Image forming device

Abstract

To provide an image forming device with which it is possible to detect the abnormality of torque acting upon a motor when torque acts upon the motor that would cause a torque change to occur within the rated load.SOLUTION: A control unit calculates an average torque per unit time in a section A1. The control unit calculates an average torque per unit time in a section B1 after the voltage application of a primary transfer voltage starts. The control unit calculates an average torque per unit time in a section CX for each sheet of recording medium, every time one sheet of recording medium enters and passes through a secondary transfer unit. The control unit calculates an average torque per unit time in a section B2 after the conveyance of recording media is finished. The control unit calculates an average torque per unit time in a section A2 after the voltage application of the primary transfer power supply stops. When the difference in average torque between the sections A1 and A2, or between the sections B1 and B2, or in the section CX is greater than or equal to a threshold, the control unit outputs error information pertaining to the torque acting upon a belt drive motor.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus using electrophotographic technology, such as a printer, a copying machine, a facsimile machine, or a multifunction machine. [Background technology]

[0002] In order to prevent breakdowns caused by the load torque of a motor, image forming devices stop the motor and notify the user when fluctuations in the motor's rotational speed exceed a certain level and continue for a predetermined period of time, indicating that an overload torque exceeding the rated load is being applied to the motor. To achieve this, a configuration has been proposed in the past that detects the rotational speed of the motor based on an FG (Frequency Generator) signal output from the motor (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-151528 Summary of the Invention [Problem to be solved by the invention]

[0004] The device described in Patent Document 1 above can detect when an excessive torque load is applied, causing the motor's rotation speed to become unstable, but it cannot detect when a torque that causes torque changes within the rated load, which is not enough to cause the motor's rotation speed to become unstable, is applied. Examples of torque changes within the rated load include when a belt cleaning blade that removes toner from the intermediate transfer belt becomes warped, or when the shaft or bearing of the motor that drives the intermediate transfer belt, or the shaft or bearing of the gear in the gear train driven by the motor, becomes worn down during use. If left unchecked, these problems can shorten the life of the intermediate transfer belt or cause motor failure, which is undesirable.

[0005] Therefore, it would be desirable to be able to detect as a torque abnormality when a torque that causes a torque change within the above-mentioned rated load is applied, but because the motor rotation speed in this case is stable, it has not been possible in the past to detect as an abnormality in the torque applied to the motor.

[0006] The present invention has been made in consideration of the above problems, and aims to provide an image forming apparatus that can detect an abnormality in the torque applied to the motor when a torque that causes a torque change within the rated load is applied to the motor. [Means for solving the problem]

[0007] an intermediate transfer member that is in rotatable contact with the photosensitive drum; a drive unit that drives the intermediate transfer member to rotate; a primary transfer unit that is capable of primary transfer of the toner image on the photosensitive drum to the intermediate transfer member by applying a primary transfer voltage; a secondary transfer unit that is in contact with the intermediate transfer member to form a nip portion that can sandwich and transport a recording material and is capable of secondary transfer of the toner image on the intermediate transfer member to the recording material by applying a secondary transfer voltage; a voltage application unit that applies a voltage to the primary transfer unit; a detection unit that detects the torque applied to the drive unit as the intermediate transfer member rotates; and a control unit that is capable of outputting error information regarding the torque applied to the drive unit when, based on the torque detected by the detection unit, a difference between an average torque per unit time from when the drive unit starts to drive in response to the start of an image formation job to when the voltage application unit starts to apply voltage and an average torque per unit time from when the voltage application unit stops applying voltage to when the drive unit stops to drive in response to the end of the image formation job is equal to or greater than a threshold value.

[0008] an intermediate transfer member that is in rotatable contact with the photosensitive drum; a drive unit that drives the intermediate transfer member to rotate; a primary transfer means that is capable of primary transfer of the toner image on the photosensitive drum to the intermediate transfer member by applying a primary transfer voltage; a secondary transfer means that is in contact with the intermediate transfer member to form a nip portion that can sandwich and transport a recording material and is capable of secondary transfer of the toner image on the intermediate transfer member to the recording material by applying a secondary transfer voltage; a voltage application means that applies a voltage to the primary transfer means; a detection means that detects the torque applied to the drive unit as the intermediate transfer member rotates; and a control means that is capable of outputting error information regarding the torque applied to the drive unit when, after the drive unit starts to drive in response to the start of an image forming job, the difference between the average torque per unit time from the start of voltage application by the voltage application means to the time when the first recording material enters the nip portion and the average torque per unit time from the time when the last recording material passes through the nip portion to the time when the voltage application means stops applying voltage is greater than or equal to a threshold value based on the torque detected by the detection means.

[0009] an intermediate transfer member that is rotatably abutting against the photosensitive drum; a drive unit that drives the intermediate transfer member to rotate; a primary transfer means that is capable of primary transfer of the toner image on the photosensitive drum to the intermediate transfer member by applying a primary transfer voltage; a secondary transfer means that is in contact with the intermediate transfer member to form a nip portion that can sandwich and transport a recording material and is capable of secondary transfer of the toner image on the intermediate transfer member to the recording material by applying a secondary transfer voltage; a detection means that detects the torque applied to the drive unit as the intermediate transfer member rotates; and a control means that is capable of outputting error information regarding the torque applied to the drive unit when, based on the torque detected by the detection means, a difference between an average torque per unit time from when a first recording material, among the recording materials that are continuously transported, enters the nip portion until it passes through it and an average torque per unit time from when a second recording material, among the recording materials that are continuously transported, enters the nip portion until it passes through it is greater than or equal to a threshold value after the drive unit starts driving in response to the start of an image forming job.

[0010] An image forming apparatus according to one embodiment of the present invention comprises a photosensitive drum that rotates while carrying a toner image on its surface, a drive unit that drives the photosensitive drum to rotate, a transfer means that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by applying a transfer voltage, a voltage application means that applies a voltage to the transfer means, a detection means that detects the torque applied to the drive unit as the photosensitive drum rotates, and a control means that, based on the torque detected by the detection means, is capable of outputting error information regarding the torque applied to the drive unit when the difference between the average torque per unit time from when the drive unit starts to drive in response to the start of an image forming job to when the voltage application means starts to apply voltage and the average torque per unit time from when the voltage application means stops applying voltage to when the drive unit stops to drive in response to the end of the image forming job is greater than or equal to a threshold value.

[0011] An image forming apparatus according to one embodiment of the present invention comprises a photosensitive drum that rotates while carrying a toner image on its surface, a drive unit that drives the photosensitive drum to rotate, a transfer means that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by applying a transfer voltage, a voltage application means that applies a voltage to the transfer means, a detection means that detects the torque applied to the drive unit as the photosensitive drum rotates, and a control means that, based on the torque detected by the detection means, outputs error information regarding the torque applied to the drive unit when, after the drive unit starts to drive in response to the start of an image forming job, the difference between the average torque per unit time from when the voltage application means starts applying voltage to when the first recording material enters the nip portion and the average torque per unit time from when the last recording material passes through the nip portion to when the voltage application means stops applying voltage is greater than or equal to a threshold value.

