JPH0582586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device that does not require a surface temperature detection element of a fixing roller.

FIG. 1 shows a conventional fixing device. Fixing roller 1
A hollow tube 1a made of a material with good thermal conductivity such as aluminum or copper is thinly coated with a releasable material 1b such as silicone rubber or tetrafluoroethylene resin. The pressure roller 2 has a core metal 2a covered with a relatively thick silicone rubber layer 2b. The surface temperature of the fixing roller 1 is controlled to a temperature that allows fixing. The copy paper P holding the toner image T is conveyed in the direction of the arrow and heated and pressed between rollers 1 and 2.

The fixing roller 1 is heated by a heater 3 such as an infrared lamp that is a heat source disposed inside the fixing roller 1, and a sufficient amount of heat and pressure is applied to melt the toner image T at the contact portion with the pressure roller 2. Further, the surface temperature of the fixing roller 1 is always controlled within a certain temperature range by a temperature detection element 4 such as a thermocouple or a thermistor. Reference numeral 5 denotes an entrance guide for transporting and guiding the copy paper P to the fixing section, and in order to send out the copy paper P that has undergone the fixing process, the copy paper P that comes out of the nip while remaining in close contact with the fixing roller 1 is passed through the fixing roller. Separating means 6 for peeling off from fixing roller 1 is arranged so that its tip is in contact with fixing roller 1. The fixing roller 1 is cleaned by a cleaning means 7 that applies an anti-offset liquid such as dimethyl silicone oil, methyl phenyl silicone oil, or fluorosilicone oil to prevent toner from adhering, and the fixing roller 1 is used repeatedly.

The recent development of medium to high speed copying machines has focused on energy saving and low power consumption.
As a result, when copy paper is passed continuously, the surface temperature of the fixing roller 1 cannot maintain the set temperature during standby even if the heater 3 built into the fixing roller is turned on continuously, and the curve shown in Figure 2 As shown in C, the surface temperature of the fixing roller 1 gradually decreases, and even if it is within a practical range from the viewpoint of fixing, the amount of cold offset toner increases. When used in this manner, toner accumulated between the fixing roller 1 and the temperature detection element 4 provided to control the surface temperature may reduce the accuracy of detected temperature, reduce temperature responsiveness, and even cause temperature fluctuations. Damage to the detection element 4 and damage to the fixing roller 1 may occur. If the temperature detection element is damaged, the surface temperature of the fixing roller 1 cannot be controlled, causing the surface of the fixing roller 1 to be abnormally heated, causing damage, and even causing a fire.
Further, if the fixing roller 1 is damaged, the copy paper P corresponding to the damaged part will suffer from poor fixing, and the copy paper P will be more likely to wrinkle.

The present invention provides a heat fixing device for an electronic copying machine.
This eliminates the drawbacks caused by the temperature detection element that comes into contact with the fixing roller and detects the surface temperature, and even if offset toner adheres to the fixing roller surface, the fixing roller surface temperature is well controlled and the fixing roller has excellent durability. The purpose is to provide equipment.

The present invention includes a heater that generates heat when energized and a heating member that is heated by the heater, and detects the environmental temperature in a heating fixing device that heats and fixes a toner image on a recording material using the heat from the heating member. The energization control means has H(τ)=aτ· exp (bτ) (H: lighting time of heater to return to standby temperature after continuous fixing, τ: continuous fixing time, a, b: constants depending on environmental temperature) τ=T[1-{A(t)} ^x ]/B(t) (τ': Lighting time of heater to return to standby temperature after power off during standby, T: Standby temperature, A(t): Constant depending on environmental temperature, x: After power off during standby The heating member is maintained at a constant temperature during fixing without detecting the temperature of the heating member by controlling the energization based on the elapsed time (B(t): rate of rise in temperature of the heating member at startup). This is a heat fixing device.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing the state of surface temperature control of the fixing roller 1 of the present invention.

When the main switch of the copying machine is turned on, the surface temperature of the fixing roller 1 rises according to a curve A, and when it reaches the set temperature T, heating of the heater 3 is stopped.

During standby, the surface temperature of the fixing roller 1 is maintained at T as shown by curve B.

When a copy signal is input, the heater 3 is turned on continuously, but the surface temperature of the fixing roller 1 decreases according to a curve C after copying is completed. Heat it and curve it
According to C', the temperature is heated to the set temperature T and returned to normal.

When the copying machine in the standby state is turned off, the temperature decreases according to curve D, but when the power is turned on, the temperature returns to the set temperature T according to curve D'.

The four cases described above are assumed, and temperature control in these cases is performed as follows.

Curve A: After the main switch of the copying machine is turned on, the timer turns on the heater 3 for the required time.

Curve B, that is, in the case of standby, where W is the power required to maintain the surface of the fixing roller 1 at the set temperature T, the rated power W _H of the heat source, and the ratio γ of the lighting time of the heater 3 to the duration of standby, W = W _H ×
The heater 3 is turned on so as to satisfy the relationship γ, in other words, the timer is used to turn on and off the heater 3 at a rate of γ. γ is a constant that depends on the environmental temperature.

The surface temperature of the fixing roller 1 drops during continuous copying for a period of .tau. according to the curve C, and then returns to the set temperature T according to the curve C'. The lighting time H of the heater 3 necessary for this double regression has a relationship with the continuous copy time τ as shown in Figure 3, and if this is expressed as a function (the ) H(τ) = aτ・exp(bτ). Also, the relationship between the heater lighting time H and the continuous copy time τ is a=H/τ and the continuous copy time τ
The relationship with is shown in Figure 4.

By detecting this continuous copying time τ, the heater 3 is turned on continuously for H hours after the scheduled copying is completed.

a and b are constants that depend on the environmental temperature obtained by an environmental temperature detection means (not shown).

When the copier is turned off during standby, curve D
In this case, when the surface temperature of the fixing roller 1, which has fallen due to natural cooling, is restored according to the curve D' as shown in Fig. 5, the temperature drop y when x seconds have elapsed from the standby temperature (set temperature T) is y. =T[1-{A(t)} ^x ] seconds. Here, T is the standby temperature (set temperature), and A(t) is a constant depending on the environmental temperature. The time τ' during which the heater 3 must be turned on in order to return to the standby temperature after the temperature drops to y℃ is τ' = T[1-{A(t)} ^x ]/B(t) seconds. .
B
(t) is the rate of increase in the surface temperature of the fixing roller at the time of startup, and is a constant that depends on the environment.

For example, in the case of controlling curves C and C' in the above case, at an environmental temperature of 10°C to 20°C, γ = 0.12, a = 1.156, b = -0.015, and at an environmental temperature of 20°C or higher, γ = 0.10, a = 1.012, b = Good temperature control can be achieved by setting it to −0.021. For example, highly accurate temperature control is possible at an environmental temperature of 10°C to 35°C.

Since good temperature control can be achieved even in the case where the environmental temperature is divided into two, better temperature control can be achieved by further dividing the environmental temperature.

For example, the environmental temperature is continuously detected by a temperature detection device such as a thermocouple, and the values of H(τ), A(t), B(t), and timer set corresponding to the detected environmental temperature are determined and controlled. You can also do it.

As explained above, the heating roller fixing device is a high-performance, high-quality fixing device that does not require a contact type temperature detection element to the fixing roller.
Furthermore, we were able to provide a copying machine with excellent durability and reliability.

[Brief explanation of drawings]

Figure 1 is a side view showing a conventional example, Figure 2 is a diagram showing the status of fixing roller surface temperature control, Figure 3 is a diagram showing the relationship between heater lighting time and continuous copying time, and Figure 4 is a diagram showing continuous copying. A diagram showing the relationship between heater lighting time and continuous copying time with respect to copying time, and FIG. 5 is a diagram showing natural cooling of the fixing roller surface temperature. 1... Fixing roller, 3... Heater, 4... Temperature detection element.

Claims (1)

[Scope of Claims] 1. A heat fixing device that includes a heater that generates heat when energized and a heating member that is heated by the heater, and heats and fixes a toner image on a recording material using the heat from the heating member, It has an environmental temperature detection means that detects the environmental temperature, and an energization control means that controls the lighting time of the heater based on the detection output of the environmental temperature detection means and the state of the device, and this energization control means has H( τ) = aτ・exp(bτ) (H: lighting time of heater to return to standby temperature after continuous fixing, τ: continuous fixing time, a, b: constants depending on environmental temperature) τ′=T[1-{ A(t ⁾ } By controlling the energization based on the elapsed time after the power is turned off during standby (B(t): rate of rise in temperature of the heating member at startup), the heating member can be kept at a constant temperature during fixing without detecting the temperature of the heating member. A heating fixing device characterized by maintaining