JPS6250866A - Image forming device - Google Patents

Abstract

PURPOSE:To perform invariably proper pressure transfer by providing a couple of rollers which detect the thickness of a transfer material, detecting variation in their gap by an optical means, and controlling the contacting pressure of a dielectric drum according to the thickness of the transfer material. CONSTITUTION:A rack 31 is fitted on the core of a paper thickness detection roller 27 and a gear 30 fixed on the core of a roller 28 is engaged with it. A plane mirror 32 is fitted at right angles to the external surface of the gear 30 and reflected light from a laser light source 345 is photodetected by a position detecting element 36 to detect the thickness of the transfer material from variation in the output of the element 36. A pressure motor is driven with its output through a control system to press the dielectric drum 1 and a transfer and fixing roller 2 against each other properly. Further, a detecting device similar to that of the rollers 27 and 28 is provided on the cores of the drum 1 and roller 2 and the pressure motor and an electric brake are controlled before and after paper presses to maintain an in variably proper press-contacting state.

Description

Detailed Description of the Invention (Field of Application in Industry-1-) The present invention relates to image forming apparatuses such as copying machines, laser beam printers, and other electrostatic recording devices, and particularly relates to an image forming apparatus formed on an image carrier. This invention relates to an image-forming device for pressure-transferring an image onto a transfer material 1-.

(Prior art) Recently, devices such as copiers and laser beam printers have come to be used as part of systems such as computer output devices, and these devices are required to be even faster and more reliable. . In order to meet this demand, developing,
In place of conventional devices that require each step of transfer and fixing, this system forms an electrostatic latent image on the surface of a dielectric drum in accordance with an image signal, and then visualizes the electrostatic latent image using a toner developer. The toner image is transferred from the surface of the dielectric drum to the transfer material-I by passing the transfer material through the pressure contact portion between the dielectric drum and the transfer and fixing roller that rotates in pressure contact with the dielectric drum. A device for pressure-fixing a toner image thereon is known from Japanese Patent Laid-Open No. 78134/1983.

According to this device, after the toner image is transferred from the surface of the absorbent drum to the transfer material, it is not necessary to perform fixing using a heat roller fixing device or the like in the next step. It is possible to reduce the size of the transfer material, and to make the conveyance path of the transfer material shorter than that of the conventional method. This has the extremely large effect of making it difficult for transfer material conveyance defects to occur and improving reliability.

Conventionally, drive control of a transfer fixing roller that is in pressure contact with a dielectric drum has been performed as follows. That is, a pressure motor and a pressure brake are used to detect the positions when the transfer fixing roller is in pressure contact with the dielectric drum and when it is separated from the dielectric drum using microswitches, and drive the transfer fixing roller in the direction of contacting and separating from the dielectric drum. was under 0N10FF control.

(Problems to be Solved by the Invention) However, in the case of such prior art, since the positioning of the transfer and fixing roller during pressurization is simply performed by a microswitch, problems such as abnormalities in the contacts of the microswitch may occur. If the operating position of the microswitch changes due to loosening of the spring, etc., phenomena such as too much pressure or not enough pressure may occur during operation.

When such a condition 7ffi occurs, the transfer and fixation becomes incomplete, and not only does the transfer efficiency deteriorate, but also residual toner pressurized after transfer and fixation remains on the dielectric drum and cleaning becomes difficult.

In addition, if too much pressure is applied and the machine turns over for a while, it will have a big impact on other mechanisms, and the pressure actually applied can be so great that it can even cause damage to the equipment.

Furthermore, since the amount of pressure is set only by detecting the one-stop position of the transfer and fixing roller using a microswitch, only a certain amount of pressure 71 can be applied. This has the problem of not being able to respond flexibly to changes in the thickness of the transfer material being passed through, such as the large impact that is given to the equipment when it enters between the body drum and the transfer/fixing roller.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to be able to always perform pressure transfer or pressure transfer and simultaneous fixing with an appropriate amount of pressure. An object of the present invention is to provide an image forming apparatus that can accurately detect the thickness of a transfer material and adjust the amount of pressure applied accordingly.

(Means for Solving the Problems) In order to achieve the object 1-, the present invention forms an electrostatic latent image on the surface of an image carrier according to an image information signal and visualizes the image, In an image forming apparatus, the developed image is pressure-transferred onto a transfer material by the contact pressure between the image carrier and a rotating body that rotates in pressure contact with the image carrier. A pair of rollers is disposed at a position where the transfer material passes between the rollers, and a reflection plate is provided which is rotationally driven via a mechanism that converts a change in the distance between the rollers into a rotation amount. a light source that emits a light beam whose position can be detected, and a detection element that detects the position of reflected light emitted from the light source and reflected by the reflector,
The thickness of the transfer material is detected by the output of the detection element, and the distribution contact pressure is controlled according to the thickness of the transfer material.

(Example) The present invention will be described below based on the illustrated example. 1st
In the figure, l is a dielectric drum serving as an image carrier, and around the dielectric drum l, a latent image corresponding to an image signal is formed on the drum surface. Recording head 1 which is image forming stage p
01. A developing device 102 for making the latent image visible, a cleaning device 103, and a static eliminator 104 are provided. Reference numeral 2 denotes a transfer and fixing roller which rotates in pressure contact with the dielectric drum 1. The transfer and fixation roller 2 is rotatably supported by first arms 3 and 4, and this first arm 3.4 is supported at a fulcrum 5.4. It is possible to recruit mainly 6. Further, the swinging end of the first arm 3.4 is connected to one end of the second arms 8, 9 via a spring 7. This second arm 8.9 is swingable fE about a vehicle 10.11 located approximately in the center.

The other ends of the second arms 8 and 9 are in contact with the rollers 14 provided at the eccentric parts of the discs 12.13 so as to be able to push down the four ends of the discs 12.13. A pressure gear 16 is fixed to the disk 13 side of the support shaft 15. This machined tooth 1F16 is meshed with a control gear 18 fixed to the brake shaft of the electric brake 17, and further,
The control gear 18 is meshed with a drive gear 20 fixed to a drive shaft of a pressurizing motor 19.

Further, a rack 21 is provided on the non-rotating axis of the dielectric drum l and extends toward the axis of the transfer fixing roller 2.
A gear 22 fixed to a non-rotating shaft center portion of the transfer fixing roller 2 is meshed with the rack 21 . This gear 2
A flat mirror 23 is coaxially fixed to the mirror 2.

FIG. 2 is a schematic diagram of a paper feeding section in this apparatus, in which a transfer material (hereinafter simply referred to as a transfer sheet) 25 stored in a paper feeding cassette 24 is fed by a paper feeding roller 26,
Passing through the paper thickness detection rollers 27 and 28, the registration roller 2
It is transported up to 9. This registration roller 29 feeds the transfer sheet 25 to the pressure contact portion between the dielectric drum 1 and the transfer fixing roller 2 at a predetermined timing. As shown in FIG. 3, one of the two paper thickness detection rollers 27 has a tMM2O3 fixed to its non-rotating shaft and a tMM2O3 fixed to the non-rotating shaft of the other paper thickness detection roller 28, as shown in FIG. A rack 31 is provided. -1- The flat mirror 3 is in the tooth IIC30.
2 are coaxially mounted.

Further, in this embodiment, as shown in FIG. 4, the distance between the paper thickness detection rollers 27 and 28 and the distance between the dielectric drum 1 and the transfer/fixing roller 2 are detected. That is, when the distance between the recording paper thickness detection rollers 27 and 28 and the distance between the dielectric drum l and the transfer fixing roller 2 changes, the flat mirror 23. be done. Therefore, the light source 3 which emits a light beam C having strong directivity of laser light, etc., high illuminance, and the irradiation position of the emitted light can be detected from the flat mirror 23.32.
3.34 and the flat mirror 23.
One-dimensional position detecting elements 35 and 36 are provided for detecting the position of the reflected light reflected at 32. As the position detection elements 35 and 36, for example, a semiconductor device detection element (PSD) manufactured by Hamamatsu Photonics Co., Ltd. is used.

- By detecting the position of the reflected light by the position detecting elements 35 and 36, the flat mirror 23°32
The inclination of is determined, and the distance between the paper thickness detection rollers 27 and 28 and the distance between the dielectric drum 1 and the transfer fixing roller 2 are detected. In addition, the light source 33° 34 and the position detection element 35
．． 36 is arranged so as to move along with the axes of the transfer fixing roller 2 and the paper thickness detection roller 28.

FIG. 5 shows the principle of position detection of incident light in the PSD. As is well known, the PSD is a sensor for detecting the position of a light spot using a silicon photodiode. As shown in the figure, the structure consists of three layers: a P layer on the front surface of a flat silicon plate, an N layer on the back surface, and one layer in the middle.The light incident on the PSD is photoelectrically converted, The photocurrent is divided and output from the ' electrode attached to the P layer. In other words, when a light spot is incident on the PSD, a '-load proportional to the energy of the incident light is generated at the incident position, and this is reflected in the resistance layer (in this case, the P layer) as a dazzle of light.
It passes through and is output from the electrode. Since the resistance layer is formed to have a uniform resistance value over the entire surface, the photocurrent is extracted in inverse proportion to the distance to the electrode, that is, the resistance value.

Here, the distance between both electrodes is 2L, the photocurrent is IQ, and the current extracted from each electrode is 11. If I2, then the following relationship holds.

IQ = Il + I2 Here, if we assume that the left end of Figure 5 is the origin and that the light is incident at a distance of X from the origin as shown in the figure, then the position
teeth.

Thus, 11. I'm having trouble finding I2.
'I MV・I4 +l 4' b l-44
g I'jl 7E += :W H1 n,) 1.
You can find the % position.

FIG. 6 shows the control system of this embodiment.

In the figure, 37 and 38 are current-voltage conversion circuits, and 39 is an adder that calculates the denominator of equation (A). 40
is an amplifier, and its output is the numerator (2LXI
Output an analog voltage signal corresponding to 2). 41
is an analog divider which outputs position information X after performing a predetermined calculation. 42 is a CPU, transfer fixing roller 2
The pressurizing motor 19 is operated in response to the above-mentioned manual position information.
By controlling the electric brake 17 and the electric brake 17, the optimum contact pressure is obtained. 43 is a driver that drives the pressurizing motor 19 and the electric brake 17 based on signals from the CPU 42.

Note that an A/D converter may be used instead of the analog divider 41, and the division may be performed by the CPU 42.

In the configuration further north, in the image forming apparatus according to the present invention,
The pressing force between the dielectric drum and the transfer and fixing roller is controlled in the following manner. That is, after forming an electrostatic latent image on the surface of the dielectric drum 1 in accordance with an image signal, the electrostatic latent image is visualized by a developing device to form a toner image. In synchronization with this toner image formation on the dielectric drum l, the CPU 42
The sequence control is performed according to the flowchart shown in FIG. 7. First, position information
is read through the position detection element 36, the paper feed roller 26 is driven to feed the transfer sheet 25 from the paper feed cassette 24, and the transfer sheet 25 is passed between the paper thickness detection rows 527 and 28, and then transferred to the registration roller 29. Transport to. While waiting for the timing to send the transfer sheet 25 to the photosensitive drum 1 by the registration rollers 29, the rack 31 attached to the paper thickness detection rollers 27 and 28 and the flat mirror 32 fixed to the gear 30 detect when the transfer sheet passes. Position information X of the position detection element 36 of
Q' is read into the CPU 42, Ixo-xo'l is calculated and used as paper thickness data, and a pressure of 1 kt corresponding to the paper thickness data is calculated in advance from a table in the internal ROM (not shown) of the CPU, and the pressure is The pressure motor 19 is driven until it reaches an appropriate value of 1. That is, the pressure motor 19
When the gear 18.16 rotates, the gear 18.16 meshes with the drive gear 20.
The rotation of the support shaft 15 causes the rollers 14 to push down one end of the second arm 8.9. Then, the sliding ends of the first arms 3 and 4 are pushed up via the /henge 7, and the transfer and fixing roller 2 moves upward and comes into pressure contact with the dielectric drum l. As the transfer fixing roller 2 moves in one direction, the gear 22 attached to the center of the transfer fixing roller 2 also moves upward, and the gear IIZ meshing with the rack 21 also moves upward.
22 rotates. The position detection element 35 detects the inclination of the flat mirror 23 corresponding to the amount of rotation of the gear 22, and the position information XI is input to the CPU 42 to detect the pressurization. When the amount of pressurization reaches 1 at the proper level, the power supply to the pressurizing motor 19 is stopped via the driver 43, and the power is supplied to the electric brake 17, so that the brake 17 operates. The rotation of the control gear 18 is restrained by.

As a result, the dielectric drum 1 and the transfer/fixing roller 2 are held in contact with each other by a predetermined pressure. Here, the registration roller 29 rotates, and the transfer sheet 25 is transferred to the dielectric drum l.
In synchronization with the upper toner image, the toner image is fed into the pressure contact portion between the dielectric drum 1 and the transfer/fixing roller 2, and pressure transfer and pressure fixing are performed at the same time. Although this embodiment shows an example in which fixing is performed at the same time as pressure transfer, the present invention is not limited to this. Only pressure transfer is performed using a bipedal dielectric drum and a roller, and the fixing process is performed at the same time as transfer 1. It may be done after the process is finished.

Next, the CPU 42 executes pressure control during sheet feeding according to the flowchart of FIG. When the transfer sheet 25 passes between the dielectric drum l and the transfer fixing roller 2, the transfer fixed roller 2 moves downward by the thickness of the transfer sheet 25, and is thereby attached to the non-rotating shaft of the transfer fixing roller 2. The I&1 city 22 that has been moved also moves downward. Therefore, the gear 22 meshed with the rack 21 rotates, and the inclination of the flat mirror 23 changes. This changed slant stitch is detected by the position detection element 35, and the position information X1 during paper feeding is detected by the position detection element 35.
' is read into the CPU 42. The CPU 42 compares an appropriate value 2 from a table preset in the internal ROM (not shown) of the CPU with the pressing force corresponding to the position information XI'. If the proper value does not match 2, the brake 17 is turned OFF via the driver 43, the pressurizing motor 18 is turned ON, and the pressure is further applied until the proper value 2 is reached.

Proper (When Ik2 is reached, turn on brake 17.

By turning off the pressure motor 19, the transfer fixing roller 2 is fixed.

At the time when paper passing is completed, the brake 17 is released from the pressure of 0FFL.

In the above embodiment, the flat mirrors 23 and 32 are provided only at one end of the transfer fixing roller 2 and the paper thickness detection roller 27, but flat mirrors 23 and 32 are provided at both ends of the transfer fixation roller 2 and the paper thickness detection roller 27. It is also possible to provide positional information to obtain the position information, and in such a case, the pressure contact force of the transfer fixing roller and the paper thickness can be detected with higher precision.

In the above-mentioned embodiments, a dielectric drum is used as the image carrier, but the present invention can also be applied to a photosensitive drum as the image carrier. In this case, the photosensitive drum is subjected to well-known uniform charging and photoimage exposure to form a latent image.

(Effects of the Invention) The present invention has the above-described configuration and operation, and the distance between the pair of rollers for detecting the thickness of the transfer material is set by the reflection plate and the irradiation of the light beam reflected by the reflection plate. Since the position is detected by a detection element and the thickness of the transfer material is detected,
It is possible to optically detect the tilting of the reflector due to slight changes in the distance between the rollers with high precision, and the thickness of the transfer material is detected with high precision, and the transfer material is pressed into contact with the image carrier and rotated. The contact pressure of the rotating body can always be maintained at an appropriate level f1.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a main part showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a schematic diagram showing a conveyance system for the transfer sheet on the same side, and FIG. 3 is a detection of the H height of the transfer sheet. FIG. 4 is a schematic diagram showing the main parts of the mechanism, FIG. 5 is an explanatory diagram showing the operation of the position detection element, FIG. 6 is a block diagram showing the control system, FIG. FIG. 8 is a flowchart showing a program executed by the control system. Explanation of symbols 1...Dielectric drum 2...Transfer and fixing roller 1
7... Electric brake 19... Pressure motor 21.
31...Rack 22.30...Gear 23.32
...Flat mirror 35.36...Position detection element 42...CPU

Claims (1)

[Claims] An electrostatic latent image is formed on the surface of the image carrier according to the image information signal, and the image is visualized, and the visualized image is transferred by the contact pressure between the image carrier and a rotating body that presses against the image carrier and rotates. In an image forming apparatus that performs pressure transfer onto a material, there is provided a transfer material passing position between the transfer material supply section and the image carrier.
In addition to disposing a pair of rollers, a reflecting plate is provided that is rotationally driven through a mechanism that converts a change in the distance between the rollers into a rotation amount, and further emits a light beam whose position can be detected. A light source is provided, and a detection element is provided to detect the position of the reflected light emitted from the light source and reflected by the reflection plate, and the thickness of the transfer material is detected by the output of the detection element, and the thickness of the transfer material is detected. An image forming apparatus characterized in that the contact pressure is controlled according to.