[0012] An image forming apparatus according to one embodiment of the present invention comprises a photosensitive drum that rotates while carrying a toner image on its surface, a drive unit that drives the photosensitive drum to rotate, a transfer unit that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by applying a transfer voltage, a voltage application unit that applies a voltage to the transfer unit, a detection unit that detects the torque applied to the drive unit as the photosensitive drum rotates, and a control unit that is capable of outputting error information regarding the torque applied to the drive unit when, based on the torque detected by the detection unit, the difference between the average torque per unit time from when a first recording material, among the recording materials that are continuously transported, enters the nip portion until it passes through it and the average torque per unit time from when a second recording material, among the recording materials that are continuously transported, enters the nip portion until it passes through it is greater than or equal to a threshold value after the drive unit starts driving in response to the start of an image forming job.

[0013] An image forming apparatus according to one embodiment of the present invention includes a photosensitive drum that rotates while carrying a toner image on its surface, an intermediate transfer member that rotatably contacts the photosensitive drum, a drive unit that drives the photosensitive drum to rotate, a primary transfer unit that contacts the photosensitive drum to form a first nip portion and is capable of primary-transferring the toner image on the photosensitive drum to the intermediate transfer member by applying a primary transfer voltage, a secondary transfer unit that contacts the intermediate transfer member to form a second nip portion that is capable of nipping and conveying a recording material and is capable of secondary-transferring the toner image on the intermediate transfer member to the recording material by applying a secondary transfer voltage, and a drive unit that applies a voltage to the primary transfer unit. a detection means for detecting the torque applied to the drive unit as the photosensitive drum rotates; and a control means for outputting error information regarding the torque applied to the drive unit when, based on the torque detected by the detection means, a difference between an average torque per unit time from when the drive unit starts to drive in response to the start of an image forming job to when the voltage application means starts to apply voltage and an average torque per unit time from when the voltage application means stops applying voltage to when the drive unit stops to drive in response to the end of the image forming job is equal to or greater than a threshold value. [Effects of the Invention]

[0014] According to the present invention, when torque that causes a torque change within the rated load is applied to the drive unit, it can be detected as an abnormality in the torque applied to the drive unit. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 4 is a schematic diagram for explaining a drive unit. [Figure 3] FIG. 4 is a block diagram illustrating a control unit. [Figure 4] 6 is a graph showing the change over time in torque applied to a motor when a large torque change exceeding the rated load occurs. [Figure 5] 5 is a graph showing the change over time in the rotation speed of the motor in the case of FIG. 4. [Figure 6] 6 is a graph showing the change over time in torque applied to a motor when torque changes occur within the rated load. [Figure 7] 7 is a graph showing the change over time in the rotation speed of the motor in the case of FIG. 6. [Figure 8] 10 is a flowchart showing an abnormal torque output process. [Figure 9] FIG. 10 is a diagram showing a change in torque over time to explain an abnormal torque output process. [Figure 10] 10 is a flowchart showing a notification process. [Figure 11] FIG. 1 is a schematic diagram showing a direct transfer type image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Image forming device> The present embodiment will be described below. First, an overview of the image forming apparatus of the present embodiment will be described with reference to Figures 1 and 2. As shown in Figure 1, the image forming apparatus 100 is an intermediate transfer type full-color printer in which four color image forming units 600Y, 600M, 600C, and 600K, also called process cartridges, are arranged facing an intermediate transfer belt 61 as an intermediate transfer body.

[0017] Image forming apparatus 100 has image forming units 600Y, 600M, 600C, and 600K that form yellow, magenta, cyan, and black toner images, respectively. Image forming apparatus 100 forms a toner image on recording material S in response to an image signal from a document reading device 41 provided above apparatus main body 100A or an external device (not shown) such as a personal computer. Examples of recording material S include various types of sheet materials such as plain paper, cardboard, rough paper, textured paper, coated paper, plastic film, and cloth.

[0018] The conveyance process of the recording material S in the image forming apparatus 100 will be described. The recording material S is stored in a stacked form in one or more (here, two) cassettes 62 and is supplied one sheet at a time by a supply roller 63 in accordance with the image formation timing. The recording material S supplied by the supply roller 63 is conveyed to a registration roller 65 disposed midway along a conveyance path 64. The registration roller 65 then performs skew correction and timing correction on the recording material S, and the recording material S is sent to a secondary transfer portion T2. The secondary transfer portion T2 is formed so as to be able to nip and convey the recording material S between an inner secondary transfer roller 66 and an outer secondary transfer roller 67 that face each other across the intermediate transfer belt 61. This is a nip portion (second nip portion) that can secondarily transfer a toner image from the intermediate transfer belt 61 onto the recording material S by applying a predetermined pressure and a secondary transfer voltage. In this embodiment, a secondary transfer voltage is applied to the outer secondary transfer roller 67, which serves as a secondary transfer means, by a secondary transfer power source 701 (see FIG. 2).

[0019] The process of forming an image sent to the secondary transfer station T2 at the same timing as the process of conveying the recording material S to the secondary transfer station T2 described above will now be described. First, the image forming stations 600Y to 600K will be described. However, since the image forming stations 600Y to 600K for each color are basically the same except for the color of toner, the following description will be given using the black image forming station 600K as an example. Note that in FIG. 1, only the black image forming station 600K is labeled with a reference number, and the image forming stations 600Y to 600C for the other colors are not labeled with reference numbers.

[0020] The image forming unit 600K is mainly composed of a photosensitive drum 1, a charging device 2, a developing device 3, a drum cleaning blade 5, etc. The surface of the rotating photosensitive drum 1 is uniformly charged in advance by the charging device 2, and then an electrostatic latent image is formed on it by an exposure device 68 driven based on a signal of image information. Next, the electrostatic latent image formed on the photosensitive drum 1 is made visible through toner development by the developing device 3. The developing device 3 develops the electrostatic latent image with toner contained in the developer, forming a toner image on the photosensitive drum 1.

[0021] Thereafter, a predetermined pressure and primary transfer voltage are applied by the primary transfer roller 4, which is disposed opposite the image forming unit 600K with the intermediate transfer belt 61 sandwiched therebetween, and the toner image formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 61. The intermediate transfer belt 61 is rotatably in contact with the photosensitive drum 1. A primary transfer voltage is applied to the primary transfer roller 4, which serves as a primary transfer means, by a primary transfer power supply 700 (see FIG. 2), thereby enabling the toner image on the photosensitive drum 1 to be primarily transferred to the intermediate transfer belt 61. The primary transfer roller 4 presses against the intermediate transfer belt 61 to form a transfer portion T3Y as a first nip portion between the photosensitive drum 1Y and the intermediate transfer belt 61. Note that any primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer is collected by a drum cleaning blade 5 that rubs against the surface of the photosensitive drum 1.

