JPS58160972A - Temperature controller of heat roll - Google Patents

Abstract

PURPOSE:To prevent staining of a detection part, and damage of a heat roll, and to enable always constant control of surface temp. without being affected by the external air, by using an IR sensor unit consisting of a pyroelectrical type IR sensor, a chopper mechanism, and a reference temp. measuring thermosensitive element. CONSTITUTION:A pulse motor 8 is rotated with a pulse motor drive signal of a pulse generation circuit 34, IR rays radiated from the surface of an upper heat roll are intermitted by rotation of a chopper disc 10, and projected to a pyroelectrical type IR sensor 5. Output of the sensor 5 depends on chopper frequency, and high frequency lowers sensitivity. An output signal of the sensor 5 is held at the peak value with a retention circuit 32. Output of a reference temp. measuring element 7 is amplified with an amplification circuit 55, the obtd. signal and a signal of the circuit 32 are added with a synthesizing circuit 33, its output VO is compared with a set temp. VB of a set temp. signal generating circuit 37 with a comparator 36. When VO<VB, a heater 22 is turned on, and when VO>=VB, it is turned off, thus maintaining the surface temp. of the upper heat roll at a constant prescribed value.

Description

TECHNICAL FIELD The present invention relates to a temperature control device for a heat roller for heating and fixing toner on copy paper in an electrophotographic copying machine.

In a conventional electrophotographic copying machine, in order to maintain sufficient fixing ability with a fixing device using a heat roller, it is necessary to perform control to maintain the surface temperature (fixing temperature) of the heat roller at a constant value. That is, if the fixing temperature is low, it will cause fixing failure, and if it is high, it will cause problems such as toner offset on the heat roller.

Conventionally, this type of temperature control has been carried out by directly contacting a heat-sensitive element such as a thermistor with the surface of the heat roller (contact type).
Alternatively, it has been common practice to install the heat rollers at a small distance (non-contact type), and to control the heater of the heat roller on and off based on the temperature detected by the heat-sensitive element.

However, in the control method using such a heat-sensitive element, in the contact type, the surface temperature of the heat roller can be detected instantaneously, so the ripple in the control temperature can be reduced, and at the same time, the ripple when the temperature of the heat roller rises can be reduced. Although it has the advantage of keeping overshoot small,
The detection unit is contaminated by toner, paper dust, oil, etc. that adhere to the surface of the heat roller, resulting in lower temperature detection efficiency and response, and has disadvantages such as damage to the surface of the heat roller. .

On the other hand, the non-contact type has the advantage that there is no contamination of the detection part and no damage to the surface of the heat roller, but there is a gas layer between the heat-sensitive element and the surface of the heat roller. Because of the interference, thermal response is poor, it is easily affected by outside air, and accurate temperature detection is difficult. Ripples in the control temperature are large, resulting in uneven fixing and defective fixing. It has the disadvantage of being demanding.

In other words, at present, both contact and non-contact types have their advantages and disadvantages, but a temperature detection method that combines the advantages of both and eliminates the disadvantages, specifically, is a non-contact type and is influenced by the outside air. There is a need for a temperature detection method that does not require

Purpose The present invention has been made in view of the above-mentioned requirements.The purpose of the present invention is to provide a non-contact type that is free from the effects of outside air, such as fluctuations in temperature detection level due to changes in outside air temperature and sudden air flows. An object of the present invention is to provide a temperature control device that can always control the surface temperature of a heat roller to a constant value using a dislike detection means.

SUMMARY In order to achieve the above objects, the heat roller temperature control device according to the present invention uses an infrared ray sensor, which includes a pyroelectric infrared sensor, a chopper mechanism, and a reference temperature measurement thermosensitive element, as means for detecting the surface temperature of the heat roller. It uses a sensor unit.

Embodiment Hereinafter, an embodiment of a heat roller temperature control device according to the present invention will be described with reference to the accompanying drawings.

First, the principle of the pyroelectric infrared sensor used in the present invention will be explained.

All objects at temperatures above absolute zero (OK) emit infrared (electromagnetic) energy from their surfaces in proportion to their absolute temperature. The energy per unit wavelength interval emitted from a black body at absolute temperature T' into the hemisphere at wavelength λ is expressed by Blank's law as follows.

