JP7206820B2 - Fixing device and image forming apparatus provided with the fixing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image transferred to a recording medium onto the recording medium by thermocompression, and an image forming apparatus equipped with the fixing device.

An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred to a recording medium such as paper. A fixing device generally includes a belt-shaped fixing member that is heated by a heating member, and a pressure member that is arranged opposite to the fixing member. The toner image is fixed on the recording medium by heating and pressing (thermocompression). In a fixing device that fixes a toner image to a recording medium by such thermal compression, it is necessary to maintain the temperature of the fixing member at a control temperature suitable for thermal fixing. However, the temperature of the fixing member at the nip portion cannot be directly detected. For this reason, for example, in a fixing device disclosed in Patent Document 1 below, the temperature of a heating member that heats the fixing member is detected, and power supplied to the heating member is controlled based on the detected value.

By the way, when the heating member is in a heat storage state, even if the temperature of the fixing member drops due to the passage of paper, the change in the temperature of the heating member during passage of the paper is small, so the supplied electric power becomes small, and the fixing performance deteriorates. be. Therefore, the fixing device described above is provided with an end temperature detector for detecting the temperature of the end portion of the heating member in the longitudinal direction. When it is inside, it is determined that the heating member is in the heat storage state, and the electric power supplied to the heating member is made higher than in the normal state in the heat storage state of the heating member.

JP 2017-67826 A

However, in the above-described fixing device, when the heating member is in a heat storage state, the electric power supplied to the heating member is increased more than usual, and the temperature drop of the fixing member due to the passage of paper cannot be detected. There is a problem that the temperature ripple of the fixing member increases.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to reduce the temperature ripple of a fixing member.

A fixing device according to an aspect of the present invention includes a belt-like fixing member, a heat source disposed inside the fixing member for heating an inner peripheral surface of the fixing member, and a heat source contacting the heat source to generate a temperature of the heat source. a heat source temperature sensor for detecting a pressure detected by the heat source temperature sensor; a power control unit that calculates a maintenance power for maintaining the temperature of the heat source at a predetermined control temperature, and supplies the maintenance power to the heat source; A recording medium temperature sensor for detecting a temperature, a pressure member temperature sensor for detecting a temperature of the pressure member, and the recording medium being inserted into the nip portion, thereby allowing the recording medium to pass through the fixing member and the pressure member. a power calculation unit for calculating a power deprived corresponding to the amount of heat taken from the pressure member based on each temperature detected by the recording medium temperature sensor and the pressure member temperature sensor; a sum calculation unit that calculates a total power obtained by summing the deprivation power and the maintenance power that maintains the heat source at the control temperature, wherein the power control unit is configured so that the leading edge of the recording medium reaches the nip portion. Calculated by the total calculation unit by raising the control temperature of the heat source by an increase amount corresponding to the total power calculated by the total calculation unit at a pre-timing that is a predetermined time before the timing. and a fixing device that supplies the total electric power obtained from the heat source to the heat source.

Further, an image forming apparatus according to another aspect of the present invention includes an image forming unit that forms a toner image, and the fixing device that fixes the toner image formed by the image forming unit onto the surface of the recording medium. and an image forming apparatus.

According to the present invention, it is possible to reduce the temperature ripple of the fixing member.

1 is a cross-sectional view showing structures of a fixing device and an image forming apparatus according to a first exemplary embodiment of the present invention; FIG. 1 is a functional block diagram showing electrical configurations of a fixing device and an image forming apparatus according to a first embodiment of the invention; FIG. 1 is a cross-sectional view showing the configuration of a fixing device according to a first exemplary embodiment of the present invention; FIG. FIG. 10 is a diagram showing electric power and belt temperature when the timing of raising the control temperature is changed; 4 is a flowchart showing an example of temperature control processing of the fixing device according to the first embodiment; FIG. 5 is a cross-sectional view showing the configuration of a fixing device according to a second embodiment of the invention; (A) is a diagram showing the temperature of each layer of the belt on the exit side of the nip portion after passing the paper, and (B) is a diagram showing the temperature of each layer of the belt on the inlet side of the nip portion before the passing of the paper. 9 is a flowchart showing an example of temperature control processing of the fixing device according to the second embodiment; (A) is a diagram showing control temperature switching timing when T1<T2 in the fixing device according to the third embodiment; FIG. 5 is a diagram showing temperature switching timing;

A fixing device and an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing structures of a fixing device and an image forming apparatus according to one embodiment of the present invention. FIG. 2 is a functional block diagram showing electrical configurations of a fixing device and an image forming apparatus according to one embodiment of the invention.

