JPH0921604A - Method and apparatus for measuring displacement amount of axial center of cylindrical body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly measure the amount of displacement of the axial center of a cylindrical body, by solving an expression generated by the use of each output voltage value of eddy current displacement sensor, a calibrated sensor sensitivity by a sensor sensitivity operation part and coefficient of a term second degree according to the Newton-Raphson's method. SOLUTION: A displacement amount expression generation part 54 generated expressions determining unknown displacement amounts [X(n), X(n)] in directions of two orthogonal axes (X axis, Z axis) of a cylindrical body with the use of calibrated sensor sensitivities [aX(n), aZ(n)] by a sensor sensitivity operation part 53 and coefficients of a degree of second term (CX, CZ) registered in a tangential displacement output characteristic calibration part 52. A displacement amount calculation part 55 solves the expressions generated by the generation part 54 according to the Newton-Raphson's method. In this manner, displacement amounts [X(n), Z(n)] in two orthogonal axial directions (X axis, Z axis) of the cylindrical body are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring an axial displacement of a cylindrical body for measuring the axial displacement of a relatively thin cylindrical body such as a drive shaft of an automobile in real time.

[0002]

2. Description of the Related Art In the development of automobiles, the optimum design of the drive shaft joint portion that influences the magnitude of the vibrating force of these sound vibration phenomena in order to improve the start-up vibration, beat noise, etc., of a front-wheel drive vehicle in particular. Is an important issue. For that purpose, it is necessary to quantitatively grasp the dynamic change of the joint angle of the drive shaft when the vehicle is running. Therefore,
It is necessary to develop a device that can measure the joint angle of the drive shaft in the actual vehicle running condition under dark environment such as dust, water, mud, oil, temperature etc. Has been.

In order to measure the joint angle of such a drive shaft in an actual running state, it is necessary to measure the behavior of the central axis of a cross section of the cylinder at one point or at a plurality of points. Examples of the non-contact type sensor that may be used to measure the behavior of a certain cylinder include an ultrasonic displacement sensor, a laser displacement sensor, an optical displacement sensor, and a capacitance displacement sensor. However, under severe environmental conditions such as the actual driving condition of the above-mentioned vehicle, all of these types of sensors can collect dust, water,
Measurement is impossible if mud, oil, etc. adheres to the sensor head part, or it cannot be used because it is easily affected by temperature and cannot be measured accurately, its size is too large, its vibration resistance is poor, etc. The only possible sensors are eddy current displacement sensors.

Therefore, conventionally, there has been known an axial center displacement measuring device using a eddy current displacement sensor as shown in FIG. This conventional axial center displacement measuring device for a cylindrical body has two eddy current displacement sensors 1x and 1z in two orthogonal axes directions, an x direction and az direction (hereinafter, referred to as a vertical direction z axis of a vehicle, and x in the left and right directions). The description will be given by setting the y-axis in the axial direction and the front-back direction. Therefore, in the following description, the y-axis can be used instead of the x-axis, and the x- and y2-axis directions can also be considered). The sensor head portion is placed on the surface of the cylindrical body 2 and the distance d between the surface of the cylindrical body 2 and the sensor head portion is measured independently in each direction. The amplifier outputs the voltage signal (Vx, Vz) proportional to the output distance d.
P) Amplified by each of 3x and 3z, further A / D converted and sampled by the A / D converter 4, inputted to the arithmetic processing unit 5 as a digital signal, and subjected to a predetermined arithmetic processing to be described later to obtain the cylindrical body 2 The displacement amounts (x, z) in the two orthogonal axes directions are calculated and stored, and the data of the calculation result is D / A converted by the D / A converter 6 as necessary.
The information is converted and displayed on the display device 7 in an appropriate form.

