Image forming device

Abstract

The present invention comprises: a control unit (301) that rotates, with the axis of rotation being a support part (36), a rotating substrate (30) provided with a resist roller pair (191) that feeds recording paper (P) to an image forming unit (12), and that tilts roller shafts (192A, 192B) of the resist roller pair (191) to the upstream side or downstream side with respect to a conveyance direction D, thereby correcting the tilt of the recording paper (P); and another control unit (201) that corrects the rotation speed of the resist roller pair (191) on the basis of the direction and amount of tilting of the roller shafts (192A, 192B).

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus having a function for correcting the skew of recording paper. [Background technology]

[0002] 2. Description of the Related Art Generally, image forming apparatuses such as copiers or multifunction machines are known that include an image forming unit that forms an image on recording paper, and registration rollers that clamp the recording paper and adjust the timing of supplying it to the image forming unit.

[0003] In such an image forming apparatus, the recording paper may be transported in a state inclined with respect to a predetermined recording paper transport direction. When the recording paper is transported to the image forming unit in a tilted state, a tilted image is formed on the recording paper.

[0004] A technique is known that uses a registration roller to correct the skew of a recording paper. For example, the rotation of the registration roller is stopped once, and after the leading edge of the recording paper hits the stopped registration roller, the rotation of the registration roller is resumed at an appropriate timing. When the recording paper hits the stopped registration roller, a bend is formed in the recording paper, and as a result, the skew of the recording paper is corrected.

[0005] However, when the recording paper hits the stopped registration rollers, an impact noise is generated, which is a problem.

[0006] In order to solve such problems, for example, Patent Documents 1 to 3 disclose techniques for correcting the skew of the recording paper without stopping the rotation of the registration roller. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-075802 A [Patent Document 2] JP 2020-007092 A [Patent Document 3] JP 2020-050493 A Summary of the Invention

[0008] Patent Document 2 discloses a technique for detecting the inclination of a recording paper relative to a predetermined transport direction of the recording paper and correcting the inclination of the recording paper by inclining the roller axis of a registration roller in accordance with the inclination of the recording paper.

[0009] However, tilting the roller shaft of the registration roller affects the timing at which the recording paper reaches the registration roller. Specifically, tilting one end of the roller shaft of the registration roller toward the upstream side in the transport direction shortens the distance between the registration roller and the recording paper, and the recording paper reaches the registration roller earlier. On the other hand, tilting one end of the roller shaft of the registration roller toward the downstream side in the transport direction lengthens the distance between the registration roller and the recording paper, and the recording paper reaches the registration roller later.

[0010] If the timing at which the recording paper reaches the registration rollers changes, this affects the timing at which the recording paper is supplied to the image forming section, which in turn affects the formation of an image on the recording paper.

[0011] The present invention has been made in consideration of the above circumstances, and has an object to make it possible to correct the skew of the recording paper while ensuring that the recording paper is supplied to an image forming unit at an appropriate timing.

[0012] According to one aspect of the present invention, an image forming apparatus includes an image forming unit that forms an image on a recording sheet, a registration roller that is provided upstream of the image forming unit in a predetermined recording sheet transport direction and sends the recording sheet to the image forming unit, a first control unit that controls the rotation of the registration roller, a tilt detection sensor that detects the tilt of the recording sheet relative to the transport direction, a tilt mechanism that tilts the roller shaft of the registration roller, the initial state of which is perpendicular to the transport direction, upstream or downstream relative to the transport direction, and a second control unit that controls the tilt mechanism to tilt the roller shaft upstream or downstream relative to the transport direction based on the detection result of the tilt detection sensor, and to return the tilted roller shaft to its initial state when the recording sheet reaches the registration roller. The second control unit transmits tilt data indicating the direction and amount of tilt of the roller shaft to the first control unit. The first control unit corrects the rotation speed of the registration roller based on the direction and amount of tilt of the roller shaft indicated by the tilt data received from the second control unit. Effect of the Invention

[0013] According to the present invention, the roller shaft of the registration roller is tilted according to the tilt of the recording paper, and when the recording paper reaches the registration roller, the tilted roller shaft is returned to its initial state, so that the tilt of the recording paper can be corrected. Also, the rotation speed of the registration roller is corrected based on the direction and amount of tilt of the roller shaft, so that even if the roller shaft is tilted, the recording paper can be supplied to the image forming unit at the appropriate timing for image formation. This makes it possible to correct the tilt of the recording paper while ensuring that the recording paper is supplied to the image forming unit at the appropriate timing. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic partial front view showing a structure of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 3 is a side view showing a schematic view of a pair of registration rollers and a peripheral area of ​​the pair of registration rollers. FIG. [Diagram 3] 11A and 11B are diagrams illustrating an example of a tilting operation of the pair of registration rollers. [Figure 4] 13A and 13B are diagrams for explaining another example of the tilting operation of the pair of registration rollers. [Diagram 5] 1 is a functional block diagram illustrating a schematic internal configuration of an image forming apparatus. [Figure 6] 10 is a flowchart showing an example of a first roller shaft inclination process. [Figure 7] 6 is a flowchart showing an example of a first rotation speed adjustment process. [Figure 8] 13 is a flowchart showing an example of a second roller shaft inclination process. [Figure 9] 10 is a flowchart showing an example of a second rotation speed adjustment process. [Figure 10] 13 is a flowchart showing an example of a third roller shaft inclination process. [Figure 11] 13 is a flowchart showing an example of a third rotation speed adjustment process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (First embodiment) An image forming apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic partial front view showing the structure of the image forming apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 is a multifunction machine having multiple functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an image forming section 12, a fixing section 13, a paper feed section 14, and a conveying section 19.

[0016] The image forming section 12 includes an intermediate transfer unit 120, photoconductor drums 121 for black, magenta, cyan, and yellow, and a secondary transfer roller 210. The intermediate transfer unit 120 includes an intermediate transfer belt 125 on whose outer circumferential surface a toner image is transferred, a drive roller 125A, a driven roller 125B, and a primary transfer roller 126.

[0017] The intermediate transfer belt 125 is stretched between a drive roller 125A and a driven roller 125B. The intermediate transfer belt 125 is driven by the drive roller 125A while in contact with the circumferential surface of the photosensitive drum 121, and thus travels endlessly in synchronization with the photosensitive drum 121.

[0018] The toner images of each color (black, magenta, cyan, and yellow) transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 at adjusted transfer timings, thereby forming a color toner image.

[0019] Secondary transfer roller 210 forms a nip portion N1 between itself and driving roller 125A, sandwiching intermediate transfer belt 125. Secondary transfer roller 210 transfers, at nip portion N1, the color toner image formed on the surface of intermediate transfer belt 125 onto recording paper P transported from paper feed unit 14 via transport path 190. Recording paper P to which the toner image has been transferred at nip portion N1 is transported to fixing unit 13.

