JP2003329513A - Measuring method for propagation speed of ultrasonic waves in inner ring of cylindrical roller bearing and measuring method for degree of fatigue - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method for a propagation speed of ultrasonic waves in an inner ring of a cylindrical roller bearing, in which it is not required to replace a transmitting sensor and a receiving sensor even when a diameter of the inner ring is changed and which reduces a man-hour and costs. <P>SOLUTION: In the measuring method for the propagation speed of the ultrasonic waves in the inner ring of the cylindrical roller bearing, the transmitting sensor 1 and the receiving sensor 2 are brought into line contact with the inner ring 10 so as to measure the propagation speed of the ultrasonic waves, and the transmitting sensor 1 and the receiving sensor 2 can be used for the inner ring 10 in different diameters. Consequently, it is not required to prepare a plurality of kinds of transmitting sensors 1 and receiving sensors 2 according to the diameter of the inner ring 10, and the measuring method reduces a measuring man-hour and measuring costs. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave propagation velocity measuring method for propagating an ultrasonic wave to an inner ring of a cylindrical roller bearing and measuring its propagation velocity. Further, based on the measured propagation velocity, the cylinder The present invention relates to a fatigue degree measuring method for measuring the fatigue degree of an inner ring of a roller bearing.

[0002]

2. Description of the Related Art Conventionally, when measuring characteristics (for example, hardness) of an inner ring of a cylindrical roller bearing, the sensor surfaces (mounting surfaces) of ultrasonic transmission and reception sensors are closely attached along the raceway surface of the inner ring. With such a surface curvature, the characteristics of the inner ring have been measured based on the velocity of the ultrasonic waves propagated from the transmission sensor to the inner ring.

[0003]

Therefore, the transmission sensor and the reception sensor cannot be applied to a plurality of types of inner rings having different diameters, and the transmission sensor and the reception sensor are prepared only for the types of inner rings having different diameters. Therefore, the measurement man-hour and the measurement cost are increased.

Therefore, an object of the present invention is to measure the ultrasonic propagation velocity of the inner ring of a cylindrical roller bearing, which does not require replacement of the transmitting sensor and the receiving sensor even if the diameter of the inner ring changes, and can reduce the measurement man-hour and the measurement cost. And to provide a method for measuring the degree of fatigue.

[0005]

In order to achieve the above object, the method for measuring the ultrasonic propagation velocity of the inner ring of a cylindrical roller bearing according to the invention of claim 1 transmits ultrasonic waves to the raceway of the inner ring of the cylindrical roller bearing. A method for measuring the propagation velocity of the ultrasonic wave propagating on the orbital plane, using a transmitting sensor and a receiving sensor for receiving the ultrasonic wave propagating on the orbital plane,
A contact line in which the transmission sensor and the reception sensor are in line contact with the raceway surface of the inner ring by axial lines at predetermined intervals in the circumferential direction, and the transmission sensor is in line contact with the raceway surface. And a straight line connecting the center of the inner ring and a straight line connecting the center of the inner ring and the contact line where the receiving sensor is in line contact with the raceway surface are 2α, and the radius of the raceway surface is r. (mm) and the wall thickness of the inner ring is T (mm), the transmission sensor and the reception sensor are arranged so as to satisfy the following expression r (1-cosα) <T / 2. In the invention of claim 1, the transmission sensor and the reception sensor are brought into line contact with the raceway surface of the inner ring by a line in the axial direction, and the ultrasonic wave transmitted by the transmission sensor to the raceway surface of the inner ring is transmitted. The signal is received by the reception sensor. This ultrasonic wave from the propagation time that this ultrasonic wave propagates from the transmission sensor to the reception sensor and the distance between the line contact position of the transmission sensor and the line contact position of the reception sensor on the orbital surface (inter-sensor propagation distance) The propagation speed of is obtained. Based on this propagation velocity, it is possible to measure the characteristics such as the degree of surface deterioration, hardness, and fatigue of the inner ring.

According to the first aspect of the present invention, since the transmission sensor and the reception sensor are in line contact with the raceway surface of the inner ring to measure the propagation velocity of ultrasonic waves, the transmission sensor and the reception sensor are inner rings having different diameters. It can be used. Therefore, it is not necessary to prepare a plurality of types of transmission sensors and reception sensors according to the diameter of the inner ring, and the number of measurement steps and the measurement cost can be reduced.

According to the first aspect of the invention, the above formula, r
By arranging the transmission sensor and the reception sensor so as to satisfy (1-cos α) <T / 2, the ultrasonic waves propagating on the raceway surface of the inner ring interfere with the reflected waves of the ultrasonic waves reflected on the inner diameter surface of the inner ring. Can be suppressed.

According to a second aspect of the present invention, there is provided a method for measuring an ultrasonic wave propagation velocity of an inner ring of a cylindrical roller bearing, wherein the ultrasonic wave is transmitted to the raceway surface of the inner ring of the cylindrical roller bearing, and the ultrasonic wave is propagated through the raceway surface. Using a reception sensor that receives ultrasonic waves,
A method for measuring the propagation velocity of the ultrasonic wave propagating on the orbital surface, wherein the transmitting sensor and the receiving sensor are lined in the axial direction at a predetermined interval in the circumferential direction with respect to the orbital surface of the inner ring. And a line in which the transmitting sensor is in line contact with the raceway of the inner ring and a line in which the receiving sensor is in line contact with the raceway of the inner ring are orthogonal straight lines and this orthogonal straight line It is characterized in that the distance between the parallel tangents to the raceway surface is set to less than half the radial thickness of the inner ring.

According to the second aspect of the present invention, the transmission sensor and the reception sensor are brought into line contact with the raceway surface of the inner ring by an axial line, and the transmission sensor transmits to the raceway surface of the inner ring. Ultrasonic waves are received by the reception sensor. The ultrasonic wave from the propagation time that this ultrasonic wave propagates from the transmission sensor to the reception sensor and the distance between the line contact position of the transmission sensor and the line contact position of the reception sensor on the orbital surface (inter-sensor propagation distance) The propagation speed of is obtained. Based on this propagation velocity, it is possible to measure the characteristics such as the degree of surface deterioration, hardness, and fatigue of the inner ring. Further, in the invention of claim 2, an orthogonal straight line orthogonal to a line in which the transmission sensor is in line contact with a line in which the reception sensor is in line contact, and a raceway surface of the inner ring parallel to the orthogonal straight line. The distance from the tangent line was set to less than half the radial thickness of the inner ring. With this setting, it is possible to suppress the interference of the ultrasonic waves propagating on the raceway surface of the inner ring with the reflected waves of the ultrasonic waves reflected on the inner diameter surface of the inner ring. Therefore, the measurement sensitivity of the ultrasonic wave propagating on the orbital surface can be improved, and the measurement accuracy of the propagation velocity can be improved.
Therefore, by using this method, the characteristics of the inner ring (surface deterioration degree, hardness, fatigue degree, etc.) can be accurately measured.

Further, the invention of claim 3 is the ultrasonic wave propagation velocity measuring method according to claim 1 or 2, wherein the transmitting sensor contacts an effective portion effective for transmitting ultrasonic waves with the raceway surface of the inner ring. The receiving sensor is characterized in that an effective portion effective for receiving ultrasonic waves is brought into contact with the raceway surface of the inner ring.

According to the third aspect of the present invention, the transmission sensor brings an effective portion effective for transmitting ultrasonic waves into contact with the raceway surface of the inner ring, and the reception sensor has an effective portion effective for receiving ultrasonic waves. It is in contact with the raceway surface of the inner ring. Therefore, the transmitting sensor can surely propagate the ultrasonic wave from the effective portion to the orbital surface, and the receiving sensor can surely detect the ultrasonic wave at the effective portion.

Further, the invention of claim 4 is the ultrasonic wave propagation velocity measuring method according to claim 1 or 2, wherein the facing surface of the transmission sensor facing the raceway surface of the inner ring is a flat shape, and the inner ring is It is characterized in that the facing surface of the above-mentioned reception sensor facing the track surface of is a planar shape.

In the invention of claim 4, the facing surface of the transmitting sensor facing the raceway surface of the inner ring is flat, and the facing surface of the receiving sensor facing the raceway surface of the inner ring is flat. . Therefore, the shapes of the facing surfaces of the transmitting sensor and the receiving sensor can be particularly simplified, and the sensor cost can be reduced.

According to a fifth aspect of the present invention, there is provided a fatigue measuring method according to any one of the first to fourth aspects, in which the ultrasonic wave propagating through the inner ring of the cylindrical roller bearing is propagated. The speed is measured, and the fatigue degree of the inner ring of the cylindrical roller bearing is measured based on the measured propagation speed.

According to the fifth aspect of the present invention, the ultrasonic wave propagation velocity measuring method can accurately and easily measure the propagation velocity of the ultrasonic wave propagating on the raceway surface of the inner ring, and based on the accurately measured propagation velocity. In addition, the degree of fatigue of the inner ring can be measured accurately and easily.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings.

With reference to FIGS. 1, 2 and 3, an embodiment of a method for measuring the degree of fatigue of an inner ring of a cylindrical roller bearing of the present invention will be described.

As shown in FIG. 1, in the fatigue measuring method of this embodiment, the raceway surface 10A of the inner ring 10 of the cylindrical roller bearing is used.
The transmitting sensor 1 and the receiving sensor 2 are brought into line contact with each other. That is, the transmission sensor 1 is in line contact with the raceway surface 10A at the axial contact line 3, and the reception sensor 2 is in line contact with the raceway surface 10A at the axial contact line 5.

Further, as shown in FIGS. 1 and 2, an orthogonal straight line 6 which is orthogonal to the contact line 3 of the transmission sensor 1 and the contact line 5 of the reception sensor 2 and the raceway surface parallel to the orthogonal straight line 6. The distance H (mm) between the tangential line 7 of 10A was set to 0.4 times the radial thickness T (mm) of the inner ring 10. Further, the facing surface 1A of the transmitting sensor 1 and the facing surface 2A of the receiving sensor 2 facing the track surface 10A have a planar shape.

Further, the transmission sensor 1 has its facing surface 1A.
Of the effective part 11 effective for transmitting ultrasonic waves in the orbital surface 1
It is in contact with 0A. Further, the reception sensor 2 brings an effective portion 12 of the facing surface 2A effective for receiving ultrasonic waves into contact with the track surface 10A.

Next, referring to FIG. 3, the transmission sensor 1
The structure of is explained. This transmission sensor 1 has an outer resin portion 1
A piezoelectric element 15 is embedded in the interior of the piezoelectric element 4, and a vibrating surface 15A of the piezoelectric element 15 is inclined by an angle β (degrees) with respect to the facing surface 1A. An extension line L1 extending from both ends of the vibrating surface 15A in a direction orthogonal to the vibrating surface 15A,
A region R1 inside the two points P1 and P2 where L2 intersects the facing surface 1A by a predetermined dimension becomes the effective portion 11.
As shown in FIG. 3, by vibrating the vibrating surface 15A of the piezoelectric element 15 with respect to the facing surface 1A, ultrasonic waves from the vibrating surface 15A propagate from the contact line 3 of the effective portion 11 along the track surface 10A. Shear horizontal wave (SH wave (Shear Horizontal W
ave)) can be generated efficiently.

As a more specific example, as shown in FIG. 3, the dimension between the end wall 1B of the transmission sensor 1 and the piezoelectric element 15 is Da (mm), and the piezoelectric element in the direction parallel to the facing surface 1A is used. The dimension of the element 15 is Db (mm), and the dimension between the facing surface 1A and the piezoelectric element 15 is Dc. Further, the dimension between the end wall 1B and the point P2 is set to Dm (mm), and the end wall 1B
The dimension between the point P1 and the point P1 is Dn (mm). At this time,
The dimension X1 (mm) from the end wall 1B to one end 11A of the effective portion 11 and the dimension X2 (mm) from the end wall 1B to the other end 11B of the effective portion 11 are calculated by the following equation (1) and Use the value calculated in (2). In the following, the dimension unit system is (mm) and the angle unit system is (degrees).

X1 = Dm + 1 = Da− (Dc + Db · tanβ) tanβ + 1 (1) X2 = Dn−1 = (Da + Db) −Dc · tanβ−1 (2) That is, in this example, the vibrating surface of the piezoelectric element 15 is used. A region R1 which is inside by 1 mm from the region R0 in which 15A is projected on the facing surface 1A is defined as an effective portion 11, and this effective portion 11 is brought into line contact with the raceway surface 10A of the inner ring 10.

Referring to FIG. 2, the dimension X0 between the end wall 1B and the contact line 3 where the facing surface 1A of the transmission sensor 1 is in line contact with the raceway surface 10A is set to X1≤X0≤X2. By setting, the effective portion 11 of the facing surface 1A of the transmission sensor 1
Can be brought into line contact with the raceway surface 10A. This dimension X0 is called the contact position X0.

