JPH1124493A - Copying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copying device by which copy possible number per unit time is not limited when set consecutive copy number is equal to or less than specified number. SOLUTION: When the width of a transfer paper is smaller than that of a maximum copy possible transfer paper, for example, A4-size length(S10; Y), the set consecutive copy number is the specified number, for example, <=10 (S11; N) the copy control of 12 cpm is performed (S12). On the other hand, when the set consecutive copy number is equal to or more than the specified number, for example, >=10 (S11; Y), the copy control of 7 cpm is performed (S13). Temperature rising on the end part of a fixing roller is caused by the accumulation of the copy consecutive number of the transfer paper with small width. Consequently, when the temperature rising is within limit where fixing offsetting and fixing wrinkle occur(within 10 here), the limit of the copy possible number per the unit time is not required to be applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying apparatus which limits the number of copies that can be made per unit time when copying a transfer sheet narrower than the maximum transferable copy sheet width.

[0002]

2. Description of the Related Art In a conventional copying apparatus, after turning on a main switch (SW), in order to quickly reach the surface temperature of a fixing roller at which copying is possible, the core of the fixing roller is thinned or the wattage of a fixing heater is reduced. Was relatively large. In these copying apparatuses, especially when the width of the transfer sheet is narrower than the maximum transfer sheet width that can be copied, the surface temperature of the end portion of the fixing roller becomes higher than the center portion, exceeds the appropriate surface temperature, and the fixing offset, fixing There is a high possibility that a problem such as generation of wrinkles will occur. This problem is caused by the fact that the temperature sensor that detects the surface temperature of the fixing roller and feeds it back to the control circuit is usually installed at the center of the fixing roller when copying transfer paper with a narrow width continuously. It is because it is. That is, since the central portion of the fixing roller absorbs heat by the transfer paper and the fixing heater is controlled to heat, the end of the fixing roller rises in temperature due to the amount of heat because there is no transfer paper. Will occur. Therefore, the number of copies that can be made per unit time of the copying apparatus has been limited.

[0003]

When the width of the transfer sheet is smaller than the maximum transfer sheet width at which copying can be performed, the surface temperature of the end portion of the fixing roller becomes higher than that of the center portion and exceeds the proper surface temperature. Is a case in which copying of transfer paper having a narrow width is continuously performed. For example, in the case of A4 length as described below, the process conditions under which normal 12 cpm (cpm: the number of copies per minute) can be obtained. Nevertheless, 7cp
m. A4 landscape: 15 cpm A4 length: 7 cpm B4: 10 cpm A3: 9 cpm However, in a few copying processes that are normally used, the surface temperature of the end portion of the fixing roller becomes higher than the central portion and exceeds an appropriate surface temperature. There is no possibility that problems such as fixing offset and occurrence of fixing wrinkles will occur. Therefore, it is not desired to limit the number of copies that can be made per unit time in the normally used copying process for several sheets.

Accordingly, an object of the present invention is to provide a copying apparatus which does not limit the number of copies that can be made per unit time if the set number of continuous copies is equal to or less than a predetermined number.

[0005]

According to the first aspect of the present invention, in a copying apparatus provided with a heater for heating a fixing roller and a power supply means for supplying power to the heater, the maximum possible copy is provided. Limiting means for limiting the number of copies per unit time when copying transfer paper narrower than the transfer paper width, and limit releasing means for releasing the limitation by the limiting means when the designated number of copies is less than a predetermined number. The above object is achieved by providing the following.

According to a second aspect of the present invention, in the copying apparatus of the first aspect, the above object is achieved by further comprising setting means for setting a predetermined number of sheets for canceling the limitation by the limitation canceling means. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a schematic diagram of a fixing device of a copying apparatus according to the present embodiment and a diagram showing a positional relationship between a temperature sensor and the fixing device. Generally, if a plurality of temperature sensors 16 are provided at intervals in the axial direction of the fixing roller 12 and optimal control is performed using heaters 10 having different heat generation distributions in the axial direction of the plurality of fixing rollers 12, The temperature distribution in the axial direction can be made constant regardless of the size of the transfer paper, but the cost is high. Therefore, a single machine is used in a low cpm machine. In FIG. 1, A indicates the A4 vertical width, and B indicates the A4 horizontal width.

FIG. 2 shows that in this embodiment, after the main switch is turned on, in order to quickly reach the surface temperature of the fixing roller capable of copying, the core of the fixing roller is made thinner or the W number of the fixing heater is relatively reduced. FIG. 9 is a conceptual diagram of a rising curve of the surface temperature at the end and the center of the fixing roller when the width of the transfer sheet is smaller than the maximum transfer sheet width that can be copied in a copying apparatus having a larger size.

That is, when the width of the transfer paper is narrower than the maximum transfer paper width that can be copied, (for example, when the A4 paper is A4 lengthwise), the continuous fixing of the transfer paper having the narrow width is usually performed. A temperature sensor 16 that detects the surface temperature of the roller and feeds it back to the control circuit is provided at the center of the fixing roller 12. Therefore, the central portion of the fixing roller 12 absorbs heat by the transfer paper, and the fixing heater 10 is controlled to heat. Therefore, the temperature of the end portion of the fixing roller 12 rises due to the amount of heat because there is no transfer paper, and a temperature difference occurs with the central portion of the fixing roller 12.

The temperature rise at the end of the fixing roller 12 is as follows.
This is caused by the accumulation of the number of continuous copies of transfer paper having a narrow width. Therefore, if the temperature rise is within the limits of the occurrence of the fixing offset and the fixing wrinkle, the limitation of the number of copies that can be made per unit time is not applied.

FIG. 3 is a flowchart showing a processing procedure of the present embodiment. When the width of the transfer paper is smaller than the maximum transfer paper width that can be copied, for example, in the case of A4 length (Step 10; Y), the set number of continuous copies is a predetermined number of copies.
For example, if the number is 10 or less (step 11; N), 12
Cpm copy control is performed (step 12). On the other hand, if the set number of continuous copies is equal to or more than a predetermined number, for example, 10
If the number is equal to or greater than the number of sheets (step 11; Y), the copy control of 7 cpm is performed (step 13).

[0012]

According to the first aspect of the present invention, even if the width of the transfer sheet is narrower than the maximum transfer sheet width that can be copied, if the set number of continuous copies is equal to or less than a predetermined number, the number of copies per unit time is reduced. Since the number of copies that can be made is not limited, an efficient copying operation can be performed without reducing the copying speed even if the width of the transfer paper is narrow. According to the second aspect of the present invention, since the setting unit sets the predetermined number of sheets for canceling the limitation by the limitation canceling unit, efficient copying can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a fixing device of a copying apparatus according to an embodiment and a diagram illustrating a positional relationship between a fixing device and a temperature sensor.

FIG. 2 is a conceptual diagram of a surface temperature rise curve of an end portion and a center portion of a fixing roller when the width of a transfer sheet is smaller than a maximum transfer sheet width that can be copied;

FIG. 3 is a flowchart illustrating a processing procedure according to the embodiment.

[Explanation of symbols]

 Reference Signs List 10 fixing heater 12 fixing roller 14 pressure roller 16 temperature sensor

Claims (2)

[Claims] A heater for heating a fixing roller;
In a copying apparatus having a power supply unit for supplying power to the heater, when copying a transfer sheet narrower than the maximum copyable transfer sheet width, a limiting unit that limits the number of copies per unit time; A copy canceling means for canceling the limitation by the limiting means when the designated number of copies is equal to or less than a predetermined number. 2. The copying apparatus according to claim 1, further comprising setting means for setting a predetermined number of sheets for canceling the limitation by said limitation canceling means.