Image forming apparatus

Abstract

To reduce the time required for an operation to change the number of revolutions of a scanner motor involving forced light emission.SOLUTION: An ASIC controls to perform a light emission operation in which an area including an image forming area of a photoconductor drum is irradiated with a laser beam from a light source, thereby controlling to allow execution of a changing operation for changing the rotation speed of a rotary polygon mirror from a first rotation speed (24803 rpm) to a second rotation speed (35433 rpm) different from the first rotation speed, performs the light emission operation while the photoconductor drum and a developing roller are in contact with each other and the photoconductor drum and the developing roller rotate (vi), and performs the changing operation based on a result of detection performed by a BD in the light emission operation (ii).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a rotating polygon mirror that scans a photosensitive member with a laser beam.

Background Art

[0002] Conventionally, when continuously printing various media and performing a printing operation in which a plurality of process speeds and resolutions are mixed, it is necessary to switch the rotation speed of the scanner motor. In this case, printing is temporarily stopped to switch the rotation speed of the scanner motor. In an image forming apparatus that performs such switching, a technique is known in which the rotation speed of the scanner motor is detected by forcibly emitting a laser beam for a predetermined time when the scanner motor is started up (hereinafter referred to as forced emission). Further, for example, Patent Document 1 discloses a technique for shortening the first printout time under the restriction that the laser beam is forcibly emitted only when the photosensitive drum and the developing means are separated.

[0003] On the other hand, in order to print various media at once, the number of cases where a printing operation in which a plurality of process speeds and resolutions are mixed is increasing. However, when a plurality of process speeds are mixed, it takes time to switch the rotation speed of the scanner motor. In response to the problem of time-consuming switching, for example, Patent Document 2 discloses the following technique. That is, in Patent Document 2, when there are reservations with different process speeds, the reservations are rearranged so that the number of switches is minimized, or printing is performed at the lowest print speed within the reservations, thereby preventing a decrease in overall productivity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the problem that the switching operation of the rotation speed of the scanner motor with forced light emission takes time still exists. The reason why the switching operation takes time is that when switching the rotation speed of the scanner motor with forced light emission, it is necessary to stop the members related to image formation and separate the photosensitive drum from the developing means.

[0006] The present invention has been made under such circumstances, and an object thereof is to further shorten the time required for the switching operation of the rotation speed of the scanner motor with forced light emission.

Means for Solving the Problems

[0007] In order to solve the above-described problems, the present invention has the following configuration. (1) Scanning means including a light source, a rotating polygon mirror that deflects the laser light emitted from the light source and is emitted, and first driving means for driving the rotation of the rotating polygon mirror; control means for controlling the light source and the first driving means; A photoreceptor on which an electrostatic latent image is formed by the laser light emitted from the scanning means, and the photoreceptor on Developing means for developing the electrostatic latent image formed thereon with toner to form a toner image; an intermediate transfer member onto which a toner image formed on the photoreceptor is primarily transferred by the developing means, primary transfer means for primarily transferring the toner image onto the intermediate transfer member, and secondary transfer means for forming a secondary transfer nip with the intermediate transfer member, the secondary transfer means for secondarily transferring the toner image onto a recording material when the toner image primarily transferred onto the intermediate transfer member passes through the secondary transfer nip, and secondary transfer voltage applying means for applying a voltage to the secondary transfer means; Comprising an image forming apparatus , a first image forming period during which a first electrostatic latent image is formed while the rotating polygon mirror rotates at a first rotational speed, a second image forming period during which a second electrostatic latent image is formed while the rotating polygon mirror rotates at a second rotational speed different from the first rotational speed, and a non-image forming period between the first image forming period and the second image forming period, during the non-image forming period, in a state where the photoreceptor and the developing means are rotating while in contact with each other A light emission operation in which the laser light is irradiated from the light source to an area including the image formation area of the photoreceptor the control means controls the light source so as to perform the above, and during the non-image forming period, without stopping the rotation of the rotating polygon mirror The rotation speed of the rotating polygon mirror the From the first rotation speed to the record first Switching operation to switch to the second rotation speed the control means controls the first driving means so as to perform the above Controlling When the polarity of the voltage applied to the secondary transfer means by the secondary transfer voltage applying means is a first polarity when the toner image corresponding to the first electrostatic latent image in the first image forming period or the toner image corresponding to the second electrostatic latent image in the second image forming period passes through the secondary transfer nip, the third electrostatic latent image formed when the light emission operation is performed during the non-image forming period is developed, and after the toner image corresponding to the third electrostatic latent image is primarily transferred onto the intermediate transfer member, the polarity of the voltage applied to the secondary transfer means by the secondary transfer voltage applying means during the period when the toner image corresponding to the third electrostatic latent image passes through the secondary transfer nip is a second polarity opposite to the first polarity. An image forming apparatus characterized by this.

Effects of the Invention

[0008] According to the present invention, it is possible to further shorten the time required for the switching operation of the rotation speed of the scanner motor with forced light emission.

Brief Description of the Drawings

[0009]

Figure 1

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Modes for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, modes for carrying out this invention will be exemplarily described in detail. However, dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are to be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions, and are not intended to limit the scope of this invention to the following embodiments.

Examples

[0011] In Example 1, an intermediate transfer full-color image forming apparatus will be described as an example. Here, in the intermediate transfer full-color image forming apparatus, the toner image on the photosensitive drum is transferred once to an intermediate transfer belt (intermediate transfer member) (hereinafter referred to as primary transfer), and then transferred from the intermediate transfer belt onto a recording material (hereinafter referred to as secondary transfer) to form a full-color image.

[0012] <Description of the Apparatus> First, the image forming process will be described using the schematic cross-sectional views of the main parts of the apparatus shown in FIGS. 1 and 2. A charging roller 102 is in contact with the surface of a photosensitive drum 101 which is a photoreceptor. The charging roller 102 charges the photosensitive drum 101 to a uniform potential by applying a charging voltage (charging process). A scanner unit 103 forms an electrostatic latent image on the surface of the charged photosensitive drum 101 (latent image process). A developing roller 104 which is a developing means is in contact with the photosensitive drum 101. The developing roller 104 develops the toner corresponding to the electrostatic latent image on the photosensitive drum 101 by applying a developing voltage (developing process) to form a toner image. The developing roller 104 is housed in a developing container 105 in which the toner is stored. Note that the developing roller 104 and the photosensitive drum 101 are controlled by a contact / separation mechanism 130 which is a contact / separation means to be in a contact state which is a first state in which these two members are in contact and a separation state which is a second state in which they are separated. Also, the developing roller 104 and the photosensitive drum 101 are rotationally driven by a drive motor 120 which is a second driving means. Further, the conveyance of the recording material S is performed by a conveyance roller (not shown) which is a conveyance means arranged on a conveyance path (not shown). The conveyance roller (not shown) is also driven by the drive motor 120.

