JPS6332384B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a heat fixing device in an electrophotographic copying machine that heats and fixes a toner image on copy paper by guiding it to a fixing roller. BACKGROUND ART In some prior art, when an electrostatographic copying machine is powered on, a fixing roller is driven to rotate at a relatively high speed suitable for fixing. In such prior art, before the power is turned on, toner remains and solidifies on the fixing roller from the previous copying operation, and this toner causes the pair of fixing rollers to adhere to each other. There is. By rotating the fixing roller at the same time as the power is turned on, the fixing roller is driven before the fixing roller reaches the softening temperature or melting temperature of the toner. Therefore, the toner that has adhered to and solidified on the fixing roller damages the roller. In order to remove the toner on the fixing roller and prevent the copy paper from wrapping around the fixing roller, there is a heat fixing device that is equipped with a peeling plate that comes into sliding contact with the surface of the fixing roller. By the time the toner that has adhered and solidified across the roller surface and peeling plate softens and melts, the fixing roller is driven to rotate, so the peeling plate rotates together with the fixing roller, and the peeling plate and fixing roller are rotated. The angle with the surface will deviate from the proper angle, and the peeling plate and fixing roller will be damaged. Additionally, if the toner that has solidified on the surface of the fixing roller adheres to the peeling plate, an abnormal sound may occur when the fixing roller starts rotating.
Also, while the fixing roller is rotating, the toner on the surface of the fixing roller hits the peeling plate, causing abnormal noise. Since the fixing roller rotates at a relatively high speed suitable for fixing, it is noisy. In other prior art, after the electrophotographic copying machine is powered on, the fixing roller is rotated at a relatively high speed suitable for fixing only after the surface of the fixing roller reaches a temperature suitable for fixing. In such prior art, once the fusing roller is heated to a temperature suitable for fusing, the fusing roller continues to be rotated at a relatively high speed suitable for fusing, which may cause damage to the fusing roller. Also, the noise is loud. Moreover, when fusing is performed immediately after the fusing roller reaches a temperature suitable for fusing and starts rotating, the temperature fluctuations on the fusing roller surface are not sufficiently eliminated by the rotation of the fusing roller. It is not possible to obtain a perfect fixing state over the entire surface of the copy paper, resulting in uneven fixing quality. Furthermore, since the fixing roller remains stationary until it reaches a temperature suitable for fixing, the fixing roller is deformed by the pressure force between the fixing rollers. Problems to be Solved by the Invention The main object of the present invention is to provide a heat fixing device for an electrophotographic copying machine that prevents damage caused by toner adhering to the fixing roller and provides good fixing performance. It is. Embodiment FIG. 1 is a simplified side view of an embodiment of the present invention, and FIG. 2 is a perspective view of a portion thereof. The heat fixing device 1 can be pulled out from the body of the electrophotographic copying machine to the side (to the back side of the paper in FIG. 1). FIG. 3 is a developed cross-sectional view taken along a cut plane including the axes of the fixing rollers 3 and 4. FIG. A frame 2 of the heat fixing device 1 is provided with a pair of fixing rollers 3 and 4 that are parallel to each other and have horizontal axes. The fixing roller 3 is rotatably supported on the frame 2 of the heat fixing device 1. A heater 5 is inserted into the fixing roller 3 . The other fixing roller 4 is pivotally supported by a lever 6. One end of the lever 6 is pivoted to the frame 2 by a pin 8, and the other end of the lever 6 is
The fixing roller 4 is biased by the spring 9 so as to come into pressure contact with the fixing roller 3. The transport path of the copy paper is indicated by reference numeral 1 in Fig. 1.
Indicated by 0. The copy paper is guided in the direction of arrow 11 to a pair of fixing rollers 3 and 4. This fixing roller 3,
A toner image corresponding to the original document is formed on the copy paper that is led between the four paper sheets. A peeling plate 12 is provided on the downstream side of the fixing roller 3 for removing toner adhering to the fixing roller 3 and peeling off copy paper wrapped around the fixing roller 3. A sprocket wheel 14 is fixed to one end of the fixing roller 3. A rotating shaft 15 is pivotally supported on the frame 2 in parallel with the fixing rollers 3 and 4, and a sprocket wheel 16 is fixed to this rotating shaft 15. A chain 17 is wound around the sprocket wheels 14 and 16. Associated with this chain 17 is a sprocket wheel 18 for tensioning the chain 17. A rotary shaft 20 is rotatably supported on the body of the electrophotographic copying machine by a bearing 19.
