JP2006071557A - Friction testing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a friction testing method and its device for finding an accurate friction coefficient even on a surface under measurement not flat in a direction orthogonal to a relative slip giving direction of a raceway surface, etc. of a ball bearing by decreasing the displacement amount of a spherical body in the longitudinal direction of leaf springs owing to the bending of the leaf springs caused by frictional force without decreasing the distortion amount of the leaf springs caused by the frictional force, in measuring frictional force from the distortion amount of the leaf springs when relative slip motion is given to the spherical body such as a steel ball with the spherical body pressed against a surface under test via the leaf springs. <P>SOLUTION: The spherical body 7b is supported by means of leaf springs 7d and 7e disposed parallel to each other with a prescribed distance left between them in their slipping directions while causing their bend-allowing directions to lie parallel to slipping directions with respect to a surface Wa under test. The use of a pick-up 7 mounted in a rigid body (a part under support) 7a, reduces the longitudinal displacement amount of the leaf springs 7d and 7e due to the bending thereof caused by the frictional force, to enhance positional accuracy of pressing the surface Wa by the spherical body 7b, thereby finding an accurate frictional coefficient, without decreasing the distortion amount of the leaf springs 7d and 7e, and accordingly, without lowering sensitivity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for giving a relative sliding motion between the two in a state in which the sphere is pressed against the surface to be measured, measuring a force acting on the sphere by the slip, and measuring a friction coefficient of the surface to be measured. More specifically, friction effective when the surface to be measured is not flat in a direction perpendicular to the sliding direction with respect to the sphere, such as when measuring the sliding friction coefficient in the circumferential direction of the raceway surface of the ball bearing raceway. The present invention relates to a test method and apparatus.

  Conventionally, a Bowden type tester, a pin-on-disk, or the like is known as a tester for measuring the sliding friction coefficient of the surface of an object (see, for example, Patent Document 1).

The pin-on disk detects the tangential force acting on the pin by pressing a pin-shaped metal against the surface of the disk under test with a predetermined pressure while applying a test object on the disk and applying rotation. Then, using the measured value of the friction force, the sliding friction coefficient of the surface of the test object is obtained from the pressing force of the pin.
On the other hand, the Bowden friction tester gives a relative reciprocating sliding motion between the steel ball and the test object while pressing the steel ball against the surface of the test object under a predetermined pressing force. The force in the sliding motion direction acting on the sphere is detected as a measured value of the frictional force, and the sliding friction coefficient on the surface of the test object is obtained from the pressing force of the steel ball.

  By the way, in rolling bearings such as ball bearings, the rolling elements are basically in rolling contact with the raceways of the inner ring and outer ring, but these may be in sliding contact depending on the use conditions and conditions. Therefore, it is important to know the dynamic sliding friction coefficient of the raceway surface to know the behavior of the rolling bearing.

  In measuring the sliding friction coefficient of the raceway surface of the rolling bearing, the conventional friction tester is naturally used as it is, especially when the surface to be measured is not flat, such as a ball bearing or a spherical roller bearing. This is not possible, and a dedicated device needs to be manufactured.

  As a device for measuring the sliding friction coefficient of the raceway surface of the inner and outer rings of the ball bearing, for example, the inner ring or the outer ring is gripped and rotated, and a sphere such as a steel ball is pressed against the raceway surface, and the sphere is A device that detects a force acting in a tangential direction of an inner ring or an outer ring and generates a frictional force is often used. In such an apparatus, a front view (A) and a front view (A) shown in FIG. 5 according to those used in a Bowden friction tester as a pickup for holding a sphere to be pressed against the raceway surface and detecting a force acting on the sphere are shown. A plan view (B) is used.

