JP2008267997A - Frictional force measurement method and frictional force measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional force measurement method and a frictional force measuring device capable of more accurately measuring the static frictional force, maximum static frictional force and dynamic frictional force. <P>SOLUTION: The frictional force measuring method for measuring frictional force between a roller 10 and paper 20 in a mutual contact state by moving the paper 20 at constant speed, while keeping the contact state in the fixed state of the roller 10, is such that frictional force between the roller 10 and paper 20 is measured continuously, while moving the paper 20 and that the movement of a local part (a tracer) near a portion, brought into contact with the paper of the roller 10 at a point of time before moving the paper 20, is monitored throughout the movement of the paper 20 so that static frictional force and dynamic frictional force are measured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction force measuring method and a friction force measuring device for measuring a friction force.

  In printers and copiers, a device for conveying sheets such as paper is provided. In such an apparatus, it is important to stably convey the sheet in order to suppress the occurrence of sheet jam. A sheet is generally conveyed by a roller. The conveyance of the sheet by the roller uses a frictional force between the roller and the sheet. In order to stably convey the sheet, it is necessary to prevent slippage between the roller and the sheet.

  In particular, in the sheet feeding unit, it is necessary to send out one of a plurality of sheets stacked on the tray. In general, a mechanism is used in which a roller comes into contact with the uppermost sheet among a plurality of stacked sheets and only one uppermost sheet is sent downstream. In this case, in order to prevent a plurality of sheets from being overlapped and conveyed, the frictional force between the roller and the sheet needs to be sufficiently high, and at least higher than the frictional force between the sheets. Don't be.

  Rubber has a particularly high frictional force among various materials and is generally used as a material for a roller (surface layer of the roller). In the case of metal or resin, the frictional force against the pressing load (vertical drag) is less than 1 time, whereas in the case of rubber, about 1 to 2 times the frictional force is generated. In the case of rubber, since it can be elastically deformed greatly, there is an advantage that even a rubber having a step can be conveyed by a roller.

  Here, the frictional force is roughly classified into two types: a static frictional force and a dynamic frictional force. The static friction force is a friction force generated when there is no relative movement between objects, and the maximum value is the maximum static friction force. Note that this maximum static frictional force is sometimes simply referred to as static frictional force. On the other hand, the dynamic friction force is a friction force generated when there is a relative movement between objects.

  In the case of the roller used in the above-described sheet feeding unit, a static friction force and a dynamic friction force act between the roller and the sheet. In order to perform stable feeding, it is important to increase the maximum static frictional force.

  Various methods are known as methods for measuring the frictional force between the roller and the sheet (see Non-Patent Documents 1 and 2). The frictional force is measured with the two members to be measured in contact with each other and with the two members pressed with a constant force. It is common to measure the frictional force.

  As described above, the transition of the frictional force with respect to time can be measured by a generally known frictional force measuring method. Thereby, it is possible to obtain data based on a graph in which the horizontal axis represents elapsed time and the vertical axis represents frictional force.

In any case, when the frictional force between two members that are non-elastic bodies (rigid bodies, etc.) is measured, the frictional force gradually increases while the relative movement between the two members is not occurring. It is well known that the frictional force decreases at the moment when it occurs and then becomes constant. That is, as described above, taking a graph with the elapsed time on the horizontal axis and the frictional force on the vertical axis, a graph is obtained in which the frictional force decreases after the peak appears and then the frictional force becomes constant. In this case, the peak frictional force is the maximum static frictional force, and the constant frictional force is the dynamic frictional force.

  On the other hand, when the frictional force is measured between an elastic body (superelastic body) having a large elastic deformation amount such as rubber and a non-elastic body, a graph in which a peak appears cannot be obtained. When the frictional force is measured between the elastic body and the non-elastic body, the frictional force gradually increases, and then the frictional force becomes constant without decreasing.

