JP2700633B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is rotatably supported by an image forming apparatus main body,
An image bearing drum on the surface of which an electrostatic latent image is formed while being rotated, and a developing device for visualizing the electrostatic latent image as a toner image, the developing device comprising: a toner containing toner; A container, and a developing roller rotatably supported by the toner container and carrying the toner on the surface thereof while being rotated and driven, the developing roller being directly or another member on the surface of the image bearing drum. And an image forming apparatus that visualizes the electrostatic latent image with toner carried and conveyed on the surface of the developing roller.

2. Description of the Related Art An image forming apparatus of the above type configured as an electronic copying machine, a printer, a facsimile or the like has been conventionally known.

FIG. 9 is a schematic cross-sectional view showing one example, and the image forming apparatus shown here is configured as a copying machine including an image bearing drum configured as a photosensitive drum 1 and a developing device 2. . The photosensitive drum 1 is rotatably supported by the structure of the main body of the image forming apparatus but is not moved, and is rotated clockwise by a driving device (not shown). At this time, the surface is charged to a predetermined polarity, and a light image from the document is image-formed and projected by an image forming element (not shown) to form an electrostatic latent image on the surface of the photosensitive drum.

The electrostatic latent image is visualized as a toner image when passing through the developing device 2. The developing device 2 includes a toner container 3 containing toner, an agitator 4 for stirring the toner in the toner container, a developing roller 5, and a toner supply roller 6 for supplying toner to the toner container 3. , 5, and 6 are positioned parallel to the photosensitive drum 1 and are rotatably supported by the toner container 3, but are fixed to the toner container 3, and are respectively indicated by arrows in FIG. It is driven to rotate in the direction.

The toner supply roller 6 supplies toner to the developing roller 5, and the toner supplied to the surface of the roller 5 is regulated to a uniform thickness by a toner layer thickness regulating blade 7 to be thinned and has a predetermined polarity. It is triboelectrically charged.

Next, the toner is conveyed to the developing area where the photosensitive drum 1 and the developing roller 5 are pressed against each other with the rotation of the developing roller 5, where the toner is electrostatically transferred to an electrostatic latent image on the surface of the photosensitive drum 1. , The latent image is visualized.

As described above, the developing roller 5 rotatably supported by the toner container 3 holds and conveys the toner on the surface thereof while being rotationally driven, and directly presses against the surface of the image bearing drum including the photosensitive drum 1, The electrostatic latent image is visualized by the toner carried and conveyed on the surface of the developing roller 5. The developing roller can be pressed against the surface of the image bearing drum via another member.

The visible image formed on the photosensitive drum 1 is transferred to a transfer paper (not shown), and the toner remaining on the photosensitive drum 1 is cleaned by a cleaning device (not shown).

In the above-described image forming apparatus, the contact developing is performed by the developing roller 5 that is in pressure contact with the photosensitive drum 1.
In order to enhance the image quality of the visible image formed thereby, it is desirable that the developing roller 5 be pressed against the photosensitive drum as uniformly as possible over its entire length. For this purpose, the entire developing device 2 is supported so as to be movable (in the horizontal direction in the example of FIG. 9) in a direction approaching or separating from the photosensitive drum 1. That is, the outer side surfaces of the front side plate (not shown) and the rear side plate 8 in FIG.
Two guide rollers 9, 9 are rotatably supported, and these rollers 9, 9 are rotatably fitted into cutouts 10, 10 formed in the front and rear frame plates of the structure of the image forming apparatus main body. I agree. Pressurizing means including a compression spring 12 is provided between the toner container 3 and the structure 11 of the image forming apparatus main body, whereby the developing device 2 is urged toward the photosensitive drum 1.

As described above, the developing roller 5 and the toner container 3 supporting the developing roller 5 are supported so as to be movable toward or away from the photosensitive drum 1, and are pressed against the photosensitive drum 1 by the spring 12. For this reason, even if the outer peripheral surfaces of the developing roller 5 and the photosensitive drum 1 are slightly eccentric due to manufacturing errors and the like, and the surface thereof has some unevenness, the developing roller 5 is uniformly positioned with respect to the photosensitive drum 1. It is possible to make pressure contact. That is, the developing roller 5 can be constantly and uniformly pressed against the photosensitive drum 1 while swinging a small amount in the horizontal direction according to the unevenness or eccentricity of the surface of the developing roller 5 or the photosensitive drum 1. It is.

By the way, when the toner in the toner container 3 runs out, the developing device 2 is attached to the main body of the copying machine for the purpose of replacing the toner with a new developing device or performing maintenance and inspection of the developing device 2. It is supported so that it can be attached and detached. That is, to remove the developing device 2 shown in FIG.
By moving this to the right, the guide rollers 9, 9 are removed from the notches 10, 10, the developing device 2 is set in a free state, and the developing device 2 is detached from the image forming apparatus main body. By the reverse operation, the same developing device or another new developing device can be installed.

However, according to the image forming apparatus shown in FIG. 9, when removing the developing device 2, it is necessary to move the developing device 2 to the right to perform the removing operation, and the operability is poor. Developing device 2
The same is true when installing the horn. If the developing device 2 can be detached simply by lifting or lowering the developing device 2 from the state shown in FIG. 9, for example, upward or downward, the work can be performed easily and the operability can be improved. However, in the image forming apparatus shown in FIG.
9 is fitted in the notches 10 and 10 of the horizontally extending frame plate, so that the frame plate hinders the developing device 2 from being lifted upward.

When a new developing device is installed as shown in FIG. 9,
If the diameters and surface conditions of the guide rollers 9, 9 of the developing device and the guide rollers 9, 9 of the developing device used before are different due to manufacturing errors or the like, the former developing device 2 This causes a difference in the frictional force generated when the new developing device swings in the horizontal direction in FIG. For this reason, the force with which the developing roller of the previous developing device is in pressure contact with the photosensitive drum is different from the force with which the developing roller of the new developing device is in contact with the photosensitive drum, and the image quality of the visible image formed thereby changes. There is fear.

Further, in the configuration shown in FIG. 9, the spring 12 must be removed or attached each time the developing device 2 is attached or detached, so that the operation becomes very troublesome.

An image forming apparatus has been proposed in which the developing device is not supported by the guide rollers 9, 9 and the notches 10, 10, but the developing device is swingably supported via pins. There is a similar problem.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which can solve the above-mentioned conventional disadvantages at once.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an image forming apparatus of the type described at the outset, in which the developing device is detachably supported although it is not moved, and is moved toward or away from the surface of the image bearing drum. A developing device carrier supported by the image forming apparatus main body so as to be movable in a direction, and pressing means for urging the developing device carrier in a direction in which the developing roller is pressed against the surface of the image carrying drum. An image forming apparatus characterized by the following is proposed.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an exploded perspective view showing an example of a developing device 2 and an apparatus for supporting the developing device, and FIG. 2 is an explanatory view schematically showing an image forming apparatus in which these are assembled in an image forming apparatus main body. is there.

The basic structure and operation of the image forming apparatus shown in FIG. 2 are the same as those of the image forming apparatus shown in FIG. Then
The image forming apparatus shown in FIG. 2 is also rotatably supported by the main body of the image forming apparatus, and is rotatably driven to form an electrostatic latent image on the surface thereof. A developing device 2 for visualizing the electro-latent image as a toner image; the developing device 2 is rotatably supported by the toner container 3 containing the toner; A developing roller 5 that carries and transports the toner on the surface thereof; the developing roller 5 directly presses against the surface of the image bearing drum; Visualize the image. As described later, the developing roller 5 can be pressed against the surface of the image bearing drum via another member.

The toner container 3 in which the developing roller 5 that is driven to rotate counterclockwise is provided with a toner supply roller, an agitator, and a toner layer thickness regulating blade.
There is no difference from the image forming apparatus shown in the figure.

Here, the features of the image forming apparatus of the present embodiment are as follows.
The developing device 2 is supported by the image forming apparatus main body such that the developing device 2 is detachably supported although it is not moved, and is movable in a direction approaching or away from the surface of the image bearing drum composed of the photosensitive drum 1. The present invention is characterized in that a body 15 and a pressurizing means for urging the developing device carrier 15 in a direction in which the developing roller 5 is pressed against the surface of the image carrier drum are provided.

In the illustrated example, the entire developing device 2 is supported by a dish-shaped or bucket-shaped developing device carrier 15, and an appropriate number of positioning holes 16 are formed in the bottom plate of the developing device carrier 15,
A projection 17 protruding from the lower surface of the toner container of the developing device 2 is fitted to these. Therefore, in the state of FIG. 2 in which the projection 17 is fitted in the hole 16, the developing device 2 is
The developing device 2 can be detached from the developing device carrier 15 by lifting the developing device 2 upward. Thus, the developing device 2 is detachably supported by the developing device carrier 15.

On the other hand, the upper pins 18, 18a, 18b, 18c
The upper portions of the four ring plates 19, 19a, 19b, and 19c are pivotally connected to each other, and these plates extend as much as possible, and the lower portions of the four ring plates 19, 19a, 19b, and It is pivotally attached to brackets 21, 21a, 21b, 21c fixed to the structure 11. In this way, the developing device carrier 15, the link plates 19 and 19b; 19a and 19c, and the structure 11 constitute a four-node rotating chain, particularly a parallel movement mechanism. Therefore, the developing device carrier 15 can move to the image forming apparatus main body so as to move toward or away from the surface of the photosensitive drum 1 as shown by arrows A and B while holding the developing device 2 immovably. Supported.

Further, a compression spring 12, which is an example of the above-mentioned pressing means, is pressed between the back surface of the developing device carrier 15 and the structure 11, whereby the developing roller 15 is brought into contact with the photosensitive drum 1 by the developing device carrier 15. It is urged in the direction of pressing.

With the above configuration, as in the case of FIG. 9, even if the peripheral surfaces of the photosensitive drum 1 and the developing roller 5 are slightly eccentric, the parallelism thereof is slightly out of order, or the surface thereof has slight irregularities, Roller 5 responds to these irregularities by the arrow in FIG.
While swinging in the directions A and B, the roller 5 can be uniformly pressed against the photosensitive drum 1 over the entire longitudinal direction of the roller 5, and a visible image formed on the surface of the photosensitive drum 1 can be formed. Image quality can be improved. The swing stroke of the developing roller 5 is usually about 0.1 mm.

The spring 12 is provided, for example, at two symmetrical positions in the left-right direction of the developing device carrier 15 in FIG. 1 or at a central portion thereof to uniformly press the developing device carrier 15 left and right. Is desirable. As the pressing means, a pressing arm may be urged by a torsion coil spring in addition to a compression spring, and the arm may be pressed against the supporting member, or a leaf spring or the like may be used.

The developing device carrier 15 has a toner end detection sensor 22 for detecting that the toner in the developing device 2 has run out, and an input for applying a bias voltage to the developing roller 5 and the toner supply roller (see FIG. 9). A terminal 23 is provided.

Since the developing device 2 is detachably supported by the developing device carrier 15 as described above, when removing the developing device 2 from the image forming apparatus main body, the developing device 2 is lifted upward, Remove from body 15 and developing device 2
When attaching the developing device, it is only necessary to lower it downward and set it on the developing device carrier 15, and the operation is very simple. In this case, even if the sensor 22 and the terminal 23 are provided on the developing device carrier 15, the developing device 2 can be attached and detached without any hindrance. Of course, by appropriately changing the shape of the developing device carrier 15, etc., the developing device 2 can be configured to be attachable / detachable in an appropriate direction such as a direction perpendicular to the plane of FIG. The degree of freedom in design can be greatly increased as compared with the conventional case.

Further, since the spring 12 does not abut against the developing device 2 as in the related art, but presses the developing device carrier 15,
When the developing device 2 is attached or detached, there is no need to remove or attach the spring 12.

In addition, when the developing device 2 swings, the developing device itself does not receive the frictional force acting on the conventional guide rollers 9, 9 (FIG. 9), so that a new developing device is used. Even when the developing roller is set on the carrier 15, the developing roller of the new developing device can be pressed against the photosensitive drum 1 at the same pressure as the developing roller 5 of the previous developing device pressed against the photosensitive drum 1. A visible image of constant quality can always be obtained.

By supporting the developing device 2 in a detachable manner with respect to the developing device carrier 15, even if the developing device 2 is replaced, the developing device carrier 15 movable with respect to the photosensitive drum 1 is not replaced. Therefore, the pressing force of the developing roller 5 against the photosensitive drum 1 does not change, and an image of the same quality before and after the replacement of the developing device 2 can be formed on the surface of the photosensitive drum 1.

Further, since the terminal 23 and the sensor 22 are attached to the developing device carrier 15 that swings integrally with the developing device 2, the swing of the developing device is provided between the terminal 23 and the sensor 22 and the developing device 2. The sliding resistance does not act during the movement, so that the developing roller 5 and the photosensitive drum 1 can always be brought into pressure contact with a uniform pressure. In addition, poor contact between the terminal 23 or the sensor 22 and the developing device 2 can be prevented.

When the developing device 2 or the photosensitive drum 1 is removed from the image forming apparatus main body, the link plate 19 is brought into contact with the stoppers 24 and 25, and the developing device carrier 15 and the link plate move so as to interfere with other elements. Has been prevented.

When the developing device carrier 15 is supported via the link plates 19, 19a, 19b, and 19c as shown in FIGS. 1 and 2, the following excellent advantages can be obtained.

In order to make this advantage easy to understand, the problem caused by the conventional configuration illustrated in FIG. 9 will first be clarified.

FIG. 10 is an explanatory diagram schematically and more generally showing the configuration shown in FIG. In Figure 10, the photosensitive drum 1 is rotated by v _0, the developing roller 5 is assumed to rotate at v _1, and v is ₀ <v _1. For convenience of explanation, these rotation directions are opposite to those in FIG. 9, but they may be the same direction.

The developing device 2 has its own weight W acting thereon, and a guide roller
At points 9 and 9, reaction forces N ₁ and N ₂ are received. The force applied by the spring 12 to the developing device 2 is P, and the pressure applied from the photosensitive drum 1 to the developing roller 5 is F. Since v ₀ <v ₁ , a frictional force of μF acts on the center of the developing roller 5 (μ is a friction coefficient between the photosensitive drum 1 and the developing roller).

The positive direction of the upper in FIG. 10 Y, which right perpendicular to the positive direction of X in, l ₁ as described above each force is shown the position and angular of each point to act, l _2, l _3, l ₄ , θ, and developing roller 5
The driving moment of M, each guide roller 9,9 and notch 10,10
If the friction coefficients between are represented by μ ₁ and μ ₂ , the following equations hold in the X and Y directions.

Fcosθ + μFsinθ-P ± (μ 1 N 1 + μ 2 N 2) = 0 (1) N 1 + N following equation holds for _{2 -W-Fsinθ-μFcosθ = 0} (2) The moment.

M−N ₁ l ₁ −N ₂ l ₂ + Pl ₃ + Wl ₄ = 0 (3) By solving the above equations (1), (2) and (3), the force P
And F can be obtained.

Here, when ± (μ ₁ N ₁ + μ ₂ N ₂ ) in the equation (1) is referred to as a fluctuation term, the fluctuation term is a direction in which the developing device 2 swings and approaches the photosensitive drum 1. And positive and negative signs are alternately taken when the operation is performed in a direction away from the camera. Thus during oscillation of the developing roller 5, the value of variation term is changed, even if the first 11 pressure P of the spring 12 as shown in FIG constant as shown for example in P _1, the developing roller 5 photoconductive The pressure F received from the body drum 1 changes by a fluctuation range indicated by D in FIG. That is, the pressure contact force between the developing roller 5 and the photosensitive drum 1 fluctuates. If such a situation occurs, the density of the visible image formed on the surface of the photosensitive drum 1 also changes, and An image may not be obtained. FIG. 12 is a diagram for explaining this, in which the vertical axis represents the image density.
In the graph, ID is taken and the above-mentioned pressure F is plotted on the horizontal axis, where ID1 shows the minimum density of the image density generally required. As can be seen from this graph, if the pressure F fluctuates, the image density also changes accordingly, and the overall image quality decreases.

By reducing the weight W of the developing device 2 and hence N ₁ and N ₂ ,
If the friction coefficients μ ₁ and μ ₂ can be reduced, the influence of the fluctuation term can be reduced, but there is a limit to reducing these values.
FIG. 13 is a diagram showing the relationship between the pressure F and the friction coefficients μ ₁ and μ ₂ using the own weight W of the developing device 2 as a parameter. Device 2
Has moved in the direction in which it is returned from the photosensitive drum 1,
The relationship between the pressure F and the coefficient of friction when moving to the drum 1 side is shown. The two-dot chain line shows the same relationship when the own weight W is small, and the broken line shows the same relationship when the own weight W is intermediate. From this figure, it can be understood that the larger the weight W of the developing device 1 and the larger the friction coefficients μ ₁ and μ ₂ , the larger the fluctuation range of the pressure F and the more remarkable the fluctuation of the image density.

For example, when a developing roller having a length of A4 size is pressed against a photosensitive drum, a fluctuation occurs in the pressing force of the two, and it is considered that the fluctuation width is desirably suppressed to ± 200 g or less. . The pressure F of both at this time is 1000g ± 200
g. When the pressure F is 300 g or less, or 1.5 kg or more,
The image quality of the visible image is significantly deteriorated.

Therefore, as shown in FIG. 1 and FIG. 2, when the developing device carrier 15 is supported via a link plate and a four-bar rotating chain is formed as described above, the above-described problem can be greatly suppressed, and Variations in the pressing force between the roller 5 and the photosensitive drum 1 can be suppressed.

That is, in the configuration shown in FIG. 2, when the developing device 2 and the developing device carrier 15 swing in the directions of the arrows A and B, the resulting frictional resistance is generated at the pins 20, 20a, 20b and 20c. However, at the developing device carrier 15, this resistance decreases to the ratio of the lever length l of the link plate to the radius r of the pin, r / l. Therefore, the developing device 2 can swing without being substantially affected by the resistance. In other words, a result similar to that when the variation terms μ ₁ and μ ₂ in the above-mentioned equation (1) are made very small is obtained, and the width in which the pressure contact force between the photosensitive drum 1 and the developing roller 5 fluctuates. It can be kept small and the uniformity of the image density of the obtained visible image can be greatly improved.

Also, as shown in FIG. 1, when a four-node rotating chain is constituted by a supporting member, a link plate, and the like, when the developing device carrier 15 and the developing device 2 swing, one end side of the developing roller 5 and the other end thereof are rotated. Even if the surface condition (irregularity, eccentricity, etc.) of the roller 5 on the end side and the photosensitive drum 1 is different, the developing device carrier 15 and the developing roller 5 can follow up accordingly. That is, since the developing device carrier 15 can be elastically deformed to some extent, and the link plate has a slight play at the pin between the support member and the bracket, the developing device carrier 15 is located on the front side in FIG. The end and the back end can swing to some extent independently of each other. Thereby, the developing roller 5
The two ends of the support member swing independently of each other in accordance with the surface condition of the photosensitive drum 1 and the developing roller 5 is pressed against the photosensitive drum 1 while always following the entire length thereof.

By the way, in the example shown in FIG. 2, the developing roller 5 performs the developing operation while rotating in the counterclockwise direction, so that the roller 5 needs to be rotationally driven. Therefore, conventionally, a developing roller gear 27 is fixed to an end of one roller shaft 26 of the developing roller 2, and the developing roller gear 27 is rotationally driven to rotate the developing roller 2.

At that time, as shown in FIG. 9, a driving gear 28 rotatably supported on the image forming apparatus main body side meshes with the developing roller gear 27, and a motor (not shown) supported on the image forming apparatus main body. ), The gear 28 is driven to rotate, the rotation is transmitted to the developing roller gear 27, and the developing roller 5 is rotated. However, according to this configuration, when rotation is transmitted from the drive gear 28 to the developing roller gear 27,
Receives a force F1 (FIG. 9) from the mating gear 28 in a direction deviated from the common tangential direction by a pressure angle of the gear.
If this force is referred to as a tangential force, if a tangential force F1 acts on the developing roller 5 swingably supported with respect to the image forming apparatus main body, the roller 5 is moved away from the photosensitive drum 1. It is urged to. That is, the developing roller 5 receives a force such that the developing roller 5 is separated from the photosensitive drum 1 by a component force of the tangential force F1 in a direction away from the photosensitive drum 1. On the other hand, since no driving force is applied to the other roller shaft end of the developing roller 5, the developing roller 5 receives the tangential force F1 only at one end thereof, whereby the force balance is lost, There is a possibility that the developing roller 5 may be prevented from contacting the photosensitive drum 1 with a uniform pressure over the entire length thereof.

In the example shown in FIG. 9, the tangential force F1 acts on the developing roller 5 in a direction away from the photosensitive drum 1 side.
Depending on the engagement position of the developing roller 5 and the rotational direction of the developing roller 5, a tangential force in a direction in which the developing roller 5 approaches the photosensitive drum 1 may be applied.

The embodiment shown in FIGS. 1 and 2 is configured so that the above-mentioned problem can be eliminated.

1 and 2, a drive gear 29 is rotatably supported by the bracket 21 in the image forming apparatus main body side, in the illustrated example, and the gear 29 is supported by the image forming apparatus main body side. 2 is driven to rotate counterclockwise in FIG.

The driving gear 29 is connected to the developing roller gear 27 via intermediate gears 30, 31, and 32 rotatably supported by the link plate 19.
Drive-coupled. Therefore, the rotation of the driving gear 29 is transmitted to the first intermediate gear 30 meshing with the driving gear 29, further to another second intermediate gear 31 meshing with this, and further transmitted to another intermediate gear 32, and transmitted to this gear 32. The power is transmitted to the meshing developing roller gear 27. Thus, the developing roller 5 is driven to rotate counterclockwise in FIG. At this time, the meshing point between the drive gear 29 and the first intermediate gear 30, that is, the contact point within the pitch between the two gears 29, 30 coincides with the position of the pin 20, which is the center of rotation of the link plate 19.

When the drive gear 29 rotates and the rotation is transmitted to the first intermediate gear 30, a tangential force acts on the intermediate gear 30 as described above with reference to FIG. However, since the transmission point of the forces of the two gears 29 and 30 coincides with the center of rotation of the link plate 19, this tangential force is received by the pin 20. Therefore, the tangential force causes the developing roller 5 to move the photosensitive drum 1
The rotation is transmitted to the developing roller 5 via the gears 30, 31, and 27 in sequence without exerting a pressure on the developing roller or acting as a force for separating the drum from the drum 1. Therefore, the developing roller 5
However, even if the rotational driving force is input from only one end of the developing roller 5, the pressing force of the developing roller 5 against the photosensitive drum 1 is reduced by the tangential force F1 as in the conventional example shown in FIG. A problem such as weakening or strengthening at the end does not occur, and a visible image with uniform density can be obtained.

The agitator (see FIG. 9) provided in the toner container 3 can be configured to drive the developing roller 5 by transmitting the rotational force of the developing roller 5, as shown in FIGS. 1 and 2. In the illustrated embodiment, a gear 34 is fixed to a shaft 33 of the agitator, and a gear 35 meshing with the gear 34 is rotatably supported on a side plate of the toner container 3.
Is rotatably driven by a driving gear 28a rotatably supported by a bracket 21a on the image forming apparatus main body side via three intermediate gears 30a, 31a, 31a rotatably supported by a link plate 19a. The agitator is configured to be driven in a predetermined direction. When the agitator is driven by the drive gear 28a outside the developing device, a tangential force acts on the first intermediate gear 30a from the gear 28a. In this case as well, the intermediate gear 30a and the drive gear 28a are driven.
The meshing point of, that is, the transmission point of the force
It is preferable to match the position of the pin 20a which is the center of rotation of the photosensitive drum 1 so that the tangential force is not exerted on the photosensitive drum 1 via the developing roller 5.

In the example shown in the figure, the toner supply roller (see FIG. 9)
1, is driven to rotate via a belt 38 wound around a pulley 36 fixed to the shaft of the developing roller 5 and another pulley 37 fixed to the shaft of the toner supply roller, as shown in FIG. You.

In the above embodiment, the intermediate gears 30, 31,
Although such a gear is omitted, such a gear is omitted, the drive gear 28 is directly meshed with the developing roller gear 27, and the transmission point of both forces is matched with the rotation center of the link plate 19 or the position of the pin 20. May be. The same is true for the gear train driving the agitator. In this way, the input point of the driving force to the developing device is matched with the connection point between the link of the four-bar rotating chain and the image forming apparatus main body side, and the tangential force is set between the developing roller and the photosensitive drum 1. Configurations that render it inoperative can be implemented in various ways.

Even if the above-mentioned various gears are provided, they do not affect the attachment and detachment of the developing device 2 at all. When the developing device 2 is detached from the developing device carrier 15, the developing roller gear 27 is disengaged from the intermediate gear 32, and the gear 35 is disengaged from the intermediate gear.
When the developing device 2 is set on the developing device carrier 15, the gears mesh with each other, and the developing device 2 can be detached without any trouble.

As described above, in the embodiment shown in FIGS. 1 and 2,
Even when the weight of the developing device 2 becomes large due to the various configurations described above, the developing roller 5 can be uniformly pressed against the photosensitive drum 1, and the developing roller 5 can be simply set by appropriately setting the spring force of the spring 12. It is possible to control the pressure between the photosensitive drum 1 and the photosensitive drum 1 to a predetermined value.

