JPH0323912B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a fixing device installed in a copying machine, etc.
More specifically, the present invention relates to a fixing device that can successfully fix both large-sized paper and small-sized paper. [Prior Art] Generally, in the fixing device of a copying machine, a heat source such as a Kortz lamp is provided inside the heating roll, and the heating roll is heated to a predetermined temperature by the light emitted from the lamp, thereby fixing the toner image. Provides heat as needed. Then, the copy paper on which the toner image has been developed is passed through a nip between a heating roll and a pressure roll that rotate in pressure contact with each other, and fixing is performed using heat supplied from the Kortz lamp. Therefore, the amount of heat consumed from the circumferential surface of the heating roll for fixing is different between large-sized paper and small-sized paper. Therefore, it is necessary to control the temperature on the circumferential surface of the heating roll when fixing large-sized paper and small-sized paper. That is, it is necessary to set the heating roll peripheral surface temperature within a range that is higher than the minimum fixing temperature necessary for fixing and lower than the hot offset temperature. Conventionally, the following method has been used to detect the surface temperature of a heating roll for performing these temperature controls. () A single Coltz lamp is provided as a heat source for the heating roll, and one temperature sensor detects the light emission temperature of the single Coltz lamp. () A plurality of Colts lamps are provided as a heat source for the heating roll, and one temperature sensor detects the light emission temperature of the plurality of Colts lamps. () A single Coltz lamp is provided as a heat source for the heating roll, and a plurality of temperature sensors detect the light emission temperature of the single Coltz lamp. () A plurality of Colts lamps are provided as a heat source for the heating roll, and a plurality of temperature sensors detect the light emission temperature of the plurality of Colts lamps. [Problems to be Solved by the Invention] The conventional methods described above have the following problems. That is, in the case of (), it is not possible to detect the temperature of the entire heating roll with only one temperature sensor because the temperature distribution is different between the center and both ends of the heating roll. It is difficult to achieve both good fixing performance for large-sized paper and suppression of temperature rise during continuous feeding of small-sized paper. In the case of (), the set temperature distribution can be improved by using a plurality of Kortz lamps, but the cost is high and temperature detection cannot be achieved completely. In the case of () and (), temperature detection can be performed completely, but the cost is high. The present invention has a simple structure, low cost, and completely detects the temperature of the heating roll with a detected value without variation, and adjusts the peripheral surface temperature of the heating roll to within the allowable fixing temperature range to achieve good fixing. The object of the present invention is to provide a fixing device for a copying machine that includes a temperature sensor and a heat source. [Means and effects for solving the problem] The present invention provides a temperature sensor disposed near the heating roll so that the detection surface of the sensor can be directed in a range from one end to the center of the heating roll. This makes it possible to completely detect the peripheral surface temperature at the ends and center of the heating roll with consistent detection values, and adjust the fixing temperature to an appropriate temperature for good fixing. This is what I did. [Example] The present invention will be described below based on an example shown in the drawings. 1 and 2, reference numeral 1 denotes a fixing device, which is composed of a heating roll 2 and a pressure roll 3. In FIG. The heating roll 2 is provided with one Kortz lamp 4 as a heat source inside, and the peripheral surface is covered with a heat-resistant elastic body 5. Further, the circumferential surface of the pressure roll 3 side is also coated with a heat-resistant elastic body 6. The heating roll 2 and the pressure roll 3 are in pressure contact with each other to form a nip part N, and by passing the paper to which the toner image a has been transferred through this nip part N, the toner image a is fixed. This is done by heat fusion. Note that 7 is a peeling claw that peels off the paper after fixing. Since the heat of the heating roll 2 is consumed for thermal fusion, the temperature of the circumferential surface of the heating roll 2 changes. Therefore, in order to detect the peripheral surface temperature of the heating roll 2, an infrared non-contact type temperature sensor 8 is arranged near the heating roll 2, and the detection surface of the temperature sensor 8 is oriented in the axial direction of the heating roll 2. In particular, the peripheral surface temperature of the heating roll 2 can be detected at the edge A of the maximum size paper and the central part B of the heating roll. As shown in FIG. 3, the temperature sensor 8 is connected to a substrate 9a.
