JPH08297005A - Apparatus for measuring nip width - Google Patents

Abstract

PURPOSE: To prevent an object to be measured from being broken, improve the measuring accuracy and operability and shorten the measuring time. CONSTITUTION: In the apparatus for measuring nip width, a measuring roll 7 of the same size as a second roll in touch with a conductive or semi- conductive first roll 2 and comprising a high resistance area 7B and a low resistance area of larger length than the nip width is held in touch with the first roll 2 in place of the second roll, and a predetermined voltage is impressed between the first roll 2 and the low resistance area of the measuring roll 7. In this state, the first roll 2 and measuring roll 7 are rotated at a predetermined relative speed. The nip width is calculated in accordance with a current value of a nip between the first roll 2 and measuring roll 7 which changes correspondingly to a change of a touch area between the first roll 2 and low resistance area of the measuring roll 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nip width measuring device for measuring the nip width of a nip portion formed between a conductive or semi-conductive roll and a roll in contact therewith, and more particularly, to an object to be measured. The present invention relates to a nip width measuring device capable of preventing the destruction of the nip, improving the measurement accuracy and workability, and shortening the measurement time.

[0002]

2. Description of the Related Art In an image forming apparatus, in order to charge a photosensitive drum or transfer a toner image formed on the surface of the photosensitive drum onto a recording sheet, a predetermined voltage is applied in contact with the photosensitive drum. There are cases where a semi-conductive rubber roll is used. In such an image forming apparatus, charging characteristics and transfer characteristics are determined by the nip width between the photosensitive drum and the semi-conductive rubber roll and the output value of the semi-conductive rubber roll. Accordingly, it is necessary to control the output of the semiconductive rubber roll. That is, FIG.
As shown in FIG. 3, the nip width W between the semiconductive rubber roll 2 having the metal shaft 1 electrically connected to the power source and the photosensitive drum 3 is measured, and when the nip width is small, the semiconductive rubber roll 2 is measured. In order to improve the image quality, it is necessary to increase the voltage value, the current value, or the like, and decrease the nip width when the nip width is large.

As a conventional nip width measuring method for measuring the nip width between the photosensitive drum and the semiconductive rubber roll, for example, there are the following methods. (1) Ink transfer method Apply paper or the like on the surface of the photoconductor drum and apply ink to the surface of the semiconductive rubber roll, and when the two are in contact, the transfer width of the ink transferred to the surface of the photoconductor drum is set. taking measurement. (2) Discharging method As shown in FIG. 14, a DC power source 4 is connected to the metal shaft 1 of the semi-conductive rubber roll 2 and the photoconductor drum 3, and a predetermined voltage is applied to both of them, so that the photosensitive drum is exposed as shown in FIG. Body drum 3
A discharge is generated on the surface of the photosensitive drum 3, and the discharge trace due to the discoloration formed on the surface of the photosensitive drum 3 is measured. (3) Pressure sensitive paper method A pressure sensitive paper whose color changes with pressure is sandwiched between the semi-conductive rubber roll and the photoconductor drum, and the discoloration width of the pressure sensitive paper is measured. (4) Hertz formula calculation method The nip width W is calculated using the following Hertz's law formula.

[Equation 1]Where v₁Is the Poisson's ratio of the semiconductive rubber roll,
₁Is the Young's modulus of the semi-conductive rubber roll [kg / mm²]
, W is the linear load [kg / mm], v₂Is the photoconductor drum
Poisson's ratio of₂Is the Young's modulus of the photosensitive drum [kg
/ Mm²], R ₁Is the radius of the semi-conductive rubber roll [m
m], r₂Is the radius [mm] of the photosensitive drum
Show.

[0004]

However, the above-mentioned method for measuring the nip width has the following problems. (1) In the case of the ink transfer method, since the semiconductive rubber roll is coated with ink, the quality of the measured object may be deteriorated and the measured object may be destroyed. (2) In the case of the discharge method, as shown in FIG. 15, the nip width W ′ due to the discharge becomes larger than the actual nip width W by α depending on the measurement conditions, and the measured values vary and the measurement accuracy decreases. (3) The pressure-sensitive paper method has poor workability and requires skill and time for measurement. (4) In the case of Hertzian calculation method, Young's modulus is roll shape,
Since it varies depending on rubber hardness, rubber thickness, etc., an error occurs in the measured value. That is, as shown in FIG. 16, even if the linear load is the same, if the rubber hardness and the outer diameter of the roll are different, the amount of displacement between the shafts of the photosensitive drum and the semiconductive rubber roll, that is, the nip width is different. , When calculated by the Hertz's law formula, it is not possible to obtain a measured value that takes into account this variation in Young's modulus.