That is, it has a structure in which a sphere fixing portion 54 to which a sphere 53 is fixed via a leaf spring 52 is attached to a supported portion 51 that is cantilevered by a load mechanism, and a strain gauge 55 is attached to the leaf spring 52. ing. The supported portion 51 and the sphere fixing portion 54 substantially function as rigid bodies, and only the leaf spring 52 is bent solely by the frictional force acting on the sphere 53. This pickup is supported by the load mechanism so that the surface to be measured moves in the direction indicated by the arrow in FIG. 5B, and accordingly, the frictional force acts on the sphere 53 in the direction indicated by the arrow. As a result, the frictional force acting on the sphere 53 is proportional to the amount of bending of the leaf spring 52, and the amount of distortion of the leaf spring 52 based on the bending is detected by the strain gauge 55 to measure the frictional force. be able to.
JP 2003-136151 A

  For example, when measuring the dynamic sliding friction coefficient of the raceway surface of the inner ring or outer ring of the ball bearing using the pickup illustrated in FIG. 5, the leaf spring 52 is caused by the frictional force F as schematically shown in FIG. The bending force is measured by detecting the amount of bending of the leaf spring 2 due to the bending, and when the amount of bending of the leaf spring 52 increases, the sphere 53 in the longitudinal direction of the leaf spring 52 indicated by Δ in the figure. The displacement amount of the sphere 53 is increased, and the sphere 53 is initially pressed against the bottom of the raceway surface, but the sphere 53 is pressed and the frictional force at the intended position cannot be measured. There's a problem. As a result, when the surface to be measured is not flat in a direction orthogonal to the relative sliding direction with respect to the sphere 53 as in the raceway surface of a ball bearing or a spherical roller bearing, the pressing force by the sphere 53 is perpendicular to the surface to be measured. Therefore, when the friction force measured to obtain the friction coefficient is divided by the pressing force by the sphere 53, strictly speaking, the value is a friction coefficient defined as a value obtained by dividing the friction force by the normal force. Will not be represented.

  If the rigidity of the leaf spring 53 is increased in order to solve such a problem, there is another problem that the amount of bending due to the frictional force is reduced, and consequently the amount of distortion of the leaf spring 53 is reduced and the sensitivity is lowered. Arise.

  The present invention has been made in view of such a situation, and without changing the amount of distortion of the leaf spring due to the frictional force, the change of the pressing position with respect to the measured surface of the sphere due to the deflection of the leaf spring due to the frictional force. And a friction test method capable of obtaining an accurate friction coefficient even on a surface to be measured that is not flat in a direction perpendicular to the relative sliding direction with a sphere, such as a raceway surface of a ball bearing or a spherical roller bearing, and Providing a device is an issue.

  In order to solve the above-mentioned problems, the friction test method of the present invention is to apply a relative sliding motion between the two in a state where the sphere is pressed against the surface to be measured, and measure the force acting on the sphere by the slip. In performing the friction test of the surface to be measured, a friction test method in a case where the surface to be measured is not flat in a direction orthogonal to the sliding direction, the sphere is aligned with the flexible direction in the sliding direction, In addition, a relative sliding motion between the surface to be measured and the sphere is supported by a rigid body via two parallel leaf springs arranged at a predetermined distance in the sliding direction and pressed against the surface to be measured. The amount of strain of each leaf spring when applied is detected by strain detection means attached to each leaf spring, and the frictional force acting on the sphere is measured from the detection result. .

  The friction test apparatus of the present invention is a friction test apparatus for an object having a measurement surface whose axial parallel cross section is not a straight line on the inner periphery or outer periphery of an annular body or the outer periphery of a cylindrical body. A rotary shaft that supports the object to be rotated and a load mechanism that supports the base end side of the pickup with the sphere fixed to the tip side and presses the sphere against the surface to be measured with a constant force. Is a supported part made of a rigid body supported by the load mechanism, a parallel spring made up of two parallel leaf springs each having a base end fixed to the supported part, and a distal end of the parallel spring A sphere fixing portion made of a rigid body fixed to the sphere, a sphere fixed to the sphere fixing portion, and a strain detection sensor attached to each of the leaf springs. The pickup is pressed against the surface to be measured. In the state Serial characterized by the direction connecting the leaf spring is supported by the loading mechanism along a tangential direction of the rotation of the object by the rotating shaft (Claim 2).

The present invention intends to solve the problem by using a parallel spring as a leaf spring interposed between a supported portion supported by a load mechanism and a sphere pressed against a surface to be measured.
That is, comparing the case of using a single conventional leaf spring and the case of changing this to a parallel spring, the thickness of each leaf spring constituting the parallel spring is the same as the case of using a single leaf spring alone. By setting the thickness to ½, the amount of displacement of the leaf spring in the longitudinal direction due to bending can be reduced to about ½ without reducing the amount of distortion when the same force is applied to the sphere. It became clear by the simulation of the inventors. Therefore, the displacement of the pressing position in the longitudinal direction due to the bending of the leaf spring can be reduced without reducing the amount of distortion of the leaf spring, and thus without lowering the sensitivity. The coefficient of friction can be measured.