[0022] In this embodiment, there are four sets of image forming units 600Y to 600K: yellow (Y), magenta (M), cyan (C), and black (K). However, the number of colors is not limited to four, and the order of the colors is not limited to this. The developing device 3 uses a two-component developer containing toner and carrier as the developer. In this case, toner is consumed during development, so toner can be replenished to the developing device 3 of each color from toner bottles 605Y, 605M, 605C, and 605K that contain toner. The replenishment developer previously stored in the toner bottles 605Y to 605K is replenished to each developing device 3 (Y, M, C, K) by a toner replenishment device (not shown).

[0023] The intermediate transfer belt 61 onto which the toner image is primarily transferred is an endless belt that is stretched by a tension roller 6, a secondary transfer inner roller 66, and tension rollers 7a and 7b and moves in the direction of arrow D in the figure. The image formation processes for each color, which are processed in parallel by the image forming units 600Y to 600K for each color described above, are performed at a timing that sequentially superimposes the image onto the toner image of the color that was primarily transferred upstream in the movement direction (see arrow R1) onto the intermediate transfer belt 61. As a result, a full-color toner image is finally formed on the intermediate transfer belt 61 and transported to the secondary transfer unit T2.

[0024] Residual toner remaining on the intermediate transfer belt 61 (on the intermediate transfer body) after passing through the secondary transfer portion T2 is removed from the intermediate transfer belt 61 by a belt cleaning blade 8 that rubs against the surface of the intermediate transfer belt 61. The belt cleaning blade 8 is a rubber blade formed into a plate shape from a rubber material such as polyurethane rubber or urethane rubber, and is in contact with the intermediate transfer belt 61 in an elastically deformed state. The primary transfer rollers 4 (Y, M, C, K), intermediate transfer belt 61, tension roller 6, inner secondary transfer roller 66, and tension rollers 7a, 7b are integrally provided as an intermediate transfer belt unit 800.

[0025] Through the conveying process and image forming process described above, the timing of the recording material S and the full-color toner image coincides at the secondary transfer portion T2, and secondary transfer is performed in which the toner image is transferred from the intermediate transfer belt 61 to the recording material S. The recording material S is then conveyed to the fixing device 9, where the toner image is fixed to the recording material S by applying heat and pressure. The fixing device 9 has, for example, a fixing roller heated by a heater, and a pressure roller that contacts the fixing roller and forms a fixing nip portion, and fixes the toner image to the recording material S by applying heat and pressure to the recording material S passing through the fixing nip portion.

[0026] The recording material S that has passed through the fixing device 9 is conveyed to discharge rollers 69, which either discharge it directly onto a discharge tray 601 (single-sided mode) or convey it to a double-sided conveying path 603 for double-sided image formation (double-sided mode). In the double-sided mode, the discharge rollers 69 rotate forward to convey the recording material S until its trailing edge passes a switching member 602, and then the discharge rollers 69 are rotated reversely to switch the leading and trailing edges, and the recording material S is conveyed to the double-sided conveying path 603. Thereafter, the recording material S is sent again to the conveying path 64 by re-supply rollers 604. The subsequent conveyance and the image formation process on the back side are the same as those described above, and therefore a description thereof will be omitted.

[0027] 2, in this embodiment, the inner secondary transfer roller 66, which contacts the intermediate transfer belt 61 from the inner circumferential side and forms the secondary transfer portion T2 together with the outer secondary transfer roller 67, also serves as a belt drive roller that rotates the intermediate transfer belt 61. That is, the inner secondary transfer roller 66 rotates by transmitting a driving force generated by a belt drive motor 801 serving as a drive unit via a drive transmission unit 802 such as a gear. In response to the rotation of the inner secondary transfer roller 66, the intermediate transfer belt 61 rotates in the movement direction (see arrow R1).

[0028] The belt drive motor 801 is provided with a torque sensor 900 as a detection unit that detects the torque applied to the belt drive motor 801 via a drive transmission unit 802 as the inner secondary transfer roller 66 is rotated. As will be described in detail later, in this embodiment, when a load torque that causes a torque change within the rated load is applied to the belt drive motor 801, an abnormality in the torque applied to the belt drive motor 801 can be detected based on the detection result of the torque sensor 900. The photosensitive drums 1Y to 1K are rotated by drum drive motors 810Y to 810K, respectively, via drive transmission units not shown.

[0029] <Control unit> 1, the image forming apparatus 100 includes a control unit 500. The control unit 500 will be described using FIG. 3 with reference to FIGS. 1 and 2. In addition to those shown in FIG. 3, various devices are connected to the control unit 500, such as motors (not shown) that rotate the photosensitive drums 1Y to 1K and a secondary transfer power supply 701. However, since this is not the main focus of the invention, illustration and description of these devices are omitted here.

[0030] The control unit 500, which serves as a control means, controls various operations of the image forming apparatus 100, such as the image forming operation, and includes, for example, a CPU (Central Processing Unit) 501 and a memory 502. The memory 502 is configured with a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and stores various programs and data for controlling the image forming apparatus 100. The CPU 501 can execute image formation jobs stored in the memory 502 and programs such as the "torque abnormality output processing" (see FIG. 8) described below. The memory 502 can also temporarily store the results of calculations and the like that accompany the execution of the various programs.

[0031] The control unit 500 is connected to the operation unit 40, the primary transfer power supply 700, the belt drive motor 801, and the torque sensor 900 via an input / output interface. The operation unit 40 has an input unit 40a and a display unit 40b. The input unit 40a includes various switches and buttons that allow the user to start and stop various programs, such as an image formation job, and to input various data, such as the type and number of sheets of recording material S. The display unit 40b, which serves as a display means, is, for example, a liquid crystal display that can display various screens, such as menu screens that present various programs, input screens that display various data, such as the type and number of sheets of recording material S, and notification screens that notify the user of operational information. The operation unit 40 may be a so-called touch panel, or may be an external device, such as a personal computer, connected to the apparatus main body 100A so as to input and output data.

[0032] The control unit 500 applies a primary transfer voltage to the primary transfer rollers 4Y to 4K by controlling the primary transfer power supply 700 as a voltage application unit. The control unit 500 can timely acquire the torque applied to the belt drive motor 801 detected by the torque sensor 900. The control unit 500 can then calculate the average torque per unit time applied to the belt drive motor 801 based on the detection result of the torque sensor 900. The control unit 500 can also count the number of times an abnormality in the torque applied to the belt drive motor 801 is detected based on the detection result of the torque sensor 900. If the control unit 500 detects an abnormality in the torque, it stops the image formation job being executed, stops driving the belt drive motor 801, and notifies the user of the occurrence of a torque abnormality using the display unit 40b.

[0033] Furthermore, when an image forming job is executed, the control unit 500 can determine the timing at which the recording material S enters the secondary transfer unit T2 and the timing at which the recording material S passes through the secondary transfer unit T2 for each sheet of recording material S in accordance with the exposure start timing at which the exposure device 68 forms an electrostatic latent image on the photosensitive drums 1Y to 1K.

