JP4108363B2 - Fixing device and image forming apparatus having the fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device that fixes an unfixed toner image carried on a recording medium, and an image forming apparatus having the fixing device.
[0002]
[Prior art]
In an image forming apparatus configured as an electronic copying machine, a printer, a facsimile machine, or a multifunction machine having at least two of these functions, an unfixed toner image carried on a recording medium is recorded by the action of heat and pressure. A fixing device for fixing on top is used. Various types of fixing devices have been proposed and put to practical use as such fixing devices. However, any type of fixing device has a fixing member heated by a heating means, and the temperature of the fixing member is adjusted. The temperature is detected by the temperature detecting means, and the temperature of the fixing member is controlled based on the detection result. As such a temperature detection means, a contact-type temperature detection means that contacts a fixing member is generally used.
[0003]
For example, in a fixing device having a fixing member composed of a fixing roller and a heating means composed of a heater provided in the fixing member, the temperature of the fixing roller heated by the heater is set by a thermistor in contact with the surface of the fixing roller. The temperature is controlled by the contact-type temperature detecting means, and the energization to the heater is controlled based on the detection result, and the temperature is controlled so that the temperature of the fixing roller is maintained within a predetermined range. Further, the temperature of the fixing roller is also detected by the thermistor from the start of energization to the heater when the image forming apparatus is turned on until the fixing roller rises to a predetermined temperature. When an abnormality occurs, etc., abnormality monitoring control is performed to detect the abnormality.
[0004]
However, when the contact-type temperature detecting means as described above is used, foreign matter such as toner adheres to the contact portion where the temperature detecting means is in contact with the fixing member, and the surface of the fixing member is thereby damaged. There is an inevitable disadvantage that the wear is accelerated and the life of the fixing member is shortened.
[0005]
Therefore, it has been studied to use a non-contact type temperature detecting means arranged in a non-contact state with respect to the fixing member. Since the non-contact type temperature detecting means does not contact the fixing member, the surface of the fixing member can be prevented from being damaged by the temperature detecting means, or a problem in which wear is accelerated can be prevented, and the life of the fixing member can be extended. . However, if the temperature detection means itself has a low temperature, the temperature detection means cannot detect the temperature correctly in a stable state, and may erroneously detect the temperature. The temperature detecting means cannot correctly detect the temperature in a stable state unless its own temperature rises to some extent. Since the non-contact type temperature detecting means is not in contact with the fixing member, it is difficult to receive heat from the fixing member when starting up the fixing device, and the temperature of the detecting means itself is difficult to rise. For this reason, when the non-contact type temperature detecting means is used, when the fixing device is started up, there is a large difference between the actual temperature of the fixing member and the temperature detected by the non-contact type temperature detecting means. For example, it may not be possible to accurately detect an abnormality at the time of start-up. In particular, when the image forming apparatus is used in a low temperature environment (for example, in the vicinity of −10 ° C.), the temperature of the non-contact type temperature detecting means is naturally −10 ° C. when the image forming apparatus is turned on. Until the temperature of the non-contact type temperature detecting means rises to some extent, the temperature detecting means cannot correctly detect the temperature of the fixing member.
[0006]
In contrast, since the contact-type temperature detecting means is in contact with the fixing member, when the temperature of the fixing member starts to rise, the heat is immediately transmitted to the temperature detecting means, and the temperature of the temperature detecting means immediately increases. To do. For this reason, if the contact-type temperature detecting means is used, the temperature of the fixing member can be accurately detected even when the fixing device is started up. However, in the case of the contact-type temperature detecting means, the fixing member is short-lived as described above. I cannot escape the fault that makes it.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a fixing device that can eliminate both the above-mentioned drawbacks when using a contact-type temperature detecting means and the above-mentioned disadvantages when using a non-contact-type temperature detecting means, and an image having the fixing device. It is to provide a forming apparatus.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a fixing device having a fixing member heated by a heating means, a non-contact type temperature which is disposed in a non-contact state in a non-contact state within the sheet passing area of the fixing member. And a contact-type temperature detection means disposed in contact with the fixing member outside the sheet passing area of the fixing member, and the contact-type temperature detection at the start of the start-up of the fixing device. Until the set time corresponding to the initial temperature detected by the means elapses, predetermined control is performed based on the detected temperature of the contact type temperature detecting means, and after the set time elapses, the non-contact type temperature detection The energization to the heating unit is controlled based on the detected temperature of the unit to control the temperature of the fixing member, and the lower the initial temperature, the longer the set time is set. We suggest fixing device according to symptoms (claim 1).