[0013] The primary transfer roller 106, which is the primary transfer means, is pressed against the photosensitive drum 101 via the intermediate transfer belt 107 which is the clamping and conveying member. The primary transfer roller 106 transfers the toner image to the intermediate transfer belt 107 by applying a primary transfer voltage by a primary transfer voltage applying means (not shown) (primary transfer process). The toner remaining on the photosensitive drum 101 in the primary transfer process moves to the drum cleaning blade 108 which is the image carrier cleaning means by the rotation of the photosensitive drum 101, and is removed from the photosensitive drum 101. The drum cleaning blade 108 is stored in the waste toner container 109 together with the cleaned toner. In the first embodiment, the photosensitive drum 101, the charging roller 102, the developing roller 104, the developing container 105, the drum cleaning blade 108, and the waste toner container 109 are collectively referred to as the cartridge 100.

[0014] The image forming process up to this point is performed in the order of yellow (y), magenta (m), cyan (c), and black (k) when forming an image of a plurality of colors, for example, four colors, and a multicolor image is formed on the intermediate transfer belt 107. In FIG. 2, each color is illustrated as 101y, 101m, 101c, and 101k if it is the photosensitive drum 101. In FIG. 1, since the main part of one cartridge 100 has been described, the y, m, c, and k representing the color at the end of the reference numeral are not shown. Also, except when explaining members or the like of a specific color, the symbol at the end will be omitted hereinafter.

[0015] The multicolor image formed in this manner is transferred by a secondary transfer roller 110, which is a secondary transfer means, to a recording material S conveyed in the conveyance direction from a paper feed cassette (not shown) (secondary transfer process). A secondary transfer voltage is applied to the secondary transfer roller 110 from a secondary transfer voltage source 140, which is a secondary transfer voltage application means. Note that the secondary transfer voltage source 140 can apply voltages of both positive and negative polarities. A fixing device 112 fixes the toner image unfixed to the recording material S as a permanent image (fixing process). The toner remaining on the intermediate transfer belt 107 in the secondary transfer process is removed from the intermediate transfer belt 107 by a belt cleaning blade 111, which is an intermediate transfer body cleaning means. The above control is performed by a control unit 200.

[0016] <Scanner unit> Next, the scanner unit 103 will be described with reference to FIG. 3. The scanner unit 103 includes a laser 301, which is a light source that emits laser light, a rotating polygon mirror 302 that deflects the laser light, and a scanner motor 303, which is a first driving means for rotationally driving the rotating polygon mirror 302. The laser 301, the rotating polygon mirror 302, and the scanner motor 303 function as scanning means. The rotating polygon mirror 302 reflects the laser light emitted from the laser 301 and periodically scans the photosensitive drum 101 (on the photoreceptor) via a folding mirror 304.

[0017] The scanner unit 103 is provided with a BD 305, which is a detection means. When the laser light is irradiated on the position of the BD 305, the BD 305 generates a main scanning synchronization signal 306. The main scanning synchronization signal 306 is used for detecting the rotation period of the rotating polygon mirror 302 and as a reference for determining the image writing position in the main scanning direction. Here, the main scanning direction is the direction in which the laser light is scanned. Also, the direction orthogonal to the main scanning direction (the rotation direction of the photosensitive drum 101) is called the sub-scanning direction.

[0018] The scanner unit 103 includes an ASIC 300 which is a control means for controlling the scanner unit 103. The ASIC 300 communicates with a CPU (not shown) of the control unit 200 and controls the scanner unit 103 according to an instruction from the CPU. A main scanning synchronization signal 306 which is a result of detecting laser light by the BD 305 is input to the ASIC 300. The ASIC 300 receives the main scanning synchronization signal 306 and outputs a scanner motor drive signal 307 for rotating the scanner motor 303 and a laser light drive signal 308 for lighting the laser 301. In this way, the ASIC 300 controls the rotation speed of the scanner motor 303 based on the detection result of the BD 305.

[0019] The rotation speed control is started when the CPU receives a print start command transmitted from an external device such as a personal computer. The scanner motor 303 is driven in an acceleration mode in which it accelerates at a predetermined rotational acceleration at the start of the rotation speed control. After a certain arbitrary time has elapsed since the rotation speed control was started, the ASIC 300 continuously emits light from the laser 301 and measures the rotation speed of the rotary polygon mirror 302 based on the main scanning synchronization signal 306 output by the BD 305. That is, the ASIC 300 performs a detection operation (hereinafter referred to as forced light emission) of detecting laser light in a state where at least a part of the laser light irradiates the image formation area on the photosensitive drum 101. Note that the image formation area in the present invention refers to an area in the longitudinal direction where the photosensitive drum 101 is irradiated with laser light and a latent image can be formed. Here, the longitudinal direction of the photosensitive drum 101 is the rotation axis direction of the photosensitive drum 101 and is also the main scanning direction.

[0020] When the rotation speed (rotational velocity) of the scanner motor 303 reaches a predetermined target rotation speed (target rotational velocity), the ASIC 300 switches the rotation speed control to the light emission control for causing the laser 301 to emit light outside the image formation area. The light emission control outside the image formation area is the control for not causing the laser to emit light within the image formation area of the photosensitive drum 101 and causing the laser to emit light only near the BD 305 outside the image formation area. Note that the reason for causing the laser to emit light within the image formation area (the area including the image formation area) in the forced light emission is that since the rotation speed changes at any time during the period of transitioning the rotation speed of the scanner motor 303 to the predetermined target rotation speed, it is difficult to cause the laser to emit light aiming only at the outside of the image formation area. The forced light emission is not limited to the acceleration at the start of the control. For example, it is similarly required during the acceleration or deceleration when switching the target rotation speed of the scanner motor 303.