[0034] An image forming job is a series of operations from the start of image formation to the completion of image forming operations based on an image signal for forming an image on a recording material S. That is, it is a series of operations from the start of preparatory operations (so-called pre-rotation) required for image formation, through the image forming process, to the completion of preparatory operations (so-called post-rotation) required for completing image formation. Specifically, it refers to the period from pre-rotation after receiving an image signal (preparatory operations before image formation) to post-rotation (operations after image formation), and includes the image formation period and paper intervals.

[0035] Next, the change over time in torque applied to belt drive motor 801 and the change over time in the rotational speed of belt drive motor 801 due to this change in torque will be described using Figures 4 to 7, along with Figure 2. Figure 4 is a graph showing the change over time (sec) in torque (kgf cm) applied to belt drive motor 801 before and after a large torque change exceeding the rated load occurs. Figure 5 is a graph showing the change over time in rotational speed (rpm) of belt drive motor 801 when a large torque change exceeding the rated load occurs.

[0036] If some abnormality occurs in the drive transmission unit 802, the inner secondary transfer roller 66 (belt drive roller), the intermediate transfer belt 61, or the like, the torque applied to the belt drive motor 801 may suddenly increase and exceed the rated load of the belt drive motor 801, as shown in Fig. 4. In that case, the rotation speed of the belt drive motor 801 drops significantly at the timing when the torque suddenly changes, as shown in Fig. 5. Then, the rotation speed of the belt drive motor 801 subsequently attempts to return to the rotation speed before the torque suddenly changed, but becomes unstable and fluctuates wildly as a reaction to the large drop.

[0037] Conventionally, the control unit 500 acquires the rotation speed of the belt drive motor 801 detected by a rotation sensor (not shown), and detects that a torque abnormality has occurred when the rotation speed exceeds a preset upper limit (Vs1) or falls below a preset lower limit (Vs2). Then, when the control unit 500 detects that a torque abnormality has occurred in the belt drive motor 801, it stops the belt drive motor 801. Thus, conventionally, if the torque change is so great that the rotation speed of the belt drive motor 801 becomes clearly unstable, it can be detected that a torque abnormality has occurred.

[0038] For this reason, in the past, it was not possible to detect the occurrence of a torque abnormality when the torque applied to the belt drive motor 801 changed within the rated load, but not to the extent that it destabilized the rotational speed of the belt drive motor 801. Fig. 6 is a graph showing the time change in torque applied to the belt drive motor 801 before and after a torque change occurred within the rated load. Fig. 7 is a graph showing the time change in the rotational speed of the belt drive motor 801 when a torque change occurred within the rated load.

[0039] As shown in Figure 6, the torque applied to the belt drive motor 801 changes less than in the case of Figure 4 and does not exceed the rated load. When such a torque change occurs within the rated load, as shown in Figure 7, the rotation speed of the belt drive motor 801 decreases at the timing of the torque change, as in the case of Figure 4. Then, after the decrease, the rotation speed of the belt drive motor 801 becomes stable, unlike in Figure 5, and does not exceed the upper limit value (Vs1) or fall below the lower limit value (Vs2). Therefore, when the torque applied to the belt drive motor 801 changes within the rated load, it is not possible to detect the occurrence of a torque abnormality.

[0040] One of the causes of torque variations within the above-mentioned rated load is, for example, curling of the belt cleaning blade 8. The surface friction coefficient of the intermediate transfer belt 61 can vary during manufacturing, and can also change depending on usage conditions and the effects of friction with the recording material S. If the frictional force between the intermediate transfer belt 61 and the belt cleaning blade 8 becomes greater than expected, the belt cleaning blade 8 will buckle and curl up. This will cause the belt cleaning blade 8 to generate a frictional force greater than normal on the intermediate transfer belt 61, increasing the torque applied to the belt drive motor 801. Furthermore, the belt cleaning blade 8 may not be able to sufficiently remove toner from the intermediate transfer belt 61, which could result in poor image quality.

[0041] If the image forming apparatus 100 continues to be used after the belt cleaning blade 8 has turned over, there is a risk that the intermediate transfer belt 61 will break down. If this happens, the broken intermediate transfer belt 61 must be replaced, which requires the service technician to perform the work, which is time-consuming and costly. Furthermore, the user cannot use the image forming apparatus 100 until the belt cleaning blade 8 has been replaced, which is undesirable as it results in downtime for the image forming apparatus 100. Note that examples of torque changes occurring within the above-mentioned rated load include when the shaft or bearing of the belt drive motor 801 is worn down due to use, in addition to when the belt cleaning blade has turned over.

[0042] Therefore, in this embodiment, when a torque change occurs within the rated load of the belt driving motor 801 due to, for example, the turning over of the belt cleaning blade 8, it is possible to detect the occurrence of a torque abnormality. The torque abnormality output process of this embodiment will be described below using FIGS. 8 and 9 with reference to FIGS. 2 and 3. FIG. 8 is a flowchart showing the torque abnormality output process. The torque abnormality output process is executed by the control unit 500 in accordance with the input of an image formation job. FIG. 9 is a diagram showing a change in torque over time to explain the torque abnormality output process. Note that, hereinafter, detection of an abnormality in the torque applied to the belt driving motor 801 will be described.

[0043] 8, the control unit 500 starts driving (turns on) the belt drive motor 801 in response to the start of an image forming job (S1). The control unit 500 starts calculating the average torque per unit time in section A1 shown in FIG. 9 based on the torque applied to the belt drive motor 801 detected by the torque sensor 900 (S2). Then, the control unit 500 starts applying a primary transfer voltage to the primary transfer rollers 4Y-4K from the primary transfer power supply 700 in order to perform primary transfer of the toner images from the photosensitive drums 1Y-1K to the intermediate transfer belt 61 (S3).

[0044] That is, when an image formation job is started, first, in order to rotate the intermediate transfer belt 61, the belt drive motor 801 is driven to rotate the inner secondary transfer roller 66 (belt drive roller). Then, when the primary transfer voltage is applied to the primary transfer rollers 4Y-4K by the primary transfer power supply 700, an electrostatic attraction force acts between the intermediate transfer belt 61 and the photosensitive drums 1Y-1K, and the dynamic friction force between the photosensitive drums 1Y-1K and the intermediate transfer belt 61 increases. As a result, the torque of the belt drive motor 801 that drives the inner secondary transfer roller 66 increases (time Ta1). The control unit 500 calculates the average torque per unit time (e.g., 0.3 sec) in the section A1 from the start of driving the belt drive motor 801 to the start of application of the primary transfer voltage, updating the average torque over time.

[0045] After starting application of the primary transfer voltage, the control unit 500 starts calculating the average torque per unit time in the section B1 shown in Fig. 9 (S4). Then, the control unit 500 determines whether or not conveyance of the recording material S has started (S5), and waits until conveyance of the recording material S starts (No in S5). The control unit 500 calculates the average torque per unit time in the section B1 shown in Fig. 9 from the start of conveyance of the recording material S until the first recording material S enters the secondary transfer portion T2.

