CN113601982A

CN113601982A - Image forming apparatus

Info

Publication number: CN113601982A
Application number: CN202110960928.4A
Authority: CN
Inventors: 刘汉莉; 罗艳辉
Original assignee: Zhuhai Nasda Lehmann Technology Co ltd
Current assignee: Zhuhai Nasda Lehmann Technology Co ltd
Priority date: 2021-08-20
Filing date: 2021-08-20
Publication date: 2021-11-05

Abstract

The application discloses imaging device, this imaging device include paper feed passageway, first sensor, second sensor and rubber roll, and the paper feed passageway has paper feed end and goes out the paper end, and first sensor sets up in paper feed end, and the second sensor sets up in a paper end, and the rubber roll sets up in paper feed passageway for drive print media removes to a paper end by the paper feed end. When the detection method is used for detecting whether the printing medium deflects, whether the printing medium enters the paper feeding channel or not is detected through the first sensor, when the first sensor detects that the printing medium enters the paper feeding channel, the printing medium is driven to move from the paper feeding end to the paper discharging end through the rubber roller, at least part of the second sensor is covered by the printing medium, so that the second sensor has dynamic parameters which can be used for determining whether the printing medium deflects or not, the dynamic parameters are related to the condition that the second sensor is covered by the printing medium and the running speed of the rubber roller, the interference of external environment and human factors is avoided, and the detection precision is improved.

Description

Image forming apparatus

Technical Field

The present application relates to the field of imaging technology, and more particularly, to an imaging apparatus with a print media skew detection device.

Background

A printing medium (e.g., paper, film, etc.) is imaged by a printing unit of an image forming apparatus, and if the printing medium enters the printing unit obliquely, problems such as paper jam and skew of printing contents are easily caused. In a conventional printer having a printing medium skew detection function, sensors are provided on both sides of a printing medium inlet/outlet passage, and a skew of a printing medium is calculated from a time difference between the sensors on both sides. However, the calculation of the skew of the printing medium by the time difference is easily interfered by external environment and human factors, and has poor accuracy.

Disclosure of Invention

In order to overcome the problems of the prior art, the present application provides an imaging device capable of avoiding interference from external environment and human factors.

In order to achieve the above purpose, the following technical solutions are specifically adopted in the present application:

the present application provides an image forming apparatus including:

the paper feeding channel is provided with a paper feeding end and a paper discharging end;

the first sensor is arranged at the paper feeding end;

the second sensor is arranged at the paper outlet end;

the rubber roller is arranged in the paper feeding channel and used for driving the printing medium to move from the paper feeding end to the paper discharging end;

when detecting whether the printing medium deflects, detecting whether a printing medium enters the paper feeding channel through the first sensor, and when detecting that the printing medium enters the paper feeding channel, driving the printing medium to move from the paper feeding end to the paper discharging end through the rubber roller so that the second sensor is at least partially covered by the printing medium, so that the second sensor has a dynamic parameter which can be used for determining whether the printing medium deflects, wherein the dynamic parameter is related to the condition that the second sensor is covered by the printing medium.

In a specific embodiment, the image forming apparatus further includes a controller, the controller is connected to the first sensor, the second sensor and the rubber roller respectively, and the controller is configured to control a movement of the rubber roller according to a detection result of the first sensor and determine whether the printing medium is skewed according to a dynamic parameter of the second sensor.

In a particular embodiment, the controller is particularly adapted to determine whether the print medium is skewed based on a time parameter required for the second sensor to be partially or fully covered by the print medium.

In a specific embodiment, the controller is specifically configured to detect an actual time parameter required for the second sensor to be completely covered by the printing medium, compare the actual time parameter with a preset time parameter, and determine whether the printing medium is skewed according to a comparison result.

In a specific embodiment, the preset time parameter is calculated according to the length of the second sensor and the rotation speed of the rubber roller.

