JP4720239B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using dry toner, such as an electrophotographic copying machine, a printer, and a facsimile.

  An image forming apparatus using dry toner such as an electrophotographic method or an electrostatic recording method fixes the unfixed toner image on the recording medium by heating and pressurizing the recording medium on which the unfixed toner image is formed. Fixing means for obtaining a toner image. As the heating means, there are a heating roller system that maintains a predetermined temperature by a built-in heat source such as a halogen heater, and a film heating system that heats the fixing nip portion intensively. Recently, there is a need for an image forming apparatus that shortens the warm-up time from the start to the usable state, and this warm-up time is caused by the time until the temperature of the heating portion of the fixing unit reaches a predetermined temperature. Therefore, a film heating method is often used as the fixing means.

  Since the recording medium conveyed to the fixing unit is rapidly heated by the fixing unit, the water content in the recording medium is generated as water vapor. At the time of starting up the image forming apparatus and the like, since the parts other than the fixing unit are still in a cold state, the generated water vapor may come into contact with these parts to cause dew condensation. For example, condensation may occur on the photoreceptor.

  Therefore, in order to prevent the occurrence of condensation, a partition member in which the recording medium introduction opening on the upstream side of the fixing nip is set narrowly is provided on the upstream side of the fixing unit, and the image disposed on the upstream side of the fixing unit. There is a technique for preventing the formation of condensation on a forming portion (for example, a photoreceptor) (see Patent Document 1).

Further, on the downstream side of the fixing unit, a guide unit that guides exhaust gas is provided on the downstream side of the fixing unit, and air is actively blown toward the conveyance path by the guide unit, thereby generating from the recording medium. There is a technique for forcibly discharging water vapor (see Patent Document 2).
JP 11-344886 A JP-A 61-14161

  However, since Patent Documents 1 and 2 described above are based on the premise that exhaust after warming up sufficiently is used, only cold air can be blown when the apparatus is not warmed up. The occurrence of this cannot be reliably prevented. In particular, when the generated water vapor comes into contact with a low-temperature portion positioned downstream of the fixing unit, for example, a metal portion such as a shaft of a paper transport roller, condensation occurs immediately.

The present invention may be a relatively short image forming apparatus of the warm-up time, and to provide the images forming apparatus that can of preventing dew condensation on the site located in the fixing means near.

In order to solve the above-mentioned problem, the invention described in claim 1 is to fix the unfixed toner image on the recording medium by heating and pressurizing the recording medium on which the unfixed toner image is formed. an image forming apparatus comprising a fixing means for obtaining a heating body and pressure body for conveying the recording medium while forming a fixing nip portion in pressure contact with each other, by covering the heating body and the pressure body, A heat radiation shielding member having an insertion hole through which the recording medium is inserted , and an inner space with the heating body and the pressure body and an outer space without the heating body and the pressure body, and the heat radiation shielding member provided in the insertion hole near the opening and closing means for opening and closing said insertion hole, said one of the outer space, provided in front Symbol insertion hole side of the heat radiation shielding member, blowing means for blowing air toward the insertion hole near and, before An environment measuring means for measuring the temperature and humidity of the outer space, and when the temperature measured by the environment measuring means is lower than a first threshold, the opening and closing means are opened and the air blowing means is driven to measure the temperature. When the temperature is equal to or higher than the first threshold and the humidity measured by the environment measuring means is lower than the second threshold, the opening / closing means is closed and the air blowing means is stopped. Control means for closing the opening / closing means and driving the air blowing means when the temperature is equal to or higher than the first threshold and the measured humidity is equal to or higher than the second threshold ; It is characterized by doing.

In the above configuration, the heat radiation shielding member has the insertion holes on the inlet side and the outlet side of the recording medium, and the opening / closing means is generated from the heating body among the insertion holes on the inlet side or the outlet side. It is provided only in the vicinity of the insertion hole on the side where the heat flow rises .