[0046] As described above, when the primary transfer voltage is applied to the primary transfer rollers 4Y-4K, the dynamic friction force between the photosensitive drums 1Y-1K and the intermediate transfer belt 61 increases. Thereafter, when the recording material S being conveyed toward the secondary transfer portion T2 enters the secondary transfer portion T2, a torque for conveying the recording material S is applied to the inner secondary transfer roller 66. As a result, the torque of the belt drive motor 801 that drives the inner secondary transfer roller 66 further increases (time Tb1). After the belt drive motor 801 starts to drive as described above, the control unit 500 calculates, while updating the average torque per unit time (e.g., 0.3 seconds) over time, the average torque in the interval B1 from when the primary transfer power supply 700 starts applying the primary transfer voltage to when the first recording material S enters the secondary transfer portion T2.

[0047] Then, each time a sheet of recording material S enters and passes through the secondary transfer portion T2, the control unit 500 calculates the average torque per unit time in the section CX (C1, C2, ...) shown in FIG. 9 for each sheet of recording material S (S6). That is, while the recording material S enters and passes through the secondary transfer portion T2, a torque for conveying the recording material S is constantly applied to the inner secondary transfer roller 66. Therefore, the torque of the belt drive motor 801 that drives the inner secondary transfer roller 66 is maintained at a high level (for example, from time Tb1 to time Tc1). When recording materials S are continuously conveyed, once the first recording material S passes through the secondary transfer portion T2, the torque of the belt drive motor 801 temporarily decreases. Then, as the second recording material S subsequently enters the secondary transfer portion T2, the torque of the belt drive motor 801 increases again, and the torque of the belt drive motor 801 is maintained at a high level until the second recording material S passes through the secondary transfer portion T2. Thereafter, the interval CX is determined according to the number of times X that the recording material S enters the secondary transfer portion T2. In this way, after the belt drive motor 801 starts to be driven as described above, the control portion 500 calculates, for each sheet of continuously conveyed recording material, the average torque per unit time (for example, 0.3 seconds) from when the recording material S enters the secondary transfer portion T2 until it passes through it, while updating the average torque as time passes.

[0048] The control unit 500 determines whether the difference in the average torque in the above-mentioned section CX is equal to or greater than a threshold value (for example, 0.3 to 0.5 kgf cm) (S7). If the difference in the average torque in the section CX is equal to or greater than the threshold value (Yes in S7), the control unit 500 outputs error information related to the torque applied to the belt drive motor 801 and displays this error information related to the torque as a motor torque abnormality display on the display unit 40b (S15). Furthermore, when the control unit 500 outputs the error information, it stops driving the belt drive motor 801 (S16) before stopping driving the belt drive motor 801 in response to the end of the image formation job (see S14).

[0049] Thus, in this embodiment, if the difference between the average torque per unit time from when the first recording material S, which is being continuously conveyed, enters the secondary transfer portion T2 until it passes through, and the average torque per unit time from when the second recording material S, which is being continuously conveyed, enters the secondary transfer portion T2 until it passes through, is greater than or equal to a threshold value, error information regarding the torque applied to the belt drive motor 801 can be output.

[0050] On the other hand, if the difference in the average torque in the section CX is smaller than the threshold value (No in S7), the control unit 500 determines whether or not the conveyance of the recording material S has ended (S8). If the conveyance of the recording material S has not ended (No in S8), the control unit 500 returns to the process of step S6 and performs the processes of steps S6 and S7.

[0051] If the conveyance of the recording material S has ended (Yes in S8), the control unit 500 starts calculating the average torque per unit time in section B2 shown in Fig. 9 (S9). The control unit 500 determines whether the difference between the average torque in section B1 and the average torque in section B2 is equal to or greater than a threshold value (for example, 0.3 to 0.5 kgf cm) (S10).

[0052] If the difference between the average torque in section B1 and the average torque in section B2 is smaller than the threshold value (No in S10), the control unit 500 stops the application of the primary transfer voltage by the primary transfer power supply 700 (S11). The above-mentioned section B2 is from when the last recording material S passes through the secondary transfer portion T2 to when the application of the primary transfer voltage by the primary transfer power supply 700 stops (time Tb2 to Ta2). In other words, section B2 is the section in which the torque of the belt drive motor 801 is maintained in a reduced state compared to when the last recording material S passes through the secondary transfer portion T2 and the recording material S is passing through the secondary transfer portion T2, that is, compared to section CX.

[0053] On the other hand, if the difference between the average torque in section B1 and the average torque in section B2 is equal to or greater than the threshold value (Yes in S10), the control unit 500 outputs error information related to the torque applied to the belt driving motor 801 and displays this error information related to the torque on the display unit 40b (S15). Furthermore, when the control unit 500 outputs the error information, it stops driving the belt driving motor 801 (S16) before stopping driving the belt driving motor 801 in response to the end of the image formation job (see S14).

[0054] Thus, in this embodiment, if the difference between the average torque per unit time from when the primary transfer power supply 700 starts applying voltage until the first recording material S enters the secondary transfer portion T2 and the average torque per unit time from when the last recording material S passes through the secondary transfer portion T2 until the voltage application of the primary transfer power supply 700 stops is equal to or greater than a threshold value, error information related to the torque applied to the belt drive motor 801 can be output. Note that the "first" recording material S and the "last" recording material S referred to here refer to the single recording material S when an image is formed on that single recording material S.

[0055] After stopping the voltage application of the primary transfer power supply 700 (S11), the control unit 500 starts calculating the average torque per unit time in the section A2 shown in Fig. 9 (S12). The control unit 500 determines whether the difference between the average torque in the section A1 and the average torque in the section A2 is equal to or greater than a threshold value (for example, 0.3 to 0.5 kgf cm) (S13).

[0056] If the difference between the average torque in section A1 and the average torque in section A2 is smaller than the threshold value (No in S13), the control unit 500 stops (turns off) the driving of the belt drive motor 801 in response to the end of the image formation job (S14). The above-mentioned section A2 is from the time when the application of the primary transfer voltage by the primary transfer power supply 700 is stopped to the time when the driving of the belt drive motor 801 is stopped in response to the end of the image formation job (after time Ta2). In other words, in section A2, the torque of the belt drive motor 801 is maintained in a reduced state compared to section B2 due to a decrease in the dynamic friction force between the photosensitive drums 1Y-1K and the intermediate transfer belt 61 in response to the stop of the voltage application from the primary transfer power supply 700.

[0057] On the other hand, if the difference between the average torque in section A1 and the average torque in section A2 is equal to or greater than the threshold value (Yes in S13), the control unit 500 outputs error information related to the torque applied to the belt driving motor 801 and displays this error information related to the torque on the display unit 40b (S15).Furthermore, when the control unit 500 outputs the error information, it stops driving the belt driving motor 801 (S16) before stopping driving the belt driving motor 801 in response to the end of the image forming job (see S14).