  According to the present invention, it is possible to reduce the displacement of the sphere in the longitudinal direction of the plate spring due to the bending of the leaf spring without reducing the amount of distortion of the leaf spring due to the frictional force acting on the sphere, and the friction force The accuracy of the pressed position of the surface to be measured by the sphere is improved without reducing the measurement sensitivity, and the friction coefficient of the surface to be measured which is not flat in the direction perpendicular to the relative sliding direction, such as the raceway surface of a ball bearing or spherical roller bearing, is improved. This makes it possible to obtain more accurately than in the past.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a configuration of a friction test apparatus according to an embodiment of the present invention, and shows an example in which a friction test of a raceway surface Wa is performed using an outer ring of a ball bearing as a test object W.

  A rotating shaft 2 is provided on the table 1, and a housing 2 a of the rotating shaft 2 and a motor 3 as a driving source can be moved in the x, y, and z axis directions orthogonal to each other by a moving mechanism 4. . Then, the device under test W is attached to the tip of the rotating shaft 2 via the attachment 5.

  A load mechanism 6 is also provided on the table 1. The load mechanism 6 has an intermediate portion of a lever 6c fixed to a shaft 6b rotatably supported by a support base 6a, a pickup 7 is mounted on one end side of the lever 6c, and a balance weight on the other end side. 6d is attached. An L-shaped arm 6e is fixed to the shaft 6b, and a weight 6f is suspended from the tip of the arm 6e so as to be positioned on a vertical line passing through the center of a steel ball 7b of the pickup 7 shown below. Has been lowered. With this configuration, a vertically downward force having a magnitude corresponding to the weight of the weight 6f acts on the steel ball 7b of the pickup 7.

  As shown in FIG. 2 (A), the pickup 7 includes a supported portion 7a that is cantilevered by the lever 6c of the load mechanism 6 and a steel ball 7b. It has a structure in which a steel ball fixing portion 7c to be fixed is connected by a parallel spring composed of two parallel leaf springs 7d and 7e, and strain gauges 7f and 7g are attached to the leaf springs 7d and 7e. ing. The lever 6c of the load mechanism 6 is attached so that the steel ball 7b faces vertically downward, and thus the separation direction between the two leaf springs 7d and 7e constituting the parallel spring is along the horizontal direction.

  In the test, as shown in FIG. 3, the steel ball 7 b is positioned by the operation of the moving mechanism 4 so as to abut against and press against the bottom of the raceway surface Wa of the outer ring of the ball bearing which is the test object W. Thus, the rotating shaft 2 is driven to rotate the device under test W. As a result, the steel ball 7b is pressed against the raceway surface Wa with a force having a magnitude corresponding to the weight 6f, and a sliding motion is given between them.

  By such a test, a frictional force is generated between the steel ball 7b and the raceway surface Wa, and the frictional force acts on the steel ball 7b to bend the parallel spring composed of the leaf springs 7d and 7e. The strain amount of each leaf spring 7d, 7e is detected by the strain gauges 7f, 7g attached thereto, and the magnitude of the frictional force is obtained from the detected value.

  Here, the plate spring is bent by the frictional force acting on the steel ball, and the point of measuring the frictional force from the amount of distortion of the plate spring due to the bending is the same as the conventional pickup shown in FIG. As shown below, due to the difference in the deformation mode of the leaf spring, the amount of displacement of the leaf spring in the longitudinal direction due to bending should be greatly reduced while equalizing the amount of strain of the leaf spring caused by the same frictional force. Can do.

  That is, in the pickup 7 according to the embodiment of the present invention using a parallel spring, as shown in FIG. 4, it is deformed as shown in FIG. The mode is different from the modification shown in FIG.

