JPH03133654A - Image recorder - Google Patents

Abstract

PURPOSE:To prevent the temperature increase of a recording head by a method wherein a part bending upward in the loading part of a heat pipe to a recording head is provided on at least one end of the heat pipe loaded on the recording head, and a head radiation means is provided on the bending part. CONSTITUTION:A controller 6 drives a heater 8, and the heater 8 heats a recording head 1 through a heat pipe 2. When a temperature detected by a temperature sensor 7 becomes higher than a specified temperature by more than an allowable value, the controller 6 turns ON a fan 10 to feed air to a heat radiation fin 9, thereby starting release of heat from the recording head 1 through the heat pipe 2. A condensed thermally-operative fluid is returned to a liquid state at the end part of the head pipe 2 on which the heat radiation fin 9 is mounted. The liquefied thermally-operative fluid is easily flowing toward the recording head 1, which is disposed downward as a heating part, through a wick in the heat pipe 2 because the end part of the heat pipe is bent to be disposed higher than the recording head 1.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image recording device.

(Prior Art) Liquid jet recording devices (inkjet recording devices) that record information such as characters and images by ejecting recording liquid from a recording head are widely known.

This type of device mainly uses paper, plastic sheets, etc. as the recording material, and has the advantage that it has lower operating noise than other recording methods, and its basic structure is simple and inexpensive. It has been adopted in various fields as a recording/output device for computers, word processors, etc.

However, in this type of device, changes in the ejection state of the recording liquid (hereinafter referred to as ink) immediately appear as disturbances in the recorded image, so in order to perform stable image recording, it is necessary to It is important to stabilize the discharge condition. On the other hand, the ink ejection state is determined by the viscosity of the ink inside the ejection opening (hereinafter referred to as orifice) of the recording head and the bubble formation process caused by the phase change of the ink when thermal energy is applied to the ink. In addition, the viscosity change of this ink largely depends on the non-recording operation time and the ink temperature, and the bubble generation process and maximum volume also mainly depend on the ink temperature. In order to stabilize the ejection state, it is important to control the temperature of the ink.

Therefore, a heat pipe that conducts heat using a thermally working fluid provided inside the recording head is attached to the recording head, and the recording head is heated or radiated via the heat pipe according to the temperature of the recording head. A method of uniformly controlling the temperature of the recording head has been considered.

Here, a conventional image recording apparatus in which a beat pipe is attached to a recording head will be described with reference to FIG.

In this image recording apparatus, a recording head 31 equipped with a heat pipe 32 is disposed in the direction F of a recording member 41 that is conveyed in the direction of arrow A by a conveyance means (not shown), facing the conveyance direction A. has been done.

In the recording head 31, a substrate member 34 in which a plurality of electrothermal transducers (not shown) that apply thermal energy to ink are arranged in parallel in the longitudinal direction is adhered to the support member 3. An ink chamber 3 including a common liquid chamber in which a plurality of orifices shown are arranged in parallel in the longitudinal direction and ink is supplied to each of the orifices through an ink flow path.
5 is installed. In this recording head 31, when the ink chamber 35 is attached to the substrate member 34F, the ink chamber 35
At least one electrothermal conversion element corresponds to each of the orifices 5 in the same manner. Ink is appropriately supplied to the common liquid chamber of the ink chamber 35 from an ink reservoir (not shown). The recording head 31 records an image on the recording member 41 by ejecting ink from each orifice by driving an electrothermal transducing element by an image signal from a printing control section (not shown).

Further, a heat pipe 32 having a longer length than the recording head 31 is integrally attached to the recording head 31 on the supporting member 33 side along the direction in which the electrothermal transducer elements are arranged. One end is a protrusion that protrudes to the side of the recording head 31.

A heater 38 is attached to the heat pipe 32 at a portion corresponding to the center of the recording head 31, and a heat radiation fin 39 is attached to the protruding portion.
9 and the recording head 31 are located at the same height. The heat radiation fins 39 radiate heat from the recording head 31 transmitted via the heat pipe 32 by blowing air from a fan 40 installed below. Further, a temperature sensor 37 for detecting the temperature of the recording head 31 is attached to a portion where the heat pipe 32 is attached to the recording head 31 and corresponds to the center of the recording head 31 .