  In the present invention, by controlling the opening / closing means and the air blowing means, the vicinity of the fixing means is efficiently warmed by the heat generated from the heating body. As a result, even when the apparatus is activated, the surroundings of the fixing unit are warmed, so that dew condensation that occurs around the fixing unit can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of an image forming apparatus to which the present invention is applied.

  In FIG. 1, an image forming apparatus 10 is an intermediate transfer type image forming apparatus, and each color component (for example, yellow (Y), magenta (M)) is disposed above a casing 11 of the image forming apparatus 10 by, for example, electrophotography. , Cyan (C), black (K) toner image forming module 20 is disposed, and multi-stage sheet trays 31 to 33 are disposed below the image forming module 20.

  Here, the image forming module 20 arranges photosensitive drums 21 (specifically, 21Y, 21M, 21C, and 21K) that form and carry each color component toner image in parallel, and each color component toner formed by each photosensitive drum 21. The image is primarily transferred to the intermediate transfer belt 22, and each color component toner image on the intermediate transfer belt 22 is secondarily transferred to the sheet S such as paper supplied from the sheet trays 31 to 33 by the secondary transfer roller 23 and fixed. This is guided to the device 50.

In the present embodiment, the conveyance path 40 from the sheet trays 31 to 33 passes through the secondary transfer roller 23 and the fixing device 50 of the image forming module 20 and discharges the sheet formed on the upper surface of the image forming apparatus 10. A main conveyance path 41 toward the section 35 side, and a return conveyance path that is provided on the lower side near the exit of the main conveyance path 41, reverses the front and back of the sheet S, and returns to the main conveyance path 41 in front of the image forming module 20 again. 42. As described above, the conveyance path 40 includes a mechanism for reversing the front and back of the sheet S by the switchback method, and enables duplex printing.

  Next, the configuration of the fixing device 50 will be described with reference to FIG. The fixing device 50 includes a case 51 having a heat shielding effect from its material, a heating roller 52 housed in the case 51 and including a heater 52A, a pressure roller 53 pressed against the heating roller 52, And generally configured.

  The case 51 is formed in a circular arc shape in cross section, and has a carry-in insertion hole 51A and a carry-out insertion hole 51B through which the sheet S is conveyed from the lower side toward the upper side. The case 51 includes an inner layer having a high thermal reflectance and an outer layer made of a material having a low thermal conductivity. The heating roller 52 and the pressure roller 53 are disposed in the case 51 so that the peripheral surfaces thereof face the inner layer.

  On the carry-out side insertion hole 51B side of the case 51, a shutter 54 for opening and closing the carry-out side insertion hole 51B is provided. Further, in the portion of the housing 11 that is located on the unloading side insertion hole 51B side, air from the outside (the sheet discharge portion 35) is supplied to the vicinity of the unloading side insertion hole 51B side in the housing 11 (hereinafter referred to as “space R”). Is provided) (see FIG. 1).

  Reference numeral 56 denotes a temperature / humidity sensor. The temperature / humidity sensor 56 is provided in the vicinity of the carry-out side insertion hole 51B of the fixing device 50, detects the temperature and humidity in the vicinity thereof, and sends the detection result to a control unit 60 described later. Send. Reference numeral 57 is a plate-like peeling member, and the peeling member 57 is disposed at an acute angle with respect to the heating roller 52 and peels off the sheet S attached to the heating roller 52.

Here, the structure of the control part 60 is demonstrated based on FIG.
The control unit 60 includes an input / output unit 60A such as an interface, a CPU (Central Processing Unit) 60B, a ROM (Read Only Memory) 60C, a RAM (Random Access Memory) 60D, a storage area 60E, and the like. Moreover, the control part 60 is provided with the timer mechanism, and measures time by instruction | command.
The input / output unit 60A has a temperature / humidity sensor 56, a heater temperature sensor 58, and an image forming module 20 connected to its input side, a heater 52A connected to the output side via a heater drive circuit 52B, and a shutter 54. The shutter 55 is connected via the shutter drive circuit 54A, and the fan 55 is connected via the fan drive circuit 55A. Although not shown in FIG. 2, the heater temperature sensor 58 is installed at a position where the surface temperature of the heating roller 52 is directly detected.

