JPH10123783A - Color image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily release a jamming by placing each image forming part on a retreating position and traveling a carrying belt in the reverse direction in the case where the occurrence of the jamming has been detected. SOLUTION: A controller judges that a jamming has occurred at a fixing device 48 based on the change of temperature detected by a temperature sensor 81, and stops the operation of a color image recorder. A jamming releasing means drives the respective first motors of the image formula parts 12C, 12K,... in the reverse direction so as to rotate a gear. At this time, a one-way bearing is locked, the rotation of the gear is transmitted to a cam shaft 22, and an eccentric circular cam 23 is rotated. As the result, the respective image forming parts 12C, 12K,... are placed on the retreating position, and each photoreceptor is speared from the carrying belt 20. A second motor is driven in the reverse direction so as to rotate a driving roller 31, a heat roller 49 and a pressure roller 50 in the reverse direction, and the front end of a recording medium 21 reaches a position where the medium 21 is positioned between a discharging device 102 and the part 12K, then the second motor is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image recording apparatus for forming a color image.

[0002]

2. Description of the Related Art Conventionally, a color image recording apparatus has an image forming section for each color of yellow, magenta, cyan and black, and each image forming section has a recording head formed by arranging recording elements in a line. Is provided. Then, the recording medium is fed one by one from a paper storage cassette, is attracted to a transport belt, and is transported in a direction perpendicular to the arrangement direction of the recording elements.

[0003] The image forming section includes yellow, magenta,
A toner image of each color is formed line by line with toner of each color of cyan and black, and the toner images are sequentially superimposed on the recording medium.

[0004]

However, in the above-described conventional color image recording apparatus, even when only a toner image of a predetermined color is formed, the image forming units of all colors are operated and each image forming unit is operated. Since the photosensitive drum and the conveyor belt are brought into contact with each other directly or via a recording medium, the photosensitive drum and the conveyor belt are worn and the life is shortened.

[0005] Further, as each image forming section is operated, the deterioration of the toner of each color is increased, the life of the toner is shortened, and the image quality is deteriorated. Further, the recording medium is conveyed by being attracted to the conveyor belt by the electrostatic force, so that when the electrostatic force becomes strong, for example, when the humidity is low, the recording medium is caught in the heat roller of the fixing device. Jams may occur.

In this case, it is necessary to pull out the recording medium wound around the heat roller, and it is difficult to clear the jam. The present invention solves the problems of the conventional color image recording apparatus, can extend the life of the photosensitive drum, the conveyance belt, and the toner, and can improve the image quality and reduce the jam. It is an object of the present invention to provide a color image recording device that can be easily released.

[0007]

For this purpose, in the color image recording apparatus of the present invention, a transport belt which is transported by a driving means and transports a recording medium, and which is disposed in opposition to the transport belt, is provided. A plurality of image forming units that take a retracted position and an image forming position and form a toner image on the photosensitive drum when placed at the image forming position, and face each of the photosensitive drums via the transport belt. Transfer means disposed in the image forming section, image forming section moving means for selectively placing each of the image forming sections at the retracted position and the image forming position, jam detecting means for detecting that a jam has occurred, and detecting the jam. And a jam clearing unit for setting each of the image forming units to the retracted position when the jam is detected by the unit and causing the transport belt to run in the reverse direction.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a first schematic diagram of a color image recording device according to the first embodiment of the present invention, FIG. 2 is a second schematic diagram of the color image recording device according to the first embodiment of the present invention, and FIG. FIG. 4 is a perspective view of an image forming unit located at an image forming position according to the first embodiment of the present invention, and FIG. 4 is a diagram illustrating a jam clearing method of the color image recording apparatus according to the first embodiment of the present invention. is there.

In FIG. 1, a color image recording apparatus 11 is provided with four sets of first to fourth printing mechanisms P1 to P4 in order from the insertion side of the recording medium 21 to the ejection side.
The fourth to fourth printing mechanisms P1 to P4 are each composed of an electrophotographic LED printing mechanism. The first printing mechanism P
Reference numeral 1 denotes a yellow image forming unit 12Y, an LED head 13 that exposes the surface of the photosensitive drum 16 according to image data.
Y, and a transfer roller 1 for transferring a yellow toner image formed by the image forming unit 12Y to a recording medium 21
4Y.