Temperature sensor 37, heater 38 and fan 40 described above
is connected to a controller 36, which adjusts the human power to the heater 38 or the fan 40 or the ON-OFF time interval according to the temperature detected by the temperature sensor 37, and records it via the heat pipe 32. The configuration is such that the temperature of the head 31 is maintained at a predetermined temperature.

[Problem to be solved by the invention]

However, in the conventional technology described above, during recording operation,
It is attached to a recording head and a heat nozzle that generate heat.
Since the heat dissipation means for dissipating the heat of the recording head via the heat pipe is located at the same height, if the heat generation amount of the recording head increases and exceeds the maximum heat transfer amount of the heat pipe, the heat pipe This makes it difficult for heat to be conducted from the heat dissipating part to the heat generating part, resulting in a dry-out condition of the beat pipe, which has the drawback of causing density unevenness in the recorded image and preventing normal image formation. .

The present invention has been made in view of the drawbacks of the prior art, and an object of the present invention is to provide an image recording apparatus that can prevent the temperature of the recording head from increasing and always perform normal recording.

[Means to solve the problem]

In the image recording apparatus of the present invention, at least one end of a beat pipe attached to a recording head that discharges recording liquid using thermal energy is provided with a bent portion bent in the E direction from a portion attached to the mud storage recording head. The bent portion is equipped with a heat dissipation means, and there is also one in which the bent portion of the beat pipe protrudes to the side of the recording head.

(Function) During recording operation, when the thermal working fluid in the heat pipe, which is vaporized by the heat of the recording head that generates heat, is condensed and liquefied by the heat dissipation means provided at the end of the heat pipe, the liquefied thermal working fluid Since the end of the heat pipe provided with the heat dissipation means is bent upward from the part where it is attached to the recording head, it easily moves downward toward the recording head, which becomes the heat generating part, and the thermal activation Fluid movement becomes active and the heat transport ability of the heat pipe improves.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The image recording apparatus of the present embodiment includes a recording head 1 in which a heat pipe 2 is mounted on the side of a recording member 11 that is conveyed in a conveying direction A by a conveying means (not shown) and facing the conveying direction A. is located.

In the recording head 1, as shown in FIG. 2, a substrate member 4 on which a plurality of electrothermal transducers (not shown) are arranged in parallel in the longitudinal direction is adhered to a support member 3. ,
A plurality of orifices 12 are arranged in parallel in the longitudinal direction, and an ink chamber 5 having a common liquid chamber for supplying ink through an ink flow path is attached to the orifices 12. In this recording head 1, at least one electrothermal transducer element corresponds to each orifice 12 of the ink chamber 5 in the same way, and a common liquid chamber of the ink chamber 5 is provided with ink as appropriate from an ink reservoir (not shown). is supplied, and the electrothermal transducer is driven by an image signal from a print control unit (not shown), and the thermal energy is used to drive each orifice! Discharge ink from 2"C
It is configured to form an image on the recording member 11.

Roughly speaking, a beat pipe 2 having one end bent and a heat dissipation fin 9 attached to the bent portion is integrally attached to the recording head 1.

The beat pipe 2 of this embodiment has a length longer than the length in the longitudinal direction of the recording head 1, and one end thereof is connected to the heat pipe 2.
When the heat pipe 2 is attached to the recording head 1, it is bent so as to be located above the attachment portion of the heat pipe 2 to the recording head 1. Furthermore, this heat pipe 2 has 'fS3
As shown in the figure, a heater 8 is attached to a portion corresponding to the center of the recording head 1, and a heat radiation fin 9 is attached to the bent end. As shown in FIG. 1, this beat pipe 2 has an end side to which a heat dissipation fin 9 is attached protrudes to the side of the recording head 1, and the heat dissipation fin 9 extends from the heat pipe 2 to the recording head 1. 4 above the installed HfR5
It is attached to the recording head 1 so that the

In addition, a temperature sensor 7 is installed at the bonded portion between the heat pipe 2 and the recording head 1 at a portion corresponding to the center of the recording head 1, and a temperature sensor 7 is installed at a portion corresponding to the center of the recording head 1 at the side surface of the beat pipe 2. A controller 6 drives a fan 10 provided below the heater 8 or the radiation fins 9 to move the recording head 1 to a predetermined position based on the temperature detected by the temperature sensor 7. The structure is such that the temperature is maintained at the specified temperature.

Next, the operation of this embodiment will be explained.

First, turn on a switch (not shown) that instructs the start of recording operation.
Then, the opening sensor 7 detects the temperature of the recording head 1. Here, since the recording operation is not performed,
The temperature of Recording Rad 1 has not reached the specified temperature of Moeji,
A controller 6 drives a heater 8 to heat the recording head 1 via a heat pipe 2.

The heat from the heater 8 evaporates the thermal working fluid within the heat pipe 2 and spreads uniformly within the beat pipe 2, releasing latent heat. At this time, the adhesive surface side of the heat pipe 2 with the support member 3 of the recording head 1 becomes a condensation part due to its low temperature, condenses the thermal working fluid that has evaporated and spread, and receives a uniform heat flux. Recording head! temperature rises uniformly.

Here, FIG. 4 shows actual measurement data obtained by measuring temperature changes in the longitudinal direction of the support member 3 due to this heating at a plurality of locations on the support member 3. Furthermore, the fifth section shows actual measurement data obtained under the same conditions using an aluminum substrate of the same size as the heat pipe 2 instead of the beat vibrator 2.

In both figures, the horizontal axis represents the time since the heater 8 was turned on, and the vertical axis represents the temperature of the adhesive surface between the support member 3 and the beat vibe 2. Here, temperature measurement is performed using heater 8.
10 in the longitudinal direction from the position directly below the heater 8.
The temperature was set at 50°C, and the heater 8 was adjusted appropriately so that the temperature at the position directly below the heater was 50°C. 0N-OFFL. The room temperature is 28° C., and the temperature of the support member 3 is the same as the room temperature before the heater 8 is turned on. As is clear from both figures, when the beat vibrator 2 of this example is used, it can be seen that ideal heating temperature control of the support member 3 is achieved. That is, when an aluminum substrate is used as a heat pipe, as shown in Fig. 5, a maximum temperature difference of about 10°C occurs in the longitudinal direction, whereas when heat pipe 2 is used, as shown in Fig. 4, , there is almost no temperature difference in the longitudinal direction. Furthermore, when an aluminum substrate is used, the temperature fluctuation that occurs when the heater 8 is turned OFF is approximately 7°C around the specified temperature (50°C), as shown in Figure 5.
While the temperature vibration shows a temperature vibration of ~8°C, when the Beat Vibe 2 is used, the vibration can be suppressed to within ±1°C as shown in FIG.

As described above, when the temperature of the recording head 1 reaches the specified temperature, the amount of ink inside the orifice 12 is adjusted by the recovery means (not shown), and the recording member 11 is finally heated.
is transported in the transport direction A by a transport means (not shown).

When the recording member 11 reaches a position facing the orifice 12 of the recording head 1, thermal energy is applied to the ink according to the image signal, and the ink is ejected from the orifice 12. When the ejected ink reaches the opposing recording member 11, it is absorbed and forms an image.

Now, as this image formation progresses, the temperature of the recording head 1 increases due to the heat remaining in the recording head 1 out of the thermal energy applied to the ink, and the temperature of the support member 3 also increases. Then, when the temperature detected by the temperature sensor 7 rises from the specified temperature to more than the allowable amount, the controller 6 turns the fan 0 ONL/ to send air to the heat radiation fins 9, and causes the heat radiation of the recording head 1 through the beat vibe 2. Start. At this time,
Since the adhesive surface of the heat pipe 2 and the support member 3 has a high temperature, it becomes a so-called evaporation part, and a large amount of thermal working fluid evaporates from the part where the heat flux from the support member 3 is large, that is, the high temperature part, and the heat flow is reduced. A small amount of the thermal working fluid evaporates from the portion where the inflow of the bundle is small, that is, the low temperature portion, and the amount of heat corresponding to the amount of evaporation is taken away from each portion to turn the thermal working fluid into steam.

Further, since the portion where no heat flux flows in at all becomes a condensing portion, the thermal working fluid that has become vapor is condensed, and the latent heat at that time is absorbed in the condensing portion. The steam part of the thermal working fluid has no thermal resistance and heat transfer occurs instantaneously.
This equalization of the interface temperature between the thermal working fluid and the steam section in the evaporation section is instantaneous, and even if the heat flux flowing from the support member 3 to the beat vibe 2 is uneven, this interface temperature is almost uniform. is maintained. Therefore, even if a heat flux with unevenness flows into the support member 3 according to the image signal, the support member 3 will be kept at a uniform temperature by the action of temperature equalization inside the heat pipe 2. Become. The amount of heat remaining after uniformizing this interface temperature is
It is instantly transported to the heat radiation fins 9 and condensed to generate heat. The generated at passes through the radiation fins 9, is transmitted to the air flow sent by the fan 10, and is emitted into the air.

At this time, at the end of the heat pipe 2 to which the radiation fins 9 are attached, the condensed thermal working fluid returns to a liquid state, and the end of the liquefied thermal working fluid is bent and the recording head 1
Since it is located at a higher position, it easily flows through the wick in the heat pipe 2 toward the recording head 1, which is located at a lower position and serves as a heat generating section. Then, the heat from the recording head 1 transforms into steam and is carried toward the radiation fins 9 to release the heat, and by repeating these steps, the heat radiation effect is further improved.

Figure 6 shows actual measurement data when the recording head is fully ejected, the fan 10 is turned 0N-OFF as appropriate, and the temperature of the support member 3 is controlled near the specified temperature by appropriate heat dissipation. Discharge half of orifice 3 of t-do 1,
This is similar actual measurement data when the other half is in a non-ejection state. In both figures, the horizontal axis is time, and the vertical axis is the interface temperature between the support member 3 and the heat pipe 2. After heating the support member 3 with the heater 8 and controlling the room temperature to 40°C, the origin is set at the time when the discharge operation is started. fan 10
turns on when the temperature of the support member 3 exceeds 41°C, and
It turns off at temperatures below ℃.

Now, in the case of full discharge, as shown in FIG. 6, by turning off the fan 10 on and off, the temperature can be kept more stably at a constant temperature. Of course, in this case, it goes without saying that there is almost no temperature unevenness in the longitudinal direction. Next, in the case of half discharge and half non-discharge, as shown in FIG. 7, the temperature of the support member 3 is stably maintained with a difference of about 1°C. This temperature difference is due to the heat resistance of the so-called wick inside the beat pipe 2, and the steam
Although the thermal working fluid interface is at a uniform temperature, a temperature difference occurs across the wick to the surface of the beat pipe 2. However, this temperature difference of 1°C between the non-ejection part and the support member 3 of the ejection part is a temperature difference that is almost negligible in image recording, and in this sense, the heat dissipation of the recording head 1 is performed through the beat pipe 2. If this is done, the temperature of the support member 3, that is, the recording head 1, can be ideally controlled almost uniformly. During the image recording operation, the controller 6 turns the fan 10 ON and OFF as appropriate according to the temperature detected by the temperature sensor 7, so that the temperature of the support member 3 is almost uniformly maintained near the specified temperature as described in F. can be held stably.

As described in detail below, by attaching the heat pipe 2 to the recording head 1 and heating or dissipating heat from the recording head 1 via the heat pipe 2 according to the temperature of the recording head 1, long length recording is possible. It becomes possible to maintain the head 1 at a uniform and constant temperature. As a result, the state of ink ejection is dramatically stabilized, and the stability of images is greatly improved.

Furthermore, in this embodiment, the radiation fins 9 and the fan 1
Since the installation position of fan 0 is outside the recording image area, fan 1
It is possible to separate the strong airflow from the image area from the image area, and it is possible to dissipate heat without disturbing the flight path of the ejected ink, which also has the effect of increasing the stability of the image.

In this embodiment, one end is bent upward, but both ends may be bent upward.

In addition, the beet pipe shaped like the one shown in this example is
It may be made with a bent vibrator, or a straight type may be made and then bent.As described above, the present invention has excellent effects particularly in bubble jet recording heads and recording devices among inkjet recording methods. It brings about For its typical configuration and principle, see US Patent No. 472312, for example.
Preferably, the method is carried out using the basic principle disclosed in the specification of No. 9 and the specification of No. 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type, but especially in the case of the on-demand type, the ink is placed in correspondence with the sheet holding the liquid (ink) and the liquid path. By applying at least one drive signal to the electrothermal transducer in the recording head that corresponds to recorded information and that causes a rapid temperature rise to obtain nucleate boiling, the electrothermal transducer generates thermal energy and the recording head is heated. This is effective because it causes nucleate boiling on the heat acting surface, resulting in the formation of bubbles in the liquid (ink) in one-to-one correspondence with this drive signal. Due to the growth and contraction of this gas, the liquid (ink 2) is ejected through the ejection opening to form at least one liquid.

