JPH04355782A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain the recorded image of high image quality with a small-size and inexpensive constitution by reducing fluctuations of driving various kinds of thickness enter between rollers. CONSTITUTION:A press-contacting means 7 pressing the transfer material 11 is provided on the upstream side on the carrying passage of the transfer material 11, compared with a transfer position, and a displacing means for displacing a pressure roller 6 according to the displacement of the press-contacting means 7, which occurs when the transfer material 11 passes the press-contacting means 7, is provided. The press-contacting means 7 is composed of a pair of hard rollers, constituted so that, at least, one of them can be displaced by the enter of the transfer material 11, and provided in a location where a distance with respect to a transfer position is shorter than the length of the transfer material 11, and equal to the distance front an electrostatic latent image forming position to the transfer position, or longer than it.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that records a toner image formed on a recording medium onto a transfer material by pressure transfer or pressure transfer and simultaneous fixing. printers, copiers,
Used for facsimile, etc.

0002

2. Description of the Related Art FIG. 4 shows the structure of an image forming apparatus using pressure transfer, which is described in Japanese Patent Application Laid-Open No. 57-501348. Rotatable recording medium 101
An electrostatic latent image consisting of a large number of dots is formed on the recording head 102 of the ion flow type, and this latent image is developed with toner by the developing device 103, and this toner image is transferred to the recording medium 1.
Transfer material 10 conveyed between 01 and pressure roller 104
It is fixed at the same time as it is transferred onto 5. Toner and latent images remaining on the recording medium 101 are removed by a static eliminating cleaning device 10.
6 and configured to prepare for the formation of a new latent image.

0003

[Problems to be Solved by the Invention] However, in such an image forming apparatus, the recording medium and the pressure roller are pressed against each other with a large force of, for example, about 1 ton, so if the transfer material enters between them, Since the driving torque of the recording medium increases rapidly and fluctuates greatly, there is a problem in that the motor serving as the driving source must be made large.

[0004] Further, rapid fluctuations in the driving torque cause uneven rotation of the recording medium, resulting in uneven pitch of the recorded image. In order to avoid pitch unevenness, there is a method of detecting the rotation of the recording medium with a rotary encoder and using the signal from this encoder as a reference synchronization signal to control the image formation timing of the recording head, but the device is expensive. There is a problem with becoming.

In addition, in the pressure fixing device disclosed in Japanese Utility Model Publication No. 56-47639, as a method of reducing the load when the recording paper enters between the rollers, a fixed roller, a pressure roller, or both of the rollers are coated on the circumferential surface. , a concave groove is provided along the circumferential direction, and a rectangular cross-section gap is formed between the rollers, the gap being wider than the width of the recording paper and narrower than the thickness of the recording paper, and the recording paper is inserted into this gap. A method of passing while applying pressure is disclosed. However, although this method is highly effective in reducing drive torque fluctuations and rotational unevenness,
It is not possible to handle recording paper that is thinner than the size of the gap with a rectangular cross section, and if the size of the gap is set small to accommodate thin paper, fluctuations in driving torque and There is a problem in that the effect of reducing rotational unevenness is lost.

Furthermore, in the pressure roller shock absorbing device disclosed in Japanese Patent Application Laid-Open No. 61-90167, when the recording paper enters between the rotating image carrier and the pressure roller and/or is ejected, A method of providing a buffer member to reduce the pressure applied by the pressure application device to the pressure roller has been proposed, but the first embodiment is one in which buffer members are provided upstream and downstream of the pressure transfer mechanism, Increasing the size of the equipment is unavoidable. In the second embodiment, a buffer member is provided only upstream to reduce the impact when the recording paper enters. As with the first embodiment, although the impact reduction effect of the buffer member is large, slight uneven rotation of the image carrier occurs even at the moment when the recording paper enters the buffer member, which may cause pitch unevenness of the image. Therefore, countermeasures are required to obtain higher image quality.

The present invention is intended to solve the above-mentioned problems, and has a small and inexpensive structure, and reduces fluctuations in driving torque and uneven rotation when transfer materials of various thicknesses enter between rollers. The purpose is to obtain high-quality recorded images.

[0008]

[Means for Solving the Problems] In the present invention, the pressure contact means for pressing the transfer material is provided upstream of the transfer material transport path from the transfer position, and the pressure contact means generated when the transfer material passes through the pressure contact means. The present invention is characterized in that a displacement transmitting means for displacing the pressure roller according to the displacement is provided. Here, the upstream side of the conveyance path of the transfer material from the transfer position refers to the area before the transfer seen from the transfer position when the transfer material is conveyed on the conveyance path from the conveyance start position, passes the transfer position, and ends conveyance. It is about the side of Similarly, the downstream side from the transfer position refers to the side after transfer.

[0009] Furthermore, the pressure contact means is composed of a pair of hard rollers, and at least one of them is constructed so that it can be displaced by the introduction of the transfer material. The pressure contact means is provided at a position where the distance from the transfer position is shorter than the length of the transfer material and is equal to or longer than the distance from the electrostatic latent image forming position to the transfer position, and the pressure contact means It is characterized in that the amount of displacement of the pressing roller is not larger than the amount of displacement of the pressing means.

0010

[Operation] When the transfer material is conveyed and enters the pressure contact means, at least one of the displaceable rollers is displaced against the pressure contact force so that the rollers are separated from each other. This displacement is transmitted to the pressure roller by the displacement transmission means, and the pressure roller is displaced in a direction away from the recording medium. This amount of displacement corresponds to the thickness of the transfer material, and is configured so as not to be larger than the amount of displacement of the pressing means. Since the transfer material enters the transfer position with a portion of it pressed by the pressure contact means, the pressure roller maintains its displaced state, reducing fluctuations in drive torque and uneven rotation of the recording medium when the transfer material enters. However, it will still be subjected to sufficient pressing force.

Furthermore, since the electrostatic latent image forming step is always performed with the transfer material being pressed against the pressure contact means, uneven rotation of the recording medium that occurs when it enters the pressure contact means will not adversely affect the image. do not have.

0012

Embodiment FIG. 1 shows a first embodiment of the present invention. first,
The individual components will be explained. The ion head 1 has an ion generation source and an ion control section inside, and irradiates the recording medium 5 with ions in accordance with an image signal.

The developing device 2 uses conductive magnetic one-component toner to visualize the electrostatic latent image on the recording medium 5. Cleaner 3
is transferred to the recording medium 5 through a transfer process using a steel blade.
Scrape off any toner remaining on the top. The static eliminator 4 applies alternating current discharge to the electrostatic latent image remaining on the recording medium 5, thereby bringing the surface potential of the recording medium 5 to approximately 0V.

The recording medium 5 has an aluminum pipe cylinder as a base, the surface of which is anodized, sealed with resin, and polished. Therefore, a dielectric layer is formed on the surface of the recording medium 5, and has sufficient insulation to hold the electrostatic latent image formed by the ion head 1 up to the development position. Note that the support shaft of the recording medium 5 is rotatably held in the main body of the apparatus, and the support shaft will not be displaced even when the load increases due to pressure by the pressure roller 6 or entry of the transfer material 11. One support shaft of the recording medium 5 is connected to a drive motor, and the recording medium 5 is moved in the direction of arrow A.
to drive.

The pressure roller 6 is rotatably held by a pressure lever 9 having a fulcrum 8 on the downstream side of the transfer position, and is supported by a pressure urging means 10 provided at the upstream end of the pressure lever 9 to generate a load of about 700 kg. It is pressed against the recording medium 5 from below by a pressing force. The pressure roller used is a steel roll whose surface is coated with polyacetal resin. The pressure biasing means 10 uses a coiled compression spring.

In this embodiment, the displacement transmitting means of the present invention has the following features:
It is composed of a pressure lever 9, a fulcrum 8, and a pressure urging means 10. The pressure contact means 7 was provided 120 mm upstream from the transfer position, assuming an official postcard as a small transfer material. The pressure contact means 7 consists of a fixed roller 71 and a displacement roller 72. The support shaft of the displacement roller 72 is held by the pressure lever 9, and the support shaft is moved from the support point 8 by the action of the pressure urging means 10 like the pressure roller. Fixed roller 71 with a pressing force that is almost inversely proportional to the distance to
It is in pressure contact with the

Both the fixed roller 71 and the displacement roller 72 are made of steel. The operation of this embodiment configured as above will be explained with reference to FIGS. 1(b) and 1(c). FIG. 1(b) shows a state in which the transfer material 11 has entered the pressure contact means 7, and the leading edge thereof has not yet reached the transfer position. As the transfer material 11 enters, the displacement roller 72 is slightly displaced downward against the pressing force. As a result, the pressure lever 9 rotates clockwise about the fulcrum 8. Along with this, the pressure roller 6 is displaced downward, and the pressing force acting between the recording medium 5 and the pressure roller 6 becomes smaller than when there is no transfer material in FIG. 1(a). In this state, the transfer material 11 is conveyed and enters the transfer position as shown in FIG. 1(c). At this time, since the rear end of the transfer material 11 is pressed by the pressing means 7, the pressing force at the transfer position is still weakened. Therefore, the transfer material 11
Fluctuations in the driving torque that occur when the leading edge of the printer enters the transfer position were significantly reduced, and pitch irregularities in the recorded image due to rotational irregularities were at a level that caused no problems in terms of image quality.

FIGS. 2(a), 2(b) and 2(c) show a second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that in the second embodiment, a transfer material position detection means 12 is provided at the position where the transfer material enters. Since the other components are the same as in the first embodiment, the same names and reference numbers will be used for each component. Therefore, a description of each component will be omitted, and only the differences will be described below.

The transfer material position detection means 12 is an optical sensor equipped with a light emitting part and a light receiving part, and is provided on the transport path of the transfer material 11 and upstream of the pressure contact means 7. When the leading edge of the transfer material passes above the optical sensor, the output voltage level of the sensor changes and is transmitted to the ion head 1 as a transfer material entry detection signal. The ion head 1 starts forming an electrostatic latent image with a delay of t seconds from this signal. The time t is the rotational speed of the recording medium 5, the diameter of the recording medium 5, the angle between the electrostatic latent image forming position and the transfer position, the conveying speed of the transfer material, the distance between the transfer material position detection means 12 and the pressure contact means 7, and the pressure contact means. 7 and the distance from the transfer position, and the leading edge of the transfer material and the leading edge of the electrostatic latent image on the recording medium 5 are set to coincide at the transfer position. In the second embodiment, the rotation speed of the recording medium 5 and the transport speed of the transfer material are made equal, and the distance from the electrostatic latent image forming position to the transfer position is made equal to the distance from the pressure contact means 7 to the transfer position. Configured.

In the second embodiment, an optical sensor is used as the transfer material position detection means 12, but other means may be used as long as it detects the position of the transfer material and issues a signal. Needless to say. For example, a mechanical microswitch may be provided on the conveyance path of the transfer material. In addition, without providing a special transfer material position detection means, the position of the transfer material is determined based on various timing signals provided as a normal image forming apparatus, the above-mentioned time t is set accordingly, and the image forming apparatus is stabilized. It is also possible to decide the timing of electrolatent image formation. Various timing signals include, for example, a print signal that instructs an image forming apparatus in a standby state to start printing, and a JA signal that is used to detect paper jams in transfer materials, etc.
This is a signal emitted from the M sensor each time the transfer material passes.

Further, in the first embodiment and the second embodiment, when the transfer material enters the pressure contact means 7, the displacement roller 72, the pressure lever 9, or the pressure roller 6 is displaced. may be detected by an optical displacement sensor or the like. Further, a pressure sensor can also detect fluctuations in pressure due to entry of the transfer material. Further, as the transfer material enters, the pressure lever 9 rotates around the fulcrum 8, so the angle changes. A change in the amount of light reflected due to a change in this angle may be detected.

A third embodiment is shown in FIGS. 3(a), 3(b) and 3(c). The pressure lever 90 has a stepped shape, and the fulcrum 80 is provided between the pressure roller 6 and the pressure contact means 70. Here, the upper roller of the pressure contact means 70 is a displacement roller 702 and is held by the pressure lever 90. When the transfer material 11 enters the pressure contact means 70, the pressure lever 90 rotates counterclockwise about the fulcrum 80, and as a result, the pressure roller 6 is displaced in a direction away from the recording medium 5. By providing the fulcrum 80 at a position closer to the transfer position than the pressure contact means 70, the amount of displacement of the pressure roller 6 does not become larger than the amount of displacement of the displacement roller 702, and the transfer material 1
1 receives sufficient pressing force at the transfer position. When a printing test was conducted using the experimental machine constructed in this manner, it was confirmed that this embodiment also achieved the object of the present invention in the same manner as in the first embodiment.

In the embodiment, the roller of the pressure welding means was made of steel, but it is also possible to use a metal material such as stainless steel, or a hard resin such as polyacetal, polycarbonate, silicone resin, phenol resin, etc. on the surface of the metal material.
Alternatively, it is possible to use an inorganic material such as silicon carbide, silicon nitride, silicon oxide, alumite, etc., and/or hard rubber, etc., in accordance with the present invention.

[0024]

[Effects of the Invention] As described above, according to the present invention, the above-mentioned conventional problems can be solved, and the structure is small and inexpensive.
It was possible to reduce fluctuations in driving torque and uneven rotation when transfer materials of various thicknesses enter between the rollers, and to obtain high-quality recorded images.

[Brief explanation of drawings]

[Fig. 1] Figs. 1(a), (b), and (c) show the first embodiment of the present invention.
FIG. 1 is a side view of an image forming apparatus showing an example.

[Fig. 2] Fig. 2(a), (b), and (c) show the second embodiment of the present invention.
FIG. 1 is a side view of an image forming apparatus showing an example.

[Fig. 3] Fig. 3(a), (b), and (c) show the third embodiment of the present invention.
FIG. 1 is a side view of an image forming apparatus showing an example.

FIG. 4 is a configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

1 Ion head 5 Recording medium 6 Pressure roller 7,70 Pressure welding means 71,701 Fixed roller 72,702 Displacement roller 8,80 fulcrum 9 Pressure lever 10 Pressure urging means 11 Transfer material

Claims (1)

[Claims] Claim 1: An electrostatic latent image on a recording medium is visualized using charged toner, and the toner image is applied with pressure when a transfer material passes between the recording medium and a pressure roll that is pressed against the recording medium. In image forming apparatuses that perform transfer or simultaneous transfer and fixing,
A pressure contact means for pressing the transfer material is provided upstream from the transfer position on the conveyance path of the transfer material, and the pressure roller is displaced in accordance with the displacement of the pressure contact means that occurs when the transfer material passes the pressure contact means. A transmission means is provided, and the distance between the transfer position and the pressing position of the pressure contact means is shorter than the length of the transfer material and is equal to the distance from the electrostatic latent image forming position to the transfer position along the outer periphery of the recording medium, or An image forming device characterized by a long length.