JPH01201689A - Heat fixing device - Google Patents

Abstract

PURPOSE:To obtain an image of a high quality whose light transmissivity is uniform extending from the tip of the image to the rear end by making a rotating speed of a heat fixing roller lower than a steady speed when an OHP sheet passes through and also, decelerating its speed in accordance with passing of the OHP sheet. CONSTITUTION:When it is detected by a recording material detecting means 70 that a recording materials is an OHP (overprojector) sheet and also, it is detected by a tip detecting means 58 that the tip of the OHP sheet has reached a contact position between a pair of heat fixing rollers 42, 44 made of rubber, a rotating speed of the heat fixing rollers 42, 44 is decelerated in accordance with passing of the OHP sheet, and when it is detected by a rear end detecting means 58 that the rear end of the OHP sheet has reached the contact position between the rollers, the rotating speed of the heat fixing rollers 42, 44 is returned to a steady speed. Accordingly, a uniform heating value is provided extending from the tip of the OHP sheet to the rear end. In such a way, an image on the OHP sheet which has been fixed comes to have uniform light transmissivity extending from the tip to the rear end.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal fixing device that is advantageously used in a fixing device of a copying machine, particularly a full-color copying machine.

Conventionally, in a heat fixing device equipped with a slightly distorted heat fixing roller, in order to uniformly fix an image on a recording material and ensure gloss, it is necessary to It is necessary to apply a uniform amount of heat from the front end to the rear end. On the other hand, the surface temperature of the heat fixing roller decreases as the recording material passes, and if the rotational speed of the heat fixing roller, that is, the fixing speed is constant, a uniform amount of heat is applied from the leading edge to the trailing edge of the recording material. As a result, the fixing properties and glossiness vary between the leading and trailing edges of the image, making it impossible to obtain a uniform image.

Therefore, in conventional heat fixing devices, the heat fixing roller is made of Teflon, which has good thermal conductivity, and a temperature sensor is installed on the surface of the heat fixing roller to control the temperature of the heater, thereby controlling the amount of heat applied to the recording material. This prevents deterioration of fixing performance due to a drop in surface temperature by keeping it constant.

By the way, in a heat fixing device using such a heat fixing roller made of Teflon, if the toner adheres to the recording material in an uneven manner, the pressure force cannot be sufficiently absorbed during fixing, and as a result, the surface of the image after fixing is The toner particles may become uneven, or may not be sufficiently melted and toner particles may remain. Even if such a situation occurs, it is not a particular problem in the case of plain paper, but it causes a problem in the case of an OHP sheet (paper used for an over-projector) that requires translucency. That is, when such an OHP sheet having an uneven image surface after fixing is used for OHP, the light source is diffusely reflected when passing through the OHP sheet, making it impossible to obtain a clear projected image.

In order to solve this problem, a thermal fixing device using a rubber roller as a thermal fixing roller is used. In this prior art, a rubber roller is used as the heat fixing roller, so when fixing the OHP sheet, the elastic force can absorb the pressure, so the image after fixing is flat and has uniform translucency. Obtainable.

However, when such a rubber roller is used, its thermal conductivity is poor, making it extremely difficult to control the temperature using a temperature sensor. Therefore, the surface temperature decreases as the OHP sheet passes, and due to this, it is not possible to apply a constant amount of heat to the toner, and uniform translucency is maintained from the leading edge to the trailing edge of the image on the OHP sheet. can't get it.

Therefore, a thermal fixing device has been proposed in which the fixing speed and temperature are switched and applied to the recording material depending on the type of recording material, and the amount of heat applied to the toner is kept constant.

In such prior art, the fixing speed is simply switched depending on the case of OHP sheet and plain paper, and the fixing speed of the heat fixing roller as the OHP sheet passes through is simply changed. It is not possible to follow the decrease in surface temperature, and it is not possible to ensure uniform translucency from the leading edge to the trailing edge of the image.

An object of the present invention is to solve the above-mentioned technical problems and to ensure that when the recording material is an OHP sheet, the image on the OHP sheet after fixing has uniform translucency from the leading edge to the trailing edge. An object of the present invention is to provide a heat fixing device that can perform the following steps.

The present invention is equipped with a pair of rubber heat fixing rollers that are driven to rotate and whose outer peripheral surfaces are in line contact with each other, and toner is deposited between the pair of heat fixing rollers in a manner corresponding to the image. In a heat fixing device, in which a recording material passed through, the toner is melted and thermally fixed on the recording material during this passage, means for rotationally driving the heat fixing roller, and a contact between the heat fixing roller and the leading edge of the recording material. a leading end detecting means for detecting that the rear end of the recording material has reached the contact position; a trailing edge detecting means for detecting that the rear end of the recording material has reached the contact position; and a recording material detecting means for detecting that the recording material is an OHP sheet. Based on the detection results of the leading edge detecting means, the trailing edge detecting means, and the recording material detecting means, when the recording material is an OHP sheet and the leading edge of the OHP sheet reaches the contact position between the heat fixing rollers, the heat fixing roller is rotated. Controlling the heat fixing roller rotation drive means to reduce the speed as the OHP sheet passes, and return the rotation speed of the heat fixing roller to a steady speed when the rear end of the OHP sheet reaches a contact position between the heat fixing rollers. The invention is characterized by comprising a control means for controlling.

According to the above configuration, the recording material is detected by the recording material detection means.
) When it is detected that there is an HP receipt and the leading edge detection means detects that the leading edge of the OHP sheet has reached the contact position between the pair of rubber heat fixing rollers,
The rotation speed of the heat fixing roller is decelerated as the OHP sheet passes, and when the trailing edge detection means detects that the trailing edge of the OHP sheet has reached the contact position between the rollers, the rotation speed of the heat fixing roller is reduced to a steady speed. will be returned to.

As a result, a uniform amount of heat is applied from the leading edge to the trailing edge of the OHP sheet. Therefore, the fixed image on the OHP sheet has uniform translucency from the leading edge to the trailing edge.

JLJI FIG. 1 is a diagram schematically showing the internal structure of a full-color copying machine 1 according to an embodiment of the present invention. The original placed on the original glass 2 is CC-controlled by an exposure lamp 3 and a lens array 4.
The light is exposed to the D line sensor 5 and read as color signals of the three primary colors of R (red), G (green), and B (blue). This RGBO color signal is processed by the image processing circuit as Y(
Yellow) 2M (magenta), C (cyan), or Bk (black) added thereto is converted into a three-value or four-value signal, and is transmitted to the laser optical system 6 as an output signal. The copying machine of this embodiment does not have an image memory for three colors, and the image reader unit 7 scans each time when forming an image for each color, and based on this, sequentially Y, M, C or Y, M,
The C and Bk signals are transmitted to the laser optical system 6.

The laser optical system 6 includes a scanning polygon mirror 8, an Fθ lens 9, a reflection mirror 10, and the like.

Exposure is performed by irradiating the photosensitive drum 11 with image-forming laser light for each color based on the M, C, or Y, M, C, and Bk signals. The photosensitive drum 11 is rotationally driven in the direction of the arrow. The surface of the photosensitive drum 11 is provided with an organic photoreceptor formed into a laminated unit on a conductive substrate, and a photosensitive member exhibiting particularly high sensitivity near a laser emission wavelength of 780 nm is used.

Further, in this embodiment, the photosensitive drum 11 is negatively charged by a charger 12. A drum cleaner 13, a toner collection roll 14, an eraser lamp 15, and the charger 12 are arranged around the photosensitive drum 11, as well as four types of developing devices. The first developer 16 uses yellow toner, the second developer 17 uses magenta toner, the third developer 18 uses cyan toner, and the fourth developer 19 uses black toner. These toners are negatively charged. Further, toner replenishment is carried out by transporting the toner of each color stocked in the toner hopper 20 to each developing device 16, 17, 18, 19 via a pipe (not shown) at an appropriate time based on a replenishment signal.

