JP2006194943A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus obtaining a high-quality image by keeping distances between members arranged around a photoreceptor and the photoreceptor constant. <P>SOLUTION: The image forming apparatus using an electrophotographic system is equipped with: a 1st member made cylindrical and rotatably held; at least one or more roller members abutting on the 1st member made cylindrical; a 1st piezoelectric member deformed in accordance with the positional displacement of the roller member; a 2nd member held to move in the radial direction of the 1st member made cylindrical; a 2nd piezoelectric element member connected to the 2nd member; a processing means for processing an output signal from the 1st piezoelectric member; and an input means for inputting the processed signal in the 2nd piezoelectric element. Then, the processing means processes the output signal from the 1st piezoelectric element member so as to cut the variation component thereof other than desired frequency by using a filter not to input in the 2nd piezoelectric element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  In an electrophotographic image forming apparatus, it is important to maintain a constant distance (clearance, gap) between a photosensitive member and an object disposed around it in order to obtain high image quality. Examples include a corona charging device that applies a charge to the photosensitive member, a developing roller of a developing device, and the like.

  Conventionally, the position of a corona charging device is determined by mechanical dimensional accuracy, and the gap between the charging wire and the photosensitive member is adjusted. In some developing devices, the gap between the photosensitive member and the developing roller is adjusted and set with high accuracy. Also, there has been a case where a roller-like abutting member is provided coaxially on both ends of the developing roller, and the gap is kept constant by abutting it against the photoreceptor.

  On the other hand, there is a type of piezoelectric element called bimorph. Reference is shown as an example of using this bimorph in an image forming apparatus. Bimorph is a piezoelectric element made of ceramic, and has a feature that it has a small amount of displacement but good response and large holding force as compared with a normal piezoelectric element (Patent Document 1).

JP-A-8-254877

  However, in the conventional configuration, in particular, in the configuration in which the gap between the photosensitive member and the developing roller is adjusted with high accuracy, it is necessary to process the deflection of the photosensitive member, its holding member, and developing sleeve with high accuracy. As a result, the cost of parts is increased.

  In the case of the abutting roller method, the shake of the photosensitive member can be canceled, but the developing roller and the abutting roller must be processed with high accuracy. In addition, if foreign matter adheres to the abutting roller, the developing roller may vibrate and the image may be deteriorated (pitch unevenness).

  As described above, the conventional methods such as mechanical dimensional accuracy and adjustment set have limitations in terms of manufacturing cost and performance, and it has been difficult to achieve higher image quality.

  The present invention has been made in view of the above problems, and an object thereof is to obtain a high-quality image by keeping the distance between a member disposed around the photoconductor and the photoconductor constant with high accuracy. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to achieve the above object, according to the present invention, in an image forming apparatus using an electrophotographic system, a cylindrical first member that is rotatably held and at least one roller that abuts on the cylindrical first member. A member, a first piezoelectric element member that deforms in accordance with the displacement of the roller member, a second member that is held movably in the radial direction of the cylindrical first member, and the second member. A second piezoelectric element member; a processing means for processing an output signal from the first piezoelectric element member; an input means for inputting the processed signal to the second piezoelectric element; The output signal from one piezoelectric element member is cut by using a filter to remove fluctuation components other than a desired frequency, and is not input to the second piezoelectric element.

  According to the present invention, the distance between the member disposed around the photoconductor and the photoconductor can be kept constant with high accuracy, so that a higher image quality than before can be obtained.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
FIG. 1 and FIG. 2 are structural views around the photosensitive member of the image forming apparatus according to the present invention. In FIG. The support member 4 is a bimorph, and both ends thereof are fixed to the support member and the apparatus main body. The bimorph 4 is attached in a state of being bent in advance, and the abutting roller 2 is always in contact with the photoreceptor 1.

  Two sets of the abutting rollers 2, the support member 3, and the bimorph 4 are provided, and the abutting rollers 2 are brought into contact with the image forming positions (both ends) of the photoreceptor 1, respectively.

  In FIG. 2, 5 is a developing device, 5a is a developing roller, 6 is a developing abutting portion, 7 is a bimorph, and 8 is a developing pressure spring. The developing device 5 is held so that it can approach / separate toward the center of the photoreceptor 1. The bimorph 7 is held at both ends by the apparatus main body and the development abutting portion 6. In this state, the bimorph 7 is not bent. The developing pressure spring 8 urges the developing device 5 in a direction away from the photosensitive member 1, and the position of the developing device 5 is fixed when a part of the developing device 5 contacts the developing abutting portion 6.

  The developing device 5 needs to adjust the initial position with respect to the photoreceptor 1. The method is as follows.

  The photoreceptor 1 and the developing roller 5a are exchanged for adjustment. This is manufactured with high accuracy and is so small that the vibration, variation in diameter, and the like can be ignored. In this state, adjustment is made so that a clearance (hereinafter referred to as an SD gap) between the adjusting photoconductor and the developing roller becomes a desired value. The adjustment is performed by moving the adjustment piece 8 in the developing device 5. After completion of the adjustment, the photoreceptor 1 and the developing roller 5a are returned to the actual ones.

  When any voltage is applied to the bimorph 7 in the above-described state, the bimorph 7 is displaced in the bending direction accordingly, so that the developing device 5 approaches or separates from the photoreceptor 1.

  The voltage fluctuation in the initial state of the apparatus will be described with reference to FIGS. The initial state refers to a state where the photoreceptor 1 and the abutting roller 2 are not worn or attached with dirt.

  When the image forming operation is started, the photosensitive member 1 rotates, and the abutting roller 2 rotates accordingly. The photoconductor 1 and the abutting roller 2 are cylindrical, but have a certain degree of radial deflection. The deflection of the bimorph 4 continues to change slightly due to the deflection, and a voltage is generated according to the deflection.

  FIG. 3A shows the voltage waveform. A voltage A (DC component) corresponding to the initial deflection amount of the bimorph 4, a wave having a large period of the photoreceptor (AC component), and a wave having a small period of two butting rollers (AC component) are output as an output voltage. Is done. FIG. 2B shows a frequency analysis of this voltage waveform. According to this, it can be seen that there is a peak in the frequency of one cycle of the photoreceptor due to the shake of the photoreceptor 1 and the frequency of two cycles of the butting roller due to the shake of the butting roller 2.

  This voltage signal is sent to the signal processing unit, where it is subjected to arithmetic processing and then input to the bimorph 7. The bimorph 7 is displaced in response to the signal, and the developing device 5 moves relative to the photoreceptor 1, so that the SD gap can be kept constant.

  The concept of signal processing is as follows.

  This will be described with reference to FIG.

  Since the rotation number of the photosensitive member 1 is known in advance, the frequency of the rotation cycle can be roughly calculated. As shown in FIG. 4A, the voltage waveform output from the bimorph 4 is subjected to a filter that cuts other frequency components while leaving only the vicinity of the rotational frequency of the photoreceptor 1. As a result, the original voltage waveform is as shown in FIG. This voltage signal is amplified by an amplifier according to the loss in the signal transmission path to have the same amplitude as the input signal, and then input to the bimorph 7. As a result, the developing device 5 moves following the fluctuation in the radial direction due to the shake of the photoreceptor 1, and as a result, the SD gap can be kept constant regardless of the shake of the photoreceptor 1.

  Next, a description will be given of a case where the use period of the apparatus becomes long, foreign matter such as toner adheres to the end of the photoreceptor 1, or the abutting roller 2 is worn out.

  This will be described with reference to FIG.

  As the durability progresses, a change appears in the output signal of the bimorph 2 due to dirt or irregularities on the surface of the photoreceptor 1, dirt or irregularities on the abutting roller 2, wear, or the like. That is, the fluctuation of the DC component (change from A to A + α) and the frequency component that did not exist at the beginning appear.

  For this, the following processing is performed in the signal processing unit.

  First, the variation α of the DC component is detected, and the waveform is shifted accordingly. Next, frequency components other than the photosensitive member rotation period are cut as in the initial stage. Finally, amplify.

  By performing such processing, the same waveform as in FIG. 4B can be extracted even after the durability of the apparatus has progressed. By inputting this to the bimorph 7, a constant SD gap can be maintained.

  As described above, in this example, it is possible to obtain a stable SD gap by controlling the position of the developing device using two pairs of bimorphs. Bimorph has a small displacement, but has good responsiveness and large holding force, so it is suitable for highly accurate control as in this example.

<Embodiment 2>
The developing device of Embodiment 1 can also be applied to a corona charging device.

1 is a configuration diagram around a photoconductor of an image forming apparatus according to the present invention. FIG. 1 is a configuration diagram around a photoconductor of an image forming apparatus according to the present invention. FIG. It is a figure which shows the voltage fluctuation in an initial state. It is a figure which shows the voltage waveform output from a bimorph. It is a figure which shows the voltage waveform output from a bimorph.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Abutting roller 3 Support member 4 Bimorph 5 Developing apparatus 5a Developing roller 6 Developing abutting part 7 High morph 8 Developing pressure spring

Claims (6)

In an image forming apparatus using an electrophotographic method,
A cylindrical first member rotatably held, at least one roller member in contact with the cylindrical first member, and a first piezoelectric element member deformed in accordance with the displacement of the roller member; A second member held movably in the radial direction of the cylindrical first member, a second piezoelectric element member connected to the second member, and an output signal from the first piezoelectric element member Processing means, an input means for inputting the processed signal to the second piezoelectric element, and an output signal from the first piezoelectric element member in the processing means by using a filter to vary the component other than a desired frequency The image forming apparatus is characterized in that is cut and not input to the second piezoelectric element.   The image forming apparatus according to claim 1, wherein the cylindrical first member is a photoconductor.   The image forming apparatus according to claim 1, wherein the piezoelectric element member is a ceramic piezoelectric element (hereinafter, bimorph).   The image forming apparatus according to claim 1, wherein the second member is a developing device.   The image forming apparatus according to claim 1, wherein the relative distance between the second piezoelectric element members connected to the second member can be adjusted to a desired amount.   The image forming apparatus according to claim 1, wherein the second member is a charging device.

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