[0021] Further, when the image forming apparatus of Example 1 conveys a paper with a low basis weight such as plain paper, for example, it operates at a process speed of, for example, 200 mm / second which is the second process speed. On the other hand, when the image forming apparatus of Example 1 conveys a paper with a high basis weight such as cardboard, for example, it operates at a process speed of 140 mm / second which is a first process speed slower than the second process speed. The rotation speed of the scanner motor 303 when operating at the second process speed is, for example, 35433 rpm which is the second rotation speed. On the other hand, the rotation speed of the scanner motor 303 when operating at the first process speed is, for example, 24803 rpm which is a first rotation speed different from the second rotation speed. Note that the effect of the present invention is not limited to the case where the rotation speed of the scanner motor 303 is two. The same effect can be obtained as long as it has at least two rotation speeds of the scanner motor 303. Note that the ASIC 300 and the control unit 200 can communicate with each other, and the ASIC 300 performs the light emission control of the laser 301, the rotation speed control of the scanner motor 303, etc. according to an instruction from the control unit 200.

[0022] <Operation of Example 1> Using the chart shown in FIG. 4, the switching operation of the process speed in Example 1 will be described. When continuous printing is performed from thick paper to plain paper, an example will be used in which the rotation speed of the scanner motor 303 with forced light emission is switched without performing the separation operation between the photosensitive drum 101 and the developing roller 104 or the stop of the drive motor 120. FIG. 4(i) shows the above-described image forming process such as the Y latent image process. Note that Y, M, C, and K indicate the processes of each color. FIG. 4(ii) shows the rotation speed (such as 24803 rpm) and state (acceleration, forced light emission, etc.) of the scanner motor 303 of each color scanner unit 103. FIG. 4(iii) shows the primary transfer voltage (+560 V, etc.), and FIG. 4(iv) shows the secondary transfer voltage (+700 V, etc.). FIG. 4(v) shows the process speed (such as 140 mm / s) and state (speed switching, etc.) by the drive motor 120. FIG. 4(vi) shows the state (such as the developing contact state) of the contact / separation mechanism 130. The horizontal axis indicates time.

[0023] The upper part of the chart in FIG. 4 shows the implementation timing of the image forming process used for the explanation. The first half shows the image forming process for thick paper, and the second half shows the image forming process for plain paper. As described above, the image forming process is executed in the order of the charging process, latent image process, developing process, primary transfer process, secondary transfer process, and fixing process. Note that the charging process and the developing process are omitted from the chart in FIG. 4.

[0024] Each image forming process will be described. The Y latent image process of the chart indicates the time period during which the photosensitive drum 101y for yellow is irradiated with laser light for image formation. The Y primary transfer process of the chart indicates the time period during which the toner on the photosensitive drum 101y is transferred to the intermediate transfer belt 107. The same applies to magenta, cyan, and black. The secondary transfer process of the chart indicates the time period during which the multicolor toner image formed on the intermediate transfer belt 107 is transferred to the recording material S. Also, the fixing process of the chart is the time period during which the toner image transferred to the recording material S is fixed. Since the faster the process speed, the shorter the time required for each process, the time required for the image forming process on plain paper is shorter than that on thick paper.

[0025] The lower part of the chart shows the operating status of each member. Each color scanner unit 103 shows the rotation speed of the scanner motor 303 and the time period during which forced light emission is performed. The primary transfer voltage and the secondary transfer voltage show the applied voltage and the time period during which it is applied. The drive motor 120 shows the process speed at which it is driving and the time period for speed switching. The contact separation mechanism 130 shows the contact and separation state between the developing roller 104 and the photosensitive drum 101.

[0026] (Switching of process speed) The start of the process speed switching operation is performed starting from the timing 401 of the end of the yellow latent image process. First, from the timing 401 when the yellow latent image process ends, the rotation speed of the scanner motor 303y is accelerated from 24803 rpm to 35433 rpm to perform the switching operation. At the timing 402 when the time T401 has elapsed since the start of acceleration at the timing 401, the forced emission of the laser 301 is started. The time T401 is the time estimated that the scanner motor 303 accelerates to, for example, -10% of the target rotation speed even under the slowest conditions from the start of acceleration, and is determined by experiments. When the time T402 has elapsed from the timing 402 when the forced emission (emission operation) is started, the scanner motor 303y reaches the target rotation speed of 35433 rpm, and the forced emission ends at the timing 403. The same operation is performed in the order of magenta, cyan, and black. The drive motor 120 starts acceleration (speed switching) to switch the process speed from 140 mm / s to 200 mm / s starting from the timing 404 when the fixing process of the thick paper is completed.

[0027] On the other hand, since the developing roller 104 and the photosensitive drum 101 are in contact, from the timing 402 when the forced emission of the scanner motor 303y is started, a toner image is formed on the photosensitive drum 101y by the forced emission. During this time, a primary transfer voltage of the same polarity as during image formation on the thick paper (for example, +560 V) is applied to the primary transfer roller 106. For this reason, the formed toner image is transferred to the intermediate transfer belt 107 and reaches the secondary transfer roller 110 at the timing 405 after the time T403 has elapsed from the timing 402 when the forced emission is started. Note that the applied voltage is not limited to the value of the first embodiment, and any value can be used as long as the toner image can be transferred to the intermediate transfer belt 107.

[0028] When the toner image reaches the secondary transfer roller and a voltage of the same polarity as during image formation (e.g., +700 V) remains applied, toner will adhere to the secondary transfer roller 110. If toner adheres to the secondary transfer roller 110, it will cause smudging on the back side of the plain paper to be printed next. Here, backside smudging refers to the phenomenon where the surface on the side opposite to the side where the toner image is formed on the recording material S becomes dirty. Therefore, from the timing 405 when the yellow toner image reaches the secondary transfer roller 110, a voltage of the opposite polarity (e.g., negative polarity, e.g., -500 V) to that during image formation (e.g., positive polarity) is applied to the secondary transfer roller 110. By applying a voltage of the opposite polarity, adhesion of toner to the secondary transfer roller 110 is prevented. The arrival of the toner image at the secondary transfer roller 110 continues from the timing 406 when the forced emission of black ends until the timing 407 when the time T404 has elapsed. For this reason, it is necessary to continuously apply a voltage of the opposite polarity to the secondary transfer roller 110 from timing 405 to timing 407. That is, during the period when the toner image on the intermediate transfer belt 107 (on the intermediate transfer medium) passes through the secondary transfer roller 110, it is necessary to maintain the application of a voltage of the opposite polarity to the secondary transfer roller 110. The toner on the intermediate transfer belt 107 that has passed through the secondary transfer roller 110 is removed by the belt cleaning blade 111. Note that as a means for avoiding toner adhesion to the secondary transfer roller 110, the following configuration may also be used. That is, an approach and separation mechanism (approach / separation mechanism) between the secondary transfer roller 110 and the intermediate transfer belt 107 may be added, and the approach / separation mechanism may be configured to perform a temporary separation operation of the secondary transfer roller 110 from the intermediate transfer belt 107.