A sprocket wheel 21 is provided integrally with the sprocket wheel 0. A sprocket wheel 23 is fitted onto the rotating shaft 20 via a one-way clutch 22. A chain 24 is wound around this sprocket wheel 23. This chain 24 is driven by a main drive means 25 including a motor. One-way clutch 22 transmits rotational force in the direction of arrow 26 from chain 24 to rotating shaft 20. The running direction 26 of this chain 24 corresponds to the rotational direction 27 of the fixing roller 3, and thereby the copy paper is transported in the direction of arrow 11. A one-way clutch 30 is provided between the rotating shafts 15 and 20.
is interposed, and this one-way clutch 30 transmits rotational force from the rotation shaft 20 rotating in the rotation direction 28 to the rotation shaft 15. The rotating shaft 15 is connected to the heating fixing device 1
one-way clutch 30 when the is pulled out of the aircraft.
The shaft 15 is fitted into the one-way clutch 30 when the heat fixing device 1 is disengaged from the one-way clutch 30 and the heat fixing device 1 is mounted on the machine body. A sprocket wheel 33 is pivotally supported on the fuselage. A chain 34 is wound between the sprocket wheel 33 and the sprocket wheel 21. A gear 32, which is integral with the sprocket wheel 33, meshes with a gear 37 that is loosely fitted to the output shaft 36 of the low-speed drive means 35. An electromagnetic clutch 38 is provided between the gear 37 and the low speed drive means 35. The low speed drive means 35 consists of a motor 39 and a reduction gear train 40 connected to the motor 39. FIG. 4 is an electrical circuit diagram of one embodiment of the present invention. The heater 5 built into the fixing roller 3 is connected to the power source 4.
2 and a temperature control circuit 43. A temperature detection element 44 such as a thermistor is brought into contact with the surface of the fixing roller 3, and the surface temperature of the fixing roller 3 is detected. The temperature control circuit 43 includes a temperature detection element 44
In response to the output from
The energizing power of the heater 5 is controlled so that the temperature is kept constant (180°C). One output line l1 of the temperature control circuit 43 is at a low level when the surface temperature of the fixing roller 3 detected by the temperature detection element 44 is lower than a set temperature (for example, 100° C.), and is at a low level of 100° C.
It is at a high level above ℃. The other output line l2 of the temperature control circuit 43 is connected to the temperature detection element 4.
The surface temperature of the fixing roller 3 detected by 4 is
It is low level below 180°C and high level below 180°C. As mentioned above, for example, the set temperature is 100℃.
At least a temperature at which the toner solidified at room temperature softens when heated, and at a temperature suitable for fixing (for example, 180°C as mentioned above)
During the period when the temperature is raised to a temperature suitable for fixing, the fixing rollers 3 and 4 rotate at a low speed as described later, so that temperature unevenness on the surface of the fixing rollers 3 and 4 is eliminated. It is determined within the temperature range. Therefore, during the period after the surface temperature of the fixing roller 3 reaches the set temperature until it reaches a temperature suitable for fixing that is higher than the set temperature (for example, 180° C. as described above), the fixing rollers 3 and 4 Since the fixing rollers 3 and 4 are driven to rotate at a low speed, the surface temperature distribution of the fixing rollers 3 and 4 becomes uniform in the circumferential direction, eliminating temperature unevenness, and thereby the surface temperature of the fixing roller 3 reaches a temperature suitable for fixing. Even if the fixing operation is performed immediately after the fixing operation, good fixing performance can be achieved.

[Table] Table 1 shows how the main drive means 2 changes in surface temperature of the fixing roller 3 in the embodiments shown in FIGS. 1 to 4.
5. The operating state of the low-speed drive means 35 and the electromagnetic clutch 38 is shown. "ON" of the main drive means 25 and the low speed drive means 35 indicates an activated state,
"OFF" indicates a disabled state. "ON" of the electromagnetic clutch 38 indicates the connected state, "OFF"
indicates a blocked state. Next, the operation will be explained. When the electrophotographic copying machine is powered on, the temperature control circuit 43 energizes the heater 5 . During the period when the surface temperature of the fixing roller 3 is between the room temperature and the set temperature of 100° C., the output line l1 is at a low level, and therefore the output of the AND gate 45 is at a low level. The drive circuit 46 is then disabled,
The electromagnetic clutch 38 is demagnetized and disconnected. Further, the output line l2 of the temperature control circuit 43 is at a low level, so the output of the AND gate 47 is at a low level, so the drive circuit 48 is disabled and the main drive means 25 is disabled. ing. In this way, the fixing rollers 3 and 4 remain stationary. When the surface temperature of the fixing roller 3 reaches 100℃ or higher,
In response to the output from temperature detection element 44, temperature control circuit 43 derives a high level signal on its output line l1. On the other hand, the output line l2 remains at a low level, so the AND gate 47
The output of this AND gate 4 is low level.
The output of 7 is inverted by an inverting circuit 49. Therefore, the input signal from the delay circuit 52 consisting of the series resistor 50 and the parallel capacitor 51 to the AND gate 45 remains at a high level. Therefore
The output of AND gate 45 goes high, thereby activating drive circuit 46 and energizing electromagnetic clutch 38. Therefore, the electromagnetic clutch 3
8 is in a connected state. Referring to FIG. 3, the rotational force from the low-speed drive means 35 is transmitted from the output shaft 36 to the electromagnetic clutch 38, gears 37, 32, sprocket wheel 33, chain 34, sprocket wheel 21, rotating shaft 20, one direction The power is transmitted to the clutch 30, rotating shaft 15, sprocket wheel 16, chain 17 and sprocket wheel 14 in this order, and the fixing roller 3 is rotationally driven in the direction of arrow 27. The rotation speed of the fixing roller 3 by this low-speed drive circuit 35 is lower than the speed suitable for fixing. The heater 5 is further energized and the fixing roller 3
When the temperature reaches a temperature suitable for fixing (ie, for example, 180° C. as described above), the temperature control circuit 43 controls the heater 5 to be powered so as to maintain the fixing temperature. Therefore, the surface temperature of the fixing roller 3 is always maintained at 180°C. Assume that a copying operation is performed when the surface of the fixing roller 3 is maintained at 180°C. At this time, the print button 53 is pressed to make a copy. Therefore, the flip-flop 54 is set, and its high level set output is set.
is applied to AND gate 47. Temperature control circuit 4
Since the surface temperature of the fixing roller 3 is 180° C., the output line l2 from the fixing roller 3 is at a high level. Therefore, the output of the AND gate 47 becomes high level, so that the drive circuit 48 is activated and the main drive means 25 is activated. Its main drive means 25
The power from the chain 24 passes through the sprocket wheel 23, the one-way clutch 22, the rotating shaft 20, the one-way clutch 30, the rotating shaft 15, the sprocket wheel 16, the chain 17, and the sprocket wheel 14, and then the fixing roller 3. is transmitted to.
In this way, the fixing roller 3 is driven to rotate at a relatively high speed suitable for fixing. The rotational force from this rotating shaft 20 is also applied to the sprocket wheel 21, chain 34, and sprocket 3.
3. Transmitted to gears 32 and 37. At this time, the electromagnetic clutch 38 is in a disconnected state. To describe this operation, in FIG. 4, when the print button 53 is pressed, the output of the AND gate 47 rises from a low level to a high level and becomes a high level. The rising output from the AND gate 47 is given to the inverting circuit 49, and the output from the inverting circuit 49 becomes a falling signal from high level to low level. This falling signal is sent to the delay circuit 5.
This is the forward current of the diode 55 which is provided in parallel with the current. Therefore, the falling waveform and the subsequent low level signal are applied from the inverting circuit 49 to the AND gate 45 via the diode 55. In other words, the low level signal from the inverting circuit 49 is applied to the AND signal regardless of the operation of the delay circuit 52.
is applied to gate 45. Therefore, when the print button 53 is pressed, the AND gate 45
It immediately goes to low level, and therefore the drive circuit 4
6 is disabled, and the electromagnetic clutch 38 is placed in a disconnected state. During the copying operation, the copy paper on which the toner image has been formed is guided to fixing rollers 3 and 4, where it is heated and fixed, and is discharged from the body of the electrophotographic copying machine.