Further, as shown in FIG. 2, a straight line L connecting the contact line 3 of the transmission sensor 1 and the center P0 of the raceway surface 10A.
The angle that r extends from the center P0 and the center line Lc orthogonal to the orthogonal straight line 6 is α. The straight line Lr and
Tangent line Ls of the raceway surface 10A at the contact position X0
And a right-angled triangle formed by the center line Lc and the angle α
The complementary angle of (θ / 2) is (θ / 2), and as shown in FIG. 1, the angle θ that is twice this angle (θ / 2) is called the sensor angle. The distance W between the line of intersection La between the facing surface 1A of the transmission sensor 1 and the end wall 1B and the line of intersection Lb between the facing surface 2A of the reception sensor 2 and the end wall 2B is called the sensor interval.

The distance Dd between the contact line 3 and the contact line 5 on the track surface 10A is called the propagation distance. This propagation distance D
d is calculated by the following equation (3).

Dd = α · π · r / 90 (3) In the formula (3), r is the radius of the orbital surface 10A, and π is the circular constant.

In the method of measuring the degree of fatigue of the inner ring 10 of this embodiment, the effective portion 11 is vibrated by driving the piezoelectric element 15 of the transmission sensor 1 to vibrate the vibrating surface 15A, and the contact line 3 to the raceway surface. Propagate ultrasonic waves to 10A.
This ultrasonic wave is a transverse wave S traveling along the orbital surface 10A and having an amplitude parallel to the orbital surface 10A.
It is an H wave.

When the SH wave propagates on the orbital surface 10A and reaches the contact line 5 of the effective portion 12 of the reception sensor 2, the reception sensor 2 outputs a detection signal indicating that the SH wave is detected. From the time Tt from when the piezoelectric element 15 of the transmission sensor 1 is driven to when the reception sensor 2 outputs a detection signal and the distance Dd on the track surface 10A from the contact line 3 to the contact line 5 to the SH The wave propagation velocity V can be calculated. That is, V = Dd / Tt (mm /
Seconds). Based on this propagation velocity V, the degree of fatigue of the inner ring 10 can be measured. For example, as the fatigue of the inner ring 10 progresses, the propagation speed V of the SH wave decreases.

According to this embodiment, the transmitting sensor 1 and the receiving sensor 2 are brought into line contact with the inner ring 10 to generate S as an ultrasonic wave.
Since the propagation velocity of the H wave is measured, the transmission sensor 1 and the reception sensor 2 can be used for inner rings having different diameters. Therefore, it is not necessary to prepare a plurality of types of transmission sensors and reception sensors according to the diameter of the inner ring 10, and the number of measurement steps and the measurement cost can be reduced.

Further, in this embodiment, an orthogonal straight line 6 orthogonal to the contact line 3 with which the transmission sensor 1 is in line contact with the contact line 5 with which the reception sensor 2 is in line contact, and this orthogonal straight line 6
The distance H between the parallel tangent line 7 and the parallel tangent line 7 is set to ⅕ which is less than ½ of the radial thickness T of the inner ring 10. With this setting, the SH propagating on the raceway surface 10A of the inner ring 10
It is possible to suppress the interference of the reflected waves of the ultrasonic waves reflected by the inner diameter surface 10B of the inner ring 10 with the waves. Therefore, the measurement sensitivity of the SH wave propagating on the track surface 10A can be improved, the measurement accuracy of the propagation velocity can be improved, and the fatigue level can be accurately measured.

Further, in this embodiment, the transmission sensor 1
The effective portion 11 effective for transmitting ultrasonic waves is in contact with the raceway surface 10A of the inner ring 10, and the reception sensor 2 is contacting the effective portion 12 effective for receiving ultrasonic waves with the raceway surface 10A of the inner ring 10. Therefore, the transmitting sensor 1 has its effective part 1
The ultrasonic wave can be reliably propagated from 1 to the orbital surface 10A, and the reception sensor 2 can reliably detect the ultrasonic wave at the effective portion 12 thereof.

Further, in this embodiment, the facing surface 1A of the transmitting sensor 1 facing the raceway surface 10A of the inner ring 10 is flat, and the facing surface 2A of the receiving sensor 2 facing the raceway surface 10A of the inner ring 10 is flat. The shape. Therefore,
The shapes of the facing surfaces 2A of the transmission sensor 1 and the reception sensor 2 can be particularly simplified, and the sensor cost can be reduced.

Further, referring to FIG. 2, the value (rsinα-W / 2) obtained by subtracting one half of the sensor interval W from the value rsinα obtained by multiplying the radius r of the track surface 10A by sinα is the contact position X.
It can be seen that it is equal to 0 × cos α. That is, the following equation (4)
Is established.

X0 = (rsinα−W / 2) / cosα (4) where angle α = 90 ° − (θ / 2), and θ is the sensor angle.

In this equation (4), the radius r = 19.25
FIG. 4 shows an example of the relationship among the sensor angle θ, the sensor interval W, and the contact position X0 when the distance is mm. In FIG. 4, X1 and X2 indicate the positions of both ends of the effective portion 11. Therefore, referring to FIG. 4, the sensor interval W is set so that the contact position X0 is between X1 and X2 (effective portion).
And the sensor angle θ can be easily set.

Further, referring to FIG. 2, it can be seen that the distance H is a value obtained by subtracting (rcosα) from the radius r of the track surface 10A. This angle α is half of the angle 2α formed by the straight line Lr connecting the contact line 3 and the center P0 and the straight line Lq connecting the contact line 5 and the center P0. That is, H = r
(1-cosα) (5). In this embodiment, the formula
The distance H calculated in (5) was set to 0.4 times the wall thickness T of the inner ring 10.

In FIG. 5, at a radius r = 19.25 (mm), the sensor angle θ (= 2 (90 ° −
The relationship between α)) and the distance H is shown. In FIG. 5, the sensor angle θ
Is 126 ° or more, the distance H is the wall thickness T (= 4.
It becomes 1/2 or less of 25), the influence of the reflected wave can be suppressed, and the SH wave can be accurately detected. On the other hand, when the sensor angle θ is less than 126 °, the distance H exceeds ½ of the wall thickness T, so that the influence of the reflected wave cannot be ignored and the SH wave cannot be accurately detected.

In the above embodiment, the fatigue level of the inner ring was measured by the ultrasonic propagation velocity measuring method of the present invention. However, the ultrasonic propagation velocity measuring method of the inner ring of the present invention is effective for the surface deterioration and hardening of the inner ring. It is also applicable to evaluation.

[0040]

As is apparent from the above, claims 1, 2
In the method of measuring the ultrasonic wave propagation velocity of the inner ring of the cylindrical roller bearing according to the invention, the transmitting sensor and the receiving sensor are brought into line contact with the inner ring to measure the ultrasonic wave propagation velocity. Therefore, the transmitting sensor and the receiving sensor have inner diameters different from each other. Can be used for. Therefore, it is not necessary to prepare a plurality of types of transmission sensors and reception sensors according to the diameter of the inner ring, and the number of measurement steps and the measurement cost can be reduced.

According to the invention of claim 1, r (1-cos
The transmitting sensor and the receiving sensor are arranged so as to satisfy α) <T / 2. Further, in the invention of claim 2, a distance between a line orthogonal to the line in which the transmission sensor is in line contact with a line in which the reception sensor is in line contact and a tangent line parallel to the orthogonal line. Was set to less than half the radial thickness of the inner ring. With this setting, it is possible to suppress the interference of the ultrasonic waves propagating on the raceway surface of the inner ring with the reflected waves of the ultrasonic waves reflected on the inner diameter surface of the inner ring. Therefore, the measurement sensitivity of the ultrasonic wave propagating on the orbital surface can be improved, and the measurement accuracy of the propagation velocity can be improved.

In the invention of claim 3, the transmitting sensor brings an effective portion effective for transmitting ultrasonic waves into contact with the raceway surface of the inner ring, and the receiving sensor has an effective portion effective for receiving ultrasonic waves. Is in contact with the raceway surface of the inner ring. Therefore, the transmitting sensor can surely propagate the ultrasonic wave from the effective portion to the orbital surface, and the receiving sensor can surely detect the ultrasonic wave at the effective portion.

Further, in the invention of claim 4, the facing surface of the transmitting sensor facing the raceway surface of the inner ring is flat, and the facing surface of the receiving sensor facing the raceway surface of the inner ring is flat. is there. Therefore, the shapes of the facing surfaces of the transmitting sensor and the receiving sensor can be particularly simplified to reduce the sensor cost.

Further, in the fatigue degree measuring method according to the fifth aspect of the present invention, it is possible to accurately measure the propagation velocity of the ultrasonic wave propagating on the raceway surface of the inner ring by the above ultrasonic propagation velocity measuring method. The fatigue of the inner ring can be accurately measured based on the propagation velocity.

[Brief description of drawings]

FIG. 1 is a layout diagram showing a layout of an inner ring, a transmission sensor, and a reception sensor in an embodiment of a method for measuring a fatigue degree of an inner ring of a cylindrical roller bearing of the present invention.

FIG. 2 is an enlarged view of a main part of the above layout diagram.

FIG. 3 is a schematic diagram showing a structure of a main part of the transmission sensor.

FIG. 4 is a graph showing an example of a relationship between a contact position X0 of a transmission sensor, a sensor interval W, and a sensor angle θ in the above embodiment.

FIG. 5 is a sensor angle θ and a distance H in the above embodiment.
It is a graph which shows the relationship with.

[Explanation of symbols]

1 ... Transmitting sensor, 1A ... Opposing surface, 1B ... End wall, 2 ... Receiving sensor, 2A ... Opposing surface, 3,5 ... Contact line, 6 ... Orthogonal straight line, 7 ... Tangent line, 10 ... Inner ring, 10A ... Raceway surface, 11,1
2 ... Effective part, 14 ... Outer side resin part, 15 ... Piezoelectric element, 1
5A ... vibrating surface, β ... angle, P1, P2 ... point, T ... wall thickness,
X0 ... contact position, W ... sensor interval.

Continued front page    F-term (reference) 2G024 AC01 BA12 BA21 CA13 DA09                       FA02                 2G047 AB01 AC08 BA01 BB02 BC02                       BC11 EA12 EA16 GA03                 2G064 AA17 AB05 AB13 BA28 DD23                 3J101 AA13 AA52 AA62 BA77 FA24                       FA26

Claims (5)

[Claims] 1. An ultrasonic wave transmits the ultrasonic wave to the raceway surface of an inner ring of a cylindrical roller bearing, and a receiving sensor which receives the ultrasonic wave propagating on the raceway surface is used. A method of measuring a propagation velocity of propagation, wherein the transmitting sensor and the receiving sensor are brought into line contact with an orbital surface of the inner ring by axial lines at predetermined intervals in a circumferential direction, and the transmitting sensor Is formed by a straight line connecting the contact line in line contact with the raceway surface and the center of the inner ring, and a straight line connecting the contact line in which the receiving sensor is in line contact with the raceway surface and the center of the inner ring The angle is 2α and the radius of the above raceway surface is r
(mm) and the wall thickness of the inner ring is T (mm), the cylinder is characterized in that the transmission sensor and the reception sensor are arranged so as to satisfy the following expression r (1-cosα) <T / 2. Measuring method of ultrasonic wave propagation velocity of inner ring of roller bearing. 2. The ultrasonic wave is transmitted through the raceway surface of an inner ring of a cylindrical roller bearing by using a transmitting sensor that transmits the ultrasonic wave and a receiving sensor that receives the ultrasonic wave that propagates through the raceway surface. A method of measuring a propagation velocity of propagation, wherein the transmitting sensor and the receiving sensor are brought into line contact with an orbital surface of the inner ring by axial lines at predetermined intervals in a circumferential direction, and the transmitting sensor Is a line that is in line contact with the raceway of the inner ring and a line that is orthogonal to the line that the receiving sensor is in line contact with the raceway of the inner ring, and a tangent line of the raceway that is parallel to this line. The distance between the inner ring and the inner ring is set to be less than half the radial thickness of the inner ring. 3. The ultrasonic propagation velocity measuring method according to claim 1 or 2, wherein the transmitting sensor brings an effective portion effective for transmitting ultrasonic waves into contact with a raceway surface of the inner ring, and the receiving sensor comprises: An ultrasonic propagation velocity measuring method for an inner ring of a cylindrical roller bearing, characterized in that an effective portion effective for receiving ultrasonic waves is brought into contact with the raceway surface of the inner ring. 4. The ultrasonic propagation velocity measuring method according to claim 1 or 2, wherein the facing surface of the transmission sensor facing the raceway surface of the inner ring has a planar shape, and the facing surface faces the raceway surface of the inner ring. A method for measuring an ultrasonic wave propagation velocity of an inner ring of a cylindrical roller bearing, characterized in that the opposing surface of the reception sensor is flat. 5. The ultrasonic propagation velocity measuring method according to claim 1, the propagation velocity of ultrasonic waves propagating through the inner ring of the cylindrical roller bearing is measured, and the measured propagation velocity is based on the measured propagation velocity. Furthermore, a fatigue degree measuring method characterized by measuring the fatigue degree of the inner ring of the cylindrical roller bearing.