JP3096998B2 - Color recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color recording apparatus having a plurality of developing units.

[0002] Electrophotographic recording apparatuses are widely applied to copiers, laser printers, laser facsimile machines, and the like.
It is expected to spread further in the future. In the case of color recording, a plurality of developing devices are used.

[0003]

2. Description of the Related Art FIG. 11 is a side view showing an outline of the structure of a conventional color recording apparatus. In FIG. 11, reference numeral 1 denotes a photosensitive drum (image carrier) which rotates in the direction of an arrow. Around the photosensitive drum 1,
A charger 2, an exposure unit 3, and four developing units 4 _Y , 4 _M , 4 _c , which hold Y (yellow), M (magenta), C (cyan), and BK (black) developers, respectively. 4 _BK , a transfer unit 5, a static elimination lamp 6, and a cleaner 7 are arranged. Each developing device has a separation / contact mechanism. During development, only one of the four members contacts the photosensitive drum, and the other three members are separated.

[0004] Recording is performed in the following procedure. That is, for example, when an organic photoconductor is used as the photoconductor on the surface of the photosensitive drum 1, generally, the entire surface of the photosensitive drum 1 is negatively charged by the charger 2. Next, by irradiating the surface of the photosensitive drum 1 with an exposure device 3 in accordance with an image signal,
The charge of the exposed portion is reduced, and an electrostatic latent image is formed.
When the latent image area passes through the developing unit 4 _Y, Y-color toner image is formed toner negatively charged to adhere thereto.

On the other hand, a recording paper 100 on which an image is printed
Are supplied one by one by a sheet transport belt 8 to a position where the toner image contacts the toner image formed on the photosensitive drum 1.
The transfer device 5 is provided below the photosensitive drum 1 with the paper transport belt 8 and the recording paper 100 interposed therebetween, and is configured to apply a positive charge to the recording paper 100. Therefore, the toner image on the photosensitive drum 1 is attracted to the positive charge of the recording paper 100 and is transferred to the toner. The recording paper 100 after the transfer is returned to the original position by the paper transport belt 8.

Further, the surface of the photosensitive drum 1 on which the toner has been transferred onto the recording paper 100 is completely discharged by the discharge lamp 6 and is cleaned by the cleaner 7 to return to the initial state. This process is repeated in the developing units 4 _M , 4 _c , and 4 _BK . The recording paper 100 carrying the four color toner images is sandwiched between a heat roller 10 constituting the fixing device 9 and a rubber roller 11 which is pressed against and rotates, and the toner image is fixed on the recording paper 100 by heat and pressure. And is discharged out of the device. Although the above is the process of negative charging, the process of positive charging is the same.

[0007]

The developing units 4 _Y , 4 _M ,
FIG. 12 shows a state in which the photosensitive drum 1 is pressed against 4 _c , 4 _BK .
The photosensitive drum 1 rotates in the direction of the arrow, and the developing units 4 _Y , 4 _M , 4 _c , 4 _BK arranged in parallel around the photosensitive drum 1 are
As a result, the developer carrier 13 is pressed in the direction parallel to the horizontal line a passing through the axis of the photosensitive drum 1 at the same pressure F, so that each developer carrier 13 comes into pressure contact with the photosensitive drum 1. Further, the developer carriers 13 of the respective developing devices are all rotating in the same direction as indicated by arrows.

FIG. 13 shows the relationship between the pressure between the developer carrier 13 and the photosensitive drum 1 located at an angle θ from the horizontal line a. This developer carrier 13 is, as described above, horizontal line a
In a direction parallel to the direction of the arrow. If the friction coefficient between the photosensitive drum 1 and the developer carrier 13 is μ,
Friction force f due to rotation of developer carrier 13 in tangential line c direction
₁ = μFcosθ occurs.

Since the vector direction of f ₁ is negative, F and f
The vector direction of the resultant force of ₁ becomes upward, the force in the direction of the normal line b becomes unstable, and the pressing pressure of the developer carrier 13 against the photosensitive drum 1 becomes unstable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color recording apparatus capable of stabilizing the pressure of a developer carrier against an image carrier.

[0011]

In order to achieve the above object, the present invention provides an image carrier and a developer carrier for developing an electrostatic latent image on the image carrier. And a plurality of pressurizing means for pressing each of the developing devices toward the image carrier, wherein each of the developing devices includes the developer carrier. a spring for canceling the frictional force f ₁ by the rotation of the structure, characterized in that respectively (a first configuration).

In the color recording apparatus of the first configuration, the tension of the spring is f ₁ + f ₂ , the sum of the friction force f ₁ due to the rotation of the developer carrier and the force f ₂ of the spring, and the pressure of the pressing means. The configuration (second configuration) is characterized in that the resultant force of the pressure F is set to be in the direction of the normal line b of the contact portion between the image carrier and the developer carrier.

Also, an image carrier, a plurality of developing devices each having a developer carrier for developing an electrostatic latent image on the image carrier and containing developers of different colors, respectively, In a color recording apparatus comprising at least a plurality of pressurizing means for pressing the image bearing member, the rotation direction of the image carrier of each of the developing units is determined by the pressure F of the pressing means and the developer carrier. configuration vector direction of the resultant force of the frictional force f ₁ by the rotation of which is characterized in that which is set so as to approach the normal line direction b of the contact portion of the developer carrying member and said image bearing member (a third configuration) And

[0014]

[Action] For the first configuration, since it is canceled by the tension of the frictional force f ₁ spring by the rotation of the developer carrying member, the pressing pressure of the developer carrying member is stabilized with respect to the image bearing member. In the case of the second configuration, the tension of the spring, the developer frictional force caused by the rotation of the carrier f ₁ and the sum f ₁ of the spring force f ₂
Since the resultant force of + f ₂ and the pressure F of the pressurizing unit is set so as to be directed in the direction of the normal line b, the pressing pressure of the developer carrier becomes more stable.

In the case of the third configuration, the direction of rotation of the developer carrier of each developing unit is set such that the vector direction of the resultant force of F and f ₁ approaches the direction of the normal line b. The pressing pressure of the developer carrier becomes stable.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIGS. 1 to 3 show a first embodiment.

[0018] Figure 1 is a main structure diagram of the color recording apparatus of this example, in the _{figure, 21 Y, 21 M, 21} c, 21 BK each color developing units arranged in parallel around the photosensitive drum 1, Reference numerals 22 and 23 denote a developer carrier and a spring provided in each developing device. The spring 23 is provided between the shaft 22a of the developer carrier and the bottom plate 24 of the developing device, and urges the developer carrier 22 so as to cancel the frictional force due to its rotation. Next, this relationship will be described with reference to FIG.

FIG. 2 shows a horizontal line a passing through the axis of the photosensitive drum 1.
FIG. 9 is an explanatory view of the action of the spring on the developer carrier 22 located at an angle of θ from the angle A. In FIG. It is biased at a force of f ₂ by spring. Assuming that the friction coefficient between the photosensitive drum 1 and the developer carrier 22 is μ, a frictional force f ₁ = μFcos θ due to the rotation of the developer carrier 22 acts in the tangential line c direction, but this f ₁ is canceled by f _2. The photosensitive drum 1 and the developer carrier 2
2, the pressing pressure is stabilized.

The structure and operation of each developing device of this embodiment will be described below with reference to FIG. The photosensitive drum 1 is rotating clockwise as indicated by an arrow. The developer carrier 22 is composed of a solid rubber roller for conveying and developing the toner, and rotates counterclockwise as indicated by the arrow. When the horizontal line passing through the axis of the photosensitive drum 1 is set to 0 °, the developer carrying member 22 of each developing device contacts the photosensitive drum 1 at θ = ± 40 ° and ± 20 °, (Refer to FIG. 1), and is pressed in a direction parallel to the horizontal line a at a pressure of 900 gf. The coefficient of friction μ between the photosensitive drum 1 and the developer carrier 22 is 0.6
5

That is, the first developing unit 21 _Y has θ = 40
°, the second developing device 21 _M is θ = 20 °, and the third developing device 21 _c
Is located at a position of θ = −20 °, and the fourth developing device _21BK is disposed at a position of θ = −40 °. The developer carrier 22 has a diameter of 20 mm,
One end of the spring 23 was fixed at a point 15.66 mm rearward from a point vertically lowered from the axis of the developer carrying member on the bottom plate 24.
Similarly, the second developing device 21 _M posterior 4.37, the third developing unit 21 _c forward 4.37, fourth developing units 21 _BK was fixed to one end of the spring 23 to a point forward 15.66Mm.

The first developing device 21_YAnd the fourth developing device 21
_BKFrictional force f₁Is 448 gf and the second developing device 21_MAnd the second
3 developing unit 21_cFrictional force f₁Is 550 gf,
A spring 23 having the same tension as the frictional force was used. to this
From above, f₁And f _TwoAre canceled and each developing unit
, The pressing pressure of the developer carrier is stabilized.

FIG. 4 shows a second embodiment.

The structure and operation of each developing device of this embodiment will be described with reference to FIG. When the resultant force of tension of the tension f ₂ of the developing frictional force and pressure F by the pressure means in units f ₁ and the spring 23 is to face the normal direction b of the contact portions of the photosensitive drum 1 and the developer carrying member 22, The pressing pressure of the developer carrier 22 is further stabilized. This example realizes this.

For this purpose, F sin θ = − (f ₁ + f
It may be obtained with a made f _{2 2).} As a result, f ₂ was set in the following manner. That is, the developing unit 31 _Y in f ₂ =
1026Gf, the developing device 31 _M in f ₂ = 859gf, the developing unit 31 _c in f ₂ = 241gf, the developing unit 31 _BK in f
₂ = -130 gf. In the case of the fourth developing device _31BK , the direction of the tension of the spring 23 is opposite to that of the other developing devices.

FIG. 5 shows a third embodiment.

In the second embodiment, the pressures of the springs in the respective developing units are all different, but in the present embodiment, the developer carriers 2 of the developing units 41 _c and 41 _BK are limited so that the spring tension can be limited to two types.
The second rotational direction is the opposite to that of the developing unit 41 _Y, 41 _M. Accordingly, it provided the bottom plate 24 of the two developing units on top of the developing unit, the developing unit 41 _BK in the spring from a point down the developer heart perpendicularly carrier axis to the point of 15.66mm rear bottom plate 24 23 was fixed at one end. Similarly, the one end of the developing device 41 _c spring 23 rearward 4.37mm at fixed.

Thus, the developing device _41Y and the developing device _41BK
In spring tension f ₂ = 1026gf, it could decrease the developing device 41 _M a developing unit in 41 _c spring tension f ₂ = 859gf, and the spring tension into two types.

FIGS. 6 to 8 show a fourth embodiment.

FIG. 6 is a diagram for explaining the structure and operation of each developing device of this embodiment. In this embodiment, each developing device 51 _Y , 51 _M , 51 _c , 51 _BK arranged in parallel around the photosensitive drum 1 is illustrated. The rotation direction of the developer carrier 22 is reversed above and below the horizontal line a. That is, the first and second developing units 51 _Y and 5 on the horizontal line a
The rotation direction of the 1 _M developer carrier 22 is the same clockwise as that of the photosensitive drum 1 and the third and fourth developing devices 51 below the horizontal line a.
The rotation direction of the developer carrier 22 of _c , _51BK is counterclockwise.

FIG. 7 shows the relationship between the pressure between the developer carrier 22 and the photosensitive drum 1 located at an angle of θ from the horizontal line a when the rotation direction of the developer carrier is as described above. The developer carrier 22 is pressed by the pressing means 12 (see FIG. 6) in a direction parallel to the horizontal line a with a pressure of F. Assuming that the friction coefficient between the photosensitive drum 1 and the developer carrier 22 is μ, the frictional force f ₁ due to the rotation of the developer carrier 22 in the direction of the tangential line c =
μFcos θ occurs.

On the other hand, since the vector direction of f ₁ is positive,
The vector direction of the resultant force of F and f ₁ approaches the direction of the normal line b.
Thus, the pressure of the developer carrier 22 against the photosensitive drum 1 is stabilized. This will be described more specifically with reference to FIG.

As shown in FIG. 8, the first developing unit 51 _Y
= 40 °, the developer carrier 2
The rotation direction of No. 2 is the direction of the arrow, and the friction coefficient μ is 0.65.
When the frictional force f ₁ is its vector direction is a positive in 448Gf. The resultant force with F = 900 gf is 3 from normal b.
The pressure f _{2 is} 857 gf in the direction shifted by 6 °, and the pressure contact state is more stable than in the case of the related art in FIG. 13 in which the developer carrier rotates in the opposite direction.

The pressing positions of the developer carriers of the other developing units are set as follows: θ = 20 ° for the second developing unit, θ = −20 ° for the third developing unit, and θ = −40 for the fourth developing unit. In this case, in these cases, the vector direction of the resultant force is closer to the normal line than in the case of the related art in FIG. 13, and the pressure contact state of the developer carrier is stabilized.

FIGS. 9 and 10 show a fifth embodiment.

In the case of the fourth embodiment, the pressure F acting on the developer carrier of each developing device is constant at 900 gf. In this case, the resultant force f ₂ between F and f ₁ is not constant for each of the developing devices. This example is to make this constant. 9 configuration of each developing device of the present embodiment, in view illustrating the operation, the developing devices 61 _Y, 6
The arrangement of 1 _M , 61 _c and 61 _BK is as follows. That is, the pressure contact position of the developer carrier 22 of each developing device is θ = 4
0 °, θ = 20 °, θ = −20 °, and θ = −40 °.

When the pressure F of each developer carrier 22 of the developing devices 61 _Y and 61 _BK at θ = ± 40 ° F = 900 gf, the resultant force f
₂ = 857 gf. Developing device 6 with θ = ± 20 °
In order to make the resultant force f ₂ = 857 gf even at the position of 1 _M and 61 _c , the cosine theorem (857) ² = X ² + (μXcos 20 °) ² −
X may be obtained from 2X (μX cos 20 °) cos 70 ° (F
= X).

[0038] Figure 1 for the results, the second developing device 61 _M
0, F = 87 at the position of θ = ± 20 °.
By the 4 gf, it can be a f ₂ to 857Gf, the f ₂ becomes possible to a constant value at the positions of all of the developing unit.

[0039]

As described above, according to the present invention, the developer carrier can always be pressed against the image carrier with a stable pressure, which greatly contributes to the improvement of the print quality of the color recording apparatus. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part structure of a color recording apparatus according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of a spring according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating the configuration and operation of each developing device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating the configuration and operation of each developing device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating the configuration and operation of each developing device according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating the configuration and operation of each developing device according to a fourth embodiment of the present invention.

7 is a fourth embodiment of F, vector direction illustration of the resultant force of f ₁ of the present invention.

FIG. 8 is an explanatory diagram of a vector direction of f ₂ of a first developing device according to a fourth embodiment of the present invention.

FIG. 9 is a diagram illustrating the configuration and operation of each developing device according to a fifth embodiment of the present invention.

FIG. 10 is an explanatory diagram of a vector direction of f2 of a _second developing device according to a fifth embodiment of the present invention.

FIG. 11 is a side view showing a structural outline of a conventional color printing apparatus.

FIG. 12 is an explanatory diagram of a state in which each developing device and a photosensitive drum are in pressure contact with each other in the related art.

FIG. 13 is an explanatory view of a pressure between a conventional developer carrier and a photosensitive drum.

[Explanation of symbols]

First photosensitive drum (image bearing member) 12 pressing means _{21 Y ~21 BK, 31 Y ~31} BK, 41 Y ~41 BK, 5
_{1 Y ~51 BK, 61 Y ~61} BK developing unit 22 developer carrying member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-15578 (JP, A) JP-A-3-85564 (JP, A) JP-A-2-262672 (JP, A) JP-A 52-1982 130642 (JP, A) Hira 1-59250 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/08 -15/08 507

Claims (3)

(57) [Claims] 1. An image carrier, a plurality of developing devices each including a development re-carrier for developing an electrostatic latent image on the image carrier, and incorporating developers of different colors, respectively; in at least comprising a color recording apparatus and a plurality of pressing means, the pressing toward the image bearing member, wherein the developing units, provided a spring for canceling the frictional force f ₁ by the rotation of said developer carrying member, respectively A color recording device. 2. A color recording apparatus according to claim 1, wherein the tension of the spring, the sum f ₁ + f ₂ of the frictional force f ₁ and the spring force f ₂ due to the rotation of the developer carrying member, the pressure of the pressurizing means A color recording apparatus characterized in that the resultant force of F is set to be in the direction of the normal line b of the contact portion between the image carrier and the developer carrier. 3. An image carrier, a plurality of developing devices each including a developer carrier for developing an electrostatic latent image on the image carrier, and incorporating developers of different colors, respectively; In a color recording apparatus comprising at least a plurality of pressurizing means for pressing the image bearing member, the rotation direction of the developer carrier of each of the developing devices is determined by the pressure F of the pressing means and the developer carrying force. vector direction of the resultant force of the frictional force f ₁ by the rotation of the body, a color recording apparatus characterized by configured to be closer to the normal direction b of the contact portion of the developer carrying member and said image bearing member.