JPH04346384A - Temperature control of fixing device and device thereof - Google Patents

Abstract

PURPOSE:To diminish fixing temperature change caused by a change in paper sheet size or the number of feed paper sheets by setting a heating range of a heating device properly while detecting the paper sheet size at a fixing time, and giving heating compensation for temperature drop of a heating roll optimally by means of the heating device while detecting the number of printing paper sheets or the paper sheet position at all times. CONSTITUTION:A temperature control device for a fixing device is provided with a paper sheet detecting unit 7 to detect information on size, kind and so on of image recording paper sheets, a position detecting unit 8 to detect information on the position and so on of the image recording paper sheets, an inside detecting unit 5 to detect inside temperature of a heating roll 1 having an integral inside heating device 3, an outside detecting unit 6 to detect surface temperature of the heating roll 1, and a central control unit 9 to process these results, an inside control unit 10 to control the inside heating device 3 and an outside control unit 11 to control an outside heating device 4.

Description

[Detailed description of the invention]

0001

0001

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling the temperature of a fixing device in an image forming apparatus such as an optical printer or a copying machine.

0003

0002

0004

2. Description of the Related Art An optical printer will be described below as an example of an image forming apparatus.

[0005]

The fixing device has a heating roll with a built-in internal heating device and a pressure roll that comes into pressure contact with the heating roll, and the image recording paper passes between the two rolls (hereinafter referred to as
It is called "passing paper." ), the toner image is heated and pressurized and fixed on the image recording paper.

[0006]

The heating roll has an internal heating device, a cylindrical core surrounding the internal heating device, and a flexible elastic member such as rubber attached to the outer peripheral surface of the core. On the other hand, the pressure roll has a cylindrical core made of the same material as the heating roll, and a thin surface layer of a resin with releasability that prevents the toner image from adhering to the outer peripheral surface of the core. ing. The surface temperature of the heating roll is detected using a thermistor, etc.
The internal heating device is controlled so that the detected temperature is constant.

[0007]

However, since the heat of the heating roll is absorbed by the image recording paper as the paper passes through the paper, its surface temperature tends to decrease. Therefore, when continuous printing is performed, fixing is performed on the second and subsequent image recording sheets at a temperature lower than a predetermined temperature, so that sufficient fixing is not performed and problems such as poor fixing occur. On the other hand, there is also a method of detecting a temperature drop in the heating roll and heating the surface of the roller with a second heating means based on the detection result. If the temperature drop becomes large, the temperature of the second heating means is increased to compensate, which causes the second heating means to reach a higher temperature than necessary, and the second heating means continues to heat even after the fixing operation is completed. The roller may continue to be heated, which may have an adverse effect on the elastic member, etc.

[0008]

[0006] Therefore, a temperature control method and apparatus have been proposed in which the temperatures of the heating roll and the external heating device are detected and the external heating device is controlled based on the detection results.

[0009]

The technology described in JP-A-64-52184 includes (1) a fixing device having a heat roller with a built-in heater, a pressure roller that comes into pressure contact with the heat roller, and an external heating device that heats the heat roller; A temperature control method for a fixing device, characterized in that the temperature of the heat roller and an external heating device is detected, and the external heating device is controlled based on the detection result.

0010

(2) A first detection means for detecting the surface temperature of a heat roller with a built-in heater, a second detection means for detecting the temperature of an external heating device that heats the heat roller, and detection of these detection means. A temperature control device for a fixing device, comprising: a control section that controls the external heating device in response to a result.

[0011]

(3) The control section includes a bridge circuit in which the first detection means and the second detection means are connected in parallel, a comparator that compares the output of the bridge circuit with a reference voltage, and a 3. The temperature control device for a fixing device according to claim 2, further comprising an on/off means for turning on and off the external heating device. (4) The temperature control device for a fixing device according to claim 2, wherein the external heating device is a roller that comes into contact with a heat roller and has a built-in heater. (5) The temperature control device for a fixing device according to claim 2, wherein the external heating device is a heating lamp installed near the heat roller and having a reflecting plate.

0012

[0010]

[0013]

[0011]

[0014]

[Problems to be Solved by the Invention] However, in the temperature control method and device described in the above-mentioned Japanese Patent Application Laid-Open No. 64-52184, the surface temperature of the heat roller and the temperature of the external heating device are detected by the first and second detection methods. In order to control the external heating device based on the detection result, the external heating device compensates for the temperature drop on the roller surface. However, when the size of the image recording paper changes in the axial direction of the roller, the roller surface There will be a difference in temperature. For this reason, when the external heating device heats the heat roller, there are parts where the temperature exceeds the required temperature, which adversely affects the materials of the heat roller's elastic members and the like.

