JPH01193878A - Image forming device - Google Patents

Abstract

PURPOSE:To detect toner concentrations with the same rotational frequency of developer agitating shafts by rotating plural developer agitating shafts with one rotation driving source between image forming processes at the time of full color development and rotating them in parallel with the development operation at the time of monochromatic development. CONSTITUTION:One rotation driving source 2 rotates developer agitating shafts 11-14 and developing sleeves 41-44 in plural developing devices 51-54. A rotational number control means 1 controls the rotational frequency of developer agitating shafts 11-14 to a preliminarily determined value between one image forming process and the next image forming process at the time of full color development and controls it to the preliminarily determined value in parallel with the development operation at the time of monochromatic development. Consequently, developer agitating shafts 11-14 are rotated with the preliminarily determined rotational frequency to detect toner concentrations between one image forming process and the next image forming process at the time of full color development and to detect them in parallel with development operation at the time of monochromatic development. Thus, L detecting sensors 16-19 having the same characteristic in plural developing device 51-54 measure toner concentrations in the same agitating state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in means for detecting the toner density of each of the plurality of developing devices in an image forming apparatus having a plurality of developing devices.

(Background of the Invention) The toner concentration in a developing device in a conventional image forming apparatus is detected while the developer is being stirred. The developer is stirred only when the developing sleeve rotates, and the number of rotations of the developer stirring shaft corresponds to the number of rotations of the developing sleeve.

Therefore, when the rotation speed of the developing sleeve changes, the rotation speed of the developer stirring shaft also changes. On the other hand, the sensor that detects the toner concentration (hereinafter referred to as the L detection sensor) is a sensor whose output voltage changes depending on the developer stirring state, that is, the rotation speed of the developer stirring shaft.

(Problems to be Solved by the Invention) However, the toner density detection means of the conventional image forming apparatus described above has the following problems.

In other words, the toner concentration can only be detected during the developing operation when the developing sleeve is rotating, and if the rotating speed of the developing sleeve differs for each developing device, the rotating speed of the developer stirring shaft will also change and the state of stirring of the developer will change. Because of this difference, the output voltage of the L detection sensor changes, and even if the toner density has not changed, it is detected as if it had changed. Therefore, an image forming apparatus is configured in which a single motor rotates a plurality of developing sleeves one by one, and the number of revolutions of each developing sleeve is varied according to each developing condition, and each developing device has the same characteristics. If a sensor is used, a problem arises in that the toner concentration cannot be detected accurately.

An object of the present invention is that one rotational drive source that rotates each developer stirring shaft and each developing sleeve of a plurality of developing devices rotates all of the plurality of developer stirring shafts once during full color development.
By rotating at a predetermined number of rotations between an image forming step and the next image forming step, and rotating at the predetermined number of rotations in parallel with the development operation during monochrome development, It is an object of the present invention to provide an image forming apparatus in which toner concentration is detected at the same developer stirring shaft rotation speed even if the rotation speed of each developing sleeve is different.

(Means for Solving the Problems) The image forming apparatus of the present invention has the following means configuration to achieve the above object.

That is, the image forming apparatus of the present invention includes a plurality of developing devices and:
one rotational drive source that rotates the developer stirring shaft and the developing sleeve of each developing device; the number of rotations of all of the plurality of developer stirring shafts is adjusted between one image forming process and the next image forming process during full color development; and a rotational speed control means for controlling the rotational speed to a predetermined rotational speed during monochrome development, and controlling the rotational speed to the predetermined rotational speed in parallel with the development operation during monochrome development. It is.

(Function) The function of the image forming apparatus of the present invention having the above means configuration will be explained below.

In the image forming apparatus of the present invention, the zero rotation speed control means for causing one rotary drive source to rotate the developer stirring shaft and the developing sleeve of each of the plurality of developing units controls the rotation speed of the developer stirring shaft. During full-color development, the rotational speed is controlled to a predetermined number between one image forming process and the next image forming process, and during monochrome development, the rotational speed is controlled to the predetermined rotational speed in parallel with the development operation. . Therefore, during full color development, the toner concentration is detected while the developer stirring shafts of all developing devices are rotating at a predetermined number of revolutions between one image forming process and the next image forming process, and during monochrome development, the toner concentration is detected. In parallel with the development operation, the toner concentration is detected while the developer stirring shaft is rotating at the predetermined rotation speed, so that the detection sensors of the multiple developing units have the same characteristics. The toner concentration can be measured with the same stirring condition.

As explained above, the image forming apparatus of the present invention rotates the developer agitating shaft and the developing sleeve of the developing device in parallel at a predetermined rotational drive speed suitable for toner concentration measurement when forming a monochrome image, thereby producing a full color image. During image formation, the developer stirring shafts of all the developing devices are rotated at the predetermined rotational drive speed during the time between one image forming step and the next image forming step, that is, the time when no developing device is performing development. Therefore, even if the rotation speed of each developing sleeve is different during full color development, the rotation speed of the developer stirring shaft can be the same when measuring toner concentration, and therefore each development sleeve can be rotated at the same speed. The toner concentration can be accurately measured by using an L detection sensor provided in the developing device that has the same characteristics.

(Example) An example of the image forming apparatus of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of an image forming apparatus of the present invention. In the figure, a Y toner developing device 51 that stores yellow toner (hereinafter abbreviated as Y toner), a C toner developing device 52 that stores cyan toner (hereinafter abbreviated as C toner), and a magenta toner (hereinafter abbreviated as C toner). The M toner developing device 53 that stores M toner (abbreviated as M toner) and the black toner developing device 54 that stores black toner have developer stirring shafts 11, 12, 13, and 14, respectively.

The four developer stirring shafts rotate in unison as a shaft 4 coupled to a motor 3 rotates.

The developing sleeves 41, 42, 43, and 44 of the Y toner developing device 51, the C toner developing device 52, the M toner developing device 53, and the black toner developing device 54 are connected to the clutches 21, 22, 23, and 44, respectively. 24 are connected one by one, the rotation of the shaft 4 is individually transmitted through each of the developing sleeve rotation shafts 31, 32, 33, and 34, and the sleeves rotate one by one.

During full color development, the control unit 1 sends a clutch operation signal 1 to connect only one of the four clutches.
0, and at the same time, the clutch is engaged and a rotation speed control signal is sent to the motor driver 2 at a predetermined rotation speed to rotate the developing sleeve, to which the rotation of the shaft 4 is transmitted, at a predetermined rotation speed. do. As a result, the clutch of motor 3 is in the engaged state! Only the developing sleeve to which the rotation of M4 is transmitted is rotated at a predetermined number of rotations. In this way, while each of the four developing sleeves rotates one at a time, all developer stirring shafts are rotated at a number of revolutions corresponding to the number of revolutions of each developing sleeve. In this state, the toner detection sensors 16, 17, 18, and 19 do not detect toner density. Between one image forming process and the next image forming process, the control unit 1 closes all four clutches. At the same time as outputting the clutch operation signal 10 for releasing the clutch,
A rotation speed control signal is sent to the motor driver 2 to rotate the developer stirring shaft at a predetermined rotation speed suitable for measuring toner concentration. As a result, the motor 3 rotates only the four developer stirring shafts at the predetermined rotation speed, and the L detection sensors 16, 17, 18, and 19 monitor the toner concentration of each developer during this time. To detect.

During monochromatic development, the control unit 1 performs a developing operation) outputs a clutch operation signal 10 that connects the clutch corresponding only to the developing sleeve, and rotates the four developer stirring shafts at the predetermined rotation speed. A rotation speed control command for rotating the clutch is sent to the motor driver 2 at the same time as the clutch operation signal 10 described above. As a result, the motor 3 rotates the four developer stirring shafts at the predetermined number of rotations, and rotates only the developing sleeve that performs the developing operation.

The L detection sensors 16, 17, 18, and 19 detect the toner density while this developing operation is in progress.

(Effects of the Invention) As explained above, the image forming apparatus of the present invention rotates the developer stirring shaft of the corresponding developing device and the developing sleeve in parallel at a predetermined rotational drive speed suitable for toner concentration measurement when forming a monochrome image. When forming a full-color image, the developer stirring shafts of all the developing devices are rotated at the predetermined speed during the time between one image forming process and the next image forming process, that is, the time when no developing device is performing development. Since it is rotated at the driving speed, even if the rotation speed of each developing sleeve is different during full color development, the rotation speed of the developer stirring shaft should be the same when measuring toner concentration. Therefore, there is an advantage that the toner concentration can be accurately measured by using a detection sensor provided in each developing unit and having the same characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of an image forming apparatus according to the present invention. 1... Control unit, 2... Motor driver, 3... Motor, 4... Axis,
10...Clutch operation signal, 11,12,1
3.14...Developer stirring shaft, 16.17, 18.
19... L detection sensor, 21, 22, 23.2
4...Clutch, 31.32, 33.34...
...Developing sleeve rotation axis, 41.42.43.44
...Development sleeve, 51...Y toner developer, 52...C toner developer, 53.
...M toner developer, 54...Black toner developer. Agent Patent Attorney Yoshihiro Hachiman

Claims (1)

[Claims] a plurality of developing units; one rotational drive source that rotates the developer stirring shaft and the developing sleeve of each of the developing units; and a rotation speed of all the plurality of developer stirring shafts set to 1 during full color development.
a rotational speed control means that controls the rotational speed to a predetermined rotational speed between an image forming step and the next image forming step, and controls the rotational speed to the predetermined rotational speed during monochrome development in parallel with the developing operation; An image forming apparatus comprising: