JPH0375862B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus having a rotating body whose surface temperature is kept constant.

[Conventional technology]

Conventionally, in a transfer copying machine, which is one type of image forming apparatus, an electrostatic latent image is formed on an image bearing member such as a photoreceptor drum using an optical member, and this is developed with a developer to make it visible. Make it into a statue. This visible image is then transferred onto a recording material such as a transfer material (for example, plain paper such as transfer paper) using a transfer charger or the like. However, at this time, it is necessary to separate the transfer paper after transfer from the photoreceptor drum and transport it, and if a separation failure occurs during this process, the machine must be immediately stopped and the transfer paper that failed to be separated must be removed. Must-have.

In order to detect the presence or absence of such transfer paper that has failed to separate, conventional methods detect the reflected light from the transfer paper using light receiving elements such as CdS, phototransistors, and photodiodes, and detect when the transfer paper is separated from the drum. A circuit is provided which converts the change in the intensity of the reflected light due to the non-separation into a change in voltage value via the light receiving element.

However, when detecting transfer paper separation failure using reflected light, a light source with a high S/N ratio is used and The combination of light-receiving elements must be selected, the circuit is extremely complicated, and the response time is long. In addition, when such a method is adopted, the type of light source and light receiving element and operating conditions differ depending on the type of transfer paper, such as wall thickness and coloring, so that the detection of all transfer papers can be achieved in the most reliable and stable operating condition. It is difficult to do so.

Furthermore, since the photosensitive drum is always irradiated by a light source, an optical memory is generated on the photosensitive drum, which causes a problem that causes deterioration of image quality, which is considered most important in copying machines.

Also, from a cost point of view, it requires a light source with relatively large power consumption, requires the use of a complicated circuit to obtain a high S/N ratio, and has the drawback that it becomes an expensive detection device. It was hot.

[Purpose of the invention]

The present invention solves the above-mentioned conventional problems and provides an image forming apparatus capable of detecting failure of separation (jam) of a recording material from a rotating body without providing a special photo sensor.

[Summary of the invention]

To achieve the above object, the present invention includes a rotating body that comes into contact with a recording material heated by a heat source, a temperature sensing member that detects the temperature on the surface of this rotating body, and a rotating body that rotates based on the output of this temperature sensing member. An image forming apparatus having a control means for controlling a heating source so as to keep the temperature of the body surface constant, the image forming apparatus having a comparison means for comparing a rate of change in the output of the temperature sensing member with a predetermined value, the rate of change in the output of the temperature sensing member is It is characterized in that it is determined that there is a recording material separation failure when the value is equal to or greater than a predetermined value.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 explains the outline and structure of a copying machine to which an embodiment of the present invention can be applied. In the figure, reference numeral 1 indicates a photosensitive drum, which is rotated in the direction of the arrow in FIG. Surrounding the photosensitive drum 1 are a main charging charger 2 that charges the photosensitive member on the circumference of the photosensitive drum, an exposure optical system 3 that irradiates the charged photosensitive member surface with an image of a document (not shown), and an image A developing device 4 that converts an electrostatic latent image formed by irradiation into a toner image, a transfer charger 5 disposed in a transfer section, a separation charger 6 that removes charge from the photosensitive drum surface and separates the transfer paper, and a photosensitive drum 1 after transfer. Photoreceptor cleaners 7 for removing residual toner from the surface of the photoreceptor are sequentially arranged clockwise in FIG.

Based on the above configuration, the photosensitive member of the photosensitive drum 1 rotates through each process, forms a toner image, and transfers the toner image onto the transfer paper 8.

Normally, the photosensitive drum 1 is configured to have a heater built into the drum to keep the surface of the drum at a constant temperature at all times in order to prevent sensitivity shifts due to changes in environmental conditions, particularly changes in humidity.

Here, in order to measure the temperature of the photoreceptor, a temperature detection sensor 9 is arranged at the rear stage near the separation charger 6 as shown in FIG.
(The case of two sensors 9, 9a is also shown).

The present invention utilizes the temperature detection sensors 9 and 9a to detect separation failure.

Since a poorly separated jam wraps around the roller, the jam can also be detected by the sensor 9a.

For example, if a CdS binder-based NP photoreceptor coated with insulation is used as a photoreceptor, the photoreceptor drum 1
Assume that the surface of is maintained at approximately 40°C.

Now, considering the time that the transfer paper 8 is in contact with the photosensitive drum 1, the time for it to pass through the temperature detection sensor 9 near the separation charger after transfer is extremely short, and the heat capacity of the transfer paper 8 is comparatively small. During this period, the surface temperature of the transfer paper is equal to room temperature. Therefore, as shown in FIG. 2, the surface temperature of the photosensitive drum 1 is 40°C. Then, a temperature difference of about 20° C. will occur between the surface temperature of the photosensitive drum 1 and the surface temperature of the transfer paper.

