JPH05309924A - Device for detecting leading end of paper - Google Patents

Abstract

PURPOSE:To certainly start recording from a predetermined position by providing a temp. control means keeping the temp. of a support member constant and a means detecting the leading end of paper on the basis of the change of the signal from the temp. control means of the support member. CONSTITUTION:Since recording paper takes the heat of a platen when it reaches the platen, the temp. of the platen lowers to the tolerance value or more stored in an ROM within a unit time. Therefore, the temp. measured in a step S13 is compared with the previous measured temp. stored in an RAM and, when the difference between both temps. exceeds to tolerance value stored in the ROM, a CPU judges that the recording paper reaches the platen (S14) and drives a fan motor to bring the recording paper into close contact with the platen by a fan through a suction hole (S1). Subsequently, an ink jet head is moved in the recording direction vertical to a paper feed direction by a carriage motor to perform recording operation on the recording paper to execute recording processing of one page (S16).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet leading edge detecting device.

[0002]

2. Description of the Related Art Conventionally, there is a hot-melt type ink jet recording apparatus using this paper leading edge detecting apparatus. Particularly, in a hot-melt ink jet recording apparatus that records on a recording sheet using a heat-meltable ink that is solid at room temperature and melts when heated, the platen is heated to raise the temperature of the recording sheet. Some prints improve the print quality by recording on paper.

That is, as shown in FIG. 6, the hot-melt type ink jet recording apparatus records on the recording paper 106 by ejecting the melted ink from the recording head 102 onto the recording paper 106 on the platen 104. is there. Carriage 108 equipped with this recording head 102
Is supported by two guide shafts 110 and is arranged so as to be moved in a direction perpendicular to the conveying direction of the recording paper 106 by driving a carriage motor (not shown).

A heater 120 for heating the platen 104, which is disposed so as to face the recording head 102, is attached to the platen 104.
The print quality is improved by raising the temperature and recording. A thermistor 122 is attached to the platen 104, and the temperature of the platen 104 is detected by the thermistor 122 so that the heating temperature of the heater 120 is maintained constant.

Further, a paper leading edge detection sensor 130 is attached in the vicinity of the upstream side of the platen 104 in the conveyance path of the recording paper 106 and at a position far from the platen 104 to the extent that the heat generated by the platen 104 is not affected. The leading edge of the recording paper 106 conveyed by the paper feed roller 114 from the paper feed cassette 112 is detected.

In the hot-melt type ink jet recording apparatus having the above-mentioned structure, the recording sheet fed by the sheet feeding roller 114 from the sheet feeding cassette 112 arranged upstream of the recording head 102 in the conveying path of the recording sheet 106. 106 is a drive roller 116 and a nip roller 118.
Is conveyed to the sheet leading edge detection sensor 130 portion.
Then, the recording paper 106 is detected by the paper leading edge detection sensor 130.
When the leading edge of the recording sheet 106 is detected, the driving roller 116 is rotated by a predetermined amount, so that the leading edge of the recording sheet 106 is moved to the platen 1.
Then, the recording head 102 starts printing on the recording paper 106. Also, recording sheet 1
No. 06 is heated and heated by the platen 104 at the time of printing, whereby the ink ejected from the recording head 102 is well fixed on the recording paper 106, and the printing quality is improved. 1
The recording paper 106 on which printing of pages has been completed is driven by the drive roller 116 and the nip roller 118 to eject the recording paper 106.
9 is ejected onto the sheet.

[0007]

However, in the conventional hot-melt type ink jet recording apparatus as described above, the paper leading edge detecting sensor 130 is provided on the paper carrying passage.
There is a distance between the platen 104 and the platen 104. Therefore, after the sheet leading edge detection sensor 130 detects the leading edge of the recording sheet 106, the driving roller 116 and the nip roller 118 are rotated by a predetermined amount so that the recording sheet reaches the position of the platen 104. Since printing was started as being transported,
There is a problem that normal printing cannot be performed unless the recording sheet 106 can be reliably conveyed onto the platen 104 due to the influence of slip between the driving roller 116 and the recording sheet 106 when the recording sheet 106 is conveyed.

Although the above-mentioned problem can be solved by providing the paper leading edge detection sensor 130 in the vicinity of the platen 104, in the hot melt ink jet recording apparatus, the platen 104 is kept at a high temperature by the heater 120. Therefore, the possibility of malfunction or malfunction of the paper leading edge detection sensor 130 due to heat increases, which is difficult.

The present invention has been made to solve the above-mentioned problems, and it is possible to reliably start recording from a predetermined sheet position with the detection of the leading edge of the sheet without increasing the number of parts. An object is to provide a tip detection device.

[0010]

In order to achieve this object, a sheet leading edge detecting apparatus of the present invention comprises a supporting member for supporting a sheet at the time of printing, a heating means for heating the supporting member,
The temperature detection means for detecting the temperature of the support member, the temperature control means for keeping the temperature of the support member constant by the signal of the temperature detection means, and the change of the signal of the detected temperature means causes the leading edge of the sheet. And a paper leading edge detecting means for detecting.

[0011]

In the sheet leading edge detecting device of the present invention having the above-mentioned structure, the supporting member for supporting the sheet at the time of printing is heated by the heating means, and the temperature controlling means operates the temperature of the supporting member based on the signal from the temperature detecting means. Keep the temperature constant. Then, the sheet leading edge detecting means detects the sheet leading edge in accordance with the change in the temperature of the supporting member when the sheet comes into contact with the supporting member.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
This will be described with reference to FIG.

Hot melt ink jet recording apparatus 1
0 is for recording on the recording paper 16 by ejecting the melted ink from the inkjet head 12 onto the recording paper 16 supported on the platen 14 as a supporting member. That is, the inkjet head 12
Applies a voltage to a piezoelectric element (not shown) arranged on the wall surface of a nozzle (not shown) filled with ink, deforms the piezoelectric element to press the ink in the nozzle, and the pressure is applied. The ink is ejected to the outside of the inkjet head 12 and attached to the recording paper 16.

The carriage 18 carrying the ink jet head 12 is supported by two guide shafts 20 and is arranged so as to be reciprocally moved along the platen 14 via the timing belt 24 by the drive of the carriage motor 22. There is.

A heater 26 is attached to the platen 14 arranged at a position facing the ink jet head 12, and the platen 14 has a thermistor as a temperature detecting means for detecting the heating temperature of the heater 26. 28 is attached to the CPU 7 as a temperature control means.
2 and a program written in the ROM 74, the temperature of the platen 14 is kept constant by a control method described later.

On the other hand, a plurality of suction holes 32 are provided in parallel with each other in the recording paper conveyance path near the top and bottom of the platen 14 facing the ink jet head 12.
A fan holder 34, which is connected to the suction hole 32 and is made of a synthetic resin having excellent airtightness, is continuously provided on the back surface of the platen 14, and a fan motor 36 drives a rear end of the fan holder 34. The fan 38 is attached. Therefore, by driving the fan motor 36, the fan 38 rotates and the air in the fan holder 34 is exhausted to the outside of the hot melt ink jet recording apparatus 10 to generate a negative pressure in the fan holder 34. The recording paper 16 fed above is brought into close contact with the platen 14 via the suction holes 32.

Further, as shown in FIG. 2, a paper feed cassette 40 and a manual paper feed tray 42 are arranged on the upstream side of the ink jet head 12 and in the lower portion of the front surface of the apparatus. The inkjet recording device 1 of the paper feed cassette 40 is provided at the rear position where the paper feed cassette 40 is mounted.
Presence / absence of attachment to 0 and attached paper feed cassette 40
There is a cassette sensor 41 for detecting the type. When performing automatic paper feeding, the uppermost one of the recording papers 16 stacked in the paper feeding cassette 40 is fed by the paper feeding roller 4
Feed by 4. Further, when the manual feed is performed, the recording papers 16 are inserted one by one from the manual feed tray 42, and are nipped and fed by the drive roller 46 and the nip roller 48. A manual feed sensor 49 for detecting whether or not the recording paper 16 is set on the manual feed tray 42 is arranged near the nip roller 48.

Further, during manual paper feeding, when the manual paper feed sensor 49 detects that the recording paper 16 is set on the manual paper feed tray 42, the paper feed roller 44 is prevented from being driven. Since the sheet feeding cassette 40 is controlled, the recording sheet 16 is not fed from the sheet feeding cassette 40 even if the sheet feeding cassette 40 is attached to the inkjet recording apparatus 10.

Further, the recording paper 16 fed from the paper feed cassette 40 or the manual paper feed tray 42 is fed onto the platen 14 by a plurality of divided lower feed rollers 62 and pressure rollers 64, and then recorded. The paper 16 is discharged to a paper discharge tray 69 by an upper feed roller 66 and a pressure roller 68 that are divided into a plurality of pieces. The vertical feed rollers 62 and 66 and the pressure rollers 64 and 68 are
It is driven by the paper feed motor 70.

Next, a method of controlling the temperature of the platen 12 described above will be described. The CPU 72 causes the thermistor 28 to rotate the platen 1 by the program in the ROM 74 every unit time.
The temperature of 2 is checked, and the heater 2
The ratio of the time when current is applied to 6 and the time when it is not applied (hereinafter referred to as DUT
Y ratio) is determined based on the control table 82 of the ROM 74. The heater 26 generates heat only when a current flows,
Keep the platen 12 at the set temperature. Generally, such heater temperature control is called PWM control. Further, this control method is performed by the hot melt type inkjet recording apparatus 1 described later.
The temperature control is performed separately from the recording operation of 0, and the temperature control is performed at the same time as the recording operation even during the recording operation.

Next, the control section of the hot melt type ink jet recording apparatus 10 will be described with reference to FIG.

The control unit includes a well-known CPU 72 and ROM 7
4, RAM 76, etc., each of which is connected via a bus. Further, the CPU 72 includes an inkjet head 12, a carriage motor 22, a heater 26 for heating the platen, a thermistor 28 for detecting a heating temperature by the heater 26, a fan motor 36 for generating suction pressure, and the paper feed cassette 40. A cassette sensor 41 for detecting presence / absence and type, a manual feed sensor 49 for detecting whether or not the recording paper 16 is set on the manual feed tray 42, an external device 80 for transmitting recording data, etc. are connected. ..

The ROM 74 stores a control table 82 storing the optimum duty ratio of the heater 26 according to the temperature of the platen 14, and whether or not the temperature change of the platen 14 is drastically reduced by the heat taken by the recording paper 16. An allowable value as a criterion for determining whether or not, a program for controlling the entire hot melt ink jet recording apparatus 10 and the platen 1
A program for keeping the temperature of No. 4 constant is stored.
Further, the RAM 76 stores an image buffer 84 in which the recording data sent from the external device 80 is expanded into image data, temperature data of the thermistor 28 measured at each unit time, various known scales, counters, flags and the like. Has been done.

Next, the recording operation of the hot-melt type ink jet recording apparatus 10 thus constructed will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG.

First, when the recording data is sent from the external device 80, the recording paper 16 in the paper feed cassette 40 is fed to the downstream side in the paper feed path S by the paper feed roller 44 or the drive roller 46. (S11).

Next, the fed recording paper 16 is nipped by the lower feed roller 62 and the nip roller 64,
It is conveyed toward the platen 14 (S12).

