JPH03172876A - Developing device - Google Patents

Abstract

PURPOSE:To accurately detect toner concentration by providing a heating device to a member for holding a toner concentration sensor and preventing the detection characteristic or the detected value of the toner concentration sensor from being influenced by temperature change. CONSTITUTION:When a main switch which is not shown in figure is turned on, the startup of respective parts necessary for development is executed and a heater 6 is turned on simultaneously with the startup. The energizing time of the heater 6 is set at a proper rate and the startup of the temperature of the bottom side part 1a of a developing device 1 is finished by the time when the startup of the respective parts is completed. Then, a thermistor 5 measures the temperature of the bottom side part 1a of the device 1 and the energizing time of the heater 6 is controlled by a CPU 8 in accordance with the measured value. Thus, the detection characteristic or the detected value of the toner concentration sensor is prevented from being influenced by the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device used in electrophotographic recording devices such as copying machines, printers, and facsimiles.

[Conventional technology]

FIG. 6 is a configuration diagram of a conventional developing device, in which 20 is a photosensitive drum, 21 is a developing device, 22 is a developing roller provided in the developing device 21, and 23 is a paddle provided in the developing device 21. 24 is a pre-transfer exposure lamp, 25 is a transfer device, 26 is a registration roller, and 27 is a toner density sensor provided on the bottom side of the developing device 21.

In the figure, a developer containing toner contained in a developing device 21 causes a paddle roller 23 to move as is known in the art. By the operation of the developing roller 22, the latent image on the photosensitive drum 20 is visualized, and the developed image is transferred by the transfer device 25 onto the transfer paper conveyed by the registration rollers 26.

The toner concentration sensor 27 detects the toner concentration of the developer and outputs a signal for making the toner concentration constant to a control section (not shown). However, in order to avoid erroneous detection due to the developer staying in the developing device 21, the toner concentration sensor 27 is always turned on. It is installed at a position where the developer flows, that is, at the bottom plate of the developing device 21 and between the developing roller 22 and the paddle roller 23.

[Problem to be solved by the invention]

In the above conventional technology, the detection output voltage of the toner concentration sensor 27 that is sensitive to the amount of magnetic material in the developer exhibits temperature dependence, and as shown in the explanatory diagram in FIG. 7, the sensor output increases as the toner concentration increases. When the temperature decreases and the temperature rises, the detection output decreases.

Incidentally, it has been found that the temperature characteristics of the toner concentration sensor 27 are correlated with the temperature of the bottom plate portion of the developing device 21 in which the toner concentration sensor 27 is installed. The reason is,
This is because since the material of the bottom plate is a metal such as aluminum, the temperature including the toner concentration sensor 27 is almost uniform due to its thermal conductivity.

However, the bottom plate portion of the developing device 21 is not necessarily in good condition in terms of temperature fluctuations. The reason for this is that a pre-transfer exposure lamp 24 is installed directly below the bottom plate of the developing device 21 as shown in FIG. 6, and this pre-transfer exposure lamp 24 serves as a heat source to raise the temperature of the bottom plate. Put it away,
Furthermore, the heater inside the photosensitive drum 20 or the power supply unit causes the temperature of the bottom plate to rise. Furthermore, when the developing device is continuously operated, the kinetic energy of the developer is converted into thermal energy, and the bottom plate is heated. This has a direct effect on the temperature rise in the area.

As described above, the temperature around the toner concentration sensor 27 tends to become heated, and there is a problem in that the toner concentration cannot be accurately detected by the toner concentration sensor 27 due to the influence of temperature changes.

An object of the present invention is to provide a developing device that can accurately detect toner concentration.

[Means to solve the problem]

In a developing device that includes a toner concentration sensor and detects the toner concentration of the developer using the toner concentration sensor, a heating means is provided on a holding member of the toner concentration sensor,
Alternatively, this can be achieved by a configuration that performs temperature correction on the toner concentration detection value from the toner concentration sensor based on the temperature around the toner concentration sensor.

[Effect]

The heating means can maintain the toner concentration sensor at a constant temperature via the holding member, stabilize the toner concentration detection characteristics, and perform temperature correction on the toner concentration detection value based on the temperature around the toner concentration sensor. Eliminates the effects of temperature changes in concentration detection.

〔Example〕

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

FIG. 1 is a configuration diagram showing a first embodiment of a developing device of the present invention, in which 1 is a developing device, 2 is a developing roller, 3 is a paddle roller, 4 is a toner concentration sensor, 5 is a thermistor, and 6 is a heating device. 7 is Ilo (input/output interface), 8 is CPU (central processing unit), 9 and 10
are the RAM and ROM of the storage device, and the toner concentration sensor 4 and the thermistor 5. The heater 6 is provided on the bottom side (holding member) la of the developing device 1.

In the figure, when a main switch (not shown) is turned on, the various parts necessary for development are started up, and at the same time, the heater 6 is turned on.

