JPS63309983A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the breakage of a form and the scatter of toner when jamming, etc., happens by reducing the press-contacting force between a heat roller and a pressure roller according to the opening of an upper frame and releasing a rotation transmission mechanism for a roller from a driving source. CONSTITUTION:When the upper frame 2 is opened at the time of executing a maintenance job since the jamming happens, the press-contacting force between the heat roller 6 and the pressure roller 8 is reduced, and also the rotation transmission mechanism from the driving source such as a main body motor, etc., is separated from the rotation means of the heat roller 6. Then, the resistance of rotation between the heat roller 6 and the pressure roller 8 is made smaller and the form 14 can be drawn out with a slight force while the heat roller 6 and the pressure roller 8 are rotating in a contact state, if the form 14 which is put between the heat roller 6 and the pressure roller 8 is drawn. At such a time, the application of current to the heating means of the heat roller is cut, but the unfixed toner can be fixed with remaining heat. Thus, the scatter of the toner on the form 14 to the main body 1 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image forming apparatus that develops an electrostatic latent image formed on the surface of a photosensitive member with toner particles, further transfers the powder image onto paper, and then thermally fixes the image. It is related to.

BACKGROUND OF THE INVENTION Conventional heat fixing devices for image forming apparatuses are equipped with a heat roller that has a heat source such as a halogen lamp inside, and a pressure roller that rotates in contact with the heat roller with an appropriate pressure. 2. Description of the Related Art A thermal fixing device is known that performs fixing by moving a sheet of paper on which toner particles have been transferred between a pair of rollers. In an apparatus having such a structure, when paper jamming occurs, the image forming apparatus (hereinafter referred to as the main body) must be opened and the paper removed when transporting the paper. A pair of rollers, a heat roller and a pressure roller, is connected via a rotation transmission mechanism such as a gear.
Since it is connected to a drive source such as a motor and a large pressure force (for example, 10 kg or more) is applied between the pair of rollers, a large amount of force is required to pull out the paper from between the pair of rollers. , which caused the paper to become damaged. In addition, unfixed toner on the paper may adhere to the surface of the heat roller, and during subsequent fixing operations, the toner adhering to the surface of the heat roller may adhere to the paper.
There were problems such as unfixed toner scattering into the main body. Therefore, a mechanism has been proposed in which the pair of rollers are released from the contact rotation state using the opening operation of the paper conveyance section of the main body.

A conventional example will be described below with reference to screens.

In FIG. 3, an upper frame 2 is attached to a main body 1 of the image forming apparatus via a hinge 3 so as to be openable and closable. 4 is an instruction member for maintaining the upper frame 2 in an open state. Note that a heat fixing device 5 is attached to the main body 1 at a predetermined position.

FIG. 4 shows the heat fixing device 5. In the figure, 6 is a hollow heat roller, which has a heat generation source 7 made of a halogen lamp inside. A pressure roller 8 is made of an elastic member, and is rotatably supported by an L-shaped arm 9. The arm 9 is attached to the base 1 of the heat fixing device 5.
0 so as to be rotatable about a shaft 11.

Further, the pretour roller 8 is biased by the spring 12 in a direction opposite to the heat roller 6 side. here,
13 is the summary 14 of the heat roller 6 and the pressure roller 8.
It is a guide part that guides between a pair of rollers consisting of 1
5 is a discharge roller that discharges the paper 14. One of the discharge rollers 15 is rotatably attached to the base 10 and the other to the L-shaped arm 9. 16 has an adjustment screw,
It is adjustably fixed to the L-shaped arm 9 by a nut 17, and when the upper frame 2 is closed, the bushing rod 18
pushed by A spring 19 is installed on the bushing rod 18. The pressure roller 8 is pressed against the heat roller 6 with a substantially constant pressure. The pressure contact force can be varied by adjusting the height of the adjustment screw 16. In this way, an appropriate pressure contact force is applied to the heat roller 6 and pressure roller 8, and the rotation from the drive source is transmitted. Since the heat roller 6 is rotated via a mechanism (not shown), the paper 14 is fed by the pressure roller 8 and the heat roller 6.

The operation of the conventional example configured as described above will be explained. As shown in FIG. 5, when the paper 14 on which unfixed toner has been transferred is conveyed between a pair of rollers when the upper frame 2 is in the closed operating state (printing operating state), the heat generating source 7
The toner is fixed onto the paper 14 by the heat and the pressing force between the heat roller 6 and the pressure roller 8. Here, if jamming occurs while the paper 14 is passing between the heat roller 6 and the pressure roller 8 due to some inconvenience, the user performs the jamming release operation as follows. First, when the upper frame 2 of the main body 1 is operated, the contact rod 18 on the upper frame 2 is disengaged from the adjustment screw 16 formed on the heat fixing device 5. That is, the pressure roller 8
is released from the contact state with the heat roller 6 as shown in FIG. do not have.

Problems to be Solved by the Invention However, since there are places where the toner on the paper 14 is not yet fixed, the paper 14 is carelessly pulled out from between the heat roller 6 and the pressure roller 8 (and the paper 14 is unfixed).
The toner on the heat roller 6 may scatter into the main body 1.
Sometimes it adheres to the surface of In this case, problems may arise in subsequent fixing operations. Furthermore, there are other drawbacks such as the operator's hands getting dirty with toner.

Means for Solving the Problems The present invention solves the above-mentioned conventional drawbacks, and its technical means are to divide the frame into upper and lower parts, to make the upper frame openable, and to separate the fixing heat roller and pressure roller. A means is provided to make the contact pressure strong when the upper frame is closed and weak when the upper frame is opened; A means is provided for turning off the power of the heat source that heats the roller.

For production Therefore, the effects of the above technical means are as follows.

When jamming occurs and the upper frame is opened for maintenance, the pressure contact force between the heat roller and pressure roller is reduced, and the rotation transmission mechanism from the drive source such as the main body motor is separated from the rotation means of the heat roller. Therefore, the rotational resistance of the heat roller and pressure roller is small, and when the paper sandwiched between the heat roller and pressure roller is pulled, the paper can be pulled out with a light force while rotating the heat roller and pressure roller in contact with each other. At this time, although the heating means of the heat roller is cut off, the unfixed toner is fixed by preheating the heat roller.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. Note that components having the same functions as those of the conventional example are given the same numbers.

FIG. 1 is a side view of the thermal fixing device 5 in a printing state. In the figure, 6 is a heat roller that has a heat generation source 7 such as a halogen lamp inside, and a gear 2
2, 23, and 24. The gear 22 is coupled to the output shaft of the drive source, the gear 23 is attached to the upper frame 2, and the gear 24 is coupled to the heat roller 6. A pressure roller 8 has a surface covered with an elastic member such as rubber, and is rotatably supported on an L-shaped arm 9.
rotates about a shaft 11 fixed to a base 10 of the heat fixing device 5 as a fulcrum. Here, 20 is Bushrod,
The tongue piece 9a of the L-shaped arm 9 is slidably formed between the hole 9b of the tongue piece 9a of the L-shaped arm 9 and the hole 10b of the tongue piece 10a of the base 10. A spring 21 is inserted between them. Reference numeral 22 denotes a contact portion formed on the upper frame 2, which presses down the bushing rod 20 when the upper frame 2 is in the closing state, and presses the pressure roller 8 against the heat roller 6 via the L-shaped arm 9. A microswitch 25 is connected between the power source and the heat generating source 7, and is turned on when the bushing rod 20 is pushed down by the upper frame 2, and turned off when the upper frame 2 is in an open state.

In this embodiment configured as described above, the operation will be explained. As shown in FIG. Press down. Then, the bushing rod 20 rotates the L-shaped arm 9 about the shaft 11 by the force of being pushed down, and presses the pressure roller 8 against the heat roller 6 with a constant pressure. Here, the rotational force from the drive source of the main body is transferred to the gear 22. Gear 23. It is transmitted to the heat roller 6 via the gear 24, and the heat roller 6 is rotationally driven, so that the heat roller and the pressure roller 8 are
The paper 14 held between them is conveyed in the direction of the arrow. Further, the microswitch 25 is turned on, the heat generating source generates heat, and the heat roller 7 is heated. The unfixed toner on the paper 14 is heated to a heat source 7 in the heat roller 6.
The image is fixed by the heat and the pressing force of the pressure roller 8.

Here, if jamming occurs while the paper 14 remains sandwiched between the pair of rollers due to some inconvenience, the paper must be removed. At this time, as shown in FIG. 2 (when the upper frame 2 is opened, the contact portion 22 is separated from the bushing rod 20).

Further, since the bushing rod 20 hits the base 10 of the heat fixing device 5 with the tongue piece 10a due to the stepped portion 20a and does not rise any further, the pressure roller 8 is pressed with a lighter pressure than when the upper frame 2 is closed as shown in FIG. It is pressed by the heat roller 6. The state will be as follows. Additionally, as the gear 23 separates from the gear 24 as the upper frame 2 opens,
The heat roller 6 is in a state where it can be easily rotated by external force. Further, since the heat roller 6 rotates with a light force in combination with the reduced pressure contact force with the pressure roller 8, when the paper 14 is pulled by hand, the paper 14 can be smoothly pulled out in the direction of the arrow. At this time, the microswitch 25 is off, so the power to the heat source 7 in the heat roller 6 is cut off. However, if it is a short time after the power is turned off, the paper 14 can be heated by preheating the heat roller.
The toner in the upper unfixed portion can be fixed on the paper 14. In the above embodiments, the driving force from the motor is transmitted to the heat roller, but the driving force may be transmitted to the pressure roller, or the driving force may be transmitted to both the heat roller and the pressure roller. It may be configured to convey the information.

Effects of the Invention The present invention is as described above (a frame is divided into upper and lower halves, the upper frame is attached to the lower frame so as to be openable and closable, and a predetermined pressing force is applied between the heat roller and the pressure roller when the upper frame is in the closed state. At the same time, a voltage is applied to the heating means of the heat roller to perform a heat fixing operation, and when the upper frame is opened, the pressure contact force between the heat roller and the pressure roller is reduced, and a rotation transmission mechanism from the drive source to the roller is provided. By making it easier to take out the paper when jamming or the like occurs, it prevents damage to the paper, prevents toner from scattering into the main body, and reduces print quality due to toner adhering to the heat roller. It prevents deterioration and also fixes unfixed toner by sandwiching the paper between the heat roller and the pressure roller, solving the inconvenience of operators such as getting their hands dirty, and its effects are extremely large. be.

In the above embodiments of the present invention, the pressure contact force of the pressure roller is reduced by the L-shaped arm and the bushing rod. Various modifications are possible within a range that does not deviate from the above.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of an image forming apparatus according to an embodiment of the present invention showing the upper frame in a closed state, FIG. 2 is a cross-sectional view of the main parts showing the upper frame in an open state, and FIG. FIG. 4 is a side view showing the upper frame in an open state; FIG. 5 is an exploded cross-sectional view of main parts of a conventional image forming apparatus showing the upper frame in a closed state. , FIG. 6 is an enlarged sectional view of the main part, and FIG. 7 is a sectional view of the main part showing the upper frame in a closed state. 1... Image forming device 2... Upper frame 3... Hinge 4...
- Support member 5... Heat fixing device 6... Heat roller 7... Heat generation source 8... Pressure roller 9... L-shaped arm 9a... Tongue piece 9b.
... Hole 10 ... Base 10a ...
・Tang piece 10b...hole 11...shaft
12...Spring 13...Guide part
14... Paper 15... Ejection roller 1
6... Adjustment screw 17... Nut 18.
... Contact rod 19 ... Spring 20 ... Bush rod 20a ... Step portion 21 ... Spring 2
2... Name of contact department agent Patent attorney Toshio Nakao and one other person No. 214 1 (75'7 1J,) Figure 3

Claims (1)

[Claims] A heat fixing means having a heat roller and a pressure roller that presses the heat roller and the pressure roller against each other is provided, a drive source for rotationally driving at least the heat roller or the pressure roller is provided, and the pressing force of the heat roller and the pressure roller is in a strong state or A switching means is provided for switching to a weak state, and in response to the switching means, the driving force is transmitted from the drive source to the pressure roller or the heat roller when the pressing force is strong, and when the pressing force is weak, the driving force is transmitted from the drive source to the pressure roller or the heat roller. An image forming apparatus comprising: a driving force transmitting means that does not transmit driving force from the driving source to the pressure roller or the heat roller.