JP2003200589A - Ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet printer having a mechanism of simple arrangement for heating ink without causing an undue temperature rise. <P>SOLUTION: An ink heating mechanism 70 disposed in the ink jet printer comprises PTC thermistors 71-74 for heating ink of respective colors, and a circuit 80 for controlling conduction thereof wherein the conduction control circuit 80 comprises an NTC thermistor 75 and a conduction control transistor Tr1 having a base application voltage being controlled by the NTC thermistor 75 depending on the environmental temperature. Since the NTC thermistor 75 has a high resistance when the environmental temperature is low, the base application voltage is raised and conduction amount of the PTC thermistors 71-75 is increased thus increasing heat generation. Since the resistance of the NTC thermistor 75 decreases as the environmental temperature rises, the base application voltage is lowered and conduction amount of the PTC thermistors 71-74 is decreased thus suppressing or stopping heat generation. Since the PTC thermistor is also provided with a self temperature control function, undue temperature rise of ink can be prevented more reliably through simple circuitry. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer provided with an ink heating mechanism for keeping an ink viscosity in an appropriate state without being affected by environmental temperature.

[0002]

2. Description of the Related Art Ink jet printers print by ejecting ink droplets from the ink nozzles of the ink jet head. Therefore, unless the viscosity of the ejected ink is appropriate, the ink droplets cannot be ejected properly from the ink nozzles. . Since the ink viscosity varies depending on the temperature, it is necessary to heat the ink in order to maintain the ink viscosity in an appropriate state even at a temperature significantly lower than room temperature.
Therefore, conventionally, a heater and a temperature sensor are arranged in the inkjet head, and when the temperature of the ink supplied to the ink nozzle is low, the heater is energized to heat the ink. An ink jet printer provided with such a heating mechanism is disclosed in, for example, Japanese Patent Laid-Open No. 9-13.
No. 1896.

[0003]

However, if the ink is overheated, proper ink ejection characteristics cannot be ensured, so it is necessary to take measures to prevent the ink from overheating. In addition, it is necessary to take safety measures to prevent overheating of the heater. For example, it is necessary to add a temperature control element such as bimetal. However, conventionally, a safety mechanism such as an ink overheat prevention mechanism and a heater excessive heat generation prevention has not been particularly proposed. In addition, if you add a temperature control element and configure an overheat prevention mechanism,
Therefore, the cost increases, and it is also disadvantageous from the viewpoint of downsizing and compacting of the inkjet head.

In view of this point, an object of the present invention is to provide an ink jet printer provided with a heating mechanism capable of preventing overheating of ink without inviting an increase in cost, and without hindering miniaturization and size reduction. To propose.

[0005]

In order to solve the above problems, an ink jet printer of the present invention has an ink jet head and a heating means for heating ink supplied to ink nozzles of the ink jet head. However, the heating means is characterized by including a PTC thermistor arranged in the vicinity of an ink flow path for supplying ink to the ink nozzle.

The PTC thermistor itself generates heat to function as a heater. When the PTC thermistor self-heats to raise the temperature, the resistance value of the PTC thermistor also increases and the flowing current decreases. This prevents excessive temperature rise of the PTC thermistor itself. By utilizing the automatic temperature control function of such a PTC thermistor, it is possible to prevent the ink from being overheated without using a temperature control element such as a bimetal.

Here, it is preferable that the heating means includes an energization control circuit for controlling energization of the PTC thermistor based on the temperature in the vicinity of the ink flow path.

The energization control circuit includes a control transistor for controlling energization of the PTC thermistor and an NTC thermistor arranged in the vicinity of the ink flow path, and the base terminal voltage of the transistor is the NTC. The thermistor may be configured to be controlled according to the resistance change. Since the NTC thermistor has a characteristic that its resistance value decreases as the temperature rises, it is possible to realize energization control for the PTC thermistor based on the ink temperature with a simple circuit configuration.

Instead of using an NTC thermistor, the energization control circuit uses a switching transistor for turning on and off the energization of the PTC thermistor, a temperature sensor for detecting the temperature in the vicinity of the ink flow path, and a detection of this temperature sensor. A control pulse generating circuit for applying a drive pulse signal having a predetermined duty ratio to the switching transistor based on the result may be provided.

Next, a plurality of PTC thermistors can be arranged in the ink flow path. Particularly, in the case of a color inkjet printer, the ink flow path includes a plurality of ink flow paths for supplying inks of different colors, so that one or a plurality of ink flow paths are provided near each ink flow path. It is desirable to arrange the PTC thermistor.

On the other hand, in the case of a serial type ink jet printer, a head unit incorporating an ink jet head is reciprocally moved in the print width direction by a carriage. Generally, the head unit is provided with a damper chamber for absorbing or mitigating fluctuations in ink supply pressure that occur with reciprocating movement. In this case, the PTC thermistor may be attached to the outer wall portion of the head unit corresponding to the position where the damper chamber is formed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ink jet printer to which the present invention is applied will be described below with reference to the drawings.

(Overall Configuration) FIG. 1 is a schematic configuration diagram showing a main part of an ink jet printer of this example. The inkjet printer 1 of this example is of a serial type, and a head unit 4 is mounted on a carriage 3 that can reciprocate along a guide shaft 2. Ink is supplied to the head unit 4 from an ink tank 5 arranged at a fixed position via a flexible ink tube 6. In the present example, four ink tubes 6-1 to 6-1 are formed from ink tanks 5-1 to 5-4 in which four color inks of cyan, magenta, yellow and black are respectively stored.
It is supplied to the head unit 4 via 6-4. In the head unit 4 of this example, as will be described later, the ink heating mechanisms 70, 70 used to heat the inks of the respective colors and maintain their viscosities in an appropriate state when the environmental temperature is low.
A is attached (see FIGS. 5 and 6).

(Structure of Head Unit) The structure of the head unit 4 will be described prior to the description of the ink heating mechanism.
2 is a perspective view showing the head unit 4 of the present example, FIG. 3 is a sectional view of a portion cut along the line III-III, and FIGS. 4A and 4B are exploded views of the head unit 4, respectively. It is a perspective view.

Explaining with reference to these figures, the head unit 4 of the present example is provided with a rectangular parallelepiped unit cover 11 having an opening on the rear surface side, and the head unit constituent member is inside this unit cover 11. It is stored.

Inside the unit cover 11, from the front side thereof, a head chip 12 (ink jet head), a unit substrate 13, a damper rubber film 14, and a damper presser 15.
The relay board 16 is stacked in this order. Four damper chambers 21 (1) to 21 (4) are defined by the unit substrate 13 and the damper rubber film 14. Unit cover 11, unit substrate 13, damper holder 15
Is a resin molded product, for example.

In each of the damper chambers 21 (1) -21 (4),
Tip portions 22a of the ink supply pipes 22 (1) to 22 (4)
(1) to 22a (4) communicate with each other, and the rear end portions 22b (1) to 22 (1) to 22 (4) of the respective ink supply pipes 22 (1) to 22 (4).
22b (4) has ink tubes 6 (1) through 6
(4) is connected. Each damper chamber 21 (1) -21
(4) communicates with the four ink intake ports 24 (1) -24 (4) formed in the head chip 12 via the ink supply ports 23 (1) -23 (4).

Therefore, the ink tanks 5 (1) -5
The ink from (4) is the ink tubes 6 (1) to 6
(4) and the ink supply pipes 22 (1) to 22 (4) to be supplied to the damper chambers 21 (1) to 21 (4),
From the damper chambers 21 (1) to 21 (4) to the ink supply port 2
3 (1) to 23 (4) and the ink intake port 24
It is supplied to the ink nozzle group of each color via (1) to 24 (4).

The head chip 12 has a flat rectangular parallelepiped shape, and a front surface 12a thereof is an ink nozzle surface, and an ink nozzle row (not shown) for ejecting ink of each color is formed here. The ink nozzle surface 12a is exposed from the front opening 11a of the unit cover 11. Further, flexible wiring boards 25 (1) and 25 (2) for power feeding are drawn out from the respective side surfaces of the head chip 12, and are drawn out rearward along the inside of the side surfaces of the unit cover 11 to form a relay board. It is connected to the rear surface of 16. Head chip drive ICs 26 (1) and 26 (2) are attached to portions of the flexible wiring boards 25 (1) and 25 (2) facing the respective side surfaces of the unit cover 11.

The unit substrate 13 arranged on the rear side of the head chip 12 has a front plate portion 31 to which the head chip 12 is adhered and fixed, and an outer periphery extending from the four peripheral edges of the front plate portion 31 toward the rear at a right angle. It is provided with a side plate portion 32, and a vertical partition plate portion 33 and a horizontal partition plate portion 34 that partition the portion surrounded by the rear surface of the front plate portion 31 and the outer peripheral side plate portion 32 into a cross shape.

The head chip 14 is provided on the front surface of the front plate portion 31.
A mounting recess 31a is formed in which the fitting recess 31a is fitted, and a bonding groove 31b for filling an adhesive is engraved on the bottom surface of the mounting recess 31a. The upper end portion of these bonding groove 31b is the outer peripheral plate portion 32. Is pulled out to the upper surface of. The head chip 12 is fitted into the mounting recess 31a, and the front plate portion 3 is formed by the adhesive filling the adhesive groove 31b.
Adhesively fixed to 1.