Measurement of the axial displacement of the cylindrical body by the conventional axial displacement measuring device for the cylindrical body is performed as follows in accordance with the flowchart shown in FIG. First, the output voltage value of each of the sensors 1x and 1z is set to 0 in the initial reference state, and for the displacement of the cylindrical body 2 in the x direction, the voltage signal Vx output from the eddy current displacement sensor 1x is amplified by the amplifier 3x. Then, A / D conversion is performed by the A / D converter 4, sampling is performed at a predetermined cycle, and the sampling data Vx (n) is input to the arithmetic processing unit 5, and the cylindrical body 2
For the displacement in the z direction, the voltage signal Vz output from the eddy current displacement sensor 1z is amplified by the amplifier 3z, A / D converted by the A / D converter 4, sampled at a predetermined cycle, and the sampling data Vz. (n) is input to the arithmetic processing unit 5 (step S1).

With respect to the input data Vx (n) [V], Vz (n) [V] at each sampling timing, the sensor sensitivity ax which is registered in advance and which indicates the sensor output voltage per unit displacement amount The displacement amounts x (n) and z (n) in the x-axis and z-direction are calculated by dividing by [V / mm] and az [V / mm] (steps S2 and S3). The displacement amount calculation at each sampling timing is repeatedly executed, and the results are sequentially stored (step S
4). Then, if necessary, the calculation result is converted into a D / A converter 6
D / A conversion is performed through the display device 7 and the display device 7 displays the data.

[0007]

However, such a conventional axial center displacement measuring device for a cylindrical body has the following problems. One of the problems is that the influence of the sensor output error due to the circular cross section of the cylindrical body 2 cannot be avoided. As shown in FIG. 8, when the cylindrical body 2 is displaced by Δz in the z direction from the state 2a shown by the broken line to the state 2b shown by the solid line (in this case, for the sensor 1z in the z-axis direction, radial displacement, x-axis Direction sensor 1
For x, the displacement is in the cutting line direction), and the distance in the x direction from the sensor head portion of the sensor 1x in the x direction to the surface of the cylindrical body 2 is increased by εx. Therefore, in the ideal measurement, only the z-direction sensor 1z should output Vz (Δz), but the x-direction sensor 1x also outputs Vx (εx).
Will be output, and it will be regarded as if it was displaced in the x direction, and this will appear as an error.

Another problem is that the size of the sensor that can be used is limited by the size of the diameter of the cylinder to be measured, which is unique to the eddy current displacement sensor. An eddy current displacement sensor with a diameter less than or equal to 1/4 must be used. For example, φ
In order to measure the axial center behavior of the 25 drive shafts, accurate measurement cannot be performed unless a sensor having a diameter of φ6 or less, which is ¼ of that, is used. This is because the output sensitivity of the sensor (sensor output voltage per unit displacement amount) is kept constant when the diameter of the cylinder to be measured is not more than four times the diameter of the eddy current displacement sensor as shown in FIG. This is because it cannot be done.

Therefore, the diameter of the drive shaft of an automobile is about φ25, and when this drive shaft is a cylindrical body to be measured, if it is ¼ or less of that, it is necessary to use a sensor with a diameter of φ6 or less. There is no eddy current displacement sensor having such a small sensor and a measuring range capable of covering the displacement range of a cylindrical body having a displacement range of about 10 mm like a drive shaft.

An eddy current displacement sensor which can cover a displacement range of the drive shaft of 10 mm as a measurement range has a diameter of about 20 to 22 at the smallest.
However, when the displacement amount of the drive shaft is measured using a sensor having such a diameter, as shown in FIG. 10, it is -5 mm within the measurable range (-5 mm to +5 mm) of the sensor.
The sensor sensitivity is almost constant up to 1 mm, but when it is 1 mm or more, it tends to decrease linearly as the displacement increases.

For this reason, conventionally, it has been impossible to measure the dynamic displacement of a cylindrical body having a small diameter and a large axial displacement, such as a drive shaft.

By solving such problems, φ20 to φ22
In order to accurately measure the dynamic behavior of a cylindrical body having a diameter of about φ25 with an eddy current displacement sensor of size, as shown in FIG. 11, at each point of x and z coordinates around the cylindrical body 2 to be measured, in the x direction. , The relationship between the displacement amount (xi, zj) in the z direction and the output voltage (Vxi, Vzj) is experimentally obtained, and is registered in the arithmetic processing device 5 as a data table for actual measurement. Measured sensor output voltage (V
A method of determining the actual displacement amount (x, z) by referring to this table for x, Vz) can be considered.

However, this method has a problem in that, when an accuracy of 0.1 mm is required, a large amount of data should be registered in the table, resulting in a huge number of steps. Also,
Prior to the actual measurement, the output voltage (Vx, Vz) at the first (x, z) position needs to be exactly matched with the value in the table, and the work is also troublesome.

The present invention has been made in view of the above-mentioned problems of the prior art, and an eddy current displacement sensor having a relatively large diameter can be obtained by simply registering a small number of data as calibration data as an initial setting. It is an object of the present invention to provide a method and apparatus for measuring the axial center displacement of a cylindrical body that can accurately measure the axial center displacement of a cylindrical body having a relatively small diameter such as a drive shaft.

[0015]

According to a first aspect of the present invention, there is provided a method for measuring an axial center displacement amount of a cylindrical body, comprising: two orthogonal axes (hereinafter, x axis and z axis in a plane perpendicular to the axial center of the cylindrical body). However, the eddy current sensor installed in the direction of the orthogonal three axes x, y, z may be the other two axes). The distance to the peripheral surface of the cylinder is measured by the voltage value (Vx, Vz). ), The cylindrical body is moved in the radial direction (x
Direction, z direction), the unit displacement in the radial direction (ax, az) at an arbitrary distance (x, z) to the peripheral surface of the cylinder and the output voltage value (Vx, Vz) of the corresponding sensor )
The relational expressions (ax = ax (Vx), az = az (Vz)) with and are registered in advance as sensor sensitivity calibration formulas, and the cylindrical body has a cutting line direction (z direction,
The relation between the displacement amount d in the cutting line direction of the cylinder and the output voltage value (Vx, Vz) of the sensor when it is displaced in the x direction) is a quadratic equation,

(Equation 3) The quadratic coefficient (Cx, Cz) of the quadratic equation obtained by approximating with is registered in advance, and the voltage value detected by each eddy current displacement sensor ( Vx, Vz) is substituted into the sensor sensitivity calibration formula to calculate the calibrated sensor sensitivity (ax, az), and the output voltage value (Vx, Vz) of each eddy current displacement sensor and the sensor sensitivity calibration calculation unit Using the calibrated sensor sensitivities (ax, az) and the quadratic coefficient (Cx, Cz) according to
simultaneous equations that determine the amount of displacement (x, z) in each of the z-axis directions,

(Equation 4) Is generated and the simultaneous equations are solved by the Newton-Raphson method to obtain the displacement amounts (x, z) in the directions of the two orthogonal axes of the cylindrical body.

According to a second aspect of the present invention, there is provided a cylindrical body axial center displacement measuring device which is installed in two directions orthogonal to a plane perpendicular to the central axis of the cylindrical body, and the distance to the peripheral surface of the cylindrical body is taken as a voltage value. The eddy current displacement sensor to detect, and the unit displacement in the radial direction at an arbitrary distance to the peripheral surface of the cylinder when the cylinder is displaced in the radial direction with respect to each eddy current displacement sensor and the output of the corresponding sensor The sensor sensitivity calibration formula registration unit in which the relational expression with the voltage value is registered as the sensor sensitivity calibration formula, and the displacement amount in the cutting line direction of the cylindrical body when the cylinder body is displaced in the cutting line direction with respect to each eddy current displacement sensor. And the output voltage value of the sensor are approximated by a quadratic equation, the sensor characteristic calibration unit in which the quadratic coefficient of the quadratic equation is registered, and the voltage value detected by each eddy current displacement sensor SE Sensor sensitivity calibration formula The sensor sensitivity calibration calculator that calculates the calibrated sensor sensitivity by substituting it in the sensor sensitivity relational expression, the output voltage value of each eddy current displacement sensor, and the calibration by the sensor sensitivity calibration calculator An equation generation unit that generates simultaneous equations that determine the displacement amounts of the cylindrical body in each of the unknown two orthogonal directions using the obtained sensor sensitivity and the quadratic coefficient that is registered in the sensor characteristic calibration unit, and an equation generation unit. And a displacement amount calculating unit that obtains displacement amounts of the cylindrical body in each of the two orthogonal directions by solving the simultaneous equations generated by the unit.

In the axial center displacement measuring device for a cylindrical body according to the invention of claim 2, prior to actual measurement, in the two orthogonal axes (x axis, z axis) in the plane perpendicular to the axial center of the cylindrical body. The installed eddy current sensor detects the distance to the peripheral surface of the cylinder as a voltage value (Vx, Vz), and the cylinder is displaced in the radial direction (x direction, z direction) with respect to each eddy current displacement sensor. At any given distance (x,
z) the unit displacement in the radial direction (ax, az) and the output voltage value (Vx, Vz) of the corresponding sensor (ax = ax)
(Vx), az = az (Vz)) is registered in advance in the sensor sensitivity calibration formula registration section as a sensor sensitivity calibration formula, and the cylindrical body is in the cutting line direction (z direction, x direction) for each eddy current displacement sensor. ) Is obtained by approximating the relationship between the displacement amount d in the cutting line direction of the cylindrical body and the output voltage value (Vx, Vz) of the sensor when displacing to The quadratic coefficient (Cx, Cz) of is registered in the sensor characteristic calibration unit in advance.

In measuring the actual displacement of the cylinder,
Voltage value detected by each eddy current displacement sensor (Vx, V
z) The calibrated sensor sensitivity (ax, az) is calculated by substituting each into the sensor sensitivity calibration formula in the sensor sensitivity calibration calculation unit, and the output voltage value (Vx, Vz of each eddy current displacement sensor is calculated in the equation generation unit. ) And the sensor sensitivity (a
x, az) and the quadratic coefficient (Cx, Cz) registered in the sensor characteristic calibration unit, the displacement amount (x, z) in each of the unknown two orthogonal axes (x axis, z axis) of the cylindrical body. The simultaneous equations of the above equation 4 for determining z) are generated. Then, the displacement amount calculating unit solves this simultaneous equation by the Newton-Raphson method to obtain the displacement amounts (x, z) in the two orthogonal axial directions of the cylindrical body.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a system configuration of an axial center displacement measuring device for a cylindrical body according to a second aspect of the invention, which is almost the same as the conventional example device shown in FIG.
0 has a different internal configuration. Therefore, the same parts as those of the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

Arithmetic processing unit 50 which is a characteristic part of the present invention
Is the radial displacement output sensitivity calibration unit 5 as shown in FIG.
1, a disconnection direction displacement output characteristic calibration unit 52, a sensor sensitivity calculation unit 53, a displacement amount equation generation unit 54, a displacement amount calculation unit 55, and a data storage unit 56.

To the arithmetic processing unit 50, analog output voltages Vx and Vz output from the eddy current displacement sensors 1x and 1z in the x and z directions and amplified by the amplifiers 3x and 3z are A / D converters. 4, A / D converted, sampled at a predetermined cycle, input as digital voltage data Vx (n) and Vz (n), and calculated by the arithmetic processing unit 50 and stored in the data storage unit 56. It is D / A converted by the D / A converter 6 and output to an arbitrary display device 7.

In the radial displacement output sensitivity calibration unit 51 of the arithmetic processing unit 50, the cylindrical body 2 is arranged along each axis in the radial direction (x direction, x,
Cylindrical body 2 from the sensor head when it is displaced in the z direction)
Relational expression (ax = ax (Vx), az) between the unit displacement (ax, az) in the radial direction and the output voltage value (Vx, Vz) of the corresponding sensor at any distance (x, z) to the surface of the = Az (Vz)) is registered in advance as a sensor sensitivity calibration formula.

Further, in the cutting line displacement output characteristic calibration unit 52, the cylindrical body 2 is in the cutting line direction perpendicular to each axis for the eddy current displacement sensors 1x, 1z, that is, the z axis, x.
The relationship between the displacement amount d of the cylindrical body 2 in the cutting line direction (z direction, x direction) and the output voltage value (Vx, Vz) of the sensor when the cylinder body 2 is displaced in the respective directions of the quadratic equation,

(Equation 5) Here, the quadratic coefficient (Cx, Cz) of the quadratic expression, which is obtained by approximating Ax and Az by constants, is registered in advance.