Therefore, it is an object of the present invention to provide a nip width measuring device capable of preventing the destruction of an object to be measured, improving the measurement accuracy and workability, and shortening the measurement time.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention aims to prevent destruction of an object to be measured, improve the measurement accuracy and workability, and shorten the measurement time. It has the same size as the second roll that contacts the electrically conductive first roll, and the first roll replaces the first roll.
And a predetermined voltage is applied between the measuring roll, which is in contact with the first roll and the low resistance region having a length larger than the nip width, and the low resistance region of the first roll and the measuring roll. Change in contact area between the voltage application unit, the first roll, and the rotation driving unit that rotates the measurement roll at a predetermined relative speed, and the contact area between the first roll and the low resistance region of the measurement roll due to rotation of the relative speed. A nip width measuring device provided with a current detecting means for detecting a current between the nip of the first roll and the measuring roll, which changes in accordance with the above, and a nip width calculating means for calculating the nip width according to the current value. It is provided.

[0007]

A predetermined voltage is applied between the low resistance regions of the first roll and the measuring roll to rotate the first roll and the measuring roll at a predetermined relative speed. The current detecting means detects the current between the nip between the first roll and the measuring roll, which changes according to the change in the contact area between the first roll and the low resistance region of the measuring roll by the rotation of the relative speed. ,
The nip width calculation means calculates the nip width according to the current value.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The nip width measuring device of the present invention will be described in detail below with reference to the accompanying drawings.

1 and 2 show the construction of a nip width measuring device according to an embodiment of the present invention. This nip width measuring device includes a measuring roll 7 having the same size as the photosensitive drum, in which an electrode 6 is provided on a part of the insulator surface,
A load roll 8 that presses the conductive rubber roll 2 as a measured object against the measurement roll 7 with a predetermined load, and a constant voltage such that no discharge occurs between the metal shaft 1 and the electrode 6 of the conductive rubber roll 2 (this embodiment). Then, a DC constant power source 9 for applying 100 V), a minute ammeter 10 connected between the metal shaft 1 and the DC constant power source 9 for measuring a minute current flowing through the conductive rubber roll 2, and a measuring roll 7 are rotated. The nip width W is calculated by performing a graph process or a predetermined calculation process on the basis of the current value of the minute ammeter 10 while controlling the drive of the motor 14, the drive circuit 15 that drives the motor 14, and the drive of the motor 14. The calculation result is displayed on the display unit 13
A computer 13 for displaying on A is provided.

The measuring roll 7 is supported by an insulating block 12 and is rotated by a rotational force of a motor 14 and is rotated by a metal shaft 7A, and an insulator 7B made of a high resistance resin is provided on the outer periphery of the metal shaft 7A. , An electrode 6 of 4 mm square embedded in an insulator 7B, and the electrode 6 is connected to an anode of a constant DC power supply 9.

The semi-conductive rubber roll 2 is made of semi-conductive rubber having a rubber hardness of 72 ° provided on the outer circumference of the metal shaft 1 electrically connected to the terminal 11, and the load roll 8 has a weight of 500 gf at each end. The load is added. The terminal 11 is connected to the cathode of the DC constant power source 9,
A micro ammeter 10 with a built-in constant voltage source with a minimum resolution of 1 pA is inserted between them. The load roll 8 employs a system in which a weight is placed on the slide rail so that the semi-conductive rubber roll 2 is not affected by the outer diameter accuracy, runout, and the like.

In the computer 13, the measuring roll 7 has a predetermined rotation speed (0.1 rpm in this embodiment) at the time of measurement.
The drive circuit 15 is controlled so as to rotate at. Further, the current flowing through the semiconductive rubber roll 2 when the electrode 6 comes into contact with the semiconductive rubber roll 2 due to the rotation of the measuring roll 7 is input as a current value signal from the minute ammeter 10 every 30 μm, and shown in FIG. The nip width W is calculated by creating a graph or performing the following predetermined arithmetic processing.