[0058] Thus, in this embodiment, if the difference between the average torque per unit time from when the belt drive motor 801 starts to drive in response to the start of an image formation job to when the primary transfer power supply 700 starts to apply voltage, and the average torque per unit time from when the primary transfer power supply 700 stops applying voltage to when the belt drive motor 801 stops to drive in response to the end of an image formation job, is greater than or equal to a threshold value, error information regarding the torque applied to the belt drive motor 801 can be output.

[0059] For example, when there is no curling of the belt cleaning blade 8, the average torque Tqa1 in section A1 and the average torque Tqa2 in section A2 are approximately equal in value. This is because both sections A1 and A2 are in the same state, with no recording material S at the secondary transfer portion T2 and no voltage being applied by the primary transfer power supply 700. Furthermore, the average torque Tqb1 in section B1 and the average torque Tqb2 in section B2 are approximately equal in value, and the average torque TqcX in section CX are approximately equal in value.

[0060] For example, suppose that the belt cleaning blade 8 is curled up in section B2. In that case, the average torque Tqb2 in section B2 is greater than the average torque Tqb1 in section B1. Therefore, as described above, the control unit 500 compares the average torque Tqb2 in section B2 with the average torque in section B1, and if the difference between the two is equal to or greater than a preset threshold, it can detect that a torque abnormality has occurred in the belt drive motor 801. The same applies to sections A1, A2, and CX.

[0061] For example, if the belt cleaning blade 8 is turned over in section A1, the average torque will be higher than normal in both sections A1 and A2. Therefore, it is not possible to detect a torque abnormality in the belt driving motor 801 from the difference between the two alone. In this case, it may be possible to detect a torque abnormality in the belt driving motor 801 from the difference between the average torque in section A1 during a previous image formation job executed before the current image formation job and the average torque in section A1 during the current image formation job. The same applies to sections B1 and C1.

[0062] As described above, the control unit 500 may be configured to immediately stop driving the belt drive motor 801 when it detects that a torque abnormality has occurred in the belt drive motor 801. This makes it possible to prevent breakdowns in the device. Furthermore, since the driving time of the belt drive motor 801 can be shortened when a torque abnormality has occurred, it is possible to minimize the stress on the drive transmission unit 802. In this way, it is possible to prevent a reduction in the lifespan of the belt drive motor 801, the drive transmission unit 802, etc.

[0063] When a torque abnormality occurs in the belt drive motor 801, it is also possible to simply display error information related to the torque on the display unit 40b without stopping the drive of the belt drive motor 801. When the error information related to the torque is displayed on the display unit 40b, it is also possible to display a message urging the user to have a maintenance performed by a service technician, such as replacing the belt cleaning blade 8.

[0064] As described above, in this embodiment, when, for example, the belt cleaning blade 8 is turned over and torque that causes a torque change within the rated load that does not cause the rotation speed to become unstable is applied to the belt drive motor 801, error information related to torque is output. By stopping the driving of the belt drive motor 801 in response to the output of error information related to torque, it is possible to prevent breakdowns and shortening of the lifespan of the belt drive motor 801, etc. Furthermore, by notifying the user in response to the output of error information related to torque, it is possible to reduce the time required for maintenance by a service technician, thereby reducing downtime of the image forming apparatus.

[0065] [Other embodiments] Incidentally, if a torque abnormality is detected in the belt drive motor 801, the user can follow the instructions on the display unit 40b to have a service technician replace the belt cleaning blade 8, etc. On the other hand, since the belt drive motor 801 and the drive transmission unit 802 are more expensive than the belt cleaning blade 8, it is preferable to replace them as infrequently as possible. However, if a torque abnormality occurs in the belt drive motor 801, stress due to the torque abnormality may accumulate, which may lead to a breakdown of the belt drive motor 801 or the drive transmission unit 802. To prevent this, it is preferable to count the number of times that a torque abnormality occurring in the belt drive motor 801 is detected, and to notify the user to replace the belt drive motor 801 or the drive transmission unit 802 before a breakdown occurs based on the cumulative number of times counted.

[0066] The notification process that notifies the user of the need to replace the belt drive motor 801 or the drive transmission unit 802 before a failure occurs will be described below using Fig. 10 with reference to Figs. 2 and 3. Fig. 10 is a flowchart showing the notification process. The notification process shown here is executed by the control unit 500 simultaneously with the torque abnormality detection process (see Fig. 8) described above.

[0067] 10, the control unit 500 determines whether or not a torque abnormality has been detected in response to the output of error information related to the torque applied to the belt drive motor 801 by the torque abnormality detection process (see FIG. 8) described above (S21). If a torque abnormality has not been detected, that is, if error information has not been output (No in S21), the control unit 500 returns to the process of step S21. If a torque abnormality has been detected, that is, if error information has been output (Yes in S21), the control unit 500 counts the number of detections and stores the count in the memory 502 (S22).

[0068] Then, the control unit 500 determines whether the counted number of detections exceeds a predetermined number (S23). If the counted number of detections does not exceed the predetermined number (No in S23), the control unit 500 returns to the processing of step S21. On the other hand, if the counted number of detections exceeds the predetermined number (Yes in S23), the control unit 500 displays on the display unit 40b a message urging the user to replace the belt drive motor 801 or the drive transmission unit 802 (S24).

[0069] In this way, the number of times that a torque abnormality is detected is counted based on the output of error information related to the torque applied to the belt drive motor 801, and based on the counted number, the user is prompted to replace the belt drive motor 801 or the drive transmission unit 802. This reduces the frequency of replacement of the belt drive motor 801 or the drive transmission unit 802 as much as possible, allowing them to be replaced before they break down, thereby reducing the downtime of the image forming apparatus.

[0070] In the above-described embodiment, an intermediate transfer type image forming apparatus has been described as an example of the image forming apparatus 100, but the present invention is not limited to this. The above-described embodiment can also be applied to a direct transfer type image forming apparatus in which a toner image is directly transferred from photosensitive drums 1Y to 1K onto a recording material conveyed by a conveyor belt. This will be described below with reference to FIG. 11. FIG. 11 is a schematic diagram showing a direct transfer type image forming apparatus.

[0071] The image forming apparatus shown in FIG. 11 is a direct transfer type full-color printer in which image forming stations PY, PM, PC, and PK are arranged along a conveyor belt 24. In image forming station PY, a yellow toner image is formed on photosensitive drum 1Y and transferred to recording material S conveyed by conveyor belt 24. In image forming station PM, a magenta toner image is formed on photosensitive drum 1M and transferred to recording material S conveyed by conveyor belt 24. In image forming stations PC and PK, a cyan toner image and a black toner image are formed on photosensitive drums 1C and 1K, respectively, and transferred to recording material S conveyed by conveyor belt 24. The recording material S with the transferred toner images is separated from conveyor belt 24 by curvature and sent to fixing device 9. The fixing device 9 applies heat and pressure to the recording material S, thereby fixing the toner image.

[0072] The image forming units PY, PM, PC, and PK have the same configuration except that the colors of toner used in the developing devices 3Y, 3M, 3C, and 3K are yellow, magenta, cyan, and black, respectively. Therefore, the image forming unit PY will be described below as a representative.