Next, the CPU 72 measures the temperature of the platen 14 by the thermistor 28 every unit time (S1).
3). Then, if the measured temperature is compared with the previously measured temperature stored in the RAM 76 and the difference is within the allowable value stored in the ROM 74, the CPU 72 still causes the recording paper 16 to remain on the platen 14. When it is determined that the recording sheet 16 has not been fed (YES in S14), the lower feed roller 62 and the nip roller 64 continue to convey the sheet 16, and the recording operation on the recording sheet 16 by the inkjet head 12 is not yet started. On the other hand, when the recording sheet 16 reaches the platen 14, the recording sheet 16 takes away the heat of the platen 14,
The temperature of the platen 14 falls below the allowable value stored in the ROM 74 within a unit time. Therefore, when the temperature measured in S13 is compared with the previously measured temperature stored in the RAM 76 and the difference exceeds the allowable value recorded in the ROM 74, the CPU 72 causes the recording paper 16 to move to the platen 14 It is judged that it has reached above (S14 ・ N
O), the fan motor 36 is driven to bring the recording paper 16 into close contact with the platen 14 via the suction holes 32 by the fan 38 (S15).

Then, the ink jet head 12 moves to the R
Based on the data in the image buffer 84 of AM76,
The recording operation is performed on the recording sheet 16 while being moved in the recording direction perpendicular to the sheet conveying direction by the carriage motor 22, and when the recording operation for one line is completed, the lower feed roller 66 and the pressure roller 68 move the recording sheet 16 to the 1st direction. The paper is fed by the line, and these operations are repeated to execute the recording process for one page (S16).

The recording paper 16 on which the recording process for one page has been completed has an upper feed roller 66 and a pressure roller 68.
Is discharged to the paper discharge tray 69 (S17),
The rotation of the fan motor 36 is stopped.

With the above-described structure, the hot melt type ink jet recording apparatus 10 has the platen 14
In addition, the leading edge of the conveyed sheet can be detected with a simple structure without increasing the number of parts.

Although not specifically exemplified, the present invention is not limited to the present embodiment, and various changes can be made by the judgment of the parties within the scope not departing from the spirit of the present invention. For example, in the present embodiment, the temperature of the thermistor 28 is used as the determination for detecting the leading edge of the sheet, but the DUTY ratio may be used.
That is, in S13 of FIG. 5, the CPU 72 causes the thermistor 2 to
Instead of checking the temperature of the platen 14 via 8 and comparing it with the previous temperature, the CPU 72 uses the heater 2 for each unit time.
When the DUTY ratio of 6 is 100%, that is, when there is no time during which no current flows within the unit time, it is determined that the leading edge of the recording paper 16 has reached the platen 14, and the recording process is started. Things are possible.

[0032]

As is apparent from the above description, the sheet leading edge detecting apparatus of the present invention can detect the leading edge of the recording sheet with a simple structure without increasing the number of parts.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a cross-sectional view of a hot melt ink jet recording apparatus embodying the present invention.

FIG. 3 is a partial perspective view of a recording mechanism and a suction mechanism of this embodiment.

FIG. 4 is a block diagram showing an electrical configuration.

FIG. 5 is a flowchart of this embodiment.

FIG. 6 is a cross-sectional view of a conventional hot melt ink jet recording apparatus.

[Explanation of symbols]

 14 Platen 26 Heater 28 Thermistor 72 CPU 74 ROM 76 RAM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B41J 11/42 M 9011-2C 29/42 F 8804-2C

Claims (1)

[Claims] 1. A sheet leading edge detecting device for detecting the leading edge of a sheet in a sheet transporting path, a supporting member for supporting the sheet at the time of printing, a heating unit for heating the supporting member, and a temperature for the supporting member. Temperature detecting means, a temperature control means for keeping the temperature of the supporting member constant by the signal of the temperature detecting means, and a paper leading edge detecting means for detecting the leading edge of the paper by the change of the signal of the temperature detecting means. A paper leading edge detection device comprising: