JP2001075415A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device yielding excellent quality images by preventing fixation failure and fixation offset. SOLUTION: In this image forming device provided with paper sheet size detecting means, a pressure roller 17 and a fixing roller 16, a fixing device device 7 equipped with a fixing roller 16, a pressure roller 17 and a temp. detecting means for detecting and outputting the temp. of a fixing roller 16 and moreover a controlling means performing a specific temp. control based on the output of temp. detecting means, first, second and third temp. detecting means are provided, among which the first and the second temp. detecting means are respectively arranged on both sides of the third detecting means and moreover made freely shiftable over a shaft direction of the fixing roller 16 in accordance with a paper sheet size of transfer paper. The detection values of a plurality of times respectively detected by the first, second and third temp. detecting means are individually averaged, these average values of the three detection values are compared and fixing temp. control is performed on the basis of the lowest detection value thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus using an electrophotographic process such as a printer and a facsimile.

[0002]

2. Description of the Related Art Conventionally, as a fixing device used in this type of image forming apparatus, for example, Japanese Utility Model Laid-Open No. 52-29147 discloses one temperature detecting means by a driving means together with the rotation of a fixing roller. Are parallelly moved in the axial direction of the fixing roller, the surface temperature of the fixing roller is detected averagely over a wide range, and the temperature of the fixing device is controlled based on the average value thus detected. I have.

[0003]

However, in a fixing device used in the above-described conventional image forming apparatus,
Since it is necessary to detect the surface temperature of the fixing roller corresponding to the entire sheet width by only one temperature detecting means, it takes a considerable amount of time to detect the temperature. Therefore, there is a problem that accurate temperature detection cannot be performed due to damage. Also,
Since the surface temperature of the fixing roller detected by the temperature detecting means is an average value, it cannot be said that it is optimal for the entire sheet width (entire area), and cannot cope with various types of sheet size paper.
An image defect may occur due to the occurrence of a fixing defect or a fixing offset, which adversely affects the copied image.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional image forming apparatus and to prevent the occurrence of fixing defects and fixing offsets, thereby obtaining a high quality copy image. An image forming apparatus is provided.

[0005]

According to the present invention, in order to achieve the above object, the invention according to claim 1 comprises a paper size detecting means for detecting a paper size of a transfer paper, and a transfer to a transfer paper. A fixing device having a fixing roller and a pressure roller for heating and fixing the formed toner image, a temperature detecting device for detecting a surface temperature of the fixing roller, and a control device for performing predetermined fixing temperature control based on an output of the temperature detecting device In the image forming apparatus provided with, the temperature detecting means has a first temperature detecting means, a second temperature detecting means, and a third temperature detecting means, wherein the first and second temperature detecting means are fixed. The first and second temperature detecting means are arranged on both sides of a third temperature detecting means provided substantially at the center of the roller, and are movable in the axial direction of the fixing roller in accordance with the size of the transfer paper. hand, An average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detection means, the three detection average values are compared, and the lowest detection average value is fixed. The temperature is controlled by selecting the surface temperature of the roller.

According to a second aspect of the present invention, in the first aspect of the invention, three detected average values are compared, and the highest detected average value is selected as the surface temperature of the fixing roller to perform temperature control. It is characterized by the following.

According to a third aspect of the present invention, in the first aspect of the invention, the three detected average values are compared, and the detected average value having the largest difference with respect to the set temperature is determined by the fixing roller. The surface temperature is selected, and temperature control is performed so that the detected average value approaches the set temperature.

According to a fourth aspect of the present invention, in the first aspect of the invention, an average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detecting means. A detection value selected by further averaging the average value is used as the surface temperature of the fixing roller, and the temperature is controlled based on the detection value.

According to a fifth aspect of the present invention, in the first aspect of the invention, an average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detecting means. The average value is further averaged, and if it is determined that the average value has a difference of 1% or more from the set temperature, temperature control is performed so that the average value approaches the set temperature. It is characterized by the following.

[0010]

FIG. 1 shows a basic configuration of an image forming apparatus A according to a first embodiment of the present invention. That is,
As shown in FIG. 1, an image forming apparatus A includes a main body 1 including an image forming unit such as an engine and a photoreceptor, an operation unit 2 for inputting an operation instruction signal to the main body 1, and a main body 1 having a desired paper size. It has paper feeders 3 to 6 for feeding the transfer paper. Reference numeral 7 denotes a fixing device for heating and fixing the unfixed toner on the transfer paper. Here, the basic operation of each of these devices is generally known and will not be described. FIG. 2 is a general block diagram of a circuit configuration according to the image forming apparatus of the present invention. Reference numeral 8 denotes a main body control circuit (control means). The main body control circuit 8 controls the electrical operation of the main body 1. It has a CPU, a ROM, a RAM, and input / output circuits for performing the operations. Reference numeral 9 denotes an operation unit control circuit. The operation unit control circuit 9 has operation input keys for an operator and a display device such as an LED. The operation section control circuit 9 and the main body control circuit 8 are connected by serial communication. Also,
Reference numerals 10 to 13 denote paper feed control circuits for controlling the respective paper feed devices 3 to 6 (FIG. 1). Each of the paper feed control circuits 10 to 13 includes a sensor for detecting a paper size and the like and a paper feed drive. Connected to the main body control circuit 8 in order to output power to a drive motor, clutch, solenoid, etc.

FIGS. 3 and 4 show the structure of the fixing device 7 applied to the image forming apparatus A of the present invention. That is, the fixing device 7 heats and fixes unfixed toner on the conveyed transfer paper. The fixing device 16 includes a fixing roller 16 provided with a heater 15 therein, and a pressing roller 17 that is in pressure contact with the fixing roller 16.
And A first temperature detecting means 18 and a second temperature detecting means 18 are provided on the surface of the fixing roller 16 for detecting a fixing temperature.
Temperature detecting means 19 and the third temperature detecting means 20 are provided. These first, second and third temperature detecting means 18, 19, 20
Are in contact with the fixing roller 16 in a state of being substantially in close contact with the fixing roller 16. Further, as shown in FIG. 3, the first and second temperature detecting means 18 and 19 are arranged on both sides of a third temperature detecting means 20 provided substantially at the center of the fixing roller 16. For this reason, the third temperature detecting means 20 detects the temperature at the approximate center of the fixing roller 16.

A driving device 21 is provided at a substantially central position of the fixing roller 16, and the driving of the driving device 21 causes the first and second temperature detecting means 18 and 19 to move in the axial direction of the fixing roller 16 (see FIG. 3). (Left-right direction). That is, the stays are made to penetrate the drive
The first and second temperature detecting means 18 and 19 are supported by the stay 22 via connecting plates 23 and 23, respectively. Inside the drive device 21, a drive gear and a speed change gear for moving the stay 22 in the axial direction are provided,
Thus, the stay 22 can be moved in the axial direction of the fixing roller 16 by driving the driving device 21. On the other hand, the third temperature detecting means 20 is attached and fixed to the bottom side of the driving device 21 via the connecting plate 23.

Therefore, when the driving of the driving device 21 is started, the stay 22 moves in parallel, and the first and second temperature detecting means 18, 19 also move in parallel with this movement. Here, the operation of the driving device 21 is controlled by an operation signal from the main body control circuit 8 (FIG. 2), and the amount of movement of the first and second temperature detecting means 18 and 19 is determined by selecting the "paper" It will be selected each time according to “size”. For example,
When the “paper size” is A3 paper, the amount of movement of the first and second temperature detecting means 18 and 19 becomes maximum because the paper width is wide.

Hereinafter, the operation of the image forming apparatus according to the present invention will be described in detail. First, when the operator selects (inputs) “paper size” using the operation unit 2 (FIG. 1), this input signal is input from the operation unit control circuit 9 to the main unit control circuit 8 and the operation from the main unit control circuit 8 is performed. Drive device by signal
Drive 21 is started. As described above, this driving device 21
Is performed according to the “paper size” of the selected transfer paper. More specifically, the first and second temperature detecting means 18 and 19 are respectively moved along the surface of the fixing roller 16 to the positions which are the ends of the transfer paper, and the surface temperatures at the positions are detected respectively. Is done. Then, the detected value is read by the main body control unit 8. Such temperature detection by the first and second temperature detecting means 18 and 19 is performed a plurality of times, and an average value of the detected values is calculated. A comparison operation is performed on the three detected average values thus calculated, and the "lowest value" is selected as the surface temperature of the fixing roller 16 to perform temperature control (claim 1). Here, the sampling is performed a plurality of times in order to prevent erroneous sampling of the detection value. Contrary to the above, comparison operation processing is performed on the three detected average values, and thereafter, the "highest value" of the average value is selected as the surface temperature of the fixing roller 16, and temperature control is performed based on this value. In this case, the fixing offset can be prevented and the margin for erroneous detection can be increased (claim 2).

The first, second, and third temperature detecting means 18,
A comparison operation is performed on the three average values detected by 19 and 20, and a value at which the difference between the average value and the set value (set temperature) is maximum is determined as the surface temperature of the fixing roller 16. Then, the surface temperature (detected temperature) of the fixing roller 16 determined in this way and the set value are compared and processed by the main body control circuit 8, and it is determined that the detected temperature is greatly deviated from the set value. Then, the fixing temperature is controlled so that the detected temperature approaches the set value (claim 3). By performing the temperature control so as to approach the set temperature in this way, the error between the determined value and the set temperature can be minimized, so that adverse effects on the copy image can be prevented.

The first, second and third temperature detecting means 18,
The surface temperature of the fixing roller 16 is determined by further averaging the three average values detected by 19 and 20 and performing a comparison operation, and the fixing temperature is controlled based on the detected value. . According to this, since the fixing temperature control can be performed by averaging the set value at the end of the transfer sheet and the set value at the center of the transfer sheet, it is possible to prevent the fixing temperature from excessively rising. Further, the first, second, third temperature detecting means 18, 19,
The average value is calculated for each of a plurality of detection values detected in step 20 and the average value is further averaged, and it is determined that the average value has a difference of 1% or more from the set temperature. In this case, the fixing temperature is controlled so that the average value approaches the set temperature (claim 5). According to this, by controlling the average value to within 1% of the set temperature, it is possible to suppress the temperature fluctuation with respect to the fixing roller 16 when the transfer paper passes.

[0017]

The present invention is as described above. According to the first aspect of the present invention, there is provided a paper size detecting means for detecting a paper size of a transfer paper, and heat fixing of the toner image transferred to the transfer paper. A fixing device including a fixing roller and a pressure roller, a temperature detecting unit that detects and outputs a temperature of the fixing roller, and a control unit that performs predetermined temperature control based on an output of the temperature detecting unit. Has first temperature detecting means, second temperature detecting means, and third temperature detecting means, wherein the first and second temperature detecting means are arranged on both sides of the third temperature detecting means, A movable member which is movable in the axial direction of the fixing roller in accordance with the sheet size of the transfer sheet, and calculates an average value of a plurality of detection values detected by the first, second and third temperature detecting means. And
By comparing these three detected average values and selecting the lowest detected average value as the surface temperature of the fixing roller and performing temperature control, it is possible to prevent the occurrence of defective fixing and to obtain a high quality copy image. Is obtained.

According to a second aspect of the present invention, in the first aspect of the present invention, three detected average values are compared, and the highest detected average value is selected as the surface temperature of the fixing roller to perform temperature control. Therefore, there is an effect that the occurrence of the fixing offset can be prevented and a high-quality copy image can be obtained.

According to a third aspect of the present invention, in the first aspect of the invention, the three detected average values are compared, and the detected average value having the largest difference with respect to the set temperature is determined by the fixing roller. Since the surface temperature is selected and temperature control is performed so that this detected average value approaches the set temperature, reduce the temperature difference between the set value at the end of the transfer paper and the set value at the center of the transfer paper. Further, by controlling the temperature so as to approach a preset temperature, it is possible to reduce the fixing unevenness over the entire area of the transfer paper and obtain a higher quality copy image.

According to a fourth aspect of the present invention, in the first aspect, an average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detecting means. Then, a detection value selected by further averaging the average value is used as the surface temperature of the fixing roller, and the temperature is controlled based on the average value. Therefore, an effect that an excessive rise in the fixing temperature can be prevented can be prevented. is there.

According to a fifth aspect of the present invention, in the first aspect, an average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detecting means. The average value is further averaged, and if it is determined that the average value has a difference of 1% or more from the set temperature, fixing temperature control is performed so that the average value approaches the set temperature. Therefore, it is possible to suppress the fluctuation of the temperature of the fixing roller when passing through the transfer paper, and it is possible to obtain a stable copy image.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an image forming apparatus of the present invention.

FIG. 2 is an overall block diagram showing an example of the circuit configuration.

FIG. 3 is a schematic longitudinal sectional view showing a fixing device to which the present invention is applied.

FIG. 4 is a schematic side view of the same.

[Explanation of symbols]

 A Image forming apparatus 1 Main body 2 Operation section 3, 4, 5, 6 Paper feed section 7 Fixing device 8 Main body control circuit 9 Operation section control circuit 10, 11, 12, 13 Paper feed control circuit 15 Heater 16 Fixing roller 17 Pressure roller 18 First temperature detecting means 19 Second temperature detecting means 20 Third temperature detecting means 21 Drive unit 22 Stay 23 Connecting plate

Claims (5)

[Claims] 1. A sheet size detecting means for detecting a sheet size of a transfer sheet, a fixing roller and a pressure roller for heating and fixing a toner image transferred to the transfer sheet, and a temperature detecting means for detecting a surface temperature of the fixing roller. And a control unit for performing predetermined fixing temperature control based on the output of the temperature detection unit, the temperature detection unit includes a first temperature detection unit, a second temperature detection unit, Third
And first and second temperature detecting means are disposed on both sides of a third temperature detecting means provided substantially at the center of the fixing roller. The detecting means is movable in the axial direction of the fixing roller in accordance with the size of the transfer paper, and is an average value of a plurality of detection values detected by the first, second and third temperature detecting means. An image forming apparatus comprising: calculating the three detected average values; selecting the lowest detected average value as the surface temperature of the fixing roller; and performing temperature control. 2. The image forming apparatus according to claim 1, wherein the three detected average values are compared, and the highest detected average value is selected as the surface temperature of the fixing roller to perform temperature control. 3. A method for comparing three detection average values,
2. The apparatus according to claim 1, wherein a detected average value having the largest difference with respect to the set temperature is selected as a surface temperature of the fixing roller, and temperature control is performed such that the detected average value approaches the set temperature. Image forming device. 4. A detection value selected by calculating an average value of a plurality of detection values detected by each of the first, second, and third temperature detection means, and averaging the average values. 2. The image forming apparatus according to claim 1, wherein is a surface temperature of the fixing roller, and temperature control is performed based on the detected value. 5. An average value is calculated for each of a plurality of detection values detected by the first, second, and third temperature detection means, and the average value is further averaged, and the average value is set. 2. The image forming apparatus according to claim 1, wherein when it is determined that there is a difference of 1% or more with respect to the temperature, temperature control is performed such that the average value approaches the set temperature.