A vertical partition plate portion 33 and a horizontal partition plate portion 34 are provided on the rear side of the unit substrate 13 so as to form a vertical partition plate portion 33.
One damper chamber recess 35 (1) to 35 (4) is formed. The recesses have substantially the same shape, and the ink supply ports 23 (1) to 23 (23) formed in the front plate portion 31 are formed on the bottom surface 35a of the damper chamber recesses 35 (1) to 35 (4).
(4) is open. A filter 36 is attached so as to cover the bottom surface 35a.

Next, the damper rubber film 14 is adhesively fixed to the rear surface of the unit substrate 13, that is, the outer peripheral side plate portion 32 and the vertical and horizontal partition plate portions 33, 34. The damper rubber film 14 is supported by a damper retainer 15 attached to the rear surface side. In the damper rubber film 14, the portions 14 (1) to 14 (4) facing the recesses 35 (1) to 35 (4) for damper chambers are made thin.
It is easy to bend in the out-of-plane direction. This damper rubber film 14
The damper chamber recesses 35 (1) to 35 (4) are closed by the thin wall portions 14 (1) to 14 (4) to form the damper chambers 21 (1) to 21 (4). .

The damper retainer 15 includes a rear plate portion 41, an outer peripheral plate portion 42 extending from its four peripheral edges to the front at a right angle, and a front portion surrounded by the front surface of the rear plate portion 41 and the outer peripheral side plate portion 42. A vertical partition plate portion and a horizontal partition plate portion (not shown) for partitioning into a cross shape, and four concave portions 45 facing the damper chambers 21 (1) to 21 (4).
(1) to 45 (4) are formed. These recesses 4
5 (1) to 45 (4) communicate with the atmosphere through the respective vent holes 46 formed in the rear plate portion 41, and the recesses 45
(1) to 45 (4) allow the thin-walled portions 14 (1) to 14 (4) of the damper rubber films to freely bend in the out-of-plane direction.

Here, in the damper presser 15 of this example, four ink supply pipes 22 (1) to 22 (4) are integrally formed at a portion 47 where vertical and horizontal partition plate portions intersect. , A resin molded product, for example. Rear end portions 22b (1) to 2 of the ink supply pipes 22 (1) to 22 (4)
2b (4) are through holes 51 (1) through the relay board 16
The ink tubes 6 (1) to 6 (4) are connected to the ink tubes 6 (1) to 6 (4) by penetrating through 51 (4). On the contrary,
Tip portions 22 of the ink supply pipes 22 (1) to 22 (4)
a (1) to 22a (4) penetrate through the insertion holes 52 (1) to 52 (4) formed in the damper rubber film 14 and project into the damper chambers 21 (1) to 21 (4). ing. The insertion holes 52 (1) to 52 (4) are respectively attached to the damper chambers 21 (1) to 21 (1) to 52 (4).
21 (4) of a predetermined length protruding into
The inner diameter of each ink supply pipe 22 (1) to 22 (22)
The tip end portions 22a (1) to 22a (4) of (4) are formed to have a size slightly smaller than the outer diameter size.

Therefore, the portion of the damper rubber film 14 forming each insertion hole 52 (1) is brought into close contact with the outer peripheral surface of the tip portions 22a (1) to 22a (4) by its own elastic restoring force. And, the space between them is completely sealed.

The head unit 4 of the present example thus constructed discharges ink droplets while moving in the direction indicated by arrow A in FIGS. The pressure fluctuation acting on the ink tube 6 due to the movement is absorbed or alleviated by the four damper chambers 21 (1) to 21 (4) provided in the head unit 4. In addition, the head chip 12 is removed from each damper chamber where the damper effect of the damper chamber cannot be expected.
The lengths of the ink supply ports 23 (1) to 23 (4) reaching the above are extremely short. Therefore, since the pressure acting on this portion is extremely small, the ejection of the ink droplets from the ink nozzle is not adversely affected. Therefore, it is possible to reliably prevent printing defects such as missing dots due to ink pressure fluctuations due to movement of the head unit.

(Ink Heating Mechanism) Next, the ink heating mechanism of this example attached to the head unit 4 thus constructed will be described. First, referring to FIGS. 2 and 4, the unit substrate 13 of the head unit 4 includes a front plate portion 31 to which the head chip 12 is adhesively fixed as described above and four peripheral edges of the front plate portion 31. An outer peripheral side plate portion 32 extending at a right angle toward the publication is provided. Here, on the surfaces of the upper wall portion 321 and the lower wall portion 322 of the outer peripheral side plate portion 32, four PTC thermistors 71, 72, 73, which respectively constitute a heating mechanism for heating the ink of each color, 74 is attached by, for example, a silicone adhesive. These PTC thermistors 71
˜74 are the damper chambers 21 for the inks of the respective colors.
It is attached to the positions corresponding to (1) to 21 (4). Further, one side wall portion 3 in the outer peripheral side plate portion 32
One NTC thermistor 75 is attached to the surface of 23 with a silicon adhesive, for example.

FIG. 5 shows an ink jet printer 1 of this example.
FIG. 3 is a schematic configuration diagram showing an ink heating mechanism 70 mounted on the printer. The ink heating mechanism 70 of this example includes the above-mentioned four P
The TC thermistors 71 to 74 and an energization control circuit 80 that controls energization to these are provided. The energization control circuit 80 includes the above-mentioned NTC thermistor 75, a transistor Tr1 for energization control, and a voltage dividing resistor R. Four
The individual PTC thermistors 71 to 74 are connected in parallel with each other, and one ends thereof are connected to the collector terminal of the transistor Tr1. The emitter terminal of the transistor Tr is grounded, and the divided voltage of the drive voltage Vcc defined by the voltage dividing resistor R and the NTC thermistor 75 is applied to the base terminal as the base terminal voltage.

In the ink jet printer 1 having the heating mechanism 70 of this structure, the NTC thermistor 75 is
It has the characteristic that its own resistance value decreases as the temperature rises. Therefore, when the environmental temperature of the inkjet printer 1 is low, it shows a large resistance value. Therefore, a large divided voltage is used as the base terminal voltage of the transistor Tr.
1, a large current flows through the transistor Tr, and the PTC thermistors 71 to 74 generate heat. As a result, the inks of the respective colors supplied to the ink nozzles via the damper chambers 21 (1) to 21 (4) are heated, so that the inks of the respective colors can be maintained at an appropriate viscosity.

When the environmental temperature of the ink jet printer 1 is high, the NTC thermistor 75 has a small resistance value, and accordingly, the base terminal voltage applied to the transistor Tr1 also becomes small. As a result, the current flowing through each PTC thermistor 71-75 is reduced, and the heat generation is suppressed. When the current falls below a predetermined value, the PTC thermistors 71 to 75 stop generating heat. In addition, since the temperature of each of the PTC thermistors 71 to 74 increases due to self-heating, the self-resistance value increases accordingly.
Performs a self-temperature control operation that automatically suppresses the amount of heat generated.

Therefore, in the ink jet printer 1 of the present embodiment, the ink of each color is properly controlled by the self-temperature control function of the PTC thermistors 71 to 74 and the energization control of the PTC thermistor according to the environmental temperature constituted by the NTC thermistor 75. The heating can be controlled in a wide temperature range.

Here, as the ink heating mechanism 70,
The structure shown in FIG. 6 can be used. Four PTC thermistors 7 in the heating mechanism 70A shown in this figure
The energization control circuit 80A for 1 to 74 includes a switching transistor Tr2, a control pulse generation circuit 81 that controls ON / OFF of the transistor Tr2, and a temperature sensor 82 that detects the environmental temperature of the inkjet printer 1. In the control pulse generation circuit 81, the temperature sensor 8
When the environmental temperature detected by 2 is equal to or higher than the predetermined temperature, the transistor Tr2 is held in the off state.

On the other hand, when the environmental temperature is lower than the predetermined temperature, the control pulse signal Ph having the pulse duty ratio corresponding to the detected environmental temperature is generated to control the on / off of the transistor Tr. That is, the lower the temperature, the wider the control pulse signal having the ON pulse width Phw,
For example, the control pulse signal Ph1 shown in the figure is generated, and when the temperature is high, the control pulse signal having a narrow ON pulse width Pwh, for example, the control pulse signal Ph2 shown in the figure is generated.
As a result, the current corresponding to the pulse duty ratio is
It flows into the C thermistors 71 to 74 and they generate heat,
The ink of each color is heated.

In this embodiment, the desired environmental temperature is set to 3
The temperature is set to 0 ° C to 40 ° C. If the environmental temperature is lower than 30 ° C., the PTC thermistors 71 to 74 are energized to raise the ink temperature. The PTC thermistors 71 to 74 increase in self-resistance value as the temperature rises, suppress the self-heating value, stop the temperature rise at 30 ° C., and keep the temperature constant thereafter. In this way, excessive temperature rise of the PTC thermistor itself is prevented, and therefore excessive heating of the ink is prevented without using a temperature control element.

(Other Embodiments) In the above example, the present invention is applied to a serial type ink jet printer, but the present invention can also be applied to other types of ink jet printers. Of course. Further, it is of course possible to apply the present invention to an inkjet printer that performs monochrome printing.

Further, in the above example, four PTC thermistors are used in order to apply the present invention to the head unit in which the ink flow paths of four color inks for performing color printing are formed. It is also possible to use up to three PTC thermistors as a common heat source for each color of ink. On the contrary, it is also possible to attach two or more PTC thermistors to the ink flow path of each color ink.

[0038]

As described above, in the ink jet printer of the present invention, in order to maintain the viscosity of the ink in an appropriate state without being affected by the fluctuation of the environmental temperature,
The ink is heated using a PTC thermistor. PT
Since the C thermistor has a self-temperature control function in which the self-resistance value increases as the temperature rises and the self-heating amount is suppressed, unlike the case where a general heating element is used, a temperature control element such as a bimetal is used. It is possible to prevent the excessive temperature rise of the ink without adding.

Further, according to the present invention, the PTC thermistor is energized by controlling the energization control so that the resistance change characteristic with temperature change is PTC.
Since the NTC thermistor, which is the opposite of the thermistor, is used, the energization control circuit for the PTC thermistor can be configured with an extremely simple configuration.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a serial type inkjet printer to which the present invention is applied.

FIG. 2 is a perspective view showing a head unit of the inkjet printer shown in FIG.

3 is a cross-sectional view showing a portion of the head unit of FIG. 2 taken along the line III-III.

FIG. 4 is an exploded perspective view showing a state in which the head unit shown in FIG. 2 is disassembled and seen from the front, and an exploded perspective view showing a state seen from the rear side.

5 is a schematic configuration diagram showing a circuit configuration of an ink heating mechanism attached to the inkjet printer of FIG.

6 is a schematic configuration diagram showing another configuration example of an ink heating mechanism attachable to the inkjet printer of FIG.

[Explanation of symbols]

1 inkjet printer 2 Guide shaft 3 carriage 4 head unit 5 ink tank 6 ink tubes 11 unit cover 11a Front opening 12 head chips 12a Ink nozzle surface 13 unit board 14 Damper rubber film 15 Damper holder 16 Relay board 21 (1) -21 (4) Damper chamber 22 (1) to 22 (4) Ink supply pipe 23 (1) to 23 (4) Ink supply port 24 (1) to 24 (4) Ink intake port 321 Unit board upper wall 322 Lower wall portion of unit substrate 323 Side wall of unit board 70, 70A ink heating mechanism 71-74 PTC Thermistor 75 NTC Thermistor 80, 80A energization control circuit Tr1 and Tr2 transistors R resistance 81 Control pulse generator 82 Temperature sensor

Claims (7)

[Claims] 1. An inkjet head, and heating means for heating ink supplied to ink nozzles of the inkjet head, the heating means being in the vicinity of an ink flow path for supplying ink to the ink nozzles. Inkjet printer equipped with a PTC thermistor. 2. The ink jet printer according to claim 1, wherein the heating unit includes an energization control circuit that controls energization of the PTC thermistor based on a temperature near the ink flow path. 3. The energization control circuit according to claim 2, further comprising a control transistor for controlling energization of the PTC thermistor, and an NTC thermistor arranged near the ink flow path. The base terminal voltage of the transistor is the NTC
An ink jet printer characterized by being controlled according to a change in resistance of a thermistor. 4. The switching transistor according to claim 2, wherein the energization control circuit turns on / off energization to the PTC thermistor.
A temperature sensor for detecting the temperature in the vicinity of the ink flow path,
An inkjet printer, comprising: a control pulse generation circuit that applies a drive pulse signal having a predetermined duty ratio to the switching transistor based on the detection result of the temperature sensor. 5. The ink jet printer according to claim 1, which has a plurality of PTC thermistors. 6. The ink flow path according to claim 5, wherein the ink flow path includes a plurality of ink flow paths for supplying inks of different colors, and one or more of the PTC thermistors are provided near each ink flow path. Inkjet printer characterized in that is arranged. 7. The unit substrate according to claim 1, further comprising a head unit in which the inkjet head is incorporated, the head unit including the inkjet head mounted on a front surface thereof. And a damper chamber formed in the unit substrate, and an ink supply port for supplying ink from the damper chamber to the inkjet head, wherein the PTC thermistor defines the damper chamber. An inkjet printer characterized by being attached to an outer wall portion of a substrate.