The ROM 60C stores a program for controlling the operation of the image forming apparatus 10 , a fixing device control program for controlling the operations of the heater 52A, the shutter 54, and the fan 55, and the like. The RAM 60D is used as a work area when executing the program.

  Further, in the storage area 60E, a preset start reference time Ts0, space reference temperature t0, space reference humidity h0, heater reference temperatures H1, H2, standby state switching time Tn0, fan 55 rotation speeds F1, F2, etc. Various parameters are stored.

Here, various parameters will be described. The start reference time Ts0 is the time from the start of the image forming apparatus 10 until the space R reaches room temperature, and the operation of the fixing device 50 is processed depending on whether or not the start reference time Ts0 has elapsed since the start. This is a reference value for switching from normal processing to normal processing. In other words, in this embodiment, when the start reference time Ts0 has elapsed since the image forming apparatus 10 was started, the inside of the apparatus 10 is warmed to some extent, and therefore, it is considered that there is no concern about condensation due to water vapor.
The starting reference time Ts0 is set to, for example, 30 minutes. Since the starting reference time Ts0 is caused by an external temperature, data corresponding to the air temperature is stored in the storage area 60E in advance even if the starting reference time Ts0 is arbitrarily set at the start of processing. You may remember as.

  The space reference temperature t 0 and the space reference humidity h 0 are reference values that determine the operation of the shutter 54 and the fan 55 from the detection result from the temperature / humidity sensor 56. Specifically, the space reference temperature t0 is a temperature at which condensation is unlikely to occur in the space R (for example, 30 ° C.), and the space reference humidity h0 is a humidity at which condensation is unlikely to occur in the space R (for example, 50%).

  The heater reference temperatures H1 and H2 are temperatures that serve as a reference for controlling the surface temperature of the heating roller 52. The relationship is H1 <H2, and H1 = 160 ° C. and H2 = 180 ° C. are set. The standby state switching time Tn0 is a reference time for switching to the standby state (or power saving state), and is, for example, 3 hours. Further, the rotation speeds F1 and F2 of the fan 55 adjust the strength of the wind from the outside flowing into the space R, and the relationship between these is F1> F2.

Next, the control process of the fixing device will be described with reference to the flowcharts of FIGS. This process is a process performed separately from the process of controlling the operation of the image forming apparatus 10 and ends when the power supply is opened.
First, the overall processing flow of the fixing device will be described with reference to FIG.
The CPU 60B of the control unit 60 detects whether or not the power is turned on (step Sa1).
When the power is turned on (step Sa1; YES), the start timer Ts is started (step Sa2). Further, the CPU 60B transmits a drive signal to the heater drive circuit 52B and supplies a current to the heater 52A. Accordingly, the heater 52A is turned on and starts a heat generating operation (step Sa3).

  Further, the CPU 60B determines whether or not the measured value of the start timer Ts exceeds the start reference time Ts0 (step Sa4). In this determination, when the value of the start timer Ts has not reached the start reference time Ts0 (step Sa4; NO), the process proceeds to a startup process (step Sa5) described later, and when it exceeds (step Sa4; YES). Shifts to a normal process (step Sa6) to be described later.

  Here, the startup process is a process performed until the space R reaches room temperature, and the normal process is a process performed after the space R reaches room temperature. For example, when the starting reference time Ts0 is 30 minutes, this image forming apparatus performs startup processing until 30 minutes have elapsed after startup of the apparatus 10, and performs normal processing after 30 minutes. It will be.

Next, the startup process of the fixing device will be described with reference to FIG.
The CPU 60B measures the temperature t and the humidity h of the space R from the temperature / humidity sensor 56 (steps Sb1, Sb2). Next, the CPU 60B determines whether or not the temperature t of the space R is lower than the space reference temperature t0 (step Sb3).

  Here, when the CPU 60B determines that the temperature t is lower than the space reference temperature t0 (step Sb3; YES), the CPU 60B regards the space R as a space where condensation is likely to occur regardless of the humidity h. . Therefore, the CPU 60B transmits an opening signal to the shutter drive circuit 54A, moves the shutter 54, and opens the carry-out side insertion hole 51B (step Sb4). Further, the CPU 60B transmits a drive signal to the fan drive circuit 55A, and drives the fan 55 at the rotation speed F1 (step Sb5).

  Thereby, as shown in FIG. 2, the heat flow generated from the heating roller 52 rises to the space R via the carry-out side insertion hole 51B. On the other hand, in the space R, an air flow as shown by an arrow is formed by the inflow air generated from the fan 55, and this flow causes a venturi effect and positively introduces the heat flow into the space R. Thereby, the space R can be warmed in a relatively short time.

  Returning to FIG. 5 again, if the temperature t exceeds the space reference temperature t0 (step Sb3; NO) in the determination in step S3, the CPU 60B transmits a closing signal to the shutter drive circuit 54A, and the shutter 54 Is moved to close the carry-out side insertion hole 51B (step Sb6). Further, the CPU 60B determines whether or not the humidity h of the space R is lower than the space reference humidity h0 (step Sb7).

  Here, when the CPU 60B determines that the humidity h is lower than the space reference humidity h0 (step Sb7; YES), the space R is t ≧ t0 & h <h0, so that the condensation is difficult to occur. It is considered. Therefore, the CPU 60B stops the drive signal transmitted to the fan drive circuit 55A and stops the fan 55 (step Sb8). Thereby, the state of the space R in which condensation does not easily occur is maintained.

  On the other hand, when the CPU 60B determines that the humidity h is higher than the space reference humidity h0 (step Sb7; YES), since the humidity in the space R is high, the CPU 60B transmits a drive signal to the fan drive circuit 55A to Drive at the rotation speed F2 (step Sb9). Accordingly, the space R is agitated with a weak air flow in a state where the unloading side insertion hole 51B is closed by the shutter 54.

Next, the CPU 60B measures the heater temperature H from the heater temperature sensor 58 (step Sb10), and performs control to keep the heater temperature H between the heater reference temperatures H1 and H2.
Specifically, when the heater temperature H becomes lower than the lower heater reference temperature H1 (step Sb11; YES), the CPU 60B transmits a drive signal to the heater drive circuit 52B and supplies current to the heater 52A. Heat is generated from the heater 52A (step Sb12).

  On the other hand, when the heater temperature H becomes higher than the high heater reference temperature H2 (step Sb13; YES), the drive signal transmitted to the heater drive circuit 52B is stopped, and the heat generation of the heater 52A is stopped (step Sb14). As described above, the CPU 60B performs the feedback control based on the heater temperature H, thereby maintaining the heater temperature H within a certain range.

  Further, the CPU 60B determines whether or not the value of the start timer Ts that has started measurement exceeds the start reference time Ts0 (step Sb15). When the value of the start timer Ts exceeds the start reference time Ts0 (step Sb15; YES), the CPU 60B proceeds to step Sa6 in FIG. 4 in order to shift from the startup process to the normal process. On the other hand, when the value of the start timer Ts has not reached the start reference time Ts0 (step Sb15; NO), the CPU 60B returns to step Sb1 and executes this startup process.

  In this startup process, the process is performed according to the determination shown in FIG. That is, when the temperature is low (t <t0), regardless of the value of humidity h, the carry-out side insertion hole 51B is opened by the shutter 54, and the fan 55 is rotated at the rotation speed F1. When the temperature is normal temperature (t> t0) and the humidity is h> h0, the carry-out side insertion hole 51B is closed by the shutter 54, and the fan 55 is rotated at the low rotation F2. When the temperature is normal temperature (t> t0) and the humidity is h <h0, the carry-out side insertion hole 51B is closed by the shutter 54, and the fan 55 is stopped.

  In this startup process, the shutter 54 and the fan 55 are driven and controlled based on the temperature t and humidity h of the space R. The space R can be efficiently warmed using the heat of the heating roller 52, and the space R can be warmed to room temperature within a warm-up time in which the image forming apparatus 10 is activated after being activated. Thereby, even when the sheet S heated from the fixing device 50 is conveyed to the space R, the temperature of the portion located in the space R is normal temperature, so that water vapor generated from the sheet S adheres. Condensation does not occur and defects due to condensation can be reliably prevented.

Next, normal processing of the fixing device will be described with reference to FIG.
The CPU 60B starts an inactivity timer Tn. The non-operation timer Tn measures the time during which no printing process is performed. When the standby state switching time Tn0 stored in advance has elapsed, the apparatus 10 shifts from the normal operation state to the standby state. .

The CPU 60B executes the processes of steps Sb10 to Sb14 in order to control the temperature H of the heater 52A. Since this process has been described above, a description thereof is omitted here.
Next, the CPU 60B determines whether or not the non-operation timer Tn has passed the standby state switching time Tn0. If it has not elapsed (step Sc2; NO), the rollers 52 and 53 rotate at any time. The shutter 54 opens the carry-out side insertion hole 51B so that the sheet S can be fixed (step Sc3).

On the other hand, when the non-operation timer Tn has passed the standby state switching time Tn0 (step Sc2; YES), the CPU 60B shifts the apparatus 10 to the standby state, so that the shutter 54 is carried out as shown in FIG. The side insertion hole 51B is closed (step Sc4). Thereby, the heat generated from the heater 52A is shielded by the case 51 having a heat shielding action. For this reason, in the standby state, by separating the inside of the case 51 and the space R by the shutter 54 , the heat dissipation amount of the heater 52A can be reduced, and consequently the power consumption for generating heat from the heater 52A can be reduced. .

  Further, the CPU 60B determines whether or not the rollers 52 and 53 are rotated, that is, whether or not a signal for rotating the rollers 52 and 53 is transmitted (step Sc5). In this determination, when a signal for rotating the rollers 52 and 53 is transmitted (step Sc5; YES), the CPU 60B returns (step Sc6) and performs the normal operation processing (not shown) of the fixing device 50. Execute.

  FIG. 9 shows the operation of the fixing device 50 when the sheet S is conveyed along the main conveyance path 41. A toner image is secondarily transferred to the sheet S by a secondary transfer roller 23. Then, the sheet is sandwiched between the heating roller 52 and the pressure roller 53 to be heated and pressurized, and the toner image is fixed on the sheet S. Thereafter, the sheet S passes through the carry-out side insertion hole 51 </ b> B, passes through the space R, and is conveyed to the sheet discharge unit 35. At this time, the CPU 60B can efficiently cool the sheet S conveyed through the main conveyance path 41 by rotating the fan 55 at the rotation speed F1. Accordingly, toner blocking caused by melting of the toner image when the sheet S is stored in the sheet discharge unit 35 can be prevented. In particular, by cooling the sheet S, it is possible to prevent image defects in double-sided printing.

  In this embodiment, since the shutter 54 and the fan 55 are driven and controlled based on the temperature t and humidity h of the space R as described in the start-up process, the space R is made efficient by using the heat of the heating roller 52. Can be warmed up. As a result, the space R can be warmed to room temperature within a warm-up time in which the image forming apparatus 10 is activated after the image forming apparatus 10 is activated. As a result, even when the sheet S heated from the fixing device 50 is conveyed to the space R immediately after the image forming apparatus 10 is activated, the temperature of the portion located in the space R is normal. Further, the water vapor generated from the sheet S does not adhere to cause condensation, and it is possible to reliably prevent problems due to condensation.

  Further, since the heating roller 52 and the pressure roller 53 are covered with the case 51, it is possible to reduce leakage of noise generated by rotation or the like to the outside.

  Further, the sheet S after fixing can be cooled by the flow of air generated from the fan 55, and defects such as uneven glossiness of the image generated when the conveying roller contacts the sheet S after fixing can be reduced. Can do.

  When the image forming apparatus 10 is in the standby state, the heating roller 52 and the pressure roller 53 are shut off from the outside by the shutter 54, and the temperature control of the heater 52A is performed, thereby realizing energy saving.

  In the above-described embodiment, the air blowing means is described as the fan 55 that flows in air from the outside. However, the present invention is not limited to this and may be as shown in FIG. In other words, a plurality of intake holes 59, 59,... As a result, by driving the exhaust fan 55 ′, the air in the space R is discharged to the outside, so that the air flows in from the intake holes 59. Thereby, an air flow is generated. At this time, when the shutter 54 is opened, the heat flow of the heating roller 52 flows into the space R through the carry-out side insertion hole 51B. Thus, also in this example, the space R can be efficiently warmed. Moreover, since the air in the space R can be discharged, water vapor generated in the space R can be discharged to the outside.

In the above embodiment, the case where the shutter 54 is provided only in the carry-out insertion hole 51B of the case 51 has been described as an example. However, the present invention is not limited thereto, and may be provided in the carry-in insertion hole 51A. Of course.

  Further, the fixing device 50 is configured to be heated and pressed while the sheet S moves upward. However, the fixing device 50 is not limited to this, and when the sheet S is moved in the lateral direction, the sheet S is heated and pressed. You may use also for a fixing device.

  The image forming apparatus 10 of the above embodiment has been mainly described as a printer. However, the present invention is not limited to this, and the present invention can be used in an image forming apparatus using dry toner such as a copying machine and a facsimile. .

1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a fixing device used in the embodiment. It is a figure which shows the control system of the fixing device used for the embodiment. 6 is a flowchart showing a control process of the fixing device according to the embodiment. 6 is a flowchart showing processing at the time of startup of the fixing device according to the embodiment. 5 is a flowchart showing normal processing of the fixing device according to the embodiment. It is a figure which shows the operation state of the shutter and fan in the process at the time of starting. FIG. 6 is a diagram illustrating a state in which a space R is warmed when the fixing device is activated. FIG. 10 is a diagram illustrating an operation in fixing a sheet S of the fixing device. It is an enlarged view showing a fixing device according to a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 40 ... Conveyance path, 50 ... Fixing device, 51 ... Case, 51A ... Carry-in side insertion hole, 51B ... Carry-out side insertion hole, 52 ... Heating roller, 52A ... Heater, 53 ... Pressure roller, 54 ... Shutter, 55 ... Fan, 56 ... Temperature / humidity sensor, 57 ... Peeling member, 60 ... Control part R ... Space, S ... Sheet.

Claims (2)

In an image forming apparatus including a fixing unit that heats and pressurizes a recording medium on which an unfixed toner image is formed to fix the unfixed toner image on the recording medium to obtain a toner image.
A heating body and a pressure body that convey the recording medium while forming a fixing nip portion in pressure contact with each other;
By covering the heating body and the pressurizing body , it is divided into an inner space with the heating body and the pressurizing body and an outer space without the heating body and the pressurizing body, and an insertion hole through which the recording medium is inserted A heat dissipation shielding member having
An opening / closing means provided in the vicinity of the insertion hole of the heat radiation shielding member, for opening and closing the insertion hole;
Among the outer space, provided in front Symbol insertion hole side of the heat radiation shielding member, and blowing means for blowing air toward the insertion hole near
Environmental measuring means for measuring the temperature and humidity of the outer space;
When the temperature measured by the environment measuring unit is lower than the first threshold, the opening / closing unit is opened and the blowing unit is driven, and the measured temperature is equal to or higher than the first threshold, and When the humidity measured by the environment measuring means is lower than a second threshold value, the opening / closing means is closed and the air blowing means is stopped, and the measured temperature is equal to or higher than the first threshold value, and When the measured humidity is equal to or higher than the second threshold, the control means for closing the opening and closing means and driving the air blowing means ,
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The heat radiation shielding member has the insertion holes on the inlet side and the outlet side of the recording medium,
The image forming apparatus , wherein the opening / closing means is provided only in the vicinity of the insertion hole on the side where the heat flow generated from the heating body rises among the insertion holes on the inlet side or the outlet side .

Images