  From the visual observation at the time of measurement, the measurement results, and the knowledge about the friction force between inelastic bodies, the maximum static friction force and the dynamic friction force are considered to be equal with respect to the friction force between the elastic body and the inelastic body. Have been deceived.

  However, the idea that the maximum static frictional force and the dynamic frictional force are equal was not supported by sufficient verification. On the other hand, when measuring the frictional force between the elastic body and the non-elastic body, if the non-elastic body is moved while the two are in contact with each other, even if the non-elastic body moves, The part is deformed following the inelastic body, and a state in which no relative movement occurs between the two occurs. And after a part of elastic body deform | transforms to some extent, relative movement between both starts instantaneously. As a result, there was doubt about the idea that the maximum static frictional force and the dynamic frictional force are equal.

  On the other hand, as described above, in the case of a roller used in the sheet feeding unit, the maximum static frictional force is important. Therefore, even if the maximum frictional force on the graph is not actually the maximum static frictional force, the maximum frictional force is recognized as the maximum static frictional force in the conventional way of thinking. May be inappropriate.

However, the conventional measuring method and measuring apparatus cannot accurately verify which value is the maximum static frictional force.
Yuko Kobayashi, The Japan Society of Mechanical Engineers Information, Intelligence and Precision Equipment Conference Lecture Collection, “Examination of Friction Characteristics of Conveying Rubber Rollers Including High-Speed Regions and Test Methods”, 2002, P238-241 Wada Noriaki, Journal of the Japan Rubber Association "Vol. 70 No. 4 (1997)", P34-42

  An object of the present invention is to provide a frictional force measuring method and a frictional force measuring apparatus that can more accurately measure a static frictional force, a maximum static frictional force, and a dynamic frictional force.

  The present invention employs the following means in order to solve the above problems.

That is, the friction force measuring method of the present invention is:
Of the elastic body and non-elastic body in contact with each other (including rigid and flexible materials such as paper sheets (hereinafter the same)), these are in a state where the elastic body is fixed. In the frictional force measurement method for measuring the frictional force between the elastic body and the non-elastic body by moving the non-elastic body at a constant speed while maintaining the contact state,
While moving the inelastic body, while continuously measuring the frictional force between the elastic body and the inelastic body,
By monitoring the movement of a local portion in the vicinity of the portion in contact with the non-elastic body of the elastic body before moving the non-elastic body during the movement of the non-elastic body. It is characterized by measuring static friction force and dynamic friction force.

  According to the present invention, the moment when relative movement occurs between the elastic body and the non-elastic body by monitoring the movement of the local portion of the elastic body in the vicinity of the portion in contact with the non-elastic body. Can be grasped more accurately. Therefore, it is possible to more accurately grasp the moment of transition from the static friction state to the dynamic friction state.

  Here, when the inelastic body is moved, at first, only a part of the elastic body is deformed following the inelastic body, and no relative movement occurs between the two. In this way, in the process in which a part of the elastic body follows the inelastic body, the moving speed of the part in the vicinity that follows is almost the same as the moving speed of the inelastic body. The speed is also constant. However, the movement speed of the part changes at the moment when relative movement occurs between the two.

  Therefore, it is preferable that the frictional force when the moving speed of the local portion changes more than a certain value is recognized as the maximum static frictional force.

Moreover, the frictional force measuring device of the present invention is used for the above frictional force measuring method,
An apparatus for measuring a frictional force between the elastic body and the non-elastic body;
A camera having a zoom lens for photographing the movement of the local part;
An image processing apparatus for processing an image captured by the camera;
With
The image processing apparatus can obtain data in which an elapsed time is associated with an amount of movement of the local portion with respect to the elapsed time.

  According to the present invention, the image processing apparatus performs image processing while photographing the movement of the local portion of the elastic body with the camera, thereby obtaining the elapsed time and the amount of movement of the local portion with respect to the elapsed time. Correlated data is obtained. Thereby, since the movement speed of a local part is known, the moment which changed to a dynamic friction state from a static friction state can be grasped | ascertained more correctly.

