JP2013152443A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further shorten a first print time in an image forming apparatus having a plurality of image forming means in which each of the forming means has a photoreceptor.SOLUTION: There is provided an image forming apparatus which comprises: detection means 54 for detecting light which is emitted from a light source 81c of a second image forming means and reflected by a rotary polygon mirror 53; and adjusting means 40 for performing the adjustment operation of the rotational speed of the rotary polygon mirror 53 on the basis of the output of the detection means 54, wherein the adjusting means causes the light source 81c of the second image forming means to emit light to perform the adjustment operation during a period including at least a period in which light is irradiated to a photoreceptor 22c of the second image forming means before a first image forming means performs the image forming operation and the first image forming means starts to move a developing member 24d to a developing position before completing the adjustment operation.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material such as a sheet.

  Conventionally, in this type of image forming apparatus, the rotational polygon is rotated so that the rotational speed of the rotary polygon mirror that is rotationally driven by the scanner motor becomes the speed for performing the image forming operation before performing the printing operation on the recording material. Adjust the mirror speed (start up the scanner motor). At this time, in order to detect the rotation speed of the rotary polygon mirror, there is a configuration in which the period of the horizontal synchronizing signal detected when the laser is forced to emit light is used.

  In this configuration, when starting up the rotary polygon mirror, the laser is always emitted from the time when the scanner motor is started to monitor the horizontal synchronization signal. Alternatively, the laser is forcibly emitted after waiting for the scanner motor to reach the target speed. Then, a horizontal synchronization signal is detected at the time of forced light emission, and the rotation speed of the scanner motor (rotating polygon mirror) is detected by looking at the period of the detected signal, and the speed is adjusted to execute the image forming operation. As described above, when the rotating polygon mirror is raised, the laser beam exposes the photosensitive member (image carrier) while the laser is forcibly emitted to detect the rotation speed of the rotating polygon mirror. For this reason, when the developing roller is in contact with the photosensitive member or a developing bias is applied to the developing device, toner adheres to the photosensitive member. Then, unnecessary toner is transferred to a transfer unit that transfers toner to a recording material that directly contacts the photoconductor, or a transfer unit that transfers toner to a recording material that carries toner from the photoconductor via a belt or the like. . As a result, there is a concern that a toner different from the toner image formed on the recording material may adhere and become dirty when the recording material is passed.

Therefore, Patent Document 1 proposes that a weak electric bias is applied by a developing device so that the photosensitive member is hardly developed even when exposed to laser light.
Patent Document 2 discloses an in-line color image forming apparatus provided with a mechanism capable of contacting and separating the developing device from the photosensitive member, and the developing device is separated from the photosensitive member so that toner does not adhere to the photosensitive member. A configuration is proposed in which the developing device is brought into contact with the photosensitive member immediately before image formation.
In Patent Document 3, a safety area is provided so as not to expose the photoconductor with laser light so that it does not overlap the image area on the surface of the photoconductor. When the scanner motor is started up, the laser is emitted only in the safety area for calibration. It has been proposed to implement.

Japanese Patent Laid-Open No. 7-306626 JP 2007-93771 A US Pat. No. 5,864,355

However, in order to prevent the back side of the recording material from becoming dirty due to the exposure of the photosensitive member by the laser light, when a weak electric bias is applied to the developing device as in Patent Document 1, switching from the weak electric bias to the normal bias is performed. Therefore, the image forming operation cannot be executed immediately after the laser forced light emission ends. For this reason, there is a concern that the first print time (FPOT), which is the time from when the print request is received until the first recording material is discharged outside the apparatus, becomes long. In addition, when exposure is performed with a laser beam with a very high amount of light, even if a weak electric bias is applied, some toner adheres to the photosensitive member and develops, resulting in contamination on the back side of the recording material. Concerned.
Further, as in Patent Document 2, when the developing device is kept in a state of being separated from the photosensitive member so that toner does not adhere to the photosensitive member, and the developing device is brought into contact with the photosensitive member immediately before image formation, the developing device is attached to the photosensitive member. The timing of contact must be after waiting for completion of start-up of the scanner motor that performs forced laser emission, and then inadvertently shifting to a state where the photoconductor is not exposed. For this reason, there is a concern that the first print time may become longer as described above.
Further, as in Patent Document 3, when an area that does not overlap with the image area on the surface of the photoreceptor is calculated and the laser is emitted, it is difficult to cope with a rapid change in the speed of the rotary polygon mirror. May expose the image area on the surface of the photoreceptor. In addition, there is a concern that the scanner motor may become uncontrollable when a horizontal synchronization signal cannot be obtained in an area that does not overlap the image area on the surface of the photoreceptor. For this reason, it is necessary to keep the acceleration of the rotating polygon mirror within a certain range so that the rotating polygon mirror does not fluctuate rapidly. In this case, it takes time to finish adjusting the speed of the rotating polygon mirror. There is a concern that the print time will become longer.

  An object of the present invention is to further reduce the first print time while preventing the recording material from being soiled in an image forming apparatus having a plurality of image carriers.

In order to achieve the above object, the present invention provides:
First and second image forming units each including a photoconductor, a light source that emits light, and a developing member that can move to a developing position and a position retracted from the developing position, and a light source of the first and second image forming units And each of the first and second image forming means reflects the light emitted from the respective light source to the respective photosensitive members by the rotary polygon mirror. In an image forming apparatus capable of executing an image forming operation of forming a latent image by irradiation and developing the latent image with toner by each developing member at the developing position.
Detection means for detecting light emitted from the light source of the second image forming means and reflected by the rotary polygon mirror, and adjustment for executing an adjustment operation for adjusting the speed of the rotary polygon mirror based on the output of the detection means Means,
The adjusting unit includes a light source for the second image forming unit in a period including at least a period during which light is irradiated to the photosensitive member of the second image forming unit before the first image forming unit performs an image forming operation. The first image forming means starts moving the developing member to the developing position before finishing the adjusting operation.

  According to the present invention, in the image forming apparatus having a plurality of image carriers, the above prior art can be further developed and the first print time can be further shortened.

Sectional drawing which shows schematic structure of the image forming apparatus of Example 1. FIG. FIG. 3 is a perspective view illustrating a schematic configuration inside the scanner unit according to the first embodiment. Explanatory drawing of the timing of the sequence for printing from the print request of Example 1 The block diagram of the electric circuit applied by control of Example 1 Sectional drawing which shows schematic structure of the image forming apparatus of Example 2. FIG. The perspective view which shows schematic structure inside the scanner unit of Example 2. FIG. Explanatory drawing of the timing of the sequence for printing from the printing request of Example 2 The block diagram of the electric circuit applied by control of Example 2 The perspective view which shows schematic structure inside the scanner unit of Example 3. FIG. Explanatory drawing of the timing of the sequence for printing from the printing request of Example 3 The block diagram of the electric circuit applied by control of Example 3

DETAILED DESCRIPTION Exemplary embodiments for carrying out the invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.
The present invention relates to an image forming apparatus, and in particular, in an electrophotographic image forming apparatus using oscillation light from a semiconductor laser as a light source for image exposure, the rising of a rotating polygon mirror is detected at the period of a horizontal synchronizing signal of laser light. The present invention relates to an image forming apparatus (particularly a laser printer). More specifically, the present invention relates to an image forming apparatus having an optical scanning device that irradiates a laser beam corresponding to a photoconductor (photosensitive drum) as a plurality of image carriers.

The image forming apparatus of Example 1 will be described below.
(Image forming device)
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus 10 according to the present exemplary embodiment. In this embodiment, a four-drum color image forming apparatus will be described as an example of the image forming apparatus 10.
Hereinafter, an image forming operation for forming an image on a recording material, which can be executed by the image forming apparatus 10 of the present embodiment, will be described.
First, after the leading end position of the recording material 12 fed by the pickup roller 13 is detected by the registration sensor 11, the transporting operation is temporarily stopped at a position where the leading ends slightly pass through the pair of transport rollers 14 and 15.

On the other hand, the scanner unit 80 disposed below the photoconductors 22a to 22d (22a, 22b, 22c, and 22d) sequentially applies laser beams (light beams) 21a to 21d to the photoconductors 22a to 22d that are rotationally driven. Irradiate. At this time, since the photoconductors 22a to 22d are previously charged by the charging rollers 23a to 23d, electrostatic latent images are formed on the surfaces of the photoconductors by the irradiation of the laser beams 21a to 21d. The electrostatic latent images are developed using toner (developer) in the order of the photosensitive members 22d, 22c, 22b, and 22a by the developing units 25a to 25d and the developing sleeves 24a to 24d as developing members. A toner image (developer image) is formed on the surface.
The developing sleeves 24a to 24d can be brought into contact with and separated from the photoconductors 22a to 22d (contactable and separable, movable) in order to suppress wear of the developing sleeves 24a to 24d disposed in the developing units 25a to 25d. Mechanism is provided. A position where the developing sleeves 24a to 24d are in contact with the photosensitive members 22a to 22d is defined as a developing position, and a position apart from the photosensitive members 22a to 22d is defined as a retracted position where the developing sleeves 24a to 24d are retracted from the developing position.

  The toner images formed on the photosensitive members 22a to 22d are primary transfer nip portions T1 formed by the primary transfer rollers 26a to 26d and the photosensitive members 22a to 22d, respectively, and are endless belts as intermediate transfer members. The images are sequentially superimposed and transferred onto an intermediate transfer belt 30. As shown in FIG. 1, the intermediate transfer belt 30 is sandwiched between the photosensitive members 22a to 22d and the primary transfer rollers 26a to 26d and is in contact with the photosensitive members 22a to 22d. The intermediate transfer belt 30 is driven by rollers 31, 32, and 33 to convey the toner image to a secondary transfer nip T 2 formed between the intermediate transfer belt 30 and the secondary transfer roller 27. At this time, the conveyance of the recording material 12 is resumed at the secondary transfer nip T2 between the secondary transfer roller 27 and the intermediate transfer belt 30 so that the timing coincides with the toner image conveyed by the intermediate transfer belt 30. . The toner image is transferred from the intermediate transfer belt 30 to the recording material 12 by the secondary transfer roller 27 at the secondary transfer nip T2.

  Thereafter, the unfixed toner image on the recording material 12 is heated and fixed to the recording material 12 by the fixing roller pair 16 and 17 in the fixing device 18. Then, the recording material 12 on which the toner image is heat-fixed is output (discharged) outside the apparatus. Here, the toner that has not been transferred from the intermediate transfer belt 30 to the recording material 12 by the secondary transfer roller 27 is collected in the waste toner container 36 by the cleaning blade 35.

(Scanner unit configuration of Example 1)
Next, the configuration of the scanner unit (irradiation means, optical scanning means) in the image forming apparatus 10 of this embodiment will be described with reference to FIG. FIG. 2 is a perspective view showing a schematic configuration inside the scanner unit 80. In FIG. 2, for convenience of explanation, a cover 82 that roughly seals the inside of the scanner unit 80 and that includes a plate-like glass 56 through which a light beam passes is shown.

  As shown in FIG. 2, in the scanner unit 80, laser light source devices 81a to 81d serving as two light sources are arranged two-dimensionally in two rows on the left and right sides, and also in two rows on the top and bottom. Laser light emitted from the laser light source devices 81a to 81d is applied to a rotating polygon mirror 53 as a deflecting unit having a deflecting reflecting surface in the vicinity of a linear image of a light beam formed by being condensed by an integrally formed cylindrical lens 52. Is done. The scanner unit 80 is provided with a scanner motor 55 as drive means for driving the rotary polygon mirror 53 to rotate. When the rotary polygon mirror 53 is rotationally driven by the scanner motor 55, the laser light emitted from the laser light source devices 81a to 81d is incident on the deflection reflection surface of the rotation polygon mirror 53 and reflected by the deflection reflection surface. Thus, deflection scanning is performed. The laser light source devices 81a and 81b are incident on the same deflection reflection surface (same surface) at the same timing. Similarly, the laser light source devices 81c and 81d are also incident on the same deflection reflection surface (same surface) at the same timing.

  Further, the scanner unit 80 has lenses 84L, 84R, 85L, 85R, 86L, 86R and mirrors 87L, 87R, 88L, 88R, 89L so as to be substantially symmetrical in the left-right direction in FIG. , 89R are disposed.

In FIG. 2, the laser beams 21a to 21d deflected by the rotating polygon mirror 53 rotating at a high speed in the CCW (counterclockwise) direction are imaged on each photoconductor and scanned as follows.
Laser beams 21c and 21d emitted from two laser light source devices 81c and 81d arranged on the left side in the figure are scanned in the direction of arrow S1 on the photosensitive members 22c and 22d. On the other hand, the laser beams 21a and 21b emitted from the two laser light source devices 81a and 81b arranged on the right side in the drawing are scanned in the direction of the arrow S2 on the photosensitive members 22a and 22b. Therefore, the laser beams 21c and 21d and the laser beams 21a and 21b are scanned in the opposite directions (images are formed). A part of the laser light emitted from the laser light source device 81c is deflected by the rotary polygon mirror 53 and then irradiated to the horizontal synchronization detecting means 54, thereby generating a horizontal synchronization signal.

Here, the horizontal synchronization detecting means 54 detects a laser beam for irradiating the photoconductor 22c, and generates a horizontal synchronization signal that serves as a reference for the timing at which formation of an electrostatic latent image on the photoconductor 22c is started. This corresponds to first horizontal synchronizing signal output means for outputting. The photoconductor 22d corresponds to a first image carrier on which a toner image that is first transferred to the intermediate transfer belt 30 is formed when toner images on a plurality of photoconductors (on the image carrier) are sequentially superimposed. To do. In addition, the photosensitive member on which the toner image that is first transferred to the intermediate transfer belt 30 when the toner images on the plurality of photosensitive members are sequentially overlapped receives a print request (image formation request, print request). First, the photosensitive member starts forming an electrostatic latent image. The photoconductor 22c corresponds to any one of the plurality of photoconductors excluding the photoconductor 22d.
Further, one photosensitive member 22, the developing sleeve 24 corresponding to the photosensitive member 22, and the laser light source device 81 correspond to one image forming unit (station).

(Explanation of timing until printing starts)
The sequence for printing (image forming operation) after receiving a print request will be described below.
FIG. 3 is a diagram for explaining the timing of the print sequence from the print request executed by the engine controller 40 in the image forming apparatus 10 of the present embodiment. FIG. 4 is a block diagram of an electric circuit applied in a printing sequence from a printing request in the image forming apparatus 10 of the present embodiment. Here, before the start of printing, the developing sleeves 24a to 24d are in a state of being separated (retracted) from the photoreceptors 22a to 22d, respectively.

  The engine controller 40 that has determined that the print signal has been turned on starts control of the fixing heater 19 so that the temperature of the fixing device 18 becomes the fixing possible temperature. Then, in order to start the rotation control of the scanner motor 55 for rotating the rotary polygon mirror 53, the ON signal of the scanner motor 55 is made true, and the main motor 43 is turned on to start the main motor 43 of the photosensitive members 22a to 22d. The signal is made true (T201). When it is detected that the main motor 43 has reached a predetermined (predetermined, preset) rotational speed and has become stable, the laser light source devices 81a to 81d emit light (ON), and the laser light amounts of the laser light source devices 81a to 81d The laser drivers 50a to 50d as the light amount adjusting means are controlled to adjust the light amount so that becomes a predetermined light amount (T202).

  When it is confirmed that the laser light amount of the laser light source devices 81a to 81d has reached the predetermined light amount, the ON signal of the development contact / separation motor 44 is made true (T203). As a result, the developing sleeves 24a to 24d sequentially come into contact with the photosensitive members 22a to 22d (reach the developing position) in the order of 24d, 24c, 24b, and 24a. That is, the operation of moving from the developing sleeve 24d to the developing position contacting the corresponding photosensitive member in order is started. Further, the recording material 12 is present in the feeding cassette 102 and it is determined by the signal from the recording material presence / absence sensor 41 (FIG. 4) that the feeding is possible, and the pickup solenoid 42 (FIG. 4) is turned on to turn on the recording material 12. Is fed (T203).

  The developing sleeves 24a to 24d are controlled so as to come into contact with the photoreceptors 22a to 22d immediately before the electrostatic latent image is formed in order to extend the life, and consideration is given to reducing the amount of wear as much as possible. Therefore, the developing sleeves 24d, 24c, 24b, and 24a are contacted in the order of the developing sleeves 24d, 24c, 24b, and 24a while the surface of the intermediate transfer belt 30 is shifted by the time Tn for moving the distance between the photosensitive members.

After a predetermined time has elapsed from the ON signal of the scanner motor 55, the engine controller 40 performs an adjustment operation for adjusting the rotation speed of the scanner motor 55 to a specified rotation speed that is a rotation speed for executing the image forming operation. That is, it is detected whether the scanner motor 55 has reliably reached the specified rotational speed. For this reason, the following determination is made. That is, the laser light source device 81c is forced to emit light (ON), and the horizontal synchronization circuit 57 determines the period of the horizontal synchronization signal detected by the horizontal synchronization detection means 54 (T204).
Here, the engine controller 40 that makes a determination at the timing of T204 calculates a value corresponding to the rotation speed of the rotary polygon mirror 53 using the horizontal synchronization signal output from the horizontal synchronization detection means 54, and the rotary polygon mirror 53. This corresponds to determination means for determining whether or not the number of rotations (rotation speed) has reached a preset number of rotations (rotation speed). Note that the slower the rotational speed of the rotary polygon mirror 53, the longer the period of the horizontal synchronization signal. As described above, the laser light source device 81c emits light so that a value corresponding to the rotation speed of the rotary polygon mirror 53 can be calculated by detecting the horizontal synchronization signal a plurality of times by the horizontal synchronization detection unit 54 when forced light emission is performed. Continue to (ON). in this way,
The forced light emission for detecting the rotation speed of the rotary polygon mirror 53 emits light in a situation where the rotation speed of the rotary polygon mirror and the direction of the reflecting surface are unknown. Therefore, the period of forced light emission (ON) includes at least the period during which light from the laser light source device 81c is irradiated onto the photosensitive member 22c. However, as shown in FIG. 3, during this period, the developing sleeve 24c is not in contact with the photosensitive member 22c, so that the toner adheres to the photosensitive member 22c even when the light from the laser light source device 81c is irradiated to the photosensitive member 22c. There is no end to it. Therefore, of course, the toner is not transferred from the photosensitive member 22 c onto the intermediate transfer belt 30 and attached to the secondary transfer roller 27.
In order to detect whether or not the scanner motor 55 has reached the specified rotational speed, when the laser light source device 81c is caused to emit light, the amount of laser light is changed until it is confirmed that there is no abnormality in the period of the horizontal synchronization signal. The horizontal synchronization signal may be detected in a state where the horizontal synchronization signal is lowered to such an extent that it can be detected. Thereby, it can reduce that the surface of a photoreceptor deteriorates by irradiating light.

If the period of the horizontal synchronizing signal is not a predetermined period (not reaching the specified rotational speed), the scanner motor 55 is accelerated and / or decelerated to adjust the rotational speed. When it is confirmed that the period of the horizontal synchronizing signal has reached a predetermined period (having reached the specified rotational speed), the adjustment operation is completed. Further, it is determined that the fixing device 18 has reached a predetermined fixing temperature (T205).
As shown in FIG. 3, the developing sleeve 24d is in contact with the photosensitive member 22d (has reached the developing position) before the timing (T205) when the adjustment operation is completed. However, since the laser light source device 81d is extinguished (not ON) during the adjustment operation, even if the developing sleeve 24d is in contact with the photosensitive member 22d, toner that causes contamination on the recording material is present on the photosensitive member 22d. There is no sticking to. Of course, toner is not transferred from the photosensitive member 22d onto the intermediate transfer belt 30 that is in contact with the photosensitive member 22d during the adjustment operation, and does not adhere to the secondary transfer roller 27.
In this embodiment, the horizontal synchronization detecting means 54 is disposed in a station (image forming unit) provided with the photosensitive member 22c. As a result, the laser light source device 81c is forced to emit light to detect a horizontal synchronization signal, and after confirming that the scanner motor 55 has reached the specified rotational speed (T205), the developing sleeve 24c contacts the photosensitive member 22c. A sufficient time (interval) Tg until (T207) can be secured. In other words, the developing sleeve 24c can be separated from the photosensitive member 22c during the forced light emission of the laser light source device 81c.
Here, the horizontal synchronization detecting means 54 may be arranged at a station (photosensitive body 22b, 22a) downstream of the rotation direction (surface movement direction) of the intermediate transfer belt 30 from the station of the photosensitive body 22c. Thereby, the time Tg can be made longer.

  After confirming that the determination of T205 has been made within a predetermined time from the print request, the engine controller 40 generates a horizontal synchronization signal for the horizontal synchronization signal of the station where the horizontal synchronization detection means 54 is not provided. Then, the engine controller 40 masks the video signal so that the laser light source devices 81a to 81d do not emit light except for the area where the image can be formed on the recording material 12 and the timing at which the horizontal synchronization detecting means 54 detects the laser light. . Laser light is modulated by the laser light source devices 81a to 81d by the video signal after masking, and exposure is sequentially started from the laser light source device 81d (T206).

  In this way, the image forming operation is started (executed). Here, the engine controller 40 that performs control to start exposure at the timing of T206 corresponds to an execution unit that executes an image forming operation when it is determined that the rotational speed of the rotary polygon mirror 53 has reached a preset rotational speed. To do. The timing from when the image forming apparatus receives the print signal to when the scanner unit starts exposure has been described above.

As described above, in this embodiment, the horizontal synchronization signal output by detecting the laser beam for irradiating the photoconductor 22c other than the photoconductor 22d where the formation of the electrostatic latent image is first started is detected. It is used to determine whether the scanner motor 55 has surely reached the specified rotational speed. Thus, after the developing sleeve 24d starts to abut (moving to the developing position) with respect to the photosensitive member 22d where the electrostatic latent image is first started (T203), the photosensitive member 22d is irradiated with the laser beam. Is no longer exposed. Accordingly, the movement of the developing sleeve 24d to the developing position can be started before the adjustment operation of the scanner motor 55 for forcibly emitting the laser light source device 81c is completed. That is, the start timing of the movement of the developing sleeve 24d to the developing position can be advanced as compared with the configuration in which the adjustment operation of the scanner motor 55 for forcibly emitting the laser light source device 81d is executed.
Therefore, unnecessary toner is developed on the photosensitive member 22 d, and the toner on the photosensitive member 22 d does not contaminate the secondary transfer roller 27 via the intermediate transfer belt 30. That is, the back side of the recording material 12 is not soiled. Further, it is possible to prevent the occurrence of density unevenness in the exposed portion, which has been a concern when the photoconductor is irradiated with laser light. Further, it is possible to prevent horizontal stripes on the photosensitive member that are generated by turning on the laser beam completely to detect the horizontal synchronization signal while the scanner motor is activated.
In this embodiment, the start-up control of the scanner motor 55 is performed at the station of the photoconductor 22c. However, the time Tg from when the scanner motor 55 reaches the specified rotation speed until the developing sleeve 24c comes into contact with the photoconductor 22c. Can be secured sufficiently. Occurrence of a problem that has been a concern due to irradiation of the photosensitive member 22c with laser light can be prevented by using this time Tg (within this time Tg).
As described above, in this embodiment, the scanner is used at the station (second image forming unit) of the photoconductor 22c that executes the image forming operation after the station (first image forming unit) of the photoconductor 22d that executes the image forming operation. The start-up control (adjustment operation) of the motor 55 is performed. Therefore, the movement of the developing sleeve 24d to the developing position can be started before the adjustment operation of the scanner motor 55 for forcibly emitting the laser light source device 81c is completed. For this reason, when the scanner motor 55 reaches the specified rotational speed (after the adjustment operation of the scanner motor 55 is completed), the image forming operation on the photosensitive member 22d can be started immediately.
Therefore, according to the present embodiment, the developing sleeve 24d starts to move to the developing position as compared with the case where the start-up control of the scanner motor 55 is performed at the station of the photosensitive member 22d without adding new parts. The timing to do is advanced. For this reason, it is possible to shorten the first print time.

In the present embodiment, the laser light source device 81d is turned off (not ON) during the period from T203 to T206, but is not limited thereto. That is, even when the surface potential of the photosensitive member 22d is such that the surface potential of the photosensitive member 22d is such that the toner does not adhere even if the developing sleeve 24d is in contact with the photosensitive member 22d, the photosensitive member 22d is irradiated with light. Good.
In this embodiment, an intermediate transfer type image forming apparatus for transferring a toner image from each of the photoconductors 22a to 22d onto the intermediate transfer belt 30 and transferring the toner image from the intermediate transfer belt 30 to a recording material will be described. However, it is not limited to this. That is, the present invention is also suitable for an image forming apparatus of a type in which a toner image is directly transferred from each of the photoreceptors 22a to 22d to a recording material carried and transported on a transport belt that can contact each of the photoreceptors 22a to 22d. Can be applied.

The image forming apparatus of Example 2 will be described below. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, and the description is abbreviate | omitted.
FIG. 5 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present exemplary embodiment. The present embodiment is different from the first embodiment in that a first scanner unit 70a and a second scanner unit 70b are provided as shown in FIG. Here, the first and second scanner units have the same configuration. The first and second scanner units 70a and 70b are configured to irradiate laser beams on the corresponding photoreceptors by image signals separated into two colors from one rotary polygon mirror to form full-color images. ing.

(Scanner unit configuration of Example 2)
FIG. 6 is a diagram for explaining a schematic configuration inside the second scanner unit 70b in the present embodiment. Here, of the first and second scanner units 70a and 70b, the second scanner unit 70b will be described, but the first scanner unit 70a has the same configuration. Further, in FIG. 6, for convenience of explanation, a cover that roughly seals the inside of the second scanner unit 70 b and that includes a plate-like glass through which a light beam passes is shown.

  In the drawing, laser light emitted from laser light source devices 81 d and 81 c (laser light source devices 81 b and 81 a in the first scanner unit 70 a) disposed vertically is transmitted through the cylindrical lens 52 and then the rotating polygon mirror 53. It is condensed on the same reflecting surface. The rotary polygon mirror 53 is rotationally driven at high speed by the scanner motor 55b, and deflects the incident laser light in the same direction. The deflected laser light passes or reflects through the lenses 74, 75c, and 75d and the mirrors 87, 88, and 89, and is condensed and scanned on the respective photoreceptors 22c and 22d to form an electrostatic latent image.

In the figure, reference numeral 54b denotes a light receiving element constituting a horizontal synchronization detecting means, which is disposed at a position where the laser light of the laser light source device 81c for exposing the photosensitive member 22c of the two lasers can be detected. A horizontal synchronization signal obtained from the light receiving element is transmitted to a laser drive substrate (not shown), whereby the modulation timing of the laser light source devices 81d and 81c can be determined, and an image can be formed at a desired position on the photoconductor.
For convenience of explanation, it is assumed that the horizontal synchronization detecting means of the first scanner unit 70a is 54a, and detection is performed with a part of the laser light 21a emitted from the laser light source device 81a.

(Explanation of timing until printing starts)
A printing sequence after receiving a print request will be described below.
FIG. 7 is a diagram for explaining the timing of the print sequence from the print request executed by the engine controller 40 in the image forming apparatus of the present embodiment. FIG. 8 is a block diagram of an electric circuit applied in a print sequence from a print request in the image forming apparatus of this embodiment.

The engine controller 40 that has determined that the print signal has been turned on starts control of the fixing heater 19 so that the temperature of the fixing device 18 becomes a fixing possible temperature. Then, the ON signal of the scanner motors 55b and 55a is made true in order to start the rotation control of the scanner motors 55b and 55a as driving means for driving the rotary polygon mirror 53 to rotate. Further, the ON signal of the main motor 43 is made true in order to start up the main motor 43 of the photoconductors 22a to 22d (T301).
When it is detected that the main motor 43 has reached a predetermined rotational speed and is in a stable state, the laser light source devices 81a to 81d are controlled to control the laser light quantity of the laser light source devices 81a to 81d so that the laser drivers 50a to 50a as light quantity adjusting means. The light amount is adjusted by controlling 50d (T302).

  When it is confirmed that the laser light amount of the laser light source devices 81a to 81d has reached the predetermined light amount, the ON signal of the development contact / separation motor 44 is made true (T303). As a result, the developing sleeves 24a to 24d sequentially come into contact with the photosensitive members 22a to 22d in the order of 24d, 24c, 24b, and 24a. Further, the recording material 12 is present in the feeding cassette 102, and it is judged from the signal of the recording material presence / absence sensor 41 (FIG. 8) that the feeding is possible, and the pickup solenoid 42 (FIG. 8) is turned on to turn on the recording material 12. Is fed (T303).

  The developing sleeves 24a to 24d are controlled so as to come into contact with the photoreceptors 22a to 22d immediately before the electrostatic latent image is formed in order to extend the life, and consideration is given to reducing the amount of wear as much as possible. . Therefore, the intermediate transfer belt 30 contacts with the photoconductor in order from the developing sleeve 24d by shifting by the time Tn for moving between the photoconductors.

  After a predetermined time has elapsed from the ON signal of the scanner motors 55b and 55a, the following determination is made in order to detect whether the scanner motors 55b and 55a have reached the specified rotational speed. That is, the laser light source devices 81c and 81a emit light, and the horizontal synchronization circuits 57b and 57a determine the period of the horizontal synchronization signal detected by the horizontal synchronization detection means 54b and 54a (T304).