[0012]
In order to achieve the above object, the present invention proposes an image forming apparatus having the fixing device according to claim 1 (claim 2).
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0014]
1 is a cross-sectional view showing an example of a fixing device, FIG. 2 is a front view of the fixing device 1 shown in FIG. 1 viewed from the right side, and FIG. 3 is a plan view of the fixing device 1 viewed from the direction of arrow III in FIG. It is. The fixing device 1 shown in these drawings is disposed in an image forming apparatus main body (not shown), and includes a hollow fixing roller 2 which is an example of a fixing member and an additional fixing member constituting the fixing roller 2. A pressure roller 3 and a heater 4 which is an example of a heating unit for heating the fixing roller 2 are provided. In the illustrated example, the heater 4 is disposed inside the hollow fixing roller 2, but a heating unit may be provided outside the fixing member.
[0015]
The fixing roller 2 and the pressure roller 3 are in pressure contact with each other, and during the fixing operation, the rollers 2 and 3 are rotationally driven in directions indicated by arrows in FIG. At this time, the fixing roller 2 is heated by the heat of the heater 4, the heat is transmitted to the pressure roller 3, and the pressure roller 3 is also heated. As described above, the fixing device 1 includes the fixing roller 2 which is an example of a fixing member heated by the heating unit.
[0016]
On the other hand, an image forming unit (not shown) is provided in the image forming apparatus main body, and a toner image TM is formed on a recording medium P made of transfer paper, a resin sheet, or the like in this image forming unit. For example, the toner image formed on the photoconductor of the image forming unit is transferred onto the recording medium P, whereby the toner image is formed on the recording medium P. In this way, the recording medium P carrying the unfixed toner image TM (not shown in FIG. 3) is conveyed in the direction of arrow A in a direction in which the toner image comes into contact with the fixing roller 2. It is sent to a nip portion formed by the pressure contact of the pressure roller 3 and passes there. At this time, heat and pressure are applied to the toner of the toner image TM, the toner is melted, and the toner image TM is fixed on the recording medium P. The recording medium that has passed through the fixing device 1 is discharged to a paper discharge unit (not shown).
[0017]
When the above-described fixing operation is performed, it is necessary to keep the temperature of the fixing roller 2 within a temperature range suitable for fixing the toner image. Further, in order to detect an abnormality of the heater 4 or the like even when the energization of the heater 4 is started and the fixing roller 2 rises to a predetermined temperature when the power of the image forming apparatus is turned on, the fixing roller is detected. It is necessary to detect the temperature rise state of 2. For this purpose, if the temperature of the fixing roller is controlled using either a contact-type temperature detection unit or a non-contact-type temperature detection unit, the above-described drawbacks are unavoidable.
[0018]
Therefore, in the fixing device 1 shown in the figure, two temperature detecting means, that is, a non-contact type temperature detecting means 5 spaced from the peripheral surface of the fixing roller 2 and a contact type temperature detecting means 6 in contact with the peripheral surface of the fixing roller 2. Is provided. As the temperature detection means 5 and 6, for example, a thermistor can be used. The temperature of the fixing roller 2 is controlled based on the detection results of these temperature detection means 5 and 6. Before describing the details, the non-contact type temperature detection means 5 and the contact type temperature detection means 6 are controlled. Clarify the placement status.
[0019]
The recording medium P passes through the nip portion between the fixing roller 2 and the pressure roller 3. At this time, as shown in FIG. 3, a range in which the recording medium P having the maximum width W passes through the fixing roller 2 is a sheet passing area LA of the fixing roller 2. The recording medium P does not pass through each area outside the sheet passing area LA in the longitudinal direction of the fixing roller 2, and these areas are outside the sheet passing area.
