JP2723998B2 - Image recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image recording apparatus.

[Conventional technology]

2. Related Art A liquid jet recording apparatus (inkjet recording apparatus) that discharges a recording liquid from a recording head to record information such as characters and images is widely known.

Paper and plastic sheets are mainly used as the recording material of this type of apparatus, and in particular, there is an advantage that operation noise is small as compared with other recording methods, and a basic mechanical structure is simple and inexpensive. It has been adopted in various fields as a recording output device such as a computer and a word processor.

However, in this type of apparatus, a change in the ejection state of a recording liquid (hereinafter, referred to as ink) immediately appears as a disturbance in a recorded image. It is important to stabilize the discharge state. On the other hand, when the ink is ejected, the viscosity of the ink inside the ejection opening (hereinafter, referred to as an orifice) of the recording head and the application of thermal energy to the ink,
The bubble formation process and the maximum volume caused by the phase change of the ink greatly depend on the maximum volume. Furthermore, the viscosity change of this ink depends on the time of the non-printing operation and the ink temperature, and the bubble generation process and the maximum volume are also mainly the ink temperature. In the end, it is important to control the temperature of the ink in order to stabilize the ink ejection state.

Therefore, by attaching a heat pipe that conducts heat by a heat working fluid provided inside the recording head and heating or radiating the recording head through the heat pipe according to the temperature of the recording head, the recording head is elongated. A method of controlling the temperature of the recording head uniformly has been considered.

Here, a conventional image recording apparatus in which a heat pipe is mounted on 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 above a recording member 41 conveyed in a direction indicated by an arrow A by a conveying unit (not shown), facing the conveyance direction A. ing.

The recording head 31 has a substrate member 34 on which a plurality of electrothermal conversion elements (not shown) that apply thermal energy to ink are juxtaposed in the longitudinal direction on the support member 3.
A plurality of orifices (not shown) are arranged in the longitudinal direction of the orifice 34, and an ink chamber 35 having a common liquid chamber for supplying ink to each of the orifices through an ink flow path is provided. When the ink chamber 35 is mounted on the substrate member 34, the recording head 31 is configured such that at least one electrothermal conversion element similarly corresponds to each orifice of the ink chamber 35. The common liquid chamber of the ink chamber 35 is appropriately supplied with ink from an ink reservoir (not shown). The recording head 31 drives an electrothermal conversion element in response to an image signal from a printing control unit (not shown), and discharges ink from each orifice to record an image on the recording member 41.

A heat pipe 32 having a length longer than that of the recording head 31 is integrally attached to the recording head 31 on the support member 33 side along the direction in which the electrothermal transducers are arranged. One end is a protrusion protruding to the side of the recording head 31.

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

The above-described temperature sensor 37, heater 38, and fan 40 are connected to a controller 36.
Is a heater according to the temperature detected by the temperature sensor 37.
The input power to the 38 or the fan 40 or the ON-OFF time interval is adjusted to maintain the temperature of the recording head 31 at a predetermined temperature via the heat pipe 32.

[Problems to be solved by the invention]

However, the above-described conventional technique has a problem that during a recording operation,
Since the recording head that generates heat and the heat radiating means attached to the heat pipe and dissipating the heat of the recording head through the heat pipe are located at the same height, the amount of heat generated by the recording head increases and the heat pipe If the maximum heat transfer amount exceeds the maximum heat transfer amount, it becomes difficult to conduct heat from the heat radiating portion to the heat generating portion by the heat pipe, which may cause a dry-out state of the heat pipe, resulting in density unevenness in the recorded image. And it is impossible to form a normal image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described drawbacks of the related art, and has as its object to provide an image recording apparatus capable of preventing a rise in the temperature of a recording head and always performing normal recording.

[Means for solving the problem]

In the image recording apparatus of the present invention, at least one end of a heat pipe attached to a recording head that ejects a recording liquid by thermal energy is provided with a bent portion that is bent upward from a portion attached to the recording head. In some cases, a bent portion of the heat pipe protrudes to the side of the recording head.

[Action]

During the recording operation, the heat 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 radiating means provided at the end of the heat pipe,
Since the liquefied thermal working fluid has the end of the heat pipe provided with the heat dissipating means bent upward from the mounting portion of the recording head, it can easily move to the side of the recording head which is a heat generating portion below. Thus, the movement of the thermal working fluid becomes active, and the heat transport power of the heat pipe is improved.

〔Example〕

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

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

In the image recording apparatus of the present embodiment, a recording head 1 having a heat pipe 2 mounted thereon is disposed above a recording member 11 conveyed in a conveying direction A by a conveying unit (not shown), facing the conveying direction A. Are located.