If this drive signal is in the form of a pulse, bubble growth and contraction will occur immediately and appropriately, so liquids with particularly excellent responsiveness (
Ink) can be ejected, which is more preferable. As this pulse-shaped drive signal, those described in US Pat. No. 4,463,359 and US Pat. No. 4,345,262 are suitable. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed. In addition to the configuration of the recording head that is a combination of ejection ports and liquid path electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specification, the heat acting part is bent. The present invention also includes configurations using the specifications of US Pat. No. 4,558,333 and US Pat. No. 4,459,600 which disclose configurations in which the device is disposed in the area where the device is located. In addition, Japanese Patent Laid-Open No. 123670 of 1981 discloses a configuration in which a slit common to a plurality of electrothermal converters is used as a discharge part of the electrothermal converter, and a discharge part is provided with an opening that absorbs pressure waves of thermal energy. The effects of the present invention are also effective even with a structure based on Japanese Patent Application Laid-Open No. 138461 of 1982, which discloses a structure corresponding to the above. Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by a recording apparatus, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects. In addition, by being attached to the device body,
Even when using a replaceable chip-type recording head that allows electrical connection to the device main body and supply of ink from the device main body, or a cartridge-type printhead that is integrated into the recording head itself. The present invention is effective. Further, it is preferable to add recovery means, preliminary auxiliary means, etc. for the recording head provided as a component of the recording apparatus to the present invention, since the effects of the present invention can be further stabilized. Specifically, these include a capping means, a cleaning means, and a cleaning means for the recording head.
In order to perform stable recording, it is also possible to use pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof, and a preliminary discharge mode that performs discharge other than recording. It is dynamic. Furthermore, the recording mode of the recording device is not limited to a recording mode for only mainstream colors such as black, but may also be configured by integrally configuring the recording head or by a combination of multiple heads, or by using multiple colors of different colors or by mixing colors. The present invention is also extremely effective for devices equipped with at least one full color image.

(Effects of the Invention) As explained above, the present invention has the following effects.

(1) The end of the heat pipe attached to the recording head,
Since it is bent upward from the part attached to the recording head and the heat radiating means is provided in the bent part, the thermal working fluid can easily move from the heat radiating part to the recording head which becomes a heat generating part during recording operation. , it is possible to increase the heat transport amount of the heat pipe.

(2) By increasing the heat transport amount of the heat pipe,
This improves the uniformity of the movement of the thermal working fluid, which improves the temperature control effect of heating the recording head or dissipating heat through the heat pipe, making it possible to control the temperature of the recording head with high precision and stability. Since the temperature difference between the ink and the ink is eliminated, the ink ejection condition becomes stable, and it is possible to record high-quality images without any unevenness.

(3) If the bent portion of the heat pipe protrudes to the side of the recording head, the heat dissipation means will be located outside the recording liquid discharge area of the recording head, so the flight path of the recording liquid by the blower included in the heat dissipation means will be This eliminates the disturbance in image formation, further improving the reliability of image formation.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the image recording device of the present invention, FIG. 2 is a perspective view showing the configuration of a recording head l, and FIG. 3 is a heat pipe 2 used in the image recording device of FIG. FIG. 4 is a diagram showing the temperature change of the beat vibrator 2 at the start of recording in the image recording apparatus shown in FIG. 1, and FIG.
6 is a diagram showing temperature changes when an aluminum substrate is used as a beat pipe in the image recording apparatus shown in FIG. 7 is a diagram showing the temperature when ejecting from half the orifices of the recording head 1 in the image recording apparatus shown in FIG. 1, and FIG. 8 is a perspective view showing the conventional example. DESCRIPTION OF SYMBOLS 1... Recording head, 2... Beat pipe, 3... Support member, 4... Substrate member 5... Ink chamber, 6... Controller. 7... Temperature sensor, 8... Heater, 9... Radiation fin, 10...
-Fan, 11... Recorded member, 12... Orifice.

Claims (1)

[Scope of Claims] 1. At least one end of a heat pipe attached to a recording head that discharges recording liquid using thermal energy is provided with a bent portion bent upward from the portion attached to the recording head, and the bent portion An image recording device comprising a heat dissipation means. 2. The image recording apparatus according to claim 1, wherein the bent portion of the heat pipe projects laterally of the recording head.