JPH0478870A - Copying machine - Google Patents

Abstract

PURPOSE:To perform the overheat preventing control of a platen glass without providing a temperature sensor on the platen glass and without making a processing speed excessively low by properly delaying the time of starting to decrease the number of copied sheets in accordance with the voltage value of a light emitting lamp for reading an original. CONSTITUTION:This copying machine is constituted so that the number of copied sheets per unit time may be decreased every time the number of consecutively copied sheets exceeds a previously set threshold. Then, an optical image plotted on a photosensitive body K is converted into an electrostatic latent image by a latent image forming part 5 and converted into a toner image by a developing part 6. Furthermore, the toner image is thermally fixed by a fixing part 7 and a paper is ejected to the outside of a machine. While the above processing is performed, a temperature detection part 13 measures the temperature at the proper spot of the fixing part 7, and an off-time after stopping the operation is calculated from the measured temperature by an off- time calculation part 12. Whether electrostatic charging processing is performed to the photosensitive body K is decided by a processing part 14 by setting the off-time as reference. Then, a platen glass temperature calculation part 15 calculates the temperature of the platen glass.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in electronic copying machines.

[Conventional technology]

In general, this type of copying machine irradiates a document placed on a platen glass with light from a light-emitting lamp for document reading, and transmits the reflected light through a drawing section to a photoconductor drum (OPC (organic photoconductor)). or a drum with a selenium-based photoconductive material on its surface) or a photoreceptor belt as an electrostatic latent image.
Furthermore, the electrostatic latent image is converted into a toner image in a developing section, transferred onto recording paper, and then thermally fixed in a fixing section.

In conventional copying machines, if the temperature of the platen glass rises above a predetermined temperature due to the heat of the original reading lamp, there is a risk of physical or psychological harm to the user. In particular, this point is strictly regulated by UL standards for equipment destined for the United States. For this reason,
In the conventional apparatus, (1) the temperature of the platen glass is actually measured with a temperature sensor, and when the temperature exceeds a predetermined value, the CPM value (number of copies per unit time) is decreased.

(2) The CPM value is reduced to a predetermined CPM value according to the copy magnification.

It was structured like this.

[Problem to be solved by the invention]

However, in the conventional image forming apparatus described above, those using the temperature sensor described in (1) result in increased man-hours and costs associated with sensor installation, and a complicated apparatus configuration.

If the CPM value is determined by the multiplication factor (2), the processing speed may be lowered more than necessary, and the device may not be able to demonstrate its original performance.

It had some problems.

In view of the above points, it is an object of the present invention to provide a copying machine that can prevent overheating of the platen glass while maximizing the original performance of the device without using a special temperature sensor.

[Means to solve the problem]

To achieve the above object, the present invention provides a copying machine configured to reduce the number of copies per unit time each time the number of consecutive copies exceeds a preset threshold. A means is provided for appropriately delaying the start time of reduction of the original reading light emitting lamp according to the voltage value of the original reading light emitting lamp, thereby making it possible to precisely control the copying processing speed.

(Principle of off-time measurement) Prior to explaining the embodiments, the theoretical basis of the time measurement method based on heat radiation aging characteristics used in the device of the present invention will be explained.

First, the heat dissipation characteristics of the surface temperature of the fixing roller over time assume that the temperature inside the machine is constant regardless of the outside temperature, temperature over time - 1, fuser temperature + 190°C1 proportionality constant - K, temperature inside the machine =
Assuming that the time constant is -η at 25°C, the off time is τ, and the undetermined constant is C, it can be approximately expressed as T(r)-Kexp(-r/77)+C-(1).

Here, T (0) = +c +190°C T ((X)) = C = 25°C, so 1, -, = T (0) -T ((1)) +190-2
5 +165. That is, T (r) = 165e xp (-r/ η)
+25-(1)'. Next, τ/η-1, that is, in the heat dissipation characteristics shown in Figure 4, exp (
-τ/η)=0.368 When T(τ)=86("c), τ=l○(minutes), so the time constant η may be set as η=IO.

Here, if the influence of the outside temperature is considered, the above formula (])' becomes T = 165e x p (-r/ 10) +2
5+ a -----(2). However, α is a correction value indicating the influence of the air flow around the heating part and the temperature difference between the main body of the device and the outside air, and for example, cx= (T, -25) (1-exp (-r/20
)) T, I: Can be approximated to room temperature.

Therefore, T,=10, which is assumed to be the normal temperature range,
When T (10) and T (20) are calculated for each room temperature of 20 and 30°C, each time estimation error ΔT is as follows: ΔT(10)≦±1 minute ΔT(20)≦±2 minutes. Therefore, it can be seen that the error when estimating the off time from the temperature of the heating section is sufficiently small, about ±10% at most, and that time can be measured with an accuracy that poses no problem in practical use.

Furthermore, it is also possible to estimate in advance the influence of this type of time measurement error on process control, and to realize control with a margin within which the influence of the error does not extend.

〔Example〕

Hereinafter, the present invention will be described based on an embodiment shown in the accompanying drawings.

Fig. 1 is a principle configuration diagram of the present device, Fig. 2 is a block diagram, Fig. 3 is a flowchart showing the main operations, and Fig. 4 is a flowchart showing the main operations.
The figure is a characteristic diagram showing the relationship between platen glass temperature and CVR value, Figure 5 is an experimental example showing the change in platen glass temperature due to CPM down, Figure 6 is platen glass temperature and magnification,
This is a characteristic episode that shows the relationship between paper sizes.

In the figure, 1 is a platen glass, and the platen glass 1 is provided on the upper surface of the main body 100 of the apparatus of the present invention. The platen glass 1 is used to place a copy original, and is configured so that it can be optically scanned by a light emitting lamp of the original reading section 2 and can output image information consisting of light reflected from the original to the drawing section 3.

Reference numeral 4 denotes an image generation section, and the image generation section 4 can extract images, characters, graphic patterns, etc. from a predetermined storage device or signal transmission device (not shown) and output them to the drawing section 3. ing. This image generating section 4 is used to create images that do not involve copying, or to add different types of images, characters, or patterns to a copied image. Here, when the device main body 100 of the present application is configured as a copy-only machine,
The image generating section 4 may be omitted.

Reference numeral 5 denotes a latent image forming section, and the latent image forming section 5 includes a photoreceptor K (drum or belt) and is configured to convert an image drawn with the light beam from the drawing section 4 into an electrostatic latent image. has been done. However, if the off time (duration of the power off of the main body) exceeds a predetermined length, the photoconductor may be
Charging processing is performed at , so that sufficient residual charge can be retained.

Reference numeral 6 denotes a developing section, and the developing section 6 is configured to attach toner to the electrostatic latent image formed on the photoreceptor by the latent image forming section 5 and convert it into a toner image. The recording paper is then conveyed to the fixing section 7, where the toner image is thermally fixed, and then the recording paper is discharged outside the machine.

8 is a CPM setting section, and the CPM setting section 8 is used to appropriately set the processing speed (the number of recording sheets processed per minute) according to the conditions of recording sheet production as described below. be. That is, the CPM value can be appropriately set according to the following: (1) Creation magnification (2) Number of sheets to be continuously processed (2) CVR value (voltage of the light emitting lamp of the document reading section 2) (2) Temperature of the platen glass, etc.

Here, the creation magnification of ■ is the information in the magnification input section 9, and the number of continuous processing sheets of ■ is the information of the number input section 10, respectively.
The setting section 8 is manually operated. The CPM setting unit 8 has a plurality of CPM values set, and is configured so that the optimum value can be selected from among them even during processing, depending on the magnification and the number of continuous processing sheets.

Figure 6 shows how the platen glass temperature changes depending on the magnification and the number of sheets processed continuously at rA4・200% and B.
4.200%", and by switching the CPM value during processing, the CPM value can be changed to 4.
It can be seen that the temperature can be controlled so as to be saturated at an increased temperature of 5°C or less.

■The 0CVR value is determined by the CV
The voltage set by the R adjustment section 11 is input. This CVR value is approximately proportional to the amount of heat generated by the light emitting lamp of the document reading section 2, and is an important factor governing the temperature rise of the platen glass. That is, for example, it is possible to prevent the platen glass from overheating by reducing the CPM value determined according to the paper size and magnification when the number of continuously processed sheets exceeds a predetermined threshold. In this case, if the amount of heat generated by the light emitting lamp is evaluated more precisely with reference to the CVR value, the timing of CPM down can be delayed. The conflicting demands of preventing heating of the platen glass and exhibiting the processing performance of the apparatus of the present application can be realized in the most harmonious manner.

Since it is not desirable to detect the platen glass temperature by installing a temperature sensor near the platen glass l in terms of complicating the configuration and increasing costs, in this embodiment, the platen glass temperature calculating section 14 detects the temperature by installing a temperature sensor near the platen glass l. The platen glass temperature is calculated based on the off time calculated by the off time calculation unit 12 and the predetermined heat dissipation characteristic of the platen glass. This platen glass temperature can be used to control CPM down with reference to various parameters such as the paper size, magnification, and CVR value.

Reference numeral 12 denotes an off-time calculating section, and the off-time calculating section 12 calculates the output of a temperature detecting section 13 provided at a suitable position of the temperature rising part in the fixing section 7 (in this embodiment, on or near the surface of the heat fixing roller). The apparatus is configured to be able to calculate the elapsed time after the operation is stopped based on the information and the predetermined heat radiation aging characteristic of the temperature increasing section. That is, the off-time calculating section 12 stores the heat radiation characteristics of the temperature increasing section over time in a map format in a memory.
The off time can be estimated by reversely looking up the map from the output information of the temperature detection section 13. and,
Based on the off time calculated by the calculation unit 12, the preprocessing unit 1
4, it is determined whether or not to perform the charging process, and the platen glass temperature calculation section 15 also estimates the platen glass temperature. The theoretical consideration regarding time measurement based on heat radiation characteristics over time is as described above.

In the above embodiment, in the copy mode, a document is placed on the platen glass 1, the document reading section 2 reads the document, and image information is transmitted to the drawing section 4. On the other hand, CPM
The setting section 8 includes a magnification detection section 9, a number detection section 10, and a CVR.
The CPM value is appropriately determined according to each output of the adjustment section 11 and the platen glass temperature calculation section 15. In particular, the CPM down control timing performed based on the magnification and paper size is appropriately delayed with reference to the CVR value of the CVR adjustment section 11.

Next, in the latent image forming section 5, the optical image drawn on the photoreceptor is converted into an electrostatic latent image, and then in the developing section 6, the latent image is converted into a toner image. Further, the toner image is subjected to heat fixing processing in the fixing section 7, and is discharged outside the machine. During this time, the temperature at a suitable location of the fixing section 7 is measured by the temperature detection section 13, and from this temperature the off time calculation section 12 calculates the off time after the operation is stopped.
It is calculated by Then, based on this off time, the preprocessing section 14 determines whether or not to perform the charging process on the photoreceptor K, and the platen glass temperature calculation section 15 calculates the platen glass temperature.

〔Effect of the invention〕

As described above, the copying machine of the present invention is configured to reduce the number of copies per unit time every time the number of consecutive copies exceeds a preset threshold, and the number of copies starts decreasing. This feature is characterized by the provision of means for appropriately delaying the timing according to the voltage value of the light-emitting lamp for document reading, so that overheating of the platen glass can be prevented without providing a temperature sensor on the platen glass and without reducing the processing speed too much. Preventive control can be performed.

As a result, the excellent effect of maximizing the processing performance of the apparatus while controlling the temperature of the platen glass with a simple configuration is achieved.

[Brief explanation of drawings]

Fig. 1 is a principle configuration diagram of the present device, Fig. 2 is a block diagram, Fig. 3 is a flowchart showing the main operations, and Fig. 4 is a flowchart showing the main operations.
The figure is a characteristic diagram showing the relationship between platen glass temperature and CVR value, Figure 5 is an experimental example showing the change in platen glass temperature due to CPM down, Figure 6 is platen glass temperature and magnification,
FIG. 3 is a characteristic diagram showing the relationship between paper sizes. 1-Image forming apparatus main body 2-Original reading section 3-Image generation section 4-Drawing section 5-Latent image forming section 6-Developing section 7 Constant deposition section 8-CP M setting section 9-Magnification detection section 10-Number of sheets detection Section 11-CV R adjustment section 12-Off time calculation section 13--Temperature detection section 14-Pre-processing section 15-Platen glass temperature calculation section K-Photoconductor P-11 Recording paper Fig. 3 Fig. 4

Claims (1)

[Claims] Each time the number of consecutive copies exceeds a preset threshold,
A copying machine configured to reduce the number of copies per unit time, characterized in that the copying machine is provided with means for appropriately delaying the start time of the reduction in the number of copies according to the voltage value of a light-emitting lamp for reading originals. Machine.