[0015]

The present invention was devised in consideration of the above circumstances, and uses information such as the size and type of the image recording paper and information such as the position of the image recording paper to appropriately adjust the heating device and heating width. It is an object of the present invention to provide a temperature control method and apparatus for a fixing device that can obtain stable fixing performance by controlling the temperature.

[0016]

[0013]

[0017]

[Means for Solving the Problems] A temperature control method for a fixing device according to the present invention includes a heating roll having a built-in internal heating device, a pressure roll that is in pressure contact with the heating roll, and an external heating device that heats the heating roll by radiation. This method detects information such as the size and type of image recording paper, information such as the position of the image recording paper, detects the temperature of the heating roll, and sends these results to the The control unit processes the internal heating device or external heating device appropriately.

[0018]

Further, the temperature control device for a fixing device according to the present invention includes a paper detecting section that detects information such as the size and type of image recording paper, a position detecting section that detects information such as the position of the image recording paper, An internal detection unit that detects the internal temperature of the heating roll with a built-in internal heating device, an external detection unit that detects the surface temperature of the heating roll, a central control unit that processes these results, and an internal detection unit that controls the internal heating device. It has a control section and an external control section that controls the external heating device.

[0019]

Further, in the temperature control device of the fixing device according to the present invention, the heating width of the internal heating device and the external heating device can be changed in accordance with the size of the image recording paper by means of a plurality of heating sections divided in the axial direction. can.

[0020]

[0016]

[0021]

[Operation] The paper detection section detects information such as the size and type of the image recording paper, and based on this result, adjusts the heating width of the internal and external heating devices appropriately, and also detects the position of the image recording paper, etc. Based on this result, the heating amount of the internal and external heating devices is appropriately controlled.

[0022]

On the other hand, when the surface temperature of the heating roll decreases as the image recording paper passes between the heating roll and the pressure roll after printing is started, this temperature drop is detected by an external detection section; Based on the detection results, such as the size of the image recording paper, the external heating device is controlled to have an optimum heating width and appropriately radiant heats the heating roll. When the surface of the heating roll is radiantly heated, the external detection section detects this fact, and the external heating device is controlled based on the detection result.

[0023]

If the internal temperature decreases even after heating the surface of the heating roll, this temperature decrease is detected by the internal detection section, and based on the detection result and the detection result of the position of the image recording paper, etc. will properly heat the heating roll from the inside. When the inside of the heating roll is heated, the internal detection section detects this fact, and the internal heating device is controlled based on the detection result.

[0024]

[0019]

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[0026]

FIG. 1 is a schematic diagram of a temperature control device for a fixing device according to the present invention. The heating roll 1 incorporating the internal heating device 3 has a core metal 17 made of aluminum or the like, and an elastic member 16 made of rubber or the like fixed to the outer peripheral surface of the core metal 17 with an adhesive or the like. Inside the heating roll 1, that is, inside the core metal 17, an internal detection section 5 consisting of a thermistor or the like is provided.
On the outside of the heating roll 1, that is, on the surface of the elastic member 16, an external detection section 6 consisting of a thermistor or the like and an external heating device 4 are installed in the vicinity thereof. This heating roll 1
rotates in the direction of arrow A shown in FIG.

[0027]

[0021] The pressure roll 2 is in pressure contact with the heating roll 1, and has a core made of aluminum or the like and is coated with Teflon (trade name).
It is coated with synthetic resin such as. The pressure roll 2 rotates in the direction of arrow B following the rotation of the heating roll 1.

[0028]

As the image recording paper for printing is passed between the heating roll 1 and the pressure roll 2 in the direction of arrow C shown in FIG. 1, the toner image is heated and pressed onto the image recording paper. It will be established.

[0029]

The central control section 9 processes the information from the paper detection section 7 that detects the size and type of the image recording paper and the information from the position detection section 8 that detects the position of the image recording paper, and processes the information from the internal control section 1.
0 and an external control section 11, the internal control section 10 and the external control section 11 include an internal detection section 5 that detects the internal temperature of the heating roll 1, and an external detection section 6 that detects the surface temperature. The internal heating device 3 and the external heating device 4 are appropriately controlled according to the detection results and the control of the central control unit 9.

[0030]

The internal heating device 3 and the external heating device 4 are composed of a plurality of heating sections divided in the axial direction, and adjust the heating width in the axial direction based on the size of the image recording paper detected by the paper detection section 7. Change appropriately. To explain this with the temperature distribution diagram of the conventional heating roll 1 shown in FIG. In the temperature distribution 15 at the time, the temperature changes in the axial direction of the heating roll 1, and this is a means for dealing with this phenomenon.

[0031]

Next, control operations of the central control section 9, internal control section 10, and external control section 11 will be explained with reference to flowcharts shown in FIGS. 2 and 3. When the optical printer is powered on, the central control section 9 issues a heating control command (S1) to the internal control section 10 and the external control section 11. The internal control unit 10 and external control unit 11 that received this command execute S01. In S02, the temperature inside and on the surface of the heating roll 1 is compared with the fixing temperature, and if the temperature is not the fixing temperature, the process goes to S04, and if the fixing temperature is the same, the process goes to S03. The central control unit 9 waits until the fixing preparation is completed in S2, and when the fixing preparation is completed, it issues a heating end command (S3) to the internal control unit 10 and the external control unit 11. The internal control unit 10 and external control unit 11 that have received this command end the heating control (S03). The paper detection unit 7 detects the size, type, and number of print sheets of the image recording paper (S4), and based on the results, the heating widths of the internal heating device 3 and the external heating device 4 are optimized (S5).

[0032]

When printing is started (S6), S1 is then executed to shift to an operation for compensating for the temperature drop of the heating roll 1. The position of the image recording paper is detected by the position detection section 8 (S7),
Detection is performed at any time (S7) until the end of fixing (S8). During this time, the temperature of the heating roll 1 is being controlled in parallel.
The fixing temperature is controlled to an appropriate level. The fixing operation ends (S
8) and the heating control of the heating roll 1 is completed (S3), and the fixing operation is completed.

[0033]

[0027]

[0034]

[Effects of the Invention] According to the present invention, since the heating roll is heated from inside and outside simultaneously, the waiting time until the fixing operation can be shortened. Since the external heating device is configured to detect a decrease in surface temperature and appropriately compensate for heating according to the result, the fixing temperature does not fluctuate due to changes in the amount of paper passing. Therefore, the occurrence of fixing failures is reduced.

[0035]

Furthermore, since the size of the image recording paper is detected and the heating width of the internal and external heating devices is optimally changed, heating control can be performed appropriately to reduce the temperature on the surface of the heating roll. The heating roll is heated, and the completion of fixing is immediately detected and heating of the internal and external heating devices is stopped, so that excessive heating of the heating roll does not occur.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a temperature control device for a fixing device according to the present invention.

FIG. 2 is a flowchart showing control operations of a central control unit.

FIG. 3 is a flowchart showing control operations of internal and external control units.

FIG. 4 is a temperature distribution diagram of a heating roll of a conventional fixing device.

[Explanation of symbols]

1... heating roll, 2... pressure roll, 3... internal heating device,
4... External heating device, 5... Internal detection section, 6... External detection section,
7...Paper detection section, 8...Position detection section, 9...Central control section, 1
0... Internal control section, 11... External control section.

Claims (3)

[Claims] Claim 1: A heating section comprising a heating roll with a built-in internal heating device, a pressure roll that presses against the heating roll, and an external heating device that heats the heating roll by radiation, and is divided into a plurality of parts in the axial direction. In the temperature control method of the fixing device, which is composed of internal and external heating devices whose heating width can be changed by , and detecting the temperature of a heating roll, and appropriately controlling an internal heating device or an external heating device based on these results. Claim 2: A paper detection unit that detects information such as the size and type of the image recording paper, a position detection unit that detects information such as the position of the image recording paper, and an internal temperature of a heating roll that includes an internal heating device. an internal detection section that detects the surface temperature of the heating roll, an external detection section that detects the surface temperature of the heating roll, a central control section that processes these results, an internal control section that controls the internal heating device, and an external detection section that controls the external heating device. 1. A temperature control device for a fixing device, comprising: a control section; the internal heating device and the external heating device are capable of changing the heating width by means of a plurality of heating sections divided in the axial direction. Claim 3: The external heating device is installed near the heating roll, the internal heating device and the external heating device can simultaneously heat the heating roll, and the internal heating device and the external heating device correspond to the size of the image recording paper. 3. The temperature control device for a fixing device according to claim 2, wherein the heating width can be changed by changing the heating width.