The sensor sensitivity calculation unit 53 is configured to detect the eddy current displacement sensor 1x.x at each sampling timing n when actually measuring the displacement amount of the cylindrical body. By substituting the voltage values (Vx (n), Vz (n)) detected by the respective 1z into the sensor sensitivity calibration formula registered in the radial displacement output sensitivity calibration unit 51, the sensor sensitivity (ax (n), az (n)) is calibrated and output.

The displacement amount equation generator 54 is provided with the sensor sensitivity (ax) calibrated by the sensor sensitivity calibration calculator 53.
(n), az (n)) and the quadratic term coefficients (Cx, Cz) registered in the tangential displacement output characteristic calibration unit 52, and are used as two orthogonal axes (x axis, z axis) of the cylindrical body 2. Simultaneous equations that determine unknown displacements (x (n), z (n)) in each direction,

(Equation 6) Is the part that generates.

The displacement amount calculation unit 55 solves the simultaneous equations of the equation 6 generated by the displacement amount equation generation unit 54 by the Newton-Raphson method, which will be described later.
Displacement of each of the two orthogonal axes (x-axis, z-axis) (x
(n), z (n)).

Next, the operation of the axial displacement measuring device for a cylindrical body having the above construction will be described. Prior to actual measurement, first, the sensor sensitivity calibration formula is registered in the radial displacement sensitivity calibration unit 51.

The procedure for registering this calibration formula is shown in FIG. 3, but the distance between the head portion of the eddy current displacement sensor 1x in the x direction and the surface of the cylindrical body 2 is set to 5 mm, and this is set as the reference position 0.
As the position of mm, the cylindrical body 2 is moved in the x direction in the range of -5 mm to +5 mm in 1 mm steps, and the sensor output voltage at that time
Plot Vx on the graph (step 3a). Next, with respect to the graph of the output voltage of the eddy current displacement sensor 1x-the displacement amount for calibration obtained in step 3a, the voltage is divided by the distance at each measurement point, and the divided value is plotted in the graph. Sensor sensitivity ax [V / mm] at each calibration displacement x [mm]
(Step 3b). Further, as shown in step 3c, each displacement amount for calibration x [mm] in the graph obtained in step 3b is replaced with the corresponding sensor output voltage Vx and plotted.

After that, the graph obtained in step 3c is approximated by a linear expression to obtain the sensor sensitivity with respect to the sensor output voltage Vx.
For ax, the following functional expression of Equation 7 is obtained and registered (steps 3d and 3e).

The above procedure can be carried out separately for the z-direction eddy current displacement sensor 1z, but if the same sensor is used, it is considered that they have substantially the same sensitivity characteristics in order to avoid the complexity of the procedure. , Sensor output voltage
For the sensor sensitivity az with respect to Vz, the following functional expression of Equation 7 is set.

[0031]

[Equation 7] Output voltage Vx, Vz = less than 0.5 V (displacement −5 to +1)
mm): ax (Vx) = az (Vz) = 0.52 [V / mm] Output voltage Vx, Vz = 0.5 V or more (displacement +1 mm or more): ax (Vx) = az (Vz) = − 0.011 × (output Voltage) +0.52 [V /
mm] Next, the quadratic term coefficients Cx and Cz that satisfy the above equation 5 are calculated and registered in the cut line direction displacement output characteristic calibration unit 52. The procedure is shown in FIG. 4, but first, the cylindrical body 2 is set at the reference position (the position from the sensor head to the surface of the cylindrical body 2 is 5 mm away from the eddy current displacement sensor 1x, and Place it on the extension line at the position where the center axis of the cylinder 2 exists, and displace it in the cut line direction (that is, z direction) in the range of -5mm to + 5mm in predetermined increments (for example, 1mm increments), and correspond to the displacement amount d. The sensor output voltage Vx is measured and plotted on a graph (step 4a). Then, with respect to the obtained graph, the relationship between the displacement amount d and the output voltage value Vx of the sensor is approximated by the quadratic equation of the above equation 5, and the quadratic coefficient Cx of the obtained quadratic equation is obtained.
Is stored (steps 4b and 4c). In the equation (5), the constant Ax is the measurement of the reference position, and if the calibration is strictly performed, Ax = 0 and the calculation becomes easy.

