JP2817854B2 - Method and apparatus for measuring nip width of pressure roller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a nip width of a pressure contact roller such as a fixing roller of a copying machine, and in particular, has a low roundness measurement accuracy. The present invention relates to improvement of measurement accuracy for a pressure roller.

2. Description of the Related Art For example, a pressing roller such as a fixing device roller of a copying machine requires accuracy. In order to make the fixing uniform, the fixing is performed by pressing the heated fixing roller and the pressure roller against each other, and rotating the paper with the toner image transferred between them by pressing the paper. It is done at the same time. Uniform fixing is achieved only by equalizing the pressing force between the two rollers. When the two rollers are pressed against each other, a press-contact portion is generated at the press-contact portion, and the width of the press-contact portion (hereinafter, referred to as “nip width”) becomes a factor representing the press-contact force. Therefore, uniform measurement of the fixing is premised on accurate measurement of the nip width.

Conventionally, the nip width was measured as follows. That is, paper that has been copied in a band shape in black in some places is passed through a fixing roller, and pressure is applied for a while between the rollers. Then, the paper was taken out, and the width of the portion discolored by applying pressure was measured as the nip width.

[Problems to be Solved by the Invention] However, in such a conventional measuring method, since paper is used manually, there are problems in terms of cost, efficiency, and accuracy.

In view of this point, in Japanese Patent Application Laid-Open No. Hei 2-13805, the applicant fixed a roller to be measured and arranged a distance sensor so as to be movable in a direction (X axis) orthogonal to the axis (Z axis) of the roller. Then, while moving the distance sensor in the X direction, a measurement method of measuring the distance from the sensor to the roller surface was proposed.

In this measurement method, from the distance data from the sensor to a plurality of points on the roller surface, for each roller, the equation of a circle approximating the circle of the cross section of the roller is obtained by the least squares method, and the two obtained circles are obtained. Is defined as the nip width at the intersection coordinates of the equation.

However, an actual pressing roller has a crease on its surface due to pressure. Since the creases degrade the roundness of the roller surface, the proposed technique by the present applicant could not find a highly accurate circle equation.

The present invention has been made from such a viewpoint, and an object thereof is to provide a method for measuring a nip width with high accuracy even for a pressure roller having a low roundness measurement accuracy due to, for example, a crease. And an apparatus.

[Means and Actions for Solving the Problems] A nip width measuring device for achieving the above object is a measuring device for measuring a nip width formed between two rollers that are pressed in parallel with each other. Y perpendicular to the roller axis
A distance sensor placed at a position separated in the direction, a distance sensor that measures the distance to a point on the outer periphery of each roller, and, in the X direction orthogonal to the Y direction, the roller and the sensor Changing means for changing the positional relationship; vibrating means for vibrating the roller to be measured in the axial direction of the roller; and changing the positional relationship between the roller and the sensor by a predetermined amount in the X direction. And
Collection means for collecting distance data to a point on the outer periphery of each roller measured by the distance sensor while vibrating the roller to be measured by the vibration means, and change position data changed by the change means, And calculating means for calculating the nip width based on the two approximate circles by approximating the outer circumferences of the two rollers with a circle based on the distance data and the change position data. .

Further, the invention according to the measuring method is a measuring method for measuring a nip width formed between two rollers pressed in parallel with each other, while vibrating a roller to be measured by a minute distance in a predetermined direction. A plurality of points on the circumference of the roller to be measured in the X and Y directions are measured by a distance sensor placed at the Y direction, and the positional relationship in the X direction between the distance sensor and the roller to be measured is changed. The measurement process was repeated while the X and Y of the points on the outer circumference of each of the two obtained rollers were obtained.
Based on the position data, the outer circumferences of the two rollers are approximated by a circle, and the nip width is calculated according to the intersection of the approximated circles.

That is, in the present invention, in order to collect the position data of a point on the outer periphery in order to approximate the roller surface in a circle,
By vibrating the roller by a small distance in a predetermined direction, even if the roundness is deteriorated due to a crease on the roller surface, position data in which the reduction in roundness in the vibration direction is compensated can be obtained. The approximate circle equation is calculated from the compensated position data.

