JPH01173088A - Recorder - Google Patents

Abstract

PURPOSE:To execute an optimum temperature control even if thickness of a form changes by controlling a temperature by correcting a temperature control reference of a heat fixing part, based on heat conduction information of the form, in a printing state of an electrophotography system. CONSTITUTION:A heating element temperature control part 1 controls a heating element 2 so as to become a prescribed temperature. A form detecting element 3 such as a thermistor, etc., is placed so as to be opposed to the heating element 2, and detects a temperature of a form 4. A heat fixing roller 6 is heated by a control output of a heat fixing part temperature control circuit 5, and feeds out the form 4, while rotating. A heat fixing roller temperature detecting element 7 comes into slide-contact with the roller 6 and detects a temperature, and brings it to feedback to the control circuit 5. In this constitution, a temperature of the element 3 is compared with a reference value and held until the form 4 passes through the roller 6. By comparing a detection signal of the element 7, based on this difference signal as a reference, a temperature of the roller 6 is controlled. In such a way, even if the form changes, a temperature of the roller 6 for fixing a toner is held automatically at an optimum temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device with an improved heat fixing section.

[Prior Art] Copiers, laser printers, and the like use an electrophotographic method (xerography method). For example, when an optical image is projected onto a charged photoconductor, or when it is drawn with a light beam, the charge in the exposed area escapes and forms an electric latent image. Charged toner is attached to a photoconductor, developed, and transferred to charged plain paper, and then the transferred plain paper is heated to fuse and fix the toner.

In addition, there is also a method that forms an electric latent image directly on paper, develops it with toner, and fixes it thermally.

In such a recording apparatus, the heating temperature in the above-mentioned heat fixing process is set based on the thickness of general paper. For this reason, toner fixing properties of extremely thick or thin sheets of paper are inferior to those of regular paper, so as a means to prevent this, a system that allows the user to select the sheet of paper by operating an operation panel, etc. is proposed. It is taken.

[Problems to be Solved by the Invention] As described above, in the recording apparatus using the electrophotographic method, the heating temperature in the above-mentioned heat fixing process is set based on the thickness of general paper. For this reason, toner fixing properties of extremely thick or thin sheets of paper are inferior to those of regular paper, so as a means to prevent this, a system that allows the user to select the sheet of paper by operating an operation panel, etc. is proposed. It is taken. However, this is set appropriately by the user, so when printing on items such as postcards and envelopes, it is often difficult to set the heat fixing temperature properly, resulting in poor toner fixing properties. The disadvantages are that the print quality is impaired, or that toner adheres to the heat roller for heat fixing, staining the heat roller, and even the cleaning pad provided to remove this stain cannot be removed, eventually staining the printing paper itself. was there. This is because the optimum settings cannot be made to match the heat transfer characteristics that change depending on the thickness and quality of the paper.If the heat dispersion is large, the toner will be difficult to fix and will easily peel off, and conversely, the fixing temperature will be too high. This may cause the paper to burn. Therefore, the purpose of this invention is to be able to automatically maintain the optimum fixing temperature even when the paper is changed, thereby eliminating the need for troublesome setting of the fixing temperature and, moreover, making it possible to obtain high quality printing. The purpose of the present invention is to provide a recording device that can perform the following functions.

[Means for Solving the Problems] In order to achieve the above object, the present invention is configured as follows. In other words, in an electrophotographic recording apparatus that records by sending a sheet of paper on which a toner image has been formed to a heat fixing section whose temperature can be electrically controlled and thermally fixing the paper, a heat source that detects the temperature of the heat fixing section is used. A fixing section temperature detection means, a heating means that contacts the unrecorded paper sent and heats it at a constant temperature, a temperature detection element that detects the temperature of the heated paper, and a detection of this temperature detection element. a first comparing means for comparing the temperature signal with a reference value and outputting a signal corresponding to the difference; and a first comparing means for sample-holding the output signal of the comparing means until the fed sheet passes through the heat fixing section. a sample hold means for holding the signal during the recording operation, and a selection means for extracting the signal held by the sample hold means during the recording operation state and a lower predetermined temperature signal preset by the setting means during the standby state; and a second comparison means for comparing the detection signal of the heat fixing section temperature detection means with reference to the extracted signal obtained by the heat fixing section and generating a signal corresponding to the difference for controlling the temperature of the heat fixing section. and fixing section temperature control means.

[Operation] In such a configuration, an electric latent image is formed on the photoconductor, this electric latent image is developed with toner and transferred to paper,
Recording is performed by sending this to a heat fixing section whose temperature can be electrically controlled and thermally fixing it.The unrecorded paper that has been sent is heated at a constant temperature by a heating means, and the temperature of this heated paper is is detected by a temperature detection element. The detected temperature signal of this temperature detection element is compared with a preset reference value by the first comparison means to obtain a signal corresponding to the difference, and the output signal of this comparison means is sampled and held by the sample and hold means. Then, the fed paper is held until it passes through the heat fixing section. On the other hand, during the printing operation, the sample holding means is held by the selection means which extracts the signal held by the sample hold means during the recording operation state, and extracts a lower predetermined temperature signal preset by the setting means during the standby state. and extract the signal. Then, a second comparing means compares the detection signal of the thermal fixing section temperature detecting section with this extracted signal as a reference, generates a signal corresponding to the difference, and uses the generated signal to control the temperature of the thermal fixing section. Further, in the standby state, the selection means extracts a lower predetermined temperature signal preset by the setting means, and the second comparison means compares the detection signal of the heat fixing section temperature detection means with this extracted signal as a reference. A signal corresponding to the difference is generated and used to control the temperature of the heat fixing section. Therefore, during printing, the temperature control standard of the heat fixing section is corrected based on the heat conduction information of the paper, and the temperature is controlled by feeding back the actual temperature information of the heat fixing section, so no matter whether the paper is thick or thin. Heat fixing can be performed at the optimal temperature. Furthermore, since the temperature is controlled to such an extent that the heat fixing section is preheated during the standby state, there is no fear of overheating, and the temperature can immediately be brought to the optimum temperature once the printing state is entered.

Therefore, according to the present invention, even if the paper is changed, the fixing temperature can be automatically maintained at an optimum level, so that the troublesome setting of the fixing temperature is unnecessary, and moreover, it is possible to obtain high quality printing. It is possible to provide a recording device with

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a main part showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a heat fixing section temperature control circuit in this system, and FIG. 3 is a schematic diagram showing a main part configuration of this system. 4 are timing charts for explaining the operation of this device.

In FIG. 1, reference numeral 1 denotes a heating element temperature control unit that controls the temperature of a heating element 2 for paper detection, and controls the temperature of the heating element 2 so that it is always constant. Further, 3 is a paper detecting element, which is constituted by, for example, a thermistor. The paper detecting elements 3 are arranged to face each other, and when the paper 4 is sent, the paper 4 is sandwiched between the heating element 2 for paper detection and the paper detecting element 3 to obtain information on the thermal conductivity coefficient of the paper 4. Reference numeral 5 denotes a thermal fixing section temperature control circuit, which receives information on the thermal conductivity coefficient of the paper 4 obtained from the paper detection element 3 and controls the temperature of the thermal fixing section. Reference numeral 6 denotes a heat fixing roller constituting the heat fixing section, which has a heating element and generates heat according to the control output of the heat fixing section temperature control circuit 5, and rotates to feed out the paper.

A heat fixing roller temperature detection element 7 detects the temperature of the heat fixing roller, and is in sliding contact with the heat fixing roller 6 to detect the temperature and feed it back to the heat fixing section temperature control circuit 5. This is constituted by, for example, a thermistor.

The heat fixing section temperature control circuit 5 is constructed as shown in FIG. That is, 21 is a comparison circuit having an amplification function, which compares the output voltage e1 of the paper detection element 3 with reference to the comparison reference voltage ei2 supplied by dividing the DC voltage element V by the voltage dividing resistors R1 and R2. , and generates an output corresponding to the difference. Reference numeral 22 denotes a sample and hold circuit, which holds and outputs the output of the comparison circuit 21 upon receiving a hold signal from a control circuit (not shown).

ASW-A and ASW-B are analog switches, respectively, and ASW-A receives the ON signal MrON of the motor that feeds the paper and extracts the output of the closed sample and hold circuit 22 during the rotation period of the motor. It is something. Further, ASW-B closes when the on-signal MrON of the motor for feeding the paper disappears, and extracts the set voltage from the setter 23 that sets the temperature reference in the standby state. Reference numeral 24 denotes a comparison circuit having an amplification function, which compares the detection output of the heat fixing roller temperature detection element 7 using the signal extracted by the ASIf-A- or ASW-H as a reference signal, and outputs an output corresponding to the difference. Occur. 25 is a heater on signal eater from a control circuit (not shown)
This gate circuit is controlled by oN and extracts the output of this comparison circuit 24 and applies it to the heat fixing roller 6 to control heating.

FIG. 3 is a block diagram of the printing and fixing section, in which 2 is a heating element for paper detection, 3 is a paper detection element, and a paper detection sensor 31 is provided in front of these, and the paper 4 is fed.
When the paper 4 comes, the paper detection sensor 31 detects this and brings the paper detection element into contact with the paper detection heating element 2 at the timing when the paper 4 reaches the position of the paper detection heating element 2, and generates heat for paper detection at a constant temperature. The paper detecting element 3 detects the temperature of the paper 4 heated by the body 2 to obtain information regarding the thermal conductivity coefficient.

Reference numeral 32 denotes a photoconductive drum for forming and developing an electric latent image, in which a printed image is formed as an electric latent image and developed by adhesion of toner, and this toner image is sent as described above. The image is transferred onto the coming paper 4, and the heat fixing press roller 3 rotates synchronously with the heat fixing roller 6.
3, while being conveyed, it is heated and fixed by the heat of the heat fixing roller 6, and is discharged as a hard copy.

The operation of this apparatus having such a configuration will be explained with reference to the time chart shown in FIG. In this apparatus, when a printing operation is started, the paper feed motor is first activated and the paper 4 is fed. Then, the paper 4 is detected by the paper sensor 31
When the paper reaches the position, it is detected by the paper sensor 31, and a paper detection signal (FIG. 4(a)) is generated while the paper is at the paper sensor 31 position (this is defined as time T1). As a result, the paper 4 is sandwiched between the paper detection heating element 2 and the paper detection element 3, which have been heated and maintained at a constant temperature in advance under the control of the heating element temperature control circuit 1. Then, the sheet is heated by the heating element 2 for sheet detection. The temperature of the heated paper 4 is detected by the paper detection element 3, and the temperature of the heated paper 4 is detected by the heat fixing section temperature control circuit 5 as a detection signal el.
give to The heat fixing section temperature control circuit 5 uses this detection signal e.
1 is compared with the reference signal ei2 by the comparison circuit 21, and a signal corresponding to the difference is generated. On the other hand, the heat fixing section temperature control circuit 5
Then, a hold signal is output a little later than this based on the detection signal of the paper sensor 31 (this delay time is defined as T4), and the output is continued until the paper finishes passing through the heat fixing section (this time is defined as T2). (Fig. 4(b)). Note that T3 in FIG. 4(C) is a period during which the paper remains in the heat fixing section. Therefore, the sample and hold circuit 22 of the heat fixing section temperature control circuit 5 performs sampling for the period T4, and then holds and outputs the output of the comparison circuit 21 at the time when the hold signal is received. Prior to this, the analog switch ASW-
A is closed, and the gate 25 is opened by the heater ON signal HeaterON applied during the power-on period. Therefore, the held output signal of the sample and hold circuit 22 passes through the analog switch ASW-A and is applied to the comparison circuit 24. The comparison circuit 24 compares the heat detection signal output by the temperature detection element 7 of the heat fixing roller with the output signal of the sample hold circuit 22 as a reference, and outputs a signal corresponding to the difference. This output signal is applied as a heating output to the thermal fixing roller 6 through the gate circuit 25, and the thermal fixing roller 6 is heated and controlled. When the printing operation is finished, the motor-on signal disappears in order to stop the paper feed motor, so the analog switch ASW-A is
is turned off, and analog switch ASW-8 is turned on instead. Therefore, the comparator circuit 24 is supplied with a set voltage from the setter 23 that sets the temperature reference during the standby state, and the detection output of the heat fixing roller temperature detection element 7 is compared with this reference.

Therefore, the temperature of the heat fixing roller 6 is now controlled so as to maintain it at the temperature in the standby state.

In this way, the output of the comparison circuit 21 is controlled for a certain period of time (
T2) is sampled, and the value obtained by amplifying the difference between the output voltage e1 of the paper detection element 3 obtained from this sampled temperature and the reference voltage e12 of the comparator circuit 21 is held for a certain period of time (T3), and the temperature of the heat fixing section is This is the reference voltage of the control circuit 5. Therefore, when the paper 4 that is the object to be measured is thick, the output voltage e1 from the paper detection element 3 is smaller than when the paper is thin, so the reference voltage e of the comparison circuit 21 is
Since the difference from i2 is large, the reference voltage of the heat fixing section control circuit 5 is set high correspondingly. Therefore, the temperature of the heat fixing section is controlled at a high temperature that corresponds to the above difference, and is controlled to a temperature necessary for fixing that compensates for the heat absorbed by the paper, so the toner can be fixed well. It becomes like this. In addition, since the value that determines the reference voltage for temperature control of the heat fixing unit control circuit 5 is an analog value, the control range is continuous, so the temperature can be adjusted to the optimum temperature corresponding to the paper being used. It becomes possible to set the temperature of the fixing section.

In addition, in the standby state other than during printing operation, the analog switch ASW-B selects the standby reference value, which is set so that the temperature is somewhat lower than that during printing operation, and when the temperature is in the printing state, In comparison, the temperature of the heat constant tube section is controlled to be lower. Then, to switch this temperature, the on/off signal of the paper feed motor is used as a signal to determine whether it is in printing operation or in standby mode, and when this is on, the output voltage of the paper detection element is sampled and held. The analog switch ASW-A is turned on so as to set the value as the reference voltage and given to the comparator circuit 24 as the reference value, and when the paper feed motor is off, the analog switch ASv-A is turned off, and
Standby reference voltage setting circuit 23 that provides low heating temperature
Analog switch AS to select the reference voltage by
Turn off W-8 and give it to the comparator circuit 24 as a reference value,
Temperature control at low temperature.

Therefore, when an idle heating state such as a standby state is sufficient, the thermal fixing roller 6 does not need to be overheated, and it is possible to maintain the temperature at the optimum temperature immediately after entering the printing state.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope of the gist thereof, and is applicable to a method of recording by thermally fixing toner. If it is, it can be applied.

[Effects of the Invention] As described above, according to the present invention, in an electrophotographic recording apparatus, even when the paper is changed, the temperature of the heat fixing unit that heats the toner on the paper is automatically adjusted. It becomes possible to provide a recording device that can maintain the temperature at an optimum temperature, thereby achieving good fixing and preventing staining of the paper.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts showing an embodiment of the present invention, FIG. 2 is a diagram showing the structure of the heat fixing section temperature control circuit in this system, and FIG. 3 is a schematic diagram of the main parts of the system. 4 are time charts showing the operation of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Heating element temperature control section, 2... Heating element for paper detection, 3... Paper detection element, 4... Paper, 5... Heat fixing part temperature control circuit, 6... Heat Fixing roller, 7... Heat fixing roller temperature detection element, 21.24... Comparison circuit,
22...Sample hold circuit, ASW-A, A
SW-B: Analog switch, 31: Paper sensor, 32: Photoconductive drum, 33: Heat fixing press roller. Applicant's agent Patent attorney Takehiko Suzue 3 Illustrated print, Figure 4

Claims (1)

[Claims] In an electrophotographic recording device that performs recording by sending a sheet of paper on which a toner image is formed to a thermal fixing section whose temperature can be electrically controlled and thermally fixing the sheet, the thermal fixing section detects the temperature of the thermal fixing section. A temperature detection means, a heating means that contacts the unrecorded paper sent and heats it at a constant temperature, a temperature detection element that detects the temperature of the heated paper, and a detected temperature signal of the temperature detection element. a first comparing means for comparing the value with a reference value and outputting a signal corresponding to the difference; and a first comparing means for sample-holding the output signal of the comparing means until the fed sheet passes through the heat fixing section. , a sample hold means for holding, a selection means for extracting the signal held by the sample hold means in a recording operation state, and a lower predetermined temperature signal preset by a setting means in a standby state; a second comparing means that compares the detection signal of the heat fixing section temperature detection means with the obtained extracted signal as a reference and generates a signal corresponding to the difference to provide for temperature control of the heat fixing section. A recording device characterized by comprising: temperature control means.