JP3410243B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of an image forming apparatus such as a copying machine or a printer, and more particularly to a fixing device of an image forming apparatus for controlling a copying speed. 2. Description of the Related Art In a fixing device of an image forming apparatus such as a copying machine, the quality of fixing an image on copy paper depends on a change in the surface temperature of a heating roll. Also, after the power is turned on or when the number of copies is large, the surface temperature of the heating roll is in a low temperature state. In such a case, good copying cannot be performed unless the heating roll is rotated at a low speed. There is a problem that the time required is long. For this reason, Japanese Patent Laid-Open Publication No. 56-25754 discloses that the temperature of a heating roll is detected, and when the temperature of the heating roll is higher than a predetermined temperature, the drive system is driven at a high speed. Devices for driving the system at low speed have been proposed. [0004] However, in the apparatus described in the above-mentioned publication, even if the temperature of the heating roll is equal to or higher than the predetermined temperature, for example, when the temperature of the pressure roll in contact with the heating roll is cooled, The temperature immediately drops, the temperature of the heating roll falls below a predetermined temperature, and the copying must be performed at a low speed. Since the temperature of the heating roll does not rise until the pressure roll is warmed, there is a disadvantage that the time of low-speed rotation becomes longer when copying a large number of sheets, and the time until the copying is completed becomes longer. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that can quickly maintain the temperature of a heating roll at an appropriate temperature regardless of the number of copies, thereby shortening the overall copying time. According to the present invention, in an image forming apparatus capable of changing a copying speed, the number of copies is detected by detecting the number of copies.
When the number of copies is equal to or less than a predetermined number, copying is started at a high copy speed (high-speed rotation or high CPM). When the number of copies is equal to or more than a predetermined number, copy is performed at a low copy speed (low-speed rotation or low CPM). Start, when the heating roll temperature falls below the predetermined temperature, and then exceeds the predetermined temperature,
The copying speed is switched at a high speed. When the number of copies is detected and the number of copies is equal to or less than a predetermined number, copying is started at a high copying speed. Further, when the temperature of the pressure roll is detected and the temperature is equal to or higher than a predetermined temperature, copying may be started at a high copying speed, and the copying speed may be switched when the temperature is equal to or lower than the predetermined temperature. Means are provided for switching the copying speed between the time when the main power of the image forming apparatus is turned on and a predetermined number of copies or the time when the main power is turned on for a predetermined time. The image forming apparatus according to the present invention detects the number of copies and starts copying at a high copying speed when the number of copies is equal to or less than a predetermined number. Start copying at a low speed, and switch the copying speed to a high speed when the heating roll temperature falls below a predetermined temperature and then exceeds a predetermined temperature, or after a predetermined number of sheets is less than the predetermined number of sheets. By
Regardless of the number of copies, the image can be fixed in the shortest copy time. Further, by detecting the temperature of the pressure roll, in the case of more than the predetermined temperature, to begin replication copying speed at a high speed, for switching the copying speed when a predetermined temperature below this <br / Thus, the image can be fixed in the shortest copy time regardless of the number of copies. Immediately after the power is turned on, the pressure roll remains cold even if the heating roll is heated, but after a predetermined number of copies or after a predetermined time has elapsed, the pressure roll is also turned off by heat conduction. since the pressurized hot during copying from the time of the main power-on of the image forming apparatus to a predetermined number or a predetermined time from the time when the main power is turned on, by performing the switching of the copying speed, regardless somewhat number of copies, the shortest The image is fixed in the copying time of. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below based on embodiments with reference to the drawings. In FIG. 1, a heating roll 1 of a fixing device is shown.
Is in contact with a pressure roll (not shown),
The lamp 2 is disposed in the axial direction, and power is supplied to the lamp 2 from a power supply 6 through a power control circuit 5 to heat the heating roll 1. The temperature of the heating roll 1 is
The temperature is detected by a temperature detection sensor 3 disposed on the surface of the heating roll 1, and the detection signal is input to the CPU 4.
The power control circuit 5 is configured to operate based on a command signal from the CPU 4. FIG. 2 shows the relationship among the copying time, the temperature of the heating roll, and the copying speed. At the time T1, the surface temperature of the heating roll 1 is maintained at t1. When the number of copies is equal to or greater than a predetermined number, after the copy start time T1, the rotation speed of the heating roll 1, that is, the copying speed is driven at a low speed n1, and the temperature of the heating roll 1 decreases from t1 to a predetermined temperature t1.
The temperature gradually rises again and reaches a predetermined temperature t3 at time T2. Here, the copying speed is switched from the low speed n1 to the high speed n2. Thereafter, the temperature of the heating roll 1 gradually rises, and the state where high-speed copying is possible is continued. Referring to the flow chart of the embodiment of the present invention shown in FIG.
When a copy start signal is input from the CPU (step 1), CP
U4 determines whether the number of copies N is greater or less than the predetermined number N0. If the number of copies N is less than the predetermined number N0 (N <N0) (step 2), the copying speed is increased (rotation or high speed). Copying is performed by CPM) (step 3). Conversely, the number of copies N is greater than the predetermined number N0 (N>
N0) (Step 4), first, copying is started at a low copying speed (Step 5), and when the heating roll temperature t falls below the predetermined temperature t2 (Step 6), and then exceeds the predetermined temperature t3 (Step 5). Step 7), the copying speed is switched to high speed, and high-speed copying is started (step 3). When the heating roll temperature t is higher than the predetermined temperature t2 (step 8), copying is continued at a low speed (step 5), and when the temperature is lower than the predetermined temperature t3 (step 9), Copying at a low speed is continued (step 6). Further, the switching from the low-speed copying speed to the high-speed copying speed can be performed not according to the temperature change of the heating roll 1 but according to whether the number of copies C is larger or smaller than a predetermined number of copies NX. Is shown in FIG. In FIG. 4, when a copy start signal is input from the input device 7 (step 10), the CPU 4 determines whether the number N of copies is larger or smaller than the predetermined number N0, and when N <N0 (step S10). 11), copying is performed at a high copying speed (step 12), and when N> N0 (step 13), first, copying is started at a low copying speed (step 14), and the number of copies C becomes a predetermined number of copies NX
If not reached (step 15), the copying speed is switched to high speed (step 12). The number of copies C
Is larger than the predetermined number of copies NX (step 16),
Copying at a low speed is continued as it is (step 14). Further, it is also possible to perform low-speed copying after the warm-up time has elapsed after the main power source 6 of the image forming apparatus is turned on, and to switch to high-speed copying after a predetermined time has elapsed. According to the present invention, when the number of copies is small, copying is performed at a high copying speed, so that copying is completed in the shortest copying time. Conversely, even when the number of copies is large, the copying speed is reduced while heat is taken by the pressure roll, so that the pressure roll can be sufficiently heated. After the roll has warmed up, the copying speed is switched to a high speed, so that the overall copying time can be shortened and the productivity is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating a relationship among time, copy speed, and heating roll temperature of the image forming apparatus according to the present invention. FIG. 3 is a flowchart of switching a copying speed based on detection of the number of copies and a heating roll temperature according to the present invention. FIG. 4 is a flowchart of switching a copying speed according to the number of copies according to the present invention. [Description of Signs] 1: Heating roll 2: Heater 3: Temperature detection sensor
4: Central processing unit (switching means) 5: Power control circuit (switching means) 6: Power supply (main power supply) 7: Input device T1: Time T2: Time T1: Copy start n
1: low speed n2: high speed t1: surface temperature t2
: Predetermined temperature t3: predetermined temperature N: number of copies N0: predetermined number NX: predetermined number of copies C: number of copies

Claims (1)

(57) [Claims 1] In an image forming apparatus capable of changing a copying speed, when the number of copies is less than a predetermined number, copying is started at a high copying speed, and the number of copies is more than a predetermined number. An image forming apparatus comprising: means for starting copying at a low copying speed, and switching the copying speed to a high speed when the heating roll temperature falls below a predetermined temperature and thereafter exceeds a predetermined temperature. .