Hereinafter, an embodiment in which the present invention is applied to a nip width measuring device in a fixing device of a copying machine will be described.

FIG. 1 is an overall view of a nip width measuring system of this embodiment. In FIG. 1, the fixing device main body 1 to be measured includes a fixing roller 2b and a pressure roller 2a. The main body 1 forms a work to be measured. Main body 1 is moving stage 5
The stage 5 can be moved in the vertical direction (X direction) by a pulse motor 7. The main body 1 as a work can be vibrated in the axial direction of the roller by the work vibrating section 9 including a piezo element therein. The outer shapes of the fixing roller 2b and the pressure roller 2a are measured by a contact type distance sensor 3. The distance sensor 3 is held by a moving stage 4 and is driven by a pulse motor 6 so as to be parallel to a horizontal plane and be fixed to the fixing roller 2b and the pressure roller 2a.
Can be moved in a direction (Y direction) perpendicular to the axis of.

The control and data processing for the nip width measurement are performed by the personal computer 15. That is, the pulse motor 7 for vertical movement is controlled by the driver 1, and the pulse motor 6 for horizontal movement is controlled by the personal computer 15 via the driver 2. Also, the vibration unit 9
When the output signal from the transmitter controlled by the personal computer 15 is amplified by the power supply 16, the output signal is input and vibrates in the axial direction of the roller. The output signal from the distance sensor is taken into the personal computer 15 via the A / D converter 14.

2 and 3 are views for explaining the principle of measuring the nip width.

FIG. 2 is a view for explaining the positional relationship between the distance sensor 3 used in the present embodiment and the roller to be measured.
Although there are originally two rollers, only one roller is shown in FIG. 2 for convenience of explanation. The sensor 3 emits a light beam, for example, and measures the distance to the subject from the relationship between the emitted light and the reflected light. The emission direction of the light beam is fixed. In the embodiment system shown in FIG. 1, the fixing device main body 1 is moved in the Y direction by an X direction step motor 7. That is, the relative position of the sensor 3 and the roller in the X direction is changed by the motor 7.

In FIG. 2, the time when the center of the roller is at the position A is the initial position at the start of measurement. Further, it is assumed that the sensor 3 is at a position X _a0 in the X direction.

When there is roller centered on the point A, the sensor 3, and obtain a distance Y _a0 from the sensor 3 to the point P ₀ on the roller periphery. Then, the coordinate data of the P ₀ point is (X _a0, Y _a0). Next, it is assumed that the fixing device main body 1 (that is, the roller) is moved to the position A 'in FIG. 2 by driving the motor 7 by ΔX. In this case, the distance from the sensor 3 to the roller, i.e., the distance to _a point P, as in FIG. 2, and to obtain a Y _a1. At this time, the outer peripheral point P ₁
The X direction coordinate data of the original position P ₁ ′ corresponding to the following is X _a0 −ΔX. That is, the coordinate value of the outer peripheral point P ₁ ′ when the roller center is at the point A is (X _a0 −ΔX, Y _a1 ). Here, if X _a1 = X _a0 −Δx, the outer peripheral point P ₁ ′
_Are (X _a1 , Y _a1 ). Such an operation is performed by moving the roller in the X direction by 2Δ.
If X, 3ΔX... Are continued, the coordinate value of each store on the outer periphery of the roller when the roller center is at the position A can be obtained.

The principle of measuring the nip width in the present embodiment will be described in more detail with reference to FIG. In FIG. 3, (X _a0 , Y _a0 ), (X _a1 , Y
_a1 ) to ( _Xan , _Yan ) are position data of points on the outer periphery of the pressure roller 2a obtained by the measurement as shown in FIG. 2 for the pressure roller 2a. Also, (X _b0 , Y _b0 ), (X _bn1 ,
_Yb1 ) to ( _Xb , _Ybn ) are position data of points on the outer periphery of the fixing roller 2b obtained by the measurement as shown in FIG. 2 for the fixing roller 2b. If the number of samples of these data is sufficiently large, the equation of the circle representing the roller when each roller is approximated to a circle should be formulated from the position data of the points on the outer periphery.