[0020] The conveying section 19 includes a conveying path 190, a pair of registration rollers 191 provided along the conveying path 190 upstream of the nip portion N1 (i.e., the image forming position where an image is formed in the image forming section 12) in the conveying direction D of the recording paper P, a tilt detection sensor 193 provided along the conveying path 190 upstream of the pair of registration rollers 191 in the conveying direction D, a pair of intermediate conveying rollers 194 provided along the conveying path 190 between the pair of registration rollers 191 and the paper feeding section 14, a registration sensor 195 provided along the conveying path 190 near the pair of registration rollers 191, and an intermediate sensor 196 provided along the conveying path 190 near the pair of intermediate conveying rollers 194.

[0021] The pair of registration rollers 191 includes a driving registration roller 191A and a driven registration roller 191B that rotates following the driving registration roller 191A. The driving registration roller 191A and the driven registration roller 191B form a nip portion N2. The pair of registration rollers 191 feeds the recording paper P to the image forming unit 12. The pair of registration rollers 191 adjusts the timing of transporting the recording paper P to the nip portion N1.

[0022] The skew detection sensor 193 detects the skew of the recording paper P with respect to the transport direction D. In this embodiment, the skew detection sensor 193 is a CIS (Contact Image Sensor), which is a type of line sensor. The skew detection sensor 193 detects image data on one side of the recording paper P. The skew detection sensors 193 are arranged in a row in a direction perpendicular to the transport direction D.

[0023] The intermediate transport roller pair 194 transports the recording paper P toward the registration roller pair 191 .

[0024] The registration sensor 195 detects that the leading edge of the recording paper P has reached the registration roller pair 191. The intermediate sensor 196 detects that the leading edge of the recording paper P has reached the intermediate transport roller pair 194. The registration sensor 195 and the intermediate sensor 196 are, for example, known reflective photoelectric sensors equipped with a light-emitting element and a light-receiving element that detects the reflected light of the light emitted from the light-emitting element on the recording paper P, and detect the leading edge of the recording paper P.

[0025] The paper feed unit 14 includes a plurality of paper feed cassettes 141. Each of the paper feed cassettes 141 includes a pickup roller 142, a feed roller 143, a retard roller 144 disposed opposite the feed roller 143, and a transport roller pair 145.

[0026] The pickup roller 142 picks up the recording paper P stored in the paper feed cassette 141. The feed roller 143 and the retard roller 144 separate the recording paper P picked up by the pickup roller 142 one sheet at a time and transport the separated sheets toward the transport roller pair 145.

[0027] FIG. 2 is a side view showing the pair of registration rollers 191 and the peripheral portion of the pair of registration rollers 191. As shown in FIG. 1, the pair of registration rollers 191 includes a driving registration roller 191A and a driven registration roller 191B. The driving registration roller 191A and the driven registration roller 191B each include roller shafts 192A and 192B (hereinafter, sometimes simply referred to as "roller shaft 192"). In FIG. 2, the roller shaft 192A is located directly behind the roller shaft 192B in the depth direction of FIG. 2. The driving registration roller 191A is also located directly behind the driven registration roller 191B in the depth direction of FIG. 2. The driving registration roller 191A, the driven registration roller 191B, and the roller shafts 192A and 192B are provided on the front side of the paper in FIG. 2 with respect to the rotating substrate 30. The state in which the roller shaft 192 of the pair of registration rollers 191 is perpendicular to the conveying direction D of the recording paper P shown in FIG.

[0028] The pair of registration rollers 191 is provided on a rotating substrate 30. On the rotating substrate 30, bearings 31 and 32 of a roller shaft 192A, a drive gear 33, a connecting gear 34, a shaft drive motor 35, and a support unit 36 ​​are provided. The bearing 31 of the roller shaft 192A is provided overlapping the bearing 31 of the roller shaft 192B, and the bearing 32 of the roller shaft 192A is provided overlapping the bearing 32 of the roller shaft 192B. In other words, the bearings 31 and 32 of the roller shaft 192B are provided on the rotating substrate 30 via the bearings 31 and 32 of the roller shaft 192A (see FIG. 1).

[0029] Bearings 31 and 32 of a roller shaft 192A of the drive registration roller 191A rotatably support the roller shaft 192A (drive shaft). Bearings 31 and 32 of a roller shaft 192B of the driven registration roller 191B rotatably support the roller shaft 192B (drive shaft).

[0030] A driving gear 33 that rotates together with the roller shaft 192A is fixed to the shaft end of the roller shaft 192A of the driven registration roller 191A. The driving gear 33 meshes with a connecting gear 34 fixed to the output shaft of a shaft driving motor 35. As a result, the pair of registration rollers 191 rotates when driven by the shaft driving motor 35.

[0031] The support portion 36 is fixed to a support substrate 40 which is fixed to a part of the main body of the image forming apparatus 1. The support portion 36 is, for example, a cylindrical protrusion, and is loosely fitted into a hole provided in the rotating substrate 30. The support substrate 40 rotatably supports the rotating substrate 30 via the support portion 36. The support substrate 40 is provided with a rotation motor 41 and a pinion gear 42 which is attached to the output shaft of the rotation motor 41 and rotates together with the output shaft.

[0032] A rack gear 37 is provided at one end of the rotating base 30 on the bearing 32 side. The rack gear 37 meshes with a pinion gear 42 fixed to the output shaft of a swivel motor 41. As a result, the rotating base 30 rotates around the support part 36 as a rotation shaft by driving the swivel motor 41. Therefore, by rotating the swivel motor 41 clockwise in the figure, the bearing 32 side of the registration roller pair 191 is tilted downstream in the conveying direction D of the recording paper P with the bearing 31 side of the registration roller pair 191 as the rotation center (hereinafter, this state is referred to as a state in which the registration roller pair 191 is tilted downstream in the conveying direction D). On the other hand, by rotating the swivel motor 41 counterclockwise in the figure, the bearing 32 side of the registration roller pair 191 is tilted upstream in the conveying direction D of the recording paper P with the bearing 31 side of the registration roller pair 191 as the rotation center (hereinafter, this state is referred to as a state in which the registration roller pair 191 is tilted upstream in the conveying direction D). The configuration including the rotating base 30, the support portion 36, the rack gear 37, the support base 40, the turning motor 41, and the pinion gear 42 is an example of a tilt mechanism within the scope of the claims.

[0033] 3 is a diagram showing an example of a state in which the pair of registration rollers 191 is tilted downstream in the transport direction D. When the output shaft of the swivel motor 41 rotates clockwise in the figure, the rotating base plate 30 rotates counterclockwise around the support portion 36 as the rotation shaft, and the roller shaft 192 of the pair of registration rollers 191 is tilted downstream in the transport direction D.

[0034] 4 is a diagram showing an example of a state in which the pair of registration rollers 191 is tilted upstream in the transport direction D. When the output shaft of the swivel motor 41 rotates counterclockwise in the figure, the rotating base plate 30 rotates clockwise around the support portion 36 as the rotation axis, and the roller shaft 192 of the pair of registration rollers 191 is tilted upstream in the transport direction D.

