JPH08171307A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device constituted so that excessive electric power consumption is prevented. CONSTITUTION: When the position of a transfer paper being passed through a fixing device is detected by a printer engine control part (34) by counting time after the trailing edge of a paper is detected for a fixed time by a resist sensor (33) by using a time counting means, a fixing action is executed by the remaining heat of a fixing roller by turning off the halogen heater of the fixing device (36) before the trailing edge of the transfer paper is passed through the fixing device prescribed time after the time counting action of the counting means is started (35).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction in power consumption of an image forming apparatus having a fixing means for fixing a toner image on a transfer sheet by using a heating means.

[0002]

2. Description of the Related Art FIGS. 7 and 8 show the construction of a laser beam printer which is an example of a conventional image forming apparatus. The image forming operation of the laser beam printer will be described with reference to this drawing. An image signal 101 (VDO signal) is input to the laser unit 102. Reference numeral 103 is a laser beam that is on / off modulated by the laser unit 102. A scanner motor 104 causes the rotary polygon mirror (polygon mirror) 105 to rotate steadily. An imaging lens 106 focuses the laser beam 107 changed by the polygon mirror 105 onto the photosensitive drum 108 which is the surface to be scanned.

Therefore, the laser beam 107 modulated by the image signal 101 is horizontally scanned (scanned in the main scanning direction) on the photosensitive drum 108. Reference numeral 109 is a beam detection port that takes in a beam from a slit-shaped entrance. The laser beam entering from this entrance is guided to the photoelectric conversion element 111 through the inside of the optical fiber 110. The laser beam converted into an electric signal by the photoelectric conversion element 111 is amplified by an amplifier circuit (not shown) and then becomes a horizontal synchronization signal.

Reference numeral 112 denotes a transfer paper which is a transfer material, and the latent image formed on the photosensitive drum 108 becomes a toner image visualized by the developing device 123, and is transferred to the transfer paper 112 by the transfer device 120. The transfer paper 112 to which the toner image has been transferred is fixed by a fixing device 121 which is a fixing means having a halogen heater which is a heating means, and the discharge unit 1
The paper is discharged from 22.

Reference numeral 125 denotes a paper discharge sensor using a photo interrupter, which detects passage of the rear end of the transfer paper 112. When the paper discharge sensor 125 detects the rear end of the transfer paper 112, the control means described later stops the halogen heater drive circuit.

FIG. 9 shows this halogen heater drive circuit. 130 is a commercial power source for connecting the image forming apparatus,
The image forming apparatus lights the halogen heater 132 by supplying commercial power to the halogen heater 132.
The power supply to the halogen heater 132 is controlled by turning on / off by the triac 133. The resistors 134 and 135 are bias resistors for the triac 133, and the phototriac coupler 137 is
It is a device to secure the primary and secondary creepage distances. The triac 133 is turned on by energizing the light emitting diode 137 of the phototriac coupler 137. The resistor 136 is a phototriac coupler 137.
Is a resistor for limiting the current of the transistor 13
Turn on / off by 8. The transistor 138 operates according to the signal from the control means 139.

[0007]

However, in the case of the fixing device using the halogen heater, the temperature of the fixing roller does not immediately cool even when the heater is turned off, and the temperature is constant even when the heater is turned off. The time is within the temperature range in which the toner can be fixed. That is, even if the heater is turned off before the transfer sheet completely passes through the fixing device, the fixing can be performed by the residual heat of the fixing device. However, under the present circumstances, the halogen heater of the fixing device is turned off after the trailing edge of the transfer paper has completely passed through the fixing device, so that there is a drawback that excessive power is consumed.

An object of the first invention of the present application is to provide an image forming apparatus which does not consume excessive power.

The second object of the present invention is to:
An object of the present invention is to provide an image forming apparatus capable of saving excessive power as much as possible by accurately controlling the timing of turning off the halogen heater.

Further, a third object of the present invention is to provide an image forming apparatus capable of saving excessive power without causing fixing failure even when a fixing device having a low heat capacity is used. It is in.

The fourth object of the present invention is to:
An object of the present invention is to provide an image forming apparatus capable of reducing extra power before the trailing edge of the transfer sheet completely passes through the fixing device.

