JPH0486677A - Copying machine - Google Patents

Abstract

PURPOSE:To prevent overheating of a platen glass without utilizing a temperature sensor by constituting the copying machine so that copied number of pieces per time unit is changed according to the continuously copied number of pieces and effective calorific value. CONSTITUTION:The device is provided with means to detect the continuously copied number of pieces, paper size, and copying magnification of recording paper, and a means to calculate the effective calorific value = (paper size) X(copying magnification), and is constructed so that the CPM value (copied number of pieces per minute) is varied according to the continuously copied number of pieces and the effective calorific value. That is, an original mounted on the platen glass 1 is irradiated by light from a light emitting lamp, and reflected light is transmitted as image information to a plotting part 4 through an original reading part 2. On the other hand, the CPM value is appropriately decided according to each output of a magnification detection part 9, a continuously copied number of pieces detection part 10, and the effective calorific value calculating part 11 at a CPM setting part 8. Thus, overheating of the platen glass 1 can be prevented without utilizing any special temperature sensor and while the original ability of the device can be displayed to the maximum.

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 in a reading section, and the reflected light causes a photoconductor (OPC (organic photoconductor), etc.) to be placed on a drum or belt. The basic configuration is to form an electrostatic latent image, convert the electrostatic latent image into a toner image in a developing section, transfer it onto recording paper, and thermally fix it in a fixing section.

In this conventional copying machine, if the platen glass rises above a predetermined temperature (eg, 75° C.), there is a risk of physical or psychological harm to the user. In particular, for products exported to the United States, this point is strictly regulated by UL standards.

For this reason, in conventional equipment, as a measure to prevent the platen glass from overheating, the temperature of the platen glass is actually measured using a temperature sensor, and if the temperature exceeds a predetermined value, the CPM value (number of copies per minute) is reduced. (JP 61219967, JP 6l-261753).

■Shorten the lighting time of the light emitting lamp for the second and subsequent copies during continuous copying (
(Japanese Patent Application Laid-Open No. 58-111958).

The following configuration was adopted.

[Problem to be solved by the invention]

However, in the above-mentioned conventional copying machine, the one using the temperature sensor (1) results in increased man-hours and costs associated with sensor installation, and a complicated device configuration.

(2) Shortening the lighting time of the light emitting lamps for the second and subsequent sheets will reduce the processing speed more than necessary, making it impossible to achieve the original performance of the device.

There are some problems.

In addition, if the CPM value is set appropriately according to the paper size and copying magnification set by the user, and the CPM value is reduced when the number of continuous copies exceeds a predetermined threshold, it is extremely simple. It is possible to prevent overheating of the platen glass. However, in this case as well, CPM control is not performed according to the amount of heat generated by the light-emitting lamp, so the processing speed is set to a low value (on the safe side against overheating), which prevents the device from achieving its original performance. There are many things.

In view of the above points, it is an object of the present invention to provide a copying machine that does not require a special temperature sensor and can prevent overheating of the platen glass while maximizing the original performance of the device.

[Means to solve the problem]

In order to achieve the above object, the copying machine of the present invention includes means for detecting the number of consecutive copies of recording paper, paper size, and copying magnification, and means for calculating effective heat generation value = (paper size) x (copying magnification). CP according to the number of continuous copies and effective value of heat generation.
The configuration is such that the M value can be changed, and the change in the CPM value can be precisely adjusted.

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

First, the heat radiation characteristic of the surface temperature of the fixing roller over time assumes that the temperature inside the machine is constant regardless of the outside temperature, and the temperature over time - T
, initial temperature = 190°C1 proportionality constant = K, internal temperature = 2
Assuming 5°C1 time constant -η, off time = τ, and undetermined constant = C, approximately, T (r) = Ke x p (-r/77)
It can be expressed as +C-(1). FIG. 4 is a diagram showing the heat dissipation characteristics of the heating section (fixing section) of the apparatus of the present invention.

Here, since T (0) = +C = 190°C and T(ω) = C = 25°C, 1,', = T (0) - T ((X)) = 190-2
5 = 165. That is, T (r) = 165e xp (-r/ 77)
+25 −・(1)′. Next, τ/η=1, i.e., exp (-r/ 77)=0.368T(τ)=8
6(''C), τ=10 (minutes), so the time constant η may be set as η=10.

Here, if the influence of the outside temperature is considered, the above formula (1)' becomes T= 165e x p (-T/ 10) +2
5+α−−−−−−(2). However, α is a correction value indicating the influence of the temperature difference between the main body of the apparatus and the outside air. As an approximate formula for this correction value α, a= (T*-25)(1-exp (-r/20)
) However, TII: Room temperature shall be used.

In this case, TI=10, which is assumed as the normal temperature range
．． When calculating T (10) and T (20) for each room temperature of 20.30℃, each time estimation error ΔT is as follows: ΔT (10) = within ±1 minute ΔT (20) = within ±2 minutes Ru. 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 block diagram showing the structure of the copying machine of the present invention, Fig. 2 is a block diagram as well, Fig. 3 is a flowchart showing the main operations, Fig. 4 is a heat dissipation characteristic diagram of the fixing section, and Fig. 5 is a diagram of variations in platen glass temperature under CPM control for A4 200% and B200% originals.

In FIG. 1.2, 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 to be optically scanned by a light emitting lamp of the original reading section 2 and output image information of 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 by the light beam from the drawing section 3 into an electrostatic latent image. has been done. However, if the off time determined by the method described below exceeds a predetermined length, the photoconductor is charged in the pretreatment section 11 so that it can retain sufficient residual charge. .

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. And recording paper P
is conveyed to the fixing section 7, and after the toner image is thermally fixed,
The paper is configured to be ejected 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 (1) the number of continuous copies, (2) the paper size of the recording paper, (2) the copying magnification, (2) the effective value of heat generation - (paper size) x (copying magnification), etc.

Here, the number of continuous copies of ■ is detected by the sheet number detection section 9, the paper size of the recording paper of ■ is detected by the paper size detection section 10, and the copy magnification of ■ is detected by the magnification detection section 11, and furthermore, the effective value of heat generation is calculated. The unit 20 is configured to calculate (paper size) x (copying magnification).

Reference numeral 8 denotes a CPM setting section, and the CPM setting section 8 has a plurality of threshold values set for CPM values, and is configured such that the optimum value among them can be appropriately selected during continuous copying. That is, first, continuous copying is started at the maximum CPM value (maximum processing speed), and when the number of continuous copies reaches a predetermined threshold level, the CPM value is reduced according to the paper size of the recording paper and the copying magnification. It has become. However, the timing of this CPM down is appropriately delayed according to the value of (paper size) x (copying magnification) calculated by the heat generation effective value calculation unit 20, and is adjusted so as not to excessively suppress the processing performance of the apparatus. .

Figure 6 shows how the platen glass temperature changes depending on the magnification, paper size, and number of sheets processed continuously.
00%, B4・200%''.

As is clear from this figure, by appropriately switching the CPM value while referring to the value of (paper size) x (copying magnification), it is possible to saturate the increase in platen glass temperature to 45° C. or less.

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 (-the above-mentioned off time) based on the information and the predetermined heat radiation aging characteristic of the temperature increasing section. That is, the off-time calculation section 12 stores the heat radiation characteristics of the temperature rising section over time in the memory in the form of a map, reversely looks up the map from the output information of the temperature detection section 13, and calculates the off-time. It can be estimated. Then, based on the off time determined by the calculation unit 12, it can be determined whether or not to perform the charging process in the preprocessing unit 14, and it is also possible to estimate the temperature of the platen glass. Note that the theoretical considerations regarding the principle of the time measurement method based on heat radiation characteristics over time are as described above.

In the embodiment described above, the original placed on the platen glass 1 is irradiated with light from the light emitting lamp, and the reflected light is transmitted to the drawing unit 4 as image information via the original reading unit 2. On the other hand, the CPM setting section 8 appropriately determines the CPM value according to the respective outputs of the magnification detection section 9, the continuous copy number detection section 10, and the heat generation effective value calculation 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 the appropriate location of the fixing unit 7 is measured by the temperature detection unit 13 *From this temperature, the off time calculation unit 12 determines the off time after the operation is stopped.
It is calculated by Based on this off time, the pre-processing section 14 can determine whether or not to perform the charging process on the photoreceptor K, and the platen glass temperature calculation section 15 can also calculate the platen glass temperature.

〔Effect of the invention〕

As described above, the image forming apparatus of the present invention includes means for detecting the number of continuous copies of recording paper, paper size, and copying magnification, and means for calculating effective heat generation value = (paper size) x (copying magnification). The feature is that the number of copies per unit time is changed according to the number of continuous copies and the effective value of heat generation, so it is possible to determine when the CPM value will decrease while referring to a value close to the actual heat generation value. Can be precisely adjusted.

As a result, the platen glass can be prevented from overheating with a simple configuration that does not use a temperature sensor, and high-speed processing can be performed without excessively suppressing the device performance.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram showing the structure of the copying machine of the present invention, Fig. 2 is a block diagram as well, Fig. 3 is a flowchart showing the main operations, Fig. 4 is a heat dissipation characteristic diagram of the fixing section, and Fig. 5 is a diagram of variations in platen glass temperature under CPM control for A4 200% and B200% originals.゛Fixing section - CPM setting section - Magnification detection section 0 - Number of sheets detection section 1 - CVR adjustment section 2 - Off time calculation section 3 - Temperature detection section 4 - Preprocessing section - Photoconductor - Recording Paper patent applicant: Konica Corporation 1 - Copying machine body 2 - Original reading section 4 - Drawing section 5 - Latent image forming section 6 - Developing section

Claims (1)

[Scope of Claims] The invention includes means for detecting the number of continuous copies, paper size, and copying magnification of recording paper, and means for calculating effective heat generation value=(paper size)×(copying magnification), A copying machine characterized by being configured to change the number of copies per unit time according to an effective value of heat generation.