Recording materials 56 such as plain paper and OHP sheets are stored in paper feed cassettes 21a and 21b in a stacked state, and are fed into the apparatus one by one by paper feed rollers 22a and 22b. Then, when the leading edge contacts the registration roller 23, the recording material 56 is temporarily stopped to determine the subsequent timing, and skew correction is performed at the same time.

24 is a paper sensor used for this purpose.

Reference numeral 25 denotes a transfer drum, which is driven to rotate in the direction of the arrow. A suction charger 2 is disposed inside the transfer drum 25 along the circumferential direction.
6, a transfer charger 27, and a separation charger 28 are arranged. Further, a transfer charger 29 is provided inside the photosensitive drum 11 facing the transfer charger 27, and a separation charger 30 is provided outside the transfer drum 25 facing the separation charger 28. .

The electrostatic latent image formed on the photosensitive drum 11 by exposure by the laser optical system 6 is developed as a toner image by one of the developing devices 16 to 19.

On the other hand, the recording material 56 fed from the registration roller 23 is
It is gripped by the glyph par 31 and is attracted onto the transfer drum 25 by the suction charger 26 as the transfer drum 25 rotates, and as the transfer drum 25 rotates, the transfer drum 2
It can be wrapped around 5.

Then, while the recording material 56 passes between the transfer chargers 27 and 29, the toner image on the photosensitive drum 11 is transferred to the recording material 56. Note that in the full color mode, the recording material 56 is rotated four times by the transfer drum 25. After the transfer process has been completed, the recording material 56 is neutralized by the separation charger 28 , 30 , separated from the transfer drum 25 by the separation claw 32 , and fed to the thermal fixing device 40 by the conveyance belt 33 .

The transferred recording material 56 is heated and pressurized by passing through the thermal fixing device 40 , the image is fixed on the recording material 56 , and the image is discharged onto the paper discharge tray 35 .

FIG. 2 is a sectional view showing a specific configuration of the heat fixing device 40. As shown in FIG. The thermal fixing device 40 includes a thermal fixing roller 42 having a heating heater 41 therein, a thermal fixing roller 44 having an internal heating heater 43 and being pressed against the thermal fixing roller 42.
It has an oil application roller 45 that comes into pressure contact with the heat fixing roller 44 and applies silicone oil for mold release to the outer peripheral surface of the heat fixing roller 44 . The rotational shafts of the thermal fixing roller 42 and the thermal fixing roller 44 are connected via a power transmission means such as a gear, so that the rotation of the thermal fixing roller 42 in the direction of the arrow causes the thermal fixing roller 44 to move in the direction of the arrow. Rotate to. Furthermore, the rotation of the heat fixing roller 44 causes the oil application roller 45 to rotate in the direction of the arrow.

The heat fixing roller 42 includes a silicone rubber layer 46 and a Teflon layer 47 covering the outer peripheral surface of the silicone rubber layer 46.
and has. A temperature detector 48 is provided on the Teflon layer 47 for slidingly contacting the fixing roller 42 and detecting its surface temperature. Further, the heat fixing roller 44 has a core metal 49
and a silicone rubber layer 5 covering the outer peripheral surface of this core bar 49.
0. A temperature detector 5 is provided on the silicone rubber layer 50 for slidingly contacting the heat fixing roller 44 and detecting its surface temperature.
1 is provided. The thickness of the silicone rubber layer 50 is selected to be thinner than the thickness of the silicone rubber layer 46.

The reason why the Teflon layer 47 is coated on the outer peripheral surface of the heat fixing roller 42 is that if the Teflon layer 47 was not provided,
This is because the silicone oil for mold release permeates into the silicone rubber layer 46 and the silicone rubber layer 46 becomes soggy, making it impossible to apply an appropriate pressing force.

The oil application roller 45 is made of a single layer of silicone rubber 51, and on its surface is an impregnated member 52 made of felt or the like.
The other end of the impregnated member 52 is immersed in a silicone oil storage tank 53. The impregnation member 52 is held by a holding member 54. When the heat fixing roller 44 is rotationally driven in the direction of the arrow and the oil application roller 45 is accordingly rotated in the direction of the arrow, the storage tank 5
The silicone oil in the heat fixing roller 44 is applied to the surface of the heat fixing roller 44 by the rotation of the oil application roller 45.

A guide plate 57 is provided on the entrance side of the heat fixing rollers 42 and 44 to guide the recording material 56 to which the toner 55 is attached. Further, near the contact position P between the heat fixing rollers 42 and 44, there is a leading edge/
A trailing edge detector 58 is provided. The leading/trailing detector 58 may be an optical detector or a mechanical switch such as a limit switch. Also,
Separation claws 59 and 60 are provided on the exit sides of the heat fixing rollers 42 and 44.
is provided.

The heat fixing roller 42 is rotationally driven in the direction of the arrow by a driving force supply means 61 realized by a motor or the like.

This driving force supply means 61 is controlled by a drive control circuit 62, and for example, voltage control is performed. Drive control circuit 6
2 is supplied with detection signals from a recording material detection means 70 for detecting that the recording material 56 is an OHP sheet, a full color mode designation detection means 63, and a leading edge/trailing edge detector 58. The recording material detection means 70 is composed of, for example, a light emitting element and a light receiving element, and detects that the sheet is an OHP sheet by the light emitted from the light emitting element passing through the OHP sheet and being received by the light receiving element. do. Note that the recording material detection means 70 may be provided at any location on the conveyance path before reaching the heat fixing rollers 42, 44, and in particular, in consideration of ease of detection, the recording material detection means 70 may be provided at any location on the conveyance path before reaching the heat fixing rollers 42, 44. It is desirable to provide a Further, temperature detection signals from the temperature detectors 48 and 51 are applied to a temperature control circuit 64, and from this temperature control circuit 64 a drive control signal for the heat fixing roller 42 is applied to a drive control circuit 62.

The heaters 41 and 43 are, for example, halogen lamps, and are energized by a power supply means 65.

FIG. 3 is a flowchart showing the heat fixing processing operation of the heat fixing device 40. First, in step n1, it is determined whether the full color mode designation detection means 63 has detected the full color mode. That is, when copying the recording material 56, the operator operates a mode designation key to determine whether full-color development or monochrome development is to be performed. for example,
When the multicolor development mode key is operated, the full color mode designation detection means 63 detects this and provides a detection signal to the drive control circuit 62. This allows step n1
Then, the process moves to step n2. In step n2, the recording material 5-
It is determined whether or not 6 is an OHP sheet. When the recording material detection means 70 detects that it is an OHP sheet, the process moves to step n3, and the drive control circuit 62 sets the first deceleration pattern mode shown in FIG. 4(1).

Next, the process moves to step n4, where O
It is determined whether the leading edge of the HP sheet has been detected by the leading/trailing edge detector 58. Immediately before the leading edge of the recording material 56 reaches the contact position P between the rollers 42 and 44, the detector 58
When detected, a detection signal from the detector 58 is output to the drive control circuit 62. As a result, the process moves to step n5, and the drive control circuit 62 executes the first deceleration pattern.

Incidentally, as shown in FIG. 4(1), before the time t1 when the OHP sheet reaches the contact position P, the heat fixing roller 42
．． 43 is driven in steady rotation at a circumferential speed of ■l. This peripheral speed corresponds to the fixing speed of the recording material, and the speed 1 is equal to the process speed (corresponding to the peripheral speed of the photoreceptor 11).

At time t1 when the OHP sheet reaches the contact position P, the drive control circuit 62 sets the fixing speed to a speed ■ smaller than the speed V1.
The voltage of the driving force supply section 61 is controlled so that the voltage becomes 2.

When the OHP sheet begins to pass between the heat fixing rollers 42 and 44, the drive control circuit 62 controls the voltage to the drive force supply section 61 so that the fixing speed is linearly decelerated from 2. As a result, as the OHP sheet passes the contact position P, the fixing speed is reduced as shown by line 11. Therefore, the surface temperature of the heat fixing rollers 42 and 44 is O.
Even if it decreases as the HP sheet passes, the fixing speed is decelerated, so that a uniform amount of heat is applied from the leading edge to the trailing edge of the OHP sheet. Therefore, OHP
The toner on the sheet is completely melted and fixed, and even if the toner is uneven when passing between the rubber heat fixing rollers 42 and 44, the pressing force is absorbed by the elastic force, so that the toner is not fixed. The surface of the image becomes flat. Therefore, the fixed image has uniform translucency from the leading edge to the trailing edge.

While the OHP sheet is passing through the contact position P in this way, whether or not the rear end of the OHP sheet has reached the contact position P, that is, whether the rear end of the OHP sheet has been detected by the detector 58. is determined in step n6. O
When the rear end of the HP sheet is detected by the detector 58, the process moves to step n7, and at time t2 when the OHP sheet reaches the contact position P, the fixing speed is returned from ■3 to the original steady speed ■1. Thereafter, the heat fixing rollers 42 and 44 are rotated at a fixing speed of 1. Recording material 56
When the sheet is an OHP sheet and the image is in full color mode, the fixing process is performed using the first deceleration pattern.

When the monochrome development mode is specified in step n1, the process moves to step n8, where it is determined whether the recording material 56 is an OHP sheet.

If it is an OHP sheet, the process moves to step n9, and the fourth
A second deceleration pattern shown in FIG. (2) is set. Then, in step nlO, it is determined whether the leading edge of the OHP sheet subjected to monochrome development is detected by the detector 58,
When detected, the second deceleration pattern shown in FIG. 4(2) is executed at step nil. In this second deceleration pattern, from time t3 when the OHP sheet reaches the contact position P, the fixing speed is decelerated linearly from 1 to 12 as shown by line 12. When the rear end of the OHP sheet is detected by the detector 58 in step n12, the process moves to step n13 and the fixing speed is returned from (4) to (1).

In this way, even when the recording material 56 is an OHP sheet and monochrome development is performed, by decelerating the fixing speed as the OHP sheet passes, uniform translucency can be ensured even in a monochrome image.In step n2, the recording material 56 If the sheet is not an OHP sheet, for example, if it is plain paper, the process moves to step n14, and the fixing process is executed at the normal fixing speed without reducing the fixing speed. Further, even if the recording material 56 is, for example, plain paper in step n8, the process similarly moves to step n15 and the fixing process is executed at the normal fixing speed.

Although it is assumed that fixing is performed at the normal speed in step n14, since it is a full color mode, the fixing speed may be slowed down, and this can be done by performing the processing in steps n9 to n13 instead of the processing in step n14. .

In this way, when it is an OHP sheet and the amount of toner adhesion is large, fixing is performed using the first deceleration pattern, and when it is an OHP sheet and the amount of toner adhesion is small, such as a single color, the fixing is performed using the second deceleration pattern.・Since this is done, optimal fixing can be achieved in any case.

Furthermore, in the above-mentioned embodiment, fixing was carried out using the second deceleration pattern for an OHP sheet in the case of a monochromatic image, but in the case of a multi-color image in which toner does not overlap, fixing was performed using the second deceleration pattern. In the case of an image in which toner overlaps even in two-color development, fixing may be performed using the first deceleration pattern.

In the above embodiment, after determining whether the mode is full color mode, it is determined whether or not the sheet is an OHP sheet, and fixing is performed at a steady speed or deceleration. It is also possible to perform deceleration and fixation only by determining whether or not this is the case.

Further, in the above-mentioned embodiment, the OHP sheet is attached to the heat fixing roller 4.
Although it was designed to decelerate according to a predetermined deceleration pattern as it passes between 2.44 and 48.5,
Thermal fixing rollers 42 and 44 based on the temperature detection signal from 1
The rotation speed may be controlled.

