JPH0746249B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention [Field of Industrial Application] The present invention relates to an image forming apparatus such as an electrophotographic copying apparatus or an electrostatic recording apparatus. More specifically, the present invention relates to an image forming apparatus that has a first developing device and a second developing device, and performs development by selecting the first and second developing devices.

[Conventional technology]

2. Description of the Related Art Recently, image forming apparatuses such as electrophotographic copying apparatuses are not only used for copying with conventional black toner due to diversification of their functions,
Mono-color copying using other color toners such as red, blue and green is also becoming possible. In some of these devices, a developing device containing toner of a desired color is appropriately mounted on the user side by exchanging and mounting the developing device in the main body of the copying apparatus to copy the desired color.

Recently, an automatic double-sided / multi-copy system has become possible,
A plurality of developing devices containing toners of different colors are mounted and provided in the main body of the copying apparatus, and the developing devices are selectively switched and operated by a simple button operation on the operation section to perform monocolor copying of a desired color. It has become possible to easily perform multicolor copying on one copy paper. Also in this case, all or some of the plurality of built-in developing devices in the main body of the image forming apparatus can be freely replaced and replaced with those containing desired color toners on the user side.

As for the image carrier such as the photosensitive drum, there is also a system in which the user can replace the image forming apparatus body after every predetermined durability period, etc. as a mounting structure that can be easily replaced with respect to the image forming apparatus body for the purpose of maintenance-free operation. is there.

Thus, in the image forming apparatus as described above, the developing device in the device is moved closer to an image bearing member (hereinafter referred to as a photosensitive drum) such as a photosensitive drum, so that the developing device side anti-photosensitive drum spacer roller, etc. The developing position (hereinafter referred to as the first position) in which the contact member is brought into a predetermined pressure contact state (pressurizing force, for example, 5 to 6 kg) with the photosensitive drum side, or the developing member such as the developing sleeve is extremely closely faced and opposed. On the contrary, the position can be changed by the position switching / pressurizing mechanism to the non-developing position (hereinafter referred to as the second position) which is retracted from the photosensitive drum at a predetermined distance (for example, about 10 to 15 mm). Is installed in.

The developing device is inserted into and removed from the main body of the image forming apparatus with the developing device being switched to the second position which is the non-developing position with respect to the photosensitive drum. The developing device inserted in the main body of the image forming apparatus is then in the developing position with respect to the photosensitive drum.
It is converted to a position and held at that position. Alternatively, the position is converted to the first position according to the image formation execution signal. Further, in the type in which a plurality of developing devices are incorporated, each developing device is selectively converted into a first position and a second position, and one designated developing device is switched and held at the first position. At this time, the other developing devices are controlled so as to be switched and held at the second position.

[Problems to be solved by the invention]

In the image forming apparatus as described above, when the apparatus power is turned off while the developing device is held at the first position which is the developing position with respect to the photosensitive drum, for example, during or immediately after image formation, When the front door is opened and the device power is automatically turned off by the operation of the door switch, the position switching mechanism of the developing device becomes inactive at that time and the developing device remains in the first position state with respect to the photosensitive drum. Retained.

In this state, if the developing device or the photosensitive drum at the first position with respect to the photosensitive drum is inadvertently pulled out of the image forming apparatus main body when inspecting the inside of the device or replacing the developing device or the photosensitive drum, etc. Since the developing device is in pressure contact with or extremely close to the photosensitive drum, mutual damage or interference sliding between the developing device and the photosensitive drum may damage a considerably expensive photosensitive drum. become. Therefore, the developing device is firstly attached to the photosensitive drum.
It is necessary to release the developing device and the photosensitive drum by releasing the position switching / pressurizing means mechanism held in the position and separating the developing device from the photosensitive drum, but forget the treatment. It is not uncommon for the developing device or the like to be pulled out and moved to damage the photosensitive drum.

Particularly, this problem is caused by space saving and the like. When one developing device is switched and held at the first position, the other developing device is moved and held at the second position in association with the switching movement. In the image forming apparatus of the mutual developing device interlocking type, in which the other developing device is moved to and held at the first position when the two developing positions are switched and held, the one developing device is always moved to the photosensitive drum. On the other hand, it is inevitable because it is held in the first position.