For example, the radius of the pressure roller 2a and r _a, the coordinates of the center and (C _Xa, C _Ya). In this case, the equation representing the circle of the pressure roller 2a is as follows: (X−C _Xa ) − (Y−C _Ya ) = r _a ² (1) Therefore, X ² + Y ² = 2XC _Xa + 2YC _Ya + (r ² −C _Xa ² −C _Ya ² ) is obtained. In this equation, (X _a0 , Y _a0 ), (X _a1 , Y _a1 ) to (X _an , Y
_an ), (X _b0 , Y _b0 ), (X _b1 , Y _b1 ) to (X _bn , Y _bn ) are substituted, and r _a , C _Xa , C _Ya are calculated by the least square method.

Let the radius of the fixing roller be r _b and the coordinates of its center be (C _Xb ,
C _Yb ) can be similarly calculated. That is,
The equation of the circle can be obtained.

(X−C _Xb ) − (Y−C _Yb ) = r _b ² (2) Therefore, as is apparent from FIG.
The distance between the points P and Q formed by the intersection of two circles (strictly speaking, the arc PQ of the pressure roller 2a), and two sets of the above two equations (1) and (2) obtained as simultaneous equations (X _P , Y _P ) and (X _Q , Y _Q ) are the position coordinates of the above two points. Thus, the nip width NP is, NP = a ^{_{{(X P -X Q) 2}} + (Y P -Y) 2} 1/2 ... (3).

In the system of the above embodiment, improvements are made to further increase the measurement accuracy. One factor that lowers the accuracy is the variation in the measurement of the outer peripheral position due to the pull existing on the roller surface. Another factor is the existence of work-in-place variations.

The catch refers to a spiral cutting trace having a constant pitch generated by the pressing of the pressing roller. Irregularities are generated on the surface of the cutting trace roller, and the roundness of the roller is reduced.

In this embodiment, in order to cancel the data variation due to the presence of the pull, the fixing device main body is caused to vibrate in the axial direction of the roller by the vibrator 9 during the measurement. Generally, since the roller is manufactured by a lathe or the like,
The fold occurs along the outer circumference of the roller. Therefore, as shown in FIG. 4, the distance in the Y direction is measured while the roller is vibrated in the axial direction, and the average value is calculated.
The average value is the one that compensates for the draw.

Next, a method of compensating for data due to the existence of work placement variations will be described. Generally, the mounting accuracy between the two rollers in the fixing device main body is high. However, when measuring the nip width, it is preferable to measure the nip width with a fixing device having a configuration close to the actual machine. However, since the fixing device main body 1 close to the actual machine is provided with various projections, there are various restrictions when mounting it on the moving stage 5, which causes errors in measurement. Therefore, in this embodiment, first, the roller which is less likely to be restricted in the arrangement, and in the embodiment of FIG.
Is measured first, the circular equation of the roller is approximated, and the original position of the other roller (the fixing roller 2b in the example of FIG. 1) is calculated based on the result. Then, the motor 7 is driven based on the positional relationship between the position where the fixing roller 2b should be and the sensor 3, and then the motor 6 is driven to move the sensor 3 to a position where the sensor 3 can measure most accurately. Like that. That is, the motor 7
The optimum position in the height direction (X direction) of the fixing device main body 1 is obtained by using the motor 6, and the optimum position of the sensor is obtained by the motor 6.

The pressure roller used in this embodiment is covered with rubber or the like, whereas the fixing roller is formed of metal or the like. Further, a sensor for distance measurement usually uses light such as laser light. For this reason, since the reflected light is diffused on the rubber surface of the pressure roller, the influence of the relative position of the sensor and the pressure roller in the height direction (X direction) is negligible in the positioning of the workpiece, and the measurement accuracy is negligible. Can be secured. However, since the fixing roller has a relatively high reflectance, the fixing roller is also affected by the R surface of the roller.

Therefore, in order to ensure the measurement accuracy of the fixing roller, first, the pressure roller is measured, the sensor is moved to the optimum position based on the result, and then the fixing roller is measured.