In a particular embodiment, the controller is particularly configured to determine whether the print medium is skewed based on a voltage parameter of the second sensor, wherein the voltage parameter of the second sensor is related to a condition of the second sensor being covered by the print medium.

In a specific embodiment, the controller is specifically configured to detect a voltage variation parameter of the second sensor within a preset time, compare the voltage variation parameter with a preset voltage parameter, and determine whether the printing medium is skewed according to a comparison result.

In a particular embodiment, the controller is particularly configured to determine whether the print medium is skewed based on a current parameter of the second sensor, wherein the current parameter of the second sensor is related to a condition of the second sensor being covered by the print medium.

In a specific embodiment, the controller is specifically configured to compare the current variation parameter with a preset current parameter according to the current variation parameter of the second sensor within a preset time, and determine whether the printing medium is skewed according to the comparison result.

In a specific embodiment, a length of the second sensor extends along a conveying direction of the printing medium in the paper feed path.

In a specific embodiment, two first sensors are arranged, and the two first sensors are arranged along the width extension direction of the paper feeding channel and are positioned at two sides of the paper feeding end.

In a specific embodiment, when it is determined that the printing medium is skewed, the controller controls the rubber roller to rotate in a reverse direction, so that the printing medium exits the rubber roller, and performs at least one of prompting, giving an alarm, and stopping printing by a user.

In a specific embodiment, when it is determined that the printing medium is not skewed, the controller controls the rubber roller to rotate in a reverse direction, so that the printing medium is retreated to a printing starting position of the paper feeding end and printing is performed.

In a specific embodiment, the second sensor is further configured to detect whether the printing medium is completely output.

Compared with the prior art, the imaging device has the advantages that the first sensor is arranged at the paper inlet end, the second sensor is arranged at the paper outlet end, when whether the printing medium deflects or not is detected, whether the printing medium enters the paper inlet channel or not is detected through the first sensor, when the first sensor detects that the printing medium enters the paper inlet channel, the printing medium is driven by the rubber roller to move from the paper inlet end to the paper outlet end, at least part of the second sensor is covered by the printing medium, so that the second sensor has dynamic parameters which can be used for determining whether the printing medium deflects or not, the dynamic parameters are related to the condition that the second sensor is covered by the printing medium and the running speed of the rubber roller, the running speed of the rubber roller is controllable, interference of external environment and human factors is avoided, and detection precision is improved.

Drawings

Fig. 1 is a partial configuration diagram of a conventional image forming apparatus with a skew detecting device in which a printing medium enters a paper feeding path in a skewed state.

Fig. 2 is a partial configuration view of a conventional image forming apparatus with a skew detecting device, in which a printing medium is fed into a paper feed path in a normal state.

Fig. 3 is a schematic structural diagram of an imaging apparatus according to an embodiment of the present application.

Fig. 4 is a schematic view of another perspective structure of the imaging apparatus according to the embodiment of the present application.

Fig. 5 is a schematic structural diagram of an image forming apparatus in an open state according to an embodiment of the present application.

Fig. 6 is a schematic structural diagram of another viewing angle of the image forming apparatus in an open state according to the embodiment of the present application.

Fig. 7 is a schematic view of a portion of an image forming apparatus with a skew detection device according to an embodiment of the present application, in which a printing medium enters a paper feed path in a skewed state.

Fig. 8 is a schematic diagram illustrating a printing medium entering an image forming apparatus in a normal state according to an embodiment of the present application.

Fig. 9 is a schematic diagram illustrating that a printing medium enters an image forming apparatus in a tilted state according to an embodiment of the present application.

Fig. 10 is a schematic partial structural view of an imaging apparatus according to another embodiment of the present application.

The attached drawings are as follows:

1. a main body; 2. an upper cover; 3. a paper feed path; 31. a paper feeding end; 32. a paper outlet end; 4. a rubber roller; 5. a first sensor; 6. a second sensor; 7. a printhead assembly; 8. a first gear; 9. a second gear; 10. a display screen; 11. a switch button; 12. a charging port; 13. a baffle plate; 100. an imaging device; 200. paper; 3', a paper feed channel; 5', a sensor; 200' and a printing medium.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In the description of the present application, unless explicitly stated or limited otherwise, the terms "first", "second", and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless specified or indicated otherwise; the terms "connected," "fixed," and the like are to be construed broadly and may, for example, be fixedly connected, detachably connected, integrally connected, or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In the description of the present application, it should be understood that the terms "upper" and "lower" used in the description of the embodiments of the present application are used in a descriptive sense only and not for purposes of limitation. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on "or" under "the other element or be indirectly on" or "under" the other element via an intermediate element.

Image forming apparatuses such as thermal printers, thermal inkjet printers, laser printers, and the like are generally provided with a paper feed path for conveying a printing medium. A rubber roller and a printing component, such as a printing head (thermal, inkjet, laser, etc.), are usually disposed on the printing channel, and the printing medium (such as paper, cloth, film, etc., which is described herein by taking paper as an example) is pressed and rolled by the rubber roller to drive the printing medium to move toward the paper output direction of the paper feeding channel, and the printing head forms an image on the printing medium.

Referring to fig. 1 and 2, fig. 1 is a partial structural view of a conventional image forming apparatus with a skew detecting device, in which a printing medium enters a paper feeding path in a skewed state; fig. 2 is a partial configuration view of a conventional image forming apparatus with a skew detecting device, in which a printing medium is fed into a paper feed path in a normal state. In the prior art, in order to detect whether the printing medium 200' is deflected when entering the paper feeding path 3', two pairs of sensors 5' are arranged at the paper feeding end (paper feeding side of the rubber roller 4 ') of the paper feeding path 3' along the width extending direction (X direction in fig. 1) of the paper feeding path 3', and the transmitter and the receiver of each pair of sensors 5' are respectively arranged at the upper and lower sides of the paper feeding end of the paper feeding path 3' (or in other ways, as in one side, when there is a printing medium shielding by reflecting a received signal, there is a reflected signal, otherwise there is no reflected signal or the reflected signal is very weak), and when the signal propagation path of each pair of sensors 5' is shielded by the printing medium 200', the receiver of each pair of sensors 5' does not receive a signal, and a signal change occurs. When the printing medium 200' enters the paper feeding path 3', it is determined whether the printing medium 200' is skewed by detecting a time difference when the printing medium 200' blocks the signal propagation paths of the two pairs of sensors 5 '.

However, in a small and narrow printer, the paper feed path is short, and when the paper is manually fed, the paper may cover two pairs of sensors 5' one after the other, and at this time, the printer determines that the paper is deflected, and performs an alarm, stops printing, and the like. However, in the case of manual paper feeding, even if the paper covers the sensor 5', the paper angle may be manually adjusted, and if the paper is corrected at this time, the data on the printer sensor side is not changed, and it is considered that the paper is in a skew state, normal printing cannot be performed. In this way, in a printer of a relatively small size, a narrow size, or the like, since the paper feed path is short, detection deviation due to manual paper feeding cannot be avoided. In addition, although there is a possibility that the paper is skewed after the paper angle is adjusted manually, the printer prints the paper assuming that the paper is not skewed by covering the sensor 5', which causes problems such as paper jam and skew of data image printing.

Fig. 3 to 6 are schematic diagrams of a structure of an imaging device provided in an embodiment of the present application, fig. 3 is a schematic diagram of a structure of another viewing angle of the imaging device provided in the embodiment of the present application, fig. 5 is a schematic diagram of a structure of an imaging device in an open state provided in the embodiment of the present application, and fig. 6 is a schematic diagram of a structure of another viewing angle of an imaging device in an open state provided in the embodiment of the present application. In the present embodiment, the image forming apparatus 100 includes a main body 1, an upper cover 2, a paper feed path 3, a blanket 4, a first gear 8, a second gear 9, and a printhead assembly 7. The upper cover 2 is movably connected to the main body 1, and when the upper cover 2 covers the main body 1, a paper feeding channel 3 is formed, and the paper feeding channel 3 is used for conveying a printing medium. The rubber roller 4 is rotatably connected to the upper cover 2 and used for driving the printing medium entering the paper feed channel 3 to move. The first gear 8 is arranged on the main body 1, the second gear 9 is connected to one end of the rubber roller 4, and the second gear 9 is matched with the first gear 8. When the upper cover 2 covers the main body 1, the rubber roller 4 is positioned in the paper feeding channel 3, and the second gear 9 is meshed with the first gear 8, so that a driving part arranged in the main body 1 can drive the rubber roller 4 to rotate through the first gear 8 and the second gear 9, and further, the printing medium is driven to move through the rolling of the rubber roller 4. The printing head assembly 7 is arranged on the paper feed channel 3, and when the upper cover 2 covers the main body 1, the rubber roller 4 is abutted to the printing head assembly 7, so that the printing head assembly 7 can form images on a printing medium.

Specifically, the image forming apparatus 100 further includes a display screen 10, a switch button 11, and a charging port 12, the display screen 10 being provided on an outer surface of the upper cover 2 for displaying a print setting. A switch button 11 and a charging port 12 are provided to the main body 1, respectively, the switch button 11 being used to turn on or off the image forming apparatus 100, and the charging port 12 being used to plug in a cord, a data line, or the like to charge the image forming apparatus 100 or to transmit data.

It is to be understood that the above description of the specific structures of the main body, the upper cover, the connection manner thereof, and the like of the image forming apparatus is described as an example, and the image forming apparatus of the present application may have other specific structures, and the present application does not limit the above specific structures of the image forming apparatus.

To facilitate detection of the printing medium, the image forming apparatus 100 further includes a first sensor 5 and a second sensor 6. The first sensor 5 and the second sensor 6 are respectively disposed on the upper cover 2 and located in the paper feeding path 3, and detect whether a printing medium enters the paper feeding path 3 by the first sensor 5 and detect whether the printing medium is skewed by the second sensor 6.

Referring to fig. 7, fig. 7 is a schematic view of a portion of an image forming apparatus with a skew detection device according to an embodiment of the present application, in which a printing medium enters a paper feeding path in a skewed state. The paper feeding path 3 has a paper feeding end 31 and a paper discharging end 32 for conveying the paper 200, and the rubber roller 4 is disposed in the paper feeding path 3 for rolling to drive the paper 200 to move from the paper feeding end 31 to the paper discharging end 32. The first sensor 5 is disposed at the paper feeding end 31 and used for detecting whether the paper 200 enters the paper feeding channel 3, the second sensor 6 is disposed at the paper discharging end 32 and disposed at the front and rear sides of the rubber roller 4 opposite to the first sensor 5, and the second sensor 6 is rectangular, and the length thereof extends along the conveying direction of the paper 200 in the paper feeding channel 3 and is disposed close to the rubber roller 4 and used for detecting whether the paper 200 is deflected.

When detecting whether the paper 200 is deflected, the first sensor 5 detects whether the paper 200 enters the paper feeding channel 3, and when the first sensor 5 detects that the paper 200 enters the paper feeding channel 3, the rubber roller 4 drives the paper 200 to move from the paper feeding end 31 to the paper discharging end 32, so that the paper 200 is at least partially covered by the paper 200, and the second sensor 6 has a dynamic parameter which can be used for determining whether the paper 200 is deflected. Wherein the dynamic parameter is related to the condition of the second sensor 6 being covered by the sheet 200.

Generally, when the paper is skewed, the paper generally travels a certain distance in the paper feeding process to cause phenomena such as paper curling and paper jam, and the paper has little influence on the paper state within a short distance just after the paper enters the rubber roller 4. Because the speed of the rubber roller 4 is controllable and does not depend on human, the application utilizes a controllable distance at one side of the rubber roller 4 close to the paper outlet end 32 to detect the deflection condition of the paper 200, so as to avoid the interference of human environment and improve the detection precision.

In order to control the movement of the rubber roller 4, the image forming apparatus 100 further includes a controller, the controller is connected to the first sensor 5, the second sensor 6 and the rubber roller 4, respectively, and the controller is configured to control the movement of the rubber roller 4 according to a detection result of the first sensor 5 and determine whether the printing medium is skewed according to a dynamic parameter of the second sensor 6.

Specifically, when the paper enters the paper feeding end 31 and the first sensor 5 detects the paper, the controller acquires the information, controls the rubber roller 4 to rotate to suck the paper, and simultaneously controls the rotating speed of the rubber roller 4 to enable the paper to slowly cover the second sensor 6, so that the second sensor 6 has dynamic parameters, and the controller determines whether the paper is skewed or not according to the dynamic parameters. The dynamic parameter may be a time parameter, a voltage parameter, a current parameter, or the like, for example, the dynamic parameter may be a time parameter required for the second sensor 6 to be partially or completely covered by the printing medium, the voltage parameter may be a voltage variation parameter when the second sensor 6 is partially or completely covered by the printing medium, and the current parameter may be a current variation parameter when the second sensor 6 is partially or completely covered by the printing medium.

Further, when the dynamic parameter is a time parameter, the controller calculates a preset time parameter (the preset time parameter may also be calculated in advance and stored in the memory, preferably in a storage and storage manner to save time) required for the second sensor 6 to be completely covered by the printing medium according to the length of the second sensor 6 and the speed of the rubber roller 4, detects an actual time parameter required for the second sensor 6 to be completely covered by the printing medium, compares the actual time parameter with the preset time parameter, and determines whether the printing medium is skewed according to a comparison result. When the dynamic parameter is a voltage parameter, a preset voltage change parameter within a preset time is set, an actual voltage change parameter of the second sensor 6 within the preset time is detected, the actual voltage change parameter is compared with the preset voltage change parameter, and whether the printing medium deflects or not is determined according to a comparison result. When the dynamic parameter is a current parameter, a preset current change parameter within a preset time is set, an actual current change parameter of the second sensor 6 within the preset time is detected, the actual current change parameter is compared with the preset current change parameter, and whether the printing medium deflects or not is determined according to a comparison result. For example, when the dynamic parameter is a time parameter, the time when the controller detects that the second sensor 6 is just covered by the paper is t1, the time when the second sensor is completely covered by the paper is t2, if the detection length of the second sensor 6 is L, the rotation speed of the glue roller 4 is v1, if the paper is not skewed, the time Δ t required for the second sensor 6 to be completely covered by the paper is Δ t — L/v1 — t2-t1, and the time Δ t is a preset time parameter. If the paper is skewed, t2-t1 >. DELTA.t, therefore, the actual time parameter required for the second sensor 6 to be completely covered with the paper can be compared with the preset time parameter, and whether the paper is skewed or not can be determined according to the comparison result.

The dynamic parameter is a voltage parameter, when the second sensor 6 is not covered with the sheet, the voltage of the second sensor 6 is 0V, when the second sensor 6 is just covered with the sheet, the voltage of the second sensor 6 is 0.02V, when the sheet is not skewed, the voltage of the second sensor 6 changes by 0.2V every time t passes, and when the time t passes, the second sensor 6 is completely covered with the sheet, and the voltage of the second sensor 6 is 1.02V. When the paper enters the second sensor 6, the voltage of the second sensor 6 changes from 0.02V to 0.15V after the first t time, which indicates that the paper is skewed, or when 6 t times pass, the voltage of the second sensor 6 reaches the standard value of 1.02V, which also indicates that the paper is skewed. When the dynamic parameter is a current parameter, the paper skew determination method is similar to the voltage parameter determination method, and will not be described in detail here.

If the paper is judged to be inclined, the controller controls the rubber roller 4 to rotate reversely, so that the paper exits the rubber roller 4, and at least one of actions of prompting a user, giving an alarm, stopping printing and the like is executed, so that the imaging device 100 does not perform the next printing. If the paper is judged not to be deflected, the controller controls the rubber roller 4 to rotate reversely, so that the paper exits the rubber roller 4 and returns to the printing starting position, and normal printing is performed.

Meanwhile, the second sensor 6 is also used for detecting whether the paper is completely output, if the paper is completely output, the controller controls the next paper to be printed or the next paper to be ready to be printed, and if the printing operation is completed and the second sensor 6 detects that the paper is completely output, the controller controls the rubber roller 4 to stop rotating, the printing component to stop printing or stop informing a user of actions and the like.

Referring to fig. 8 and 9, fig. 8 is a schematic view illustrating that a printing medium provided in an embodiment of the present application enters an image forming apparatus in a normal state, and fig. 9 is a schematic view illustrating that a printing medium provided in an embodiment of the present application enters an image forming apparatus in an inclined state. When the sheet is not inclined, the second sensor 6 is completely covered with the sheet at the time parameter t4 or the voltage parameter V4. When the paper inclines, the second sensor 6 can be completely covered by the paper when the time parameter is t6 or the voltage parameter is V6, and the inclination angle of the paper is calculated through comparison according to the difference of the time when the second sensor 6 is completely covered by the paper through preset setting. Further, under the same rotating speed of the rubber roller 4, when the paper is in an inclined state and a non-inclined state, the areas of the paper covering the second sensor 6 in the same preset time are different, therefore, in the preset time, the voltage of the second sensor 6 when the paper is inclined is smaller than the voltage of the second sensor 6 when the paper is not inclined, through presetting, the areas of the paper covering the second sensor 6 in the same time correspond to different voltages, and the inclination angle of the paper at the moment can be obtained through comparison and calculation. The allowable inclination angle may be a range that allows how much inclination amount of the sheet is, which does not substantially affect normal printing of the sheet, compared with the time when the sheet completely covers the second sensor 6 as in the case where the standard does not incline; it is also possible that the voltage corresponding to covering the second sensor 6 at the same time may be a range that allows how much the sheet is inclined, compared to the voltage in the case where the standard does not incline, the amount of inclination not substantially affecting the normal printing of the sheet.

The paper deflection detection mode has the advantages that no human intervention exists, the speed, the precision and the accuracy are controllable, the paper deflection detection mode is not only suitable for common printers, but also suitable for portable and small printers with shorter paper feed channels 3, and in addition, the paper deflection detection mode has the advantages that only two sensors are used, the structure is simple, and the cost is low. The second sensor 6 can be used not only to detect the skew condition of the paper, but also to detect whether the paper has been printed.

The dynamic parameter is a time parameter, a voltage parameter or a current parameter, a voltage value is merely an example, and in other embodiments, the voltage value may be other specific values. The larger the sensor precision is, the more accurate the judgment of the paper inclination angle is, and a proper sensor is selected according to the comprehensive examination and filtration of specific application scenes, requirements, cost and the like.

In order to prevent the amount of paper skew from being too large, the image forming apparatus 100 further includes shutters 13, the shutters 13 being disposed at opposite sides of the paper feed end 31 for blocking the printing medium to prevent the printing medium from being skewed too much.

Based on the above embodiment, the present application further discloses another specific implementation manner, and referring to fig. 10, fig. 10 is a schematic partial structural diagram of an image forming apparatus provided in another embodiment of the present application, and the present embodiment is different from the above embodiment in that in the present embodiment, two first sensors 5 are disposed, and the two first sensors 5 are distributed on two sides of the paper feeding end 31 along the width extending direction of the paper feeding channel 3. The present embodiment is provided with the first sensors 5 on both sides of the paper feeding end 31, so that when the paper enters the paper feeding path 3, the first sensor 5 can detect the paper at the first time regardless of which side the paper is inclined, to accelerate the detection speed of the skew of the printing medium. In addition, when the paper on the side without the first sensor 5 is closer to the rubber roller 4, the change of the paper state, such as curling and paper jam, caused by the fact that the paper is taken out by the rubber roller 4 for a long distance to cover the second sensor 6 can be avoided. In some embodiments, the second sensor 6 may also be disposed on a certain side, or may be disposed in the middle.

The first sensor 5 may be any touch sensor, such as a dot sensor, and the first sensor 5 detects a signal only when a sheet enters a detection point of the first sensor 5, because the first sensor 5 is only used to determine the presence or absence of the sheet. The second sensor 6 is a linear sensor, i.e. the effective area to be detected can detect signals, and the controller judges whether the paper inclines or not by judging the analog variation (voltage and current variation parameters) of the sensor. Common paper detection sensors include reflection type photosensors (for example, ITR20001, ITR8307-F43, ZGR9908, and the like), and correlation type photosensors (for example, ITR1100, ITR9608, and the like). The first sensor 5 of the present application may be an ITR8307-F43, and the second sensor 6 may be a ZGR 9908.

The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An image forming apparatus, characterized by comprising:

the first sensor is arranged at the paper feeding end;

the second sensor is arranged at the paper outlet end;

2. The image forming apparatus according to claim 1, further comprising a controller connected to the first sensor, the second sensor, and the blanket, respectively, the controller for controlling movement of the blanket according to a detection result of the first sensor and for determining whether the printing medium is skewed according to a dynamic parameter of the second sensor.

3. The imaging apparatus of claim 2, wherein the controller is specifically configured to determine whether the print medium is skewed based on a time parameter required for the second sensor to be partially or fully covered by the print medium.

4. The apparatus of claim 2, wherein the controller is configured to detect an actual time parameter required for the second sensor to be completely covered by the printing medium, compare the actual time parameter with a preset time parameter, and determine whether the printing medium is skewed according to a comparison result.

5. The imaging apparatus of claim 4, wherein the preset time parameter is calculated from a length of the second sensor and a rotational speed of the rubber roller.

6. The imaging apparatus of claim 2, wherein the controller is specifically configured to determine whether the print medium is skewed based on a voltage parameter of the second sensor, wherein the voltage parameter of the second sensor is related to a condition of the second sensor being covered by the print medium.

7. The apparatus of claim 6, wherein the controller is configured to detect a voltage variation parameter of the second sensor for a predetermined time, compare the voltage variation parameter with a predetermined voltage parameter, and determine whether the printing medium is skewed according to the comparison result.

8. The imaging apparatus of claim 2, wherein the controller is specifically configured to determine whether the print medium is skewed based on a current parameter of the second sensor, wherein the current parameter of the second sensor is related to a condition of the second sensor being covered by the print medium.

9. The apparatus of claim 8, wherein the controller is configured to compare the current variation parameter with a preset current parameter according to a current variation parameter of the second sensor within a preset time, and determine whether the printing medium is skewed according to a comparison result.

10. The image forming apparatus as claimed in any one of claims 1 to 9, wherein a length of the second sensor extends along a conveying direction of the printing medium in the sheet feeding path.

11. The image forming apparatus as claimed in any one of claims 1 to 9, wherein there are two first sensors arranged along a widthwise extending direction of said sheet feeding path and on opposite sides of said sheet feeding end.

12. The image forming apparatus according to any one of claims 2 to 9, wherein when it is determined that the printing medium is skewed, the controller controls the blanket roller to rotate in a reverse direction, so that the printing medium exits the blanket roller, and performs at least one of a user prompt, an alarm, and a stop of printing.

13. The image forming apparatus as claimed in any one of claims 2 to 9, wherein when it is determined that the printing medium is not skewed, the controller controls the blanket roller to rotate in a reverse direction so that the printing medium is retreated to a printing start position of the paper feeding end and printing is performed.

14. The image forming apparatus as claimed in any one of claims 2 to 9, wherein the second sensor is further configured to detect whether the printing medium is completely discharged.