JPH08286508A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of always maintaining an optimum developing gap between an image carrier and a developer carrier. CONSTITUTION: A gap measuring device 11 is provided with a measuring device constituted of a light emitting part 11a emitting laser light and a light receiving part 11b receiving the laser light and an arithmetic part 13 for calculating a developing gap Gp with a signal of the number of interceptions of the laser light from the measuring device. In the gap measuring device 11, plural measuring devices are arranged outside the area where an image of a photoreceptor 1 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrostatic latent image by supplying a developer to the surface of an image bearing member on which an electrostatic latent image is formed, by using a developer bearing member. , Printer,
The present invention relates to an image forming apparatus such as a copying machine and a facsimile.

[0002]

2. Description of the Related Art In the above image forming apparatus, for example,
When a developing device using a two-component developer containing toner and carrier is used, the development gap between the photoconductor as an image carrier and the developing roller as the developer carrier is such that the image density or the image on the carrier is It is an important characteristic that affects the mechanical quality such as image quality and toner scattering.

In the conventional image forming apparatus, the developing gap is not adjusted at the shipping stage, and when the machine starts to be used, the gap is formed by abutting rollers, and the photosensitive member shaft and the developing roller shaft are set on the same surface plate. The method is roughly classified into a method of adjusting the gap by adjusting the gap and a method of adjusting the developing gap in advance at the shipping stage.

[0004]

However, the former type of image forming apparatus cannot cope with a change in the development gap due to wear of parts and the like due to use over time. Furthermore, there is a problem that if the precision of the related parts varies, the development gap also varies.

Further, in the image forming apparatus of the latter type, since adjustment is performed by a jig in the product process one by one, it is not compatible with other photoconductors or developing devices in a strict sense. There was a problem.

The present invention solves the above-mentioned conventional problems,
An object of the present invention is to provide an image forming apparatus which can always maintain an optimum developing gap between the image carrier and the developer carrier.

[0007]

In order to achieve the above object, the present invention uses a developer carrying member facing the surface of an image carrying member on which an electrostatic latent image is formed, and supplies the developer to the surface. Then
In an image forming apparatus for developing the electrostatic latent image, a gap measuring device for measuring a developing gap between the image bearing member and the developer bearing member is provided outside an area of the image bearing member where an image is formed. The feature is that it is provided.

Further, it is effective that the gap measuring device measures the time required for one revolution of the developer carrier and the time corresponding to the least common multiple of the time required for one revolution of the image carrier.

Further, it is effective that a gap adjusting mechanism for adjusting the developing gap between the image bearing member and the developer bearing member is provided, and the upper limit and the lower limit of the adjustment width are set in the gap adjusting mechanism. Is.

Further, the gap adjusting mechanism follows the measurement of the time required for one revolution of the developer carrier of the gap measuring device and the time corresponding to the least common multiple of the time required for one revolution of the image carrier. When activated, it is effective.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing an example of a two-component developing device to which the present invention is applied, and its configuration and operation will be briefly described.

In FIG. 1, a developing device 2 has a developing roller 3 as a developer carrying member which is arranged so as to face a photosensitive member 1 as an image carrying member, and the developer in the developing device 2 is developed by a carrying paddle 4. It is sent to the roller 3. The developer sent to the developing roller 3 is scraped off by the doctor 5 and sent in a fixed amount, and the developing roller 3 rotates in the forward direction with the photoconductor 1 to perform development. The developer scraped off by the doctor 5 is sent to the separator 7 and the carrying screw 6, and is returned to the carrying section again.

On the other hand, the toner density is detected by the P sensor (see FIG. 1).
When the toner density becomes low, the toner replenishing clutch (not shown) is turned on and the toner in the toner cartridge 10 is supplied to the developing portion by the replenishing roller 9. Then, the supplied toner is stirred with the developer by the stirring roller 8.

In the developing device 2, the developing gap Gp between the photoconductor 1 and the developing roller 3 is an important characteristic that influences the image quality such as image density and carrier-adhered image and the mechanical quality such as toner scattering. Therefore, in the present invention, in order to maintain the development gap Gp at the optimum gap value, the gap measuring device 1 for measuring the size of the development gap Gp shown in FIG.
1 is provided.

The gap measuring device 11 of the present embodiment is developed by a measuring device 12 including a light emitting portion 11a for emitting a laser beam and a light receiving portion 11b for receiving the laser beam, and a signal of the laser beam cutoff number from the measuring device 12. And a calculation unit 13 that calculates the gap Gp. And the gap measuring device 1
1 has a plurality of measuring devices 12a, 12b, 12c, of which the measuring devices 12a, 12b are arranged outside the region of the photoreceptor 1 for forming an image, as shown in FIG. That is, it is arranged outside the maximum sheet passing width L of the image forming apparatus. Thus, if the measuring devices 12a and 12b are arranged outside the image area, not only the measurement laser light does not adversely affect the image, but also the amount of the developer on the developing roller 3 is smaller than that in the image area. The development gap Gp can be measured with high accuracy.

Further, in this embodiment, the measuring device 12c is also arranged in the image area. The measuring device 12c needs to perform the measurement only during warm-up or during image formation such as paper interval so that the laser beam does not adversely affect the image. Further, for example, it is necessary to rotate the developing roller 3 at a low speed before performing the measurement so that the developer on the developing roller is reduced. On the other hand, the measuring devices 12a and 12b arranged outside the image region are not subject to such a restriction, which is advantageous, and the measuring device 12c may be installed as necessary.

Next, the developing gap G by the measuring device 11
An example of the measurement time of p will be described. The measurement time is the time required for one rotation of the developing roller 3 and the time corresponding to the least common multiple of the time required for one rotation of the photoconductor 1. That is,
As shown in FIG. 4, when the rotational speeds of the photoconductor 1 and the developing roller 3 are X and Y, respectively, and the least common multiple of the reciprocals 1 / X and 1 / Y is T, the developing gap Gp of Since there is adjustment, the development gap Gp at T time is measured.
For example, at the time of initial setting of the machine, the development gap Gp of T time
Is measured, and the development gap Gp is adjusted in the T time period based on this data. Accordingly, it is possible to know the constant cycle of Gp adjustment due to the eccentricity between the photoconductor 1 and the developing roller 2 or the circularity.

FIG. 5 is a plan view showing an example of a gap adjusting mechanism 20 for adjusting the developing gap Gp. The developing device 2 is set on a rail (not shown), and the developing roller 3 is attached to the photosensitive member 1. On the other hand, it is supported so as to be movable in the contact and separation directions. The photoconductor 1 is attached to the developing device 2.
A pinion 22 that meshes with a rack 21 that extends in the contact and separation direction of
The pinion 22 is driven by a stepping motor 23 supported by the developing device 2 via a drive gear 24. The stepping motor 23 is driven by a signal from the control unit 30, and the driving of the stepping motor 23 moves the developing device 2 in the contacting / separating direction of the photoconductor 1 to adjust the gap value between the photoconductor 1 and the developing roller 3. Is configured. In this case, the movement amount is set so that one step of the stepping motor 23 is 0.1 mm or less. If the amount corresponding to one step is set to 0.1 mm or less, it is possible to have an adjusting ability higher than the manual adjustment of the developing gap Gp.

Further, as shown in FIG. 6, the moving width of the developing device 2 is restricted by the rail 24 by providing the rail 24 formed in the long hole so that the upper and lower limits of the moving width are controlled.
Therefore, it is possible to prevent the problem that the developing roller 3 comes into contact with the photoconductor 1 even when the developing roller 3 comes closest to the photoconductor 1.

Gap control of the image forming apparatus having the above structure will be described with reference to FIG. In FIG. 7, a control unit 30 for controlling the operation of the stepping motor 23 is provided,
The control unit 30 has a gap signal from the gap measuring device 10, an image density signal from the P sensor 31, and a density designation from a density adjusting unit 32 provided on an operation panel (not shown) operated by a user. A signal and a setting signal from a serviceman mode dedicated to an expert such as a serviceman are input.