[0035] As shown in Figures 3 and 4, by rotating the rotating base 30 and tilting the roller shaft 192 of the pair of registration rollers 191 so that it is parallel to the leading edge of the recording paper P, the recording paper P is transported in an uninclined position relative to the pair of registration rollers 191 and enters and is clamped in the nip portion N2 (Figure 1) formed by the pair of registration rollers 191.

[0036] After the recording paper P is sandwiched in the nip portion N2 formed by the pair of registration rollers 191, the rotating base plate 30 is rotated in the opposite direction to return the roller shaft 192 of the pair of registration rollers 191 to the initial state, thereby correcting the inclination of the recording paper P. In other words, the inclination of the recording paper P is corrected.

[0037] Fig. 5 is a functional block diagram showing a schematic diagram of the main internal configuration of the image forming apparatus 1. The image forming apparatus 1 includes a main control unit 100, an engine control unit 200, a registrationless control unit 300, a document feeder 6, a document reader 5, an image forming unit 12, a fixing unit 13, a paper feeder 14, a conveyor 19, an operation unit 47, and a storage device 8. Note that components similar to those of the image forming apparatus 1 shown in Fig. 1 are given the same reference numerals and detailed explanations will be omitted.

[0038] The document feeder 6 is provided on the top surface of the document reading unit 5 so as to be openable and closable by a hinge or the like. The document feeder 6 functions as a document pressing cover when reading a document placed on the platen glass. The document feeder 6 is an automatic document feeder called an ADF (Auto Document Feeder). The document feeder 6 includes a document placement tray, and supplies the document placed on the document placement tray to the document reading unit 5.

[0039] A description will be given of a case where a document reading operation is performed by the image forming apparatus 1. The document reading unit 5 optically reads an image of a document supplied to the document reading unit 5 by the document feeding unit 6 or a document placed on the platen glass, and generates image data. The image data generated by the document reading unit 5 is stored in an image memory or the like.

[0040] The following describes an image forming operation performed by the image forming apparatus 1. Based on image data generated by the document reading unit 5 or image data received from a computer serving as an external device connected via a network, the image forming unit 12 forms a toner image on recording paper P serving as a recording medium fed from a paper feed unit 14.

[0041] The fixing unit 13 applies heat and pressure to the recording paper P on which the toner image has been formed by the image forming unit 12, thereby fixing the toner image to the recording paper P. The recording paper P that has been subjected to the fixing process is discharged to a discharge tray. The paper supply unit 14 includes a plurality of paper supply cassettes 141 shown in FIG.

[0042] 1, toward the image forming unit 12. The conveying unit 19 includes a shaft driving motor 35, a driving motor 51 that supplies a rotational driving force to the roller shaft of the intermediate conveying roller pair 194 shown in FIG. 1, a registration sensor 195, an intermediate sensor 196, a turning motor 41, and an inclination detection sensor 193.

[0043] The storage device 8 is a large-capacity storage device such as a hard disk drive (HDD) or a solid state drive (SSD), etc. The storage device 8 stores various control programs and the like.

[0044] Operation unit 47 includes various hard keys and the like. Operation unit 47 receives user instructions, such as an instruction to execute an image forming operation, via the hard keys with respect to various operations and processes that image forming apparatus 1 can execute. Operation unit 47 includes display unit 473 that displays operation guides and the like for the user. Operation unit 47 receives input of user instructions based on a user's operation (touch operation) on an operation screen displayed on display unit 473 via a touch panel included in display unit 473, or a user's operation on the hard keys.

[0045] Display unit 473 is configured with an LCD (Liquid Crystal Display) or the like. Display unit 473 is equipped with a touch panel. When a user touches a button or key displayed on the screen, the touch panel receives an instruction associated with the touched position.

[0046] The main control unit 100, the engine control unit 200, and the registrationless control unit 300 each include a processor, a random access memory (RAM), a read only memory (ROM), and a dedicated hardware circuit. The processor is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), or a micro processing unit (MPU).

[0047] The main control unit 100 functions as a main control section 101 by the operation of the processor according to a first control program stored in the storage device 8. The engine control unit 200 functions as an engine control section 201 by the operation of the processor according to a second control program stored in the storage device 8. The registrationless control unit 300 functions as a registrationless control section 301 by the operation of the processor according to a third control program stored in the storage device 8. The first to third programs may be configured by the same control program.

[0048] The engine control unit 201 and the registrationless control unit 301 are examples of a first control unit and a second control unit, respectively, in the claims.

[0049] It should be noted that the main control unit 101 etc. can also be configured by hardware circuits, rather than being operated according to a control program by the main control unit 100 etc. The same applies to each embodiment below unless otherwise specified.

[0050] In addition, in this embodiment, an engine control unit 201 that controls a part that performs image formation is provided separately from the main control unit 101, but the present invention is not limited to this embodiment. For example, the engine control unit 201 and the main control unit 101 may be integrated, and the main control unit 101 may execute the functions and processes of the engine control unit 201.

[0051] For data communication between the main control unit 101, the engine control unit 201, and the registrationless control unit 301, for example, serial communication via a first communication line is used.

[0052] The main control unit 101 is responsible for controlling the overall operation of the image forming apparatus 1. The main control unit 101 is connected to the operation unit 47. The main control unit 101 receives instructions input by a user's touch operation on the operation unit 47, etc. The main control unit 101 controls the display of the display unit 473.

[0053] The engine control unit 200 is connected to the document feeder 6, the document reader 5, the image forming unit 12, the fixing unit 13, the paper feeder 14, and the transport unit 19. The engine control unit 201 performs drive control of each of these units. For example, the engine control unit 201 performs rotation control of the pair of registration rollers 191 in order to send out the recording paper P to the image forming unit 12. Specifically, the engine control unit 201 controls the shaft drive motor 35 to perform rotation control of the pair of registration rollers 191.

[0054] The registration-less control unit 300 is connected to the turning motor 41 and the tilt detection sensor 193 of the transport section 19. The registration-less control section 301 controls the turning motor 41 based on the detection result by the tilt detection sensor 193 to tilt the roller shaft 192 of the registration roller pair 191 upstream or downstream with respect to the transport direction D, thereby correcting the tilt of the recording paper P.

[0055] The registrationless control unit 301 uses serial communication to transmit tilt data indicating the direction and amount of tilt of the roller shaft 192 to the engine control unit 201.

[0056] The engine control unit 201 corrects the rotation speed of the pair of registration rollers 191 based on the direction and amount of tilt of the roller shaft 192 indicated by the tilt data received from the registrationless control unit 301 .

[0057] 3, when the pair of registration rollers 191 is tilted downstream with respect to the transport direction D, the distance from the recording paper P to the nip portion N2 formed by the pair of registration rollers 191 becomes longer than in the initial state, so the timing at which the recording paper P is sandwiched by the nip portion N2 becomes later than when the pair of registration rollers 191 is not tilted. Therefore, the engine control unit 201 performs a correction to increase the rotation speed of the pair of registration rollers 191. This adjusts the timing discrepancy.