The discharge of the copy paper after copying is completed to the outside of the machine is detected by the copy end signal generating means 56, and the copy end signal generating means 56 derives a high-level pulsed copy end signal. Therefore, flip-flop 54 is reset, and the output from flip-flop 54 to AND gate 47 becomes low level. As a result, drive circuit 48 and main drive means 25 are disabled. AND gate 47
A low level output from the inverting circuit 49 is provided to the inverting circuit 49. an inverting circuit 4 that receives a falling output from a high level to a low level from an AND gate 47 caused by an output from the copy end signal generating means 56;
9 derives a rising signal from low level to high level. This rising signal is connected to diode 5
5 reverse current. Therefore, the inverting circuit 49
A high level signal is applied from the delay circuit 52 to the AND gate 45 after a delay time T1 by the delay circuit 52 has elapsed after the output from the AND gate 45 rises. However, the output line l1 applied to the AND gate 45 is at a high level. Therefore
The output of the AND gate 45 becomes high level, and the electromagnetic clutch 38 is excited by the drive circuit 46 and becomes connected. In this way, the main drive means 2
After the electromagnetic clutch 5 stops, the electromagnetic clutch 38 becomes connected after a delay time T1 determined by the delay circuit 52 has elapsed. As a result, the power from the low-speed drive circuit 35 is transmitted to the fixing roller 3, and the fixing roller 3 is driven at a low speed. The reason for setting the delay time T1 is as follows. Immediately after the main drive means 25 is disabled, the chain 24 is running due to inertia.
Sprocket wheel 23 is rotating due to inertia. If it is assumed that the electromagnetic clutch 38 changes from the disconnected state to the connected state at the same time that the main drive means 25 is disabled, the large rotational force of the main drive means 25 at a relatively high speed will be applied at a relatively low speed. The signal is transmitted to the rotating output shaft 36. The direction of the rotational force transmitted to the output shaft 36 coincides with the rotational direction of the low-speed drive means 35. This output shaft 36
In order to rotate the motor at a speed higher than that of the motor 39, the reduction gear train 40 is connected to the output shaft 36.
and motor 39, and the relatively large capacity of motor 39, a large rotational force is required. In other words, the main drive means 25 is disabled and the electromagnetic clutch 38 is simultaneously disabled.
If this happens, a large load will be placed on the power transmission path from the main drive means 25 to the motor 39. Therefore, by setting the delay time T1, the electromagnetic clutch 38 is brought into the connected state only when the rotation due to inertia has weakened after the main drive means 25 is disabled.
This prevents an excessive load from being applied to the power transmission path from the main drive means 25 to the motor 39. In another embodiment of the invention, motor 39 may be disabled upon disconnection of electromagnetic clutch 38. FIG. 5 is a developed sectional view corresponding to FIG. 3 of another embodiment of the present invention. What is noteworthy in this embodiment is that the electromagnetic clutch 38 mentioned above is removed and a one-way clutch 57 is provided between the output shaft 36 of the low speed drive means 35 and the gear 37. Furthermore, in this embodiment, the motor 39 of the low-speed drive means 35 is connected in place of the electromagnetic clutch 38 in the electric circuit of FIG. 45
give directly to The rest of the structure is similar to the previous embodiment, and the operation is as shown in Table 2. In this embodiment, when the surface temperature of the fixing roller 3 is maintained at 180°C,
Motor 39 may be energized during copying operations.

[Table] According to the idea of the present invention, the main drive means 25 is
It is sufficient that it is activated only during the fixing operation during the copying operation. The reduction gear train 40 may be interposed between the electromagnetic clutch 38 or the one-way clutch 57 and the sprocket wheel 21. Effects As described above, according to the present invention, the rotation state of the fixing roller starts at a temperature lower than the temperature suitable for fixing and higher than room temperature, so that the toner on the fixing roller has a large adhesion force. Since the toner is not attached to the fixing roller, and the toner is only attached to the fixing roller with a relatively small adhesive force, there is no excessive force acting on the fixing rollers, and the toner is not attached to the fixing roller. Relatedly, there is no risk of damage to the peeling plate for peeling off the copy paper. This prevents damage to the fusing roller, etc.
Also, generation of abnormal sounds is prevented. This eliminates temperature unevenness on the surface of the fusing roller, achieving high-quality fusing over the entire surface of the copy paper, preventing deformation of the fusing roller, and rotating at a relatively high temperature suitable for fusing. The generation of large noise caused by noise can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a side view of one embodiment of the present invention, FIG. 2 is a simplified exploded perspective view of a part of the part shown in FIG. 3, and FIG. 4 is an electrical circuit diagram relating to the main drive means 25 and electromagnetic clutch 38, and FIG. 5 is an exploded sectional view of another embodiment of the present invention. 1... Heat fixing device, 3, 4... Fixing roller, 5...
Heater, 12... Peeling plate, 22, 30, 57... One-way clutch, 25... Main drive means, 35... Low speed drive means, 38... Electromagnetic clutch, 39... Motor, 4
0... Reduction gear train, 44... Temperature detection element, 52... Delay circuit, 53... Print button.

Claims (1)

[Scope of Claims] 1. A heat fixing device for electrophotographic copy paper in which a copy paper having a toner image on its surface is guided to a fixing roller having a temperature suitable for fixing (fixing temperature) and fixed, the fixing roller comprising: The roller takes a stationary state or a rotating state depending on the temperature, and the rotating state is determined by a signal from a temperature detection element that detects the surface temperature of the fixing roller, at a temperature lower than the temperature suitable for fusing and higher than room temperature. A heat fixing device characterized by starting at . 2. The roller rotation start temperature is at least higher than the temperature at which the toner solidified at room temperature is softened by heating, and the rotation of the fixing roller does not occur during the period during which the temperature rises to a temperature suitable for fixing. 2. The heat fixing device according to claim 1, wherein the heat fixing device is determined within a temperature range in which there is no unevenness in the surface temperature of the fixing roller. 3. The heat fixing device according to claim 1, wherein the roller rotation start temperature is set in a range of 100 to 180°C. 4. The heat fixing device according to claim 1, wherein the rotation state is at a temperature suitable for fixing and at a speed lower than the speed. 5. The heat fixing device according to claim 1, wherein the speed rotation state suitable for fixing is achieved only when the surface temperature of the fixing roller is at a temperature suitable for fixing and during a copying operation. 6. A main drive means for driving the fixing roller at a speed suitable for fixing; a one-way clutch interposed between the main drive means and the fixing roller and transmitting rotational force from the main drive means to the fixing roller; In response to the output from the temperature detection element, when the surface temperature of the fixing roller is (a) below the roller rotation start temperature, the main driving means is disabled and the electromagnetic clutch is cut off; (b) ) When the temperature is within the temperature range from the roller rotation start temperature to a temperature suitable for fusing, the main driving means is disabled, the low speed driving means is activated, and the electromagnetic clutch is connected, and (c) the temperature is suitable for fusing. temperature, the main drive means is activated and the electromagnetic clutch is in the disconnected state during fusing, and the main drive means is disabled, the low speed drive means is activated, and the electromagnetic clutch is in the connected state at times other than during fusing. 2. A heat fixing device for an electrophotographic copying machine according to claim 1, further comprising a control means for controlling an electrophotographic copying machine. 7. Claim 6, wherein the low-speed drive means includes: a motor; and a reduction gear train interposed between the motor and an electromagnetic clutch or between the electromagnetic clutch and a fixing roller.
A heat fixing device for an electrophotographic copying machine as described in 2. 8. A patent characterized in that the control means brings the electromagnetic clutch into the connected state immediately after the activated main drive means is disabled and after a period of time has elapsed in which the inertia of the main drive means has weakened. A heat fixing device for an electrophotographic copying machine according to claim 6. 9 a main drive means for driving the fixing roller at a speed suitable for fixing; a first drive means interposed between the main drive means and the fixing roller and transmitting rotational force from the main drive means to the fixing roller;
a one-way clutch; a low-speed drive means for driving the fixing roller at a low speed lower than a speed suitable for fusing; a second one-way clutch for transmitting rotational power from the low-speed drive means to the fixing roller; and the temperature detection element. When the surface temperature of the fixing roller is (a) below the roller rotation start temperature, the main drive means and the low speed drive means are disabled; (c) when the temperature is within a suitable temperature range, the main drive means is disabled and the low speed drive means is enabled; (c) when the temperature is suitable for fusing, the main drive means is disabled and the low speed drive means is enabled during fusing; 2. The heat fixing device for an electrophotographic copying machine according to claim 1, further comprising a control means for activating the heat fixing device.