  The image processing apparatus may be capable of tracking the movement of a predetermined portion with respect to the elastic body from a photographed image photographed by the camera.

Another frictional force measuring method of the present invention is:
The frictional force between these two members is measured by moving one of the two members in contact with each other while the other member is moved while the two members are in contact with each other. In the friction force measurement method,
While moving the other member, while continuing to measure the friction force between the two members,
Measurement of static frictional force and dynamic frictional force by monitoring the behavior of the local part where the two members are in contact before moving the other member while moving the other member It is characterized by performing.

  According to the present invention, by monitoring the behavior of a local portion where two members are in contact with each other, it is possible to more accurately grasp the moment when relative movement occurs between the two members. Therefore, it is possible to more accurately grasp the moment of transition from the static friction state to the dynamic friction state.

  The maximum static friction force may be obtained by setting the frictional force when it is determined that relative movement has occurred in the two members in the local portion as the maximum static frictional force.

Further, another friction force measuring device of the present invention is used for the above-described friction force measuring method,
An apparatus for measuring the frictional force of the two members;
A camera having a zoom lens for photographing the behavior of the local part;
It is characterized by providing.

  In addition, said each structure can be employ | adopted combining as much as possible.

  As described above, according to the present invention, the static friction force, the maximum static friction force, and the dynamic friction force can be measured more accurately.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

(Example)
With reference to FIGS. 1-4, the frictional force measuring method and frictional force measuring apparatus which concern on the Example of this invention are demonstrated.

<Friction force measuring device>
With reference to FIG. 1, a frictional force measuring apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of a frictional force measuring apparatus according to an embodiment of the present invention. In this embodiment, a case will be described in which the frictional force between the roller 10 whose surface layer is made of a rubber material (elastic body) and the paper 20 (non-elastic body) as a sheet is measured.

  As shown in FIG. 1, the paper 20 is sandwiched between a pair of rollers. One of the pair of rollers is a roller 10 that is a target for measuring the frictional force. The other is a metal roller 200 whose surface has a low frictional resistance. The roller 10 that is a target for measuring the frictional force is fixed and arranged so as not to rotate. On the other hand, the metal roller 200 is disposed in a rotatable state so that a frictional force does not act on the paper 20. Further, the metal roller 200 is configured to apply a certain force perpendicular to the paper 20. Thereby, a constant vertical load N is applied between the paper 20 and the roller 10.

  In such a state, the paper 20 sandwiched between the pair of rollers is pulled at a constant speed in a constant direction (arrow T). Then, the tensile force at this time is measured by the load cell 100. From this pulling force and the vertical load N, the frictional force between the roller 10 and the paper 20 can be calculated.

  In this embodiment, the contact portion between the roller 10 and the paper 20 is photographed from the side by a camera 300 including a high-speed camera 301 and a zoom lens 302. Further, an image photographed by the camera 300 is processed by the image processing apparatus 400 having the image display unit 401. In the image processing apparatus 400, it is possible to perform a process in which a captured image is associated with a frictional force with respect to elapsed time obtained through the load cell 100.

<Friction force measurement method>
In particular, a frictional force measuring method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an enlarged view of a part (X portion) of FIG. FIG. 3 is an explanatory view for explaining the behavior of the roller and the paper during the measurement of the frictional force. FIG. 4 is a graph showing the measurement result of the frictional force.

First, a marker (hereinafter referred to as the tracer 11) is attached to one point (local portion) of the roller 10 by the image processing apparatus 400 on the image taken by the camera 300 before the paper 20 is pulled. . The image processing apparatus 400 includes image processing software for tracking the tracer 11. Here, the tracer 11 is attached near the portion of the roller 10 that is in contact with the paper 20.

  Then, the paper 20 is pulled at a constant speed, and the movement amount of the tracer 11 from the beginning of the pulling is measured, and the frictional force is also measured. Thereby, the image processing apparatus 400 takes data in which the movement amount of the tracer 11 with respect to the elapsed time and the frictional force with respect to the elapsed time are associated with each other.