[0058] On the other hand, as shown in Fig. 4, when the pair of registration rollers 191 is tilted upstream with respect to the transport direction D, the distance from the recording paper P to the nip portion N2 formed by the pair of registration rollers 191 becomes shorter than in the initial state, so the timing at which the recording paper P is sandwiched by the nip portion N2 becomes earlier than when the pair of registration rollers 191 is not tilted. Therefore, the engine control unit 201 performs a correction to slow down the rotation speed of the pair of registration rollers 191. This adjusts the timing discrepancy.

[0059] Next, an example of the first roller shaft tilting process performed by the registrationless control unit 301 will be described with reference to the flowchart shown in Fig. 6. Note that the registrationless control unit 301 performs the first roller shaft tilting process when it detects the leading edge of the recording paper P based on the image data detected by the tilt detection sensor 193.

[0060] The registrationless control unit 301 detects the inclination of the recording paper P with respect to the transport direction D based on the image data detected by the inclination detection sensor 193 (step S1). Based on the detected inclination of the recording paper P, the registrationless control unit 301 determines the direction and amount of inclination of the roller shaft 192 of the registration roller pair 191 so as to make the roller shaft 192 of the registration roller pair 191 parallel to the leading edge of the recording paper P (step S2).

[0061] The registrationless control unit 301 determines whether the difference between the currently determined direction and amount of tilt of the roller shaft 192 and the previously determined direction and amount of tilt of the roller shaft 192 is within a predetermined setting range (step S3).

[0062] If the registrationless control unit 301 determines that the difference between the current and previous tilt direction and amount of the roller shaft 192 is not within a predetermined setting range (NO in step S3), it transmits tilt data indicating the currently determined direction and amount of tilt of the roller shaft 192 to the engine control unit 201 via serial communication (step S4). After step S4, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base 30 based on the currently determined direction and amount of tilt of the roller shaft 192, and tilts the roller shaft 192 of the registration roller pair 191 (step S5).

[0063] On the other hand, when the registrationless control unit 301 determines that the difference between the current and previous tilting directions and amounts of the roller shaft 192 is within a predetermined setting range (i.e., there is no large difference between the current and previous tilting directions and amounts) (YES in step S3), it transmits a predetermined command code having a smaller data amount than the tilt data to the engine control unit 201 by serial communication (step S6). After step S6, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base 30 based on the currently determined tilting direction and amount of the roller shaft 192, and tilts the roller shaft 192 of the registration roller pair 191 (step S5).

[0064] The command code does not need to transmit information indicating the direction and amount of tilt of the roller shaft 192, and can easily be made smaller than the amount of tilt data since it only needs to be simple information. The registerless control unit 301 may transmit, as the command code, data indicating a value that is impossible for the tilt data to indicate.

[0065] Next, an example of the first rotation speed adjustment process performed by engine control unit 201 will be described with reference to the flowchart shown in Fig. 7. Note that engine control unit 201 performs the first rotation speed adjustment process when it receives data transmitted from registrationless control unit 301 by serial communication.

[0066] The engine control unit 201 judges whether the received data is tilt data (step S11). When the engine control unit 201 judges that the received data is tilt data (YES in step S11), it determines the rotation speed of the registration roller pair 191 according to the tilt direction and amount of the roller shaft 192 indicated by the tilt data (step S12). For example, the non-volatile memory or storage device 8 built in the engine control unit 200 stores a data table indicating the rotation speed of the registration roller pair 191 associated with the combination of the tilt direction and amount of the roller shaft 192. The engine control unit 201 uses the data table to determine the rotation speed of the registration roller pair 191 according to the tilt direction and amount of the roller shaft 192 indicated by the tilt data. Alternatively, the non-volatile memory or storage device 8 built in the engine control unit 200 stores each coefficient associated with the combination of the tilt direction and amount of the roller shaft 192. The engine control unit 201 uses the coefficient to calculate and determine the rotation speed of the pair of registration rollers 191 according to the direction and amount of tilt of the roller shaft 192 indicated by the tilt data.

[0067] After the process of step S12, the engine control unit 201 controls the drive of the shaft driving motor 35 so that the rotation speed of the registration roller pair 191 becomes the determined rotation speed of the registration roller pair 191 (step S15). This corrects the rotation speed of the registration roller pair 191. The process of step S15 is performed after the registrationless control unit 301 tilts the roller shaft 192 of the registration roller pair 191 based on the determined direction and amount of tilt of the roller shaft 192 (i.e., after step S5 shown in FIG. 6).

[0068] On the other hand, when the engine control unit 201 determines that the received data is not tilt data (NO in step S11), it determines whether the received data is a command code (step S13). When the engine control unit 201 determines that the received data is a command code (YES in step S13), it determines the rotation speed of the pair of registration rollers 191 according to the tilt direction and amount of the roller shaft 192 indicated by the previously received tilt data, using a data table or a coefficient (step S14). After processing in step S14, the engine control unit 201 controls the drive of the shaft drive motor 35 so that the rotation speed of the pair of registration rollers 191 becomes the determined rotation speed of the pair of registration rollers 191 (step S15). This corrects the rotation speed of the pair of registration rollers 191.

[0069] After the process of step S15, when the registrationless control unit 301 receives a signal transmitted from the registration sensor 195 indicating that the leading edge of the recording paper P has been detected, the registrationless control unit 301 calculates the nip timing at which the leading edge of the recording paper P is completely nipped by the registration roller pair 191 (i.e., the timing at which the recording paper P reaches the registration roller pair 191) based on the reception timing of the signal. For example, the registrationless control unit 301 calculates the nip timing as the point in time that a predetermined period of time has elapsed since the reception timing. When the calculated nip timing arrives, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base 30, and returns the roller shaft 192 of the registration roller pair 191 to the initial state.

[0070] Here, in steps S12 and S14, the rotational speed of the registration roller pair 191 determined by the engine control unit 201 is set to a rotational speed at which the timing at which the leading edge of the recording paper P sent out by the registration roller pair 191 reaches the nip portion N1 of the intermediate transfer belt 125 and the drive roller 125A when the registration roller pair 191, tilted as described above, is returned to its initial state while nipping the recording paper P, is reached when the recording paper P is not tilted with respect to the transport direction D, the registration roller pair 191 remains in its initial state, and the recording paper P is sent out by the registration roller pair 191 at the rotational speed before the above-mentioned correction.

[0071] If the engine control unit 201 determines that the received data is not a command code (NO in step S13), that is, if the engine control unit 201 has not received either tilt data or a command code, the first rotation speed adjustment process is terminated.

[0072] According to the first embodiment, the roller shaft 192 of the pair of registration rollers 191 is tilted in accordance with the tilt of the recording paper P, and at the timing when the leading edge of the recording paper P is completely nipped by the pair of registration rollers 191, the tilted roller shaft 192 of the pair of registration rollers 191 is returned to its initial state, so that the tilt of the recording paper P can be corrected to a normal state in which the leading edge of the recording paper P is perpendicular to the transport direction D. Also, because the rotation speed of the pair of registration rollers 191 is corrected based on the direction and amount of tilt of the roller shaft 192, even if the roller shaft 192 is tilted, the recording paper P can be supplied to the image forming unit 12 at the appropriate timing. This makes it possible to correct the tilt of the recording paper P while ensuring that the recording paper P is supplied to the image forming unit 12 at the appropriate timing.

[0073] Furthermore, according to the first embodiment, when the resistless control unit 301 determines that the difference between the current and previous tilt direction and amount of tilt of the roller shaft 192 is within a predetermined set range (i.e., there is no large difference between the current and previous tilts), it transmits a command code having a smaller data amount than the tilt data to the engine control unit 201 via serial communication instead of the tilt data.

[0074] This reduces the time that resources such as the CPU are occupied by communication. Also, by reducing the amount of communication data, the time required for communication can be shortened. As a result, the registrationless control unit 301 can quickly transition to control of the inclination of the roller shaft 192 after communication, and the transport control of the recording paper P can be performed with good responsiveness. Also, the engine control unit 201 can quickly start correction control of the rotation speed of the registration roller pair 191.

[0075] In the first embodiment, the registrationless control unit 301 transmits a command code to the engine control unit 201 when it determines that the difference between the current and previous tilt direction and amount of the roller shaft 192 is within a predetermined setting range, but the present invention is not limited to such an embodiment. For example, in another embodiment, the registrationless control unit 301 may transmit a command code to the engine control unit 201 only when the currently determined direction and amount of tilt of the roller shaft 192 are the same as the previously determined direction and amount of tilt of the roller shaft 192.

[0076] Furthermore, when the registrationless control unit 301 detects a communication error in the transmission of either the tilt data or the command code, the registrationless control unit 301 may execute a transmission retry process.

[0077] Second embodiment Hereinafter, an image forming apparatus 1 according to a second embodiment of the present invention will be described with reference to the drawings. The image forming apparatus 1 according to the second embodiment has the same configuration as the image forming apparatus 1 according to the first embodiment, except that the registrationless control unit 301 executes a second roller shaft tilting process instead of the first roller shaft tilting process, and the engine control unit 201 executes a second rotation speed adjustment process instead of the first rotation speed adjustment process. Hereinafter, the same configuration as the image forming apparatus 1 according to the first embodiment will not be described repeatedly.

[0078] Next, an example of the second roller shaft tilting process performed by the registrationless control unit 301 will be described with reference to the flowchart shown in Fig. 8. Note that the registrationless control unit 301 performs the second roller shaft tilting process when it detects the leading edge of the recording paper P based on the image data detected by the tilt detection sensor 193.

[0079] The registrationless control unit 301 detects the inclination of the recording paper P with respect to the transport direction D based on the image data detected by the inclination detection sensor 193 (step S1). Based on the detected inclination of the recording paper P, the registrationless control unit 301 determines the direction and amount of inclination of the roller shaft 192 of the registration roller pair 191 so as to make the roller shaft 192 of the registration roller pair 191 parallel to the leading edge of the recording paper P (step S2).

[0080] The registrationless control unit 301 transmits tilt data indicating the determined direction and amount of tilt of the roller shaft 192 to the engine control unit 201 by serial communication (step S3). After step S3, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base 30 based on the determined direction and amount of tilt of the roller shaft 192, and tilts the roller shaft 192 of the registration roller pair 191 (step S4).

[0081] Next, an example of the second rotation speed adjustment process performed by engine control unit 201 will be described with reference to the flowchart shown in Fig. 9. Note that engine control unit 201 performs the second rotation speed adjustment process when it receives data transmitted from registrationless control unit 301 by serial communication.

[0082] The engine control unit 201 judges whether or not a communication abnormality has occurred in the tilt data transmitted by serial communication from the registrationless control unit 301 (step S11). The engine control unit 201 on the receiving side of the serial communication detects, for example, a known parity error, an overrun error, or a framing error as the communication abnormality.

[0083] When the engine control unit 201 determines that no communication abnormality has occurred (NO in step S11), it determines the rotation speed of the pair of registration rollers 191 according to the tilt direction and amount of the roller shaft 192 indicated by the normally received tilt data (step S12). The engine control unit 201 determines the rotation speed of the pair of registration rollers 191 by using, for example, a data table or coefficients stored in the nonvolatile memory or storage device 8 built in the engine control unit 200, in the same manner as in the first embodiment.

[0084] After the process of step S12, the engine control unit 201 controls the drive of the shaft driving motor 35 so that the rotation speed of the registration roller pair 191 becomes the determined rotation speed of the registration roller pair 191 (step S18). This corrects the rotation speed of the registration roller pair 191. The process of step S18 is performed after the registrationless control unit 301 tilts the roller shaft 192 of the registration roller pair 191 based on the determined direction and amount of tilt of the roller shaft 192 (i.e., after step S4 shown in FIG. 8).

[0085] If the engine control unit 201 determines that no communication abnormality has occurred, it transmits response data to the registrationless control unit 301 indicating that the tilt data has been normally received.

[0086] On the other hand, when the engine control unit 201 determines that a communication abnormality has occurred (YES in step S11), that is, when a communication abnormality regarding the tilt data is detected, the engine control unit 201 performs a predetermined adjustment process regarding the rotation speed of the registration roller pair 191 (step S13). When the engine control unit 201 determines that a communication abnormality has occurred, it transmits response data indicating that the tilt data could not be received normally to the registrationless control unit 301. When the registrationless control unit 301 receives the response data from the engine control unit 201, it executes a retry process for transmitting the tilt data.

[0087] As the above-mentioned predetermined adjustment process, the engine control unit 201, for example, (i) performs a process of changing the rotation speed of the registration roller pair 191 to a predetermined low speed that is slower than the predetermined rotation speed under normal circumstances when no communication abnormality occurs, (ii) performs a process of changing the rotation speed of the registration roller pair 191 based on the type or size of the recording paper P, or (iii) performs a process of correcting the rotation speed of the registration roller pair 191 based on the tilt data that was previously received normally.

[0088] The above case (ii) will be described. In the image forming apparatus 1, recording paper P that is too thick or too thin is more difficult to handle than recording paper P of standard thickness. Also, recording paper P that is too long or too short in the width direction is more difficult to handle than recording paper P of standard length. Therefore, the engine control unit 201 may temporarily stop the rotation of the pair of registration rollers 191 as a process of changing the rotation speed of the pair of registration rollers 191, for example, when at least one of the cases where the thickness of the recording paper P is outside a predetermined range and the size of the recording paper P is outside a predetermined range.

[0089] After the process of step S13, the engine control unit 201 determines whether or not the tilt data retransmitted by the retry process by the registrationless control unit 301 has been successfully received (step S15).