When it is confirmed that there is no abnormality in the cycle of the horizontal synchronizing signal, it is determined that the fixing unit 18 has reached a predetermined fixing temperature (T305).
After confirming that the determination in T305 is made within a predetermined time from the print request, the engine controller 40 generates a horizontal synchronization signal for the horizontal synchronization signal of the station where the horizontal synchronization detection means 54b and 54a are not provided. The The engine controller 40 masks the video signal so that the laser light source devices 81a to 81d do not emit light except for the area where the image can be formed on the recording material 12 and the timing at which the laser light is detected by the horizontal synchronization detecting means 54b and 54a. To do. The laser light is modulated by the laser light source devices 81a to 81d by the video signal after masking, and the exposure is sequentially started from the laser light source device 81d (T306). In this way, the image forming operation is started (executed).
The timing from when the image forming apparatus receives the print signal to when the scanner unit starts exposure has been described above.

As described above, also in the present embodiment, it is possible to obtain the same effect as in the first embodiment.
In this embodiment, the start-up control of the scanner motor is also performed at the station of the photosensitive member 22a, but the interval between T305 and the timing T308 at which the developing sleeve 24a contacts the photosensitive member 22a is longer than the time Tg. For this reason, the back surface of the recording material 12 is not soiled at the station of the photosensitive member 22a. Here, the time Tg is the same as that in the first embodiment, and is the time from T305 until the developing sleeve 24c comes into contact with the photosensitive member 22c (T307). As in the present embodiment, the same effect as in the first embodiment is obtained even in a form in which a plurality of scanner units are included in the image forming apparatus.

The image forming apparatus of Example 3 will be described below. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, 2, and the description is abbreviate | omitted.
FIG. 9 is a perspective view for explaining a schematic configuration inside the scanner unit 60 of the present embodiment. In the present embodiment, the scanner unit 60 as shown in FIG. 9 is mounted and the control method of the scanner unit is different from the first embodiment. Here, for convenience of explanation, FIG. 9 shows a state in which the cover 82 that roughly seals the inside of the scanner unit 60 and that includes the plate-like glass 56 through which the light beam passes is removed. .

(Scanner unit configuration of Example 3)
As shown in FIG. 9, the scanner unit 60 is provided with laser light source devices 81a to 81d, a cylindrical lens 52, a rotary polygon mirror 53, and a scanner motor 55, as in FIG. Further, in the scanner unit 60, lenses 84L, 84R, 85L, 85R, 86L, 86R and mirrors 87L, 87R, 88L, 88R, 89L, 89R are also arranged as in FIG.

Here, one horizontal synchronization detecting means 54 is provided in the scanner unit 80 of the first embodiment. On the other hand, in the scanner unit 60 of this embodiment, two horizontal synchronization detecting means 54e and 54f are provided.
The horizontal synchronization detecting means 54e is disposed at a position where the laser light of the laser light source device 81d that exposes the photosensitive member 22d can be detected. The horizontal synchronization detection means 54f is disposed at a position where the laser beam of the laser light source device 81a that exposes the photosensitive member 22a can be detected. Here, the horizontal synchronization detection means 54e corresponds to a second horizontal synchronization signal output means, and the horizontal synchronization detection means 54f corresponds to a first horizontal synchronization signal output means. In this embodiment, the photoconductor 22a corresponds to a second image carrier.

The horizontal synchronization signals obtained from the horizontal synchronization detection means 54e and 54f are transmitted to a laser drive substrate (not shown), whereby the modulation timing of the laser light source devices 81a to 81d is determined, and an image is formed at a desired position on the photoreceptor. The
In this embodiment, the horizontal synchronizing means is arranged at two places, but the present invention is not limited to this. If the horizontal synchronization detecting means is provided at the station of the photosensitive member 22d where the formation of the electrostatic latent image is started first, at least one of the other stations is provided with the horizontal synchronization detecting means. Anything is acceptable.

(Explanation of timing until printing starts)
A printing sequence after receiving a print request will be described below.
FIG. 10 is a diagram for explaining the control timing from the print request to the start of printing executed by the engine controller 40 in the image forming apparatus of the present embodiment. FIG. 11 is a block diagram of an electric circuit applied in a print sequence from a print request in the image forming apparatus of this embodiment.

T401 to T403 shown in FIG. 10 are the same as T201 to T203 described with reference to FIG.
In the present embodiment, after a predetermined time has elapsed from the ON signal of the scanner motor 55, the following determination is performed in order to detect whether the scanner motor 55 has reliably reached the specified rotational speed. That is, the laser light source device 81a emits light, and the horizontal synchronization circuit 57f determines the period of the horizontal synchronization signal detected by the horizontal synchronization detection means 54f (T404).
When it is confirmed that there is no abnormality in the period of the horizontal synchronizing signal, it is determined that the fixing device 18 has reached a predetermined fixing possible temperature (T405).