Also in the eddy current displacement sensor 1z, the output voltage Vz at each displacement point is measured for the eddy current displacement sensor 1z by displacing the cylindrical body 2 in the cutting line direction, that is, the x direction, and the displacement amount d and the output voltage of the sensor are measured. The relationship with the value Vz is approximated by the quadratic equation of the above-mentioned equation 5, and the obtained quadratic coefficient Cz of the quadratic equation is stored.

When the sensor sensitivity calibration formula and the quadratic coefficient of the sensor output characteristic are registered in this way, the actual measurement is started. This actual measurement is executed according to the procedure shown in FIG. That is, if the axis of the cylindrical body 2 to be measured is displaced in any direction, the eddy current displacement sensors 1x and 1z output the output voltages Vx and Vz corresponding to the displacement components in the x and z directions, respectively. Then, the signals are continuously input to the A / D converter 4 via the amplifiers 3x and 3z.

The A / D converter 4 is an input sensor 1
The output voltages Vx and Vz of x and 1z are A / D converted, sampled at a predetermined cycle, and are digital values Vx (n) and Vz (n) for each sampling timing n.
Input 0 (step 5a).

In the arithmetic processing unit 50, the sensor output voltage value Vx (n), which is input at every sampling timing n,
For each Vz (n), the sensor sensitivity calculation unit 53 uses the sensor sensitivity calibration expressions shown in the above formula 7 registered in the radial displacement output sensitivity calibration unit 51, based on the sensor sensitivity ax (n), az Find (n) (steps 5b, 5
c).

Next, in the displacement amount equation generating unit 54, the quadratic coefficient Cx, Cz registered in the cutting line displacement output characteristic calibrating unit 52, the input output voltages Vx, Vz, and the sensor sensitivity calculating unit 53 Sensor sensitivity calibration values of ax (n), az
(n) is used to generate the simultaneous equations shown in the following equation 8 based on the equation 6 (step 5d).

[0037]

(Equation 8) Here, x (n) and z (n) are unknown values.

Then, in the displacement amount calculating section 55, the simultaneous equations of the equation 8 are unknown values, that is, the displacement amount x (n) in the x direction.
And the displacement amount z (n) in the z direction are solved. The solution of this simultaneous equation is as follows.

By eliminating z (n) in the simultaneous equations of the above equation 8,

[Equation 9] Then, a quartic equation for x (n) is created, and the displacement amount x (n) in the x direction is calculated using the Newton-Raphson method as the root of the equation (9) (step 5e).

The calculation of the displacement amount x (n) in the x direction by the Newton-Raphson method is as follows. That is, the number 10
Put f (x) as shown in the formula,

(Equation 10) On the other hand, the first-order differential function f (x) 'shown in the equation (11) is obtained.

[0041]

[Equation 11] Using these functional expressions, the approximate value x for the true value of the root
_{m + 1} (n) and x _m (n) are sequentially calculated based on the following formula (12).

[0042]

(Equation 12) Then, the difference between the approximate values x _{m + 1} (n) and x _m (n) is

(Equation 13) Here, the newly obtained x _{m + 1} (n) is replaced with x _m (n) until ε becomes a permissible error, and a new x _{m + 1} (n) is obtained by the equation (12). The displacement amount x (n) in the x direction is calculated by repeating until the conditional expression of is satisfied.

In order to calculate the displacement amount z (n) in the z direction, the equation of Vz (n) in the above equation 8 is transformed into the following equation 14 to obtain a known value Vz (n). , Cz, x (n), az (n) are substituted (step 5f).

[0044]

[Equation 14] Thus, the x-direction displacement amount x (n) and the z-direction displacement amount z (n) corresponding to the sampling timing n are stored in the data storage unit 56 (step 5g). Hereinafter, the above steps 5a-
5g is repeatedly calculated at each sampling timing.