[0020]
The non-contact type temperature detecting means 5 and the contact type temperature detecting means 6 are respectively arranged at different positions in the longitudinal direction of the fixing roller 2, and the former non-contact type temperature detecting means 5 is the paper passing area LA of the fixing roller 2. The latter contact-type temperature detecting means 6 is disposed outside the sheet passing area of the fixing roller 2. In the illustrated example, the non-contact type temperature detecting means 5 is disposed at a substantially central portion in the longitudinal direction of the fixing roller 2. As described above, the fixing device includes a non-contact type temperature detecting unit disposed in a non-contact state in a non-contact state in the sheet passing region of the fixing member (the fixing roller 2 in the illustrated example), and the sheet passing through the fixing member. Contact-type temperature detection means disposed outside the area and in contact with the fixing member.
[0021]
Since the non-contact type temperature detecting means 5 is separated from the peripheral surface of the fixing roller 2, the non-contact type temperature detecting means 5 can damage the surface of the fixing roller 2 or promote its wear. Absent. The contact-type temperature detection means 6 is in contact with the surface of the fixing roller 2, but the contact point is outside the sheet passing area of the fixing roller 2. Even if the surface is slightly scratched or the surface thereof is slightly worn, the function of the fixing roller 2 is not impaired. As described above, the temperature detection means 5 and 6 can prevent a problem that the life of the fixing roller 2 is shortened.
[0022]
The temperature detection by the non-contact type temperature detection means 5 and the contact type temperature detection means 6 and the temperature control of the fixing roller 2 by this are performed as follows.
[0023]
In FIG. 4, energization of the heater 4 is started when the power of the image forming apparatus is turned on, whereby the temperature of the fixing roller 2 rises and the fixing roller 2 rises to a temperature suitable for fixing the toner image. It is explanatory drawing which shows the temperature change until it does. The solid line in FIG. 4 indicates the actual temperature X at the center in the longitudinal direction of the surface of the fixing roller, and the broken line indicates the temperature detected by the non-contact type temperature detecting means 5, that is, the detected temperature Y of the non-contact type temperature detecting means 5. Is shown. The alternate long and short dash line indicates the temperature detected by the contact-type temperature detection means 6, that is, the detected temperature Z of the contact-type temperature detection means 6. In the example shown in FIG. 4, the initial temperatures of these temperatures X, Y, and Z are all T ₀ , but these initial temperatures may be slightly different from each other. Hereinafter, the actual temperature at the center in the longitudinal direction of the fixing roller 2 will be simply referred to as the actual temperature X of the fixing roller 2 as necessary.
[0024]
When the fixing device 1 is started up, the heater 4 is fully lit, whereby the actual temperature X of the fixing roller 2, the detected temperature Y of the non-contact type temperature detecting means 5, and the detected temperature Z of the contact type temperature detecting means 6. Both rise together. At that time, since the heater 4 has a predetermined light emission distribution in the longitudinal direction, there is a difference between the temperature of the center portion in the longitudinal direction of the fixing roller 2 and the temperature of each end portion of the fixing roller. The temperature is higher. This is the difference between the temperatures X and Z indicated by the solid line and the alternate long and short dash line in FIG. Further, since the non-contact type temperature detecting means 5 is separated from the fixing roller 2, the detected temperature Y of the non-contact type temperature detecting means 5 at the time of starting up the fixing device is higher than the actual temperature X of the fixing roller 2. It is low. However, when a certain period of time elapses after the power is turned on, the temperature of the non-contact type temperature detecting means 5 itself also rises, so that the actual temperature X of the fixing roller 2 and the detected temperature Y of the non-contact type temperature detecting means 5 are The non-contact temperature detecting means 5 can detect the temperature correctly.
[0025]
Here, in the fixing apparatus of this embodiment, from the start of the start-up of the fixing device, to a temperature Z detected by the contact-type temperature detecting means 6 has reached the predetermined temperature T ₁ of the contact type temperature detecting means 6, for example, predetermined control such as abnormality monitoring control of the fixing device 1 is executed. When a more concrete example, until the temperature detected Z of the contact type temperature detecting means 6 has reached the predetermined temperature T _1, the detected temperature Z is received by the control unit (not shown), the abnormality detection to the temperature When this is done, a predetermined control is performed such that an abnormal display is made on a display unit (not shown) of the image forming apparatus or the operation of the image forming apparatus is stopped.
[0026]
Since the contact-type temperature detection means 6 is in contact with the fixing roller 2, the temperature can be detected correctly immediately after the energization of the heater 4 is started, and the abnormality of the fixing device 1 is detected based on the detected temperature Z of the contact-type temperature detection means 6. Can be detected correctly. Since the contact-type temperature detecting means 6 is located at the longitudinal end portion of the fixing roller 2, the detected temperature Z is lower than the actual temperature X in the longitudinal center portion of the fixing roller 2 as described above. However, since the difference between the temperature at the center portion in the longitudinal direction of the fixing roller and the temperature at the end portion is determined by the light emission distribution of the heater 4, the abnormality of the fixing device is determined based on the detected temperature Z of the contact-type temperature detecting means 6. It can be detected correctly.
[0027]
When the detection temperature Z of the contact type temperature detecting means 6 has reached a predetermined temperature T ₁ of the foregoing, the detection temperature Y of the non-contact type temperature sensing means 5 coincides with the actual temperature X of the fixing roller 2, or almost a Therefore, the non-contact temperature detecting means 5 is in a state where the temperature can be detected correctly. After the start-up of the fixing device 1, the temperature Z detected by the contact-type temperature detection unit 6 reaches the predetermined temperature T ₁ , and then based on the detected temperature Y of the non-contact type temperature detection unit 5. By controlling energization to the heating means (heater 4 in this example), the temperature of the fixing member (fixing roller 2 in this example) is controlled. That is, based on the detected temperature Y of the non-contact temperature detecting means 5, the actual temperature X of the fixing roller 2 is supplied to the heater 4 so as to become a target temperature T ₂ (for example, 185 ° C.) suitable for fixing the toner image. This controls on / off of the energization. In this example, the detection temperature Z of the contact type temperature detecting means 6 has completed startup of the fixing device 1 when it becomes a predetermined temperature T _1, thereafter, may perform the above-described fixing operation.
[0028]
As described above, since the temperature of the fixing roller 2 is controlled based on the detected temperature Y of the non-contact type temperature detecting unit 5 after the non-contact type temperature detecting unit 5 can detect the temperature correctly, the fixing is performed. The temperature of the roller 2 can be properly maintained within a temperature range suitable for fixing the toner image.
[0029]
When the start-up of the fixing device is completed, the fixing member composed of the fixing roller 2 and the pressure roller 3 which is the counterpart fixing member are pre-rotated to increase the temperature of the pressure roller 3 and then the fixing is performed. It is also known to be configured to perform operations. The “pre-rotation” shown in FIG. 4 means this rotation.
[0030]
In the case of adopting such a configuration, when from the start of the start-up of the fixing device 1, the temperature Z detected by the contact-type temperature detecting means 6 has reached a predetermined temperature T _1, a fixing member made of a fixing roller 2 Is pre-rotated for a predetermined time, and after completion of the pre-rotation, the energization of the heating means including the heater 4 is controlled based on the detected temperature Y of the non-contact temperature detecting means 5 to thereby control the temperature of the fixing member including the fixing roller 2. It can also be configured to control. In this case, for example, abnormality monitoring control of the fixing device 1 is performed based on the detected temperature Z of the contact-type temperature detection unit 6 until the pre-rotation is finished and the control by the non-contact type temperature detection unit 5 is started. Predetermined control can be executed.
[0031]
According to the above-described configuration, the timing at which the temperature of the fixing roller 2 starts to be controlled based on the detected temperature Y of the non-contact type temperature detecting unit 5 is later than that of the above-described configuration. After the temperature can be reliably detected normally, the control is switched to the control based on the detected temperature Y of the non-contact type temperature detecting means 5. As a result, the temperature of the fixing roller 2 can be detected more accurately and the temperature can be correctly controlled.
[0032]
Further, when the start-up of the fixing device is started, the contact-type temperature detection means 6 detects the initial temperature T ₀ shown in FIG. 4, and the detected temperature Z of the contact-type temperature detection means 6 is set in accordance with the initial temperature T _0. It is possible to switch from the control based on the control based on the detected temperature Y of the non-contact temperature detecting means 5. For example, the detected temperature of the contact-type temperature detecting means 6 when the power of the image forming apparatus is turned on, that is, the initial temperature is set to T ₀ as described above, and is calculated from the equation T = (180−T ₀ ) /1.5. When the time T is set as the set time, from the start of energization to the heater 4 when the power is turned on until the set time T elapses, for example, an abnormality of the fixing device 1 is detected based on the detected temperature Z of the contact-type temperature detecting means 6. After predetermined control such as monitoring control is executed and the set time T has elapsed since the start of energization of the heater 4, the temperature of the fixing roller 2 is set to the target temperature based on the detected temperature Y of the non-contact temperature detecting means 5. as it will be T _2, to control the energization of the oN, oFF of the heater 4. In this way, the lower the temperature of the fixing roller 2 when the image forming apparatus is turned on, the longer the set time T, during which the temperature of the non-contact type temperature detecting means 5 is increased and the non-contact type is detected. After the temperature detecting means 5 can detect the temperature correctly, the control can be switched to the control based on the detected temperature Y of the non-contact temperature detecting means 5. After the set time T has elapsed, the recording medium is started to pass through the nip portion between the fixing roller 2 and the pressure roller 3.
[0033]
As described above, the contact-type temperature detection unit from the start-up time of the fixing device 1 until the set time T corresponding to the initial temperature T ₀ detected by the contact-type temperature detection unit 6 at the start-up time elapses. For example, a predetermined control such as abnormality monitoring control of the fixing device 1 is performed on the basis of the detected temperature Z of No. 6, and after the set time T has elapsed, the heating unit (this example) is based on the detected temperature Y of the non-contact type temperature detecting unit 5 Then, the energization to the heater 4) is controlled to control the temperature of the fixing member (the fixing roller 2 in this example). At that time, the lower the initial temperature T ₀ is, the longer the set time T is set, so that the temperature control of the fixing roller 2 by the non-contact temperature detecting means 5 is correctly performed at any time of the initial temperature T _0. Can do.
[0034]
As described above, the fixing roller 2 is exemplified as the fixing member heated by the heating unit, and the example of controlling the temperature of the fixing roller 2 has been described. Configuration can be adopted. For example, the fixing member includes the pressure roller 3 shown in FIG. 1, the fixing member formed of a fixing belt or a fixing film wound around the roller, or the heating roller that heats the fixing belt or the fixing film. In order to control the temperature of a fixing member such as a fixing member, the above-described configurations can be employed. As described above, the fixing member to be temperature-detected may be a member that is heated for fixing the toner image.
[0035]
Examples of the image forming apparatus having the fixing device include an electronic copying machine, a printer, a facsimile, or an image forming apparatus having at least two of these functions.
[0036]
【The invention's effect】
According to the present invention, it is possible to prevent the fixing member from being short-lived by the temperature detecting means, and to detect the temperature of the fixing member in a stable state at all times.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of a fixing device.
FIG. 2 is a front view of the fixing device shown in FIG. 1 as viewed from the right side thereof.
FIG. 3 is a plan view seen from the direction of arrow III in FIG.
FIG. 4 is an explanatory diagram showing an example of the relationship between the actual temperature of the fixing roller and the detected temperatures of the non-contact type temperature detecting unit and the contact type temperature detecting unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing device 5 Non-contact type temperature detection means 6 Contact type temperature detection means LA Paper passing area

Claims (2)

  In a fixing device having a fixing member heated by a heating means, a non-contact type temperature detecting means arranged in a non-contact state in contact with the fixing member in a paper passing area of the fixing member, and a paper passing area of the fixing member A contact-type temperature detecting means arranged in contact with the fixing member outside, and a setting corresponding to the initial temperature detected by the contact-type temperature detecting means at the start of the start-up of the fixing device Until the time elapses, predetermined control is performed based on the detected temperature of the contact-type temperature detecting means, and after the set time has elapsed, the heating means is supplied to the heating means based on the detected temperature of the non-contact-type temperature detecting means. A fixing device that controls energization to control the temperature of the fixing member, and sets the set time longer as the initial temperature is lower.   An image forming apparatus comprising the fixing device according to claim 1.

Images