The image forming apparatus 1 is, for example, a multifunction device having multiple functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus body 11, a document reading section 5, a document feeding section 6, a control unit 10, an image forming section 12, a paper feeding section 14, a fixing section 20, and the like. The image forming apparatus 1 has a fixing device 200 . The fixing device 200 includes a fixing section 20 and an operation control section 100 (particularly, a component of the operation control section 100 that controls the fixing section 20).

The control unit 10 includes a processor, RAM (Random Access Memory), ROM (Read Only Memory), and the like. The processor is a CPU (Central Processing Unit), MPU (Micro-Processing Unit), ASIC (Application Specific Integrated Circuit), or the like.

A control program stored in the ROM or the built-in HDD is executed by the CPU to control the control unit 10. The document reading section 5, the document feeding section 6, the image forming section 12, the paper feeding section 14, and the It functions as an operation control section 100 that controls operations of the fixing section 20 and the like.

Operation control section 100 includes power control section 101 , power calculation section 102 , total calculation section 103 , and storage section 104 . Storage unit 104 stores at least various data used in power control unit 101, power calculation unit 102, and total calculation unit 103, and information such as formulas (1) and (2) described later. there is

When the image forming apparatus 1 performs a document reading operation, under the control of the operation control section 100 , the document reading section 5 receives the document fed by the document feeding section 6 or placed on the document placing glass 161 . The image of the original document is optically read to generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD (Hard Disk Drive) or a computer connected to a network.

When the image forming apparatus 1 performs an image forming operation, under the control of the operation control unit 100, the image forming unit 12 converts the image data generated by the document reading operation or the image data stored in the built-in HDD. Based on this, a toner image is formed on a sheet of paper P as a recording medium fed from the paper feeding unit 14 .

When performing color printing, the image forming unit 12M for magenta, the image forming unit 12C for cyan, the image forming unit 12Y for yellow, and the image forming unit 12Bk for black of the image forming section 12 are charged, exposed, and developed. A toner image of each color is formed on the photosensitive drum 121 by the process of . The formed toner images of each color are superimposed on the intermediate transfer belt 125 by the primary transfer roller 126 to form a color toner image. The superimposed color toner images are transferred onto the paper P transported in the transport path 190 by the secondary transfer roller 210 . After the toner image is transferred to the sheet P in this way, the fixing unit 20 performs the fixing process, and the sheet P on which the fixing process is completed is discharged to the discharge tray 151 .

FIG. 3 is a cross-sectional view showing the configuration of the fixing section 20. As shown in FIG. The fixing section 20 includes a fixing roller 21 and a pressure roller 22 as main components. The fixing roller 21 and pressure roller 22 are accommodated in a housing 24 made of resin.

The pressure roller 22 is constructed by providing an elastic layer of silicone rubber on an iron core and coating the outer surface of the elastic layer with a PFA resin film having a thickness of 50 μm. The pressure roller 22 is pivotally supported in the housing 24 so as to be rotatable counterclockwise on the page of FIG. During the fixing process, the rotary shaft 23 of the pressure roller 22 is driven to rotate by a rotary drive section 95 (see FIG. 2) composed of a motor or the like under the control of the operation control section 100 . The pressure roller 22 and the fixing roller 21 form a nip portion N through which the paper P to be fixed is inserted. In addition, the pressure roller 22 is an example of a pressure member in the claims.

A pressure roller temperature sensor 221 that detects the temperature of the pressure roller 22 is arranged in the housing 24 . The pressure roller temperature sensor 221 is a non-contact temperature sensor that detects the temperature of the pressure roller 22 without contact. For example, the pressure roller temperature sensor 221 is arranged inside the housing 24 so as to be positioned on the side of the peripheral surface of the pressure roller 22 toward the nip portion N. As shown in FIG. The pressure roller temperature sensor 221 outputs a detection signal indicating the temperature value of the pressure roller 22 to the power control section 101 . The pressure roller temperature sensor 221 is an example of a pressure member temperature sensor in the claims.

The fixing roller 21 includes a belt-like fixing member 211, a heater 212 provided inside the fixing member 211, a heater temperature sensor 213, a holding member 214, a pressing member 215, and the like.

The fixing member 211 is constructed by coating the inner and outer surfaces of a stainless steel belt having an outer diameter of 30 mm and a thickness of 0.03 mm with a fluorine resin. The fixing member 211 is rotatably supported in the housing 24 clockwise in the plane of FIG. The fixing member 211 is pressed against the pressure roller 22 by a pressure member 215 made of a heat-resistant resin pad, and is driven to rotate as the pressure roller 22 rotates. The fixing member 211 forms a nip portion N between itself and the pressure roller 22 arranged to face the fixing member 211 , and fixes the toner image on the paper P inserted in the nip portion N.

Heater 212 is, for example, a ceramic heater. Note that the heater 212 may be a heat source such as an IH heater, a halogen lamp, or a xenon lamp. The heater 212 performs a heating operation during the fixing process under the control of the operation control unit 100, and stops the heating operation after the fixing process is completed. Note that the heater 212 is an example of a heat source in the claims.

The heater temperature sensor 213 is a contact temperature sensor that contacts the heater 212 and detects the temperature of the heater 212 . The heater temperature sensor 213 outputs a detection signal indicating the temperature value of the heater 212 to the power control section 101 . Note that the heater temperature sensor 213 is an example of a heat source temperature sensor in the claims.

A holding member 214 holds the heater 212 . For example, the holding member 214 holds the heater 212 in a state in which the heater temperature sensor 213 is in contact with the heater 212 in an accommodation recess having a size capable of accommodating the heater 212 .

The fixing device 200 also includes a paper transport guide 191 , a paper temperature sensor 192 , and a paper position detection sensor 193 . The paper transport guide 191 is a guide member that guides the paper P traveling from the transport path 190 toward the fixing unit 20 to the nip portion N. As shown in FIG. The paper temperature sensor 192 is a non-contact temperature sensor that detects the temperature of the paper P before being inserted into the nip portion N without contact. The paper temperature sensor 192 outputs a detection signal indicating the temperature value of the paper P to the power control unit 101 . Note that the paper temperature sensor 192 is an example of a recording medium temperature sensor in the scope of claims. Note that the fixing device 200 according to the present embodiment is described for a case where sheets P of the same predetermined size are fixed.

The paper position detection sensor 193 is a non-contact sensor that detects the position of the paper P facing the fixing section 20 . The paper position detection sensor 193 is arranged, for example, at a position separated from the nip portion N by a predetermined distance (for example, by one rotation of the fixing member 211) on the upstream side of the paper P transport. The paper position detection sensor 193 outputs a detection signal indicating detection of the paper P to the power control unit 101 . Based on the detection signal from the paper position detection sensor 193, the power control unit 101 can determine the advance timing that is a predetermined time before the arrival timing of the leading edge of the paper P reaching the nip portion N. be. For example, in the power control unit 101, the circumference L2 of the fixing member 211 is 80 [mm], the predetermined distance is also 80 [mm], and the linear velocity V of the fixing member 211 is 100 [mm/s]. ], the timing at which the paper position detection sensor 193 detects the leading edge of the paper P reaches the nip portion N in 0.8 seconds (80 [mm]/100 [mm/s]=0.8 second). Further, the power control unit 101 determines that the timing 0.7 seconds after the paper position detection sensor 193 detects the leading edge of the paper P is the timing 0.1 seconds before reaching the nip portion N. .

The power control unit 101 maintains the temperature of the heater 212 detected by the heater temperature sensor 213 at a predetermined control temperature (that is, the fixing temperature). power required to maintain the temperature) is calculated, and the maintenance power is supplied to the heater 212 . The control temperature is determined by the type of toner used, and is, for example, a temperature of 100° C. or higher and 200° C. or lower, which is suitable for fixing (for example, 170° C.).

The electric power calculation unit 102 calculates the deprived electric power corresponding to the amount of heat taken away from the fixing member 211 and the pressure roller 22 by the paper P being inserted into the nip portion N, based on the paper temperature sensor 192 and the pressure roller temperature. It is calculated based on each temperature detected by the sensor 221 .

Specifically, the power calculator 102 calculates the stripped power Wpaper using the following formula (1).

Wpaper=S×(Tbelt−Tpaper)/a+S×(Tpr−Tpaper)/b (1)

where Wpaper: deprived power [W], S: area of nip portion N [m2], Tbelt: temperature of fixing member predicted from temperature detected by heat source temperature sensor [°C], Tpaper: detected by recording medium temperature sensor temperature of the recording medium measured [°C], Tpr: temperature of the pressure member detected by the pressure member temperature sensor [°C], a: contact thermal resistance between the fixing member and the recording medium [m2 x °C/W], b : Contact thermal resistance [m2×°C/W] between the pressure member and the recording medium . For example, the power calculation unit 102 calculates a correction value calculated or measured in advance (for example, the decrease in the temperature detected by the pressure roller temperature sensor 221 during paper feeding) from the temperature detected by the heater temperature sensor 213. The subtracted temperature is used as the temperature Tbelt [° C.] of the fixing member 211 predicted from the temperature detected by the heater temperature sensor 213 . Also, the temperature detected by the sensor that detects the temperature of the fixing member 211 may be the temperature Tbelt [°C].

The total calculation unit 103 calculates the total power by adding the deprived power calculated by the power calculation unit 102 and the maintenance power for maintaining the heater 212 at the control temperature. Note that the total calculation unit 103 calculates the maintenance power based on the controlled temperature of the heater 212 . Note that the storage unit 104 may store in advance the maintenance power for maintaining the heater 212 at the control temperature. In this case, the total calculation unit 103 calculates the total power by adding the deprived power calculated by the power calculation unit 102 and the maintenance power for maintaining the heater 212 at the control temperature stored in the storage unit 104. .

The power control unit 101 adjusts the control temperature of the heater 212 to the total power calculated by the total calculation unit 103 at a pre-determined timing prior to the arrival timing of the leading edge of the sheet P reaching the nip portion N. Increase by the amount appropriate to the As a result, the total power is supplied to the heater 212 at the arrival timing.

Specifically, the power control unit 101 can obtain the pre-timing using the following formula (2). Formula (2) is a formula for PID control, the left side is the consumption amount, the right side is the input amount, the first term on the right side indicates the I action (integral action) term, and the second term on the right side indicates the P-action (proportional action) term, and the third term on the right side indicates the D-action (differential action) term.

Wpaper + W = ∫ (Tsv + Tff - Tpv) dt x I + (Tsv + Tff - Tpv) x P + (T'pv - Tpv)/t x D ... Equation (2)

However, Wpaper: stripped power [W], W: maintenance power [W], Tsv: control temperature [°C], Tff: control temperature increase amount [°C], Tpv: heater temperature [°C], T'pv: 1 Heater temperature before cycle [°C], t: control cycle [s], I: coefficient of integral term, P: coefficient of proportional term, D: coefficient of proportional term.

The control temperature increase amount Tff is determined to be a predetermined value according to the type of recording medium and the temperature of the recording medium. The storage unit 104 stores the control temperature increase amount Tff according to the type of recording medium and the temperature of the recording medium. The power control unit 101 reads from the storage unit 104 the control temperature increase amount Tff according to the type of recording medium and the temperature of the recording medium. For example, if the type of paper P is a reference thickness paper and the temperature of the paper P is a specified temperature, the power control unit 101 reads from the storage unit 104 the corresponding control temperature increase amount Tff=20 [°C]. .

The power control unit 101 calculates the pre-timing dt by using the above equation (2) assuming that the heater temperature does not change (that is, Tpv=T'pv). For example, the power control unit 101 sets Tpv=T'pv, the total power (Wpaper+W) calculated by the total calculation unit 103 = 210 [W], the control temperature Tsv = 170 [°C], and raises the control temperature If the amount Tff = 20 [°C], the coefficient of the integral term I = 5, the coefficient of the proportional term P = 10, and the control period t = 0.1 [s], substitute each numerical value into the above equation (2). , the pre-timing dt can be obtained.
210(total power) = (170 + 20-170) x dt x 5 + (170 + 20-170) x 10 + 0
dt = 10/100 = 0.1 [s]
In the above example, the pre-timing dt is 0.1 seconds. Note that the values are not limited to the values described here, and other values may be used.

Here, the increase amount of the control temperature by the power control unit 101 and the increase timing will be described with reference to FIG. 4 . FIG. 4 is a diagram showing electric power and belt temperature when the timing of raising the control temperature is changed.

FIG. 4 shows the power waveform and the belt temperature when the control temperature of the heater 212 is increased at the arrival timing when the leading edge of the paper P reaches the nip portion N (prior timing: 0 ms). In this case, the belt temperature has decreased to about 120° C., and the temperature ripple of the fixing member 211 (that is, the belt temperature ripple) has increased.

On the other hand, when the control temperature of the heater 212 is increased at a pre-timing (100 ms) which is a predetermined time (100 ms) before the timing at which the leading edge of the paper P reaches the nip portion N (pre-timing: 100 ms), the power The waveform and belt temperature are shown by solid lines in FIG. In this case, the belt temperature stops decreasing at about 123° C., and the temperature ripple of the fixing member 211 (that is, belt temperature ripple) is smaller than in the case shown by the dashed line in FIG.

FIG. 4 shows the power waveform and the belt temperature when the control temperature of the heater 212 is increased 300 ms before the arrival timing of the leading edge of the paper P reaching the nip portion N (prior timing: 300 ms). indicated by . In this case, the belt temperature overshoots at the leading edge timing of the paper P, resulting in excessive heating, which is an undesirable result.

Here, temperature control processing of the fixing device 200 according to the first embodiment will be described with reference to FIG. FIG. 5 is a flowchart illustrating an example of temperature control processing of the fixing device according to the first embodiment;

For example, when the image forming apparatus 1 receives a print instruction from a user, the power control unit 101 supplies maintenance power to maintain the temperature of the heater 212 detected by the heater temperature sensor 213 at a predetermined control temperature (eg, 170° C.). W is calculated, and the maintenance power W is supplied to the heater 212 (S1).

The power calculation unit 102 calculates the deprived power Wpaper corresponding to the amount of heat taken away from the fixing member 211 and the pressure roller 22 by the paper P being inserted into the nip portion N, through the paper temperature sensor 192 and the pressure roller. It is calculated based on each temperature detected by the temperature sensor 221 (S2).

The total calculation unit 103 calculates the total power by adding the deprived power Wpaper calculated by the power calculation unit 102 and the maintenance power W for maintaining the heater 212 at the control temperature (S3).

The power control unit 101 reads from the storage unit 104 the control temperature increase amount Tff [° C.] according to the type of recording medium and the temperature of the recording medium. For example, if the type of paper P is a reference thickness paper and the temperature of the paper P is a specified temperature, the power control unit 101 reads from the storage unit 104 the corresponding control temperature increase amount Tff=20 [°C]. . In other words, the power control unit 101 reads the increase amount of the control temperature of the heater 212 for supplying the total power to the heater 212 . Then, the power control unit 101 calculates the pre-timing using the above equation (2) (S4). Here, it is assumed that the advance timing (for example, the timing 100 ms before the arrival timing) is calculated using the above equation (2).

Based on the detection signal from the paper position detection sensor 193, the power control unit 101 controls the timing of the leading edge of the paper P to reach the nip portion N by a predetermined time before the arrival timing (for example, 100 ms after the arrival timing). (S5). Specifically, the power control unit 101 sets the timing 0.7 seconds after the paper position detection sensor 193 detects the leading edge of the paper P to the preliminary timing 0.1 seconds before reaching the nip portion N. Determine that there is.

If the power control unit 101 determines that it is not the pre-timing (NO in S5), it returns to S5. 212, the control temperature of the heater 212 is increased (S6). That is, the power control unit 101 raises the control temperature of the heater 212 by the amount of increase T ff (=20 [° C.]) (for example, 190° C.) at the advance timing.

Based on the detection signal from the paper position detection sensor 193, the power control unit 101 determines whether or not it is time for the trailing edge of the paper P to reach the nip portion N (S7). Specifically, the power control unit 101 determines that the timing at which the paper P reaches the nip portion N is the timing 0.8 seconds after the paper position detection sensor 193 detects the trailing edge of the paper P.

If the power control unit 101 determines that it is not the timing for the trailing edge of the paper P to reach the nip portion N (NO in S7), the power control unit 101 returns to S7 and determines that it is the timing for the trailing edge of the paper P to reach the nip portion N. If so (YES in S7), the control temperature of the heater 212 is returned to the temperature before the increase (S8). That is, the power control unit 101 performs control (for example, control temperature 190° C.) is stopped, and the control temperature of the heater 212 is controlled to be the temperature before being increased (for example, 170° C.).

After S8, the operation control unit 100 determines whether or not printing is finished (S9). The operation control unit 100 determines that the printing is not finished when there is the next printing (NO in S9), and proceeds to S2. The power calculation unit 102 calculates the power deprived by the next sheet P (S2). Then, the above S2 to S8 are executed. On the other hand, if there is no next print, the operation control unit 100 determines that printing is finished (YES in S9), and ends this process.

According to the fixing unit 20 and the image forming apparatus 1 according to the first embodiment described above, the electric power calculation unit 102 allows the paper P to pass through the nip portion N, thereby causing the paper P to pass through the fixing member 211 and the pressure roller. 22 is calculated based on the temperatures detected by the paper temperature sensor 192 and the pressure roller temperature sensor 221 . The total calculation unit 103 calculates the total power (Wpaper+W) by adding the deprived power Wpaper calculated by the power calculation unit 102 and the maintenance power W for maintaining the heater 212 at the control temperature. The power control unit 101 adjusts the control temperature of the heater 212 to the total power calculated by the total calculation unit 103 at a pre-determined timing prior to the arrival timing of the leading edge of the sheet P reaching the nip portion N. The total power calculated by the total calculation unit 103 is supplied to the heater 212 by increasing the power by an amount corresponding to . As a result, the total power (Wpaper+W) is supplied to the heater 212 at the arrival timing. As a result, it is possible to adjust the increase amount and the increase timing of the control temperature of the fixing member 211 to suitable values, and reduce the temperature ripple of the fixing member 211 .

Further, since the power calculation unit 102 calculates the stripped power Wpaper corresponding to the amount of heat that the paper P takes from the fixing member 211 and the pressure roller 22 using the above equation (1), the stripped power Wpaper can be calculated accurately. be able to.

It should be noted that the present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

<Modification 1>
Note that the power control unit 101 may change the predetermined increase amount for the control temperature of the heater 212 for each type of paper P (thickness of paper, type of paper quality, etc.). Specifically, the storage unit 104 stores coefficients predetermined for each type of paper P, respectively. For example, if the paper P in the first embodiment is taken as a reference thickness, the coefficient is "1" in the case of this reference thickness, and the coefficient is "1" in the case of twice the reference thickness. When the thickness is "2" and the thickness is half the reference thickness, the coefficient is "0.5", and the coefficient is stored for each type of paper thickness.

When the user operates the operation unit 47 (see FIG. 1) of the image forming apparatus 1 to select the paper thickness as the type of the paper P, the power control unit 101 receives an instruction indicating the type of the paper P. FIG. When the power control unit 101 receives an instruction indicating the type of the paper P (here, the thickness is twice the reference thickness), the power control unit 101 sets a predetermined coefficient “2” corresponding to the type of the paper P. The result of reading from the storage unit 104 and multiplying the amount of increase by the read coefficient "2" is used as the amount of increase after change.

In the case of Modification 1, the power control unit 101 changes the control temperature increase amount of the heater 212 for each type of paper P. can do. As a result, the temperature ripple of the fixing member 211 can be reduced for multiple types of recording media (paper).

<Modification 2>
In addition, when the total power calculated by the total calculation unit 103 exceeds a predetermined specified value, the power control unit 101 calculates a new increase amount corresponding to the total power exceeding the specified value, The predetermined time may be changed to a time corresponding to the calculated new lifting amount. For example, the power control unit 101 calculates a multiple value indicating how many times the new increase amount is the increase amount in the first embodiment, and sets the calculated multiple value to the preset value of the first embodiment. Change to the time multiplied by the determined time. In the case of Modification 2, the pre-timing of raising the control temperature is advanced, so even if the amount of increase in the control temperature of the heater 212 is large, the temperature ripple of the fixing member 211 can be reduced.

Next, the fixing device 200 and the image forming apparatus 1 according to the second embodiment will be described with reference to FIGS. 6 to 8. FIG.

FIG. 6 is a cross-sectional view showing the configuration of a fixing device according to the second embodiment of the invention. FIG. 7A is a diagram showing the temperature of each layer of the belt on the exit side of the nip portion after passing the paper. FIG. 7B is a diagram showing the temperature of each layer of the belt on the inlet side of the nip portion before the paper is passed. FIG. 8 is a flowchart illustrating an example of temperature control processing of the fixing device according to the second embodiment.

The fixing device 200 and the image forming apparatus 1 according to the second embodiment set the control temperature of the heater 212 at the return timing before the timing at which the trailing edge of the sheet P leaves the nip portion N and the time before the fixing member 211 completes one rotation. The control for raising the temperature by a predetermined amount (for example, the control temperature is set to 170+20=190° C.) is stopped, and the control temperature of the heater 212 is returned to the temperature before raising (for example, 170° C.). Determination of the return timing in power control section 101 will be described later.

As shown in FIG. 6, the fixing member 211 includes a base layer 211A, an elastic layer 211B positioned on the base layer 211A, a surface layer 211C positioned on the elastic layer 211B and in contact with the paper P, It is a laminated structure having

The temperature of each layer (each layer of the belt) of the fixing member 211 at the point Nout on the exit side of the nip portion N after passing the paper shown in FIG. (eg, 170.degree. C.), the temperature of the surface layer 211C is much lower than the control temperature (eg, 170.degree. C.) (eg, about 120 to 150.degree. C.).

Note that the temperature of each layer (each belt layer) of the fixing member 211 at the point Nin on the entrance side of the nip portion N before and after the sheet passage shown in FIG. Both the temperature of the layer 211B and the surface layer 211C are maintained at about the control temperature (for example, 170°C).

According to FIG. 7A, it can be seen that the temperature of the base layer 211A is small while the temperature of the surface layer 211C is greatly decreased. Also, in the nip portion N, the paper P takes heat from the surface layer 211C, but it can be seen that the amount of heat taken from the elastic layer 211B and the base layer 211A is small. In other words, the heater 212 only needs to replenish the heat lost from the surface layer 211C, so the temperature of the surface layer 211C can be quickly saturated.

Also in the fixing device 200 according to the second embodiment, fixing is performed by controlling the control temperature of the heater 212 in the first embodiment to be increased by a predetermined amount (control temperature is set to 170+20=190° C., for example). Therefore, even if the control temperature is raised to the previous temperature (for example, 170° C.) from one rotation of the fixing member 211 (belt) before the trailing edge of the paper P leaves the nip portion N, the fixing member 211 does not Since the fixing member 211 maintains the amount of heat necessary for fixing when it rotates once, the fixing performance does not deteriorate.

Based on the detection signal from the paper position detection sensor 193, the power control unit 101 can determine the return timing before the time at which the trailing edge of the paper P leaves the nip portion N and the fixing member 211 making one revolution. It is possible. For example, in the power control unit 101, the circumference L2 of the fixing member 211 is 80 [mm], the predetermined distance is also 80 [mm], and the linear velocity V of the fixing member 211 is 100 [mm/s]. ], the timing at which the paper position detection sensor 193 detects the trailing edge of the paper P is 0.8 seconds (80 [mm]/100 [mm/s]=0.8 seconds) before reaching the nip portion N. 8 seconds) before the fixing member 211 makes one revolution.

Therefore, the power control unit 101 raises the control temperature of the heater 212 to the temperature before raising the control temperature of the heater 212 (for example, 170° C.) at the return timing before the timing when the trailing edge of the sheet P leaves the nip portion N and the time before the fixing member 211 completes one revolution. ).

Here, temperature control processing of the fixing device 200 according to the second embodiment will be described with reference to FIG. Since the temperature control process shown in FIG. 8 differs from the temperature control process of the first embodiment described above only in S7A, S7A will be described.

Based on the detection signal from the paper position detection sensor 193, the power control unit 101 determines whether the return timing is before the time at which the trailing edge of the paper P exits the nip portion N and the fixing member 211 makes one revolution. is determined (S7A). For example, in the power control unit 101, the circumference L2 of the fixing member 211 is 80 [mm], the predetermined distance is also 80 [mm], and the linear velocity V of the fixing member 211 is 100 [mm/s]. ], the timing at which the paper position detection sensor 193 detects the trailing edge of the paper P is 0.8 seconds (80 [mm]/100 [mm/s]=0.8 seconds) before reaching the nip portion N. 8 seconds) before the fixing member 211 makes one revolution.

According to the fixing unit 20 and the image forming apparatus 1 according to the second embodiment described above, the power control unit 101 controls the timing before the trailing edge of the sheet P leaves the nip portion N and the time before the fixing member 211 completes one revolution. At the return timing, the control temperature of the heater 212 is returned to the temperature before being increased, so that the power supply required for the amount of increase in the control temperature for the time for the fixing member 211 to go around once can be reduced, and the power can be saved. can be done. Further, at the return timing, even if the control temperature of the heater 212 is returned to the temperature before being raised, the fixing member 211 retains the amount of heat required for fixing when the fixing member 211 rotates once. not decrease.

Next, the fixing device 200 and the image forming apparatus 1 according to the third embodiment will be described with reference to FIG. FIG. 9A is a diagram showing control temperature switching timing when T1<T2 in the fixing device according to the third embodiment. FIG. 9B is a diagram showing control temperature switching timing when T1>T2 in the fixing device according to the third embodiment.

In addition, in the fixing section 20 and the image forming apparatus 1 according to the third embodiment, as shown in FIG. When the time T2 for the fixing member 211 to make one revolution is longer than the time T1, the time for the fixing member 211 to make one revolution, which is a predetermined time before the timing at which the leading edge of the paper P reaches the nip portion N. The control temperature of the heater 212 may be increased by the predetermined increase amount at the previous timing (that is, before the time T2). In the case of T1>T2, the paper position detection sensor 193 may be arranged at a distance corresponding to the time T1 from the nip portion N to the upstream side of the paper P transport.

In this case, the power control unit 101 controls the temperature difference between the base layer 211A and the surface layer 211C when the time T2 required for one rotation of the fixing member 211 is longer than the time T1 required for the temperature difference between the base layer 211A and the surface layer 211C to be saturated. At a preliminary timing before the fixing member 211 completes one revolution (that is, before the time T2), which is a predetermined time before the timing at which the leading edge reaches the nip portion N, the control temperature of the heater 212 is set to the predetermined value. Pull up by the amount you lift. As a result, it is possible to adjust the increase amount and the increase timing of the control temperature of the fixing member 211 to suitable values, and reduce the temperature ripple of the fixing member 211 .

In addition, in the fixing unit 20 and the image forming apparatus 1 according to the third embodiment, the power control unit 101 predetermines the timing at which the leading edge of the sheet P reaches the nip portion N, as shown in FIG. 9B. control to raise the control temperature of the heater 212 by the predetermined raising amount at a preliminary timing (before the time T1) before the temperature difference between the base layer 211A and the surface layer 211C is saturated, which is before the predetermined time. may be started.

In this case, when the time T1 until the temperature difference between the base layer 211A and the surface layer 211C is saturated is longer than the time T2 for the fixing member 211 to make one revolution, the power control unit 101 controls the paper P at the timing before the temperature difference between the base layer 211A and the surface layer 211C is saturated (before the time T1), which is a predetermined time before the timing when the tip of the heater 212 reaches the nip portion N. is increased by the predetermined increase amount. As a result, it is possible to adjust the increase amount and the increase timing of the control temperature of the fixing member 211 to suitable values, and reduce the temperature ripple of the fixing member 211 .

1 image forming apparatus 10 control unit 12 image forming section 20 fixing section 21 fixing roller 22 pressure roller (pressure member)
100 Operation control unit 101 Power control unit 102 Power calculation unit 103 Total calculation unit 192 Paper temperature sensor (recording medium temperature sensor)
200 fixing device 211 fixing member 211A base layer 211B elastic layer 211C surface layer 212 heater (heat source)
213 heater temperature sensor (heat source temperature sensor)
221 pressure roller temperature sensor (pressure member temperature sensor)

Claims (8)

a belt-shaped fixing member;
a heat source disposed inside the fixing member for heating an inner peripheral surface of the fixing member;
a heat source temperature sensor that contacts the heat source and detects the temperature of the heat source;
a pressing member disposed opposite to the fixing member and forming a nip portion between the fixing member and the fixing member through which a recording medium to be fixed is inserted;
a power control unit that calculates maintenance power for maintaining the temperature of the heat source detected by the heat source temperature sensor at a predetermined control temperature, and supplies the maintenance power to the heat source;
a recording medium temperature sensor that detects the temperature of the recording medium before being inserted into the nip portion;
a pressure member temperature sensor that detects the temperature of the pressure member;
The recording medium temperature sensor and the pressure member temperature sensor detect a deprived power corresponding to an amount of heat that the recording medium deprives from the fixing member and the pressure member when the recording medium is inserted into the nip portion. A power calculation unit that calculates based on each temperature that is calculated,
a total calculation unit that calculates a total power obtained by adding the deprived power calculated by the power calculation unit and the maintenance power that maintains the heat source at the control temperature;
The power control unit calculates the control temperature of the heat source at a pre-timing that is a predetermined time before the timing at which the leading edge of the recording medium reaches the nip portion. A fixing device that supplies the total power calculated by the total calculation unit to the heat source by increasing the amount of power increase corresponding to the total power. The power calculation unit calculates the deprived power as
Wpaper=S×(Tbelt−Tpaper)/a+S×(Tpr−Tpaper)/b (1)
2. The fixing device according to claim 1, which is calculated using the above formula (1).
where Wpaper: deprived power [W], S: area of nip [m2], Tbelt: temperature of fixing member predicted from temperature detected by heat source temperature sensor [°C], Tpaper: detected by recording medium temperature sensor Temperature of the recording medium [°C], Tpr: temperature of the pressure member detected by the pressure member temperature sensor [°C], a: contact thermal resistance between the fixing member and the recording medium [m2 x °C/W], b: It is the contact thermal resistance [m2×°C/W] between the pressure member and the recording medium . further comprising a storage unit that stores coefficients predetermined for each type of the recording medium,
The power control unit, when receiving an instruction indicating the type of the recording medium, reads the predetermined coefficient corresponding to the type of the recording medium from the storage unit, and converts the read coefficient to the increase amount. 3. The fixing device according to claim 1, wherein the result of multiplying by is used as the changed lifting amount. When the total power calculated by the total calculation unit exceeds a predetermined specified value, the power control unit calculates a new increase amount corresponding to the total power exceeding the specified value, 4. The fixing device according to claim 1, wherein the calculated time is changed to a time corresponding to the calculated new lifting amount. The power control unit controls to increase the control temperature of the heat source by a predetermined increase amount at a return timing before the time at which the fixing member rotates once before the timing at which the trailing edge of the recording medium exits the nip portion. 5. The fixing device according to any one of claims 1 to 4, wherein the control temperature of the heat source is set to the temperature before raising the control temperature of the heat source. The fixing member has a laminated structure including a substrate layer and a surface layer located on the substrate layer and in contact with the recording medium,
The power control unit operates a predetermined time earlier than the timing at which the leading edge of the recording medium reaches the nip portion by the time until the temperature difference between the base layer and the surface layer is saturated. 6. The fixing device according to claim 5, wherein control for increasing the control temperature of the heat source by a predetermined increase amount is started at advance timing. The fixing member has a laminated structure including a substrate layer and a surface layer located on the substrate layer and in contact with the recording medium,
The power control unit controls the control temperature of the heat source at a predetermined time earlier than the timing at which the leading edge of the recording medium reaches the nip portion by the time the fixing member makes one revolution. 6. The fixing device according to claim 5, wherein the control is started to pull up by a predetermined amount. an image forming unit that forms a toner image;
8. An image forming apparatus comprising: a fixing device according to claim 1, which fixes a toner image formed by said image forming section onto a surface of said recording medium.

Images