FIG. 5 is a personal computer of the FIG. 1 system.
15 is a flowchart of a control procedure program according to 15.

Steps S2 to S12 are measurement procedures for the pressure roller 2a, and steps S16 to S24 are measurement procedures for the fixing roller 2b.

In step S2, the main body 1 is moved to the initial position in the X direction by driving the motor 7. In step S4, the motor 6 is driven to move the sensor 3 to the measurable range. In step S6, the output (Y-direction data) of the distance sensor 3 is read. In step S8,
The roller is moved in the X direction by moving the motor 7 by ΔX. In step S10, it is determined whether data of the number of samples necessary for applying the least squares method has been obtained.

Once the required number of samples has been collected, go to step S1.
In step 2, based on the above equations (1) and (2), the pressure roller 2a
The radius r _a and the center position C _Xa , C _{Ya of} are calculated. In step S14, the radius r _a of the pressure roller 2a, the center position C
The mounting position of the fixing roller 2b is predicted based on _Xa and C _Ya . Then, in step S15, the fixing device main body is moved, and in step S16, if the roller 2b is located at the predicted position,
The motor 6 is driven to move the sensor 3 to a position where accurate measurement can be performed. The control of steps S18 to S24 is the same as that of steps S6 to S12 for the pressure roller 2a.

In this way, the equations of the approximate circles for the two rollers have been obtained. In step S26, the nip width NP is calculated based on the equation (3).

According to the measurement system of the embodiment described above, the following effects can be obtained. That is, using a non-contact type distance sensor, the position coordinates of the outer peripheral point of each roller are obtained, the approximate circle equation of the roller is calculated from the position data of these outer peripheral points, and the nip is calculated based on these equations. Width NP is calculated. Since these calculations can be performed by data processing on the order of a personal computer, automation of nip width measurement can be achieved. That is, it is possible to achieve higher measurement efficiency and higher accuracy.

: The measurement error due to the catch of the roller can also be canceled by applying vibration to the roller when measuring the coordinate data of the outer peripheral point.

: Of the two rollers, the roller (the pressing roller in the above embodiment) which is less likely to be restricted in arrangement is measured first, and based on the result, the other roller (fixing roller)
Since the mounting position of is estimated and the sensor position is adjusted based on the result of the estimation, the measurement accuracy is improved.

The present invention can be variously modified without departing from the gist thereof.

For example, two sensors (one for each roller) may be placed in the X direction to save tact time.

In the above embodiment, the movement in the X direction is performed on the roller side, but the sensor may be moved in the X direction.

Further, in the above-described embodiment, the vibration is applied to prevent the accuracy from being deteriorated due to the presence of the catch, but instead, a large number of sensors may be arranged in the axial direction of the roller, and the measured data may be averaged. Thus, data variations may be absorbed.

In the above embodiment, the least squares method is used as an approximation method, but the present invention is not limited to this approximation method.

[Effects of the Invention] As described above, the nip width measuring apparatus and method according to claims 1 and 7 of the present invention collect position data of points on the outer periphery of a roller surface in order to approximate the surface of the roller to a circle. When the roller is vibrated by a small distance in a predetermined direction, even if the roundness of the roller surface is low,
Position data in which the decrease in circularity in the vibration direction is compensated is obtained, and the equation of the approximate circle is calculated from the compensated position data. For this reason, even when the roundness of the roller is low due to, for example, a crease, the nip width can be measured with high accuracy.

According to the second aspect of the present invention, the two rollers can be moved integrally in the X direction to maintain the positional relationship between the two rollers.

Further, according to the device of the third aspect, the sensor is movable in the Y direction, and the sensor can be arranged at an optimum position.

According to the apparatus of claim 4, the circle approximation is performed by the least square method.

According to the apparatus of claim 5, the vibration is generated by the piezo element.

According to the apparatus of claim 6 and the method of claim 9,
The vibration direction is set in a direction parallel to the roller axis.
When the roller of the present invention is pressed or the like, a groove formed on the surface of the roller in a direction perpendicular to the roller axis, and a spiral groove (pull) extending in a direction parallel to the groove is formed by a roller. The radius of the roller varies in the axial direction, but the vibration effectively compensates for the variation in the radius of the roller in the axial direction.

According to the method of claim 8, upon measurement, measurement of one roller is performed first, the position of the other roller is predicted from this, and the sensor is moved to the optimum position with respect to the predicted position. So that the other roller is
This is effective when the roller is formed of a material that has a greater influence on the sensor accuracy than the one roller described above with respect to the curvature change.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment system in which the present invention is applied to measurement of a nip width of a roller of a fixing device. FIGS. 2 and 3 are diagrams for explaining a measurement principle of the embodiment. FIG. 5 is a diagram for explaining a method for preventing the accuracy from being degraded by a pull, and FIG. 5 is a flowchart for explaining a control procedure in the system of FIG. In the drawing, 1 ... the fixing device main body, 2 ... roller, 2a ... pressure roller,
2b ... fixing roller, 3 ... distance sensor, 4 ... Y direction moving stage, 5 ... X direction moving stage, 6 ... pulse motor for Y direction movement, 7 ... pulse motor for X direction movement, 8 ... ... Sensor fixing part, 9 ... Work vibrating part, 10,11
…… Pulse motor driver, 12 …… Motor controller, 13 …… Distance sensor controller, 14 …… A / D, 15…
… Personal computer, 16… Power supply for shaker, 17…
... Transmitter, 18 ... Stage fixing jig.

Claims (9)

(57) [Claims] 1. A measuring device for measuring a nip width formed between two rollers which are pressed against each other in parallel, wherein the distance sensor is located at a position separated in a Y direction perpendicular to the axis of the rollers. A distance sensor for measuring a distance to a point on the outer periphery of each roller; changing means for changing a positional relationship between the roller and the sensor in an X direction orthogonal to the Y direction; Vibrating means for vibrating by a minute distance in the direction of; and the changing means vibrating the roller to be measured by the vibrating means whenever the positional relationship between the roller and the sensor is changed by a predetermined amount in the X direction. Collecting means for collecting distance data to a point on the outer circumference of each roller measured by the distance sensor and change position data changed by the change means; And a calculation means for calculating the nip width based on the two approximate circles based on the data and the change position data. Nip width measuring device. 2. The nip width of a press roller according to claim 1, wherein said changing means includes a first moving means for integrally moving said two rollers in said X direction. Measuring device. 3. A distance sensor is located on a second moving means for moving said sensor in said Y direction, said second moving means being adapted to move said roller within the measuring range of said sensor. 2. The method according to claim 2, wherein the sensor is moved.
The measuring device of the nip width of the pressure contact roller according to the above item. 4. The method according to claim 1, wherein said calculating means approximates the outer periphery of the roller to a circle by a least square method, and calculates a nip width based on coordinates of an intersection of two circles. Measuring device for nip width of pressure roller. 5. The apparatus according to claim 1, wherein said vibrating means vibrates the roller by a piezo vibrator. 6. The apparatus according to claim 1, wherein said vibrating means vibrates the roller to be measured in the axial direction of the roller to be measured. 7. A measuring method for measuring a nip width formed between two rollers which are pressed in parallel with each other, the method comprising: vibrating a roller to be measured by a minute distance in a predetermined direction; A plurality of points on the circumference of the circle in the X and Y directions are measured by a distance sensor placed at the Y direction position, and the measuring step is performed while changing the positional relationship in the X direction between the distance sensor and the roller to be measured. Is repeated based on the obtained X and Y position data of the points on the outer circumference of each of the two rollers, and the outer circumference of the two rollers is approximated by a circle, and the nip width is calculated according to the intersection line of the approximated circle. A measuring method for measuring the nip width characterized by the following facts. 8. A circle approximation for one roller is performed first, the position of the other roller is estimated from the approximate circle, and the sensor comes to an optimum position with respect to the estimated position of the other roller. 7. The method for measuring a nip width of a pressure roller according to claim 6, further comprising the step of adjusting the nip width of the pressing roller. 9. The method according to claim 7, wherein the roller to be measured is vibrated in a direction parallel to an axial direction of the roller.