JP4997904B2 - Image recording head and image forming apparatus - Google Patents

Description

  The present invention relates to an image recording head that exposes a photosensitive member to form a latent image with a plurality of light emitting elements, and an image forming apparatus including the image recording head.

  As an image forming apparatus, an image forming apparatus including an image recording head, a photosensitive member, a charging device, a developing device, a transfer device, and a fixing device in which a plurality of light emitting elements such as LEDs are arranged in the main scanning direction is well known.

  In this image forming apparatus, the charging device uniformly charges the surface of the photoconductor, the image recording head emits the LED, and the charged photoconductor is exposed to form an electrostatic latent image. The developing device attaches toner to the electrostatic latent image to form a toner image on the photoreceptor, and the transfer device transfers the toner image to a recording medium. The transferred toner image is fixed on a recording medium by a fixing device.

  Here, when the image recording head causes the LED to emit light, the substrate on which the LED is arranged thermally expands due to the heat generated by the light emission, and the exposure position (dot position) deviates from a predetermined exposure position in the main scanning direction. is there.

  In a tandem type multicolor image forming apparatus provided with an image recording head for each color, this exposure position shift appears as a color shift. For this reason, correction is necessary to make the print widths of the image recording heads substantially coincide.

  In Patent Document 1, preheating means for generating heat in advance is provided at a predetermined location, and after the heat is generated in advance on a base on which a recording element array in which a plurality of recording elements are formed is arranged by the preheating means, the recording element is It comes to drive. For this reason, when heat is generated by driving the recording element, it is possible to prevent the base from newly extending. Thereby, the accuracy of the arrangement of the recording elements can be increased, and the occurrence of dot deviation can be prevented.

On the other hand, in recent years, there has been a demand for further shortening of the initialization time when the apparatus is started up, and a high-output heating means is required. However, there is a limit to disposing high-power heating means as image recording heads become smaller.
JP 2002-370400 A

  In view of the above-described facts, an object of the present invention is to provide an image recording head and an image forming apparatus capable of correcting the exposure position in the main scanning direction and shortening the initialization time when starting the apparatus. .

According to the first aspect of the present invention, in the image recording apparatus , a light emitting element that exposes a photosensitive member to form a latent image, a substrate on which a plurality of the light emitting elements are arranged along a main scanning direction, and the substrate A plurality of image recording heads having heating means for heating the substrate disposed in parallel, and heating auxiliary means connected in parallel to the heating means for auxiliary heating of the substrate, and driving these image recording heads An image recording head driving unit, wherein the image recording head driving unit is an image recording head having the largest dot position deviation amount along the main scanning direction of the substrate per unit temperature among the plurality of image recording heads. The heating auxiliary means of each image recording head is controlled on the basis of the amount of positional deviation .

  In the first aspect of the present invention, the heating means for heating the substrate and the heating auxiliary means for auxiliary heating of the substrate are connected in parallel. By using the heating means and the heating auxiliary means, the calorific value can be increased as compared with the case where only the heating means is used.

For this reason, the temperature of the substrate can be quickly raised, and the deviation of the exposure position of the light emitting element in the main scanning direction can be corrected in a short time. That is, it is possible to shorten the time required to bring the image recording head to a predetermined temperature when the apparatus is activated, that is, the so-called initialization time (initial time). Further, it is not necessary to perform temperature control for the image recording head having the largest dot position deviation amount per unit temperature.

According to a second aspect of the present invention, in the image recording apparatus according to the first aspect, each image recording head opens and closes a parallel circuit composed of the heating means and the heating auxiliary means, thereby heating means and heating auxiliary means. in, or switching means for supplying a current to the heating means, and detecting a time of flowing a current to the heating means and the heating aid, and characterized in that it comprises a control means for causing the switching operation to said switching means To do.

In the invention described in claim 2, the parallel circuit composed of the heating means and the heating auxiliary means is switched by the switching means to be opened and closed. And when the parallel circuit is closed,
In the state where the current flows through the heating means and the heating auxiliary means and the parallel circuit is opened, the current flows only through the heating means.

  Then, in a parallel state of the heating means and the heating auxiliary means (closing the parallel circuit), when a predetermined time elapses when a current is passed through the heating means and the heating auxiliary means, the switching means is switched by the control means, and the parallel circuit is changed. Open and let the current flow only through the heating means.

  Since it is necessary to bring the image recording head to a predetermined temperature in a short time after the start of the apparatus, the heating means and the heating auxiliary means are connected in parallel until the image recording head reaches the predetermined temperature, and current is supplied to the heating means and the heating auxiliary means. To quickly raise the temperature of the substrate.

According to a third aspect of the present invention, in the image recording apparatus according to the second aspect , each image recording head includes a temperature detecting unit that detects the temperature of the substrate , and the control unit detects the temperature of the substrate. A temperature detection unit is provided on the substrate, and the control unit causes the switching unit to perform a switching operation in accordance with the temperature detected by the temperature detection unit.

  In the invention described in claim 3, temperature detecting means for detecting the temperature of the substrate is provided. When the image recording head reaches a predetermined temperature, it is necessary to maintain this predetermined temperature. Therefore, a switching operation (opening / closing of the parallel circuit) is performed by the switching unit according to the temperature detected by the temperature detection unit, and the heating unit And an electric current flows into a heating auxiliary means, or an electric current flows only into a heating means.

According to a fourth aspect of the present invention, in the image recording apparatus according to any one of the first to third aspects, the heating auxiliary means is a pseudo element having a resistance.

  In the invention described in claim 4, a pseudo element such as a capacitor having resistance and a resistor is disposed as a heating auxiliary means. In this way, since the pseudo element is used to connect in parallel with the heating means, it is possible to reduce the cost when a separate heater is provided.

The invention according to claim 5 is the image recording apparatus according to any one of claims 1 to 3, wherein the heating auxiliary means is a heater. In this case, for example, when a dew condensation prevention heater is used in the image recording head, the dew condensation prevention heater can also be used as a heating auxiliary means by connecting in parallel with the heater for heating the substrate.

  According to a sixth aspect of the present invention, in the image forming apparatus, the image recording head according to any one of the first to fifth aspects is provided.

  Since the present invention has the above-described configuration, the exposure position in the main scanning direction can be corrected, and the initialization time when the apparatus is activated can be shortened.

  Hereinafter, an example of an embodiment according to an image forming apparatus including the image recording head of the present invention will be described with reference to the drawings.

  First, the overall configuration of a tandem color printer as an image forming apparatus according to the present invention will be described. FIG. 1 is a diagram illustrating a schematic configuration of a tandem color printer according to the present embodiment.

  As shown in FIG. 1, in the tandem color printer 10, an intermediate transfer belt 40 composed of an endless belt is supported by a plurality of rolls 42 with a predetermined tension. On the intermediate transfer belt 40, cyan (C), magenta (M), yellow (Y), and black (K) are supported along the belt running direction (counterclockwise direction in FIG. 1). The image forming units 44C, 44M, 44Y, and 44K are sequentially arranged.

  Each image forming unit 44C, 44M, 44Y, 44K has a photosensitive drum (photosensitive body) 46 that rotates in one direction (clockwise direction in FIG. 1), and around each photosensitive drum 46 is a drum. A charger 50, a print head 12, a developing device 52, a primary transfer roll 54, and a cleaner 48 are sequentially arranged along the rotation direction.

  With the above configuration, in each of the image forming units 44C, 44M, 44Y, and 44K, the surface of the photosensitive drum 46 is uniformly charged by the charger 50, and the surface of the photosensitive drum 46 is exposed by the print head 12. An electrostatic latent image is formed. The electrostatic latent image formed by the print head 12 forms a toner image by the developing device 52 and is transferred to the intermediate transfer belt 40 by the primary transfer roll 54. The toner remaining on the photosensitive drum 46 is removed by the cleaner 48. Note that sub-scanning is performed by each photosensitive drum 46, and main scanning is performed by the print head 12.

  Further, a misregistration amount detection sensor 33 that detects misregistration amounts of the colors C, M, Y, and K is disposed on the downstream side of the black (K) image forming unit 44K in the belt traveling direction. Two misregistration detection sensors 33 are provided at the writing start position and writing end position by the print head 12, that is, near both ends in the main scanning direction.

  Further, a sheet to be imaged is stored in a sheet feeding cassette 57, and a pickup roll 56 disposed on the upper end side (left end side in FIG. 1) of the sheet feeding cassette 57 is disposed on the leading end side of the sheet upper surface. The sheet is fed out from the sheet cassette 57 by pressure contact.

  The fed sheet is conveyed by a predetermined number of roll pairs 58 through a path indicated by a broken line in the drawing, is sent to the pressure contact position of the secondary transfer roll 60, and the color on the intermediate transfer belt 40 by the secondary transfer roll 60. The image is collectively transferred (secondary transfer) to the paper. The sheet on which the color image has been transferred is conveyed to a fixing device 64 by a sheet conveying system 62, where the image is fixed (heated, pressurized, etc.) and then discharged to a tray (not shown).

  Next, the print head 12 provided in each image forming unit 44C, 44M, 44Y, 44K will be described.

  As shown in FIGS. 2A and 2B, each color print head 12 has a long shape in the main scanning direction as a whole, and an aluminum base formed in a long shape in the main scanning direction. 13 is provided. On the aluminum base 13, a heater 28 as a heating means formed in a long shape in the main scanning direction and an LED chip substrate 22 formed in a long shape in the main scanning direction are provided in this order.

  On this LED chip substrate 22, the LED chip 14 as a light emitting element that exposes the photosensitive drum 46 to form a latent image is arranged along the main scanning direction according to a predetermined number of pixels (number of dots). Multiple sequences are arranged.

  A selfox lens array 18 is provided on the light emission side of the plurality of LED chips 14, and light emitted from the LED chips 14 passes through the selffox lens array 18 as shown in FIG. The image is formed on the photosensitive drum 46.

  In the present embodiment, an LED chip is applied as the light-emitting element of the present invention. However, the present invention is not limited to this, and other light-emitting elements such as an EL (Electro-Luminescence) element may be applied.

  Here, the structure of the heater 28 as a heating means will be described.

  FIG. 4 is a plan view of the heater 28. As shown in FIG. 4, the heater 28 includes a plate-like base material 30, and a stainless foil 32 as a conductor is attached to the base material 30. Yes. A pair of lead wires 34 for passing a current through the stainless steel foil 32 is disposed at both ends of the base material 30 in the main scanning direction.

  The stainless steel foils 32 are arranged in a line along the main scanning direction. Lead wires 34 are connected to both ends of the stainless steel foil 32 in the main scanning direction, and a voltage is applied from both ends of the stainless steel foil 32 in the main scanning direction. It has become so. When an electric current is passed through the stainless steel foil 32, Joule heat is generated by the electric resistance of the stainless steel foil 32.

  That is, the heater 28 is configured to thermally expand the LED chip substrate 22 using this Joule heat. The heater 28 extends the LED chip substrate 22 in the main scanning direction to correct the exposure position (dot position) of each LED chip 14.

  Here, the stainless steel foil 32 has excellent thermal conductivity, and when no current flows through the stainless steel foil 32, the stainless steel foil 32 has a function as a heat conductive sheet that radiates the heat of the LED chip substrate 22. Further, the surface of the heater 28 is subjected to an insulation process, and also has a function as an insulating sheet for insulating the LED chip substrate 22.

  As shown in FIG. 4, the stainless steel foil 32 is formed in a wave shape in which a wave is struck in the sub-scanning direction in consideration of good sitting and heat conduction uniformly to the LED chip substrate 22. However, it may be formed in a straight line. Moreover, you may use materials other than stainless steel as a conductor of this invention.

  By the way, in this embodiment, as shown in FIGS. 5A and 5B (for convenience of explanation, FIG. 5A shows the LED chip substrate 22 and the like in the main scanning direction and the sub-scanning direction in FIG. The main wiring 70 (see FIG. 5B) directly connected to the power source 68 is formed on the LED chip substrate 22, and the main wiring 70 is connected to the main wiring 70. The lead wire 34 of the stainless steel foil 32 shown in FIG. 4 is connected.

  In addition, a plurality of capacitors 72 as pseudo elements having resistance are disposed on the LED chip substrate 22 and connected to a sub-wiring 74 (see FIG. 5B) formed on the LED chip substrate 22. ing. The sub-wiring 74 is connected to the main wiring 70 and connected in parallel to each other. That is, the capacitor 72 and the heater 28 constitute a parallel circuit.

  The sub-wiring 74 is provided with a changeover switch 76. When the changeover switch 76 is turned ON / OFF, the main wiring 70 provided with the heater 28 and the capacitor 72 are provided when the changeover switch 76 is ON. A current is passed through the provided sub-wiring 74 so that a current flows through the heater 28 and the capacitor 72. When the changeover switch 76 is OFF, a current is passed through only the main wiring 70 and a current flows only through the heater 28. Can be.

  The ON state of the changeover switch 76 is a state where the parallel circuit is closed, and the OFF state of the changeover switch 76 is a state where the parallel circuit is open.

  Next, the configuration of a control system for driving the print head 12 according to the present embodiment will be described. FIG. 6 is a block diagram showing a configuration of a control system for driving the print head 12.

  As shown in FIG. 6, the print head drive unit 20 that drives the print head 12 of each color is connected to the print head 12 of each color. The print head drive unit 20 is connected to a controller (control unit) 16 that controls the entire tandem color printer 10, and is provided in each print head 12 based on image data sent from the controller 16. The light emission of the LED chip 14 is controlled.

  Here, the positional deviation amount detection sensor 33 is connected to the controller 16, and the positional deviation of the print head 12 of each color detected by the positional deviation amount detection sensor 33 by recording a predetermined registration mark. The quantity is input to the controller 16. That is, it is possible to detect whether or not the dot position deviation of the print head 12 of each color adjusted by the heater 28 is corrected.

  On the other hand, each color print head 12 includes a storage unit 24 and a heater 28, and a temperature sensor 26 is provided on the LED chip substrate 22. The temperature sensor 26 detects the temperature of the LED chip substrate 22, and the detected temperature is input to the print head drive unit 20. The temperature sensor 26 may be provided at a location other than the LED chip substrate 22.

  The storage means 24 stores data relating to the dot position deviation (for example, the amount of dot position deviation in the main scanning direction with respect to the design value) of the print head 12 of each color measured when the print head 12 is manufactured. Based on the stored data, the heater 28 is controlled by the print head drive unit 20.

  That is, the dot position data stored in the storage unit 24 is read from the storage unit 24 of the print head 12 of each color, and the print head 12 having the largest deviation in the main scanning direction is used as a reference, and the print head 12 is based on the reference. In order to adjust the dot position, the heaters 28 of the other print heads 12 are controlled.

  Here, the print head 12 having the largest amount of deviation in the main scanning direction is used as a reference here, but the present invention is not limited to this. For example, an upper limit value of manufacturing variation (when the dot position is most displaced in the main scanning direction) The reference value may be set in advance in consideration of the value), and the heaters 28 of all the print heads 12 may be controlled.

  For example, since the amount of thermal expansion per unit temperature is known from the size of the LED chip substrate 22, the LED chip substrate 22 is thermally expanded in order to set the LED chip substrate 22 to a target length. For this reason, the heater 28 is controlled by applying a voltage to the heater 28 until the LED chip substrate 22 reaches a predetermined target temperature, causing a current to flow, and confirming that the target temperature has been reached by the temperature sensor 26. The voltage is stabilized and the target temperature is maintained.

  Here, the main wiring 70 provided with the heater 28 and the sub wiring 74 constituting a parallel circuit are provided with a changeover switch 76, and the changeover switch 76 switches the power supply 68 with the heater 28. The capacitor 72 is connected in parallel, and a current is passed through the heater 28 and the capacitor 72, or the heater 28 is directly connected to the power source 68, and a current is passed only through the heater 28.

  Until the LED chip substrate 22 reaches a predetermined target temperature, the changeover switch 76 is turned on, and the heater 28 and the capacitor 72 are connected in parallel to the power source 68. When the LED chip substrate 22 reaches a predetermined target temperature, the changeover switch 76 is turned OFF and the heater 28 is directly connected to the power source 68. However, in order to maintain the temperature of the LED chip substrate 22 at the target temperature, it is necessary to turn the changeover switch 76 on or off based on the temperature detected by the temperature sensor 26.

  As another method, voltage-temperature rise characteristics are measured in advance and stored in the storage unit 24 of the print head drive unit 20 as a look-up table or the like, and the voltage applied to the heater 28 from the voltage-temperature rise characteristics. Can be determined. Furthermore, the pulse number of the current applied to the heater 28 may be similarly determined from the pulse number and the temperature rise characteristic using the pulse current.

  Next, with reference to FIG. 6, an example of the flow of dot misregistration correction performed at the time of initialization at the time of startup of the tandem color printer 10 according to the present embodiment will be described.

  As shown in FIG. 7, when the power of the tandem color printer 10 is turned on, in step 100, the print head driving unit 20 reads data relating to the dot position of each print head 12 from the storage means 24 of each print head 12. . Next, in step 102, the print head driving unit 20 recognizes the dot position data MAX, that is, the print head 12 (MAX print head 12) whose dot position has been shifted the longest in the main scanning direction.

  In step 104, the temperature rise of the print heads other than the MAX print head recognized in step 102 is calculated by the print head driving unit 20, and in step 106, the changeover switch 76 is turned on by the print head driving unit 20. Thus, the maximum power supply voltage is applied to the heater 28 of the print head 12 other than the MAX print head. In step 108, when the temperature sensor 26 detects that the LED chip substrate 22 has reached the target temperature, the voltage of the power source 68 is stabilized and the changeover switch 76 is turned off.

  Next, in step 110, the registration marks of each color are transferred to two positions on the writing and writing end sides, and the process proceeds to step 112, where the positional deviation amount detection sensor 33 determines the amount of dot positional deviation of the print head 12 of each color. Detected. That is, the positional deviation amount detected by the positional deviation amount detection sensor 33 is input to the controller 16.

  In step 114, the controller 16 determines whether or not the amount of dot position deviation of the print head 12 for each color is within a predetermined specification. If the determination is negative, the process returns to step 102 and the above-described processing is repeated. When the determination at step 114 is affirmed, the series of processing is terminated and the print standby state is entered.

  Next, the operation of the tandem color printer 10 according to the embodiment of the present invention will be described.

  In the tandem color printer 10 of the present invention, the dot position data of each print head 12 measured in advance at the time of manufacture is stored in the storage means 24 for each print head, and the dot position data is stored at the time of initialization at the start of the apparatus. In order to align the dot positions of the print heads 12 with reference to the dot positions of the print heads 12 (MAX print heads 12) having the largest deviation in the main scanning direction among the data read out and stored in the storage means 24, The drive of the heater 28 provided in the print head 12 is controlled to thermally expand the LED chip substrate 22 to correct the dot position deviation.

  Here, in the actual machine, when the temperature of the LED chip substrate 22 rises by 1 ° C., the LED chip substrate 22 is thermally expanded and corrected by about 10 μm. In the print head 12 having a print width of 500 mm, the dot position deviation amount is ± 150 μm. For this reason, the maximum dot position deviation amount can be corrected by raising the temperature of the LED chip substrate 22 by 15 ° C.

  For example, as shown in FIG. 8, when the target temperature of the LED chip substrate 22 is set to + 15 ° C. (45 ° C.) at room temperature (25 ° C.), how is the device initial time 4.3 minutes? The problem is whether the LED chip substrate 22 can reach the target temperature in a short time.

  In the present invention, the heater 28 for heating the LED chip substrate 22 and the capacitor 72 are connected in parallel so that a current flows through the heater 28 and the capacitor 72. In this case, since the amount of generated heat can be increased as compared with the case where only the heater 28 is used (see FIG. 11), the temperature of the LED chip substrate 22 can be rapidly increased.

  As shown in FIG. 8, it can be seen that the LED chip substrate 22 has reached the target temperature in 2.1 minutes after the tandem color printer 10 is started. That is, the dot position deviation amount of the print head 12 can be corrected in a short time by rapidly increasing the temperature of the LED chip substrate 22. For this reason, when the tandem color printer 10 is started, the time required to bring the print head 12 to a predetermined temperature, the so-called initialization time (initial time), can be shortened.

  Here, when correcting the dot position deviation between the print heads 12, the temperature adjustment of the print head 12 as a reference is performed by correcting the print head 12 having the largest dot position deviation in the main scanning direction as a reference. Since there is no need to perform the correction, the number of correction targets is reduced, and quick correction can be performed.

  Further, in this embodiment, since the dot position deviation between the print heads 12 can be corrected as described above, it is possible to expand the allowable range at the time of manufacturing the dot position deviation, and to improve the yield of the print head 12. Can do.

  Here, as shown in FIGS. 5A and 5B, a main wiring 70 to which the heater 28 is connected and a sub wiring 74 to which a capacitor 72 is connected are provided to form a parallel circuit. However, it is only necessary to be able to configure a parallel circuit with the heater 28, and the present invention is not limited to this.

  For example, instead of the capacitor 72, heaters 78 and 80 may be used. In this case, as shown in FIGS. 9A and 9B, two heaters 28 and 78 may be arranged on the same plane. Alternatively, as shown in FIG. 10, the two heaters 28 and 80 may be stacked. Further, although not shown, the print head 12 may include a dew condensation prevention heater, and the dew condensation prevention heater and the heater 28 may constitute a parallel circuit.

  In this embodiment, the tandem color printer is used as the image forming apparatus. However, an image forming apparatus that forms a monochrome image, for example, a monochrome printer may be used.

  In this monochrome printer, when an image is formed on preprinted paper, when correcting a positional deviation between an image formed in a predetermined format on the preprinted paper and a single color image to be formed, the main printer is used. The invention can be applied. The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the gist of the present invention.

1 is a diagram illustrating a schematic configuration of a tandem color printer according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The structure of the print head which concerns on embodiment of this invention is demonstrated, (A) is a schematic front view, (B) is a schematic side view. FIG. 2 is a schematic perspective view illustrating the relationship between a print head and a photoreceptor according to an embodiment of the present invention. It is a schematic plan view which shows the heater of the print head which concerns on embodiment of this invention. 1A and 1B are perspective views and a circuit diagram illustrating a configuration of a print head according to an embodiment of the present invention. 2 is a block diagram illustrating a configuration of a print head according to an embodiment of the present invention. 6 is a flowchart showing dot misalignment correction processing of the print head according to the embodiment of the present invention. 6 is a graph showing a time until a print head according to an embodiment of the present invention reaches a target temperature. FIG. 5A is a perspective view and FIG. 5B is a circuit diagram illustrating another configuration of the print head according to the embodiment of the present invention. It is a perspective view which shows the modification of FIG. The case where a power supply and a heater are directly connected is shown, (A) is a perspective view, and (B) is a circuit diagram.

Explanation of symbols

10 Tandem color printer (image forming device)
12 Print head (image recording head)
14 LED chip (light emitting device)
16 Controller (control means)
18 Selfox lens array 20 Print head drive unit (control means)
22 LED chip substrate (substrate)
26 Temperature sensor (temperature detection means)
28 Heater (heating means)
32 Stainless steel foil (heater, heating means)
72 Capacitor (pseudo element, heating auxiliary means)
76 changeover switch (switching means)
78 Heater (heating auxiliary means)
80 Heater (heating auxiliary means)

Claims (5)

A light emitting element that exposes a photoreceptor to form a latent image, a substrate on which a plurality of the light emitting elements are arranged in the main scanning direction, a heating unit that is disposed along the substrate and heats the substrate, and the heating unit A plurality of image recording heads connected in parallel with each other and having heating auxiliary means for auxiliary heating of the substrate ,
An image recording head driving unit for driving these image recording heads;
With
The image recording head drive unit is configured so that each image recording head is based on the positional deviation amount of the image recording head having the largest dot positional deviation amount along the main scanning direction of the substrate per unit temperature among the plurality of image recording heads. To control the heating auxiliary means
Image recording device. Each image recording head
A switching means for opening and closing a parallel circuit composed of the heating means and the heating auxiliary means to flow the current to the heating means and the heating auxiliary means, or to the heating means,
A control means for detecting a time during which a current is passed through the heating means and the heating auxiliary means, and causing the switching means to perform a switching operation;
An image recording apparatus according to claim 1. Each image recording head includes temperature detection means for detecting the temperature of the substrate, and the control means causes the switching means to perform a switching operation in accordance with the temperature detected by the temperature detection means.
The image recording apparatus according to claim 2. The image recording apparatus according to claim 1, wherein the heating auxiliary unit is a pseudo element having a resistance . The image recording apparatus according to claim 1, wherein the heating auxiliary unit is a heater .

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