Further, in the above embodiment, the leading edge and trailing edge of the OHP sheet are detected by the detector 58, but two detectors are provided, and the leading edge detector is connected to the heat fixing roller 42.
4, and the rear end detector may be provided on the discharge side. Further, the tip/back end detector 58 is at the contact position P.
Although it is provided nearby, it may be provided at any location on the conveyance path before reaching the heat fixing device 40.
In this case, a timer may be used to detect when the leading and trailing ends of the recording material 56 reach the contact position P.

Furthermore, in addition to the first and second deceleration patterns, a plurality of deceleration patterns may be set in advance, and the most suitable deceleration pattern may be selected and fixed depending on the amount of toner applied to the OHP sheet. good.

Note that in this embodiment, the fixing speed is not reduced for recording materials other than OHP sheets, so it is possible to improve the efficiency of the fixing process. That is, if the fixing speed is reduced even for plain paper, the fixing processing speed will be reduced. On the other hand, plain paper does not receive a uniform amount of heat, and even if toner particles remain in the image after fixing, OHP
Unlike sheets, translucency is not an issue, so there are no particular inconveniences. Therefore, in this embodiment, in order to improve the fixing processing speed, the fixing speed of only the OHP sheet is reduced to improve the efficiency of the fixing processing.

Although the thermal fixing device according to the present invention was used in a full-color copying machine in the above embodiment, the present invention can also be suitably implemented in a fixing device of a copying machine that performs ordinary monochrome development. Further, the fixing device according to the present invention can be applied not only to copying machines but also to other toner transfer type image forming apparatuses.

As described above, according to the present invention, when an OHP sheet passes between a pair of heat fixing rollers, the rotation speed of the heat fixing roller is slower than the steady speed, and furthermore, it decelerates as the OHP sheet passes. Therefore, even though the surface temperature of the heat fixing roller decreases as the OHP sheet passes, the OHP
A uniform amount of heat can be applied from the leading edge to the trailing edge of the image on the P sheet. Therefore, a high quality image with uniform light transmission from the leading edge to the trailing edge of the image can be formed on the OHP sheet.

[Brief explanation of the drawing]

FIG. 1 is a simplified diagram showing the internal structure of a full-color copying machine 1 according to an embodiment of the present invention, FIG. 2 is a sectional view showing a specific configuration of a thermal fixing device 40, and FIG. FIG. 4 is a flowchart showing the fixing processing operation of the fixing device 40.
3 is a graph showing changes in fixing speed. 40... Heat fixing device, 41.43... Heater, 42
゜44... Heat fixing roller, 55... Toner, 56...
...Recording material, 58...Top/rear end detector, 61...
Driving force supply unit, 62... Drive control circuit, 70... Recording material detection means, P... Contact position between heat fixing rollers. Patent applicant: Minolta Camera Co., Ltd. Figure 1/

Claims (1)

[Claims] (1) A pair of rubber heat fixing rollers are rotatably driven and their outer peripheral surfaces are in line contact with each other, and a recording material to which toner is attached in accordance with the image passes between the pair of heat fixing rollers.
In a heat fixing device in which the toner is melted and thermally fixed on the recording material during this passage, means for rotationally driving the heat fixing roller and detecting that the leading edge of the recording material has reached a contact position between the heat fixing rollers. a leading end detecting means for detecting that the trailing end of the recording material has reached the contact position; a recording material detecting means for detecting that the recording material is an OHP sheet; Based on the detection results of the edge detection means and the recording material detection means, when the recording material is an OHP sheet and the leading edge of the OHP sheet reaches the contact position between the heat fixing rollers, the rotational speed of the heat fixing roller is adjusted according to the passage of the OHP sheet. control means for controlling the heat fixing roller rotation drive means to reduce the speed and return the rotation speed of the heat fixing roller to a steady speed when the rear end of the OHP sheet reaches a contact position between the heat fixing rollers; A heat fixing device characterized by: