JPH03282578A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the phenomenon of the deterioration of an image caused by an toner offset for a long period by allowing pressure contact force to the fixing roller face of a cleansing roller gradually to be increased according to the progress of a utilization degree in the lapse of time. CONSTITUTION:The cleaning roller 4a formed with heat-resistant felt, and impregnated with silicone oil as a releasing agent is pressed to the face of the fixing roller 1. The face of the roller 1 which passes through a nip part (n), and where a recording sheet P is separated is cleaned in such a manner that stuck toner is collected by the roller 4a which is pressed to the face of the roller 1 and follower-rotated. The roller 4a is detachably, and replaceably attached to the top end side of one arm part 6b of a rocking lever 6, and the other arm part 6c of the rocking lever 6 allows the cam profile surface of a cam 8 to receive the bottom surface of its midway part. Then, a recording material sensor 18 and a CPU 21 detect the progress of the utilization degree of the fixing device in the lapse of time, and the drive of a motor 23 is controlled, and the cam 8 is gradually and sequentially driven and rotated counterclockwise via a reducing gear 24, so that the pressure welding force of the roller 4a to the roller 1 is increased.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to image forming apparatuses (or image forming methods) such as copying machines, laser beam printers, microfilm printers, facsimile machines, image display devices, and recording machines. , directly or indirectly (transfer) onto the surface of an image bearing member (electrofax sheet, transfer material sheet, electrostatic recording sheet, printing paper, etc.) using an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording. The present invention relates to a fixing device that fixes an unfixed toner image corresponding to target image information formed by the ) method as a fixed image on the surface of an image bearing member carrying the toner image.

More specifically, it relates to a fixing device that includes a rotating body (such as a roller body or a rotating endless belt body) that fixes an image by contacting a member carrying an unfixed toner image, such as a heat roller type or a pressure roller type, for example. .

(Prior Art) Conventionally, this type of fixing device has a member that carries an unfixed toner image between a pair of rotating rollers in pressure contact with a fixing (heating) roller whose temperature is maintained at a predetermined temperature and an opposing (pressure) roller. A heat roller method is often used in which a toner image is fixed on the surface of the recording material by heat and pressure by introducing and passing a recording material (hereinafter referred to as a recording material).

In such a fixing device, part of the toner of the toner image carried on the surface of the recording material adheres (offsets) to the surface of the fixing roller during the execution of the fixing process.

If no measures are taken to prevent this, the offset toner on the surface of the fixing roller will flow into the nip (fixing section) between the fixing roller and the pressure roller as the fixing roller rotates and onto the surface of the subsequent recording material. This will cause adhesion (re-offset) and deteriorate the image on the recording material.

Furthermore, the offset toner on the fixing roller surface is re-offset to the pressure roller surface that is in direct contact with the fixing roller when the paper is not passing, and the pressure roller surface becomes stained with toner, causing the recording material to run out.

Therefore, a means for cleaning the roller surface of the fixing roller and furthermore the pressure roller is provided.

Specifically, for example, a cleaning member such as a roller-shaped felt or an oblong bat-shaped felt impregnated with a suitable release agent such as silicone oil is placed in contact with the roller surface, and the offset toner on the roller surface is removed. The toner is collected to clean the roller surface, and a release agent is applied and supplied to the roller surface to prevent toner offset to the roller surface as much as possible.

By increasing the pressure of the cleaning member against the roller surface, the cleaning means increases the ability to collect offset toner from the roller surface, and also increases the amount of impregnated release agent that seeps out from the cleaning member. Release agent application performance is also improved.

However, if the fixing roller is pressed against the roller surface of the cleaning member with strong force for a long time, the damage to the fixing roller due to the sliding friction with the cleaning member will progress rapidly, and the amount of release agent that seeps out will be too large. Also, the release agent runs out faster.

Therefore, the pressing force of the cleaning member against the roller should be set to a moderate force (initial setting), taking the above into account.
The initial pressure contact force is maintained continuously.

(Problem to be Solved by the Invention) However, in this type of cleaning means, the cleaning member continuously comes into contact with the roller and collects the toner adhering to the roller surface. )
Even if there is no problem with the cleaning performance and mold release agent application performance of the cleaning member under the initial pressure contact force with the roller set in advance, as the equipment is used for a long period of time and its durability increases, the cleaning member may become trapped. As the roller becomes dirty with collected toner, its surface becomes covered with toner, and the ability to collect toner and apply a release agent such as silicone oil to the roller surface decreases.

Therefore, there is a problem that image deterioration due to toner offset gradually begins while the apparatus is used for a long time.

These problems are not limited to the heat roller type fixing device as in the example above, but are common to other fixing devices that include a rotating body that fixes an image by contacting a member carrying an unfixed toner image, such as a pressure roller type. There is also.

The present invention has been proposed in view of the above, and is capable of maintaining the cleaning ability of the cleaning means for the fixing rotary body for a long period of time, regardless of the durability of the fixing device, so that images due to toner offset can be removed. The purpose is to provide something devised to prevent the occurrence of deterioration phenomena over a long period of time.

(Means for Solving the Problems) The present invention provides: a rotating body that fixes an image in contact with a member carrying an unfixed toner image; a cleaning member for the surface of the rotating body that contacts the surface of the rotating body; and a cleaning member that contacts the surface of the rotating body. a pressurizing means for bringing the cleaning member into pressure contact with the surface of the rotating body; a means for detecting the progression of usage of the apparatus over time; A fixing device characterized by comprising: means for controlling the pressing means in a direction in which the pressing force is gradually increased in a predetermined manner.

(Function) That is, as the usage of the device progresses over time (the durability of the device progresses), the cleaning member of the cleaning means becomes dirty with the collected toner as described above, but the cleaning member is pressed against the fixing rotating body. By gradually increasing the force as the device durability progresses, the ability (cleaning ability) of the cleaning member due to the collected toner dirt increases.
The decrease in the release agent application ability is compensated for by the increase in the pressing force.

Therefore, the ability of the cleaning means to act on the fixing rotary member is maintained at a substantially constant level over a long period of time, and image deterioration due to toner offset is prevented for a long period of time.

(Embodiment) FIG. 1 shows a cross-sectional side view of an example of a heat roller type fixing device to which the present invention is applied.

Reference numerals 1 and 2 denote a pair of vertically parallel fixing rollers and pressure rollers that are brought into contact with each other with a predetermined contact pressure.

The fixing roller 1 has a fluororesin layer 1b having good releasability for toner formed on the surface of a core metal 1a, and a heat source 3 such as a halogen heater is inserted and built into the core metal 1a.

The pressure roller 2 has an elastic layer 2b made of a heat-resistant elastic material such as silicone rubber formed on the surface of a core metal 2a.

Bearing portions (not shown) at both ends of the pressure roller 2 are connected to support shafts 13, respectively.
A pair of left and right support members 13 (13) that can freely swing around a.
It is supported so that it can rotate freely in between. The support member 13 (13
) is constantly urged to rotate clockwise in the drawing about the support shaft 13a by a push-up spring 14 (14), and the upper surface of the pressure roller 2 is pushed against the lower surface of the fixing roller 1 by the rotational urging force. It is maintained in a pressed state with a predetermined pressing force. n
indicates a pressure nip portion between the fixing roller 1 and the pressure roller 2.

Reference numeral 5 denotes a temperature detection means such as a thermistor that is brought into contact with the outer surface of the fixing roller 1, and a temperature control circuit (not shown) including this temperature detection means 5 controls the current to the heat source of the fixing roller 1 to perform fixing. The temperature of the roller 1 is controlled to a predetermined fixing processing temperature.

4 is a cleaning device for one surface of the fixing roller, and as will be described later, a cleaning roller 4a, which serves as a cleaning member and is made of heat-resistant felt and impregnated with silicone oil as a release agent, is brought into pressure contact with one surface of the fixing roller. ing.

The recording material P on which the unfixed toner image Ta has been formed in an image forming mechanism (not shown) is transported to a fixing device by a transport device 16.
The process of passing through the nip n between the fixing roller 1 and the pressure roller 2, which are rotated in the direction of the arrow, by passing through the population guide 16a and passing through the nip n between the fixing roller 1 and the pressure roller 2. The unfixed toner image is fixed on the surface of the recording material by receiving heat and pressure.

The recording material P that has passed through the nip portion n is separated from the surface of the fixing roller 1 by a separation claw 1o, and is ejected by a pair of ejection rollers 15 by energizing a guide 17.

After passing through the nip part n, the surface of the fixing roller 1 from which the recording material P is separated is cleaned by a cleaning roller 4a which is in pressure contact with this roller surface and rotates as a result of the rotation, and the adhering toner is collected and cleaned. The impregnated silicone oil is applied to the nip portion n as the fixing roller 1 rotates, and is then used for fixing.

In the cleaning device 4, reference numeral 6 denotes a swinging lever that can freely swing around a support shaft 6a, and the cleaning roller 4a
, is removably attached to and supported on the distal end side of one arm portion 6b of the swing lever 6, and is free to rotate about the shaft 4b.

As mentioned above, the cleaning roller 4a is made of heat-resistant felt and has a cylindrical shape impregnated with a predetermined amount of silicone oil as a mold release agent, and is pressed against the fixing roller 1 in a direction substantially parallel to the fixing roller 1. It rotates following the rotation of the fixing roller 1.

The lower surface of the other arm portion 6C of the swinging lever 6 in the middle thereof is received by the cam profile surface of the cam 8. Reference numeral 7 denotes a tension spring that keeps the arm portion 6C in contact with the cam 8 at all times.

The cam 8 has a motor 23 and a reduction gear 24 (
(Fig. 2) in the counterclockwise direction, and the diameter increases continuously as the distance from the center increases from point P1 to point P2 to point P3 of the cam profile, such that r1<r2<r3. It has a cam shape that becomes

Therefore, as the cam 8 rotates and the cam profile contact portion with respect to the lever arm 6C moves from point P1 to point P2 to point P3, the swinging lever 6 resists the tension spring 7 and centers around the support shaft 6a. The cleaning roller 4a is sequentially rotated clockwise, and the pressure of the cleaning roller 4a against the surface of the fixing roller increases accordingly.

FIG. 2 is a block diagram of a rotational drive control circuit for the cam 8.

Reference numeral 21 denotes a main control circuit, and this circuit receives a recording stroke ratio signal from a recording material sensor 18 disposed near the recording material inlet side of the fixing device manually every time a recording material is introduced into the fixing device. .

The motor driver 22 is controlled by the circuit 21 to drive the motor 23 in response to each human power signal, and the cam 8 is sequentially rotated counterclockwise little by little via the reduction gear 24.

Along with this rotation, the lever 8 is sequentially rotated clockwise, and the pressing force of the cleaning roller 4a against the fixing roller 1 is strengthened.

In the above, the recording material sensor 18 and the circuit 21 are means for detecting the progress of usage of the fixing device over time (progress of device durability), and the circuits 21 and 22, the motor 23 including the deceleration device 24, and the cam 8, This is a control means for the cleaning member pressurizing means 6, 7, and 8 against the fixing roller 1.

(2) At the beginning of the durability of the device, the cam 8 is rotated at an angle at which the point 21 corresponding to the small diameter portion r1 of the cam profile is in contact with the lower surface of the arm 6C of the lever 6, as shown in FIG. As a result, the cleaning roller 4a is pressed against the surface of the fixing roller with a relatively light predetermined pressure.
They are held in contact with each other with a small nip width ml. In this case, the pressure contact force is set to a force sufficient to clean the surface of the fixing roller and apply the release agent at the initial stage of the apparatus.

■, As the durability of the device progresses, the cleaning roller 4
The arm portion 6C of the lever 6 may become dirty due to adhesion of collected toner, or the cam 8 may be rotated sequentially in the counterclockwise direction as described above as the durability of the device progresses. The cam profile portion that comes into contact with The pressure of the cleaning roller 4a against the surface of the fixing roller is automatically increased, and the contact nip width gradually increases as m1 → m2 → m3, so that the toner collected by the cleaning member The reduction in cleaning ability and release agent application ability due to contamination can be compensated for by successively increasing the pressure contact force as described above.

Therefore, the cleaning ability of the cleaning member and the ability to apply a release agent to the fixing roller 1 remain at the almost constant level required at the time of the initial setting from beginning to end over a long period of time, regardless of the progress of dirt on the cleaning member as the durability of the device progresses. As a result, image deterioration due to toner offset is prevented over a long period of time.

(2) However, as the toner contamination state of the cleaning roller 4a reaches a certain permissible limit as the durability of the device progresses, even if the pressure contact force of the cleaning roller 4a against the fixing roller 1 is further increased, the cleaning performance will be improved. It becomes impossible to maintain a predetermined level of molding agent application performance.

Therefore, in this embodiment, the detection means 20 such as an optical sensor is used to detect when the cam 8 has rotated to a predetermined rotation angle position where the pressure contact force of the cleaning roller 4a against the fixing roller 1 reaches a predetermined maximum value. (FIG. 4), the detection signal is fed back to the circuit 21 to activate the display/warning means 25, thereby prompting the operator to replace the cleaning roller 4a with a new one.

FIG. 5 shows a cleaning roller 4 as a cleaning member.
In place of a, an oblong rod-shaped cleaning pad 4b made of heat-resistant felt and impregnated with a release agent is shown.

In the case of this cleaning pad 4C, the nip width m4 hardly changes due to the increase in the pressure contact force, and the cleaning performance and release agent application performance are maintained over time only by the increase in the pressure contact force. The other configurations are the same as those of the previous example.

The above-mentioned leaning means structure can also be applied when the pressure roller 2 is provided with a cleaning means, and the fixing roller of a pressure roller type fixing device can fix an image by coming into contact with a member carrying an unfixed image. The present invention can be applied to a rotating body of a fixing device, including a rotating body (such as a roller body or a rotating endless belt body) that rotates.

The cleaning members 4a and 4c may not contain a mold release agent, and the mold release agent may be supplied by a means other than the cleaning member.

(Effects of the Invention) As described above, the fixing device of the present invention maintains the required cleaning ability of the cleaning means for the fixing rotor over a long period of time, regardless of the progress of the device durability, thereby preventing toner offset problems. It can prevent the occurrence of deterioration phenomena for a long period of time, and the intended purpose can be well achieved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view of an embodiment of the device. FIG. 2 is a block diagram of the control circuit. FIGS. 3 and 4 are state diagrams in which the pressing force of the cleaning roller against the fixing roller is increased as the durability of the apparatus progresses. FIG. 5 is a partial view of a device using a bat member as a cleaning member. 1 is a fixing roller, 2 is a pressure roller, 4a and 4C are rollers or bats as cleaning members, 6 is a swing lever, 7 is a tension spring, and 8 is a cam.

Claims (1)

[Claims] (1) A rotating body that fixes the image by contacting a member carrying an unfixed toner image; a cleaning member for the surface of the rotating body that contacts the surface of the rotating body; a pressurizing means that presses the cleaning member against the surface of the rotating body; and an apparatus. a means for detecting the progression of usage over time of the apparatus; and a means for detecting the progression of the usage over time of the apparatus, and a means for detecting the progress of the usage over time of the apparatus, which is detected by the detection means, in a direction in which the pressing force of the cleaning member against the surface of the rotating body is gradually strengthened in a predetermined direction. A fixing device comprising: means for controlling a pressure means.