JPH0377064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an on-demand ink jet recording apparatus. Establishing reliability has become the most important issue for this on-demand type inkjet recording device in order to put it into practical use. Under these circumstances, the present inventor has already filed a patent application for an inkjet recording device that operates stably under all environmental conditions.
- Proposed as No. 155209.

The present invention develops this proposal and makes improvements for practical use.

The above proposal is equipped with a mechanism that uses a cap and a pump to fill ink into the head before recording, and this prevents any problems such as dust from adhering to the nozzle surface or air bubbles from forming inside the head. In addition, it has a switching valve that discharges the ink inside the head when not recording or at abnormally high or low temperatures to prevent damage to the head due to ink solidifying in the nozzle or freezing. It was something to prevent. The present invention further embodies this basic idea and adds a number of improvements for practical use.

An object of the present invention is to prevent the inner bottom of the device from being soiled by ink that scatters when the cap is removed from the nozzle end face after filling the head with ink.

Hereinafter, the mechanism of the present invention will be explained in detail based on examples.

FIG. 1 shows an embodiment of the inkjet recording apparatus of the present invention, and is a schematic diagram of the vicinity of the standby position. Since each member will be explained in detail later, only the arrangement of these elements is shown here. An inkjet head 1 (hereinafter simply referred to as the head) is mounted on a carriage 2, and is guided by a carriage shaft 3 to move left and right. However, in the area facing the recording paper 4, a printing operation is performed, and outside the area facing the recording paper 4, which is a standby position, operations such as ink filling, discharge, cleaning, etc. are performed.

When the carriage 2 moves from the printing area to the standby area, the protrusion 6 of the carriage 2 engages with a micro switch 7 attached to the base of the device.
When the switch is operated, the carriage 2 is stopped by the stopper 8. At this time, head 1 faces head cleaner 9 and cleaner 9
When operated, the nozzle surface of head 1 is cleaned. The role of the stopper 8 here is to ensure the accuracy of the stop position of the carriage 2, which can be achieved by cutting off the power of the drive source (motor, etc.) of the carriage 2 with a slight delay in the operation of the micro switch 7. . When the cleaning operation is completed, the solenoid 23 is energized, the suction cap 10 is retracted, and the stopper 8 is displaced from the stop position of the carriage 2. Then, the carriage 2 moves further to the left and stops when it hits the frame 11 on the left end, and the head 1 and the suction cap 10 now face each other, so when the power to the solenoid 23 is turned off, the suction cap 10 is moved back to the head by the restoring force of the spring. The head 1 is filled with ink or discharged by bringing the nozzle surface of the head 1 into close contact with the head 1 and operating a pump (described later). At the end of ink filling, ink is filled by suction from the nozzle.
To ensure filling, excess ink is extracted from the nozzle, so it is necessary to take measures such as opening the cap 10 with a slight delay after the pump is stopped, as will be described later, but ink adhesion to the nozzle surface cannot be avoided. There is a risk that this adhered ink may drip during the printing operation φ, etc., and stain the bottom of the apparatus. Therefore, an ink absorption container 12 is provided on the left side of the head 1, and as shown in FIG. 2, the adhering ink 13 on the nozzle surface of the head 1 is received by a receiving portion 14 and absorbed into the ink absorption container 12 using a porous member or the like. . However, in the long term, this absorption container 1
Since it is possible that 2 will also be saturated, the absorption container 12
A hole 15 is provided in the left wall of the absorber 12, and when the carriage 2 reaches the leftmost position, the member 16 attached to the left frame 11 enters this hole 15 and compresses the porous member inside, which is provided at the bottom of the absorption container 12. The ink absorbed by the porous member is discharged from the discharge port 17. At this time, the ink drops onto the receiving member 18 and is led to the waste ink container through the conduit 19.

Next, details of the cleaner 9, suction cap 10, their driving parts, etc. will be described. FIG. 3 is an exploded perspective view of these mechanisms. 4 and 5 are side views, respectively, seen from the directions of arrows A and B in FIG. 3. The motor 20 has a pump 21 and a switching valve 2.
2. It is a power source that drives the cleaner 9 and the like.
Reference numeral 23 denotes a solenoid for moving the suction cap 10 and the cleaner 9. All of these members are attached to the first frame 24 and the second frame 25, forming an integrated unit. (Fig. 1).

The rotation of the motor 20 is decelerated by a gear train and is finally transmitted to a gear 26. On the shaft 27 there is an actuating plate 28 that drives the pump 21 on one side, and a switching valve 22.
A cam 29 that drives the pump 21, a detection plate 30 that detects the bottom dead center of the pump 21, and a belt pulley 36 are pivotally mounted. The pump 21 functions by engaging the pin 281 on the actuating plate 28 and the pin follower 30 to reciprocate the piston shaft 31. Naturally, the piston and cylinder of the pump 21 are required to have a low coefficient of friction and be airtight. Here, the piston is made of rubber, and its elasticity makes it airtight, and its surface is coated with a fluororesin film to reduce the coefficient of friction. A coating agent containing rubber as a binder (for example, Daiel Latex manufactured by Daikin Industries) is suitable for this fluororesin film.

The pump may be of the bellows type shown in FIG. 6, but may be replaced by a piston-cylinder type. A piston shaft 31 is fixed to one end of a rubber-molded bellows 32 and is airtightly mounted on the pump body 21.
The bellows 32 is expanded and contracted by reciprocating the one-way valve 34,
35, it can perform the same function as the piston-cylinder type, but since there are no sliding parts, it is more reliable.

On the other hand, the cam 29 mounted on the shaft 27 is connected to the switching valve 2.
2, and the conduit 2 from the switching valve 22
21 and 222 are connected to the head 1 and an ink tank (not shown), respectively. The actuation of the switching valve 22 causes the conduit 221 connected to the head 1 to communicate with the conduit 222 or with the atmosphere, thereby performing ink suction and discharge operations. Although not shown, since the gasket for switching the flow path of the switching valve 22 slides to switch, it is required to have a low coefficient of friction and airtightness just like the piston of the pump 21, and its surface is also made of fluorine. Coated with resin film.

Furthermore, a detection plate 30 attached to the shaft 27 is for detecting the bottom dead center of the piston of the pump 21, and a permanent magnet 33 is fixed to the detection plate 30, which is attached to the second frame 25. A magnetic detector 371 on the substrate 37 can detect one point during one rotation of the detection plate 30. This can be detected by aligning this position with the bottom dead center of the piston. This is because when filling the head 1 with ink, if the motor 20 is stopped during the depressurization process of the piston and the suction cap 10 is removed from the head 1, the ink being ejected from the nozzle will scatter to the outside the moment the cap 10 is opened. Become. Therefore, at least during the pressurizing process of the piston, this can most certainly be avoided by stopping the pump 21, ie, the motor 20, at the bottom dead center of the piston and opening the cap 10. However, in reality, since the ink flows through the conduit between the pump 21 and the suction cap 10, the pressurization and depressurization of the piston is slightly delayed inside the suction cap 10. Therefore, if the motor is stopped during the piston pressurization process and the suction cap 10 is immediately released from the head 1, ink may still scatter to the outside. To avoid this, if the motor is stopped during the piston pressurization process and the suction cap 10 is released after a few seconds (according to experiments, 1 to 5 seconds), the ink will not scatter to the outside. Therefore, in the ink filling operation, it is important to use the detection plate 30 described above to detect the piston's pressurization process to the bottom dead center and control the motor 20 to stop.

Further, a belt pulley 36 is attached to the shaft 27, and a belt 38 is wrapped around the belt pulley 36 to operate the cleaner 9. As shown in the figure, the cleaner 9 has a plurality of spatula-shaped protrusions 9 on a flat rubber ring, and is hung on two cleaner shafts 39 and 40. The above-mentioned belt 38 has a belt wheel 36 placed between one end of the cleaner shafts 39 and 40, and when the gear 26 by the motor 20 rotates, the cleaner 9 is operated from the belt 38, and when facing the head 1, the cleaner 9 is activated. 91 serves to scrape off dust, fluff, etc. from the nozzle surface.

Next, the function of the solenoid 23 will be described with reference to FIG. 7, which is a schematic diagram of the solenoid system. The movable magnetic core 231 of the solenoid 23 engages with a cap support 43 via an actuating lever 42. The suction cap 10 is attached to the cap support 43 by an axis 44, so that the suction cap 10 can swing slightly about the axis 44 (arrow C). This is important so that when the suction cap 10 engages the head 1, there is an airtight engagement. The cap support 43 is attached to the shaft 45 and is subjected to the force of arrow D by the tension spring 46, that is, receives the rotational force of the arrow E around the shaft 45, and abuts against the stopper 47. When the solenoid 23 is energized, the movable magnetic core 231 is attracted into the solenoid 23 and is moved to the cap support 43 via the operating lever 42.
is rotated in the direction opposite to the arrow E against the force of the tension spring 46. This rotation disengages the suction cap 10 from the head 1. Alternatively, the head 1 can be moved into the position of the suction cap 10. In the embodiment of FIG. 3, the solenoid 23 not only operates the suction cap 10 as described above, but also the cleaner 9, whose cleaner support 48 is attached to a shaft 45 like the cap support 43 and receives the action of a tension spring 46. Therefore, when the solenoid 23 is energized, it moves in the same way as the suction cap 10. Therefore, when the head 1 and the cleaner 9 are facing each other and the solenoid 23 is not energized, the protrusion 91 of the cleaner 9 comes into contact with the nozzle surface of the head 1, and the motor 10 is driven to scrape off dirt from the nozzle surface. However, when the solenoid 23 is energized, the projection 91 is released from contact with the nozzle surface. To explain the reason for this configuration, referring back to FIG. 1, the carriage 2 comes from the printing area to a position opposite the cleaner 9. At this time, the solenoid 23 is not energized, but the protrusion is made of rubber, and its elastic deformation allows the head 1 to move toward the cleaner section. After cleaning at this position, the solenoid 23 is energized to release the suction cap 10 and the head 1 is moved to the suction cap 10 position. Then, the solenoid 23 is de-energized, the head 1 and the suction cap 10 are brought into airtight engagement, and the pump 21 is activated to refresh the ink in the head.

Thereafter, the solenoid 23 is energized again and the carriage 10 is moved all at once to the printing area with the suction cap 10 and cleaner 9 released. At this time, the nozzle surface is not in contact with the protrusion 91 of the cleaner 9. That is, although the cleaner 9 scrapes off paper dust and the like adhering to the nozzle surface, on the contrary, dirt and fluff adhere to the protrusions of the cleaner 9. Therefore, if the protrusion 91 of the cleaner 9 is brought into contact with the nozzle surface of the head 1 after refreshing it with the suction cap, there is a risk of contaminating the nozzle surface.

In this embodiment, in order to avoid this, the cleaner 9 is not contacted after the head is refreshed.

Next, the operation of the stopper 8 shown in FIG. 1 will be explained with reference to FIG. The stopper 8 is rotatably attached to the first frame 24 on a shaft 49, and one end 50 of the stopper 8 engages with the actuating lever 42. Therefore, when the solenoid 23 is energized, the stopper 8 rotates about the shaft 49, so that the other end 51 moves. This end 51 when the solenoid 23 is de-energized
The position of the carriage 2 serves as a stopper for the carriage 2, and the shape of the carriage 2 is shaped such that the position when energized releases the stopper, and has the function described in FIG.

The embodiments of the mechanism for filling the head 1 with ink and cleaning the ink discharge nozzle surface have been described above. Next, the operations (control methods) of these mechanisms will be summarized and described below, although some parts overlap with those described above.

(1) Cleaning Head 1 cleaning is performed when printing becomes irregular during recording. According to experience, printing irregularities are caused by abnormal ejection of ink droplets from the nozzles.
The most common cause is paper dust and other dust generated from the recording paper adhering to the nozzle, and other causes include air bubbles forming inside the head, making it impossible to eject, or a particular nozzle not being able to eject for a long period of time. It is possible that the ink in the nozzle solidifies and becomes unable to eject. However, anything other than the above-mentioned paper dust is extremely rare. Therefore, cleaning is performed by the user by pressing the cleaning switch when a recording abnormality occurs, but if the probability of paper dust adhesion is calculated and automatic cleaning is performed periodically, the user's operation can be minimized. Experiments have shown that paper dust adheres to the nozzle after 5 to 20 hours of continuous recording, depending on the quality of the recording paper and the atmosphere in which the device is placed. Therefore, for example, regardless of whether it is recorded or not, 5
Automatic cleaning may be performed every hour, or automatic cleaning may be performed by appropriately determining the amount of printing and the stop time.

The cleaning operation involves the series of operations described below (see Figure 1).The carriage 2 is moved to the left, the power to the carriage 2 is stopped after a slight delay (about 1 second) from the time when the micro switch 7 is activated, and the carriage 2 is moved to the left. to surely stop at the stopper 8 position. Here, the nozzle surface of head 1 and cleaner 9 are facing each other, so motor 2
When 0 is driven, the cleaner 9 is activated to scrape off dust from the nozzle surface. (This operation takes about 2 to 3 seconds) Next, the solenoid 23 is energized and the suction cap 1
0. With the stopper 8 released from the head 1 and the carriage 2, move the carriage 2 further to the left and stop it when it hits the left frame 11.
Here, the solenoid 23 is de-energized, the suction cap 10 is hermetically engaged with the nozzle surface, and the motor 20 is
is driven in the ink filling direction. This will refresh the ink in the head. Here, the motor 20 is at the bottom dead center of the pump 21 or at least
It is controlled to stop when the inside of the cylinder is in the pressurizing process. The ink refresh process in this head takes 2 to 5 seconds. Next motor 2
After the stop of 0, the solenoid 23 is energized again after a delay (1 to 4 seconds), the suction cap 10 is released, and the carriage 2 is moved to the right toward the printing area.

(2) Ink discharge When discharging ink, the nozzle surface should be cleaned.Similar to the cleaning operation described above, after cleaning with the cleaner 9, the suction cap 10 is hermetically engaged with the nozzle surface, and the motor 20 is moved in the ink discharge direction. drive The switching valve 22 switches to the atmosphere and fills the head with air, thereby discharging the ink inside. (This process takes 10-40 seconds)
The motor 20 is stopped at an arbitrary position and maintained at that position. That is, the head and suction cap remain engaged until the next time power is applied to the device.

(3) Ink filling Ink filling into the head is performed after the ink in the head has been discharged and before printing.

As described above, if ink is always discharged when the power is turned off, ink filling is always performed when the power is turned on.

The ink filling operation may be the same as the cleaning operation described above. However, since the head 1 often starts in a state in which it is engaged with the suction cap 10, in that case, the operation of the cleaner 9, etc. is omitted, and filling can be performed by simply rotating the motor 20 in the ink filling direction. Also, the motor 20 may be stopped at the bottom dead center of the pump or during the pressurization process, similar to the cleaning operation.

Although the embodiments of the present invention have been described in detail above, the present invention is based on the development and improvement of the earlier application (Japanese Patent Application No. 155209/1982), and thereby more stably and reliably fills ink into the head, discharges it, and cleans it. This greatly contributes to improving the reliability of inkjet recording devices.

As in the present invention, by finishing ink filling during the pump pressurization process, the ink will not scatter even if the nozzle cap is removed from the head.
Reliable ink filling is possible without soiling the bottom of the device.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the inkjet recording apparatus of the present invention, and shows an outline of the vicinity of the standby position. FIG. 2 is a view of the head viewed from the nozzle end side.
FIG. 3 is an exploded perspective view showing the apparatus of FIG. 1 in more detail. 4 and 5 are side views seen from the directions of arrows A and B in FIG. 3. FIG. 6 shows an embodiment of the pump used in the device of the present invention. 7th
The figure is a diagram for explaining the movement of the suction cap. 1...head, 10...suction cap, 20...
...Motor, 21...Pump.

Claims (1)

[Scope of Claims] 1. An ink jet head having a nozzle end surface equipped with an ejection nozzle; an ink supply source that supplies ink to the ink jet head; The pump is equipped with a suction cap that selectively comes into close contact with the suction cap, a pump having a one-way valve and a pressure chamber that communicates with the suction cap and repeats pressurization and depressurization, and a power source for operating the pump. An inkjet recording apparatus characterized by comprising a control means for shutting off the power source and terminating the operation of filling the inkjet head with ink from the ink supply source during the pressure stroke. 2. The inkjet recording apparatus according to claim 1, wherein the control means is means for cutting off the power source near the bottom dead center of the pressurizing stroke of the pump.