In the embodiment shown in FIG. 3, an appropriate number of rollers 40 are rotatably supported on the lower surface of a developing device carrier 115 which supports the developing device 2 in a position-movable and detachable manner. The image forming apparatus is rotatably supported by a structure 11 of the image forming apparatus main body or a guide rail fixed thereto.
Also in this embodiment, the developing device carrier 115 can move in a direction approaching or separating from the photosensitive drum 1, and is urged toward the photosensitive drum 1 by a spring 12,
The developing roller 5 is uniformly pressed against the photosensitive drum 1. Further, similarly to the configuration of FIGS. 1 and 2, the developing device 2 can be configured to be attachable / detachable in the vertical direction or in other directions.
Further, when the developing device 2 swings, the developing device 2
(Refer to the figure).

The driving of the developing roller 5 shown in FIG. 3 is performed by a developing roller gear 27 fixed to the shaft 26, an intermediate gear 41 meshed with the gear and supported by the toner container 3, and the developing device carrier 11
An intermediate gear 43 fixed to a shaft 42 rotatably supported by 5
And a pulley 44 fixed to the shaft 42, a belt 45 wound around the pulley 44, and a pulley 46 supported rotatably on the image forming apparatus main body side and around which the belt 45 is wound. . That is, the pulley 46 is driven to rotate by a motor (not shown) supported on the image forming apparatus main body side, and the rotation is transmitted to the developing roller 5 via the above-described transmission elements.

At this time, the line L connecting the centers of the two pulleys 44 and 46 is substantially orthogonal to the direction in which the developing device carrier 115 swings together with the developing device 2, that is, the directions of arrows A and B. For this reason,
When the rotational force is transmitted from the belt 45 to the pulley 44, the ninth
Although a force corresponding to the tangential force shown in FIG. 7 acts on the pulley 44, the direction of the force is a direction that is directed in the direction of arrows A and B, that is, the direction of the line L. It does not act as a force for pressing or separating the body drum 1. Therefore, also in this embodiment, although the developing roller 5 is driven only from one end side of the developing roller 5 via the belt 45 or the like, only the one end side of the roller 5 is strong against the photosensitive drum 1, Or, a defect that is weakly hit hardly occurs. However, the developing device carrier 115
Are supported via the roller 40, and are not affected by the variation terms shown in FIG. 10 as in the configuration shown in FIG. 9, and in that sense, are affected in FIG. 1 and FIG. It can be said that the configuration shown is superior.

The same effect as described above can also be obtained by using a pair of sprockets and a chain wound around the sprockets instead of the belt 45 and the pulleys 44 and 46.

Further, instead of the belt 45 and the pulleys 44 and 46, the developing roller 5 may be driven via a universal joint 47 as shown in FIG. The joint 47 has a flexible member 48 such as rubber, which is known per se, and has one end 49 fixed to the shaft 26 of the developing roller 5 and the other end 50 connected to, for example, an image. It is fixed to a shaft of a gear (also not shown) of the image forming apparatus main body driven by a motor (not shown) fixed to the forming apparatus main body. Such a joint
Even if the developing roller 5 is driven from only one end using the 47, the disadvantage that one side of the roller 5 is strongly or weakly pressed against the photosensitive drum 1 can be eliminated. Even if a universal joint composed of an Oldham coupling is used, only the rotational moment is transmitted to the developing roller 2 in the same manner, and the above-described advantages can be obtained.

Instead of the gear train shown in FIGS. 1 and 2, the pulley and belt shown in FIG. 3 or the universal joint shown in FIG. 4 are used to transmit only moment to the developing roller 5. It is also possible.

Also in the embodiment shown in FIGS. 5 to 7, the developing device 2 is supported on the developing device carrier 215 so as to be stationary and detachable, and the advantages associated therewith are the same as in the previous embodiment. You can get it. At this time, in this embodiment, an appropriate number of link plates 119,
119 is disposed below the developing device carrier 215, one end of the plate is pivotally connected to the structure 11 of the image forming apparatus main body via pivot pins 51, 51, and the other end is connected via other pins 52, 52. And is pivotally attached to the support member 251.

Therefore, the developing device carrier 21 carrying the developing device 2
5 can operate between the position shown by the solid line and the position shown by the chain line in FIGS. That is, also in this embodiment, the developing device carrier 215 is supported by the image forming device main body so as to be movable toward or away from the photosensitive drum 1, and is urged by the pressing means including the spring 12. The developing roller 5 is pressed against the photosensitive drum 1.

Also in this embodiment, the advantage that the operability of attaching and detaching the developing device 2 can be improved is obtained, and the value of the variation term shown in FIG. It is possible to suppress the fluctuation of the force.

In this embodiment, as shown by an arrow P in FIG. 7, the developing device 2 can be pressed in the axial direction of the developing roller 5 by a pressing means such as a spring.

In each of the embodiments described above, if at least one surface portion of the photosensitive drum 1 and the developing roller 5 is made of a soft elastic material, the two are pressed against each other with a margin, and the uniform pressure contact can be further improved. Naturally, the present invention can be applied to a case where these are both formed of a rigid body.

In addition, as described above, the photosensitive drum
The present invention can be applied to a case where the developing roller is not pressed directly over the entirety thereof but is pressed against via another member. For example, as shown in FIG. 8, spacer rollers 71, 71 of the same diameter fixed on the shafts 26, 26 of the developing roller 5 are brought into contact with the photosensitive drum 1, and the developing roller 5 is They are opposed to each other with a predetermined gap G. In this case, so-called non-contact development is performed by the developing device 2. In such a developing roller 5 as well, each spacer roller 7
If the pressures of the members 1, 71 contact the photosensitive drum 1, the photosensitive drum 1 may generate an undesired vibration that may cause jitter, or the gap G may become non-uniform. Although the image quality of the visual image is degraded, such disadvantages can be eliminated by the above-described configurations.

〔The invention's effect〕

According to the present invention, the developing device is detachably supported on the developing device carrier while being stationary, and the developing device carrier is movably supported in a direction approaching or away from the surface of the image bearing drum. The developing device pressurizes the developing device carrier in a direction in which the developing roller is pressed against the surface of the image bearing drum by the pressing means, so that the developing device is movable with respect to the image bearing drum even when the developing device is replaced. The carrier is not replaced, so that the pressing force of the developing roller against the image carrying drum does not substantially change, and an image of the same quality before and after the replacement of the developing device can be formed on the surface of the image carrying drum. Further, the developing device can be easily attached to and detached from the developing device carrier, and it is not necessary to perform a troublesome operation such as removing or attaching the pressurizing means when attaching and detaching the developing device.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the developing device carrier and the developing device separated, FIG. 2 is an explanatory view schematically showing a state in which the developing device and the developing device carrier are assembled, and FIG. FIG. 4 is a view similar to FIG. 2, showing another embodiment, FIG. 4 is a perspective view showing an example of a universal joint, FIG. 5 is an exploded perspective view similar to FIG. FIG. 6 is a cross-sectional view of the developing device carrier shown in FIG. 5, FIG. 7 is a partial cross-sectional plan view in which the developing device shown in FIG. 5 is assembled to a photosensitive drum, and FIG. FIG. 9 is a plan view showing an example in which a roller and a photosensitive drum are arranged apart from each other. FIG. 9 is a cross-sectional view showing a conventional configuration example. FIG. FIG. 12 is a graph showing an example of the relationship between the pressing force and the image density. The by the weight of the developing device, it is a diagram for explaining that the fluctuation width is caused to press-contact force of the developing roller and the photosensitive drum. 2 developing device 3 toner container 5 developing roller 15,115,215 developing device carrier

Claims (1)

(57) [Claims] An image forming apparatus is rotatably supported by an image forming apparatus main body.
An image bearing drum on the surface of which an electrostatic latent image is formed while being rotated, and a developing device for visualizing the electrostatic latent image as a toner image, the developing device comprising: a toner containing toner; A container, and a developing roller rotatably supported by the toner container and carrying the toner on the surface thereof while being rotated and driven, the developing roller being directly or another member on the surface of the image bearing drum. And an image forming apparatus that visualizes the electrostatic latent image with toner carried on the surface of the developing roller and conveyed by the toner, wherein the developing device is removably supported although the position is not fixed. A developing device carrier supported by the image forming apparatus main body so as to be movable toward or away from the surface of the image bearing drum; and a developing device in a direction in which the developing roller is pressed against the surface of the image bearing drum. An image forming apparatus, comprising: a pressurizing unit for urging the image device carrier.