Similarly, the second printing mechanism P2 includes a magenta image forming section 12M, an LED head 13M for exposing the surface of the photosensitive drum 16, and the image forming section 1M.
The transfer roller 14M transfers a magenta toner image formed by 2M onto the recording medium 21. The third printing mechanism P3 includes a cyan image forming unit 12C,
LED head 1 for exposing the surface of the photosensitive drum 16
3C, and a transfer roller 1 for transferring the cyan toner image formed by the image forming unit 12C to the recording medium 21
4C.

The fourth printing mechanism P4 includes a black image forming section 12K, an LED head 13K for exposing the photosensitive drum 16, and a black toner image formed by the image forming section 12K on a recording medium. The transfer roller 21K transfers the image to the transfer roller 21. The transfer roller 1
The transfer means is constituted by 4Y, 14M, 14C, and 14K.

Each of the image forming units 12Y, 12M, 12
C and 12K each have the same structure, and the photosensitive drum 16 is rotated around the shaft 15 in the direction of arrow a;
The developing device 18 includes a charging roller 17 for uniformly and uniformly charging the surface of the photosensitive drum 16. Also,
The cleaning blade 79 is pressed against the photosensitive drum 16 and scrapes off toner remaining on the surface of the photosensitive drum 16 after transfer. Further, the scraped-off toner is stored in a waste toner box (not shown) by the spiral screw 78.

The developing device 18 includes a developing roller 1.
9 and a toner tank (not shown), and a developing blade, a sponge roller (not shown), and the like (not shown) are pressed around the developing roller 19. The image forming units 12Y and 12Y
Each component of M, 12C and 12K is supported by each frame 24. In the developing device 18, the non-magnetic one-component toner supplied from the toner tank is sent to a developing blade via a sponge roller, and is thinned on the surface of the developing roller 19 by the developing blade. It is sent to a developing section between the developing roller 16 and the developing roller 19. When the toner is thinned, the toner is strongly rubbed (rubbed) by the developing roller 19 and the developing blade to be charged. In this embodiment, the toner is charged to a negative polarity. Further, in the present embodiment, the developing roller 19 is made of a semiconductive rubber material.

Next, the LED heads 13Y, 13M,
13C and 13K will be described. The LED head 1
3Y, 13M, 13C, and 13K are LED arrays (not shown) and a drive I (not shown) for driving the LED arrays.
C, a substrate on which the drive IC is mounted, a rod lens array for condensing the light of the LED array, and the like. Each LED element of the LED array is arranged according to a color image signal transmitted from a higher-level device via an interface unit (not shown). Light is selectively emitted to form an electrostatic latent image on the surface of the photosensitive drum 16. Then, the toner on the developing roller 19 is attached to the electrostatic latent image by electrostatic force, and a toner image is formed.

Each of the LED heads 13Y, 13M, 1
3C and 13K are pressed downward in the drawing by the urging force of the spring 17a. In addition, an endless transport belt 20 is movably disposed at a transfer portion between each of the photosensitive drums 16 and each of the transfer rollers 14Y, 14M, 14C, and 14K. The developing device 18 of the image forming section 12Y contains yellow toner, the developing device 18 of the image forming section 12M contains magenta toner, and the developing device 18 of the image forming section 12C.
Is the developing device 1 of the image forming unit 12K.
8 stores black toner.

A yellow image signal among the color image signals is supplied to the LED head 13Y of the first printing mechanism P1.
The magenta image signal among the color image signals is supplied to the LED head 13M of the second printing mechanism P2 by the third printing mechanism P3.
Of the color image signal, the LED head 13C of the fourth printing mechanism P4
, A black image signal among the color image signals is input.

Next, each of the image forming units 12Y, 12M, 12
The image forming unit moving means for selectively placing C and 12K at the retreat position and the image forming position will be described. A protrusion 24a is formed at an upstream end of each of the frames 24 in the transport direction of the recording medium 21.
4a is rotatably engaged with a guide groove (not shown) formed in the main body of the color image recording apparatus 11.
Therefore, by swinging the frame 24 around the projection 24a, each of the image forming portions 12
Y, 12M, 12C, and 12K can be placed at the retreat position and the image forming position. As shown in FIG. 3, a protruding plate portion 24b is formed at the downstream end of the frame 24 in the transport direction of the recording medium 21.

