JPH0362070A - developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to a developing device using a two-component developer used in an image forming apparatus using electrophotography or electrostatic recording, and more specifically, a detection device for detecting developer concentration. This invention relates to a developing device that prevents developer from adhering to the detection window at the tip of the detection head.

In general, a two-component developer used in a developing device of an image forming apparatus using electrophotography or electrostatic recording has toner and carrier as its main components. The mixing ratio of toner and carrier in this developer is called developer concentration, and is an extremely important factor for stabilizing image quality. The developer toner is consumed during development, and the developer concentration changes. The developer concentration detection device detects the developer concentration at appropriate times, replenishes toner according to changes in the developer concentration, controls the developer concentration to be constant, and maintains image quality.

Here, a developer concentration detection device in a conventional developing device will be explained. FIG. 5 is a sectional view showing a developer concentration detection device in a conventional developing device.

In the figure, reference numeral 21 denotes a developing sleeve provided in the developing container 20 of the developing device, and a developing device side detection head portion 30 of a developer concentration detecting device is provided on the developing sleeve 21. An external detection unit 40 attached to the outside of the developing device is provided in contact. External detection unit 40
The white light from the light source 42 attached to the side plate 41 of
The light passes through the optical fiber 32 of the detection head section 30 and is reflected by the reflection mirror 32, and illuminates the developer concentration detection window 33.

The detection window 33 is provided with a guichroic mirror 35, which allows only near-infrared light, which is a long wavelength component of the white light, to pass through, with a wavelength of 700 nm as the boundary. The near-infrared light that has passed through the detection window 33 is reflected by the toner in the developer 26 on the developing sleeve 21, passes through the detection window 33 again, and is guided to the optical fiber 34 together with the visible light of the short wavelength component reflected by the mirror 35. , side plate 4
The light passes through the opening 43 of No. 1 and the color separation filter 44 and enters the light receiving element 45 of the silicon photodiode.

The color separation filter 44 has two pieces: an infrared transmission filter 47 that passes light with a wavelength of 700 nm or more and a visible transmission filter 48 that passes light with a wavelength of 700 nm or more.
The wavelengths of the light entering the light receiving element 45 are separated by this. The light that has passed through the infrared transmission filter 47 is photoelectrically converted by the light receiving element 45 and becomes a signal corresponding to the toner concentration in the developer 26 (hereinafter referred to as a concentration signal), and the light that has passed through the visible transmission filter 48 is also The signal is photoelectrically converted and becomes a signal (hereinafter referred to as a reference signal) for detecting deterioration of the light source 42 and dirt on the detection optical system.

In a developer concentration control device (not shown), these signals are A/D converted by an A/D converter as shown in FIG. 7, and then processed by the algorithm shown in the figure. The explanation is below.

After A/D conversion, an arithmetic circuit performs an operation to subtract a reference signal from the density signal. The density signal minus the reference signal is called the replenishment signal.

Replenishment signal = Density signal - Reference signal The initial value of the replenishment signal in the initial state of the developer is stored in memory as the threshold for toner replenishment, and when the toner is consumed and the density signal becomes small, the replenishment signal reaches the threshold. When the value becomes smaller than the initial value, the comparison circuit outputs a toner replenishment signal corresponding to the difference between the replenishment signal and the initial value. When toner is replenished into the developer in the developer container by the output of this toner replenishment signal, the concentration of the developer becomes high (and the concentration signal also becomes large), and the toner remains until the replenishment signal falls below the initial value again. Replenishment is not performed.As the toner is consumed and the density signal becomes smaller, toner is replenished accordingly to keep the developer concentration constant.

As described above, even if there is no change in the developer concentration, the density signal changes even if the intensity of the light source changes or if the optical system becomes dirty and the optical path is obstructed. As a countermeasure to this problem, there is a reference signal that monitors changes in the optical system regardless of the developer concentration. As mentioned above, if the density signal changes due to something other than a change in toner density, the reference signal will also change accordingly, so the replenishment signal, which is the difference between the density signal and the reference signal, will not be affected, and therefore the toner will change. Accidental replenishment is prevented.

As described above, stable developer concentration control is performed that is not affected by abnormalities in the optical system.

However, the conventional developer concentration detection device described above has the following problems.

FIG. 6 is a sectional view showing a detection section of the developer concentration detection device shown in FIG. 5. FIG. Developer 26 housed in developer container 20
comprises toner and carrier, and small toner particles are attached around large carrier particles by electrostatic force and are moved in the rotational direction 24 of the developing sleeve 21 while being attracted to the magnet roller 22. However, at the same time, the detection window 33 also has a gap between the detection surface 33a and the toner particles.
Alternatively, since electrostatic force also acts between the detection surface 33a and the carrier particles, toner and carrier may also adhere to the detection surface 33a.

At this time, the detection surface 33a detects the developer concentration based on the reflection density of the toner, so when toner adheres, the near-infrared light of the detection light is reflected more than the actual amount, and conversely, when the carrier adheres, the near-infrared light is reflected less than the actual amount. It is reflected and shifts the density signal from its actual value.

As a measure to prevent the phenomenon in which toner particles are separated from carrier particles and adhere to the detection surface 33a of the detection window 33, there is a method of providing a portion for forming a developer reservoir on the downstream side in the direction of developer movement (Japanese Patent Laid-Open No. 178276/1983). No. 3) is known, but it has the disadvantage that it is not possible to easily and reliably prevent the carrier from adhering to the detection surface 33a.

Therefore, an object of the present invention is to detect the developer concentration with high accuracy by easily and reliably preventing the adhesion of the carrier of the two-component developer to the detection surface of the detection window of the developer concentration detection device. Another object of the present invention is to provide a developing device that can maintain a constant developer concentration and perform good development by properly replenishing toner.

・To obtain 2 The above object is achieved by the developing device of the present invention.

To summarize, the present invention provides a developing device equipped with a developer concentration detecting device that detects the concentration of a developer having toner and carrier carried on a developing sleeve having a built-in magnet through a detection window of a detection head. , the developer has a volume average particle size of the toner of 10 LLm or less, a weight average particle size of the carrier of 30 to 80 μm, and a detection portion facing the developer of the detection window that is slidable on the developer. The amount of charge when rubbed is 200 to 500 V in absolute value with the same polarity as the charge on the toner, and the vertical force of the force exerted on the developer at the detection position opposite to the detection surface by the magnetic field of the magnet. The developing device is characterized in that the component is 2°0×10 −a newton or more. According to one aspect of the present invention, a developer regulating member is provided protruding around the detection window, and the amount of protrusion of the developer regulating member is changed, so that the sliding of the developer on the detection surface is prevented. The amount of charge is regulated. According to another aspect of the present invention, the amount of charge caused by the sliding of the developer on the detection surface is regulated by changing the angle of the detection surface with respect to the developing sleeve.

Kento Todoroki Examples of the present invention will be described in detail below.

FIG. 1 is a sectional view showing a detection section of a developer concentration detection device in an embodiment of the developing device of the present invention, and FIG. 2 is an enlarged view of the detection section.

The basic configuration of the developer concentration detecting device in the developing device of the present invention is the same as the developer concentration detecting device in the conventional developing device shown in FIG. At the lower end, two-component developer 26. on the developing sleeve 21 is passed through near-infrared light. A detection window 33 equipped with a guichroic mirror 35 for irradiating the light and receiving the reflected light is similarly provided.

According to the present invention, the detection window 3 at the lower end of the detection head section 30
A developer regulating member 54 is provided around 3 and protrudes toward the developing sleeve 21 installed in the developing container 20 of the developing device. This developer regulating member 54 controls the detection surface 3 of the detection window 33 by the two-component developer 26 on the developing sleeve 21.
This is to control the amount of charge on the detection surface 33a by controlling the sliding of the detection surface 33a, thereby preventing the developer 26 from adhering to the detection surface 33a. According to the present invention, the regulating member 5
4, the amount of charge on the detection surface 33a is 200 to 500 in absolute value with the same polarity as the charge polarity of the developer 26.
Regulated by V.

In this embodiment, the diameter of the developing sleeve 21 is 32 mm, the distance between the detection surface 33a of the detection window 33 and the sleeve 2j is 4 mm, and the size of the detection surface 33a in the same direction as the developer movement direction 24 is 10 mm. The amount of protrusion of the regulating member 54 is 0.
It is assumed to be 5mm. The detection surface 33a is positioned perpendicular to the line 25 connecting its center point and the center point of the sleeve 21. Further, the gap between the developer coating amount regulating plate 23 and the sleeve 21 is 800 tLm.

According to the present invention, in order to prevent the developer 26 from adhering to the detection surface 33a, the magnetic field of the magnet roller 22 in the developing sleeve 21 is applied to the detection surface of the sleeve 21 corresponding to the detection surface 33a of the detection window 33. position, the vertical component Fr of the force exerted on the carrier particles in the developer 26 is 2.0X1
0-" newton or more. In this embodiment, the magnet roller 22 is composed of five poles, and the S1 pole of the developing pole = 1
000 Gauss as the maximum, and then counterclockwise the Nl pole =
450 Gauss, S2 pole = 800 Gauss, N2 pole = 550
By setting the magnetic force to Gauss and N3 pole = 700 Gauss, the vertical component Fr of the force exerted on the carrier particles in the developer 26 at the detection position on the sleeve 21 is 2.78X10-'
Considered to be Newton.

Preventing the developer 26 from adhering to the detection surface 33a of the detection window 33 of the detection device in the developing device of this embodiment will be further explained based on test examples.

Developing sleeve 2 incorporating the above magnet roller 22
1 was rotated to charge the detection surface 33a of the detection window 33.

At this time, the amount of protrusion of the developer regulating member 54 was varied, and changes in the amount of charge on the detection surface 33a and presence or absence of adhesion of the developer 26 to the detection surface 33a were examined. The detection surface 33a is made of a 1100 tL thick fluorocarbon resin sheet as a window material, as in the past.

The amount of charge on the detection surface 33a is measured as shown in FIG.
A jig 55 made of the same ABS resin as that used for the detection head section 30 and formed to be identical to the lower end of the detection head section 30.
The detection surface 33a made of the above-mentioned fluororesin sheet was set at , and the measurement was carried out using a surface electrometer 50 and its measurement probe 51. A grounded ground plate 52 for charging measurement with a thickness of 0.2 mm is provided on the surface of the detection surface 33a opposite to the measurement probe 51, and the measurement probe 51 is connected to the detection surface 33a with a small gap of 0.5 mm or less. Then, the amount of charge on the detection surface 33a was measured.

As the two-component developer 26, a mixture of a polyester-based 1-ner and a ferrite-based carrier was stirred and mixed.

The toner used had a volume average particle diameter of 10 μm or less. The volume average particle diameter of toner particles is measured using Coulter Counter TA-II, an interface (manufactured by Nikkaki) that outputs the number average distribution and volume average distribution, and CX-
A personal computer (manufactured by Canon) was connected. The electrolytic solution for measurement was a 1% NaCl2 aqueous solution prepared using first grade sodium chloride.

Add 0.1 to 5 rnj2 of a surfactant, preferably an alkylbenzene sulfonate as a dispersant, to 100 to 150 m of the above Nacj2 aqueous solution, add the toner of the measurement sample, and mix with an ultrasonic disperser for about 1 to 3 minutes. Performed distributed processing. And 1100u by Coulter counter
Using the aperture, the particle size distribution of toner particles having a particle size of 2 to 40 LLm was determined, and then the volume average distribution was determined from the particle size distribution, and the volume average particle size was obtained from the volume average distribution.

The carrier is a ferrite particle (maximum magnetization 6
0 emu/g) was used. To measure the resistance value of the carrier particles, a sandwich type cell with a measuring electrode area of 4 crrr and an electrode spacing of 0.4 cm was used, and a voltage of E was applied between both electrodes under the condition that a pressure of 1 kg was applied to one electrode. (V/cm) was applied to obtain the resistance value of the carrier particles from the current flowing through the circuit.

By rotating the developing sleeve 21 at a circumferential speed of 280 mm/min, the detection surface 3 made of a fluororesin sheet is rotated.
3a was charged.

As a result, the height of the portion of the developer regulating member 54 upstream of the detection window 33 in the developer movement direction 24 is set to 0.2 to 0.7 mm.
By changing this, a charge amount of about -1200 to -50V was obtained on the detection surface 33a made of a fluororesin sheet.

A specified amount of charge can be obtained between 0.35 and 0.50 mm, and at that time, neither toner nor carrier adheres to the detection surface 33a, and the output density signal value is stable. Ta. The height of the upstream portion of the regulating member 54 is 0.35
When the amount of charge on the detection surface 33a is lower than 150 mm, the amount of charge on the detection surface 33a is
0V was exceeded, carriers adhered to the detection surface 33a, and the output concentration signal value decreased.

Further, when the height of the upstream side portion of the regulating member 54 is higher than 0.50 mm, the amount of charge on the detection surface 33a decreases, toner adheres to the detection surface 33a, and the output density signal value increases. Then I left.

Furthermore, even if the material of the window material constituting the detection surface 33a is changed, even if the initial toner concentration of the developer 26 is changed, or even if the characteristics of the developer 26 itself are changed, the amount of charge on the detection surface 33a will change. is within the specified value, the detection surface 33a
The developer 26 such as toner did not adhere to the toner. In addition, the magnetic cover pattern of the magnet roller 22 is changed to increase the force exerted on the carrier particles by the magnetic field at the detection position by 8.5×.
When the pressure was set to 10-9 Newton, the detection surface 3 of the carrier
The movement at the location 3a became slow, and as the developing sleeve 21 continued to rub, the carrier remained stuck to the detection surface 33a and did not move. This is because the binding force of the carrier particles became weak due to the weakening of the magnetic force, and as a result, adhesion occurred due to charging on the detection surface 33a, resulting in erroneous detection of concentration.

Although the peripheral speed of the developing sleeve 21 during rotation was set to 280 mm/min, the amount of charge on the detection surface 33a of the detection window 33 of the detection device and the charge saturation time depend on the peripheral speed of the developing sleeve 21. At 280mm/min, the detection surface 33 is reached in about 10 minutes.
The charge on a was saturated. The circumferential speed of this developing sleeve 21 is 2
By setting the speed to 10 mm/min, both the rise in charge and the saturation charge amount of the detection surface 33a were reduced by about 15%.

Although the circumferential speed of the developing sleeve 21 cannot be changed drastically because it greatly affects the developing performance, by changing it, it was possible to control the amount of charge on the detection surface 33a.

If the amount of charge on the detection surface 33a was within the specified value, the developer 26 did not adhere to the detection surface 33a even if the circumferential speed of the developing sleeve 21 was changed.

FIG. 4 is a sectional view showing a detection section of a developer concentration detection device in another embodiment of the developing device of the present invention.

In this embodiment, instead of providing a developer regulating member in the detection window 33 at the lower end of the detection head section 30 of the detection device, the detection surface 33
The angle θ of a with respect to the developing sleeve 21 (the angle with respect to the line 25 connecting the center point of the detection surface 33a and the center point of the sleeve 21) is determined by It is characterized in that the amount of charge on the detection surface 33a is regulated by increasing the amount of charge on the detection surface 33a.

Even with the change in the angle θ of the detection surface 33a as described above,
By controlling the sliding of the developer 26 on the developing sleeve 21 on the detection surface 33a, the amount of charge on the detection surface 33a can be regulated within a specified value.
The concentration of the developer 26 can be detected without erroneous detection.

As explained above, in the developing device of the present invention, toner having a volume average particle diameter of 10 μm or less and toner having a weight average particle diameter of 30 to 80 μm are used.
By means such as providing a developer regulating member in the detection window of a detection device that detects the concentration of developer having a carrier of m, the amount of charge when rubbed by the developer on the detection surface of the detection window is determined.
The absolute value is regulated to 200 to 500 V with the same polarity as the toner charge, and the vertical component of the force exerted on the developer facing the detection surface by the magnetic field of the magnet in the developing sleeve is 2.0 V.
Since it is set to X10-'' newtons or more, it is possible to easily and reliably prevent developer carriers from adhering to the detection surface, allowing the detection device to accurately detect the developer concentration.

Therefore, good development can be achieved by keeping the developer concentration constant by replenishing toner with the toner replenishing device.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a detecting section of a developer concentration detecting device in an embodiment of the developing device of the present invention. FIG. 2 is also an enlarged view of the detection section. FIG. 3 is an explanatory diagram showing a method of measuring the amount of charge on the detection surface provided in the detection window of the detection unit shown in FIGS. 1 and 2. FIG. FIG. 4 is a sectional view showing a detection section of a developer concentration detection device in another embodiment of the developing device of the present invention. FIG. 5 is a sectional view showing a developer concentration detection device in a conventional developing device. FIG. 6 is a sectional view showing the detection section of the detection device of FIG. 5. FIG. 7 is a block diagram showing signal processing of the developer concentration control device in the developing device of FIG. 21: Developing sleeve 22: Magnet roller 26 2 Two-component developer 30: Detection head section 33: Detection window 54: Developer regulating member Fig. 0 Fig. 2 5 Fig. 3 Fig. 5 Fig. 4 Fig. 6 Fig. 7 Figure 5 No Iris No. 48 @

Claims (1)

[Claims] 1) In a developing device equipped with a developer concentration detection device that detects the concentration of a developer having toner and carrier carried on a developing sleeve incorporating a magnet through a detection window of a detection head section. , the developer has a volume average particle size of the toner of 10 μm or less, a weight average particle size of the carrier of 30 to 80 μm, and a detection surface of the detection window facing the developer that is rubbed on the developer. The amount of charge when rubbed is 200 to 500 in absolute value with the same polarity as the charge of the toner.
V, and a vertical component of a force exerted on the developer at a detection position opposite to the detection surface by the magnetic field of the magnet is 2.0×10^-^3 newtons or more. . 2) A developer regulating member is provided protruding around the detection window, and the amount of charge caused by the sliding of the developer on the detection surface is controlled by varying the amount of protrusion of the developer regulating member. Developing device according to item 1. 3) The developing device according to claim 1, wherein the amount of charge caused by the sliding of the developer on the detection surface is regulated by changing the angle of the detection surface with respect to the developing sleeve.