnetic powder concentration measuring device is provided with an exciting coil L1 to which a thermistor Th is connected in series, and on a common axis P with the exciting coil L1, that is, in a magnetic path of the exciting coil L1. Measuring means surrounding the detecting coil L3 with a magnetic shield member, power supply means 2 for supplying an exciting current to the exciting coil L1, and processing means 3 for calculating and deriving a magnetic powder concentration from an output signal of the detecting coil L3. It is configured to be provided inside the housing 1. An insertion hole 1a for inserting a non-metallic sample container made of glass, resin or the like in which the sample S mixed with the magnetic powder is sealed is formed on the upper surface of the housing 1, and the insertion hole 1a is inserted through the insertion hole 1a. In a state where a flange portion formed at the upper end of the sample container is supported on the upper surface of the support portion 1b of the housing 1,
It is inserted into the exciting coil L1 immediately below the insertion hole 1a.

The power supply means 2 comprises a power supply circuit 2a having a dry cell, and an oscillation circuit 2b for outputting an alternating current of about 30 kHz to 200 kHz from the DC power supplied from the power supply circuit 2a. The processing means 3 includes a first amplifying circuit 3a for amplifying an output AC signal of the detection coil L3, and synchronously detecting the amplified AC signal with an output signal of the oscillation circuit 2b to output a DC voltage. Synchronous detecting circuit 3b, a second amplifying circuit 3c for amplifying the output of the synchronous detecting circuit 3b, and a second amplifying circuit 3c.
A / D conversion circuit 3d for quantizing the amplified signal by the above-mentioned method, and the sample S based on the quantized data based on a predetermined conversion formula.
Processing unit 3 for calculating and deriving the magnetic powder concentration contained in
e, and a display unit 3f using a liquid crystal or the like, for example, for displaying a calculation result by the calculation processing unit 3e. Thus, the excitation coil L1 corresponding to the concentration of the magnetic powder contained in the sample S is provided. A change in magnetic flux due to a change in internal magnetic permeability is obtained by measuring an induced voltage of the detection coil L3,
It is converted to the concentration of the magnetic powder contained in the sample S.

The thermistor connected in series to the coil L1 is a temperature sensitive element exhibiting NTC characteristics, that is, characteristics having a negative temperature coefficient in which the resistance value decreases as the temperature increases.
The coil resistance increases as the coil temperature rises due to changes in the ambient temperature of the device or insertion of a high-temperature sample container.
Since the resistance value of the temperature sensing element is reduced, the current value flowing through the coil is maintained constant by keeping the resistance value constant as a whole, thereby preventing zero point fluctuation and output span fluctuation. In addition, besides thermistors, semiconductor P
The temperature characteristics of the N junction may be used. Here, the temperature compensation effect can be further enhanced by providing the coil to which the temperature-sensitive element having the NTC characteristic is connected in series not only in the exciting coil L1 but also in the detection coil L3.

Next, another embodiment of the magnetic powder concentration measuring apparatus according to the present invention will be described. In the previous embodiment, the one using the temperature sensing element for temperature compensation has been described.
Instead of using a temperature sensing element for temperature compensation, a constant current power supply may be used as the power supply means 2. That is,
Although the coil resistance increases as the coil temperature increases, the value of the current flowing through the coil can be kept constant by using a constant current source for the exciting current. As described above, the temperature compensation effect can be further enhanced by connecting the temperature-sensitive element having NTC characteristics in series to the detection coil L3.

In the above embodiment, the temperature compensation element using the temperature compensation element has been described. Instead of using the temperature compensation element for temperature compensation, the coils L1 and L3 have a small temperature coefficient of a resistance component. For example, a manganin wire (Mn-Ni-
By configuring the coil using a wire such as a Cu alloy), the effect of temperature may be suppressed as much as possible in a normal use condition of about -20 ° C to 60 ° C.

In the above-described embodiment, the case where the measuring means is constituted by the single excitation coil L1 and the single detecting coil L3 has been described. However, the measuring means may be any as long as it employs the electromagnetic induction method. Can be adopted. That is, as shown in FIG. 2, a pair of equivalent exciting coils L1 and L2 connected in series are provided inside the casing 1 by a vertical common axis center such that the magnetic fields generated by the exciting coils L1 and L2 face each other. P, and a position where the combined magnetic field of the pair of exciting coils L1 and L2 is zero on the common axis P, that is, the common axis P and the axis at the center of both coils L1 and L2. The detection coil L3 is disposed such that the measurement coils are overlapped with each other, and the measurement means is configured by surrounding the pair of excitation coils L1 and L2 and the detection coil L3 with a magnetic shield member. The temperature compensation mechanism described in the embodiment may be adopted.
Here, the detection coil L3 is screwed with a ferrite core as an iron core FC having a thread formed in a peripheral portion, and the sample S is not inserted into the excitation coil L1, or
When an induced voltage is generated in the detection coil L3 due to a displacement or the like of the detection coil L3 in a state where the inserted sample S does not include the magnetic powder, the position of the detection coil L3 is changed in a manufacturing stage. Without performing, the zero point can be easily adjusted by adjusting the position of the iron core FC in the direction of the axis P, and the magnetic resistance in the detection coil L3 is reduced to improve the detection sensitivity. is there. Further, as shown in FIG. 3, a differential detection coil type electromagnetic induction method in which a single excitation coil L1 is sandwiched between a pair of detection coils L3 and L4 on a common axis is adopted as described above. The temperature compensation mechanism described in the first to third embodiments may be adopted.

In addition to the above-described embodiment, the power supply means 2, which is a current source for exciting the exciting coil, does not have to output a sine-wave current. For example, a power supply circuit having a dry cell or the like may be used. And an inexpensive circuit configuration including an oscillator circuit having an oscillator, a frequency divider circuit for dividing the output thereof, and a driver circuit connected to the output terminal of the frequency divider circuit for outputting a square wave current May be adopted.
In this case, if a resonance circuit is configured by connecting a capacitance element and a resistance element in parallel to the detection coil, a sine wave output can be easily generated while avoiding the occurrence of noise due to parasitic vibration appearing in the output of the detection coil alone. If the output is synchronously detected by the power supply output, a highly accurate output can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic powder concentration measuring device.

FIG. 2 is a configuration diagram of a main part of a magnetic powder concentration measuring apparatus showing another embodiment.

FIG. 3 is a configuration diagram of a main part of a magnetic powder concentration measuring apparatus showing another embodiment.

[Explanation of symbols]

 L1 excitation coil L3 detection coil

Continuing from the front page (72) Inventor Masanori Miyoshi 2-5-4 Mitsuyanaka, Yodogawa-ku, Osaka-shi, Osaka Inside New Cosmos Electric Co., Ltd. (72) Osamu Kitamura 1-2-2, Kotoen, Nishinomiya-shi, Hyogo Prefecture

Claims (4)

[Claims] 1. A structure in which a sample mixed with magnetic powder is inserted into at least one of an excitation coil and a detection coil arranged in a magnetic path of the excitation coil, and the detection coil is configured to detect the voltage based on an induced voltage induced in the detection coil. A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in a sample, wherein a temperature-sensitive element exhibiting NTC characteristics is connected in series to said coil, and a current value flowing through said coil is kept constant regardless of an ambient temperature. Magnetic powder concentration measuring device configured as above. 2. A structure in which a sample mixed with magnetic powder is insertable into at least one of an excitation coil and a detection coil disposed in a magnetic path of the excitation coil, and wherein the sample is formed based on an induced voltage induced in the detection coil. What is claimed is: 1. A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in a sample, wherein a power source for exciting the exciting coil is constituted by a constant current source. 3. A configuration in which a sample mixed with magnetic powder is insertable into at least one of an excitation coil and a detection coil arranged in a magnetic path of the excitation coil, and based on an induced voltage induced in the detection coil, A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in a sample, wherein the coil is formed using a wire having a temperature coefficient of a resistance component of 5 × 10 ⁻⁵ or less. 4. A structure in which a sample mixed with magnetic powder is insertable into at least one of an excitation coil and a detection coil arranged in a magnetic path of the excitation coil, and based on an induced voltage induced in the detection coil, A magnetic powder concentration measuring device for determining the concentration of magnetic powder contained in a sample, wherein an excitation current source to the excitation coil is configured to output a square wave current, and a resonance circuit is configured by the detection coil. A magnetic powder concentration measurement device.