Further, on the downstream side of the image forming units 12Y, 12M, 12C and 12K in the conveying direction of the recording medium 21, a cam shaft 22 is provided with a color image recording apparatus 1.
The eccentric cams 23 are rotatably supported by the main body 1 and are fixed near both ends of the camshaft 22 so as to face the protruding plate portions 24b. The frame 24 is connected to the LED heads 13Y, 1Y by a spring 17a.
It is pressed downward via 3M, 13C, 13K.

Each of the LED heads 13Y, 13M, 1M
3C and 13K are attached to the upper cover 11a of the color image recording apparatus 11, so that the upper cover 11
a, the LED heads 13Y, 13Y
M, 13C, and 13K to the image forming units 12Y, 12M,
12C and 12K are removed from the image forming units 12Y and 12Y.
2M, 12C, 12K can be attached and detached. For this purpose, the upper cover 11a is swingably supported on the main body of the color image recording apparatus 11 about a hinge 11b.

A gear 25 is disposed at one end of the camshaft 22 via a one-way bearing 22a. The gear 25 is fixed to a rotating shaft of the first motor 28 via a gear 70. The motor gear 27 is engaged (engaged). The gear 70 meshes with the large gear 26 a of the two-stage gear 26, and the small gear 26
b and the gear 16 a of the photosensitive drum 16 are meshed via the gear 71.

When the gear 25 is rotated in the direction of arrow s in FIG. 3, the one-way bearing 22a idles,
The rotation of No. 5 is not transmitted to the camshaft 22. vice versa,
When the gear 25 is rotated in the direction of arrow t, the one-way bearing 22a is locked, the rotation of the gear 25 is transmitted to the camshaft 22, and the eccentric cam 23 is rotated in the direction of arrow t.

When the gear 25 is rotated in the direction of arrow s, the photosensitive drum 16 is rotated in the direction of arrow a, and the rotation of the photosensitive drum 16 is controlled by the gear 16a through the gear 16a. The power is transmitted to each gear, and the charging roller 17 and the developing roller 19 are rotated. The camshaft 22 and the one-way bearing 22
a, eccentric cam 23, gears 25 and 70, and motor gear 27
This constitutes an image forming unit moving means.

Reference numeral 100 denotes a stopper, and when the image forming units 12Y, 12M, 12C, and 12K are rotated counterclockwise and moved from the retracted position to the image forming position, one of the frames 24 at a predetermined position. Of the image forming units 12Y and 12Y
The rotation of M, 12C and 12K is stopped. A slit disk 29 is fixed to the other end of the camshaft 22, and a slit 29 a is formed in the slit disk 29. The position of the eccentric cam 23 can be known by detecting the slit 29a by the photo sensor 30.

The transport belt 20 is made of a high-resistance semiconductive plastic film, is formed in a seamless endless shape, and has a drive roller 3 as a drive means.
1. It is stretched between the driven roller 32 and the stretching roller 33. Note that the resistance value of the transport belt 20 is such that when the recording medium 21 is attracted to the transport belt 20 by electrostatic force and the recording medium 21 is separated from the transport belt 20, the static electricity remaining on the transport belt 20 is natural. Is set to be in a range where static electricity is removed.

The drive roller 31 is connected to a second motor (not shown), and the drive motor 31 is driven by an arrow f by the second motor.
Rotated in the direction. The tension roller 33 is urged in the direction of arrow g by a spring (not shown), and the conveying belt 20 is always tensioned by the urging force. The upper half portion 20a of the transport belt 20 is passed over the transfer portions of the first to fourth printing mechanisms P1 to P4, and the stretching roller 33 is sandwiched across the lower half portion 20b of the transport belt 20.
And the tip of the cleaning blade 34 are brought into contact with each other.

The cleaning blade 34 is made of a flexible rubber or plastic material, and scrapes toner adhered to the surface of the conveyor belt 20 into a waste toner tank 35. A paper feed mechanism 36 is provided on the lower right side of the color image recording apparatus 11 in the drawing, and the paper feed mechanism 36 includes a paper storage cassette, a hopping mechanism, and a registration roller 4.
5, the paper storage cassette includes a recording medium storage box 37, a push-up plate 38, and pressing means 39. The hopping mechanism comprises a discriminating means 40, a spring 41, and a paper feed roller 42.

In this case, the recording medium 21 accommodated in the recording medium accommodation box 37 is pressed against the paper feed roller 42 via the push-up plate 38 by the pressing means 39, and discriminated against the paper feed roller 42 by the spring 41. The sheets are discriminated one by one by means 40. When the feed roller 42 is rotated in the direction of arrow h by a third motor (not shown) in this state, the recording medium 21 sandwiched between the feed roller 42 and the discriminating means 40 is guided by guides 43 and 44. Then, it is sent to the registration roller 45.

Subsequently, when the registration roller 45 is rotated in the direction of the arrow, the recording medium 21
And between the conveyor belt 20. The suction roller 47 is pressed against the driven roller 32 via the conveyance belt 20, charges the recording medium 21 conveyed by the paper feed mechanism 36, and causes the conveyance belt 20 to be attracted to the conveyance belt 20 by electrostatic force. For this purpose, the suction roller 47 is made of a high resistance semiconductive rubber material. Note that a photo sensor 101 that detects the front end of the recording medium 21 is provided upstream of the suction roller 47 in the transport direction of the recording medium 21.

Further, a static eliminator 102 is provided so as to face the drive roller 31 via the transport belt 20. The static eliminator 102 neutralizes the recording medium 21 adsorbed and sent to the transport belt 20, releases the attracted state, and facilitates separation from the transport belt 20. And the recording medium 2
A photo sensor 103 for detecting the rear end of the recording medium 21 is located downstream of the static eliminator 102 in the first transport direction.
a is provided.

Further, a guide 10 is provided downstream of the photosensor 103a in the conveying direction of the recording medium 21.
4 and a fixing device 48 for fixing a color toner image. The fixing device 48 includes a heat roller 49 as a rotating body that heats the toner on the recording medium 21, and a pressure roller 50 as a rotating body that presses the recording medium 21 toward the heat roller 49. The heat roller 49 and the pressure roller 50 form a fixing section therebetween, and are rotated in the direction of the arrow by driving the second motor.

The heat roller 49 has an elastic layer made of silicone rubber or the like formed on a mandrel made of aluminum or the like by 1 to 2 [m].
m], and a release layer made of PFA, ETFE, or the like, having a thickness of 100 μm on the elastic layer to prevent offset.
m]. Also,
The pressure roller 50 is formed by coating an elastic layer of silicone rubber or the like on a mandrel of aluminum or the like, and a release layer of PFA, ETFE or the like is formed on the mandrel at 3 to 100 [ μm]. In this case, the pressure roller 50 has no elastic layer.

A thermistor 80 is provided in contact with the heat roller 49, the temperature of the heat roller 49 is detected by the thermistor 80, and a heater (not shown) in the heat roller 49 is turned on / off according to the detected temperature.
It can be turned off. Further, at a predetermined distance from the fixing device 48, for example, a pyroelectric type temperature sensor 81 utilizing a pyroelectric effect as a jam detecting means is disposed, and the fixing device 48 and the temperature sensor 81 are provided.
Mirrors 82 and 83 are provided on the optical path of the infrared light between.

When the infrared light generated by the heat roller 49 is incident on the temperature sensor 81 via the mirrors 82 and 83, the temperature sensor 81 is heated by the incident infrared light. A temperature change on the surface of the surface 49 is detected. The mirror 82 is provided so as to receive and reflect infrared light from the downstream side of the fixing unit in the rotation direction of the heat roller 49 and the upstream side of the thermistor 80.

For example, when the recording medium 21 causes an offset phenomenon when passing through the fixing unit and is wound around the heat roller 49, the recording medium 21 is interposed between the heat roller 49 and the mirror 82. , Temperature sensor 8
The infrared light incident on 1 changes. Therefore, the temperature sensor 81 detects the recording medium 2 wound around the heat roller 49.
1 is detected.

Therefore, a control device (not shown), based on a change in temperature detected by the temperature sensor 81,
It is determined that a jam has occurred in the fixing device 48. Note that an oil roller, an oil pad, or the like may be provided in contact with the heat roller 49, and the offset prevention liquid may be supplied by the oil roller, the oil pad, or the like. Further, instead of the temperature sensor 81, a reflection type photo sensor can be used.

Further, a discharge port 51 is provided downstream of the fixing device 48 in the conveying direction of the recording medium 21.
A discharge stacker (not shown) is provided outside the discharge port 51. The recording medium 21 after the color image is formed,
It is discharged to the discharge stacker via the discharge port 51. Next, the operation of the color image recording apparatus 11 having the above configuration will be described.

First, when the power supply (not shown) of the color image recording apparatus 11 is turned on, the controller performs predetermined initial settings, and then energizes a heater (not shown) in the fixing device 48 to perform warm-up, thereby performing heat-up. The temperature of the roller 49 is set to the set temperature. At this time, the temperature of the heat roller 49 is detected by the thermistor 80, and the on / off control of the heater is performed in accordance with the detected temperature.

When the temperature of the heat roller 49 reaches a set temperature, a color image signal is transmitted from an external device (not shown), that is, a host computer, to the color image recording device 11, and the color image recording device 11 receives the color image signal. The color image signal is a yellow image signal,
A magenta image signal, a cyan image signal, and a black image signal are decomposed, and each yellow image signal, magenta image signal,
The cyan image signal and the black image signal are stored in memories (not shown).

Here, when the yellow image signal, the magenta image signal, the cyan image signal, and the black image signal are all obtained when the color image signal is decomposed,
Images of each color are formed by the image forming units 12Y, 12M, 12C, and 12K. Then, each image forming unit 12
Y, 12M, 12C, and 12K are placed at image forming positions, and each photoconductor drum 16 and each transfer roller 14Y, 14M, 14
C and 14K are pressed against each other via the conveyance belt 20, and the first motor 28 and the second motor are driven to operate the image forming units 12Y, 12M, 12C and 12K, and the conveyance belt 20 is moved to the photosensitive drum. The vehicle is driven at a speed substantially equal to the peripheral speed of No. 16. As a result, a toner image of each color is formed on each photosensitive drum 16, and each toner image is transferred to the recording medium 21 in a superimposed manner.

When the color image signal is decomposed,
If any of the yellow image signal, magenta image signal, cyan image signal, and black image signal is absent, an image of the corresponding color is not formed. For this purpose, a predetermined image forming unit is placed at the retracted position, and toner images of each color are formed only by the other image forming units. That is, the first motor 2 of the image forming unit to be placed at the retreat position
When the gear 8 is driven in the reverse direction to rotate the gear 25 in the direction of the arrow t, the one-way bearing 22a is locked, and the camshaft 22 and the eccentric cam 23 are rotated in the direction of the arrow t. At this time, the eccentric cam 23 raises the projection plate portion 24b of the frame 24 by the amount of eccentricity, and rotates the predetermined image forming portion clockwise around the projection 24a against the urging force of the spring 17a. When the slit 29a of the slit disk 29 is detected by the photo sensor 30, the first motor 28 is stopped, and the image forming unit is placed at the retracted position. At the retracted position, each photoconductor drum 16 of the image forming unit separates from the transport belt 20 and the corresponding transfer roller.

At this time, as the gear 25 is rotated in the direction of the arrow t, the photosensitive drum 16 is rotated in the direction opposite to the direction of the arrow a, but the speed is reduced by the two-stage gear 26. The rotation amount of the body drum 16 decreases. Therefore, the photosensitive drum 16 and the transport belt 20
Can be suppressed from being worn. Next, when the first motor 28 of the image forming section placed at the retracted position is driven in the forward direction, the photosensitive drum 16 is rotated in the direction of arrow a. At this time, the gear 25 rotates in the direction of arrow s. As a result, the one-way bearing 22a idles. At this time, each image forming unit placed at the retracted position is
is rotated counterclockwise by the urging force of the spring 17a around the center a of the stopper 100.
, The image forming section is stopped at that position and is placed at the image forming position. Thereafter, the one-way bearing 22a idles with the driving of the first motor 28, and the photosensitive drum 16 of each image forming unit continues to rotate in the direction of the arrow a.

At the image forming position, the photosensitive drums 16 of the image forming sections 12Y, 12M, 12C, and 12K are transferred by the transfer roller 14 via the transport belt 20.
Y, 14M, 14C, and 14K are pressed against each other. Next, an operation of forming a color image on the recording medium 21 will be described. First, in a state where the registration roller 45 is stopped, the paper feed roller 42 is rotated in the direction of arrow h, and one recording medium 21 stored in the recording medium storage box 37 is fed out and guided by guides 43 and 44 to perform recording. The medium 21 is conveyed, and even after the front end of the recording medium 21 reaches the registration roller 45, the recording medium 21 is further conveyed by a small amount. Accordingly, the recording medium 21 is slightly bent (bent) by pressing the front end thereof between the registration rollers 45, and the skew of the recording medium 21 is corrected by the bending.

