JPS5952271A - Temperature controller for heat roller - Google Patents

Abstract

PURPOSE:To stabilize surface temperature, by using a unit of a pyroelectric infrared sensor, chopper, and heat-sensitive element for reference temperature measurement, and attaching a filter in the entrance hole of a unit case. CONSTITUTION:Only infrared rays are transmitted from the case entrance hole 13 through a filter 14 and caused to enter the photodetection part 6 of the sensor 5. The output of the sensor 5 is separated and selected by a filter 31. A reset signal is inputted from a pulse generating circuit 34 to a peak holding circuit 32. The other output of the pulse generating circuit 34 is inputted to a pulse motor 8. The output of a composing circuit 33 is compared with that of a set temperature signal generating circuit 37 by a comparing circuit 36 and a phase control circuit 38 receives its comparison signal to turns on a heater 22 when the output of the composing circuit 33 is less than set temperature partial pressure or turn off it when equal or greater. Thus, the evil influence of the outside air is eliminated and the surface temperature of the heat roller is controlled to an invariably constant 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 very small distance (non-contact type) and 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 heat roller surface, but there is a gas layer between the heat sensitive element and the heat roller surface. 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 there is a temperature detection method that combines the advantages of both and eliminates the disadvantages. Specifically, it is a non-contact type that is not affected by the outside air. Therefore, there is a need for a temperature detection method that does not exist before.

Therefore, it is conceivable to use an infrared sensor unit as a means for detecting the surface temperature of the heat roller, which has the advantage that the detection element is of a non-contact type and the temperature detection level does not fluctuate due to the influence of outside air. However, even with this, the rapid heat flow prevents normal temperature detection, and if the light-receiving part of the infrared sensor becomes contaminated with toner scattering or fixing oil vapor, the sensitivity decreases and normal temperature detection becomes impossible. This is possible, and measures need to be taken in this regard.

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. Provided is a temperature control device that can control the surface temperature of a heat roller to a constant value at all times by using a detection means that does not require a detection means, prevents interference with normal temperature detection due to sudden heat flow, and prevents foreign matter from adhering to the light receiving part of the sensor. It's about doing.

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. This uses a sensor unit and an infrared transmission filter is attached to the infrared incidence hole formed in the case of the 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.

FIGS. 1 and 2 show the configuration of an infrared sensor unit used in the present invention. This infrared sensor unit detects temperature by utilizing the conventionally known pyroelectric effect, a phenomenon in which electric charges appear on the crystal surface when a part of the crystal is heated. In response to the incidence of infrared rays, the output rises and then immediately goes to zero, and when the infrared rays are blocked, a completely opposite reaction occurs and an output signal of the opposite sign is obtained. That is, the peak value of such an output signal corresponds to the amount of incident infrared energy.

Incidentally, since the output of the pyroelectric infrared sensor becomes zero when infrared rays of a constant intensity are continuously 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.

Specifically, the infrared sensor unit (1) includes an intermediate plate (
A pyroelectric infrared sensor (5) and a reference temperature measuring element (7) for chopper temperature measurement are installed on the printed circuit board (3) fixed to 2), and a pulse motor (8) is installed to intermittent the incident infrared radiation. The chopper disk (1■) is attached to the rotating shaft (9), and the chopper disk (1■) has a semicircular opening (
11) is formed. Since the pyroelectric infrared sensor (5) is susceptible to noise (fluctuations in incident infrared rays, noise from the pulse motor (8), etc.), the entire unit is covered with a metal case 02, and this case (121) 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).

Furthermore, the infrared entrance hole (13) formed in the case (12)
) An infrared transmission filter (141) is installed inside the infrared transmission filter (141).

This filter (141) transmits only the infrared rays necessary for the sensor (5) to detect the temperature, while blocking other heat waves, so that a rapid heat flow from the entrance hole (13) to the case (1 This prevents abnormalities in the reference temperature measured by the measuring element (7) and erroneous detection of the surface temperature of the upper heat roller (4) as described below.Moreover, the filter (The insert also has the function of blocking toner scattering and fixing oil vapor from entering the case (12) from the entrance hole +131, which may contaminate the light receiving part (6) of the sensor (5).) It also prevents

In addition, in order to obtain the same effect as the filter (141), the entrance aperture (1) should be made as small as possible (the diopter should be narrowed down).
Another possible measure is to move the unit (1) away from the vicinity of the fixing device, but this is functionally effective.

In the above configuration, infrared rays enter the incident hole (131) of the case (12) via the filter (141), pass through the chopping disk (10) (7), and the opening (11), and then enter the light receiving part ( 6) is incident on (7).

Specifically, as shown in FIG.
51 is provided with an infrared incident hole (16), and attached to the outside through a heat insulating material (1η).This fixing device consists of an upper heat roller (■) and a lower heat roller (21), and the upper heat roller (■) is a heater. It has a built-in force and can be rotated in the direction of arrow (a).The lower heat roller (2υ) is in pressure contact with the upper heat roller (2), and can be driven to rotate in the direction of arrow (b).

In this way, cover the infrared sensor unit (1) with the outer cover.
Installed on the outside of +151 are the environmental temperature limit of the infrared sensor unit (1) and the pyroelectric infrared sensor (5).
This is to satisfy conditions such as restrictions on temporal changes in its own temperature. Further, the reason why the heat insulating material (17) is provided is to prevent the temperature of the infrared sensor unit (1) from rising above the limit temperature due to the influence of the upper heat roller (2).

On the other hand, in order to prevent the temperature of the infrared sensor unit (1) from rising, as shown in FIG.
) through the outer cover (may be attached to 1ω, or 5th
As shown in the figure, an outer cover (a holding bracket f19 separate from 19) may be provided and attached to this.

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

(to) is an amplifier circuit that amplifies the output of the pyroelectric infrared sensor (5). (31) is a filter circuit, and an amplifier circuit ((
Separately select the output of The country is a peak value holding circuit, and the country is a combining circuit, and the reset signal from the pulse generation circuit (34) is input to the peak value holding circuit (321).On the other hand, another output of this pulse generation circuit (goods) is A chopper mechanism pulse motor (
8). Further, the output of the reference temperature measuring element (7) is input to the synthesis circuit (to) together with the output of the peak value holding circuit (with) via an amplifier circuit (to).

(to) is a comparison circuit to which the output of the synthesis circuit @ and the output of the set temperature signal generation circuit are input, and the two are compared.

The set temperature signal generation circuit (to) generates a resistive voltage division signal for controlling the surface temperature of the upper heat roller (2) to a predetermined set temperature, specifically, 165°C. (support) is a phase control circuit which receives a comparison signal from a comparison circuit (incorporated) and turns on the heater ■ when the output (vo) of the composite circuit is smaller than the set temperature partial pressure, and when it is equal to or greater than the set temperature partial pressure. to turn off.

In the above control circuit, first, the pulse motor (8) rotates at a period (2t 1) according to the pulse motor drive signal of the pulse generating circuit (Ren's pulse motor drive signal (see Fig. 7 (a)), and pyroelectric infrared sensor (5
) is interrupted by the rotation of the chopper disk (10). Along with this, a pyroelectric infrared sensor (5)
responds, and its output is amplified by the amplifier circuit (a) and passed through the filter circuit C1υ, resulting in the waveform shown in FIG. 8(b).

Note that the output of the pyroelectric infrared sensor (5) depends on the chopper frequency (chopper disk (rotation speed of 1ω)), and as the chopper frequency (Hz) increases, the sensitivity decreases.In this embodiment, the chopper frequency (Hz) ) is 1 to 3 (H2), but is not limited to this.

In addition, the rise of the output of the focus-shaped infrared sensor (5) is delayed by (d) with respect to the rise of the pulse motor drive signal (see Fig. 7 (bl)), but this is caused by the chopper disk (l
Due to the mechanical delay in the rotation of O).

Furthermore, the output signal (S□) of the pyroelectric infrared sensor (5)
is set to (S□) by the peak value holding circuit t321, as shown in FIG. Similarly, the output signal (S2).

(S) is reset to (52') and (SA), and the peak value is maintained at intervals thereafter. In addition, the reset signal input to the peak value holding circuit (32) is generated by delaying the pulse motor drive signal by the time ((d)) using the integrating circuit and issuing it from the pulse generating circuit G4 (see FIG. 7(d).
)reference).

Next, the output of the reference temperature measuring element (7) is converted into an amplified signal (see FIG. 7(e)) via the amplifier circuit (see FIG. 7(e)) and a signal from the peak value holding circuit (321) (see FIG. 7(e)). When the surface temperature of the upper heat roller (a), which is the object to be measured, is added with the waveform shown in FIG. 7(f), the output (■ o, ■o−■s ten vD) and the set temperature partial pressure of the set temperature signal generation circuit (9) (
VB) is compared with the comparison circuit (36), and if o<VB, the heater is turned on, and if Vo≧VB, it is turned off.

As a result, the surface temperature of the upper heat roller (2o) is maintained at the set temperature, specifically, at a constant value of 165°C.

Note that when the output of the reference temperature measuring element (7) and the output of the pyroelectric infrared sensor (5) are combined in the above-mentioned combining circuit (combining circuit), the output levels of both must be equalized with respect to temperature changes. For this purpose, the output level of both should be set at a certain level in advance under the same conditions as the usage environment, for example, 100℃.
The output at 1. Amplifier circuit +30 to make it OOV)
, (Adjust the gain of 351 and use.

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

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.

Furthermore, since an infrared transmission filter is attached to the infrared incidence hole formed in the case of the sensor unit, it is possible to eliminate the sudden flow of heat into the case and the attachment of foreign matter to the light receiving part of the sensor, thereby maintaining the characteristics of the sensor more accurately. It is possible to do so.

[Brief explanation of the drawing]

The drawings are for explaining the temperature control device according to the present invention, and FIGS. 1 and 2 are front and side views showing the inside of the infrared sensor unit, and FIG. 3 is a diagram showing the installed state of the infrared sensor unit. 4 and 5 are explanatory diagrams of modifications thereof, FIG. 6 is a block diagram of the temperature control circuit, and FIG. 7 is a signal waveform diagram. (1)...Infrared sensor unit), (51...
Pyroelectric infrared sensor, (6)... Light receiving part, (7)...
・Reference temperature measuring element, (8)...Pulse motor, fl
α...Chopper disk, (12...Case, (131
...Incidence hole, (14)...Filter, (■...
Upper heat roller, (21)...Lower heat roller,■・
...Heater, Cl21...Peak value holding circuit, country...
・Synthesis circuit, (foundation)...Pulse generation circuit, (3j5・
... Comparison circuit, (to) ... Set temperature signal generation circuit, (
Support)...Phase control circuit. Patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Hao Aoyama and 2 others

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 reference temperature, and an infrared transmission filter attached to an infrared entrance hole formed in the case of this sensor unit. , a heat roller set temperature signal generation means, a comparison means for comparing a temperature detection value of the heat roller detected by the sensor unit and a set temperature signal from the generation means, and based on the operation of the comparison means. 1. A temperature control device for a heat roller, comprising: control means for controlling on/off a heater of the heat roller.