The energization time of the heater 6 is set at an appropriate rate, and the temperature of the bottom side portion 1a of the developing device 1 has been raised by the time the startup of each part is completed. Thermistor 5
measures the temperature of the bottom side portion 1a of the developing device 1, and the CPU 8 controls the energization time of the heater 6 according to this measured value.

If the control temperature of the bottom side part 1a of the developing device 1 is based on the temperature under the worst condition without temperature control, then the temperature of the bottom side part 1a of the developing device 1 in the operating state exceeds the control temperature and cannot be controlled. This problem will no longer occur.

FIG. 2 is a flowchart showing the temperature control of the bottom side portion 1a of the first embodiment, in which the main switch is turned on (step 1-1), and the temperature detected by the thermistor 5 is set to T.
If it is larger than 0 (Y in step 1-2), the heater 6 will not turn on, but if it is smaller than the set value T, the heater 6 will not turn on (Y in step 1-2).
2N), the heater 6 heats the bottom side 1a of the developing device 1 (step 1-3), and the heater 6 continues heating until the thermistor 5 detects that the set value T0 has been reached. (Step 1-4).

By configuring as described above, toner concentration sensor 4
The temperature of the bottom side portion 1a of the developing device 1, which is a holding member that holds the toner, is kept constant so as not to be influenced by external factors, and the detection characteristics of the toner concentration sensor 4 are stabilized.

FIG. 3 is a block diagram showing a second embodiment of the developing device of the present invention, in which members corresponding to those described in the first embodiment of FIG. 1 are given the same reference numerals.

In the figure, the configuration differs from the first embodiment in that it does not include a heater 6 as a heating means.

FIG. 4 is a block diagram showing the control system of the second embodiment, in which 4 is a toner concentration sensor, 5 is a thermistor, and 11 is an A/
D (analog/digital) converter, 12 is CPU (
The toner density sensor 4 and thermistor 5 are held at the bottom side 1a of the developing device 1 as shown in FIG.

In FIG. 4, the toner concentration detected by the toner concentration sensor 4 and the temperature value of the bottom side portion 1a of the thermistor 5 are A/
It enters the CPUI 2 via the D converter 11, and the detected toner concentration value is corrected based on the temperature value.

FIG. 5 is a flowchart showing the operation of the control system of the CPU in FIG. ), the temperature T of the bottom side portion 1a of the developing device 1 is detected by the thermistor 5 (step 2-3), and the toner concentration of the developer is detected by the toner concentration sensor 4, and the toner concentration detection value V7 is detected. is output (step 24). Here, the preset reference temperature T0 and the temperature T at the time of toner concentration detection are compared, and the toner concentration detection value (7) is corrected based on this.

In other words, using f as a coefficient, the CPU 2 calculates v=v, +f (T-T,) (step 2-5), treats the calculated value V as the toner concentration detection value, and calculates the toner concentration due to temperature change. The toner density value ■ is set in advance by correcting the variation in the detected value vT. If V > VO (Y in step 2-6), toner is replenished based on the values of V and -V (step 2-7), and if V≦v0, toner is replenished. (Step 2-8).

The above operation continues until copying stops (N in step 2-9), and when copying stops (Y in step 2-9), control of each part of the copying operation is turned off (step 2-10).
).

Note that as the reference temperature T0, either of the following can be selected: (1) the temperature at the initial setting of the toner concentration sensor 4, (2) a preset temperature such as the average temperature during operation, and in the case of (3), the initial value is corrected. Since it is not a value but a true value, it is highly reliable.In the case of ■, by knowing the actual operating temperature empirically, the closer the temperature is to this, the less the correction amount will be and the correction accuracy will increase. become.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the detection characteristics of the toner concentration sensor or the detected value from being affected by temperature changes, thereby providing a developing device that can accurately detect toner concentration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of a developing device according to the present invention, FIG. 2 is a flowchart showing temperature control in the embodiment of FIG. 1, and FIG. 3 is a second embodiment of a developing device according to the present invention. FIG. 4 is a block diagram showing the control system of the second embodiment of the present invention, FIG. 5 is a flowchart showing the operation of the control system in FIG. 4, and FIG. 6 is the configuration of a conventional developing device. Figure, 7th
The figure is an explanatory diagram showing the characteristics of the toner concentration sensor. 1...Developing device, 1a...Holding member, 4...Toner concentration sensor, 5...Thermistor, 6...Heating means, 8°12...CPU. 0 Figure 2 Figure 5 Etobetsu defeated Nto 41E destroyed (>)

Claims (2)

[Claims] (1) A developing device that includes a toner concentration sensor and detects the toner concentration of a developer using the toner concentration sensor, characterized in that a heating means is provided on a holding member of the toner concentration sensor. (2) In a developing device that has a toner concentration sensor and detects the toner concentration of the developer using the toner concentration sensor, temperature correction is performed based on the temperature around the toner concentration sensor for the toner concentration detected value from the toner concentration sensor. A developing device characterized by performing the following.