[0090] When the engine control unit 201 determines that the tilt data has been successfully received (YES in step S15), it determines the rotation speed of the pair of registration rollers 191 according to the tilt direction and amount of the roller shaft 192 indicated by the tilt data (step S12). After processing in step S12, the engine control unit 201 controls the drive of the shaft drive motor 35 so that the rotation speed of the pair of registration rollers 191 becomes the determined rotation speed of the pair of registration rollers 191 (step S18). This corrects the rotation speed of the pair of registration rollers 191.

[0091] In addition, in step S18, the engine control unit 201 may further determine the rotation speed of the pair of registration rollers 191 based on the type or size of the recording paper, as well as the time required for recovery from the occurrence of the communication abnormality to the normal reception of the inclination data.

[0092] For example, as shown in FIG. 3, when the pair of resist rollers 191 is inclined downstream with respect to the conveying direction D, the engine control unit 201 corrects the rotation speed of the pair of resist rollers 191 to be faster, but as the time required for recovery becomes longer, the engine control unit 201 determines the rotation speed of the pair of resist rollers 191 so that the rotation speed of the pair of resist rollers 191 is further increased.

[0093] On the other hand, as shown in FIG. 4, when the pair of registration rollers 191 is inclined upstream with respect to the conveying direction D, the engine control unit 201 corrects the rotation speed of the pair of registration rollers 191 to slow down, but as the time required for recovery becomes longer, the engine control unit 201 determines the rotation speed of the pair of registration rollers 191 so as to further slow down the rotation speed of the pair of registration rollers 191.

[0094] On the other hand, if the engine control unit 201 determines that the inclination data has not been successfully received (NO in step S15), it determines whether the leading edge of the recording paper P has reached the pair of registration rollers 191 based on the signal sent from the registration sensor 195 (step S17).

[0095] That is, the engine control unit 201 judges whether or not the inclination data retransmitted by the retry process by the registrationless control unit 301 has been successfully received (step S15) before the leading edge of the recording paper P reaches the registration roller pair 191 (NO in step S17). When the engine control unit 201 judges that the retransmitted inclination data has been successfully received (YES in step S15) before the leading edge of the recording paper P reaches the registration roller pair 191 (NO in step S17), it determines the rotation speed of the registration roller pair 191 according to the tilt direction and amount of the roller shaft 192 indicated by the inclination data (step S12). After the process of step S12, the engine control unit 201 performs the process of step S18.

[0096] After the process of step S18, when the registrationless control unit 301 receives a signal from the registration sensor 195 indicating that the leading edge of the recording paper P has been detected, it calculates the nip timing based on the reception timing of the signal, in the same manner as in the first embodiment. When the calculated nip timing arrives, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base plate 30, and returns the roller shaft 192 of the registration roller pair 191 to the initial state.

[0097] Here, as in the first embodiment described above, in step S12, the rotational speed of the registration roller pair 191 determined by the engine control unit 201 is set to a rotational speed at which the timing at which the leading edge of the recording paper P sent out by the registration roller pair 191 reaches the nip portion N1 of the intermediate transfer belt 125 and the drive roller 125A when the registration roller pair 191 tilted as described above is returned to its initial state while nipping the recording paper P is reached when the recording paper P is not tilted with respect to the conveying direction D, the registration roller pair 191 remains in its initial state, and the recording paper P is sent out by the registration roller pair 191 at the rotational speed before correction.

[0098] On the other hand, if the engine control unit 201 does not determine that the retransmitted inclination data has been successfully received before the leading edge of the recording paper P reaches the pair of registration rollers 191 (NO in step S15, YES in step S17), it terminates the second rotation speed adjustment process.

[0099] Incidentally, in order to supply the recording paper P to the image forming unit at an appropriate timing, the engine control unit 201 corrects the rotation speed of the pair of registration rollers 191 based on the direction and amount of tilt of the roller shaft 192. However, in this embodiment, the engine control unit 201, which performs control to rotate the registration rollers, and the registrationless control unit 301, which performs control to tilt the roller shaft 192, are independent, so it is necessary to transmit tilt data from the registrationless control unit 301 to the engine control unit 201.

[0100] However, if a communication error occurs and the tilt data is not received correctly by the engine control unit 201, it becomes difficult for the engine control unit 201 to appropriately correct the rotation speed. As a result, there is a risk that image formation on the recording paper P will be adversely affected.

[0101] In contrast, according to the second embodiment, when a communication abnormality occurs regarding the inclination data, instead of correcting the rotation speed, a predetermined adjustment process is performed regarding the rotation speed of the pair of registration rollers 191. By executing this adjustment process, adverse effects that occur when a communication abnormality occurs regarding the inclination data are suppressed. As described above, the predetermined adjustment process may, for example, correct the rotation speed of the pair of registration rollers 191 based on the inclination data that was normally received last time, or reduce the rotation speed of the pair of registration rollers 191 compared to normal times when no communication abnormality occurs.

[0102] When the recording paper P is inclined with respect to the transport direction D, it is expected that there is a high possibility that the recording paper P is inclined to the same degree as the previous time the recording paper P was transported. Therefore, it is reasonable to perform the above correction based on the inclination data that was normally received last time.

[0103] In another embodiment, when a communication abnormality occurs, the engine control unit 201 may control the drive motor 51 to perform the predetermined adjustment process of changing the rotation speed of the intermediate transport roller pair 194 to a predetermined low speed that is slower than the normal speed when no communication abnormality occurs. This makes it possible to buy time until the communication abnormality is restored.

[0104] Third embodiment Hereinafter, an image forming apparatus 1 according to a third embodiment of the present invention will be described with reference to the drawings. The image forming apparatus 1 according to the third embodiment has the same configuration as the image forming apparatus 1 according to the first embodiment, except that the registrationless control unit 301 executes a third roller shaft tilting process instead of the first roller shaft tilting process, and the engine control unit 201 executes a third rotation speed adjustment process instead of the first rotation speed adjustment process. Hereinafter, the same configuration as the image forming apparatus 1 according to the first embodiment will not be described repeatedly.

[0105] Next, an example of the third roller shaft tilting process performed by the registrationless control unit 301 will be described with reference to the flowchart shown in Fig. 10. Note that the registrationless control unit 301 performs the third roller shaft tilting process when it detects the leading edge of the recording paper P based on the image data detected by the tilt detection sensor 193.

[0106] The registrationless control unit 301 detects the inclination of the recording paper P with respect to the transport direction D based on the image data detected by the inclination detection sensor 193 (step S1). Based on the detected inclination of the recording paper P, the registrationless control unit 301 determines the direction and amount of inclination of the roller shaft 192 of the registration roller pair 191 so as to make the roller shaft 192 of the registration roller pair 191 parallel to the leading edge of the recording paper P (step S2).

[0107] The registrationless control unit 301 transmits tilt data indicating the determined direction and amount of tilt of the roller shaft 192 to the engine control unit 201 by serial communication via the first communication line (step S3). After the process of step S3, the registrationless control unit 301 determines whether or not a non-execution notification has been received via a general-purpose port that is connected to the registrationless control unit 301 and enables communication with the engine control unit 201 (step S4).

[0108] As will be explained in detail later, if a communication error occurs in the tilt data sent from the registrationless control unit 301, the engine control unit 201 sends a predetermined non-execution notification to the registrationless control unit 301 via the general-purpose port so as not to perform control to tilt the roller shaft 192 of the registration roller pair 191. If the registrationless control unit 301 determines that it has not received a non-execution notification via the general-purpose port (NO in step S4), it controls the turning motor 41 to rotate the rotating base 30 based on the determined direction and amount of tilting of the roller shaft 192, and tilts the roller shaft 192 of the registration roller pair 191 (step S7).

[0109] On the other hand, if the registrationless control unit 301 determines that a non-execution notification has been received via the general-purpose port (YES in step S4), it ends the third roller shaft tilting process without performing the process in step S7.

[0110] Next, an example of the third rotation speed adjustment process performed by engine control unit 201 will be described with reference to the flowchart shown in Fig. 10. Note that engine control unit 201 performs the third rotation speed adjustment process when it receives data transmitted from registrationless control unit 301 by serial communication.

[0111] The engine control unit 201 judges whether or not a communication abnormality has occurred in the tilt data transmitted by serial communication from the registrationless control unit 301 (step S11). The engine control unit 201 on the receiving side of the serial communication detects, for example, a known parity error, an overrun error, or a framing error as the communication abnormality.

[0112] When the engine control unit 201 determines that no communication abnormality has occurred (NO in step S11), it determines the rotation speed of the pair of registration rollers 191 according to the tilt direction and amount of the roller shaft 192 indicated by the normally received tilt data (step S12). The engine control unit 201 determines the rotation speed of the pair of registration rollers 191 by using, for example, a data table or coefficients stored in the nonvolatile memory or storage device 8 built in the engine control unit 200, in the same manner as in the first embodiment.

[0113] After the process of step S12, the engine control unit 201 controls the drive of the shaft driving motor 35 so that the rotation speed of the registration roller pair 191 becomes the determined rotation speed of the registration roller pair 191 (step S13). This corrects the rotation speed of the registration roller pair 191. The process of step S18 is performed after the registrationless control unit 301 tilts the roller shaft 192 of the registration roller pair 191 based on the determined direction and amount of tilt of the roller shaft 192 (i.e., after step S7 shown in FIG. 10).

[0114] After the process of step S13, when the registrationless control unit 301 receives a signal from the registration sensor 195 indicating that the leading edge of the recording paper P has been detected, it calculates the nip timing based on the reception timing of the signal, in the same manner as in the first embodiment. When the calculated nip timing arrives, the registrationless control unit 301 controls the turning motor 41 to rotate the rotating base plate 30, and returns the roller shaft 192 of the registration roller pair 191 to the initial state.

[0115] Here, as in the first embodiment described above, in step S12, the rotational speed of the registration roller pair 191 determined by the engine control unit 201 is set to a rotational speed at which the timing at which the leading edge of the recording paper P sent out by the registration roller pair 191 reaches the nip portion N1 of the intermediate transfer belt 125 and the drive roller 125A when the registration roller pair 191 tilted as described above is returned to its initial state while nipping the recording paper P is reached when the recording paper P is not tilted with respect to the conveying direction D, the registration roller pair 191 remains in its initial state, and the recording paper P is sent out by the registration roller pair 191 at the rotational speed before correction.

[0116] On the other hand, if the engine control unit 201 determines that a communication abnormality has occurred (YES in step S11), that is, if it detects a communication abnormality regarding the tilt data, it sends a predetermined non-execution notification to the registrationless control unit 301 via a general-purpose port that is connected to the engine control unit 201 and enables communication with the registrationless control unit 301, so as not to perform control to tilt the roller axis 192 of the registration roller pair 191 (step S14).

[0117] That is, the engine control unit 201 transmits a non-execution notification to the registrationless control unit 301 through a general-purpose port as a second communication line different from the first communication line for communicating the tilt data. After the process of step S14, the engine control unit 201 ends the third rotation speed adjustment process.

[0118] Incidentally, in order to supply the recording paper P to the image forming unit at an appropriate timing, the engine control unit 201 corrects the rotation speed of the pair of registration rollers 191 based on the direction and amount of tilt of the roller shaft 192. However, in this embodiment, the engine control unit 201, which performs control to rotate the registration rollers, and the registrationless control unit 301, which performs control to tilt the roller shaft 192, are independent, so it is necessary to transmit tilt data from the registrationless control unit 301 to the engine control unit 201.

[0119] However, if a communication error occurs and the tilt data is not received correctly by the engine control unit 201, it becomes difficult for the engine control unit 201 to appropriately correct the rotation speed. As a result, there is a risk that image formation on the recording paper P will be adversely affected.

[0120] In contrast, according to the third embodiment, when a communication abnormality occurs regarding the tilt data, a non-execution notice is sent from the engine control unit 201 (receiver of the tilt data) to the registrationless control unit 301 (transmitter of the tilt data) to prevent control for tilting the roller shaft 192. This makes it possible to prevent the roller shaft 192 of the registration roller pair 191 from being tilted under circumstances in which the rotation speed of the registration roller pair 191 cannot be corrected. As a result, it is possible to suppress adverse effects that occur when a communication abnormality occurs regarding the tilt data.

[0121] Furthermore, when an abnormality occurs in communication via the first communication line for communicating tilt data, the non-execution notification is transmitted via a second communication line different from the first communication line, so that the non-execution notification can be reliably transmitted to the registrationless control unit 301, improving responsiveness. For example, the engine control unit 201 can transmit the non-execution notification to the registrationless control unit 301 by a simple process of switching a signal from a general-purpose port serving as the second communication line, which is normally "Low", to "High."

[0122] The method of detecting a communication abnormality by the engine control unit 201 is not limited to the above-described method of detecting a parity error, an overrun error, or a framing error as a communication abnormality. For example, in another embodiment, the engine control unit 201 may determine that a communication abnormality has occurred when the engine control unit 201 does not receive tilt data within a predetermined time period during which tilt data should be received under normal circumstances when no communication abnormality has occurred.

[0123] For example, the engine control unit 201 measures a predetermined time for receiving the above-mentioned tilt data by monitoring the transport status of the recording paper P. For example, the engine control unit 201 detects the timing at which the leading edge of the recording paper P reaches the pair of intermediate transport rollers 194 based on a signal obtained from the intermediate sensor 196, and measures the elapsed time from the point at which the leading edge of the recording paper P reaches the pair of intermediate transport rollers 194.

[0124] The engine control unit 201 calculates the time T required from when the leading edge of the recording paper P reaches the pair of intermediate transport rollers 194 until it reaches the pair of registration rollers 191, based on the rotation speed of the pair of intermediate transport rollers 194. If the engine control unit 201 does not receive the tilt data before the elapsed time reaches time T, it determines that a communication abnormality regarding the tilt data has occurred.

[0125] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. Furthermore, the configuration and processing of the above embodiment shown in Figures 1 to 11 are merely one embodiment of the present invention, and the present invention is not limited to the configuration and processing.