Therefore, the development gap Gp can be adjusted automatically by the gap signal of the gap measuring device 10 to always maintain a constant development gap Gp and obtain a stable image. Furthermore, since the gap adjusting mechanism 20 operates according to the output value of the P sensor 31, it is possible to always secure a stable image density. Furthermore, since the gap adjusting mechanism 20 operates according to the density adjustment of the density adjusting unit 32 by the user, it is possible to perform the density adjustment with higher accuracy. Furthermore, since it is possible to perform automatic adjustments exclusively for professionals such as the setting signal in the serviceman mode, a special jig is used for adjustment when an unexpected situation such as replacement of the developing unit or photoconductor or failure occurs. You can do it without doing. Since the Gp adjusting mechanism operates according to the output value of the density sensor, it is possible to always secure a stable image density.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made. For example, in the above-described embodiment, the developing gap Gp is adjusted by moving the entire developing device, but the developing gap Gp may be adjusted by moving only the developing roller. Further, the gap measuring device may be a sensor that uses light other than laser light.

[0023]

According to the first aspect of the present invention, there is provided a gap measuring device for measuring the development gap between the image bearing member and the developer bearing member, outside the area where the image is formed on the image bearing member. Since it is provided, highly accurate gap measurement can be obtained without affecting the image quality.

According to the second aspect of the invention, the gap measuring device measures the time required for one revolution of the developer carrier and the time corresponding to the least common multiple of the time required for one revolution of the image carrier. It is possible to know the constant cycle of Gp adjustment due to the eccentricity and roundness of the image carrier and the developer carrier.

According to the structure of claim 3, a gap adjusting mechanism for adjusting the developing gap between the image bearing member and the developer bearing member is provided, and the upper limit and the lower limit of the adjustment range are set in the gap adjusting mechanism. Therefore, it is possible to prevent the development gap from being adjusted more than necessary, and to prevent problems from occurring.

According to the structure of claim 4, the time required for the gap adjusting mechanism to make one rotation of the developer carrier of the gap measuring device and the time required for one rotation of the image carrier to be the least common multiple. Since the operation is performed following the measurement of the time, it is possible to always maintain a constant development gap and obtain a stable image.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a two-component developing device to which the present invention is applied.

FIG. 2 is a side view showing an example of the gap measuring device of the present invention.

FIG. 3 is a plan view showing an example of the gap measuring device.

FIG. 4 is a graph showing the relationship between gap adjustment and measurement time.

FIG. 5 is a plan view showing an example of a gap adjusting mechanism of the present invention.

FIG. 6 is a side view showing a part of the gap adjusting mechanism.

FIG. 7 is an explanatory diagram showing the relationship between the gap measuring device and the gap adjusting mechanism.

[Explanation of symbols]

 1 Photoconductor 2 Developing Device 3 Developing Roller 11 Gap Measuring Device 12 Gap Measuring Device 20 Gap Adjusting Mechanism 23 Stepping Motor

Claims (4)

[Claims] 1. A developer carrying member facing a surface of an image carrying member on which an electrostatic latent image is formed is used to supply a developer to the surface,
In the image forming apparatus for developing the electrostatic latent image, a gap measuring device for measuring a developing gap between the image bearing member and the developer bearing member is provided outside an area of the image bearing member where an image is formed. An image forming apparatus characterized by being provided. 2. The image forming apparatus according to claim 1, wherein a minimum common multiple of a time required by the gap measuring device for one rotation of the developer carrier and a time required for one rotation of the image carrier. An image forming apparatus, characterized in that it measures the time. 3. The image forming apparatus according to claim 1, wherein a gap adjusting mechanism for adjusting a developing gap between the image carrier and the developer carrier is provided, and the gap adjusting mechanism has an adjusting width. An image forming apparatus, wherein an upper limit and a lower limit of are set. 4. The image forming apparatus according to claim 1, wherein the gap adjustment mechanism requires one rotation of the developer carrier of the gap measuring device and one rotation of the image carrier. An image forming apparatus which is operated following a measurement of a time corresponding to a least common multiple of time.