[0029] The image forming process for plain paper starts at timing 408 when the switching of the process speed of drive motor 120 is completed. The primary transfer voltage is also switched to the applied voltage for plain paper (e.g., +800V) at the same timing 408. The image forming process for plain paper is the same as that for thick paper except for the rotation speed of scanner motor 303 being 35433 rpm, the process speed being 200 mm / second, the primary transfer voltage being +800V, and the secondary transfer voltage being +1000V. The time from timing 404 when the fixing process before the switching of the rotation speed of scanner motor 303 is completed to timing 408 when the latent image process after the switching starts is defined as the switching time Tc. The switching time Tc in Example 1 is 0.9 seconds.

[0030] <Effect of Example 1> The effect of Example 1 will be described. For comparison, it will be described using the chart of FIG. 5 showing the conventional process speed switching operation. Note that the charts from (i) to (vi) correspond to the charts from (i) to (iv) of FIG. 4. The start of the process speed switching operation is performed starting from timing 1101 when the black primary transfer process is completed. First, the developing separation operation starts at timing 1101 when the black primary transfer process is completed and ends at timing 1102 when time T1101 has elapsed. During this period, the primary transfer voltage and the secondary transfer voltage are stopped in accordance with timing 1103 when the secondary transfer process is completed. The drive motor 120 is also stopped in accordance with timing 1104 when the fixing process is completed. On the other hand, the developing contact operation starts at timing 1102 when the developing separation operation ends and ends at timing 1105 when time T1102 has elapsed from timing 1102.

[0031] As preparation for image formation on plain paper, the driving of scanner motor 303 is started in advance at timing 1106 so that forced light emission is completed (reaches the target rotation speed) by timing 1105 when the developing contact operation is completed. Also, the drive motor 120 is driven in advance at timing 1108 so as to reach a predetermined speed by timing 1107 when forced light emission starts (starting operation).

[0032] The image forming process on plain paper starts in accordance with the timing 1105 when the developing contact operation is completed. The primary transfer voltage is applied in advance at timing 1109 so as to reach a predetermined voltage (for example, +800V) by the start of the yellow primary transfer process. The secondary transfer voltage is also applied in advance at timing 1110 so as to reach a predetermined voltage (for example, +1000V) by the start of the secondary transfer process. From the above, the switching time Tc of the conventional operation from timing 1104 to timing 1105 was 3.2 seconds (>0.9 seconds).

[0033] As described so far, by switching the rotation speed of the scanner motor 303 in the state where the developing roller 104 is in contact, the switching time Tc can be shortened from 3.2 seconds to 0.9 seconds. Therefore, even when the basis weight of the recording material S is different during continuous printing and it is necessary to switch the process speed, it is not necessary to stop the drive motor 120 or perform the developing separation / contact operation, and the reduction in productivity can be minimized.

[0034] <Modification Example 1> In Example 1, the switching operation in which the target rotation speed of the scanner motor 303 increases was taken as an example for explanation. However, the effect of the present invention is not limited to the case where the rotation speed increases. For example, the same effect can be obtained even in a switching operation in which the target rotation speed decreases, such as from plain paper to thick paper. The same applies to other embodiments other than Example 1.

[0035] <Modification Example 2> In Example 1, an example in which the cleaning means of the intermediate transfer member is a cleaning blade was described. However, the shortening of the switching time, which is an effect of the present invention, can be obtained even with configurations other than the cleaning blade. For example, after discharging the toner image with a charging brush that contacts the intermediate transfer belt, the toner image is transferred to the photosensitive drum at the primary transfer unit and removed by the image carrier cleaning means, and the same effect can be obtained. The image carrier cleaning means may be the cleaning blade in Example 1 or a so-called cleanerless configuration in which it is collected by the developing roller. This is the same for other examples other than Example 1.

[0036] <Modification Example 3> In Example 1, an example having a contact-separation means between the developing roller 104 and the photosensitive drum 101 was described. However, the shortening of the switching time, which is an effect of the present invention, can be obtained regardless of the presence or absence of the contact-separation means. This is because the contact-separation means does not operate during the switching operation and is not affected by the presence or absence of the contact-separation means. Even when the present invention is applied to an image forming apparatus without the contact-separation means, the stop and restart can be omitted, so the effect of shortening the switching time can be obtained. This is the same for other examples other than Example 1.

[0037] As described above, according to Example 1, the time required for the switching operation of the rotation speed of the scanner motor accompanied by forced light emission can be further shortened.

Example

[0038] Example 2 will be described by taking a tandem type direct transfer full-color image forming apparatus as an example, in which a toner image on the photosensitive drum 101 is directly transferred to a recording material S conveyed by an electrostatic transfer belt to form a full-color image.

[0039] <Description of the apparatus> The configuration and operation of the cartridge 100 and the scanner unit 103 in Example 2 are the same as those in Example 1. The parts that are different from Example 1 in terms of the configuration and the image forming process will be described with reference to FIG. 6. In Example 2, the toner image formed on the photosensitive drum 101 is directly transferred onto the recording material S, which is one of the sandwich carriers adsorbed and conveyed by the conveying belt 507 serving as one of the sandwich carriers, by the transfer voltage applied to the transfer roller 506, which is the transfer means. Since it is directly transferred onto the recording material S in the primary transfer, unlike Example 1, it has a configuration without a secondary transfer roller. The direct transfer process is sequentially performed for each color, and a multicolor image is formed on the recording material S. The recording material S with the multicolor image formed thereon is separated from the conveying belt 507 and conveyed to the fixing device 112. Thereby, the multicolor image is fixed on the recording material S as a permanent image. Note that the conveying belt 507 is provided with a belt cleaning blade 511 as a first cleaning means for removing the toner on the conveying belt 507 (on the sandwich carrier).

[0040] <Operation of Example 2> Using the chart shown in FIG. 7, the switching operation of the process speed in Example 2 will be described. When continuously printing with thick paper followed by plain paper, an example will be used in which the rotation speed of the scanner motor 303 accompanied by forced light emission is switched without performing the separation operation between the photosensitive drum 101 and the developing roller 104 or the stop of the drive motor 120. It is equivalent to the operation shown in Example 1 except that the secondary transfer process is omitted and the primary transfer process is replaced by a transfer process that directly transfers onto the recording material S.

[0041] The start of the process speed switching operation is initiated from the timing 601 when the yellow latent image process is completed. First, the scanner motor 303y accelerates the rotation speed from 24803 rpm to 35433 rpm starting from the timing 601 when the yellow latent image process ends. Forced emission starts at the timing 602 when the time T601 has elapsed since the start of acceleration at the timing 601. At the timing 603 when the time T602 has elapsed since the start of forced emission at the timing 602, the scanner motor 303y reaches the target rotation speed of 35433 rpm and the forced emission ends. The same operation is carried out in the order of magenta, cyan, and black. The drive motor 120 starts accelerating (speed switching) to 200 mm / sec from the timing 604 when the fixing process for thick paper is completed.

[0042] On the other hand, since the developing roller 104 and the photosensitive drum 101 are in contact, from the timing 602 when the forced emission of the scanner motor 303y starts, a toner image is formed on the photosensitive drum 101y by the forced emission. During this time, a voltage equivalent to that during the image formation on thick paper (for example, +630V) is applied to the transfer roller 506. Therefore, the formed toner image is transferred to the conveyance belt 507. The transferred toner image is removed by the belt cleaning blade 511. The image formation process for plain paper starts from the timing 605 when the speed switching of the drive motor 120 is completed. The switching time Tc in Example 2 is 0.9 seconds. Note that the transfer voltage in the transfer process for plain paper is +900V.

[0043] <Effect of Example 2> The effect of Example 2 will be described. For comparison, it will be described using the chart in FIG. 8 showing the conventional process speed switching operation. It is the same as the conventional operation shown in Example 1 except that the secondary transfer process is omitted and the primary transfer process is replaced by a transfer process in which the primary transfer process is directly transferred to the recording material S.

[0044] The start of the process speed switching operation is initiated at the timing 1201 when the black transfer process is completed. The developing separation operation starts at the timing 1201 when the black transfer is completed and ends at the timing 1202 after the time T1201 has elapsed. The transfer voltage is stopped in accordance with the timing 1201 when the transfer process is completed. The drive motor 120 is stopped in accordance with the timing 1203 when the fixing process is completed. On the other hand, the developing contact operation starts at the timing 1202 when the developing separation operation ends and ends at the timing 1204 after T1202 has elapsed. As preparation for image formation on plain paper, the start-up (acceleration) of the scanner motor 303 is started in advance at the timing 1205 so that the forced light emission is completed by the timing 1204 when the developing contact operation is completed. Also, the drive motor 120 is started in advance at the timing 1207 so as to reach a predetermined speed (200 mm / s) by the timing 1206 when the forced light emission is started (start-up operation). Note that the transfer voltage in the transfer process for thick paper is +630V.

[0045] The image formation process for plain paper starts in accordance with the timing 1204 when the developing contact operation is completed. The application of the voltage is started in advance at the timing 1208 so that the transfer voltage reaches a predetermined voltage (for example, +900V) by the time the yellow transfer process starts. The switching time Tc in the conventional operation was 3.2 seconds (>0.9 seconds).

[0046] As described above, by switching the rotation speed of the scanner motor 303 with the developing roller 104 in contact, the switching time Tc can be shortened from 3.2 seconds to 0.9 seconds. Therefore, even when the basis weight of the recording material S during continuous printing is different and it is necessary to switch the process speed, it is not necessary to stop the drive motor or perform the developing separation / contact operations, and the reduction in productivity can be minimized.

[0047] <Modification Example> In Example 2, an example in which the configuration of the conveyor belt cleaning means is a cleaning blade was described. However, the shortening of the switching time, which is an effect of the present invention, can be obtained even with configurations other than the cleaning blade configuration. For example, a configuration in which toner is removed by applying a cleaning voltage to a recovery brush that contacts the conveyor belt may be used.

[0048] As described above, according to Example 2, the time required for the switching operation of the rotation speed of the scanner motor accompanied by forced light emission can be further shortened.

Example

[0049] Example 3 shows an example in which the present invention is applied to a single-color image forming apparatus of a contact development method that forms a single-color image by directly transferring a toner image formed on a photosensitive drum 101 onto a recording material S. As a feature of Example 3, an operation is performed in which a toner image accompanied by forced light emission is not transferred from the photosensitive drum 101 to a member in the next process.

[0050] <Description of the apparatus> The configurations and operations of the cartridge 100 and the scanner unit 103 in Example 3 are the same as those in Examples 1 and 2. Differences in the configuration and the image forming process from Example 2 will be described with reference to FIG. 9. In Example 3, the toner image formed on the photosensitive drum 101 is directly transferred to the recording material S as a sandwiching carrier by the transfer voltage applied to the transfer roller 706 which is a transfer means. The recording material S on which the single-color image is formed is conveyed to the fixing device 112. Thereby, the single-color image is fixed on the recording material S as a permanent image. A transfer voltage is applied to the transfer roller 706 from a transfer voltage source 150 which is a transfer voltage applying means. Note that the transfer voltage source 150 can apply voltages of both positive and negative polarities.

[0051] <Operation of Example 3> Using the chart shown in FIG. 10, the switching operation of the process speed in Example 3 will be described. An example will be used to describe the switching of the rotation speed of the scanner motor 303 with forced light emission during continuous printing from thick paper to plain paper without performing the separation operation between the photosensitive drum 101 and the developing roller 104 or the stop of the drive motor 120. It is equivalent to the operation shown in Example 2 except that the multicolor transfer process is omitted.

[0052] The start of the switching operation of the process speed is performed starting from the timing 801 when the latent image process is completed. First, from the timing 801 when the latent image process ends, the rotation speed of the scanner motor 303 is accelerated from 24803 rpm to 35433 rpm. Forced light emission starts at the timing 802 when the time T801 has elapsed from the timing 801 when the acceleration starts. At the timing 803 when the time T802 has elapsed from the timing 802 when the forced light emission starts, the scanner motor 303 reaches the target rotation speed of 35433 rpm and the forced light emission ends. The drive motor 120 starts acceleration (speed switching) to 200 mm / sec from the timing 804 when the fixing process of the thick paper is completed.

[0053] On the other hand, since the developing roller 104 is in contact with the photosensitive drum 101, a toner image is formed on the photosensitive drum 101 by forced light emission from the timing 802 when the forced light emission of the scanner motor 303 is started. The toner image reaches the transfer roller 706 at the timing 805 after passing through the time T803 from the timing 802 when the forced light emission is started. At this time, if the voltage of the same polarity as that during image formation (+630 V) is still applied, toner will adhere to the transfer roller 706 which is a member of the next process, resulting in soiling of the back side of the plain paper to be printed next. Therefore, from the timing 805 when the toner image reaches the transfer roller 706, a voltage of the opposite polarity (-500 V) to that during image formation is applied to the transfer roller 706. This prevents the adhesion of toner to the transfer roller 706. Note that the applied voltage is not limited to the value in the third embodiment, and any value can be used as long as the toner image is not transferred to the transfer roller 706. Since the arrival of the toner image at the transfer roller 706 continues from the timing 803 when the forced light emission ends to the timing 806 when the time T804 has elapsed, it is necessary to continuously apply a voltage of the opposite polarity to that during image formation from the timing 805 to the timing 806. That is, the application of the voltage of the opposite polarity is maintained during the period when the toner image on the photosensitive drum 101 passes through the transfer roller 706. The toner image that has passed through the transfer roller 706 is collected by the drum cleaning blade 108 which is the second cleaning means. The image formation process for plain paper starts from the timing 807 when the switching of the speed of the drive motor 120 is completed. After passing through the processes of latent image and transfer, it proceeds to the fixing process. The switching time Tc in the third embodiment is 0.9 seconds.

[0054] <Effects of the Third Embodiment> The effects of Example 3 will be described. For comparison, it will be described using the chart of FIG. 11 showing the switching operation of the conventional process speed. It is equivalent except that the multicolor transfer process is omitted from the conventional operation shown in Example 2. The start of the switching operation of the process speed is performed starting from the timing 1301 when the transfer process is completed. The developing separation operation starts at the timing 1301 when the transfer process is completed and ends at the timing 1302 when the time T1301 has elapsed. The transfer voltage is stopped in accordance with the timing 1301 when the transfer process is completed. The drive motor 120 is stopped in accordance with the timing 1303 when the fixing process is completed. On the other hand, the developing contact operation starts at the timing 1302 when the developing separation operation ends and ends at the timing 1304 when the time T1302 has elapsed. As preparation for image formation on plain paper, the scanner motor 303 is started (accelerated) in advance at the timing 1305 so that the forced light emission is completed by the timing 1304 when the developing contact operation is completed. Also, the drive motor 120 is started in advance (start start) at the timing 1307 so as to reach a predetermined speed (for example, 200 mm / s) by the timing 1306 when the forced light emission is started.

[0055] The image formation process on plain paper starts in accordance with the timing 1304 when the developing contact operation is completed. The transfer voltage is applied in advance at the timing 1308 so as to reach a predetermined voltage (+900 V) by the time the transfer process is started. The switching time Tc in the conventional operation was 3.2 seconds (>0.9 seconds).

[0056] As described so far, by switching the rotation speed of the scanner motor 303 in the state where the developing means is in contact, the switching time Tc can be shortened from 3.2 seconds to 0.9 seconds. Therefore, even when the basis weight of the recording material S is different during continuous printing and it is necessary to switch the process speed, it is not necessary to stop the drive motor 120 or perform the developing separation / contact operations, and the reduction in productivity can be minimized.

[0057] <Modification 1> In Example 3, an operation of not transferring a toner image associated with forced light emission from the photosensitive drum 101 to the transfer roller 706, which is a member of the next process, in a monochromatic image forming apparatus was described as an example. The operation of not transferring to the member of the next process is also applicable to the multicolor image forming apparatuses shown in Example 1 and Example 2.

[0058] <Modification Example 2> In Example 3, an example in which the configuration of the image carrier cleaning means is a cleaning blade was described. However, the shortening of the switching time, which is an effect of the present invention, can also be obtained other than the cleaning blade configuration. For example, a configuration may be adopted in which after the toner image is discharged by the charging roller 102 in contact with the photosensitive drum 101, it is collected by the developing roller 104. This is the same for other examples other than Example 3.

[0059] As described above, according to Example 3, the time required for the switching operation of the rotation speed of the scanner motor accompanied by forced light emission can be further shortened.

Example

[0060] An example in which the present invention is applied to a contact development type monochromatic image forming apparatus that forms a monochromatic image by directly transferring a toner image formed on the photosensitive drum 101 onto a recording material S is shown. As a feature of Example 4, Example 4 performs an operation of suppressing toner development by forced light emission.

[0061] <Description of the Apparatus> The configuration and operation of the image forming apparatus of Example 4 are the same as those of the configuration and the like described with reference to FIG. 9 of Example 3, except that the charging voltage operates at a weak charging voltage as a discharging means for discharging the image carrier. The description of the same points is omitted. As shown in FIG. 9, a charging voltage is applied from a charging voltage source 160, which is a charging voltage applying means, to the charging roller 102, which is a charging means. Further, a developing voltage is applied from a developing voltage source 170, which is a developing voltage applying means, to the developing roller 104, which is a developing means. Note that the developing voltage source 170 can apply voltages of both positive and negative polarities.

[0062] <Operation of Example 4> Using the chart shown in FIG. 12, the process speed switching operation of Example 4 will be described. An example will be used in which, during continuous printing with thick paper followed by plain paper, the rotation speed of the scanner motor 303 with forced light emission is switched without performing the separation operation between the photosensitive drum 101 and the developing roller 104 or stopping the drive motor 120. In the chart shown in FIG. 12, the charging process and the developing process, which were omitted in Examples 1 to 3, are added, and the charging voltage is shown in (iii) and the developing voltage is shown in (iv).

[0063] The start of the process speed switching operation is performed starting from the timing 901 at which the latent image process is completed. First, from the timing 901 when the latent image process ends, the rotation speed of the scanner motor 303 is accelerated from 24803 rpm to 35433 rpm. Forced light emission starts at the timing 902 when the time T901 has elapsed from the timing 901 at which the acceleration starts. The scanner motor 303 reaches the target rotation speed of 35433 rpm at the timing 903 when the time T902 has elapsed from the timing 902 at which the forced light emission starts, and the forced light emission ends. The drive motor 120 starts acceleration (speed switching) to 200 mm / second from the timing 904 when the fixing process for thick paper is completed. From the timing 902 when the forced light emission of the scanner motor 303 starts, the photosensitive drum 101 is irradiated with laser light by the forced light emission.

[0064] The charging voltage is switched from the timing 905 when the charging process is completed to a weak charging voltage (e.g., -500V) below the discharge threshold. As a result, the surface of the photosensitive drum 101 becomes a charge-removal state of approximately 0V. On the other hand, the developing voltage is switched to a voltage (+200V) with a polarity opposite to that during image formation (-300V) at the timing 906 when the developing process is completed. Thereby, toner development from the developing roller 104 to the photosensitive drum 101 is suppressed. By these charging process and developing process, toner adhesion to the photosensitive drum 101 due to forced light emission can be suppressed. For this reason, even if a voltage with a polarity opposite to that during image formation is not applied to the transfer roller 706, background contamination due to toner adhesion is suppressed. Note that the charging voltage and developing voltage applied in Example 4 are examples. The weak charging voltage may be any value that can maintain the charge-removal state, and the developing voltage with the opposite polarity may be any value that can suppress toner development.

[0065] The latent image process for plain paper starts based on the timing 907 when the switching of the speed of the drive motor 120 is completed. The charging voltage is switched to the voltage (-1200V) during image formation in accordance with the timing 908 when the charging process for plain paper is started. In this way, the charging voltage source 160 applies a voltage below the threshold at which discharge occurs between the charging roller 102 and the photosensitive drum 101 during the period from when the charging operation for image formation on thick paper is completed until the charging operation for image formation on plain paper is started.

[0066] The developing voltage is also switched to the voltage (-360V) during image formation in accordance with the timing 909 at the start of the developing process. In this way, the developing voltage source 170 applies a voltage with a polarity opposite to the polarity of the voltage applied during image formation to the developing roller 104 during the period from when the developing operation for image formation on thick paper is completed until the developing operation for image formation on plain paper is started. The switching time Tc in Example 4 is 0.9 seconds. Note that the charging voltage for the charging process of thick paper is -1000V.

[0067] <Effect of Example 4> The effects of Example 4 will be described. The conventional operation to be compared is the same as the conventional operation shown in FIG. 11 of Example 3. The switching time Tc of the conventional operation is 3.2 seconds. Since the switching time Tc in Example 4 is 0.9 seconds, even the operation of Example 4 can achieve a shortening of the switching time.

[0068] By applying Example 4, even when forced light emission is performed, by suppressing toner development on the photosensitive drum 101, the shortening effect of the switching operation, which is the effect of the present invention, can be obtained. As described above, by switching the rotation speed of the scanner motor in a state where the developing means is in contact, the switching time Tc could be shortened from 3.2 seconds to 0.9 seconds. Therefore, even when the basis weight is different and it is necessary to switch the process speed, it is not necessary to stop the drive motor or perform the developing separation / contact operation, and a decrease in productivity can be minimized.

[0069] <Modification 1> In Example 4, the operation of suppressing toner development by forced light emission in a monochromatic image forming apparatus was described as an example. However, the operation of suppressing toner development by forced light emission in a monochromatic image forming apparatus is also applicable to the multicolor image forming apparatuses shown in Example 1 and Example 2.

[0070] <Modification 2> In Example 4, a configuration using a weak charging voltage as the charging means for discharging the image carrier was described as an example. However, the operation of suppressing toner development is not limited to the means of Example 4 and is applicable. For example, a configuration having charging light or a charging brush, or charging using a transfer means may be used. This is the same for other examples other than Example 4.

[0071] As described above, according to Example 4, the time required for the switching operation of the rotation speed of the scanner motor accompanied by forced light emission can be further shortened.

Example

[0072] An example in which the present invention is applied to an image forming apparatus of a contact development method for forming a monochromatic image by directly transferring a toner image formed on a photosensitive drum 101 onto a recording material S is shown. As a feature of Example 5, in the operation where the rotation speed of the scanner motor 303 is switched by switching the resolution, rather than the operation where the rotation speed of the scanner motor 303 is switched by switching the process speed.

[0073] <Description of the apparatus> The configurations of the cartridge 100 and the scanner unit 103 in Example 5 are the same as those in Example 3. As operations, it operates in two modes: a high-quality mode that operates at a resolution of 400 dpi, which is the second resolution, and a normal-quality mode that operates at a resolution of 300 dpi, which is the first resolution. At this time, the rotation speed of the scanner motor 303 is 33070 rpm in the high-quality mode and 24803 rpm in the normal-quality mode. Note that both modes operate at a process speed of 140 mm / second.

[0074] <Operation of Example 5> The resolution switching operation of Example 5 will be described using the chart shown in FIG. 13. When continuously printing with the high-quality mode following the normal-quality mode, an example will be used to describe the operation in which the rotation speed of the scanner motor 303 accompanied by forced light emission is switched without performing the separation operation between the photosensitive drum 101 and the developing roller 104 or the stop of the drive motor 120.

[0075] What is different from the chart of FIG. 10 in Example 3 is that the process speed of the drive motor 120 does not change before and after the switching. In Example 3, after waiting for the completion of the switching of the process speed, the latent image process was started after the switching of the rotation speed of the scanner motor 303 (timing 807). However, even if the process speed does not change, the timing 1001 to start the latent image process after the switching of the rotation speed of the scanner motor 303 needs to wait for the end of the forced light emission. Therefore, the switching time Tc from the timing 1002 when the fixing process before the switching of the rotation speed of the scanner motor 303 ends to the timing 1001 to start the latent image process is limited by the switching of the speed of the scanner motor 303. The switching time Tc in Example 5 is 0.7 seconds.

[0076] <Effect of Example 5> The effect of Example 5 is the shortening of the switching time as in the previous examples. The switching time Tc of the conventional operation for comparison was 3.2 seconds, which is equivalent to the switching time Tc of the conventional operation shown in Example 3. Even in a switching operation where only the rotation speed of the scanner motor 303 is switched without changing the process speed as in the operation of Example 5, the effect of shortening the switching time, which is the effect of the present invention, can be obtained. As described above, by switching the rotation speed of the scanner motor 303 while the developing roller 104 is in contact, the switching time Tc can be shortened from 3.2 seconds to 0.7 seconds. Therefore, even when it is necessary to switch the resolution during continuous printing, it is not necessary to stop the drive motor or perform the developing separation / contact operation, and the reduction in productivity can be minimized.

[0077] As described above, according to Example 5, the time required for the switching operation of the rotation speed of the scanner motor accompanied by forced light emission can be further shortened.

Explanation of Reference Numerals

[0078] 101 Photosensitive drum 104 Developing roller 301 Laser 302 Rotating polygon mirror 303 Scanner motor 305 BD 300 ASIC

Claims

1. Scanning means including a light source, a rotating polygon mirror that deflects the laser light emitted from the light source and is emitted, and first driving means for driving the rotation of the rotating polygon mirror; Control means for controlling the light source and the first driving means; A photoreceptor on which an electrostatic latent image is formed by the laser light emitted from the scanning means; Developing means for developing the electrostatic latent image formed on the photoreceptor with toner to form a toner image; An intermediate transfer member onto which the toner image formed on the photoreceptor is primarily transferred; Primary transfer means for primarily transferring the toner image onto the intermediate transfer member; Secondary transfer means for forming a secondary transfer nip with the intermediate transfer member, and when the toner image primarily transferred onto the intermediate transfer member passes through the secondary transfer nip, secondary transfer means for secondarily transferring the toner image to a recording material; Secondary transfer voltage applying means for applying a voltage to the secondary transfer means; An image forming apparatus comprising: A period during which the first electrostatic latent image is formed while the rotating polygon mirror rotates at a first rotation speed is defined as a first image forming period; A period during which the second electrostatic latent image is formed while the rotating polygon mirror rotates at a second rotation speed different from the first rotation speed is defined as a second image forming period; When a period between the first image forming period and the second image forming period is defined as a non-image forming period, In the non-image forming period, the control means controls the light source to perform a light emission operation in which the laser light is irradiated from the light source to a region including the image forming region of the photoreceptor while the photoreceptor and the developing means are rotating while in contact with each other; And in the non-image forming period, the control means controls the first driving means to perform a switching operation of switching the rotation speed of the rotating polygon mirror from the first rotation speed to the second rotation speed without stopping the rotation of the rotating polygon mirror; When the polarity of the voltage applied to the secondary transfer means by the secondary transfer voltage applying means is the first polarity when the toner image corresponding to the first electrostatic latent image in the first image forming period or the toner image corresponding to the second electrostatic latent image in the second image forming period passes through the secondary transfer nip, When the third electrostatic latent image formed when the light emission operation is performed in the non-image forming period is developed and the toner image corresponding to the third electrostatic latent image is primarily transferred onto the intermediate transfer member, the polarity of the voltage applied to the secondary transfer means by the secondary transfer voltage applying means during the period when the toner image corresponding to the third electrostatic latent image passes through the secondary transfer nip is the second polarity opposite to the first polarity. An image forming apparatus characterized by the above.

2. The image forming apparatus further includes cleaning means for removing toner on the intermediate transfer member, After the toner image on the intermediate transfer member passes through the secondary transfer means, the toner image on the intermediate transfer member is removed and cleaned by the cleaning means. The image forming apparatus according to claim 1, characterized by the above.

3. The photosensitive member is a photosensitive drum, The developing means is a developing roller that contacts the photosensitive drum, The intermediate transfer member is an intermediate transfer belt, The primary transfer means is a primary transfer roller pressed against the photosensitive drum via the intermediate transfer belt, The secondary transfer means is a secondary transfer roller, The cleaning means is a belt cleaning blade for cleaning the intermediate transfer belt. The image forming apparatus according to claim 2, characterized by the above.

4. The image forming apparatus according to any one of claims 1 to 3, characterized in that the photosensitive member and the developing means are in a first state of contact or a second state of separation.

5. Charging means for charging the surface of the photosensitive member, A charging voltage application means for applying a charging voltage to the charging means, A developing voltage application means for applying a developing voltage to the developing means, and comprising The charging voltage application means applies a voltage equal to or lower than a threshold value at which discharge occurs between the charging means and the photoreceptor during a period from when the charging operation by the charging means for performing an image forming operation at the first rotation speed is completed until the charging operation is started after being switched to the second rotation speed. The developing voltage application means applies a voltage having a polarity opposite to the polarity of the voltage applied during image formation to the developing means during a period from when the developing operation by the developing means for performing an image forming operation at the first rotation speed is completed until the developing operation is started after being switched to the second rotation speed. The image forming apparatus according to any one of claims 1 to 4.

6. Further comprising second driving means for driving the photoreceptor and the developing means, The control means further controls the second driving means, and when switching the process speed from the first process speed to a second process speed different from the first process speed by the second driving means during continuous image formation, also performs control to switch from the first rotation speed to the second rotation speed. The image forming apparatus according to any one of claims 1 to 5, characterized in that.

7. The control means switches from the first rotation speed to the second rotation speed when switching the resolution from the first resolution to a second resolution different from the first resolution during continuous image formation. The image forming apparatus according to any one of claims 1 to 6, characterized in that.

8. The basis weight of the first recording material on which the toner image corresponding to the first electrostatic latent image is transferred by the secondary transfer means is defined as the first basis weight, When the basis weight of the second recording material on which the toner image corresponding to the second electrostatic latent image is transferred by the secondary transfer means is defined as the second basis weight, The first basis weight is greater than the second basis weight, and the first recording material and the second recording material are different in type. The image forming apparatus according to any one of claims 1 to 7, characterized in that.

9. The recording material onto which the toner image corresponding to the first electrostatic latent image is transferred by the secondary transfer means is thick paper. The recording material onto which the toner image corresponding to the second electrostatic latent image is transferred by the secondary transfer means is plain paper. The image forming apparatus according to any one of claims 1 to 7, characterized in that.

Images