Claims

1. An image forming unit that forms an image on a recording paper; a registration roller that is provided upstream of the image forming unit in a predetermined recording paper transport direction and sends the recording paper to the image forming unit; A first control unit that controls the rotation of the registration roller; a tilt detection sensor that detects a tilt of the recording paper with respect to the transport direction; a tilting mechanism that tilts a roller axis of the registration roller, which is initially perpendicular to the conveying direction, toward an upstream side or a downstream side with respect to the conveying direction; a second control unit that controls the tilt mechanism to tilt the roller shaft upstream or downstream with respect to the transport direction based on a detection result of the tilt detection sensor, and controls the tilt mechanism to return the tilted roller shaft to the initial state when the recording paper reaches the registration roller, The second control unit transmits tilt data indicating a direction and an amount of tilt of the roller shaft to the first control unit, The first control unit corrects the rotation speed of the registration roller based on the tilt direction and amount of the roller shaft indicated by the tilt data received from the second control unit, the second control unit determines tilt data indicating a direction and amount of tilt of the roller shaft based on a detection result of the tilt detection sensor, and when the currently determined direction and amount of tilt of the roller shaft are the same as the previously determined direction and amount of tilt of the roller shaft, or when the difference between the two is within a predetermined setting range, transmits a predetermined command code having a smaller data amount than the tilt data to the first control unit instead of transmitting the tilt data to the first control unit; When the first control unit receives the command code, the first control unit corrects the rotation speed using the tilt data previously received.

2. The image forming apparatus according to claim 1 , wherein the second control unit transmits either the tilt data or the command code to the first control unit by using serial communication.

3. The image forming apparatus according to claim 1 , wherein the second control unit executes a retry process for the transmission when a communication abnormality is detected in the transmission of either the tilt data or the command code.

4. An image forming unit that forms an image on a recording paper; a registration roller that is provided upstream of the image forming unit in a predetermined recording paper transport direction and sends the recording paper to the image forming unit; A first control unit that controls the rotation of the registration roller; a tilt detection sensor that detects a tilt of the recording paper with respect to the transport direction; a tilting mechanism that tilts a roller axis of the registration roller, which is initially perpendicular to the conveying direction, toward an upstream side or a downstream side with respect to the conveying direction; a second control unit that controls the tilt mechanism to tilt the roller shaft upstream or downstream with respect to the transport direction based on a detection result of the tilt detection sensor, and controls the tilt mechanism to return the tilted roller shaft to the initial state when the recording paper reaches the registration roller, The second control unit transmits tilt data indicating a direction and an amount of tilt of the roller shaft to the first control unit, The first control unit corrects the rotation speed of the registration roller based on the tilt direction and amount of the roller shaft indicated by the tilt data received from the second control unit, An image forming apparatus, wherein the first control unit corrects the rotation speed of the registration roller when it does not detect a communication abnormality in the inclination data, and performs a predetermined adjustment process on the rotation speed of the registration roller when it detects the communication abnormality.

5. 5. The image forming apparatus according to claim 4, wherein the first control unit, when detecting the communication abnormality, performs the adjustment process by changing the rotation speed based on a type or a size of the recording paper.

6. 5. The image forming apparatus according to claim 4, wherein, when the first control unit detects the communication abnormality, the first control unit performs, as the adjustment process, a process of changing the rotation speed to a predetermined low speed that is slower than a normal speed when the communication abnormality is not occurring.

7. 5. The image forming apparatus according to claim 4, wherein, when the communication abnormality is detected, the first control unit performs, as the adjustment process, a process of correcting the rotation speed based on the tilt data that was normally received last time.

8. The second control unit executes a retry process of the transmission when the communication abnormality is detected, The image forming apparatus of claim 5, wherein the first control unit, upon receiving the tilt data, corrects the rotational speed based on the type or size of the recording paper, as well as the time required for recovery from the occurrence of the communication abnormality to successfully receiving the tilt data.

9. an intermediate transport roller provided upstream of the registration roller in the transport direction for transporting the recording paper to the registration roller; 5. The image forming apparatus according to claim 4, wherein, when the communication abnormality occurs, the first control unit performs, as the adjustment process, a process of changing the rotation speed of the intermediate transport roller to a predetermined low speed that is slower than a normal speed when the communication abnormality does not occur.

10. The image forming apparatus of claim 5, wherein the first control unit temporarily stops rotation of the registration roller as a process for changing the rotation speed when at least one of the thickness of the recording paper is outside a predetermined range and the size of the recording paper is outside a predetermined range.

11. An image forming unit that forms an image on a recording paper; a registration roller that is provided upstream of the image forming unit in a predetermined recording paper transport direction and sends the recording paper to the image forming unit; A first control unit that controls the rotation of the registration roller; a tilt detection sensor that detects a tilt of the recording paper with respect to the transport direction; a tilting mechanism that tilts a roller axis of the registration roller, which is initially perpendicular to the conveying direction, toward an upstream side or a downstream side with respect to the conveying direction; a second control unit that controls the tilt mechanism to tilt the roller shaft upstream or downstream with respect to the transport direction based on a detection result of the tilt detection sensor, and controls the tilt mechanism to return the tilted roller shaft to the initial state when the recording paper reaches the registration roller, The second control unit transmits tilt data indicating a direction and an amount of tilt of the roller shaft to the first control unit, The first control unit corrects the rotation speed of the registration roller based on the tilt direction and amount of the roller shaft indicated by the tilt data received from the second control unit, The second control unit transmits the tilt data to the first control unit through a first communication line, When the first control unit does not detect a communication abnormality in the tilt data, it corrects the rotation speed of the registration roller, and when the first control unit detects the communication abnormality, it sends a predetermined non-execution notification to the second control unit via a second communication line different from the first communication line to prevent the second control unit from performing the control on the roller shaft.

12. a general-purpose port connected to the first control unit as the second communication line; The image forming apparatus according to claim 11 , wherein the first control unit transmits the non-execution notification to the second control unit via the general-purpose port.

13. The image forming apparatus according to claim 11 , wherein the second control unit does not perform the control on the roller shaft when the non-execution notice is received.

14. 12. The image forming apparatus according to claim 11, wherein the first control unit determines that the communication abnormality has occurred when the tilt data is not received within a predetermined time during which the tilt data should be received under normal circumstances when the communication abnormality is not occurring.

15. 15. The image forming apparatus according to claim 14, wherein the first control unit measures the predetermined time for receiving the tilt data by monitoring a transport status of the recording paper.

16. an intermediate transport roller provided upstream of the registration roller in the transport direction for transporting the recording paper to the registration roller; The image forming apparatus of claim 15, wherein the first control unit measures the elapsed time from the point at which the leading edge of the recording paper reaches the intermediate transport roller, and determines that the communication abnormality has occurred if the inclination data is not received by the time the elapsed time reaches the time required from the point at which the leading edge of the recording paper reaches the intermediate transport roller to the registration roller.

Images