Next, each of the image forming units 12Y, 12M, 12
C, 12K, and drives the first motors 28 of the photosensitive drums 16 of the image forming units 12Y, 12M, 12C, and 12K.
The charging roller 17 and the developing roller 19 are respectively rotated. Thereby, each image forming unit 12Y, 12M, 12
C and 12K are placed in the image forming position as shown in FIGS.

Further, by driving the second motor, the transfer roller 1 is driven.
4Y, 14M, 14C, and 14K, the drive roller 31, the registration roller 45, and the heat roller 49 are rotated, and at the same time, a voltage is applied to the suction roller 47. Since the registration roller 45 is rotated in the direction of the arrow, the front end of the recording medium 21 is
The recording medium 21 is conveyed until the recording medium 21 reaches between the suction roller 47 and the driven roller 3.
2 is attracted to the conveyor belt 20 by the electrostatic force between them. Further, the recording medium 21 is transported as the transport belt 20 travels while being attracted to the transport belt 20.

The recording medium 21 is the first printing mechanism P
When sent to the position just before, the control device sends a yellow image signal for one line to the LED head 13Y of the first printing mechanism P1. The LED head 13Y turns on the LED element corresponding to the sent yellow image signal,
An electrostatic latent image for one line corresponding to the yellow image signal is formed on the surface of the photosensitive drum 16.

In this manner, an electrostatic latent image is sequentially formed on the surface of the photosensitive drum 16 in accordance with the yellow image signal for one line, and the yellow image signal for the length of the recording medium 21 in the sub-scanning direction is statically formed. The exposure ends when the latent image is formed. Subsequently, the surface of the photosensitive drum 16 on which the electrostatic latent image is formed is developed by applying yellow toner by a developing roller 19 to form a yellow toner image on the photosensitive drum 16. You.

When the front end of the recording medium 21 reaches the transfer portion between the photosensitive drum 16 and the transfer roller 14Y, a transfer voltage is applied to the transfer roller 14Y. As a result, the toner image on the photosensitive drum 16 is transferred to the transfer roller 1.
4Y, it is electrically transferred to the recording medium 21. When the one-page yellow toner image is transferred to the recording medium 21, the transfer of the yellow toner image ends.

Since the conveyor belt 20 is continuously running, the recording medium 21 is conveyed from the transfer section of the image forming section 12Y to the transfer section of the image forming section 12M, and the recording medium 21 is transferred in the same manner as the transfer of the yellow toner image. The transfer of the magenta toner image is performed. Further, similarly, the recording medium 21 is conveyed from the transfer section of the image forming section 12M to the transfer section of the image forming section 12C, where the transfer of the cyan toner image is performed, and thereafter, the image forming is performed from the transfer section of the image forming section 12C. The sheet is transported to the transfer section of the section 12K, and the transfer of the black toner image is performed.

In this way, the toner images of the respective colors are sequentially transferred onto the recording medium 21 in a superimposed manner, and become the color toner images. After that, the recording medium 21 is sent to the static eliminator 102 by the transport roller 20 and is neutralized by the static eliminator 102. As a result, the recording medium 21 is easily separated from the transport belt 20, separated from the transport belt 20 above the drive roller 31, guided by the guide 104, and sent to the fixing device 48.

In the fixing device 48, a heat roller 49 having a set temperature at which fixing can be performed, and a pressure roller 50 pressed against the heat roller 49 are used.
The color toner image is fixed on the recording medium 21 to become a color image, and the recording medium 21 is discharged to a discharge stacker through a discharge port 51. This discharge is performed by the photo sensor 1
03a can be known by detecting the rear end of the recording medium 21.

In this way, a color image can be formed on the recording medium 21 fed by the paper feed mechanism 36. Therefore, when forming only a toner image of a predetermined color, the photosensitive drum 16 of the image forming unit of another color can be separated from the transport belt 20 and the recording medium 21, so that the photosensitive drum 16 and the transport belt 20 can be separated. Wear can be suppressed, and the life of the photosensitive drum 16 and the transport belt 20 can be extended. In addition, since the image forming units for other colors are not operated, the deterioration of the toner of other colors can be reduced, and the life of the toner can be prolonged, and the image quality can be improved.