As the temperature detection sensor 9, a contact type temperature detection sensor such as a thermistor may be used at a certain distance from the photosensitive drum 1, but it is preferable to use a non-contact type pyroelectric infrared sensor or the like on the photosensitive drum. It is better to provide it close to the surface of the photoreceptor. Particularly when using a pyroelectric infrared sensor, if the photosensitive drum 1, which is the infrared radiation source, fails to separate the transfer paper 8, the surface of the drum will be covered with the transfer paper, resulting in a large S. /N ratio is obtained.

Further, as shown in FIG. 3, the drum surface temperature requires a certain amount of time T0 from turning on the drum heater, which is at room temperature, to reaching a steady state. Until this time T0, the temperature of the surface of the drum is low, and the output of the temperature detection sensor 9 may become lower than the reference potential (for example, the potential for determining the occurrence of a separation failure signal). This results in a jam signal being output.

The present invention can also prevent false detection in such cases.

The present invention will be explained below using FIGS. 4 to 8. FIG. 4 is a block diagram of one embodiment of the present invention. The temperature detection sensor 9 (or 9a) detects the temperature of the temperature-detected member or a temperature corresponding thereto, and inputs its output to the temperature control means 10 and the differentiation circuit 11. This temperature control means 10 maintains the temperature detected member at a substantially uniform desired temperature.

The output from the sensor 9 is differentiated into an output change rate by the differentiating circuit 11 and input to the comparison circuit.

In this comparison circuit 12, the output differentiated by the output change rate is compared with a predetermined reference value (a plurality of reference values may be used for classification) to determine whether or not there is a separation failure of the recording material. .

As described above, when a wrapping jam occurs, the recording material generally wraps around the surface of the photosensitive drum 1, and the output of the temperature detection sensor 9 disposed near the separation point changes drastically. Therefore, when this output is differentiated, it becomes input to the comparator circuit 12 with a large output change rate not seen in a normal copying process. For example, the reference value of the comparison circuit 12 is set to be larger than the differentiated maximum value of the temperature detection sensor output at the time of rising mentioned above (which is smaller in absolute value than the differentiated value of the output at the time of jamming) and smaller than that at the time of jamming. If so, it can be immediately determined by comparing the large rate of change in output during jam with this reference value.

When it is determined that there is a jam, the microcomputer 13 issues a jam display 13a and a signal to stop the copying process 13b, and executes the process.

In this way, by comparing the output from the temperature detection sensor with a predetermined reference value in the form of an output change rate, it is possible to accurately detect recording material separation failure without false detection without providing a special jam detection sensor. I can do it.

Furthermore, if the filter circuit 11a is provided between the differential circuit 11 and the temperature detection sensors 9, 9a as shown by the line 14 shown by a dotted line (cutting the straight line between the temperature detection sensors 9, 9a and the differential circuit 11), it is possible to Harmless temperature changes that occur near a desired temperature due to external or internal factors of the temperature sensing member can be removed. Therefore, only the necessary positive differential output at the rise of temperature change, zero differential output during operation, and negative partial output in bad conditions such as winding can be obtained from the differentiating circuit 11, and the negative differential output is input. By detecting whether / is output, a jam can be detected more accurately and earlier.

Furthermore, the output of the temperature detection sensor is converted using only a filter circuit through a wiring 14C indicated by a two-dot broken line, and the determination as to whether it is abnormal or not is sent to the comparison circuit 12 or directly to the microcomputer 13, where several types of processing are performed. , wiring 1 shown with broken lines
Various methods can be applied, such as one in which an amplifier circuit 11b is provided in 4a to increase the output so that the situation can be judged accurately.

Next, FIG. 5 is a circuit diagram of a main part of an embodiment of the present invention.

The output from the temperature detection sensor 9 is differentiated by a differential circuit 11 consisting of an operational amplifier 15 having a filter effect that cuts out high frequencies, a capacitor 16, and resistors 17 and 17a.The differential output is compared with a reference potential VO by a comparator 18. Then, the switching transistor 19 is turned on and off based on the compared signals, and a jam signal 13a and a copying process stop signal 13b are sent to these operation control means.

Such a simple circuit allows accurate determination of recording material separation failure.

FIG. 6 shows an embodiment in which the present invention is applied to a fixing device.

The illustrated fixing device includes a heating roller 21 that has a built-in heating means, and a pressure roller 22 that has (or does not need to have) an external heating means that is arranged to rotate in contact with this heating roller. . The heating roller 21 has a structure in which the surface of a roll core 25 made of a metal with good thermal conductivity such as aluminum is thinly coated with a layer 24 of a releasable material such as tetrafluoroethylene or silicone rubber, and a heating means such as a heater lamp is installed inside. 23
is built-in. 10 is heating means 23, 23a
The heating roller 21, the pressure roller 2
By detecting the surface temperature of No. 2 and performing control operations based on the surface temperature, the surface temperature is always maintained at a certain constant temperature. In the figure, the controller 10 is divided into two parts, but it may be one. The pressure roller 22 has a structure in which the surface of a roll core 25a serving as a base body is coated with a layer 26 of a releasable material such as elastic rubber or silicone rubber, and rotates during the copying cycle in contact with the heating roller 21.

Although not shown, each roller is rotatably supported by a well-known support means, and one or both of the rollers are driven by a well-known drive means, or driven by driven rotation.

Moreover, the roller 2 of the temperature detection sensor 9, 9a
The position of the rollers 1 and 22 may be in contact with the rollers or with a gap between them, or the rollers 21 and 2
The arrangement may be such that a change in the surface temperature of No. 2 can be detected.

In this embodiment, pyroelectric infrared sensors are used as the temperature detection sensors 9 and 9a, and they are installed near the roller nip portion where they can quickly detect the wrapping of the toner image supporting material such as the transfer material 8 at the time of poor separation, that is, jamming. In order to increase the sensitivity of the sensors 9 and 9a and improve reliability, the sensors are placed as close to the roller surface as possible.

Next, the operation of this embodiment will be explained using the block diagram shown in FIG. 6 and the flow chart shown in FIG.

Reference numeral 27 denotes conversion means for converting the outputs from the sensors 9 and 9a as described above.

A conversion means 27 for converting the outputs of the sensors 9 and 9a into an output change rate consists of a differentiating circuit.

Among the temperature change rates of the heating roller 21 that occur during fixing, the negative and largest absolute value (if it changes depending on the environment, it can be varied depending on the conditions such as the room temperature, or the maximum value that takes these into consideration). As reference value A, if the differentiated output of sensor 9 has a larger absolute value than reference value A and is negative, it means that a jam has been detected, and the control signal can be issued to stop the process. .

Similarly, among the normal temperature change rates of the sensor 9a of the pressure roller 22, the negative one and the maximum absolute value is set as the reference value B, and the sensor 9a
If the differentiated output has a larger absolute value than the reference value B and is negative, a jam signal or a process stop signal may be output. Of course, these reference values A and B may both be the same value, or they may have a larger absolute value (and negative) than the reference values A and B, or they may have only the absolute value of the rising edge shown in Figure 2. A rate of change or a rate of change greater than the rate of change during fixing may be used as a new setting standard for jam detection.

In this embodiment, the reference values A and B are the maximum absolute values and are negative values for each roller.

When the main switch of an image forming apparatus having this fixing device is turned on, the heating roller 21 and the pressure roller 22 are heated by the heating means 23 and 23a, as shown in the relationship diagram shown in FIG. The surface temperature is raised to a desired temperature and controlled at that temperature.

FIG. 7 mainly shows an example of a flowchart of the ROM 33 in the microcomputer 13.

First, in STEP 1, sensors 9 and 9a are connected to each roller 2.
It is determined whether or not there are both signals detecting the surface temperature of 1 and 22. If not, feedback is performed until a sensor signal is detected. If there is that signal
In STEP 2, the sensor signal is converted by the conversion means 27, stored in the eye port 21, and sent to STEP 3.

In STEP 3, the change rate of the signal called from the I-O port 31 is passed through the multi-base 30 and the signal output from the sensor 9 is compared with a reference value A, and if it is smaller than the reference value A, the jam signal and process stop signal are transferred to the I-O port. Output via 34,
The jam indicator lamp 28 is turned on in response to the signal, and the process stop control means 29 stops the process.
Also, if the rate of change is greater than the standard A, the roller 21
Since this is normal, proceed to SEP4.

In STEP 4, the rate of change of the output signal from the sensor 9a is compared with the reference value B. If this rate of change is smaller than the reference value B, the jam indicator lamp 28 is turned on and the process stop process 29 is performed as described above, and if it is greater than the reference value, it is normal, so feedback is given and the above process is continued. do.

Once the process is stopped and the jam is displayed,
As shown in STEP 5, these states are maintained until a reset occurs, and when a reset signal is input, these states are released and the process is restarted, continuing the aforementioned control. The central processing unit 32 performs such processing.

Also in this embodiment, jam detection can be performed using the output of the temperature detection sensor for constant temperature control.

FIG. 8 is a flowchart of yet another embodiment of the present invention.

In this embodiment, jam detection is performed by comparing the values before and after the outputs of the temperature detection sensors 9 and 9a and converting them into output fluctuations without using a differentiating circuit.

Further, a filter circuit is provided in the jam detection circuit.

This filter circuit has a filter effect that removes small temperature changes within a certain range during operation and at the time of startup of the temperature-detected member such as the fixing roller, and as mentioned above, the temperature change increases at the time of startup. During operation, the temperature is constant or almost constant, and when jammed, the temperature change becomes extremely negative. Therefore, in this embodiment, a jam signal may be generated when the temperature change becomes negative. That is, the presence or absence of an output from the temperature detection sensor is determined in STEP 1, and if there is, it is filtered in STEP 2 and becomes the output from the filter. The output from this filter is
It is compared with the reference value C in STEP3. This standard value C
is initially below room temperature, or below the output relative to the temperature of the temperature sensing member before it is heated. Therefore, when the temperature-sensing member starts up, it is heated by the heating means until it reaches the desired temperature from room temperature, and the output from the filter also gradually increases, resulting in a malfunction that may cause a jam signal to be output. Not at all. If the output is smaller than the reference value C in STEP 3, the process is stopped and a jam display is performed, but if the output is greater than the reference value C, the reference value C is erased in STEP 4 and 6. Instead, the output compared in STEP 3 is replaced with a new reference value C and fed back. Following the same process, in STEP 3, you will be able to compare the previous output and the current output one after another.

Therefore, since the sensor output at the time of a jam is generally smaller than the reference value C, the jam can be detected using the output of the temperature detection sensor, and the jam can be detected accurately and early without any false jam detection at the start of the jam.

In STEP 5, only when a reset signal is received, the jam display is canceled and the process is restarted, and the jam detection performance is always maintained.

Although the flowchart for this embodiment has been shown for one temperature sensing means, it may be used for other temperature sensing means as well.

The shape, material, and heating means of the photoreceptor such as the photoreceptor drum and the fixing roller shown in the above embodiments, the number and arrangement of the temperature detection sensors, etc. are not limited, and any suitable ones can be applied to the present invention.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to accurately determine whether a recording material is separated or not by using the output of a temperature detection member for constant temperature control without providing a jam detection sensor such as a special photo sensor. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a copying machine to which an embodiment of the present invention is applied, FIG. 2 is a graph showing temperature changes detected by a temperature sensor over time, and FIG. 3 is a drum surface temperature vs. time. A graph diagram showing changes; FIG. 4 is a block diagram of an embodiment of the present invention;
5 is a circuit diagram of the main part of FIG. 4, FIG. 6 is a schematic diagram of another embodiment of the present invention, FIG. 7 is a flowchart of FIG. 6, and FIG. 8 is a further embodiment of another embodiment. FIG. 3 is an example flowchart. 1...Photosensitive drum, 6...Separation charger,
8...Transfer paper, 9,9a...Temperature detection sensor,
10... Temperature control means, 11... Differential circuit, 11
a...Filter circuit, 11b...Amplification circuit, 1
2... Comparison circuit, 13... Microcomputer, 13a... Jam display, 13b... Process stop, 15... Operational amplifier, 16... Capacitor, 18... Comparator, 21... Heating roller, 22
... Pressure roller, 23, 23a ... Heating means, 2
7... Conversion means, 28... Jam display lamp, 2
9...Process stop processing, 30...Multibase, 31, 34...Ioport, 32...Central processing unit, 33...ROM (ROM).

Claims (1)

[Claims] 1. A rotating body that is heated by a heat source and comes into contact with a recording material, a temperature detection member that detects the temperature of the surface of this rotating body, and a temperature detection member that detects the temperature of the surface of the rotating body based on the output of this temperature detection member. An image forming apparatus having a control means for controlling a heating source to maintain a constant temperature, the image forming apparatus having a comparison means for comparing a rate of change in the output of the temperature sensing member with a predetermined value, wherein the rate of change in the output of the temperature sensing member is equal to or higher than the predetermined value. An image forming apparatus characterized in that it is determined that there is a recording material separation failure when the above is the case. 2. The image forming apparatus according to claim 1, wherein the rotating body is a photosensitive drum that is developed with toner. 3. The image forming apparatus according to claim 1, wherein the rotating body is a heating roller that melts the toner on the recording material. 4. The image forming apparatus according to claim 1, wherein the temperature detection member is provided in a non-contact manner to the rotating body.