[0073] The image forming unit PY includes a photosensitive drum 1Y surrounded by a primary charger 21Y, an exposure device 68Y, a developing device 3Y, a transfer charger 45Y, and a drum cleaning blade 5Y. The photosensitive drum 1Y is rotated by a drum drive motor 810Y serving as a drive unit. The drum drive motor 810Y is provided with a torque sensor 900Y serving as a detection unit for detecting the torque applied to the drum drive motor 810Y.

[0074] The primary charger 21Y charges the photosensitive drum 1Y by irradiating it with charged particles, for example, due to corona discharge. The exposure device 68Y forms an electrostatic latent image on the charged surface of the photosensitive drum 1Y. The developing device 3Y develops the electrostatic latent image on the photosensitive drum 1Y into a toner image. The transfer charger 45Y, which serves as a transfer means, has a transfer blade that is pressed against the conveyor belt 24 to form a transfer portion T3Y as a nip between the photosensitive drum 1Y and the conveyor belt 24Y. A transfer voltage is applied to the transfer blade by a transfer power source 700Y, which serves as a voltage application means, so that the toner image carried on the photosensitive drum 1Y is transferred to the recording material S on the conveyor belt 24Y. Any residual toner remaining on the photosensitive drum 1Y (on the photosensitive drum) after transfer is removed by a drum cleaning blade 5Y.

[0075] The torque abnormality detection process (see FIG. 8) described above can also be applied to such a direct transfer type image forming apparatus. However, in the case of a direct transfer type image forming apparatus, the control unit 500 outputs error information related to the torque applied to each of the drum drive motors 810Y to 810K, and displays this torque error information as a motor torque abnormality display on the display unit 40b (S15 in FIG. 8). At that time, if the difference between the average torques in the above-mentioned sections A1 and A2, the difference between the average torques in the sections B1 and B2, and the difference between the average torques in the section CX are equal to or greater than predetermined thresholds, it is detected that a torque abnormality has occurred in the drum drive motors 810Y to 810K.

[0076] Furthermore, in the above-described image forming apparatus of the intermediate transfer type, similarly to the above-described image forming apparatus of the direct transfer type, it may be possible to detect torque abnormalities in the drum drive motors 810Y to 810K (see FIG. 2) that drive the photosensitive drums 1Y to 1K. In this case, although not shown in FIG. 2, torque sensors 900Y to 900K (see FIG. 11) that detect torques acting on the drum drive motors 810Y to 810K are provided on the drum drive motors 810Y to 810K, respectively.

[0077] In the above-described embodiment, the control unit 500 and the torque sensor 900 are provided separately, and the control unit 500 acquires the torque applied to the belt drive motor 801 detected by the torque sensor 900 (see FIG. 3 ). However, this is not limiting. For example, the control unit 500 may regard the voltage itself supplied to the belt drive motor 801 to drive the belt drive motor 801 at a constant rotational speed as data corresponding to the torque applied to the belt drive motor 801. That is, as the torque applied to the belt drive motor 801 increases, the rotational speed of the belt drive motor 801 (more specifically, the FG (Frequency Generator) signal output from the motor) decreases. In this case, the control unit 500 controls the voltage supplied to the belt drive motor 801 to increase in order to maintain the rotational speed constant (target speed). In this way, the voltage supplied to the belt drive motor 801 changes depending on the magnitude of the torque applied to the belt drive motor 801. Therefore, the control unit 500 may process the voltage supplied to the belt drive motor 801 as data corresponding to the torque applied to the belt drive motor 801. In other words, the control unit 500 functions as a torque sensor that detects the torque applied to the belt drive motor 801 . [Explanation of symbols]

[0078] 1Y (1M, 1C, 1K)...photosensitive drum, 4Y (4M, 4C, 4K)...primary transfer means (primary transfer roller), 5...drum cleaning blade, 8...belt cleaning blade, 40b...display means (display unit), 45Y (45M, 45C, 45K)...transfer means (transfer charger), 61...intermediate transfer body (intermediate transfer belt), 67...secondary transfer means (secondary transfer outer roller), 100...image forming apparatus, 500...control means (control unit), 700 (700Y, 700M, 700C, 700K)...Voltage application means (primary transfer power supply), 801...Drive unit (belt drive motor), 810Y (810M, 810C, 810K)...Drive unit (drum drive motor), 900 (900Y, 900M, 900C, 900K)...Detection means (torque sensor), T3Y (T3M, T3C, T3K)...Nip portion (first nip portion, transfer portion), T2...Nip portion (second nip portion, secondary transfer portion), S...Recording material

Claims

1. a photosensitive drum that rotates and carries a toner image on its surface; an intermediate transfer member rotatably contacting the photosensitive drum; a drive unit that rotates and drives the intermediate transfer body; a primary transfer means capable of primarily transferring the toner image on the photosensitive drum to the intermediate transfer body by applying a primary transfer voltage; a secondary transfer means for contacting the intermediate transfer body to form a nip portion capable of sandwiching and conveying a recording material, and for secondarily transferring the toner image on the intermediate transfer body to the recording material by applying a secondary transfer voltage; a voltage applying means for applying a voltage to the primary transfer means; a detection unit for detecting a torque applied to the drive unit in accordance with the rotation of the intermediate transfer body; and a control means capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when the drive unit starts to drive in response to the start of an image forming job to when the voltage application means starts to apply voltage and an average torque per unit time from when the voltage application means stops applying voltage to when the drive unit stops to when the image forming job ends is equal to or greater than a threshold value, based on the torque detected by the detection means. An image forming apparatus characterized by:

2. the control means is capable of outputting error information relating to the torque applied to the drive unit when, after the drive unit starts to drive, a difference between an average torque per unit time from when the voltage application means starts to apply voltage until the first recording material enters the nip portion and an average torque per unit time from when the last recording material passes through the nip portion until the voltage application means stops applying voltage is equal to or greater than a threshold value.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. the control means is capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through after the drive unit starts driving and an average torque per unit time from when a second recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through is equal to or greater than a threshold value.

3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. a photosensitive drum that rotates and carries a toner image on its surface; an intermediate transfer member rotatably contacting the photosensitive drum; a drive unit that rotates and drives the intermediate transfer body; a primary transfer means capable of primarily transferring the toner image on the photosensitive drum to the intermediate transfer body by applying a primary transfer voltage; a secondary transfer means for contacting the intermediate transfer body to form a nip portion capable of sandwiching and conveying a recording material, and for secondarily transferring the toner image on the intermediate transfer body to the recording material by applying a secondary transfer voltage; a voltage applying means for applying a voltage to the primary transfer means; a detection unit for detecting a torque applied to the drive unit in accordance with the rotation of the intermediate transfer body; and a control means capable of outputting error information relating to the torque applied to the drive unit when, after the drive unit starts to drive in response to the start of an image forming job, a difference between an average torque per unit time from when the voltage application means starts to apply voltage until the first recording material enters the nip portion and an average torque per unit time from when the last recording material passes through the nip portion until the voltage application means stops applying voltage is equal to or greater than a threshold value, based on the torque detected by the detection means. An image forming apparatus characterized by:

5. the control means is capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through after the drive unit starts driving and an average torque per unit time from when a second recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through is equal to or greater than a threshold value.

