JPS61217255A - Ink jet pump - Google Patents

Abstract

PURPOSE:To eliminate bubbles in ink and consequently unnecessitate printing treatment by providing an exhaust control means to be driven based on a detection signal transmitted by a bubble detection means to detect whether there are bubbles in a pump chamber. CONSTITUTION:An output signal from a pressure sensor PS and an air sensor AS is input to a control 21, and a control signal is output from the controller 21 as an exhaust control means to a stepping motor and a solenoid valve 14. If the existence of bubbles in a pump chamber 1 is determined by the air sensor AS, a solenoid valve V to an exhaust flow path 13 is opened to make the pump chamber 1 continuous with the exhaust flow path 13. A plunger 2 is plunged into the pump chamber 1 by driving the stepping motor. Bubbles in the pump chamber 1 are pushed out with ink into the exhaust flow path 13 continuous to the pump chamber 1, and conducted to a waste liquid section outside the pump chamber 1 through a pipe 22, thus eliminating bubbles in ink.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ink jet pump used in an inkjet printer or the like, and more specifically, to an ink jet pump that sucks ink into the pump chamber by moving a plunger into and out of the pump chamber. The present invention relates to an inkjet pump that pumps ink.

[Conventional technology]

Inkjet printers are excellent recording devices that can record at high speed and with low noise, and can use plain paper as recording paper. Therefore, if air bubbles are present in the ink used for recording, there is a risk of causing ink ejection failure and resulting recording failure. Therefore, various methods have been proposed to remove air bubbles from ink.

For example, there is a device in which a degassing tank having an exhaust port is provided in the ink flow path between an inkjet pump and a jetting nozzle, and this degassing tank is mounted on a carriage together with the jetting nozzle (for example, Japanese Patent Laid-Open No. 58-191168 issue).

However, with the above configuration, it is necessary to move the degassing tank together with the injection nozzle when recording, which requires a large carriage drive device and poses an obstacle to increasing the recording speed. It was something to do.

Therefore, the applicant previously proposed a system in which air bubbles in the pump chamber could be removed by attaching an air venting member to the upper end of the inkjet pump chamber and removing the air venting member. Showa 59-202
(See No. 084).

[Problem that the invention seeks to solve]

However, the structure of the prior application described above may have the following disadvantages, and there is still room for improvement.

First, when removing air bubbles in the pump chamber, it is necessary to remove the air venting member and also to drive the plunger, which is a time-consuming operation. Further, when removing air bubbles, ink overflows from the upper end of the pump chamber together with the air bubbles, so a configuration for processing this ink is required.

In view of the above circumstances, an object of the present invention is to provide a structure for removing air bubbles in ink without requiring any trouble.
The purpose is to eliminate the need for post-treatment of ink.

(Means for Solving the Problems) The characteristic configuration of the inkjet pump according to the present invention is that an exhaust flow path is connected to the upper end of the pump chamber via an on-off valve, and an ink discharge path is connected to the pump volume below this on-off valve. and an ink suction path, and a means for detecting the presence or absence of air bubbles in the pump chamber, and an on-off valve at the upper end of the pump chamber when air bubbles are present in the pump chamber based on a detection signal from the air bubble detection means. The present invention is characterized in that an exhaust control means is provided which opens the exhaust flow path to communicate with the pump chamber and drives the plunger so as to plunge into the pump chamber.

[For production]

In other words, the air bubbles in the ink float to the surface and accumulate in the pump chamber above the ink ejection path, so that the air bubbles are not pumped out together with the ink from the ink ejection path. When the air bubbles accumulated in the pump chamber are detected by the air bubble detection means, the path to the exhaust flow path is opened and the plunger is plunged into the pump chamber, thereby automatically discharging the air bubbles along with the ink to the outside of the pump chamber. It can be removed. However, since the air bubbles are discharged through the exhaust flow path, the ink does not overflow.

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 1 shows a cross section of an inkjet pump used in an inkjet printer. A male screw member (3) is fixed to one end of a plunger (2) that moves in and out of the pump chamber (1) of this inkjet pump, and a female screw member (3) is screwed into this male screw member (3). 4) is the drive shaft (
6) via a coupling (7). Further, the plunger (2) is connected to a rotation prevention member (9) having a pair of rollers (8), and the pair of rollers (8) are guided along the moving direction of the plunger (2). The plate (10) is arranged so as to be sandwiched from both sides.

That is, by rotating the stepping motor (M), the roller (8) of the detent member (9) is moved from the guide plate (
10) to prevent rotation of the plunger (2), the female screw member (4) and the male screw member (3)
The plunger (2) is moved up and down in the figure by relatively rotating the pump and the plunger (2) to move it into and out of the pump chamber (1).

An ink suction path (11) that communicates with an ink tank (not shown) and an ink discharge path (12) that communicates with an injection nozzle (not shown) are connected to the pump chamber (1), respectively. has been done. Then, by retiring the plunger (2) from the pump chamber (1), the inside of the pump chamber (1) is made negative pressure, and ink is sucked from the ink suction path (11) equipped with a check valve. In addition, the plunger (
2) into the pump chamber (1), the ink in the pump chamber (1) is pressurized, and the ink discharge path (12)
The ink is force-fed from the ink to the jet nozzle. Although not shown, a first limit switch that detects that the plunger (2) has reached its stroke end, and a second limit switch that detects that the plunger (2) has reached its standby position are provided, respectively. It is provided opposite to the detection section connected to the rotation prevention member (9).

As shown in FIGS. 1 and 2, the ink suction path (11)
An exhaust flow path (13) is provided in the pump chamber (1) above the part that connects the ink discharge path (12) and the air bubbles mixed in the ink to the outside of the pump chamber (1). are connected via an electromagnetic on-off valve (V). The valve body (14) of this electromagnetic on-off valve (V) is normally urged toward the pump chamber (1) by a spring (15).
The inside of the pump chamber (1) is sealed by an O-ring (17) interposed between the valve body (14) and the pump chamber (1). Then, by energizing the electromagnetic coil (16) of this electromagnetic on-off valve (v), the valve body (14
) by pulling it upward in the figure to open the pump chamber (1).
and the exhaust flow path (13) are communicated with each other.

The pump chamber (1) further includes a pressure sensor (PS) that detects the pressure of ink within the pump chamber (1), and an air sensor (AS) that detects the presence or absence of air bubbles within the pump chamber (1).
) is provided. The pressure sensor (PS) is fixed by a stop member (20) screwed to the cylinder body (19) with the inside and outside of the pump chamber (1) sealed by an O-ring (18). The air sensor (AS) has a pair of electrodes (17) provided in the pump chamber (1), and has a resistance value that changes depending on the presence or absence of ink between the two electrodes (17). ) to detect the presence or absence of air bubbles within.

The output signals from the pressure sensor (PS) and the air sensor (AS) are input to the control bag ff (21), and based on the detection signals from both the sensors (PS) and (AS), the exhaust control means This control device (21) outputs control signals for the stepping motor (M) and the electromagnetic on-off valve (14).

In other words, this air sensor (AS) causes the pump chamber (1) to
If it is determined that there are air bubbles in the exhaust flow path (13)
Open the solenoid on-off valve (V) for the pump chamber (1).
and the exhaust flow path (13).

Thereafter, the stepping motor (M) is driven to plunge the plunger (2) into the pump chamber (1).

The air bubbles in the pump chamber (1) rise to the surface and accumulate near the upper end of the pump chamber (1), and when the plunger (2) enters the pump chamber (1), the air bubbles are moved together with the ink into the pump chamber (1).
The pipe (
22) via a drainage part (not shown) outside the pump chamber (1)
guided by. Therefore, without any trouble,
Air bubbles in the ink can be removed without the ink overflowing outside the pump chamber (1).

Moreover, this electromagnetic on-off valve (v) acts as a safety valve for the inkjet pump. In other words, if the pressure of the ink is (P) and the area where the valve body (14) of the electromagnetic on-off valve (V) faces the pump chamber (1) is (D), the pressure of the ink causes the valve body (14) to The applied force (F) is F-1]・P, and this force (F) is the biasing force of the spring (15) (
(F>W), that is, if the ink pressure becomes abnormally high, the valve body (14) is pushed upward in the figure regardless of the presence or absence of air bubbles in the ink, and the pump chamber (
1) and the exhaust flow path (13),
It acts to lower the pressure inside the pump chamber (1).

In the inkjet printer according to this embodiment, the above-mentioned inkjet pumps are provided, one each for each of the four color inks of yellow, magenta, cyan, and black, and each of the ink jets pumped by these pumps is A color image can be recorded by a subtractive mixture of the three primary colors ejected from the nozzle and the addition of black.

Figure 3 shows an inkjet printer control device (21)
FIG. The main part of this control device (21) is composed of a microcomputer. The central processing unit of the microcomputer (hereinafter referred to as CP)
Output ports (P,) to (P4) of (22) (abbreviated as U)
) are the stepping motors (Mv) and (MM
), (MC), and (Ml) to output pulse signals as motor drive signals via separate data latch circuits (23a) to (23d) and power drive circuits (24a) to (24d). It is composed of: Also C
The P U (22) receives various external control signals, image signals, etc., and also receives a pressure sensor (PSY) attached to the pump chamber (1) of each inkjet pump.
), (PSM), (psc).

The detection signal from (PSa) is input capo-1-(II) ~
(I4), respectively.

And each pressure sensor (PSV), (PSM
).

Based on the detection results by (psc) and (PSE), each stepping motor (MY) and (MH) are operated so that the pressure inside each pump chamber (1) is always maintained at a constant pressure.
, (MC).

(MR) is rotated, and its rotation is controlled by a screw feeding mechanism (
SS) is configured to convert the plunger (2) into a linear motion and plunge the plunger (2) into the pump chamber (1). Further, when the predetermined drawing is completed and the plunger (2) reaches its stroke end, each motor (My) is activated by detection by the first limit switch.

(Ml, I), (Me), (ME) are driven in reverse, the plunger (2) is retired from the pump chamber (1), and new ink is sucked into the pump chamber (1). be.

In addition, CP tJ (22) has air sensors (^Sy), (ASM) attached to each pump chamber (1),
The signals from (^sc) and (^ss) are incoming capo) (1
6) -(I,) and the output port
) From (Ps) to (ps), on-off solenoid valves (v) for the exhaust passages (13) connected to each pump chamber (1),
It is configured to output control signals through separate drivers (25a) to (25d).

And each of these air sensors (ASW), (ASW
).

Based on the detection results by (^Sc) and (ASa), if there is a bubble in any of the pump chambers (1), the electromagnetic coil (16) of the electromagnetic on-off valve (v) for that pump is energized, and The stepping motor (M) for the pump is driven in normal rotation. In other words, the electromagnetic on-off valve (V)
By opening the pump chamber (1), the exhaust flow path (13)
At the same time, the plunger (2) is connected to the pump chamber (
1) The air bubbles in the pump chamber (1) are discharged and removed from the pump chamber (1) together with the ink by injecting the ink into the pump chamber (1). When the plunger (2) reaches its stroke end, the first limit switch detects that the stepping motor (M) is temporarily stopped and reversed, and the electromagnetic on-off valve (V) is closed, and new ink is pumped into the pump chamber ( 1) It is configured to be inhaled into the body.

Furthermore, the CPU (22) has the above-mentioned pump chamber (
1) A manual switch (
A signal from SN) is input.

When this switch (S4) is operated, the bubble removal operation is performed for the ink jet pumps of all colors.

Next, the operation of the inkjet printer by the above-mentioned control 11 device (21) will be explained based on the flowchart shown in FIG.

This flow starts when the inkjet printer is powered on. First, any air sensor (ASY)
, (ASW), (ASC), (^SB) to check whether air bubbles are detected in the pump chamber (1) (old). Which air sensor (ASy),
(ASW).

If no bubbles are detected by (ASC) or (^SS), then it is checked whether the manual switch (SM) has been operated (12). If the manual switch (SN) is not operated, the state of the print switch is further checked (I3).

If the print switch is not "ON", the process returns to step (I1), and if the print switch is pressed, the print process is performed (#4) and then the process returns to step (III). Thereafter, this process is repeated to record images.

In step (#1), either air sensor (ASV)
, (Δ5ll), (8SC), (AS++) when it is detected that there is a bubble in the pump chamber (1), and in step (112), the manual switch (3,
If it is detected that 4) has been operated, the flow proceeds to step (#5) and subsequent steps.

In step (#5), the necessary electromagnetic coil (16) of the inkjet pump is energized to open the electromagnetic on-off valve (V) and communicate the pump chamber (1) with the exhaust flow path (13). Subsequently, after waiting for about 1 second, a forward rotation drive pulse signal is output to the plunger drive stepping motor (M) to cause the plunger (2) to rush into the pump chamber (1) (#6). As a result, the air bubbles in the pump chamber (1) are pushed out together with the ink into the exhaust flow path (13). After that, while checking the status of the first limit switch (
#7) Continue driving the stepping motor (M) in the normal rotation until the plunger (2) reaches its stroke end.
When the first limit switch is closed, the electromagnetic coil (1
6) is stopped (18). As a result, the valve body (14) of the electromagnetic on-off valve (V) is pushed back by the spring (15), and the pump chamber (1) and the exhaust flow path (13) are cut off by the O-ring (17). continue,
Stop outputting the iE reversing drive signal to the stepping motor (M) (#9). After waiting for about 1 second, output the reverse drive pulse signal to the stepping motor (M) and pump the plunger (2). Retire from room (1) (11
10); As a result, the inside of the pump chamber (1) becomes negative pressure,
New ink is sucked into the pump chamber (1) from the ink tank via the ink suction path (11).

Thereafter, while checking the state of the second limit switch (Ill), the stepping motor (M) continues to be driven in reverse, and when the plunger (2) reaches its standby position and the second limit switch is closed, ( Return to step Ill). Thereafter, the above-mentioned operation is repeated.

In the previous embodiment, the pump chamber (1
) is provided with an air sensor (AS), and this air sensor (A
The method for detecting the presence or absence of air bubbles in ink using S) has been described. Instead of this format, the presence or absence of air bubbles in the ink may be detected by the control device (21).

In other words, if there are air bubbles in the ink, even if the plunger (2) is plunged into the pump chamber (1), the air bubbles will be compressed, so the pressure of the ink will rise to a predetermined pressure than usual. It also takes a long time. Therefore, the pressure sensor (
Based on the detection result by the stepping motor (M), if the predetermined pressure is not reached even after a predetermined period of time has elapsed from the start of driving the stepping motor (M), it is determined that there are air bubbles in the ink, and the exhaust flow path (13 ) may be opened. Therefore, the air sensor (AS) in the previous embodiment and the above-described configuration for detecting the presence or absence of air bubbles in the ink are referred to as air bubble detection means (^S).

The on-off valve (V) for the exhaust flow path (13) may be of a type opened and closed by a mechanical interlocking mechanism instead of the electromagnetic type described in the previous embodiment.

〔Effect of the invention〕

As described above, the inkjet pump according to the present invention collects air bubbles in the ink in the two pump chambers than the ink discharge path, and automatically transfers the air bubbles to the outside of the pump chamber based on the detection by the air bubble detection means. Since the ink is discharged and removed immediately, it is now possible to effectively remove air bubbles in the ink with almost no effort.Furthermore, the ink does not overflow at that time. Because,
It is now possible to omit the configuration for handling overflow ink, which was required in the past.

Therefore, as a whole, it has become possible to provide an excellent inkjet pump that can remove air bubbles in ink without any trouble and does not require treatment of overflowing ink.

In particular, as explained in the previous embodiment, if a valve of the type that is always biased toward the closing side by a spring is used as the opening/closing valve for the exhaust flow path, when the pressure inside the pump chamber increases abnormally, Since the on-off valve is opened by the pressure and communicates the exhaust flow path with the pump chamber to release the pressure, it can also function as a safety valve for the inkjet pump.

[Brief explanation of drawings]

The drawings show an embodiment of an inkjet pump according to the present invention, in which FIG. 1 is an enlarged sectional view showing a connection part of an exhaust flow path, FIG. 2 is a sectional view of the inkjet pump, and FIG. 3 is a block diagram of a control device. FIG. 4 is a flowchart showing the operation of the inkjet printer. (1) Pump chamber, (2) Plunger, (11) Ink suction path, (12
)... Ink discharge path, (13)... Exhaust flow path, (21)... Exhaust control means, (V)...
...Opening/closing valve, (AS)...Bubble detection means.

Claims (1)

[Claims] In an inkjet pump that sucks ink into the pump chamber and pumps it by moving a plunger into and out of the pump chamber, an exhaust flow path is connected to the upper end of the pump chamber via an on-off valve, and an exhaust flow path is connected to the upper end of the pump chamber via an on-off valve. A means for connecting an ink suction passage and an ink discharge passage to the pump chamber, and a means for detecting the presence or absence of air bubbles in the pump chamber, and a means for detecting the presence of air bubbles in the pump chamber based on a detection signal from the air bubble detection means; An inkjet pump provided with an exhaust control means that opens an on-off valve to communicate an exhaust flow path with a pump chamber and drives the plunger so as to plunge into the pump chamber.