Digital Inkjet Printer and Printing Control Method

Abstract

The present invention discloses a digital inkjet printer and a printing control method. The digital inkjet printer includes a paper feeding mechanism and a paper receiving mechanism, a printing cylinder is arranged between the paper feeding mechanism and the paper receiving mechanism, and a nozzle assembly is arranged above the printing cylinder; the printing cylinder is a non-jaw type suction drum, and a turning mechanism is arranged in cooperation with the printing cylinder, and the turning mechanism also serves as a paper output mechanism; the turning mechanism includes a paper lifting suction wheel, a paper returning suction wheel, a paper temporary storage assembly and a detection sensor. This digital inkjet printer only needs one non-jaw type suction drum as the printing cylinder, the overall structure design is simple, and accurate paper transfer can be realized without a paper gripper row. The turning mechanism has a simple design, a short transfer path, good turning smoothness, and is beneficial to improving the printing efficiency. The turning mechanism also serves as a paper output mechanism, realizing the multi-functional utilization of the turning mechanism, simplifying the overall structure of the machine, and reducing the manufacturing cost.

Description

Technical Field

[0001] The invention belongs to the technical field of inkjet printing machinery, and in particular relates to a digital inkjet printer and a printing control method. Background Art

[0002] Sheet-fed digital inkjet printing machinery can realize single-sided printing or double-sided printing of single-sheet paper according to customer printing requirements. The sheet-fed inkjet printing process requires high paper positioning accuracy.

[0003] In the prior art, most single-sheet digital inkjet printers use rollers to carry and transfer paper. The paper is transferred between units by the printing roller, the paper transfer roller or the gripper row on the conveyor chain. The printing roller is used to carry the paper to complete the printing operation. An inkjet head is arranged above the printing roller. When the paper rotates with the printing roller to the bottom of the inkjet head, the inkjet head prints the paper. Although the roller with the gripper row has high positioning accuracy for the paper, its manufacturing cost is also high, and the failure rate of the gripper row is also high.

[0004] After the front side of the paper is printed, the paper needs to be turned over by a flipping mechanism to convert the head of the paper into the tail of the paper before being fed into the printing roller for reverse printing. Currently, there are two main flipping mechanisms for digital inkjet printers: one is to use a paper swinging mechanism with a paper gripper row in conjunction with a roller or chain transmission mechanism to achieve the conversion between the head and the tail of the paper. This flipping method has a more complex structural design, and the paper is prone to wrinkles when swinging the paper. The paper is not turned over smoothly, and the failure rate is higher. The other is an adsorption-type turning mechanism, which includes a suction belt, which is wound around two suction wheels that can rotate forward and backward. When the suction wheel drives the suction belt to rotate forward, the suction belt adsorbs the head side of the paper on the roller to temporarily store the paper. When the suction wheel drives the suction belt to reverse, the temporarily stored paper is re-transferred from the tail side of the paper to the paper feed belt to realize paper turning. The paper feed belt then feeds the turned paper back to the printing roller for reverse printing. Although this turning method simplifies the structure and has good smoothness in paper turning, after the suction belt rotates forward to temporarily store the paper, when it reverses to transmit the paper, it needs to pass through the paper feed belt to transmit the paper back to the printing roller. The paper transmission path is long, which affects the printing efficiency.

[0005] In addition, the turning mechanism is usually a single-function component, which can only realize the function of turning over the paper, but cannot realize the output of the paper after printing, resulting in complex structural design and high manufacturing cost of the existing inkjet printer. Summary of the invention

[0006] Aiming at the above deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a digital inkjet printer with a simple structure design, which can achieve accurate paper transfer without a gripper bar, has a short paper transfer path, good smoothness in paper turning, and the turning mechanism can also serve as a paper output mechanism at the same time.

[0007] To solve the above technical problems, the technical solution of the present invention is: a digital inkjet printer, including a paper feeding mechanism and a paper receiving mechanism, with an inkjet drum arranged between the paper feeding mechanism and the paper receiving mechanism, and a nozzle assembly arranged above the inkjet drum; the inkjet drum is a suction drum without grippers, and the inkjet drum has a paper release area and a paper adsorption area, the paper adsorption area is a constant negative pressure area, and the paper release area is a non-negative pressure area; the inkjet drum is cooperatively provided with a turning mechanism, and the turning mechanism also serves as a paper output mechanism;

[0008] The turning mechanism includes a paper lifting suction wheel, a paper returning suction wheel, a paper temporary storage assembly and a detection sensor; the paper lifting suction wheel is rotatably arranged outside the paper release area of the inkjet drum, the paper lifting suction wheel is provided with a paper lifting adsorption area, and the paper lifting adsorption area is an instantaneous negative pressure area; the paper returning suction wheel is rotatably arranged outside the paper adsorption area of the inkjet drum, the paper returning suction wheel is provided with a paper feeding adsorption area, and the paper feeding adsorption area is also an instantaneous negative pressure area; the paper temporary storage assembly is arranged between the paper lifting suction wheel and the paper returning suction wheel, and the tail end of the paper temporary storage assembly is connected with the paper receiving mechanism; the detection sensor is arranged at the tail of the paper temporary storage assembly.

[0009] As a preferred technical solution, the inkjet drum includes a drum body, the surface of the drum body is provided with more than two rows of air holes, air ducts are respectively arranged in the drum body corresponding to each row of air holes, and the air ducts are communicated with the corresponding air holes; the end of the drum body is cooperatively provided with a first conduction part, the drum body and the first conduction part can rotate relatively, and a paper feeding side strong adsorption area, a paper feeding side holding adsorption area, a turning side strong adsorption area and a turning side holding adsorption area are sequentially formed in the first conduction part along the rotation direction of the drum body; when the drum body rotates, each air duct is respectively communicated with the corresponding area when passing through each area in sequence.

[0010] As a preferred technical solution, the negative pressure of the paper feeding side strong adsorption area and the turning side strong adsorption area is greater than the negative pressure of the paper feeding side holding adsorption area and the turning side holding adsorption area.

[0011] As a preferred technical solution, the coverage areas of the paper feeding side strong adsorption area and the turning side strong adsorption area can respectively only cover one air duct.

[0012] As a preferred technical solution, the coverage areas of the paper feeding side holding adsorption area and the turning side holding adsorption area can respectively cover at least two air ducts.

[0013] As a preferred technical solution, a retractable stop pin is provided between the paper temporary storage assembly and the paper receiving mechanism.

[0014] As a preferred technical solution, the paper lifting suction wheel includes a wheel body. Two or more rows of air holes are formed on the surface of the wheel body. Air ducts are respectively arranged in the wheel body corresponding to the respective air exhaust holes, and the air ducts are communicated with the corresponding air holes. A second conducting member is cooperatively arranged at the end of the wheel body. The wheel body and the second conducting member can rotate relative to each other. The second conducting member is connected to a negative pressure device through a pipeline, and an electromagnetic control valve is installed on the pipeline.

[0015] The present invention also provides a printing control method for the digital inkjet printer described above:

[0016] During single-sided printing, the paper feeding mechanism conveys the paper to the printing drum. When the paper head of the paper passes through the strong adsorption area on the paper feeding side, it is instantaneously adsorbed on the drum surface and accurately positioned. When the paper is adsorbed on the printing drum and rotates with the drum to the lower part of the nozzle assembly, the nozzle assembly performs single-sided printing on the paper. When the paper after single-sided printing rotates with the drum to the paper release area, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts the paper to the paper temporary storage assembly. The paper temporary storage assembly conveys the paper to the paper receiving mechanism.

[0017] During double-sided printing, first, front-side printing is performed. The paper feeding mechanism conveys the paper to the printing drum. When the paper head of the paper passes through the strong adsorption area on the paper feeding side, it is instantaneously adsorbed on the drum surface and accurately positioned. When the paper is adsorbed on the printing drum and rotates with the drum to the lower part of the nozzle assembly, the nozzle assembly performs front-side printing on the paper. When the paper after front-side printing rotates with the drum to the paper release area, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts the paper to the paper temporary storage assembly for temporary storage. When the detection sensor detects that the paper head reaches the set position, the paper lifting adsorption area of the paper lifting suction wheel instantaneously disconnects the negative pressure, and at the same time, the paper feeding adsorption area of the paper returning suction wheel instantaneously accesses negative pressure. The paper returning suction wheel instantaneously adsorbs the paper tail and conveys the paper to the paper adsorption area of the printing drum. The paper is re-adsorbed on the drum surface, and thus the paper tail is converted into the paper head to complete the turning over. When the paper continues to be adsorbed on the printing drum and rotates with the drum to the lower part of the nozzle assembly again, the nozzle assembly performs back-side printing on the paper. When the paper after positive and negative double-sided printing rotates with the drum to the paper release area again, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts the paper to the paper temporary storage assembly. The paper temporary storage assembly conveys the paper to the paper receiving mechanism.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] (1) The whole device only needs one gripper-free suction roller as the printing roller. The printing roller has a paper release area and a paper adsorption area. When the head of a single sheet of paper reaches the paper adsorption area, the head of the paper is adsorbed by a large negative pressure and is instantly adsorbed to the surface of the roller and accurately positioned, playing the role of the gripper handover. When the head of the printed paper rotates with the roller to the turning mechanism, the paper lifting suction wheel instantly adsorbs the paper and lifts the paper to the paper temporary storage component. According to the needs of single-sided printing or double-sided printing, the paper temporary storage component transfers the paper to the paper collection mechanism or the paper return suction wheel turns the paper over and re-transmits it to the printing roller surface. The overall structural design is simple, and accurate paper handover and delivery can be achieved without a gripper row.

[0020] (2) The flipping mechanism includes a paper lifting suction wheel, a paper returning suction wheel, a paper temporary storage component and a detection sensor; when the paper head adsorbed on the surface of the printing roller rotates with the roller to the paper release area, the paper lifting suction area of the paper lifting suction wheel is instantly connected to negative pressure, the paper lifting suction wheel instantly adsorbs the paper and lifts the paper to the paper temporary storage component for temporary storage; when the paper head reaches the set position, the paper lifting suction area of the paper lifting suction wheel is instantly disconnected from the negative pressure, and at the same time, the paper feeding suction area of the paper returning suction wheel is instantly connected to negative pressure, the paper returning suction wheel instantly adsorbs the paper tail and transfers the paper to the paper adsorption area of the printing roller, the paper is adsorbed to the surface of the printing roller again, and the paper tail is converted to the paper head to complete the flipping. In this way, only two suction wheels are used in conjunction with the opening and closing of the electromagnetic control valve to realize the conversion and flipping of the paper from the paper tail to the paper head. The structural design is simple and the manufacturing cost is low. During the flipping process, the paper has a short transmission path from the beginning of leaving the printing roller to returning to the printing roller, and the flipping is smooth, which is conducive to improving printing efficiency.

[0021] (3) The flipping mechanism also serves as a paper output mechanism, which realizes the multifunctional use of the flipping mechanism, simplifies the overall structure of the machine, and reduces the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following drawings are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0023] Figure 1 is a structural schematic diagram of a digital inkjet printer provided by an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the cooperation between the printing roller and the turning mechanism in the embodiment of the present invention;

[0025] Figure 3 1 is a schematic side view of the structure of the printing roller in an embodiment of the present invention;

[0026] Figure 4 yes Figure 3 Schematic diagram of the cross section along the AA direction;

[0027] Figure 5 is the front view structural schematic diagram of the paper lifting suction wheel in the embodiment of the present invention;

[0028] Figure 6 is the side view structural schematic diagram of the paper lifting suction wheel in the embodiment of the present invention;

[0029] Figure 7 is the paper running direction diagram during single-sided printing;

[0030] Figure 8 is the state reference diagram when the paper lifting suction wheel lifts the paper from the surface of the printing cylinder to the paper temporary storage assembly during double-sided printing;

[0031] Figure 9 is the state reference diagram when the paper return suction wheel instantaneously adsorbs the tail of the paper and is ready to transfer the paper to the paper adsorption area of the printing cylinder;

[0032] Figure 10 is the state reference diagram when the paper is re-adsorbed onto the surface of the printing cylinder and the tail of the paper is converted into the head of the paper to complete the turning over. Specific Embodiments

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. In the following detailed description, only some exemplary embodiments of the present invention are described by way of illustration. Without a doubt, those of ordinary skill in the art can recognize that various different ways can be used to modify the described embodiments without departing from the spirit and scope of the present invention. Therefore, the accompanying drawings and the description are illustrative in nature and are not used to limit the protection scope of the claims.

[0034] As Figure 1 shown, the digital inkjet printer includes a paper feeding mechanism 10 and a paper receiving mechanism 20. A printing cylinder 30 is provided between the paper feeding mechanism 10 and the paper receiving mechanism 20. A nozzle assembly 40 is provided above the printing cylinder 30. The nozzle assembly 40 is used to print on the paper that rotates to this position along with the cylinder. The paper feeding mechanism 10, the paper receiving mechanism 20, and the nozzle assembly 40 are common well-known structures in the art and will not be described in detail here. The printing cylinder 40 is cooperatively provided with a turning-over mechanism 50, and the turning-over mechanism 50 also serves as a paper output mechanism.

[0035] Referring to Figure 2 , the printing cylinder 30 is a toothless suction cylinder. The printing cylinder 30 has a paper release area 31 and a paper adsorption area 32. The paper adsorption area 32 is a constant negative pressure area, and the paper release area 31 is a non-negative pressure area (which can be normal pressure or positive pressure); Specifically, referring to Figures 2 to 4, the printing drum 30 includes a drum body 33, and more than two rows of air holes 34 are formed on the surface of the drum body 33. The air holes 34 in the same row are evenly distributed along the axial direction of the drum body 33, and the air holes 34 in different rows are annularly distributed along the circumferential surface of the drum body 33. Air ducts 35 are respectively arranged in the drum body 33 corresponding to each row of air holes 34, and the air ducts 35 are communicated with the corresponding air holes 34, and the air ducts 35 are located on the same circumferential surface;

[0036] A first conduction member 36 is cooperatively arranged at the end of the drum body 33. The drum body 33 and the first conduction member 36 can rotate relative to each other, that is, the drum body 33 is rotatably arranged, and the first conduction member 36 is fixedly arranged. A paper feeding side strong adsorption area 321, a paper feeding side holding adsorption area 322, a turning side strong adsorption area 323, and a turning side holding adsorption area 324 are sequentially formed in the first conduction member 36 along the rotation direction of the drum body 33. When the drum body 33 rotates, each air duct is communicated with the corresponding area when passing through each area in sequence. These areas together form a paper adsorption area. Of course, the setting positions of the areas can be appropriately adjusted according to the paper specifications or the handover position requirements. In this embodiment, the paper feeding side strong adsorption area 321 and the turning side strong adsorption area 323 are respectively arranged at the paper input handover position on the paper feeding side and the paper turning handover position on the other side.

[0037] Of course, to avoid air leakage, the areas on the first conduction member 36 other than the paper adsorption area are rotatably and sealingly cooperated with the end surface of the drum body 13.

[0038] Reference Figure 2 and Figure 3 , connection heads 37 corresponding to each strong adsorption area and holding adsorption area are arranged on the first conduction member 36. Through the connection heads 37, the strong adsorption area and the holding adsorption area can be respectively and independently and quickly connected to a negative pressure source. The negative pressure of the strong adsorption area is preferably greater than the negative pressure of the holding adsorption area, that is, the negative pressures of the paper feeding side strong adsorption area 321 and the turning side strong adsorption area 323 are greater than the negative pressures of the paper feeding side holding adsorption area 322 and the turning side holding adsorption area 324. Among them, the negative pressure value of the strong adsorption area is preferably 60-100 Kpa. In this way, when working, after the strong adsorption area instantaneously adsorbs and positions the paper head of the paper, the paper is held and adsorbed on the drum surface through the holding adsorption area, which can save wind energy consumption on the basis of stable and reliable transmission.

[0039] Reference Figure 2, the coverage areas of the strong adsorption area 321 on the paper feeding side and the strong adsorption area 323 on the paper turning side can only cover one air duct respectively. The coverage areas of the holding adsorption area 322 on the paper feeding side and the holding adsorption area 324 on the paper turning side can cover multiple air ducts respectively. The small coverage area of the strong adsorption area is convenient for forming an instantaneous strong adsorption force on the surface of the drum, playing the role of the gripper "bite". The paper head is subjected to a large negative pressure adsorption force and will be instantaneously adsorbed onto the surface of the drum and accurately positioned.

[0040] Reference Figure 2 , the paper turning mechanism 50 includes a paper lifting suction wheel 51, a paper returning suction wheel 52, a paper temporary storage component 53 and a detection sensor 54; the paper lifting suction wheel 51 is rotatably arranged outside the paper release area 31 of the printing drum 30, and the paper lifting suction wheel 51 is provided with a paper lifting adsorption area 511, and the paper lifting adsorption area 511 is an instantaneous negative pressure area; specifically, reference Figure 5 and Figure 6 , the paper lifting suction wheel 51 includes a wheel body 512, the surface of the wheel body 512 is provided with more than two rows of air holes, air ducts are respectively arranged in the wheel body 512 corresponding to each air exhaust hole, and the air ducts are communicated with the corresponding air holes; a second conduction member 513 is cooperatively arranged at the end of the wheel body 512, the wheel body 512 and the second conduction member 513 can rotate relatively, that is, the wheel body 512 is rotatably arranged and the second conduction member 513 is fixedly arranged; the second conduction member 513 is connected to a negative pressure device through a pipeline. When the wheel body 512 rotates, each air duct is communicated with the second conduction member 513 when passing through the second conduction member 513 to form the paper lifting adsorption area 511. An electromagnetic control valve is installed on the pipeline connecting the second conduction member 513 to the negative pressure device, and the on-off state of the negative pressure of the paper lifting adsorption area 511 can be controlled by the high-frequency opening and closing of the electromagnetic control valve.

[0041] Reference Figure 2 , the paper returning suction wheel 52 is rotatably arranged outside the strong adsorption area 323 on the paper turning side of the printing drum 30, the paper returning suction wheel 52 is provided with a paper feeding adsorption area 521, and the paper feeding adsorption area 521 is also an instantaneous negative pressure area; the paper returning suction wheel 52 has the same structural principle as the paper lifting suction wheel 51 and will not be elaborated here.

[0042] The paper temporary storage component 53 is arranged between the paper lifting suction wheel 51 and the paper returning suction wheel 52, the tail end of the paper temporary storage component 53 is connected to the paper receiving mechanism 20, and a telescopic stop pin 55 is arranged between the paper temporary storage component 53 and the paper receiving mechanism 20; the paper temporary storage component 53 is used for temporarily storing paper or conveying paper to the paper receiving mechanism 20, and it can be realized by a positive and negative rotating paper conveyor belt.

[0043] The detection sensor 54 is arranged at the tail of the paper temporary storage assembly 53 and is used to detect the position of the paper head of the paper. After single-sided printing or double-sided printing is completed, when the detection sensor 54 detects that the paper head reaches the set position, the stop pin 55 retracts, and the paper temporary storage assembly 53 rotates forward to convey the paper to the paper receiving mechanism 20; when double-sided printing requires turning over, when the detection sensor 54 detects that the paper head reaches the set position, the stop pin 55 remains extended, the paper temporary storage assembly 53 starts to rotate reversely and cooperates with the paper returning suction wheel 52 to convey the paper back to the surface of the printing drum 30 again.

[0044] The printing control method of this inkjet printer is as follows:

[0045] Reference Figure 1 and Figure 7 , during single-sided printing, the paper feeding mechanism 10 conveys the paper to the printing drum 30. When the paper head passes through the strong adsorption area 321 on the paper feeding side, it is instantaneously adsorbed to the surface of the drum and accurately positioned; when the paper is adsorbed on the printing drum 30 and rotates with the drum to the lower part of the nozzle assembly 40, the nozzle assembly 40 performs single-sided printing on the paper. When the paper after single-sided printing rotates with the drum to the paper release area 31, the paper lifting adsorption area 511 of the paper lifting suction wheel 51 instantaneously accesses negative pressure, and the paper lifting suction wheel 51 instantaneously adsorbs the paper and lifts the paper to the paper temporary storage assembly 53. When the detection sensor 54 detects that the paper head reaches the set position, the stop pin 55 retracts, and the paper temporary storage assembly 53 continues to rotate forward to convey the paper to the paper receiving mechanism 20;

[0046] Reference Figures 8 to 10When performing double-sided printing, the front side is printed first. The sheet feeding mechanism 10 conveys the paper to the inkjet printing cylinder 30. When the leading edge of the paper passes through the strong adsorption area 321 on the sheet feeding side, it is instantaneously adsorbed onto the cylinder surface and accurately positioned. When the paper is adsorbed on the inkjet printing cylinder 30 and rotates with the cylinder to the lower part of the printhead assembly 40, the printhead assembly 40 performs front-side printing on the paper. When the paper after front-side printing rotates with the cylinder to the paper release area 31, the paper adsorption area 511 of the paper lifting air suction wheel 51 instantaneously accesses negative pressure, and the paper lifting air suction wheel 51 instantaneously adsorbs the paper and lifts it to the paper temporary storage assembly 53 for temporary storage. When the detection sensor 54 detects that the leading edge of the paper reaches the set position, the retaining pin 55 remains in the extended state, the paper adsorption area 511 of the paper lifting air suction wheel 51 instantaneously disconnects the negative pressure, and at the same time, the paper feeding adsorption area 521 of the paper returning air suction wheel 52 instantaneously accesses negative pressure. The paper temporary storage assembly 53 starts to rotate in reverse, and the paper returning air suction wheel 52 instantaneously adsorbs the trailing edge of the paper and conveys the paper to the strong adsorption area 323 on the reverse side of the inkjet printing cylinder 30. The paper is re-adsorbed onto the cylinder surface, and thus the trailing edge is converted into the leading edge to complete the turning over. When the paper continues to be adsorbed on the inkjet printing cylinder and rotates with the cylinder to the lower part of the printhead assembly 40 again, the printhead assembly 40 performs back-side printing on the paper. When the paper after double-sided printing rotates with the cylinder to the paper release area 31 again, the paper adsorption area 511 of the paper lifting air suction wheel 51 instantaneously accesses negative pressure, and the paper lifting air suction wheel 51 instantaneously adsorbs the paper and lifts it to the paper temporary storage assembly 53. The paper temporary storage assembly 53 conveys the paper to the sheet receiving mechanism.

[0047] In the whole set of devices of the present invention, only one air suction cylinder without grippers is required as the inkjet printing cylinder, and the overall structural design is simple. Without a sheet gripper row, accurate transfer of the paper can be achieved. Only by using two air suction wheels in cooperation with the opening and closing of the electromagnetic control valve can the conversion and turning over of the paper from the trailing edge to the leading edge be realized. The structural design is simple, the manufacturing cost is low, and during the turning over process, the transfer path of the paper from starting to separate from the inkjet printing cylinder to returning to the inkjet printing cylinder is short, and the turning over smoothness is good, which is beneficial to improving the printing efficiency. The turning over mechanism also serves as the paper output mechanism, realizing the multi-functional utilization of the turning over mechanism, simplifying the overall machine structure, and reducing the manufacturing cost. This model has broad market prospects.

[0048] The above are only the schematic specific embodiments of the present invention and are not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention shall fall within the scope of protection of the present invention.

Claims

1. Digital inkjet printer, comprising a paper feeding mechanism and a paper receiving mechanism, with an inkjet cylinder disposed between the paper feeding mechanism and the paper receiving mechanism, and a nozzle assembly disposed above the inkjet cylinder; characterized in that: The printing cylinder is a toothless suction cylinder, and the printing cylinder has a paper release area and a paper adsorption area. The paper adsorption area is a constant negative pressure area, and the paper release area is a non-negative pressure area. The printing cylinder is provided with a turning mechanism, and the turning mechanism also serves as a paper output mechanism. The turning mechanism includes a paper lifting suction wheel, a paper returning suction wheel, a paper temporary storage assembly and a detection sensor. The paper lifting suction wheel is rotatably arranged outside the paper release area of the printing cylinder. The paper lifting suction wheel is provided with a paper lifting adsorption area, and the paper lifting adsorption area is an instantaneous negative pressure area. The paper returning suction wheel is rotatably arranged outside the paper adsorption area of the printing cylinder. The paper returning suction wheel is provided with a paper feeding adsorption area, and the paper feeding adsorption area is also an instantaneous negative pressure area. The paper temporary storage assembly is arranged between the paper lifting suction wheel and the paper returning suction wheel, and the tail end of the paper temporary storage assembly is connected to the paper receiving mechanism. The detection sensor is arranged at the tail of the paper temporary storage assembly. The printing cylinder includes a cylinder body. The surface of the cylinder body is provided with more than two rows of air holes. Corresponding to each air exhaust hole in the cylinder body, there is an air duct, and the air duct is communicated with the corresponding air hole. The end of the cylinder body is provided with a first conduction member in a matching manner. The cylinder body and the first conduction member can rotate relatively. Along the rotation direction of the cylinder body in the first conduction member, there are successively formed a paper feeding side strong adsorption area, a paper feeding side holding adsorption area, a turning side strong adsorption area and a turning side holding adsorption area. When the cylinder body rotates, each air duct is successively communicated with the corresponding area when passing through each area.

2. The digital inkjet printer according to claim 1, wherein: The negative pressure in the paper feeding side strong adsorption area and the turning side strong adsorption area is greater than the negative pressure in the paper feeding side holding adsorption area and the turning side holding adsorption area.

3. The digital inkjet printer according to claim 1, wherein: The covering areas of the paper feeding side strong adsorption area and the turning side strong adsorption area can respectively only cover one air duct.

4. The digital inkjet printer according to claim 1, wherein: The covering areas of the paper feeding side holding adsorption area and the turning side holding adsorption area can respectively cover at least two air ducts.

5. The digital inkjet printer according to claim 1, wherein: A telescopic stop pin is arranged between the paper temporary storage assembly and the paper receiving mechanism.

6. The digital inkjet printer according to any one of claims 1 to 5, characterized in that: The paper lifting suction wheel includes a wheel body. The surface of the wheel body is provided with more than two rows of air holes. Corresponding to each air exhaust hole in the wheel body, there is an air duct, and the air duct is communicated with the corresponding air hole. The end of the wheel body is provided with a second conduction member in a matching manner. The wheel body and the second conduction member can rotate relatively. The second conduction member is connected to a negative pressure device through a pipeline, and an electromagnetic control valve is installed on the pipeline.

7. The printing control method of the digital inkjet printer according to claim 1, characterized in that: During single-sided printing, the paper feeding mechanism transports the paper to the printing cylinder. When the paper head of the paper passes through the paper feeding side strong adsorption area, it is instantaneously adsorbed to the surface of the cylinder and accurately positioned. When the paper is adsorbed on the printing cylinder and rotates with the cylinder to the lower part of the nozzle assembly, the nozzle assembly performs single-sided printing on the paper. When the paper after single-sided printing rotates with the cylinder to the paper release area, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts the paper to the paper temporary storage assembly. The paper temporary storage assembly transports the paper to the paper receiving mechanism. During double-sided printing, the front printing is carried out first. The paper feeding mechanism conveys the paper to the inkjet printing drum. When the leading edge of the paper passes through the strong adsorption area on the paper feeding side, it is instantaneously adsorbed onto the drum surface and accurately positioned. When the paper is adsorbed on the inkjet printing drum and rotates with the drum to the position below the nozzle assembly, the nozzle assembly performs front printing on the paper. When the paper after front printing rotates with the drum to the paper release area, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts it to the paper temporary storage assembly for temporary storage. When the detection sensor detects that the leading edge of the paper reaches the set position, the paper lifting adsorption area of the paper lifting suction wheel instantaneously disconnects the negative pressure, and at the same time, the paper feeding adsorption area of the paper returning suction wheel instantaneously accesses negative pressure. The paper returning suction wheel instantaneously adsorbs the trailing edge of the paper and conveys the paper to the paper adsorption area of the inkjet printing drum. The paper is re-adsorbed onto the drum surface, and thus the trailing edge is converted into the leading edge to complete the turning over. When the paper continues to be adsorbed on the inkjet printing drum and rotates with the drum again to the position below the nozzle assembly, the nozzle assembly performs back printing on the paper. When the paper after double-sided printing rotates with the drum again to the paper release area, the paper lifting adsorption area of the paper lifting suction wheel instantaneously accesses negative pressure, and the paper lifting suction wheel instantaneously adsorbs the paper and lifts it to the paper temporary storage assembly. The paper temporary storage assembly conveys the paper to the paper receiving mechanism.

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