C1c2'5T-0) "C"d, p. ”)-(1,~
■λ=□(e λ5 12 C1:3.740X10 (W-cd)C2i 1
．． 438 (cM-'deg) This energy changes depending on the wavelength, and its maximum value is expressed by Wien's law as follows.

3 λm-1 ... (2) C3: 2
890 μm, deg The total energy radiated from the black body into the hemisphere can be found by integrating equation (2) over wavelengths 0 to 4, and is expressed as the following equation.

cr: 5.67 x 10 t2W/, j de
g4 Stefan-Boltzmann constant This equation (3) is called Stefan-Boltzmann's fourth power law.

On the other hand, the pyroelectric effect is a phenomenon in which charges appear on the surface of a crystal when a part of the crystal is heated. The surface of a pyroelectric material, which has spontaneous polarization, captures stray charges in the atmosphere and maintains electrical neutralization. When a temperature change of ΔT is applied to this pyroelectric material, the magnitude of internal spontaneous polarization changes. At this time, the surface charge cannot respond quickly to temperature changes due to its spontaneous polarization.
On the surface of a pyroelectric material, charges can be observed for a short time by the amount of change in spontaneous polarization.

Pyroelectric infrared sensors detect temperature using the pyroelectric effect, and the temperature detection mechanism is the first one.
This will be explained with reference to the figures.

Figure 1 (a) shows the infrared input pulse signal % (b) shows the combination state of the dipole and floating charge inside the pyroelectric body, and (C) shows the output signal detected by installing an electrode on the pyroelectric body. ing. In a steady state, there is no change in surface charge as (bl)=(b3)*(b5), and the output signal is zero. When infrared rays are irradiated here, the temperature of the pyroelectric material rises slightly and the crystal lattice is distorted, causing disturbance in the arrangement of dipoles as shown in (b2), resulting in an imbalance with the surface-feeding charges. This reaction is very fast; an output signal appears instantaneously, and the output gradually decreases until a new equilibrium state (b3) is reached. Therefore, when infrared rays of a constant intensity are continuously incident, the output becomes zero immediately after it starts, and when the infrared rays are interrupted, a completely opposite reaction occurs and an output signal of the opposite sign is obtained. That is, the peak value of the -1 output signal corresponds to the amount of incident infrared energy.

Since the output of the pyroelectric infrared sensor becomes zero when continuous infrared rays of a constant intensity are incident, in actual use, it is necessary to attach a chopper mechanism to intermittent the incident infrared rays. Furthermore, since the output at this time is the relative temperature between the chopper temperature and the object to be measured, in order to obtain the absolute temperature, it is necessary to measure the chopper temperature and correct the output of the infrared sensor.

Here, the configuration of the infrared sensor unit used in the present invention will be explained with reference to FIGS. 2 and 3.

This infrared sensor unit (1) has a pyroelectric infrared sensor (5
) and (reference temperature measuring element for chopper temperature measurement (7)
)).

A chopper disk (1o) is attached to the rotating shaft (9) of a pulse motor (8) in order to intermittent the incident infrared rays.The chopper disk (10) has a semicircular opening (1o).
1) is formed. Since the pyroelectric infrared sensor (5) is susceptible to noise (fluctuations in the incident infrared rays, noise from the pulse motor (8), etc.), the entire unit is covered with a metal case (12 pieces). ) D is connected to the ground terminal of the sensor (5).In addition, the input of the step motor (8), the input/output of the sensor (5), and the input/output of the reference temperature measuring element (7) are connected to the printed circuit board (
3) is connected to the outside through a terminal (4) fixed to the terminal (4). In the above configuration, infrared rays enter from the entrance hole (13) of the case (12), and the infrared rays enter the opening (13) of the chopper disk (10).
11) and enters the light receiving section (6) of the sensor (5). - Specifically, the infrared sensor unit (1) having the above configuration is attached to the fuser outer cover (15) as shown in Figure $4.
) is provided with an infrared entrance hole (16), and a heat insulating material (
17). Note that this fixing device consists of an upper heat roller (20) and a lower heat roller (21).
The upper heat roller (2o) has a built-in heater (22) and can be driven to rotate in the direction of arrow (a). Lower heat roller (
21) is in pressure contact with the upper heat roller (20), and the arrow ('b)
) direction.

In this way, attach the infrared sensor unit (1) to the outer cover (
15) is attached to the outside of the infrared sensor unit (
This is to satisfy the conditions of 1), such as restrictions on the environmental temperature and restrictions on temporal changes in the temperature of the pyroelectric infrared sensor (5) itself.

Further, the reason for interposing the heat insulating material (17) is to prevent the temperature of the infrared x sensor unit (1) from rising above the limit temperature due to the influence of the upper heat roller (20).

On the other hand, in order to prevent the temperature of the infrared sensor unit (1) from rising, it may be attached to the outer cover (15) via a spacer (18) as shown in Figure 5, or it may be attached to the outer cover (15) as shown in Figure 6. A retaining bracket (19) may be provided separately from the outer cover (15) and attached to this.

Next, a temperature control circuit using the infrared sensor unit (1) will be explained with reference to FIG.

(30) is an amplifier circuit that amplifies the output of the pyroelectric infrared sensor (5). (31) is a filter circuit, and an amplifier circuit (
Separate and select the outputs of 30). (32) is a peak value holding circuit, (33) is a synthesis circuit, and peak value holding circuit (32) is a combining circuit.
) is inputted with a reset signal from the pulse generating circuit (34). - On the other hand, another output of this pulse generating circuit (34) is inputted to the pulse motor (8) of the chopper mechanism as a pulse motor drive signal. Further, the output of the reference temperature measuring element (7) is sent to the synthesis circuit (33) together with the output of the peak value holding circuit (32) to the amplifier circuit (33).
5).

Reference numeral (36) is a comparison circuit to which the output of the synthesis circuit (33) and the output of the set temperature signal generation circuit (37) are input, and the two are compared. A set temperature signal generation circuit (37) generates a resistance partial pressure signal for controlling the surface temperature of the upper heat roller (2o) to a predetermined set temperature, specifically, 165°C. (38) is a phase control circuit which receives the comparison signal from the comparison circuit (36) and receives the output (V) of the synthesis circuit (33).
When Q) is smaller than the set temperature partial pressure, the heater (22)
is turned on and turned off when it is equal or greater.

In the above control circuit, first, the pulse generation circuit (34
), the pulse motor 3 (8) rotates at a period of (2t1), emits radiation from the surface of the upper heat roller (20), and detects the pyroelectric infrared sensor (5). The infrared rays incident on the chopper disk (10)
Intermittent by the rotation of. Accordingly, the pyroelectric infrared sensor (5) responds, and its output is amplified by the amplifier circuit (30) and passed through the filter circuit (31), resulting in the waveform shown in FIG. 8(b).

The output of the pyroelectric infrared sensor (5) depends on the chopper frequency (the number of revolutions of the chopper disk (10)), and as shown in Figure 9, the sensitivity decreases as the chopper frequency (Hz) increases. . In this example, the chopper frequency (H
2) is 1 to 3 (H), but is not limited to this. Also, the rise of the output of the pyroelectric infrared sensor (5) with respect to the rise of the pulse motor drive signal is % ([d)
(see FIG. 8(b)), but this is due to a mechanical delay in the rotation of the chopper disk (10).

Furthermore, the output signal (So) of the pyroelectric infrared sensor (5)
is set to (S□) by the peak value holding circuit (32), as shown in FIG. 8(C), and the pulse generating circuit (34)
) is reset immediately before the next output signal (S2) rises. Similarly, the output signal (S 2
> - (S3) is reset to (S2) and (S3), and the peak value is held in the same way 1. Also, the reset signal input to the peak value holding circuit (32) is the pulse motor drive signal The signal is emitted from the pulse generating circuit (34) with a delay of time (td) by the integrating circuit (see FIG. 8(d)).

Next, the output of the reference temperature measuring element (7) is transferred to the amplifier circuit (35).
) (see FIG. 8(e)) and the signal from the peak value holding circuit (32) (see FIG. 8(C)).
) and are added in the synthesis circuit (33), the surface temperature of the object to be measured (-) roller (20) becomes as shown in Figure 8 (
It is detected with the waveform shown in f). The output here (V o
, V o = V s + V o ) and the set temperature partial pressure (VB) of the set temperature signal generation circuit (37) are compared in the comparison circuit (36), and if o<VB, the heater (22) is turned on. If Vo≧VB, it turns off. As a result, the surface temperature of the upper heat roller (20) is maintained at a set temperature, specifically, a constant value of 165°C.

Note that the reference temperature measuring element (7) is used in the synthesis circuit (33).
) and the output of the pyroelectric infrared sensor (5), it is necessary to equalize the output level of both with respect to temperature change. For this purpose, the output level of both should be set at a certain level, for example 1, under the same conditions as the usage environment.
The output at 00°C is 1. The amplifier circuits (30) and (35) (D gain are adjusted and used so as to be OOV).

Furthermore, in general, if the output of an infrared sensor does not have linearity, it is necessary to linearize it. However,
The output of the pyroelectric infrared sensor used in the present invention is proportional to the fourth power of the absolute temperature T, and in the temperature control range of this type of heat roller, the output is approximately linear.

Furthermore, although the temperature characteristics of the diode were used as the reference temperature measuring element (7) in the above embodiments, the present invention is not limited to this.

Effects As is clear from the above explanation, the present invention uses an infrared sensor unit consisting of a pyroelectric infrared sensor, a chopper mechanism, and a reference temperature measurement heat-sensitive element as means for detecting the surface temperature of the heat roller. The advantage of the contact type is that there is no contamination of the detection section and no damage to the surface of the heat roller, and the disadvantage of the contact type is that it eliminates the adverse effects of outside air and can always control the surface temperature of the heat roller to a constant value.

[Brief explanation of drawings]

The drawings are for explaining the temperature control device according to the present invention, and FIG. 1 is an explanatory diagram of the temperature detection mechanism using a pyroelectric infrared sensor, and FIGS. 2 and 3 show the inside of the infrared sensor unit. A front view and a side view, FIG. 4 is an explanatory diagram of the installation state of the infrared sensor unit, FIGS. 5 and 6 are simple explanatory diagrams, FIG. 7 is a 10-step diagram of the temperature control circuit, and FIG.
The figure is a signal waveform diagram, and FIG. 9 is a graph showing chopper frequency characteristics of a pyroelectric infrared sensor. (1)...Infrared sensor unit, (5)...Pyroelectric infrared disk, (20)...Upper heat roller,
(21)...lower heat roller, (22)...heater 1. (32)...Peak value holding circuit, (
33)...Composition circuit, (34)...Pulse generation circuit, (36)...Comparison circuit, (37)...
- Set temperature signal generation circuit, (38)...phase control circuit. Patent applicant Minolta Camera Co., Ltd. Agent
Two patent attorneys, Aoyama Aoyama (Fig. 1, Fig. 9, 4mdYR Sutoshi CHw)
---- Procedural Amendment (Mutsu) May 6, 1980 1. Indication of the case 1988 Patent Application No. 43958 2. Name of the invention Heat roller temperature control device 3. Person making the amendment Relationship with the case Patent applicant address: 2-3 Azuchi-cho, Higashi-ku, Osaka (Street address: Osaka + 171 Building 4) Agent address: Honmachi 2-Kawa Honmachi Building, Higashi-ku, Osaka, Osaka Prefecture Date of amendment order (voluntary amendment)

Claims (1)

[Claims] 1. An infrared sensor unit installed near the heat roller and consisting of a pyroelectric infrared sensor, a chopper mechanism, and a heat-sensitive element for measuring a reference temperature, a set temperature signal generating means for the heat roller, and a temperature signal detected by the sensor unit. It is characterized by comprising a comparison means for comparing the temperature detection value of the heat roller and a set temperature signal from the generation means, and a control means for controlling on/off the heater of the heat roller based on the operation of the comparison means. Temperature control device for beat rollers.