The calculation process for calculating the nip width W will be described with reference to FIGS. 4, 5 and 6.

To calculate the nip width W, the current value flowing between the electrode 6 and the metal shaft 1 and the position of the electrode 6 with respect to the nip are measured in real time, the electrode position where the current value changes is read, and the electrical energization width is calculated. By measuring.
That is, in FIG. 4 which schematically shows the graph of FIG. 3, point A is a boundary portion where the nip portion of the semi-conductive rubber roll 2 and the electrode 6 start contact, and the tip of the electrode 6 is at the position b (see FIG. b)). Therefore, in the region before the point A, since the semiconductive rubber roll 2 is in contact with the insulator 7B of the measuring roll 7, no current is passed and the current value shows the minimum value. When the tip of the electrode 6 passes through the point A, the contact width gradually increases and the current value accordingly increases ((c) to (e) in FIG. 5). Point B is a boundary portion where the entire nip portion of the semiconductive rubber roll 2 and the electrode 6 start contact, and the tip of the electrode 6 is at the f position (see FIG. 5).
(f)). Therefore, the current value shows the maximum value from the region after the point B. Point C is a boundary portion where the electrode 6 ends contact with the entire nip portion of the semiconductive rubber roll 2, and the electrode 6
Indicates that the tip of is at the u position. When the tip of the electrode 6 passes through the point C, the contact width gradually decreases and the current value accordingly decreases ((c) to (e) in FIG. 6). Point D is a boundary portion where the nip portion of the semiconductive rubber roll 2 and the electrode 6 finish contact, and the tip of the electrode 6 is at the z position ((f) in FIG. 6). From the relationship between the current value and the position of the electrode 6, the point A
Based on the position of ~ D and the width T of the electrode 6, the following (1) ~ (4)
The nip width W is calculated by the above method. (1) Calculated from energization start point A and end point D W = A−D−T (2) Calculated from energization start point A and maximum current value reaching point B W = B−A (3) Maximum current value reaching point B And calculated from the maximum current value end point C W = TC−B (4) Calculated from the maximum current value end point C and energization end point D W = D−C

The method of measuring the nip width will be described below. First, a semiconductive rubber roll 2 having a rubber hardness of 72 ° and an outer diameter of 14 mm is prepared, and a load force of 500 gf is applied to both ends of the metal shaft 1 by the load roll 8 to set the semiconductive rubber roll 2 to the measurement roll 7 Contact.

Next, a voltage of 100 V is applied between the metal shaft 1 and the electrode 6 from the direct current constant power source 9, and the computer 1
3 controls the drive circuit 15 to move the measuring roll 7 to 0.1 r.
Rotate at a rotation speed of pm.

When the measuring roll 7 rotates with the voltage applied between the metal shaft 1 and the electrode 6 as described above,
When the electrode 16 of the measuring roll 7 comes into contact with the semiconductive rubber roll 2, a current flows between the nips. Computer 13
Input the amount of displacement of the current value of the micro ammeter 10 every 30 μm, create the graph shown in FIG. 3, and perform the above-mentioned calculation based on the relationship between the electrode position and the energization amount shown in FIG. The nip width W between the conductive rubber roll 2 and the measuring roll 7 is calculated.

FIG. 7 shows the relationship between the linear load and the nip width of the samples A to C having different outer diameters and hardnesses and the sample D having an outer diameter of 14 mm obtained by the Hertz's law by such a measuring method. It is shown. As can be seen from the above, the Hertz's law formula gives only one measurement result with the outer diameter as a parameter, but the measurement as in this example gives a measurement result considering the fluctuation of the Young's modulus.

FIG. 8 shows a second embodiment of the present invention in which the measuring roll 7 is of A4 size, and a plurality of electrodes 6A, 6B, 6C are provided at different intervals in the axial direction. . FIG. 9 shows a sectional view of the electrodes 6A to 6A.
6C has terminals 17A to 17 on the opposite side through the through conductor 16.
Lead wires 17a to 17c which are connected to C and are connected to the DC constant power source 9 are attached to each.

When such a measuring roll 7 is used in the first embodiment, the nip width can be measured at a plurality of positions in the axial direction. FIG. 10 shows an example of the measurement result, and it can be seen from this that the nip width at both ends in the axial direction is large and the nip width at the center is small.

FIG. 11 shows a third embodiment of the present invention.
In the nip width measuring device of this embodiment, the roll surface of the semiconductive rubber roll 2 is brought into contact with the measuring metal shaft 18,
A micro ammeter 9 and a constant DC power source 10 are inserted between the electrode 6 of the measuring roll 7 and the measuring metal shaft 18, and an adhesive layer 5 is provided between the semiconductive rubber roll 2 and the metallic shaft 1. When interposed and electrically insulated, the current flowing from the measurement metal shaft 18 to the semiconductive rubber roll can be detected.

In the present invention, the nip width was measured by changing the current value by applying a voltage to the extent that no discharge was generated, but the measurement of the discharge width as described in the section of the prior art in this method is also included. It is also possible to do so. FIG. 12 shows the relationship between the two types of nip widths measured by this method and the measured voltage. Even with the measurement by this method, as the measured voltage becomes higher, discharge occurs between the DUT and the electrode, and The value is large. Since the size increases according to Paschen's law, the discharge width can be measured.

[0023]

As described above, according to the nip width measuring device of the present invention, the nip width measuring device has the same size as the second roll contacting the conductive or semi-conductive first roll, and has a high resistance. A measuring roll comprising a low resistance region having a length larger than the region and the nip width is contacted with the first roll instead of the second roll, and between the first roll and the low resistance region of the measuring roll. The first roll and the measurement roll are rotated at a predetermined relative speed in a state where a predetermined voltage is applied, and the first roll and the measurement roll change in accordance with a change in the contact area between the low resistance region of the measurement roll and the first roll. Since the nip width is calculated according to the current value between the nip of the roll of No. 1 and the roll for measurement, destruction of the object to be measured is prevented, measurement accuracy and workability are improved, and measurement time is shortened. Can be planned.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between an electrode position and a current value according to an example.

FIG. 4 is a graph that schematically represents FIG.

FIG. 5 is an explanatory diagram showing a relationship of nip portions at electrode positions according to an embodiment.

FIG. 6 is an explanatory diagram showing the relationship of the positions of the electrodes and the nip portion according to the embodiment.

FIG. 7 is a graph showing the relationship between the line load and the nip width when the outer diameter and hardness are different.

FIG. 8 is an explanatory view showing a measuring roll according to a second embodiment of the present invention.

FIG. 9 is an explanatory view showing a measuring roll according to a second embodiment of the present invention.

FIG. 10 is a graph showing nip widths at a plurality of axial positions according to the second embodiment.

FIG. 11 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 12 is a graph showing the relationship between measured voltage and nip width.

FIG. 13 is an explanatory diagram showing a nip width between a semiconductive rubber roll and a photosensitive drum.

FIG. 14 is an explanatory diagram showing a conventional nip width measuring method.

FIG. 15 is an explanatory diagram showing a conventional nip width measuring method.

FIG. 16 is a graph showing the relationship between the linear load and the displacement amount when the outer diameter and hardness are different.

[Explanation of symbols]

 1 Metal Shaft 2 Semi-Conductive Rubber Roll 3 Photosensitive Drum 4 Power Supply 5 Adhesive Layer 6 Electrode 7 Measurement Roll 7A Metal Shaft 7B Insulator 8 Load Roll 9 DC Constant Power 10 Micro Ammeter 11 Terminal 12 Insulation Block 13 Computer 13A Display 14 motor 15 drive circuit 16 through conductor 17A to 17C terminal 17a to 17c lead wire 18 metal shaft for measurement

Claims (1)

[Claims] 1. A nip width measuring device for measuring a nip width of a nip portion formed between a conductive or semi-conductive first roll and a second roll in contact with the first roll. A measuring roll that has the same size as the roll and that is in contact with the first roll instead of the second roll and that has a high resistance region and a low resistance region having a length larger than the nip width. Voltage applying means for applying a predetermined voltage between the low resistance regions of the first roll and the measuring roll, and rotational drive for rotating the first roll and the measuring roll at a predetermined relative speed. Means, between the nip of the first roll and the measurement roll, which changes according to a change in contact area between the first roll and the low resistance region of the measurement roll by rotation of the relative speed. Current Current detection means for output, the measuring apparatus of the nip width, characterized in that it comprises a nip width calculation means for calculating the nip width according to the current value.