For the data thus obtained, D /
It can be converted into analog data through the A converter 6, and the behavior of the axis of the cylindrical body 2 can be displayed in xz coordinates by a display device 7 such as an oscilloscope. In addition, the data registered in the data storage unit 56 can also be subjected to secondary processing according to the purpose of measurement and displayed on the digital display device.

As described above, according to the axial displacement measuring device for a cylindrical body of this embodiment, the eddy current displacement having a diameter considerably larger than 1/4 of the diameter of the cylindrical body to be measured. Even if a sensor is used, the behavior of the axis of the cylindrical body can be continuously and accurately measured. According to the experimental example,
With a drive shaft of φ25 as the cylinder to be measured,
When the behavior of the shaft center in the actual running state of the automobile was measured using an eddy current displacement sensor with a diameter of φ22, the displacement between the displacement set as a reference and the displacement obtained from the output voltage of the eddy current displacement sensor was measured. Difference is about 5-9% (average +3
σ value), which is about 34% (average + 3σ value) difference when measured by a conventional method using an eddy current displacement sensor having the same diameter for a drive shaft having the same shaft diameter. It was proved that the measurement accuracy was improved to 1/3 to 1/7.

In the above embodiment, the drive shaft is the cylindrical body to be measured, the vertical direction is the z direction, and the horizontal horizontal direction of the cross section perpendicular to the axis is the x direction. When it is desired to grasp the behavior of the axis of a cylindrical body (a shaft extending in the left-right direction) such as a propeller shaft, the vertical Z-axis direction and the front-back y-axis direction are used instead of the x-direction in the above embodiment. For the combination of (x, z) in the above embodiment, the measurement may be performed in the x and y axis directions depending on the axial direction of the cylindrical body. ,
By replacing with the combination of (y, z) and (x, y), the same arithmetic expression can be used for measurement.

Further, in the above embodiment, the sensor sensitivity calibration formula is common to ax and az, but it is also possible to separately measure and set these in consideration of the characteristics of each sensor.

In addition, in the above embodiment, the quadratic coefficient of the quadratic equation approximating the sensor output characteristic is obtained separately for Cx and Cz, but it is obtained by actually measuring only one of the x direction and the z direction, and the other By using the same value as, the calibration work in the pre-measurement stage can be simplified.

[0050]

As described above, according to the axial center displacement measuring method of the invention of claim 1, the eddy current displacement having a diameter relatively close to the diameter of the cylinder to be measured. The sensor can be used to accurately measure the axial center behavior of the cylinder, and the eddy current displacement sensor can be used to measure the axial center behavior of the cylinder so that dust, water, mud, oil, etc. can adhere to a harsh environment. It is possible to measure even under the vehicle, and in particular, it is possible to accurately measure the behavior of the drive shaft of an automobile, which could not be easily measured in the actual traveling state in the past, even in the actual traveling state.

According to the axial center displacement measuring device of the invention of claim 2, the measuring method of the invention of claim 1 is realized,
In particular, it can be used to accurately measure the behavior of a drive shaft of an automobile even in an actual traveling state.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of one embodiment of the present invention.

FIG. 2 is a functional block diagram showing an internal configuration of the arithmetic processing unit according to the above embodiment.

FIG. 3 is a flowchart of an output sensitivity calibration procedure of the eddy current displacement sensor according to the above embodiment.

FIG. 4 is a flowchart of an output characteristic calibration procedure of the eddy current displacement sensor in the above embodiment.

FIG. 5 is a flowchart of a procedure for measuring the axial displacement of the cylindrical body according to the above embodiment.

FIG. 6 is a block diagram showing a system configuration of a conventional example.

FIG. 7 is a flowchart of a procedure for measuring an axial displacement of a cylindrical body according to a conventional example.

FIG. 8 is an explanatory diagram showing general error characteristics of an eddy current displacement sensor.

FIG. 9 is a graph showing general output characteristics of an eddy current displacement sensor.

FIG. 10 is a graph showing general sensor sensitivity characteristics of an eddy current displacement sensor.

FIG. 11 is an explanatory view of another conventional example showing a method of measuring the axial center behavior of a cylindrical body using an eddy current displacement sensor.