  As a result of analysis using the finite element method, the plate springs 7d and 7e in the embodiment of the present invention are compared with the structure using the single plate spring 52 shown in FIG. The length and the length of the spring 52 are the same except that the thickness is 0.4 times that of the spring 52. When the same force F is applied to the steel ball, the amount of strain is equal and the longitudinal direction of the leaf spring due to bending It has been found that the displacement amount δ decreases to 0.54 times the displacement amount Δ in the same direction in FIG. Specifically, in the pickup 7 using the parallel spring in the embodiment of the present invention and the conventional pickup shown in FIG. 5, each leaf spring has a thickness of 1 mm for the former and 0.4 mm for the latter. When the load is applied to the steel ball in the same direction as the direction of the frictional force during the test so that the length is 35 mm and the generated strain amount of each leaf spring is both 406 μSt, the conventional pickup uses steel. Whereas the displacement amount δ of the sphere in the longitudinal direction of the leaf spring was 0.0118 mm, in the pickup 7 according to the embodiment of the present invention, the displacement amount δ of the steel ball 7c in the longitudinal direction of the leaf spring was 0.00636 mm. Met.

  Therefore, according to the embodiment of the present invention, even when the amount of distortion of the leaf springs is the same, the displacement amount of the pressing position with respect to the measured surface Wa due to the bending of the leaf springs 7d and 7e is used in the conventional pickup shown in FIG. It is possible to reduce to about half compared to As a result, the value obtained by dividing the frictional force by the pressing force of the surface to be measured Wa by the steel ball 7b represents a more accurate friction coefficient than the conventional one.

  In the above example, an example in which the dynamic sliding friction coefficient of the raceway surface is obtained with the outer ring of the ball bearing as a test object has been described. The same effects as described above can be obtained when measuring the raceway surface of the outer ring and also the surface to be measured which is not flat in the direction orthogonal to the slip application direction when measuring the frictional force.

It is a schematic diagram which shows the structure of the friction test apparatus of embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the pick-up 7 used by embodiment of this invention, (A) is a front view, (B) is the top view. It is an enlarged view which shows the press state with respect to the to-be-measured surface Wa of the steel ball 7b of the pick-up 7 at the time of a test. It is a schematic diagram showing the deformation | transformation state by the frictional force of the pick-up 7 in embodiment of this invention. It is a figure which shows the structural example of the pickup used with the conventional friction test apparatus, (A) is a front view, (B) is the top view. It is a schematic diagram showing the deformation | transformation state by the frictional force of the pickup of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Table 2 Rotating shaft 3 Motor 4 Moving mechanism 5 Attachment 6 Load mechanism 6a Support stand 6b Shaft 6c Lever 6d Balance weight 6e Arm 6f Weight 7 Pickup 7a Supported part 7b Steel ball 7c Steel ball fixed part 7d, 7e Plate spring 7f , 7g Strain gauge W DUT (ball bearing outer ring)
Wa track surface

Claims (2)

When a sphere is pressed against the surface to be measured, a relative sliding motion is imparted between the two, and the force acting on the sphere is measured by the slip to perform a friction test on the surface to be measured. A friction test method in the case where the surface is not flat in a direction orthogonal to the sliding direction,
The spherical body is supported by a rigid body through two leaf springs parallel to each other along a flexible direction in the sliding direction and spaced apart by a predetermined distance in the sliding direction. The amount of strain of each leaf spring when it is pressed and a relative sliding motion is given between the surface to be measured and the sphere is detected by the strain detection means attached to each leaf spring, and acts on the sphere from the detection result. A friction test method characterized by measuring a friction force. A friction test apparatus for an object having a measurement surface whose axial parallel cross section is not a straight line on the inner periphery or outer periphery of an annular body, or the outer periphery of a cylindrical body,
A rotating shaft that supports and rotates the object to be used for the test, and a load mechanism that supports the base end side of the pickup with the sphere fixed to the tip side and presses the sphere against the surface to be measured with a certain force. The pickup includes a supported portion made of a rigid body supported by the load mechanism, a parallel spring made up of two parallel leaf springs each having a base end fixed to the support portion, and the parallel spring A sphere fixing portion made of a rigid body fixed to the tip of the sphere, a sphere fixed to the sphere fixing portion, and a strain detection sensor mounted on each of the leaf springs. A friction test apparatus, wherein the load mechanism supports the leaf springs so that a direction connecting the leaf springs is along a tangential direction of rotation of the object by the rotation shaft in a state of being pressed against a surface.

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