  In this embodiment, after confirming that the determination of T405 has been made within a predetermined time from the print request, the means for detecting the laser beam 21d exposed to the photosensitive member 22d and outputting a horizontal synchronization signal is provided. The synchronization detection unit 54f is switched to the horizontal synchronization detection unit 54e. Then, the engine controller 40 masks the video signal so that the laser light source device 81d does not emit light except for the region where an image can be formed on the recording material 12 and the timing at which the horizontal synchronization detecting means 54e detects the laser light. The video signal after masking is modulated by the laser light source device 81d and exposure is started (T406).

On the other hand, for each of the photoconductor 22c and photoconductor 22b stations that are not provided with the horizontal sync detection means, the engine controller 40 generates a horizontal sync signal after confirming that T405 is within a predetermined time. Be started. Thereafter, the engine controller 40 performs video so that the remaining laser light source devices 81a, 81b, and 81c do not emit light except for the region where an image can be formed on the recording material 12 and the timing at which the horizontal synchronization detecting means 54f detects the laser light. Mask on signal. The video signal after masking modulates laser light with the remaining laser light source devices 81a, 81b, 81c, and starts exposure in the order of the laser light source devices 81c, 81b, 81a. Here, in this embodiment, the time Tg is the time from T405 until the developing sleeve 24a comes into contact with the photosensitive member 22a (T408). T407 is the timing at which the developing sleeve 24c comes into contact with the photosensitive member 22c.
The timing from when the image forming apparatus receives the print signal to when the scanner unit starts exposure has been described above.

  As described above, also in the present embodiment, it is possible to obtain the same effect as in the first embodiment. In addition, in this embodiment, the following effects can be obtained. In the configuration of the first embodiment, the horizontal synchronization signal generated by the engine controller 40 is used in the station of the photoreceptor 22d. On the other hand, in this embodiment, the horizontal synchronization detecting means 54e is provided on the photosensitive member 22d where the formation of the electrostatic latent image is started first. When the scanner motor 55 reaches the specified rotational speed and the image forming operation on the photosensitive member 22d is started, the horizontal synchronization detecting unit 54e uses a horizontal synchronizing signal for forming an electrostatic latent image on the photosensitive member 22d. Output is used. This eliminates the need to wait for the engine controller 40 to generate a horizontal synchronization signal at the station of the photoreceptor 22d. Therefore, the first print time can be further reduced as compared with the configuration of the first embodiment.

  22a to 22d ... photosensitive member, 40 ... engine controller, 53 ... rotating polygon mirror, 54 ... horizontal synchronization detecting means, 81a to 81d ... laser light source device

Claims (10)

First and second image forming units each including a photoconductor, a light source that emits light, and a developing member that can move to a developing position and a position retracted from the developing position, and a light source of the first and second image forming units And each of the first and second image forming means reflects the light emitted from the respective light source to the respective photosensitive members by the rotary polygon mirror. In an image forming apparatus capable of executing an image forming operation of forming a latent image by irradiation and developing the latent image with toner by each developing member at the developing position.
Detection means for detecting light emitted from the light source of the second image forming means and reflected by the rotary polygon mirror, and adjustment for executing an adjustment operation for adjusting the speed of the rotary polygon mirror based on the output of the detection means Means,
The adjusting unit includes a light source for the second image forming unit in a period including at least a period during which light is irradiated to the photosensitive member of the second image forming unit before the first image forming unit performs an image forming operation. The image forming apparatus is characterized in that the first image forming unit starts moving the developing member to the developing position before ending the adjusting operation.   The image forming apparatus according to claim 1, wherein the developing member of the second image forming unit is in a position retracted from the developing position while the adjustment operation is being performed.   3. The image forming apparatus according to claim 1, wherein after the adjustment operation is finished, an image forming operation by the first image forming unit and an image forming operation by the second image forming unit are executed.   An endless belt capable of contacting the photoreceptors of the first and second image forming units, and the photoreceptor of the second image forming unit is more belt-like than the photoreceptor of the first image forming unit; The image forming apparatus according to claim 3, wherein the image forming apparatus is disposed on the downstream side in the rotation direction.   5. The developing member of the second image forming unit is made to reach the developing position before the image forming operation by the second image forming unit is performed after the adjustment operation is completed. The image forming apparatus described.   The light source of the first image forming unit is not caused to emit light until the adjustment operation is completed after the first image forming unit starts moving the developing member to the developing position. The image forming apparatus according to any one of 1 to 5.   While the operation of moving the developing member of the first image forming unit to the developing position is performed, the light source of the first image forming unit is of a light quantity that does not cause toner to adhere to the photosensitive member of the first image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus emits light.   8. The image according to claim 1, wherein light emitted from each of the light sources of the first and second image forming units is incident on the same surface of the rotary polygon mirror at the same timing. 9. Forming equipment.   The first and second image forming units each have an endless belt that can contact the photosensitive member, and the adjustment operation is performed while the belt is in contact with the photosensitive member of the first image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the developing position is a position where the developing member contacts the corresponding photosensitive member.

Images