5. The image forming apparatus according to claim 4.

6. a photosensitive drum that rotates and carries a toner image on its surface; an intermediate transfer member rotatably contacting the photosensitive drum; a drive unit that rotates and drives the intermediate transfer body; a primary transfer means capable of primarily transferring the toner image on the photosensitive drum to the intermediate transfer body by applying a primary transfer voltage; a secondary transfer means for contacting the intermediate transfer body to form a nip portion capable of sandwiching and conveying a recording material, and for secondarily transferring the toner image on the intermediate transfer body to the recording material by applying a secondary transfer voltage; a detection unit for detecting a torque applied to the drive unit in accordance with the rotation of the intermediate transfer body; and a control means capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the continuously conveyed recording materials, enters the nip portion until it passes through after the drive unit starts to drive in response to the start of an image forming job and an average torque per unit time from when a second recording material, among the continuously conveyed recording materials, enters the nip portion until it passes through is equal to or greater than a threshold value based on the torque detected by the detection means. An image forming apparatus characterized by:

7. A display means is provided, The control means displays the error information on the display means.

7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. the control means counts the number of times the error information is output, and when the counted number exceeds a predetermined number, displays the error information on the display means.

8. The image forming apparatus according to claim 7,

9. When the error information is output, the control unit stops the driving unit before the driving of the driving unit is stopped in response to the end of the image forming job.

8. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

10. a belt cleaning blade that comes into contact with the intermediate transfer body and removes toner from the intermediate transfer body; 10. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

11. a photosensitive drum that rotates and carries a toner image on its surface; a drive unit that drives the photosensitive drum to rotate; a transfer means that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by application of a transfer voltage; a voltage applying means for applying a voltage to the transfer means; a detection means for detecting a torque applied to the driving unit in accordance with the rotation of the photosensitive drum; and a control means capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when the drive unit starts to drive in response to the start of an image forming job to when the voltage application means starts to apply voltage and an average torque per unit time from when the voltage application means stops applying voltage to when the drive unit stops to when the image forming job ends is equal to or greater than a threshold value, based on the torque detected by the detection means. An image forming apparatus characterized by:

12. the control means is capable of outputting error information relating to the torque applied to the drive unit when, after the drive unit starts to drive, a difference between an average torque per unit time from when the voltage application means starts to apply voltage until the first recording material enters the nip portion and an average torque per unit time from when the last recording material passes through the nip portion until the voltage application means stops applying voltage is equal to or greater than a threshold value.

12. The image forming apparatus according to claim 11.

13. the control means is capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through after the drive unit starts driving and an average torque per unit time from when a second recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through is equal to or greater than a threshold value.

13. The image forming apparatus according to claim 11 or 12.

14. a photosensitive drum that rotates and carries a toner image on its surface; a drive unit that drives the photosensitive drum to rotate; a transfer means that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by application of a transfer voltage; a voltage applying means for applying a voltage to the transfer means; a detection means for detecting a torque applied to the driving unit in accordance with the rotation of the photosensitive drum; and a control means capable of outputting error information relating to the torque applied to the drive unit when, after the drive unit starts to drive in response to the start of an image forming job, a difference between an average torque per unit time from when the voltage application means starts to apply voltage until the first recording material enters the nip portion and an average torque per unit time from when the last recording material passes through the nip portion until the voltage application means stops applying voltage is equal to or greater than a threshold value, based on the torque detected by the detection means. An image forming apparatus characterized by:

15. the control means is capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through after the drive unit starts driving and an average torque per unit time from when a second recording material, among the recording materials being continuously conveyed, enters the nip portion until it passes through is equal to or greater than a threshold value.

15. The image forming apparatus according to claim 14.

16. a photosensitive drum that rotates and carries a toner image on its surface; a drive unit that drives the photosensitive drum to rotate; a transfer means that contacts the photosensitive drum to form a nip portion and is capable of transferring the toner image on the photosensitive drum to a recording material by application of a transfer voltage; a voltage applying means for applying a voltage to the transfer means; a detection means for detecting a torque applied to the driving unit in accordance with the rotation of the photosensitive drum; and a control means capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when a first recording material, among the continuously conveyed recording materials, enters the nip portion until it passes through after the drive unit starts to drive in response to the start of an image forming job and an average torque per unit time from when a second recording material, among the continuously conveyed recording materials, enters the nip portion until it passes through is equal to or greater than a threshold value based on the torque detected by the detection means. An image forming apparatus characterized by:

17. A display means is provided, The control means displays the error information on the display means.

17. The image forming apparatus according to claim 11, wherein the image forming apparatus is a recording medium.

18. the control means counts the number of times the error information is output, and when the counted number exceeds a predetermined number, displays the error information on the display means.

18. The image forming apparatus according to claim 17.

19. When the error information is output, the control unit stops the driving unit before the driving of the driving unit is stopped in response to the end of the image forming job.

18. The image forming apparatus according to claim 11, wherein the image forming apparatus is a recording medium.

20. a drum cleaning blade that comes into contact with the photosensitive drum to remove toner from the photosensitive drum; 20. The image forming apparatus according to claim 12, wherein the image forming apparatus is a recording medium.

21. a photosensitive drum that rotates and carries a toner image on its surface; an intermediate transfer member rotatably contacting the photosensitive drum; a drive unit that drives the photosensitive drum to rotate; a primary transfer means that contacts the photosensitive drum to form a first nip portion and is capable of primarily transferring the toner image on the photosensitive drum to the intermediate transfer body by application of a primary transfer voltage; a secondary transfer means for contacting the intermediate transfer body to form a second nip portion capable of nipping and conveying a recording material, and for secondarily transferring the toner image on the intermediate transfer body to the recording material by applying a secondary transfer voltage; a voltage applying means for applying a voltage to the primary transfer means; a detection means for detecting a torque applied to the driving unit in accordance with the rotation of the photosensitive drum; and a control means capable of outputting error information relating to the torque applied to the drive unit when a difference between an average torque per unit time from when the drive unit starts to drive in response to the start of an image forming job to when the voltage application means starts to apply voltage and an average torque per unit time from when the voltage application means stops applying voltage to when the drive unit stops to when the image forming job ends is equal to or greater than a threshold value, based on the torque detected by the detection means. An image forming apparatus characterized by:

22. the control means is capable of outputting error information relating to the torque applied to the drive unit when, after the drive unit starts to drive, a difference between an average torque per unit time from when the voltage application means starts to apply voltage until the first recording material enters the second nip portion and an average torque per unit time from when the last recording material passes through the second nip portion until the voltage application means stops applying voltage is equal to or greater than a threshold value.

22. The image forming apparatus according to claim 21.

Images