As shown in FIG. 2, the recording head 1 has a substrate member 4 on which a plurality of electrothermal conversion elements (not shown) are juxtaposed in the longitudinal direction on a support member 3, and further has a substrate member 4. A plurality of orifices 12 are arranged side by side in the longitudinal direction, and an ink chamber 5 having a common liquid chamber for supplying ink to the orifice 12 via an ink flow path is attached. The recording head 1 has at least one electric heat exchange element corresponding to each orifice 12 of the ink chamber 5 in the same manner. Is supplied, the electric heat exchange element is driven by an image signal from a printing control unit (not shown), and the thermal energy discharges ink from each orifice 12 to form an image on the recording member 11. I have.

Further, the recording head 1 has a heat pipe 2 having one end bent and a radiation fin 9 attached to the bent portion.
It is attached integrally.

The length of the heat pipe 2 of the present embodiment is longer than the length of the recording head 1 in the longitudinal direction, and one end of the heat pipe 2 is connected to the recording head 1 when the heat pipe 2 is mounted on the recording head 1. It is bent so as to be located above the mounting portion. Further, as shown in FIG. 3, the heat pipe 2 is provided with a heater 8 at a portion corresponding to a central portion of the recording head 1 and a radiation fin 9 at a bent end. As shown in FIG. 1, the end of the heat pipe 2 to which the heat radiating fins 9 are attached protrudes to the side of the recording head 1, and the heat radiating fins 9 are connected to the recording head 1 of the heat pipe 2. The recording head 1 is mounted so as to be located above the mounting portion.

Also, at the bonding portion between the heat pipe 2 and the recording head 1,
A temperature sensor 7 is provided at a portion corresponding to the central portion of the recording head 1.
In addition, heaters 8 are respectively arranged at portions corresponding to the central portion of the recording head 1 on the side surfaces of the heat pipe 2, and the controller 6 controls the heater 8 or the radiation fins based on the temperature detected by the temperature sensor 7. By driving a fan 10 provided below 9, the recording head 1 is maintained at a predetermined specified temperature.

 Next, the operation of the present embodiment will be described.

First, a switch (not shown) for instructing the start of the recording operation is turned on.
Then, the temperature sensor 7 detects the temperature of the recording head 1. Here, since the printing operation is not performed, the temperature of the printing head 1 has not reached the above-mentioned specified temperature, and the controller 6 drives the heater 8 to heat the printing head 1 via the heat pipe 2. .

The heating from the heater 8 causes the thermal working fluid in the heat pipe 2 to evaporate and spread uniformly in the heat pipe 2 to release 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 condensing part because of its low temperature, and condenses the thermal working fluid that has evaporated and spread, thereby receiving a uniform heat flux. The temperature of the recording head 1 rises uniformly.

Here, FIG. 4 shows actual measurement data obtained by measuring a temperature change in the longitudinal direction of the support member 3 due to the heating at a plurality of locations of the support member 3. FIG. 5 shows actual measurement data obtained using the same size aluminum substrate as the heat pipe 2 instead of the heat pipe 2 under the same conditions.

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 bonding surface between the support member 3 and the heat pipe 2. Here, the measurement of the temperature is performed by the heater 8.
10 cm in the longitudinal direction from the position directly below the heater 8
The operation is performed at three points, that is, at a distant position and a position 20 cm apart from the position directly below the heater 7 in the longitudinal direction.
OFF. The room temperature is 28 ° C., and before the heater 8 is turned on, the temperature of the support member 3 is the same as the room temperature. As is clear from both figures, when the heat pipe 2 of this embodiment is used, it is understood that the ideal heating temperature control of the support member 3 is achieved. That is, when an aluminum substrate is used as the heat pipe, as shown in FIG. 5, a maximum temperature difference of about 10 ° C. occurs in the longitudinal direction, whereas when the heat pipe 2 is used, as shown in FIG. In addition, there is almost no temperature difference in the longitudinal direction. Further, ON-OFF of the heater 8
When the aluminum substrate is used, the temperature vibration of ± 7 to 8 ° C. around the specified temperature (50 ° C.) as shown in FIG. When 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 a recovery means (not shown), and finally the recording member 11
Is transported in the transport direction A by 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 an image signal, and the ink is ejected from the orifice 12. The ejected ink is absorbed when it reaches the opposing recording member 11, and forms an image.

As the image formation progresses, the temperature of the recording head 1 rises due to the heat remaining in the recording head 1 among the thermal energy applied to the ink, and the temperature of the support member 3 also rises. When the temperature detected by the temperature sensor 7 rises from the specified temperature to an allowable amount or more, the controller 6
10 is turned on to send air to the radiating fins 9 to start radiating heat from the recording head 1 via the heat pipe 2. At this time, since the surface of the heat pipe 2 bonded to the support member 3 has a high temperature,
It becomes a so-called evaporating section, and a large amount of heat working fluid evaporates from a portion where the heat flux from the support member 3 is large, that is, a high temperature portion, and a small amount of heat working fluid is small from a portion where the heat flux is small, that is, a low temperature portion. Evaporates and takes the heat amount corresponding to each evaporation amount to turn the thermal working fluid into steam. In addition, a portion where no heat flux flows in becomes a condensing portion, so that the thermal working fluid once turned into steam is condensed, and the latent heat at that time is absorbed by the condensing portion. Since the steam portion of the thermal working fluid has no thermal resistance and heat is transferred instantaneously,
This uniformization of the interface temperature between the thermal working fluid in the evaporating section and the steam section is performed instantaneously, and the heat pipe 2
This interface temperature is maintained substantially uniform even when the heat flux flowing into the substrate has unevenness in place. Therefore, even if the heat flux having unevenness in the location flows into the support member 3 according to the image signal, the temperature of the support member 3 is maintained at a uniform temperature by the action of uniforming the temperature inside the heat pipe 2. .
The excess amount of heat that has been made uniform at the interface temperature is immediately transferred to the radiating fins 9 and condensed to generate heat. The amount of generated heat passes through the radiation fins 9,
The air is transmitted to the air flow sent from the fan 10 and released into the air. At this time, at the end of the heat pipe 2 where the radiation fins 9 are attached, the condensed thermal working fluid returns to a liquid state, and the thermal working fluid in the liquid state is bent at a higher end than the recording head 1. Since it is located at the position, it flows easily through the wick in the heat pipe 2 toward the recording head 1 which is a heat generating portion at a lower position. Then, the heat of the recording head 1 turns into vapor again and is conveyed to the radiating fins 9 to release the heat. The repetition of these operations further improves the heat radiation effect.

FIG. 6 shows actual measurement data when the fan 10 is turned on and off as appropriate and the temperature of the support member 3 is controlled close to the specified temperature by appropriate heat radiation when the recording head is fully discharged, and FIG. Is the same measured data when half the orifice 3 is ejected and the other half is in the non-ejected state. In both figures, the horizontal axis represents time, and the vertical axis represents the interface temperature between the support member 3 and the heat pipe 2. After setting the room temperature to 26 ° C. and heating the support member 3 by the heater 8 to control the temperature to 40 ° C., the time when the discharging operation is started is set as the origin. The fan 10 turns on when the temperature of the support member 3 exceeds 41 ° C., and turns off when the temperature of the support member 3 falls below 41 ° C.

By the way, in the case of full discharge, as shown in FIG. 6, by turning on and off the fan 10 as appropriate, it is possible to maintain a stable and almost constant temperature. Needless to say, in this case, 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 at the difference of about 1 ° C. This temperature difference is due to the thermal resistance of the so-called wick inside the heat pipe 2, and the vapor-thermal working fluid interface has a uniform temperature, but is separated from the wick to the surface of the heat pipe 2. Then, this temperature difference occurs. However, the temperature difference of 1 ° C. between the non-ejection portion and the ejection portion supporting member 3 is a temperature difference that causes almost no problem in image recording, and in this sense, the recording head 1 is radiated through the heat pipe 2. Thus, the temperature of the support member 3, that is, the temperature of the recording head 1 can be ideally and substantially uniformly controlled. During the image recording operation, the controller 6 turns on and off the fan 10 as appropriate according to the temperature detected by the temperature sensor 7 to stabilize the temperature of the support member 3 almost uniformly near the specified temperature as described above. Can be held.

As described above in detail, the heat pipe 2 is mounted on the recording head 1, and the recording head 1 is heated or radiated through the heat pipe 2 in accordance with the temperature of the recording head 1, so that a long recording head is provided. 1 can be uniformly maintained at a constant temperature. As a result, the ejection state of the ink is remarkably stabilized, and the stability of the image is greatly improved.

Further, in this embodiment, the radiation fin 9 and the fan
Because the installation position of 10 is outside the recorded image area, fan 10
Strong air flow from the image area can be separated from the image area, heat can be dissipated without disturbing the flight path of the ejected ink,
This 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.

Further, the heat pipe having the shape as shown in the present embodiment may be formed by a bent pipe, or may be formed by forming a straight type and then bending.

As described above, the present invention brings about an excellent effect particularly in a recording head and a recording apparatus of a bubble jet method among ink jet recording methods. Regarding the typical configuration and principle, it is preferable to use the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. This method can be applied to both so-called on-demand type and continuous type. In particular, in the case of an on-demand image, an electric device arranged corresponding to a sheet or liquid path holding a liquid (ink) is used. By applying at least one drive signal to the heat exchanger which provides a rapid temperature rise corresponding to the recording information and obtains nucleate boiling, the heat exchanger generates heat energy, and the thermal action of the recording head This is effective because nucleate boiling is caused on the surface, and as a result, bubbles in the liquid (ink) can be formed in one-to-one correspondence with the drive signal. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the gas, at least one liquid is formed.

When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,434,262 are suitable. If the conditions described in the specification of US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed. As the configuration of the recording head, in addition to the combination configuration of the discharge port and the liquid path electric heat exchanger (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above specification, the heat acting portion is bent. A configuration using U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration arranged in a region where the region is located, is also included in the present invention. In addition, JP-A-59-123670 discloses a configuration in which a slit common to a plurality of electric heat exchangers is used as a discharge unit of the electric heat exchanger, and an opening that absorbs pressure waves of heat energy is provided in the discharge unit. The effect of the present invention is also effective as a configuration based on JP-A-59-138461 which discloses a configuration corresponding to the above. Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus,
As disclosed in the above specification, any combination of a plurality of recording heads may be used to satisfy the length or a single recording head integrally formed. The above effects can be more effectively exerted. In addition, it is provided integrally with a replaceable chip-type recording head or the recording head itself, which can be electrically connected to the apparatus main body and supplied with ink from the apparatus main body by being attached to the apparatus main body. The present invention is also effective when a cartridge type recording head is used. Further, it is preferable to add recovery means for the printhead provided as a configuration of the printing apparatus, preliminary auxiliary means, and the like, since the effects of the present invention can be further stabilized. If these are specifically raised, capping means for the recording head, cleaning means, pressurizing or suction means, preheating means using an electric heat exchanger or another heating element or a combination thereof, and separate from recording It is also effective to perform a preliminary ejection mode in which the ejection is performed to perform stable printing. Further, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, and may be configured integrally with a printing head or by a combination of a plurality of printing heads. The present invention is very effective for an apparatus having at least one of the full colors.

〔The invention's effect〕

As described above, the present invention has the following effects.

(1) Insert the end of the heat pipe attached to the recording head
Since the heat radiating means is provided at the bent portion by being bent upward from the portion to be attached to the recording head, the movement of the thermal working fluid from the heat radiating portion to the recording head which becomes the heat generating portion during the recording operation can be easily performed. As a result, the heat transport amount of the heat pipe can be increased.

(2) By increasing the heat transport amount of the heat pipe,
Since the uniformity of the movement of the thermal working fluid is improved, the temperature control effect such as heating or heat radiation of the recording head through the heat pipe is improved, and the recording head can be controlled with high accuracy and stability. , The ink discharge state is stabilized, and high-quality image recording without density unevenness can be performed.

(3) When the bent portion of the heat pipe protrudes to the side of the recording head, the heat radiating means is located outside the recording liquid discharge area of the recording head. Therefore, the flight path of the recording liquid by the blower included in the heat radiating means. And the reliability of image formation is further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the image recording apparatus of the present invention, FIG. 2 is a perspective view showing the configuration of a recording head 1, and FIG. 3 is a heat pipe 2 used in the image recording apparatus of FIG. FIG. 4 is a diagram showing a temperature change of the heat pipe 2 at the start of recording of the image recording apparatus shown in FIG. 1, and FIG. 5 is an aluminum substrate as a heat pipe in the image recording apparatus shown in FIG. FIG. 6 is a diagram showing a temperature change when using
FIG. 7 is a diagram showing a temperature change when the ejection is performed from all the orifices of the recording head 1 in the image recording apparatus shown in FIG. 1. FIG. 7 is a diagram showing a half orifice of the recording head 1 in the image recording apparatus shown in FIG. FIG. 8 is a perspective view showing a conventional example in which the temperature is obtained when the ink is discharged from the nozzle. DESCRIPTION OF SYMBOLS 1 ... Recording head, 2 ... Heat 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.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Yanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshihiko Takahashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Kosuke Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Makoto Takamiya 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

(57) [Claims] At least one end of a heat pipe attached to a recording head for discharging a recording liquid by thermal energy,
An image recording apparatus, comprising: a bent portion that is bent upward from a portion attached to the recording head; and a heat radiating unit is provided in the bent portion. 2. The image recording apparatus according to claim 1, wherein the bent portion of the heat pipe projects to the side of the recording head.