Conventionally, with respect to the developing and forming apparatus having the first and second developing devices built therein, the moving structure of the first and second developing devices is such that each moving device is provided with a separate moving means. It is known that one size is provided in the casing and the casing is rocked.

However, the former one has a problem that the volume occupied by a plurality of moving means is large and the device becomes large. Further, the latter one has a problem that the moving range occupies a large volume because it is a large casing and the size is similarly increased, and the positional accuracy of holding each developing device at a predetermined developing position is poor. Therefore, the amount of the developer stored in these is also limited, and there is a problem that the frequency of replenishment of the developer is high.

In view of the above, the present invention provides an image forming apparatus that can move the first and second developing devices with a simple configuration and can improve the positional accuracy.

B. Structure of the Invention [Means for Solving the Problems] That is, the present invention relates to an image carrier, a first developing device for developing an electrostatic image on the image carrier, and a developing device for the first developing device. A moving means for moving between the position and the retreat position, and a first developing device that receives the first developing device as a cam and moves from the retreating position to the developing position in conjunction with the movement of the first developing device from the developing position to the retreating position. A second developing device that moves from the developing position to the retracted position in conjunction with the movement from the retracted position to the developing position, and an opening / closing portion that can be opened / closed with respect to the apparatus main body, and open the opening / closing portion. The second developing device is also separated from the image carrier by releasing the pressure applied to the developing position side by the moving means to position the first developing device between the developing position and the retracted position. .

〔Example〕

The drawing shows a concrete example of the embodiment apparatus according to the present invention.

In FIGS. 1 and 2, D is a photosensitive drum as an image carrier, which is rotatably driven in the direction of the arrow at a predetermined peripheral speed, and an electrostatic latent image is formed on its peripheral surface by a known appropriate latent image forming process device (not shown). An image is formed. A · B are mutually discolored toner (developer) developing apparatus of the first and second 2 units containing a t _A · t _B.

The first developing device A is swingable around the support stay 1 in the clockwise and counterclockwise directions. The second developing device B is slidably supported by the support member 2 in a direction of approaching the photosensitive drum D and in a direction of retracting the photosensitive drum D, and is constantly biased by a tension spring 3 in the retracting direction.

FIG. 1 shows a cam which is a pressing member of the first developing device A described later.
30 and a cam follower 6 (first pressed portion) as a pressed portion are rotationally driven clockwise around the support stay 1 to switch and hold the photosensitive drum D at a first position which is a developing position. The second developing device B is interlocked with each other and is being switched and held at the second position which is the non-developing position.

In this state, the first developing device A has the developing sleeve 11
Spacer rollers 12 arranged on both ends of the (developer carrying means) and having a diameter larger than that of the sleeve contact the surfaces on both ends of the photosensitive drum D with a predetermined pressing force, and the developing sleeve 11 has a predetermined contact force. It is kept in a state of closely approaching and facing the surface of the photosensitive drum D with a small gap α, and the drum surface can be developed by the first developing device A. On the other hand, the second developing device B is held by the tension spring 3 at the second position received by the stopper 4, and the developing sleeve 21 is largely separated from the photosensitive drum D (for example,
10 to 15 mm).

In contrast to the above, FIG. 2 shows a cam 30 as a pressing member and a lever 34 (second pressed portion) as a pressing member, which will be described later in the first developing device A.
Is rotated counterclockwise about the support stay 1 and is switched and held at a second position, which is a non-developing position, with respect to the photosensitive drum D, and the second developing device B is interlocked with the second position and is held at the second position. The state is shown in which the protrusion 5 on the side of the first developing device A, which has been switched to, is moved forward with respect to the photosensitive drum D against the tension spring 3 and switched and held at the developing position.

In this state, the second developing device B is arranged on both ends of the developing sleeve 21, and the spacer rollers 22 having a diameter larger than that of the sleeve come into contact with the end faces of the photosensitive drum D with a predetermined pressure, The developing sleeve 21 is kept in a state of closely approaching and facing the surface of the photosensitive drum D with a predetermined small gap α, and
The drum surface can be developed by the developing device A. On the other hand, in the first developing device A switched and held in the second position, the developing sleeve 11 is largely separated from the photosensitive drum D, and the externally exposed surface of the developing sleeve 11 is hidden by the closing operation of the developing sleeve shutter 13. .

The alternating position switching drive of the first and second developing devices A and B is performed by controlling the rotation angle of the cam 30 by a mechanism including a spring clutch 40 and a solenoid 50 shown in FIGS.

That is, when the first developing device A is designated, the solenoid 50 is de-energized, and when the second developing device B is designated, the solenoid 50 is energized.

(1) FIG. 3 shows when the solenoid 50 is not energized, that is, the first
When the developing device A is designated, the iron core 51 of the solenoid 50 is free, and the lever 52 connected to the iron core causes the pulling force of the tension spring 53 to rotate counterclockwise about the shaft 54. It is received and held in the rotation angle posture shown by the solid line. The control ring 45 of the spring clutch 40 is attached to the tip of the lever 52.
The first claw 45a of the control ring 4 is received (Fig. 5 (a)), and the control ring 4
5 rotations are blocked. This allows the clutch spring 44
Is held in a loose state (clutch-off) with respect to the spring winding cylinder 42a of the driving side gear 42 and the spring winding cylinder 43a of the driven side gear 43, and the driving force transmitted from the driving source gear G to the driving side gear 42 is It is not transmitted to the driven gear 43. Therefore, the driven side gear 43
The angular shaft gear 33 that meshes with the angular shaft 31, the angular shaft 31, and the cam 30 attached to the angular shaft are also in a rotation stopped state.

In this state, the cam 30 moves the first developing device A as shown in FIG.
Side cam follower 6 is in contact with the rotation angle position, the cam
The first developing device A is rotated counterclockwise around the support stay 1 by the pressing force of 30 and is switched to the first position which is the developing action position with respect to the photosensitive drum D. The cam 30 is supported so as to be slidable in the long axis direction of the cam at a right angle to the angular axis with respect to the U-shaped angular axis 31, and the spring 32 compressed inside the cam constantly biases the angular direction to project forward from the angular axis. I am receiving an F. Due to the urging force F, the spacer rollers 12 on both ends of the developing sleeve are kept in pressure contact with the surfaces on both ends of the photosensitive drum D with a force of about 5 to 6 kg.

The second developing device B is cut off from the first developing device A held at the first position and is held at the second position retracted by the spring 3 until it comes into contact with the stopper plate 4. .

(2) When the second developing device B is designated in the above state, the solenoid 50 is energized.

Then, the iron core 51 is pulled into the solenoid and the lever 52
Is rotated clockwise about the shaft 54 against the spring 53 and the third
The position is displaced to the position shown by the dashed line in FIG. As a result, the lever tip is disengaged from the first pawl 45a of the control ring 45 of the spring clutch to escape and the rotation inhibition of the control ring is released, and the clutch spring 44 is tightened against the spring winding cylinders 42a and 43a ( Clutch-on), the rotational force of the drive source gear G is transmitted to the angular shaft gear 33 via the spring clutch 40 in the clutch-on state, and the angular shaft 31 and the cam 30 rotate counterclockwise in FIG. .

Spring clutch 40 rotates approximately 90 ° (clockwise rotation in Fig. 5)
At that time, the second pawl 45b of the control ring 45 comes into contact with the tip of the lever 52 which is displaced to the position shown by the dashed line in FIG. 3 (FIG. 5 (b)), and the control ring 45 rotates. Is blocked. As a result, the clutch spring 44 is held in the loosened state (clutch-off), and the transmission of the rotational force to the angular shaft gear 33 is cut off.

The cam 30 moves to the first position as the spring clutch 40 rotates about 90 °.
After rotating 90 degrees counterclockwise from the rotation angle position shown in the figure, the second
It becomes the rotation angle position in the figure. During this rotation process, the cam 30 is cut off from the cam follower 6 of the first developing device A, and then comes into contact with the first arm 34a of the lever 34 which is loosely supported coaxially with the support shaft 41 of the spring clutch 40, and the lever 34 is rotated clockwise about the support shaft 41 in FIG. The rotation of the lever causes the second arm 34b to come into contact with the lower surface side of the cam follower 6 of the first developing device A to rotate the first developing device A counterclockwise about the support stay 1 to the second position. Switch and move. Immediately before the first developing device A reaches the second position, the developing sleeve shutter 13 closes the developing sleeve 11 by an interlocking mechanism (not shown).

In the process of the first developing device A switching to the second position as described above, the second developing device B causes the protrusion 5 on the first developing device A side to move.
It is pushed by and is moved forward with respect to the photosensitive drum D against the tension spring 3 and is switched to the first position.

Finally, the cam 30 is moved to the first position of the lever 34 as shown in FIG.
The rotation is stopped at the rotation angle position in contact with the tip of the arm 34a,
The first developing device A is held at the second position, and the second developing device B is held at the first position in a switched state.

In the second developing device B switched to the first position, the spacer roller 22 on both end sides of the developing sleeve is applied to the both end surface of the photosensitive drum D by a force of about 5 to 6 kg by the urging force F of the compression spring 32 in the cam 30. It is kept in pressure contact.

(3) When the first developing device A is designated again in the above state, the energization of the solenoid 50 is cut off.

Then, the iron core 51 becomes free, and the lever 52 is rotated counterclockwise about the shaft 54 by the tension spring 53 to return to the rotation angle posture shown by the solid line in FIG. As a result, the lever tip is disengaged from the second pawl 45b of the control ring 45 and escapes to release the rotation inhibition of the control ring 45, so that the clutch spring 44 moves the spring winding cylinders 42a and 43a.
With respect to the spring clutch in the winding-on state (clutch-on), the rotational force of the drive source gear G is in the clutch-on state.
It is transmitted to the angular shaft gear 33 via 40, and the angular shaft 31 and the cam 30 rotate counterclockwise in FIG.

When the spring clutch 40 rotates about 270 °, the first pawl 45a of the control ring 45 comes into contact with the tip of the lever 52 which is displaced to the position shown by the solid line in FIG. 3 (FIG. 7 (a)). ) Control ring 45
Is blocked, the spring clutch 40 is turned off, and the torque transmission to the angular shaft gear 33 is cut off.

With the rotation of the spring clutch 40 by about 270 °, the cam 30 breaks the edge of the lever 34 and finally comes into contact with the cam follower 6 of the first developing device A shown in FIG. 1 from the rotational angle position shown in FIG. The rotation angle position is reached, and the first developing device A is converted to the first position and the second developing device B is converted and held in the second position as in the item (1).

FIG. 6 is a rear view of FIG. G _D is a drum gear integrated with the photosensitive drum D, and meshes with the drive gear G _M. G
Reference numeral ₁₁ is a developing sleeve gear of the first developing device A, and G ₁₄ is a developer stirring gear, which meshes with the developing sleeve gear G ₁₁ . The rotation of the drive gear G _M causes the drum gear G _{D, that} is, the photosensitive drum D, to be rotationally driven at a predetermined peripheral speed. The developing sleeve gear G ₁₁ meshes with the drum gear G _D when the first developing device A is switched and held at the first position, and the developing sleeve 11 of the first developing device A and the developing sleeve 11 of the first developing device A are interlocked with the rotation of the photosensitive drum D. The developer stirring member 14 is driven to rotate.

When the second developing device B is switched and held in the first position, the developing sleeve gear G ₂₁ on the side of the second developing device B is changed to the drum gear G.
The developing sleeve 21 of the second developing device B meshes with _D and is rotationally driven in association with the rotational driving of the photosensitive drum D, and
Rotation of developing sleeve gear G ₂₁ causes developer stirring gears G ₂₄ and G ₂₅
And the developer agitating / conveying members 24 and 25 are rotated.

The solenoid 50 is fixedly mounted and supported inside the vertical side plate 60 which is a stationary member. Reference numeral 61 is a vertical moving vertical bar arranged on the outer surface side of the side plate 60. FIG. 7 shows a front view of the bar. The bar 61 is a bush provided vertically on the outer surface of the vertical side plate 60.
62.63 and vertically slidable with respect to the outer surface of the vertical side plate 60 within the length range of the vertically elongated holes 64, 65 guided by the vertically elongated holes 64, 65 formed on the bar side and engaging with the bush respectively. Be free.
Reference numeral 66 is a cut-and-raised portion provided in the bar portion between the upper and lower elongated holes 64 and 65, and a coil spring 67 is stretched between the cut-and-raised portion 66 and the upper bush 62. Therefore, the bar 61 is constantly urged to move upward by the spring 67, and is in a free state (6th.
In FIG. 7), the lower end of the vertically elongated hole is pulled up to the highest position where it abuts against the bush and is received, and is stopped and held at that position.

Pin shaft connecting the iron core 51 of the solenoid 50 and the lever 52
55 is an outer surface of the vertical movement bar 61 through vertical holes 68 and 69 provided by extending a rear end 55a side opposite to the connecting end side with the lever 52 and corresponding to the vertical side plate 60 and the vertical movement bar 61, respectively. It is projected to the side.

Reference numeral 70 denotes an outer surface side of the vertical movement bar 61, which is a semi-circular leaf spring piece having its upper end fixedly attached to a position above the vertically elongated hole 69 in which the rear end 55a of the pin shaft 55 projects, and 71 is vertical movement. It is a roller provided on the upper end of the bar 61.

On the other hand, the image forming apparatus main body is a divided body of an upper main body and a lower main body, both of which are openable and closable via a hinge.
Since such a device body opening / closing structure itself is already known, it is omitted in the drawing.

Various kinds of required image forming process equipments are separately arranged on the upper body side and the lower body side, respectively. In the apparatus of this example, the photosensitive drum D and the first and second developing devices A and B are provided on the upper main body side with a developing device position switching / pressurizing means including a cam 30, a spring clutch 40, a solenoid 50, and a vertically moving bar 61. The mechanism is arranged on the lower body side.

(A) FIGS. 1, 2, and 6 are views when the upper body and the lower body are closed, respectively.

In this closed state, the up-and-down moving bar 61 is in a free state and is lifted to the highest position and stopped and held (Fig. 7).
The leaf spring piece 70a is held in a non-acting position with respect to the rear end 55a of the pin shaft 55.

As described above, when the first developing device A is designated, the energization of the solenoid 50 is cut off, and the second developing device B is disconnected.
Is designated, the power is supplied to selectively move the first developing device A or the second developing device B to the first position with respect to the photosensitive drum D as described in the above items (1) to (3). The images are switched and held, and image formation using the first developing device A or image formation using the second developing device B is executed.

(B) The internal inspection of the image forming apparatus and the replacement of the developing device and the photosensitive drum are performed by opening the main body from the lower main body.

FIG. 8 shows a state in which the upper main body side including the photosensitive drum D and the first and second developing devices A and B is opened from the closed state shown in FIGS. 1 and 6 to the lower main body side. .

In this case, even when the second developing device B is switched and held at the first position with respect to the photosensitive drum D (FIG. 2) at the time when the upper main body is opened, the apparatus power is turned off before the upper main body is opened. When the upper main body is opened or the safety switch is actuated to automatically turn off the power supply to the apparatus, the solenoid 50 is de-energized, and the first developing device A is moved to the photosensitive drum D correspondingly. In contrast, the first developing device B is switched to the first position and the second developing device B is switched to the second position.
The state shown in Fig. 6 is obtained.

In the open state of FIG. 8, the cam follower 6 on the first developing device A side escapes upward from the cam 30 of the developing device position switching / pressurizing means mechanism on the lower main body side as the upper main body is opened and raised. The edge with the cam 30 is cut off. Then, the pressure applied to the cam follower 6 is released, and the first developing device A, which is held at the first position with respect to the photosensitive drum D, naturally rotates in the direction of retracting from the photosensitive drum D around the support stay 1 due to the action of the center of gravity. Move. The retracted rotation position is a rotation position substantially intermediate between the first position and the second position of the first developing device A with respect to the photosensitive drum D. At the retracted rotation position of the first developing device A, the protrusion 5 of the first developing device A moves toward or abuts against the second developing device B side, but even if it abuts, the pressing force is weak. The second developing device B is also held substantially at the second position with respect to the photosensitive drum D.

Therefore, as shown in FIG. 8, the first and second developing devices A and B are automatically replaced with the non-contact, non-pressurized state in which there is an appropriate clearance β / α with respect to the photosensitive drum D. Retained.

Thus, due to the existence of the above-mentioned gap β / α, the first or / and second developing device A / B on the upper main body side, or the photosensitive drum D
Even if the developing device is inserted and removed, contact and sliding between the developing device and the photosensitive drum cannot occur, and the problem of damaging the photosensitive drum does not occur.

(C) On the other hand, when the upper main body is opened, a member on the upper main body side, in the case of this example, a rear end portion of the support member 2 of the second developing device B
2a contacts the roller 71 at the upper end of the vertical movement bar 61 and presses the roller. By the pressing, the vertical moving bar 61 is pressed downward against the tension coil spring 67. And the bar 61
The leaf spring 70, which is integrally provided with the pin shaft 55, also descends so that its lower end 70a abuts the rear end 55a of the pin shaft 55, and a downward force is applied to the pin shaft 55.

Then, the iron core 51 of the solenoid 50 is mechanically pushed down into the solenoid 50 against the tension spring 53 of the lever 52, and the lever 52 is rotated about the shaft 54 in the clockwise direction in FIG. The clockwise rotation of the lever 52 causes the tip of the lever 52 to escape from the first pawl 45a of the control ring 45 of the spring clutch 40, and the engagement with the first pawl 45a is disengaged (dotted line in FIG. 3). When the tip of the lever 52 comes off from the first claw 45a,
The control ring 45 is slightly rotated clockwise (counterclockwise in FIG. 8) by the winding tightening force of the clutch spring 44 as shown in FIG. 9 (a).
f _1, and the spring clutch 40 is a clutch - set to ON-state.
Even when the clutch is on, when the image forming apparatus is in the open state, the power supply circuit of the image apparatus is off, and the drive source gear G is not rotating, so the mechanism 43.33. 31/30 also does not rotate.

(D) When the inspection of the inside of the image forming apparatus main body and the replacement of the image forming apparatus and the photosensitive drum are completed, the upper main body is closed with respect to the lower main body.

FIG. 10 shows the state of the process just before the closure is completed. In this state, the cam follower 6 of the first developing device A on the upper main body side, which has been closed, comes into contact with the cam 30 of the developing device position switching / pressurizing means mechanism on the lower main body side from above. Then, the cam 30 is pushed by the cam follower 6 by the subsequent closing of the upper body, and the cam 30 and the angular shaft 31 to which the cam is attached are rotated f ₂ clockwise in FIG. The rotation causes the control ring 44 of the spring clutch 40 to rotate f ₃ counterclockwise in FIG. 10 to some extent. As described above, the rotation of the control ring 44 is released by releasing the tip of the lever 52 from the first pawl 44a of the control ring (FIGS. 8 and 9 (a)). Tolerated by

On the other hand, the member 2a is released from the roller 71 at the upper end of the vertical movement bar 61, and the pressing force on the vertical movement bar 61 is released. As a result, the bar 61 is brought into a free state and is lifted to the highest position and locked and held. As a result, the leaf spring piece for the pin shaft 55 is
The pushing down by the lower end 70a of 70 is also released, the iron core 51 of the solenoid 50 is returned to the state in which it is projected from the solenoid by the tension spring 53, and the lever 52 is centered around the shaft 54 from the position shown by the chain double-dashed line in FIG. It is rotated counterclockwise as indicated by the solid line.

When the upper main body is completely closed with respect to the lower main body, the control ring 45 of the spring clutch 40 presses the cam 30 by the cam follower 6 of the first developing device A as described above. It is rotated f ₃ by rotation f ₂ (FIG. 10) and is positioned at the rear position of the first claw 45a of the control ring 45 as shown in FIG. 9 (b), or the side surface of the first claw 45a. Is in contact with.

(E) Then, the upper body is closed with respect to the lower body,
Next, when the device power is turned on, the drive motor is actuated to rotate the drive source gear G, and the drive force is transmitted to the drive-side gear 42 of the spring clutch 40, the spring clutch 40 causes the first ring of the control ring 45 to move. As shown in FIG. 9B, the tip of the lever 52 is disengaged from the pawl 45a, and the second pawl 45b is also in the non-engagement clutch-on state. The angular shaft 31 and the cam 30 are driven to rotate. When the control ring 45 of the spring clutch 40 rotates clockwise about 270 ° from the angular position of FIG. 9 (b), the first pawl 45a abuts against the tip of the lever 52 and is received (FIG. 5 (a)). ), The rotation of the control ring 45 is blocked, and the spring clutch 40 is turned off.

As a result, the cam 30 is returned (reset) to a state in which the cam 30 comes into contact with the cam follower 6 of the first developing device A at a regular turning angle as shown in FIGS. 1 and 6 and is stopped, and the first developing device A is exposed to light. The drum D is stably held at a predetermined first position with a predetermined pressure. After that, when the second developing device B is designated, the solenoid 50 is energized, and the first developing device A is moved backward to the second position with respect to the photosensitive drum D as described in the item (2), and is interlocked with it. And the second developing device B
Is switched to the first position and held (FIG. 2).

As described above, according to the present invention, since the second developing device can be held at the predetermined position by the movement of the first developing device, the positional accuracy is high, the configuration is simple, and the device is downsized. it can. In other words, the amount of the retained developer in the developing device can be increased without increasing the size of the device, and the intended purpose can be achieved well.

Further, since the first and second developing devices are held in the non-developing position when the opening / closing part is opened, even if the image carrier, the developing device, etc. are taken out during maintenance, they do not come into contact with each other. It is possible to prevent equipment damage.

[Brief description of drawings]

FIG. 1 shows the state in which the first developing device and FIG. 2 show the state in which the second developing device is switched and held at the developing position, and FIG. 3 shows the developing device position switching / pressurization consisting of a spring clutch and a solenoid. FIG. 4 is a longitudinal sectional view of the spring clutch, and FIGS. 5A and 5B are transverse sectional views of the spring clutch showing the relationship between the pawls of the control ring and the locking lever, respectively. 1 is a rear view of FIG. 1, FIG. 7 is a front view of the vertical movement bar portion, FIG. 8 is a rear view of the apparatus when the upper body is open, and FIGS. 9 (a) and 9 (b) are the upper body. FIG. 10 is a transverse cross-sectional view of the spring clutch showing the relationship between the claws of the control ring and the locking lever when opening and closing of FIG. 10, and FIG. 10 is a rear view of the device when the closing of the upper main body is completed a little before. D is a photosensitive drum which is a member to be developed, and A and B are first and second.
2 developing devices, 30 is a cam, 40 is a spring clutch, 50 is a solenoid, and 91 is a vertical movement bar of a reset mechanism.

Continuation of the front page (56) Reference JP-A-49-51953 (JP, A) JP-A-60-254065 (JP, A) JP-A-60-120377 (JP, A) JP-A-56-142559 (JP , A) Actually open 60-39055 (JP, U) Actually open 60-163454 (JP, U)

Claims (1)

[Claims] 1. An image carrier, a first developing device for developing an electrostatic image on the image carrier, moving means for moving the first developing device between a developing position and a retracted position, and a first developing device. Receiving the developing device as a cam and moving from the retracting position to the developing position in conjunction with the movement of the first developing device from the developing position to the retracted position, and developing position in conjunction with the movement of the first developing device from the retracted position to the developing position. From the retracted position to the retracted position, and an opening / closing portion that can be opened / closed with respect to the main body of the apparatus. By opening this opening / closing portion, the pressure applied to the developing position side by the moving means is released. 1
By positioning the developing device between the developing position and the retracted position, the second
An image forming apparatus characterized in that the developing device is also separated from the image carrier.