Further, a fifth object of the present invention is to provide an image forming apparatus capable of reducing extra power as much as possible before the trailing edge of the transfer sheet completely passes through the fixing device. Another object of the sixth invention of the present application is to provide an image forming apparatus capable of further reducing power consumption by performing optimum temperature control according to the toner amount. .

[0013]

According to the first invention of the present application, the above object is to provide a toner image forming means for forming a toner image using an electrostatic recording system, and a heating means for heating the toner image. In an image forming apparatus having a fixing unit for fixing to a transfer material by using it, a control unit for controlling a temperature of the heating unit, and a detection unit for detecting a position of the transfer material on a conveyance path, the control unit is This is achieved by cutting off the power supply to the heating means at a predetermined timing based on the position of the transfer material detected by the detection means and fixing the toner image with the residual heat of the heating means.

According to the second invention of the present application,
The above-mentioned object is, in the above-mentioned first invention, the detection means is means for detecting that the transfer material has passed a predetermined position on the transfer material transport path, and the control means is the detection means for passing the transfer material. This is achieved by providing a time measuring means for measuring the time from the detection of, and determining the position of the transfer material on the conveyance path after the predetermined place.

Further, according to the third invention of the present application, in the above-mentioned first object, the detecting means is provided after the fixing means on the transfer material conveying path, and detects the leading end of the transfer material. It is achieved by being a means to do.

According to the fourth invention of the present application,
In the first aspect of the invention described above, the predetermined timing is achieved when the rear end of the transfer material is before being discharged from the fixing unit.

Further, according to the fifth invention of the present application, in the above-mentioned first invention, the predetermined timing is before the trailing edge of the toner image on the transfer material is discharged from the fixing means. Or before the transfer material enters the fixing means.

According to the sixth invention of the present application,
The above-mentioned object is, in the above-mentioned first invention, the control means has a detection means for detecting a dot ratio of a latent image formed in a predetermined range of the transfer material, and the detection means and the predetermined dot ratio. This is achieved by controlling the temperature of the fixing unit within a predetermined temperature range according to the dot ratio based on the relationship with the temperature of the fixing unit.

[0019]

According to the first invention of the present application, when the position of the transfer material is detected during the conveyance to the fixing means by the detecting means for detecting the position of the transfer material, the predetermined position is determined based on the detected position. At this timing, the heating means is de-energized, and the residual heat of the heating means fixes the toner image. Therefore,
Power saving is achieved.

According to the second invention of the present application,
When the detection means detects that the transfer material has passed through a predetermined place on the transfer material conveyance path to the fixing means, the control means detects the passage of the transfer material by the detection means by the timing means. By measuring the time, the position of the transfer material on the conveyance path after the predetermined place is judged, and the power supply to the heating means is cut off at a predetermined timing. Therefore, excess power is saved.

Further, according to the third invention of the present application, when the front end of the transfer material is detected by the detecting means provided after the fixing means on the transfer material conveying path, the heating means is energized at a predetermined timing. Cut off. Therefore, excess power is saved.

According to the fourth invention of the present application,
Power is cut off to the heating means before the trailing edge of the transfer material is discharged from the fixing means, so power is saved compared to the conventional method where the heating means is cut off after the trailing edge of the transfer material is discharged from the fixing means. Be promoted.

Further, according to the fifth aspect of the present application, the heating means is provided to the heating means before the trailing edge of the toner image on the transfer material is discharged from the fixing means or before the transfer material enters the fixing means. Since power supply is cut off, further power saving can be achieved.

According to the sixth invention of the present application,
The control unit detects the dot ratio of the latent image formed in the predetermined range of the transfer material by the detection unit, and based on the relationship between the predetermined dot ratio and the temperature of the fixing unit, the detected dot ratio is Since the temperature of the fixing unit is controlled within a predetermined temperature range corresponding to the above, the optimum temperature is achieved according to the toner amount, and power saving can be achieved as compared with the related art.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows an example in which the halogen heater of the fixing device is turned off and the remaining heat is used for fixing before the trailing edge of the transfer sheet passing through the fixing device exits the fixing device. FIG. 2 shows the flowchart of FIG.

When the printer starts image formation, the halogen heater 19 which is a heating means of the fixing device 17 which is a fixing means is turned on (step 31), and when the surface temperature of the fixing roller 18 reaches within a specified temperature range (step 32). A latent image is formed on the photosensitive drum 12 and a paper feeding operation is performed. The transfer paper 15 that is the fed transfer material is temporarily stopped before the registration roller 11 in order to align the front end of the transfer paper 15 with the front end of the latent image, and is conveyed again. Reference numeral 16 is a registration sensor, which is a sensor as a detection means using a photo interrupter arranged in front of the registration rollers on the conveyance path. The rear end of the transfer paper 15 conveyed by the registration sensor 16 is detected,
The printer engine control unit 20 serving as a control unit controls the transfer paper 15
Is confirmed to have been fed to the electrophotographic process section 14 (step 33). After that, the toner image formed on the photosensitive drum 12 by the transfer roller 13 is transferred onto the transfer paper 15, and the toner is fixed by the fixing device 17.

In the image forming apparatus as described above, since the transfer speed of the transfer paper 15 and the length of the paper transfer path are constant, the printer engine control unit 20 positions the transfer paper 15 while passing through the fixing device 17. Can be detected by measuring the time after the registration sensor 16 detects the trailing edge of the paper for a fixed time by the time measuring means (step 34).
When a predetermined time has elapsed since the timekeeping means started counting time (step 35), that is, the printer engine controller 20 receives the control signal 21 and the halogen heater of the fixing device 17 before the trailing edge of the transfer paper 15 leaves the fixing device 17. 19 is turned off (step 36), and fixing is performed by the residual heat of the fixing roller 18.

The timing for turning off the heater must be limited to some extent so that the surface temperature of the fixing roller 18 can be fixed until the trailing edge of the paper passes.

When the halogen heater 19 is used as the heat source as in the present embodiment, the temperature of the fixing roller 18 does not drastically decrease even when the halogen heater 19 is turned off, and the temperature is maintained for a certain period of time. Is within a temperature range sufficient to fix the toner. That is, even if the halogen heater 19 is turned off before the rear end of the transfer paper 15 completely passes through the fixing device 17, the residual heat of the fixing device 17 can be used to fix the toner to the rear end of the transfer paper 15. The power consumption can be reduced as compared with the conventional limitation.

As described above, before the trailing edge of the transfer sheet passing through the fixing device passes through the fixing device, the halogen heater of the fixing device can be turned off to fix with residual heat, which is consumed by the halogen heater. It is possible to reduce excessive power consumption.

In this embodiment, a fixing device using a halogen heater as a heat source has been described as an example, but it goes without saying that the present invention is also effective for an on-demand type fixing device. However, it is necessary to determine the timing for turning off the heater in consideration of the thermal time constant of the fixing device used.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. 1 and 3. FIG. 1 shows an example in which the halogen heater of the fixing device is turned off and fixing is performed with residual heat before the trailing edge of the toner image on the transfer paper leaves the fixing device. FIG.
Shows the flowchart of FIG.

When the printer starts image formation, the fixing device 1
When the halogen heater 19 of No. 7 is turned on (step 41) and the surface temperature of the fixing roller 18 reaches within the specified temperature range (step 42), the photosensitive drum 1 is irradiated with the laser beam.
A latent image is formed on the sheet 2 and a sheet feeding operation is performed. The fed transfer paper 15 is temporarily stopped before the registration roller 11 in order to align the leading end of the transfer paper 15 with the leading end of the latent image, and is conveyed again. Reference numeral 16 is a registration sensor, which is a sensor using a photo interrupter arranged in front of the registration roller 11 on the conveyance path. The registration sensor 16 detects the trailing edge of the transfer paper 15 conveyed, and the printer engine control unit 20 confirms that the transfer paper 15 has been fed to the electrophotographic process unit 14 (step 43). After that, the toner image formed on the photosensitive drum 12 by the transfer roller 13 is transferred onto the transfer paper 15, and the toner is fixed by the fixing device 17.

The trailing edge position of the toner image formed on the transfer paper 15 during or before passing through the fixing device 17 can be detected as follows. Since the transfer speed of the transfer paper 15 and the length of the paper transfer path are constant, the printer engine control unit 20 finishes the latent image formation by the laser beam (step 4).
4) Then, the time from then is detected by measuring a certain time by the time measuring means (step 45). When a predetermined time has elapsed since the timekeeping means started timekeeping (step 4
6) That is, before the rear end position of the toner image on the transfer paper 15 passes through the fixing device 17, the printer engine control unit 20 turns off the halogen heater 19 of the fixing device 17 by the control signal 21 (47), and the fixing roller Fixing is performed with residual heat of 18.

The timing of turning off the heater 19 must be limited to some extent so that the surface temperature of the fixing roller 18 can be fixed until the trailing edge of the toner image passes.

As described above, before the trailing edge of the toner image formed on the transfer paper leaves the fixing device, the halogen heater of the fixing device can be turned off to fix with the residual heat.

Since the heater can be turned off earlier than in the first embodiment in this embodiment, the excess power consumed by the halogen heater can be further reduced as compared with the first embodiment.

For example, in the case of image formation on the upper half of the paper, the heater can be turned off earlier than the image formation on the entire paper.

In this embodiment, a fixing device using a halogen heater as a heat source has been described as an example, but it goes without saying that the present invention is also effective for an on-demand type fixing device. However, it is necessary to determine the timing for turning off the heater in consideration of the thermal time constant of the fixing device used.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIGS. 1 and 4 to 6. FIG.
Shows an example in which the temperature of the fixing device is controlled according to the dot ratio of the formed latent image in a predetermined range of the transfer paper. 6 is shown in FIG.
The flowchart of is shown.

When the printer starts image formation, the fixing device 1
When the halogen heater 19 of No. 7 is turned on (step 52) and the surface temperature of the fixing roller 18 reaches within the specified temperature range (step 53), the photosensitive drum 1 is irradiated with the laser beam.
A latent image is formed on the sheet 2 and a sheet feeding operation is performed. The fed transfer paper 15 is temporarily stopped before the registration roller 11 in order to align the leading end of the transfer paper 15 with the leading end of the latent image, and is conveyed again. Reference numeral 16 is a registration sensor, which is a sensor using a photo interrupter arranged in front of the registration roller 11 on the conveyance path. The registration sensor 16 detects the rear end of the transfer paper 15 conveyed, and the printer engine control unit 20 confirms that the transfer paper 15 has been fed to the electrophotographic process unit 14 (step 54). After that, the toner image formed on the photosensitive drum 12 by the transfer roller 13 is transferred onto the transfer paper 15, and the toner is fixed by the fixing device 17.

A method of controlling the temperature of the fixing device 17 will be described below with reference to FIGS. 5 and 6.

The printer engine controller 20 controls the transfer paper 1
The dot detection means for detecting the dot ratio of the latent image formed in the predetermined range of No. 5, the position detection means of the transfer paper using the time measuring means, and the relationship between the predetermined dot ratio and the temperature of the fixing device 17 It has as reference data. 5 and 6 show examples of the predetermined range and reference data. The printer engine control unit 20 detects the ratio of the dots of the latent image in the predetermined area (hatched portion) 51 of the transfer paper 15 by the dot detection means (step 56). Based on the result of comparing the detected ratio with the reference data and the time measured by the above-mentioned time measuring means (steps 57, 5).
8) On / off control of the temperature of the heater of the fixing device 17 is performed in advance so that the predetermined range 51 reaches a predetermined temperature when passing through the fixing device 17 (step 59).

For example, referring to FIG. 5, in the place where the dot ratio is 3%, the temperature of the heater is controlled so that the temperature of the fixing device becomes around 150 ° C. when the predetermined range 51 passes through the fixing device 17. I do.

By using this embodiment, when the amount of toner in the predetermined range on the transfer paper is small, the fixing temperature for fixing that range can be lowered below the normal temperature control temperature. The power consumed by the heater of the container can be reduced.

In this embodiment, the fixing device using a halogen heater as a heat source is described as an example, but it goes without saying that the present invention is also effective for an on-demand type fixing device. However, it is necessary to determine the timing for turning on / off the heater in consideration of the thermal time constant of the fixing device used.

Further, the position of the detecting means for detecting the position of the transfer sheet may be rearward of the fixing device 17 in the moving direction of the transfer sheet, and the heater is turned off at a predetermined timing after the front end of the transfer sheet is detected. May be. This is particularly effective when using a fixing device having a low heat capacity.

[0049]

As described above, the first aspect of the present application
According to the invention, the position of the transfer material is detected by the detecting unit, and the heating unit is de-energized at a predetermined timing based on the detected position. Therefore, excessive power consumed by the heating unit of the fixing unit is consumed. Therefore, it is possible to provide an image forming apparatus with lower power consumption than ever before.

According to the second invention of the present application,
The detection means detects that the transfer material has passed a predetermined position on the transfer material conveyance path to the fixing means, and the control means detects the passage of the transfer material by the time detection means. (EN) An image forming apparatus with lower power consumption is provided by measuring the time, determining the position of the transfer material on the conveyance path after the predetermined location, and cutting off the power supply to the heating means at a predetermined timing. You can

Further, according to the third invention of the present application, the leading end of the transfer material is detected by the detection means provided after the fixing means on the transfer material conveying path, and the heating means is energized at a predetermined timing. Therefore, it is possible to provide an image forming apparatus with lower power consumption.

According to the fourth invention of the present application,
Power is cut off to the heating means before the trailing edge of the transfer material is discharged from the fixing means, so power is saved compared to the conventional method where the heating means is cut off after the trailing edge of the transfer material is discharged from the fixing means. Can be realized.

Further, according to the fifth invention of the present application, the heating means is provided to the heating means before the trailing edge of the toner image on the transfer material is discharged from the fixing means or before the transfer material enters the fixing means. Since power supply is cut off, further power saving can be achieved.

According to the sixth invention of the present application,
The detection unit detects the dot ratio of the latent image formed in the predetermined range of the transfer material, and based on the relationship between the predetermined dot ratio and the temperature of the fixing unit, the predetermined temperature corresponding to the detected dot ratio. Since the temperature of the fixing unit is controlled within the range, optimum temperature control according to the amount of toner becomes possible, and power saving can be achieved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a laser beam printer to which the present invention is applied.

FIG. 2 is a flow chart for explaining the control of the heating means in the first embodiment of the present invention.

FIG. 3 is a flow chart for explaining control of heating means in the second embodiment of the present invention.

FIG. 4 is a diagram showing a transfer sheet for explaining a third embodiment of the present invention.

FIG. 5 is a diagram showing an example of data on the relationship between the dot ratio and the temperature of the fixing device in the third embodiment of the present invention.

FIG. 6 is a flow chart for explaining control of heating means in a third embodiment of the present invention.

FIG. 7 is a configuration diagram around an exposure unit of a conventional laser beam printer.

FIG. 8 is an overall configuration diagram of a conventional laser beam printer.

FIG. 9 is a drive circuit diagram of a conventional halogen heater.

[Explanation of symbols]

 15 transfer paper (transfer material) 16 registration sensor (detection means for detecting the position of the transfer material) 17 fixing device (fixing means) 19 halogen heater (heating means) 20 printer engine control section (control means)

Claims (6)

[Claims] 1. A toner image forming means for forming a toner image using an electrostatic recording method, a fixing means for fixing the toner image on a transfer material by using a heating means, and a control for controlling the temperature of the heating means. In the image forming apparatus having a unit and a detection unit that detects the position of the transfer material on the conveyance path, the control unit may include the heating unit at a predetermined timing based on the position of the transfer material detected by the detection unit. The image forming apparatus is characterized in that the toner image is fixed by the residual heat of the heating means by turning off the power supply to the toner. 2. The detecting means is means for detecting that the transfer material has passed a predetermined place on the transfer material conveying path, and the control means detects the passage of the transfer material by the detecting means. The image forming apparatus according to claim 1, further comprising: a time measuring unit that measures time, and determines the position of the transfer material on the conveyance path after the predetermined place. 3. The image forming apparatus according to claim 1, wherein the detection unit is a unit that is provided after the fixing unit on the transfer material conveyance path and detects the leading end of the transfer material. 4. The image forming apparatus according to claim 1, wherein the predetermined timing is before the trailing edge of the transfer material is discharged from the fixing unit. 5. The image according to claim 1, wherein the predetermined timing is before the trailing edge of the toner image on the transfer material is discharged from the fixing means or before the transfer material enters the fixing means. Forming equipment. 6. The control unit has a detection unit for detecting a dot ratio of a latent image formed in a predetermined range of the transfer material, and the detection unit and the predetermined dot ratio and the temperature of the fixing unit. The image forming apparatus according to claim 1, wherein the temperature of the fixing unit is controlled within a predetermined temperature range according to the dot ratio based on the relationship.