[Explanation of symbols]

 1x, 1z Eddy current displacement sensor 2 Cylindrical body 3x, 3z Amplifier 4 A / D converter 6 D / A converter 7 Display device 50 Arithmetic processing device 51 Radial displacement output sensitivity calibration unit 52 Cutting line displacement output characteristic calibration unit 53 Sensor sensitivity calculation unit 54 Displacement amount equation generation unit 55 Displacement amount calculation unit 56 Data storage unit

Claims (2)

[Claims] 1. An orthogonal 2 in a plane perpendicular to the axis of the cylindrical body.
A distance to the peripheral surface of the cylindrical body by an eddy current sensor installed in the axis direction (arbitrary two axes selected from three orthogonal axes x, y, z, hereinafter referred to as x, z axes). Is detected as a voltage value (Vx, Vz), and an arbitrary distance to the peripheral surface of the cylindrical body when the cylindrical body is displaced in the radial direction (x direction, z direction) with respect to each of the eddy current displacement sensors. The relational expression (ax = ax (Vx), az = az (Vz)) between the unit displacement amount (ax, az) in the radial direction at (x, z) and the output voltage value (Vx, Vz) of the corresponding sensor It is registered in advance as a sensor sensitivity calibration formula, and the displacement amount d and the sensor in the cutting line direction of the cylindrical body when the cylindrical body is displaced in the cutting line direction (z direction, x direction) with respect to each of the eddy current displacement sensors. Output voltage value (Vx, V
z) is a quadratic equation, and The quadratic coefficient (Cx, Cz) of the quadratic equation obtained by approximating with is registered in advance, and when actually measuring the displacement of the cylindrical body, the voltage value detected by each of the eddy current displacement sensors The calibrated sensor sensitivities (ax, az) are calculated by substituting each of (Vx, Vz) into the sensor sensitivity calibration formula, and the output voltage values (Vx, Vx) of the eddy current displacement sensors are calculated.
z), the sensor sensitivity (ax, az) calibrated by the sensor sensitivity calibration calculation unit, and the quadratic coefficient (Cx, Cz), the two unknown orthogonal axes (x axis, z axis) of the cylindrical body. ) Simultaneous equations that determine the displacement amount (x, z) in each direction, Is generated and the simultaneous equations are solved by the Newton-Raphson method to obtain the displacement amounts (x, z) in the two orthogonal axial directions of the cylindrical body, respectively. 2. An orthogonal 2 in a plane perpendicular to the axis of the cylindrical body.
An eddy current displacement sensor that is installed in the axial direction and detects the distance to the peripheral surface of the cylindrical body as a voltage value, and the cylindrical body when the cylindrical body is displaced in the radial direction with respect to each of the eddy current displacement sensors. A sensor sensitivity calibration expression registration unit in which a relational expression between a unit displacement amount in the radial direction and an output voltage value of a corresponding sensor at an arbitrary distance to the peripheral surface of the sensor sensitivity calibration expression is registered as a sensor sensitivity calibration expression, and the eddy current displacement sensor, respectively. With respect to the quadratic term of the quadratic expression obtained by approximating the relationship between the displacement amount in the tangential direction of the cylinder and the output voltage value of the sensor when the cylinder is displaced in the tangential direction by a quadratic expression By substituting the sensor characteristic calibration unit in which the coefficient is registered and the voltage value detected by each of the eddy current displacement sensors into the relational expression of the sensor sensitivity of the sensor sensitivity calibration formula registration unit, And sensor sensitivity calibration calculation unit for calculating a calibrated sensor sensitivity was, each output voltage value the eddy current displacement sensor, and the sensor sensitivity is calibrated by the sensor sensitivity calibration calculation unit,
An equation generation unit that generates a simultaneous equation that determines the displacement amount of each of the unknown two orthogonal axial directions of the cylindrical body using the quadratic term coefficient registered in the sensor characteristic calibration unit, and the equation generation unit An axial displacement measuring device for a cylindrical body, comprising: a displacement amount calculating section for obtaining displacement amounts in the two orthogonal directions of the cylindrical body by solving the simultaneous equations.