  FIG. 3A shows a state before the paper 20 is moved. As described above, the tracer 11 is attached on the photographed image near the portion of the roller 10 that is in contact with the paper 20. In FIG. 3, for convenience of explanation, an X mark 21 is also shown on the paper 20 side in the vicinity of the portion in contact with the roller 10 before the paper 20 is pulled. However, the X mark 21 does not have to be added on the image during actual measurement.

  FIG. 3B shows the state immediately after the paper 20 is moved. As shown in the figure, the positional relationship between the tracer 11 and the X mark 21 does not change immediately after the paper 20 is moved. That is, even if the paper 20 moves, the roller 10 partially follows the paper 20 and is only partially deformed, and there is no relative movement between the two.

  FIG. 3C shows a state at the moment when a relative movement occurs between the roller 10 and the paper 20. Even after the relative movement between the roller 10 and the paper 20 occurs, the tracer 11 slightly moves in the moving direction of the paper 20, but is then pulled back to the opposite side.

  After that, after the self-excited vibration in which the tracer 11 swings back and forth is generated, the vibration is attenuated by the damping effect and settles at a certain position.

  FIG. 4 is a graph showing an example of measurement results. As shown in the figure, initially, the amount of movement of the tracer 11 with respect to the elapsed time increases substantially constant. That is, at the beginning, the moving speed of the tracer 11 is substantially constant. This is because the paper 20 moves at a constant speed, and the tracer 11 follows this. In the graph, A indicates a point in time when the paper 20 starts to be pulled, and B indicates a period during which the tracer 11 is moving at a constant speed.

  In the graph, the gradient of the movement amount with respect to the elapsed time decreases when the elapsed time is around 0.5 seconds. That is, the moving speed of the tracer 11 decreases (D period in the graph). This is because the movement speed of the tracer 11 is slower than the movement speed of the paper 20 due to the relative movement between the roller 10 and the paper 20. This can also be verified from the captured image.

  In this way, when the movement speed of the tracer 11 changes (in practice, the movement speed is not completely constant even during the period B, so the movement speed changes more than a certain value) from the static friction state to the dynamic friction. It can be recognized that the status has been changed to. Therefore, the frictional force at this time (the frictional force at point C in the graph) is the maximum static frictional force.

  Thereafter, a period E in which the movement amount of the tracer 11 with respect to the elapsed time becomes unstable occurs. This is due to the above-described self-excited vibration. Thereafter, as described above, the movement amount of the tracer 11 is stabilized. Generally, the friction force when stabilized is the dynamic friction force.

As described above, in the graph, the period indicated by B is a static friction state, and the periods indicated by D and E are dynamic friction states. The frictional force at the time point C when changing from B to D is the maximum static frictional force. As can be seen from this graph, the frictional force increases even after changing from the static friction state to the dynamic friction state.

  From the above, it was confirmed that the idea that the maximum static friction force and dynamic friction force are equal is inappropriate. In practice, it has been found that the maximum static friction force is lower than the value at which the friction force is maximum.

  Thus, by attaching the tracer 11 to one point of the roller 10 and tracking the movement of the tracer 11, it is possible to more accurately grasp the moment when the relative movement between the roller 10 and the paper 20 occurs. can do. Thereby, it is possible to more accurately grasp the moment of transition from the static friction state to the dynamic friction state. Therefore, the transition of the static friction force, the transition of the dynamic friction force, and the maximum static friction force can be measured more accurately. Accordingly, for example, the frictional force of the roller can be evaluated more appropriately.

<Others>
The above-described friction force measurement method can also be applied to the friction force measurement between inelastic bodies. As an example, the case of measuring the frictional force between papers will be described with reference to FIGS. FIG. 5 is an explanatory diagram showing the state of the sheets being measured. FIG. 6 is a graph showing the measurement result of the frictional force.

  Even when the frictional force between the papers is measured, one paper 30 and the other paper 40 are brought into contact with each other. Then, the papers 30 and 40 are applied with a constant vertical load. Then, one of the papers 30 is pulled while maintaining a state where a certain vertical load is applied.

  When measuring the frictional force between papers, a tracer 31 is attached to one point on one paper 30 on the pulling side. The graph of FIG. 6 shows the measurement results. As can be seen from this graph, the moment when one of the sheets 30 moves becomes the highest in frictional force, and then the frictional force is stabilized. Thus, it can be seen that the largest frictional force at the moment of transition from static friction to dynamic friction is the maximum static frictional force.

  As described above, by monitoring the behavior of the local portion where the papers are in contact with each other, it is possible to more accurately grasp the moment when the state is changed from the static friction state to the dynamic friction.

  In the above embodiment, the method and apparatus for measuring the frictional force based on the tensile force have been described as examples. However, in the present invention, the method and apparatus for measuring the frictional force have been described in the above embodiment. However, other known techniques may be applied. For example, a method and apparatus for measuring a frictional force from a balance of rotational moments can be applied.

FIG. 1 is a schematic configuration diagram of a frictional force measuring apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a part (X portion) of FIG. FIG. 3 is an explanatory view for explaining the behavior of the roller and the paper during the measurement of the frictional force. FIG. 4 is a graph showing the measurement result of the frictional force. FIG. 5 is an explanatory diagram showing the state of the sheets being measured. FIG. 6 is a graph showing the measurement result of the frictional force.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Roller 11 Tracer 20 Paper 21 X mark 30 Paper 31 Tracer 40 Paper 100 Load cell 200 Metal roller 300 Camera 301 High speed camera 302 Zoom lens 400 Image processing apparatus 401 Image display unit

Claims (7)

By fixing the elastic body between the elastic body and the non-elastic body that are in contact with each other and moving the non-elastic body at a constant speed while maintaining the state in which they are in contact with each other, the elastic body and the non-elastic body In the friction force measurement method for measuring the friction force between the body and
While moving the inelastic body, while continuously measuring the frictional force between the elastic body and the inelastic body,
By monitoring the movement of a local portion in the vicinity of the portion in contact with the non-elastic body of the elastic body before moving the non-elastic body during the movement of the non-elastic body. A method for measuring frictional force, comprising measuring static frictional force and dynamic frictional force.   2. The frictional force measuring method according to claim 1, wherein the frictional force when the moving speed of the local portion changes by a certain level or more is recognized as the maximum static frictional force. In the frictional force measuring apparatus used for the frictional force measuring method according to claim 1 or 2,
An apparatus for measuring a frictional force between the elastic body and the non-elastic body;
A camera having a zoom lens for photographing the movement of the local part;
An image processing apparatus for processing an image captured by the camera;
With
The frictional force measuring device characterized in that the image processing device obtains data in which the elapsed time is associated with the amount of movement of the local portion relative to the elapsed time.   The frictional force measuring apparatus according to claim 3, wherein the image processing apparatus can track the movement of a predetermined portion with respect to the elastic body from a photographed image photographed by the camera. The frictional force between these two members is measured by moving one of the two members in contact with each other while the other member is moved while the two members are in contact with each other. In the friction force measurement method,
While moving the other member, while continuing to measure the friction force between the two members,
Measurement of static frictional force and dynamic frictional force by monitoring the behavior of the local part where the two members are in contact before moving the other member while moving the other member A method for measuring frictional force, characterized in that   6. The maximum static friction force is obtained using a friction force when it is determined that relative movement has occurred in the two members in the local portion as a maximum static friction force. Friction force measurement method. In the frictional force measuring apparatus used for the frictional force measuring method according to claim 5 or 6,
An apparatus for measuring the frictional force of the two members;
A camera having a zoom lens for photographing the behavior of the local part;
A frictional force measuring device comprising:

Images