Further, by driving the first motor 28 in the forward direction, the image forming units 12Y, 12M,
12C and 12K can be gradually moved from the retreat position to the image forming position, so that the image forming units 12Y and 12K can be moved.
M, 12C and 12K will not be impacted. When the driving of the first motor 28 in the reverse direction is started, the photosensitive drum 16 is slightly rotated in the reverse direction.
Since the gear is immediately released by the engagement between the gear 71 and the gear 16a, the rotation of the photosensitive drum 16 in the reverse direction does not affect the rotation.

By the way, when the recording medium 21 on which the color toner image is formed passes through the fixing unit, an offset phenomenon occurs, and as shown in FIG. As a result, the recording medium 21 is interposed between the recording medium 21 and the infrared light incident on the temperature sensor 81, and a change in the temperature of the surface of the recording medium 21 is detected.

The control device includes a temperature sensor 81
Fixing device 48 based on the temperature change detected by
, The operation of the color image recording apparatus 11 is stopped. Subsequently, a jam clearing unit (not shown) of the control device includes image forming units 12Y, 12M,
The first motors 28 of 12C and 12K are driven in opposite directions,
The gear 25 is rotated in the direction of arrow t. At this time, the one-way bearing 22a is locked, the rotation of the gear 25 is transmitted to the camshaft 22, and the eccentric cam 23 is rotated in the direction of the arrow t.

As a result, each of the image forming units 12Y, 12M,
12C and 12K are placed in the retracted position as shown in FIG.
Each photoconductor drum 16 is separated from the conveyor belt 20. Further, the jam release unit drives the second motor in the reverse direction to rotate the drive roller 31, the heat roller 49, and the pressure roller 50 in the reverse direction, and the recording medium 21 is moved to the position shown in FIG. , The front end of the recording medium 21 is
When reaching the position located between the image forming unit 12K and the image forming unit 12K, the second motor is stopped.

Then, the control device displays the occurrence of the jam on a display device (not shown). The operator can rotate the upper cover 11a in the direction of arrow w to open it, remove the image forming unit 12K, and remove the recording medium 21 on the transport belt 20. Therefore,
The jam can be easily released. In the present embodiment, when the recording medium 21 is wound around the heat roller 49, the occurrence of the jam is detected, but when the recording medium 21 is wound around the pressure roller 50, Also, it is possible to detect that a jam has occurred.

A static eliminator 102 is provided so as to face the drive roller 31 via the conveyor belt 20.
The static eliminator 102 is configured to neutralize the recording medium 21 adsorbed and sent to the transport belt 20 and release the attracted state to facilitate separation from the transport belt 20, but when the humidity is low, etc. When the electrostatic force is increased, the recording medium 21 may be caught in the lower half portion 20b of the conveyor belt 20 and a jam may occur.

Also in this case, since the recording medium 21 needs to be rewound to clear the jam, the operation is very troublesome. Therefore, a second embodiment of the present invention will be described in which the jam of the recording medium 21 wound on the lower half portion 20b side of the transport belt 20 can be easily released.

FIG. 5 is an enlarged view of a main part of a color image recording apparatus according to a second embodiment of the present invention, and FIG.
FIG. 9 is a diagram illustrating a jam clearing method of the color image recording apparatus according to the embodiment. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. In this case, as shown in FIG. 5, a reflection type photo sensor 84 is provided as a jam detecting unit facing the driving roller 31 via the recording medium 21, and the recording is performed on the lower half portion 20b side of the transport belt 20. When the medium 21 is wound, the recording medium 21 can be detected by the photo sensor 84.

The control device (not shown) determines that a jam has occurred in the transport belt 20 based on a change in the detection signal sent from the photo sensor 84, and stops the operation of the color image recording device 11. Subsequently, the jam clearing means of the control device includes image forming units 12Y, 12M,
The first motors 28 of 12C and 12K are driven in opposite directions,
As shown in FIG. 6, each of the image forming units 12Y, 12M, 12M
C, 12K are placed at the retracted position, and each photosensitive drum 16 is separated from the conveyor belt 20.

The control device drives the second motor (not shown) in the reverse direction to rotate the drive roller 31, the heat roller 49 and the pressure roller 50 in the reverse direction. When the position, that is, the position where the front end of the recording medium 21 reaches the position between the static eliminator 102 and the image forming unit 12K, the second motor is stopped. Then, the control device displays the occurrence of the jam on a display device (not shown). The operator can rotate the upper cover 11a in the direction of arrow w to open it, remove the image forming unit 12K, and remove the recording medium 21 on the transport belt 20. Therefore, the jam can be easily released.

In each of the above embodiments, the LED head 13 is used as a means for exposing the surface of the photosensitive drum 16 to light.
Y, 13M, 13C, 13K are used, but LED
In place of the heads 13Y, 13M, 13C, and 13K, a laser, a liquid crystal shutter, or the like can be used. In each of the embodiments, the camshaft 22 (FIG. 3), the one-way bearing 22a, the eccentric cam 23, the gears 25 and 70, and the motor gear 27 constitute an image forming unit moving unit. The image forming unit moving means may be constituted by a rack and pinion or the like.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0064]

As described above in detail, according to the present invention, in a color image recording apparatus, a transport belt that is transported by a driving means and transports a recording medium, and is disposed facing the transport belt. A plurality of image forming units, each of which takes a retreat position and an image forming position, and forms a toner image on a photosensitive drum when placed at the image forming position; and A transfer unit disposed to face the drum, an image forming unit moving unit that selectively positions each of the image forming units at the retracted position and the image forming position, and a jam detecting unit that detects that a jam has occurred. And a jam canceling unit that, when the jam detecting unit detects that a jam has occurred, places each of the image forming units in the retracted position and causes the transport belt to run in the reverse direction.

In this case, the image forming unit moving means
Since each image forming unit can be selectively placed at the retreat position and the image forming position, when forming only a toner image of a predetermined color, the photosensitive drums of the other color image forming units are conveyed to the conveyance belt and the recording belt. Can be separated from media. Therefore, wear of the photosensitive drum and the transport belt can be suppressed, and the life of the photosensitive drum and the transport belt can be extended. Further, since the image forming units for other colors are not operated, deterioration of the toners of other colors can be reduced, and the life of the toners can be prolonged.
Image quality can be improved.

Then, when a jam occurs, the occurrence of the jam is detected by the jam detecting means, and the jam clearing means places each of the image forming units at the retracted position and moves the transport belt in the reverse direction. Therefore, the operator opens the upper cover, removes the image forming unit,
Since the recording medium on the conveyor belt can be removed,
The jam can be easily released.

[Brief description of the drawings]

FIG. 1 is a first schematic diagram of a color image recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a second schematic diagram of the color image recording apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view of an image forming unit located at an image forming position according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a jam clearing method of the color image recording apparatus according to the first embodiment of the present invention.

FIG. 5 is an enlarged view of a main part of a color image recording apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a jam clearing method of the color image recording apparatus according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Color image recording apparatus 12Y, 12M, 12C, 12K Image formation part 14Y, 14M, 14C, 14K Transfer roller 16 Photoreceptor drum 20 Conveyor belt 21 Recording medium 22 Cam shaft 22a One-way bearing 23 Eccentric cam 25, 70 Gear 27 Motor gear 31 Drive roller 48 fixing device 49 heat roller 50 pressure roller 81 temperature sensor 84 photo sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Yabuki 4--11-22 Shibaura, Minato-ku, Tokyo Inside the company's offshore data (72) Inventor Nao Ono 4--11-21 Shibaura, Minato-ku, Tokyo Shares In company offshore data

Claims (3)

[Claims] 1. An image forming apparatus comprising: (a) a transport belt that is transported by a driving unit to transport a recording medium; and (b) is disposed to face the transport belt, and has a retracted position and an image forming position. A plurality of image forming units for forming a toner image on the photosensitive drum when placed at the forming position; and (c) a transfer unit arranged to face each of the photosensitive drums via the transport belt. (D) an image forming unit moving means for selectively placing each of the image forming units at a retreat position and an image forming position; (e) a jam detecting means for detecting that a jam has occurred; A color image recording apparatus comprising: a jam canceling unit that places each of the image forming units at a retracted position when the detection unit detects that a jam has occurred and causes the transport belt to run in a reverse direction. . 2. The color image recording apparatus according to claim 1, wherein said jam detecting means is provided so as to face a rotating body of a fixing device. 3. The color image recording apparatus according to claim 1, wherein said jam detecting means is disposed so as to face a conveyor belt.