It is attached to the bracket 9b set upright on the same board 9a.
It is designed to be able to rotate around a vertical support shaft 9c that pivots. A bracket 9d is fixedly mounted on the substrate 9a, and a solenoid 10 is connected to the bracket 9d so that the temperature sensor 8 can be rotated by the operation of the solenoid 10. Large size paper b ₁ for Figures 4, 5 and 6
2 shows how to detect and control the circumferential surface temperature of the heating roll 2 and changes in the circumferential surface temperature when fixing on small size paper _B2 and when fixing on small size paper B2. As shown in Figure 4, when fixing large size paper _B1 , the temperature distribution is set as shown in the diagram L1 in Figure ₆ during standby, so the peripheral surface at the edge A of the largest size paper is The temperature is at its lowest. Therefore, the surrounding surface temperature at point A is the minimum fixing temperature.
It is sufficient to control T to ₁ or more. That is, the Kortz lamp 4 is turned on to prevent the temperature from falling below the minimum fixing temperature _T1 . Furthermore, even if heat is consumed due to thermal fusing in the central part B of the heating roll, the peripheral surface temperature at the central part B of the heating roll remains within the allowable fixing temperature range, and detection of the peripheral surface temperature is particularly important. No. Next, as shown in Figure 5, small size paper b ₂
When fusing is performed by continuously feeding the heating roll 2,
Only the central portion of the heating roll 2 contacts the small-sized paper b ₂ and heat is consumed, and the temperature of the circumferential surface of both end portions of the heating roll 2 rises with time, resulting in a temperature distribution as shown in the diagram L ₂ of FIG. 6, At both ends of the heating roll 2, the hot offset temperature T ₀ or higher is reached. When the Kortz lamp 4 is turned off, the temperature of each part of the heating roll 2 drops uniformly, as shown in the diagram _L3 in FIG _. If controlled so that the temperature at both ends becomes below the hot offset temperature _T0 , the temperature at the circumferential surface of the heating roll 2 can be controlled within the allowable fixing temperature range as a whole. The following table shows how the temperature sensor 8 detects the peripheral surface temperature at the edge A of the maximum size paper and the center B of the heating roll to control the temperature.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to detect the circumferential surface temperature of the center and end portions of the heating roll with one temperature sensor, so that the temperature of the circumferential surface during fixing of large-sized paper and small-sized paper can be detected. It can be adjusted and provides good fusing regardless of the size of the paper, reduces costs, and has the advantage of more accurate temperature control with no variation in detected values compared to using multiple temperature sensors. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional plan view of one embodiment of the present invention, and FIG.
The figure is a cross-sectional side view of the same, Figure 3 is an explanatory diagram of the rotation mechanism,
FIG. 4 is an explanatory diagram of fixing large size paper, FIG. 5 is an explanatory diagram of fixing small size paper, and FIG. 6 is a temperature distribution diagram on the circumferential surface of the heating roll. 1: Fixing device, 2: Heating roll, 3: Pressure roll, 4: Kortz lamp, 5, 6: Heat-resistant elastic body,
7: Peeling claw, 8: Temperature sensor, 9a: Substrate, 9
b: Bracket, 9c: Vertical support shaft, 9d: Bracket, 10: Solenoid, A: Maximum size paper edge, B: Center of heating roll, N: Nip section,
T ₀ : Hot offset temperature, T ₁ : Minimum fixing temperature,
a: Toner image.

Claims (1)

[Claims] 1. In a fixing device that includes a heat source provided inside a heating roll and a temperature sensor that detects the temperature of the circumferential surface of the heating roll in a non-contact manner for controlling the temperature, the temperature sensor is placed near the heating roll. Driving means that supports the temperature sensor so that the detection surface of the sensor rotates in the axial direction of the heating roll, and rotates the temperature sensor between the edge of the maximum size paper and the center of the heating roll. A fixing device characterized in that the temperature of the heating roll is controlled so that the respective detected temperatures at the edges and the center of the maximum size paper of the heating roll are within a range of allowable fixing temperatures.