JPH1039714A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which accurately controls the drive of a fixing heater and detects an abnormal condition. SOLUTION: A fixing unit and a device main body have drawer connectors 5a and 5b, respectively. Also, the device main body is provided with an interlock switch 3a and an attachment/detachment detection switch 3b. The switches 3a and 3b are directly pressed by the projections 13a and 13b of the fixing unit, so that they are brought into on/off state. However, the projections 13a and 13b are not equal in length, the projection 13b disposed opposite to the interlock switch 3a is longer than the projection 13a disposed opposite to the attachment/detachment detection switch 3b. Thus, accompanying the accompanying/detachment of the fixing unit, the interlock switch 3a and the attachment/detachment detection switch 3b are turned on/off with specific timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a fixing unit having a heater is detachably mounted.

More specifically, the present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, etc., provided with a fixing unit using a heater.

[0003]

2. Description of the Related Art In a conventional image forming apparatus, the thermal fixing system has the following three forms.
That is, when the front door is opened, the interlock switch and the front door detection switch operate to stop the fixing temperature control, and the configuration in which the interlock switch is not provided and only the front door detection switch is provided. There is a configuration in which the front door is opened upward like a crocodile mouth, and a configuration in which an interlock switch or a door detection switch operates.

The above-mentioned configuration is such that the fixing unit itself can be pulled out from the main body in order to improve the jam-removing property, and when the fixing unit section is jammed, the fixing unit is reset from the main body. Some configurations can be processed.

On the other hand, AC switching elements (for example, triacs, SSRs, etc.) are used as driving means for controlling the temperature of the fixing heater. When the AC switching element causes element breakdown, damage in three states of full-wave / half-wave / dielectric breakdown may occur.

For example, when the SSR breaks down, the heater is not energized. However, if a short circuit occurs due to full-wave or half-wave, the full-wave / half-wave current continues to flow while AC power is supplied to the heater, and as a result, a thermo-protection element such as a thermal fuse or a thermoswitch is used. Thermal runaway occurs until the heater is disconnected from AC power.

Therefore, in order to avoid such a phenomenon, A
There is an image forming apparatus in which a means for determining the short-circuit state of the C switching element is provided to take a safety measure against the above trouble.

As a short detection method, there are a method of monitoring a voltage applied to both ends of the SSR and a method of monitoring a current actually flowing through the fixing heater. Generally, the former method is often used in terms of cost and the like.

When the former method, that is, the method of monitoring the voltage between both ends of the SSR, is adopted, if the voltage between the terminals of the SSR can be detected, it indicates that the SSR is not in a short-circuit state. On the other hand, when the voltage between the terminals of the SSR cannot be detected, it indicates that the SSR is in a short-circuit state.

However, when the control signal to the SSR serving as the fixing heater driving means is an ON signal during the fixing temperature control, it is needless to say that it is not abnormal even if the short-circuit state is detected.

[0011]

However, in the method of detecting abnormality by detecting the voltage between the terminals of the SSR,
If the fixing unit has been removed from the main unit or the interlock switch has been activated,
Since the voltage between both ends of the SR is cut off, even if the SSR is normal, it is erroneously detected as a short-circuit state.

In the case of a configuration having two interlock switches and a detection switch synchronized therewith, if the detection switch is turned on first by the interlock switch means, no AC power is supplied to both ends of the SSR. Or the processor determines that the fuser unit is set correctly and AC power is being supplied, and in fact, despite the AC power being disconnected by the interlock switch, Although the temperature control of the fixing unit is performed, the temperature of the fixing unit does not rise.
There was an inconvenience.

Accordingly, an object of the present invention is to provide
An object of the present invention is to provide an image forming apparatus configured so that drive control of a fixing heater and abnormality detection can be accurately performed.

[0014]

In order to achieve the above object, the present invention provides an image forming apparatus in which a fixing unit having a heater is detachably mounted, wherein the fixing unit is mounted on a main body of the apparatus. A fixing switch, and an interlock switch for energizing the heater when the fixing unit is mounted on the apparatus main body. With the attachment and detachment of the fixing unit, the detachment detection switch and the The interlock switch is arranged to open and close under a predetermined time relationship.
Here, when the fixing unit is mounted on the apparatus main body, the interlock switch is turned on first, and thereafter, the attachment / detachment detection switch is turned on. When the fixing unit is removed from the apparatus main body, the attachment / detachment detection switch is turned off first, and thereafter, the interlock switch is turned off.

With the attachment and detachment of the fixing unit, the attachment / detachment detection switch and the interlock switch are directly pressed by the fixing unit, thereby taking on / off states. At this time, the attachment / detachment detection switch and the interlock switch are directly pressed by respective protrusions provided on the fixing unit. By changing the protruding length of the protruding portion, it is possible to set a temporal relationship in which the attachment / detachment detection switch and the interlock switch are turned on / off.

The heater built in the fixing unit is
Electric power is supplied through drawer connectors provided on the fixing unit side and the apparatus main body side, respectively. Further, the temperature information of the heater is transmitted to the apparatus main body through the drawer connector.

The drive current of the heater is controlled by a triac or SSR connected between a drawer connector provided on the apparatus body and an AC power supply.

When the fixing unit has been installed, the voltage between the terminals of the SSR is abnormal, and the energizing signal of the SSR is in an ON state, the SSR is abnormal. to decide.

In addition, the apparatus further includes heater driving means for controlling a current flowing through the heater, and short-circuit detecting means for detecting whether or not the heater driving means is in a short-circuit state. In some cases, the detection output of the short detection means is invalidated.

In addition, there is provided heater driving means which flows to the heater, and when the attachment / detachment detection switch is in an off state, the energizing signal of the heater driving means is invalidated.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of an embodiment of the present invention, a configuration shown in FIG. 1 will be described. The fixing unit and the apparatus main body have drawer connectors 5a and 5b, respectively. In addition, an interlock switch 3a and a detachment detection switch 3b are provided on the apparatus main body side. These switches 3a and 3b are directly pressed by the protrusions 13a and 13b provided on the fixing unit side, and thereby are turned on / off.

However, the lengths of the projections 13a and 13b are not the same, and the length of the projection 13b disposed opposite to the interlock switch 3a is determined by the length of the detachment detection switch 3b.
Is longer than the protruding portion 13a that is disposed to face. Thus, as the fixing unit is attached and detached, the interlock switch 3a and the attachment / detachment detection switch 3b are turned on / off at a predetermined timing.

Ideally, the three contacts should be connected in the order of drawer connectors 5a and 5b whose main component is a mechanical set, the interlock switch 3a for connecting to an AC power source, and the third. Denotes a detachment detection switch 3b (indicating that the fixing unit is normally set in the main body and that the temperature control of the fixing device can be performed after the AC power is supplied). However, the drawer connectors 5a and 5b and the interlock switch 3a
In either case, it does not matter if the temperature control is not performed until the attachment / detachment detection switch 3b becomes effective.

When the contacts are disconnected, the order may be exactly opposite to the above.

Until the attachment / detachment detection signal becomes valid, an operation is performed so as not to perform abnormality detection relating to the fixing temperature control. Also, the drive signal of the heater drive unit is made to be invalid until the attachment / detachment detection signal becomes valid.

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory diagram showing a mechanical configuration of one embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an image forming apparatus main body. Reference numeral 4 denotes a front door portion, which in the present embodiment is a double door of a left door 4a and a right door 4b. Reference numeral 2 denotes a front door detection switch, which is configured to indicate that it is effective when both the left door 4a and the right door 4b are closed. Reference numeral 1 denotes a fixing unit. When the front door 4 is open as shown by an arrow A, the fixing unit 1
Is pulled out in the direction of arrow B, so that it can be detached from the main body.

The connection of the electric signal is configured to be connectable / disconnectable by a drawer connector for the fixing unit.
5a is a drawer connector fixed to the fixing unit 1 side.
5b is a drawer connector fixed on the main body side. In this embodiment, the drawer connectors 5a and 5b are screwed to the fixing unit and the main body, respectively, and the connection / disconnection of the drawer connectors is performed by the set / reset operation of the fixing unit 1.

Reference numeral 3a denotes an interlock switch for the fixing unit, and 3b denotes a detachment detection switch for the fixing unit. In this embodiment, a push-type switch is used in each case. Interlock switch 3
The switches a and 3b become effective when the fixing unit 1 is set. The timing will be described in detail later, but the positional relationship is determined so that the first is the drawer connector, the second is the interlock switch 3a, and finally the detachment detection switch 3b is connected.
The order of disconnection at the time of the reset operation is completely opposite to that of the above connection. First, the detachment detection switch 3b, the interlock switch 3a, and finally the drawer connector.

FIG. 1 shows an electrical configuration of the present embodiment. That is, FIG. 1 is a block diagram showing a circuit diagram around the AC power supply related to the fixing unit and electric connections of the drawer connectors 5a and 5b, the interlock switch 3a, the fixing unit attachment / detachment detection switch means, and the like. FIG. 3 is a diagram for explaining timing of connection / disconnection of switches and the like. First, means on the main body side, which is a circuit-like matter, will be described.

As described with reference to FIG. 2, the interlock switch 3a and the attachment / detachment detection switch 3b are provided on the main body 10, and the fixing unit 1 has projections 13a and 13b having different lengths for applying pressure to the two switches. There is an interlock switch 3a and a detachment detection switch 3b which are arranged on the main body side so that the switch operates in response to the protrusion, and the connection of the switch is set by the protrusions having different lengths. FIG. 3).

PLG is a power cord connected to an AC outlet. 8 is a circuit breaker,
By being in series with the PLG, the current is shut out due to overcurrent. Reference numeral 7 denotes a main switch for turning on and off the power of the entire apparatus. After the main switch 7, although only the circuits necessary for the fixing operation are shown in the figure, the circuits are actually supplied to the DC power supply means, the light source lamp means, and the like. However, since the present invention relates to the control of the fixing relation, illustration and description are omitted.

Reference numeral 6 denotes an AC switch for driving the fixing heater 9 on the fixing unit 1, and an element represented by a triac or SSR is used. In this embodiment, SSR is used. In addition, the voltage across SSR6 is input to the circuit 3 as S3, and the AC voltage across SSR cannot be detected.
When SSR 4 is valid, when SSR 6 is in the ON state in a normal state, and when SSR is in a short state with a full wave or a half wave, a signal in a short state is output from S31.

FIG. 4 shows a specific example of the circuit 3. S3
Is rectified by a diode bridge DB, and when an AC voltage is applied to S3 by a resistor, a capacitor, and a photocoupler (SSR is off), S31 falls to a low level, and S3
When the voltage is not applied to (SSR is ON), S31 becomes high level.

Reference numeral 20 in FIG. 1 denotes control means for controlling means necessary for an image forming operation in the image forming apparatus. In the present embodiment, the control means is constituted by an IC such as a microcomputer. The control unit 20 controls the units necessary for the image forming operation, realizes the image forming operation, and controls the entire apparatus by controlling the present embodiment.

Next, the connection between the fixing unit 1 and the main body will be described with reference to FIG. There are drawer connectors 5a and 5b described with reference to FIG.
Is attached to the sheet metal of the main body indicated by a thick line. Also, interlock switch 3
a, The reference of the height of the lever of the push switch of the attachment / detachment detection switch 3b is based on the main body sheet metal indicated by the black line. The attachment / detachment direction of the fixing unit 1 is indicated by an arrow B, and the right direction is the reset direction, and the left direction is the set direction.

The fixing unit 1 has a temperature detecting means 12 for detecting the temperature of a target portion used for controlling the temperature of the fixing section.
A series of a fixing heater 9 represented by a halogen heater or the like and a thermal protect 11 (hereinafter referred to as TP) represented by a thermal fuse or a thermoswitch for shutting out a drive current when a thermal runaway occurs in the fixing heater 9. Then, when connected to the drawer connector of the main body, it is electrically connected to the control means 20, and the control means 20 performs known temperature control.

The signals of S1, S2, S3 and S4 in FIG. 1 are coupled to the control means 20 via circuits 1 to 4, respectively.
S11 is a detachment detection signal, S21 is a temperature detection signal, S31 is an SSR short detection signal, and S41 is a heater drive signal.

This is the end of the description of the block circuit of FIG.

Next, referring to FIGS. 1 and 3, the interlock switch 3a when the fixing unit is set is set.
The timing relationship when the push switch of the attachment / detachment detection switch 3b is turned on will be described.

First, when the fixing unit 1 is pulled out, the direction is the rightward direction of the arrow B in FIG. 1 and the infinite direction indicated by the horizontal axis in FIG. When the fixing unit is moved in the direction in which the fixing unit is set on the main body, in FIG.
In FIG. 3, the direction is minus infinity.

When the projection 13b of the fixing unit 1 has moved to the position X, this is the point where x = 0 in FIG.
In this embodiment, first, when the fixing unit is in the reset state, the interlock switch 3a indicated by A
And the switch of the attachment / detachment detection switch 3b are both turned off.

Next, when the fixing unit 1 starts to move in the setting direction, the projection 13b of the fixing unit 1 hits the interlock switch 3a, and when the fixing unit 1 is pushed to-(ba), the interlock indicated by B in FIG. When only the switch 3a is turned on, and when the projection 13a of the fixing unit 1 is set, that is, when the lever of the detachment detection switch 3b is pressed by (-a), the interlock switch 3a remains in the on state, and the detachment detection is performed. If the switch of the interlock switch 3a and the attachment / detachment detection switch 3b is arranged so that the switch 3b is turned on, the attachment / detachment detection switch 3b is turned on after the interlock switch 3a is turned on. Timing can be made reliably.

The description of the interlock switch 3a and the attachment / detachment detection switch 3b being turned on / off at a certain timing when the fixing unit 1 enters the set / reset state is completed.

Next, based on what has been described so far,
The operation of the present embodiment will be described in more detail.

First, as for the output signal S31 from the SSR short detection means, as shown in the general flow of FIG.
Control may be performed. In the determination of step S5-1, first,
It is detected whether the fixing unit 1 is set in the main body. If it is in the reset state, the process proceeds to the next control without determining that it is abnormal. If set, step S
Move on to 5-2. In step S5-2, the determination is made based on the signal from the circuit 3 which is the SSR short detection means. If it is abnormal, the process proceeds to step S5-3, otherwise it is not abnormal, and the process proceeds to the next control. In step S5-3,
The SSR ON signal S31 is checked, and if driving is in progress, the operation proceeds to the next control without abnormality. If the apparatus is not being driven, it is abnormal. Therefore, after displaying the abnormality or the like, the safety of the apparatus is ensured by using a shut-off means provided in the main switch 7 or the like.

In FIG. 6, the above is realized by circuit logic. By checking the voltage level in S 32 according to this diagram, the same control as that shown in FIG. 5 is performed. That is, using a three-input AND gate, the SSR
The signal S33 in the state where the short-circuit detection has been activated is made by a gate, and the signal S33 is inputted by the control means 20, and the judgment is one, and it is sufficient to check whether or not it is abnormal (high level) (low level).

Next, in the control for invalidating the SSR control signal, if the state where the fixing unit 1 is slowly pulled out continues, when the current is cut off by the interlock switch 3a, as shown in FIG. Has an unstable state, an AC voltage is applied until the state becomes stable, which may adversely affect the contacts.

Therefore, the circuit shown in FIG.
With this control signal, it is possible to limit the time of the burden on the interlock switch 3a.

First, using a two-input AND gate, a detachment detection switch for discriminating whether the fixing unit 1 is in a set state, an S41 signal for controlling the SSR, and a signal S42 generated by the two-input AND gate are controlled to drive the SSR. Signal S42
By doing so, the time of the current passed by the maximum SSR 6 from the time when the detachment detection switch 3b is turned off is only T1 for a half cycle, so that the load on the interlock switch 3a can be suppressed only to the time of the maximum T1. . FIG. 8 shows the SSR 6 after the detachable switch 3b is turned off.
Represents the state of the current flowing through the fixing heater.
If the attachment / detachment switch 3b is turned off during that time, it indicates that the current indicated by oblique lines flows.

[0051] As has been described above the effect of the embodiment, the set / reset state of the fixing unit, if the configuration interlock switch 3a and attachment detection switch works, even before the door is opened, the fixing temperature Key control can be performed reliably, and even if short-circuit destruction such as SSR occurs, it works without erroneous detection. Therefore, the wait time after jam processing is reduced, and the temperature control is performed when the fixing unit is half-mounted. It is possible to avoid the occasional fixing control error.

Further, immediately before the fixing unit is artificially detached, the SSR control can be invalidated by the detachment detection switch means. In the best case, the arc is generated by the current flowing through the heater to the interlock switch 3a. Since it does not fly, the load on the interlock switch 3a can be reduced. Further, since only half a wave of the AC current is applied to the interlock switch 3a, a load is not applied as compared with the conventional configuration.

[0053]

As described above, according to the present invention, it is possible to realize an image forming apparatus configured so that the driving control of the fixing heater and the abnormality detection can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a mechanical configuration of the embodiment.

FIG. 3 is an explanatory diagram showing the operation of the present embodiment.

FIG. 4 is a circuit diagram showing details of a short detection circuit (circuit 3) in the present embodiment.

FIG. 5 is a flowchart showing an overall control procedure of the present embodiment.

FIG. 6 is a block diagram showing a hardware configuration for executing the procedure shown in FIG.

FIG. 7 shows an SS for preventing a load on the interlock switch 3a when resetting the fixing unit.
FIG. 4 is a circuit diagram for generating an R control signal.

8 is a waveform diagram showing a current flowing through a detachment detection switch and a fixing heater when the circuit of FIG. 7 is used.

[Explanation of symbols]

 Reference Signs List 1 fixing unit 2 front door detection switch 3a interlock switch 3b attachment / detachment detection switch 4a left door 4b right door 5a, 5b drawer connector 6 SSR 7 main switch 8 circuit breaker 9 fixing heater 10 device body 11 TP (thermo protect) 12 temperature Detection means Circuits 1-3 Input detection circuit Circuit 4 Control signal output circuit

Continuation of the front page (72) Inventor Kazuhiko Hirooka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hirohiko Kishimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masanobu Taira 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (12)

[Claims] An image forming apparatus in which a fixing unit having a heater is detachably mounted, wherein a detachment detection switch for detecting that the fixing unit is mounted on the apparatus main body, and wherein the fixing unit is mounted on the apparatus main body. An interlock switch for energizing the heater when the heater is mounted, wherein the attachment / detachment detection switch and the interlock switch are opened / closed in a predetermined time relationship with the attachment / detachment of the fixing unit. An image forming apparatus comprising: 2. The apparatus according to claim 1, wherein when the fixing unit is mounted on the apparatus main body, the interlock switch is turned on first, and thereafter, the attachment / detachment detection switch is turned on. Image forming apparatus. 3. The apparatus according to claim 1, wherein when the fixing unit is removed from the apparatus main body, the attachment / detachment detection switch is turned off first, and then the interlock switch is turned off. Image forming device. 4. The fixing device according to claim 1, wherein the attachment / detachment detection switch and the interlock switch are directly pressed by the fixing unit in accordance with attachment / detachment of the fixing unit, thereby taking an on / off state. Image forming apparatus. 5. The image forming apparatus according to claim 4, wherein the attachment / detachment detection switch and the interlock switch are directly pressed by respective protrusions provided on the fixing unit. 6. The image according to claim 5, wherein a temporal relationship in which the attachment / detachment detection switch and the interlock switch are turned on / off is set by changing a length of the protrusion. Forming equipment. 7. The image forming apparatus according to claim 1, wherein the heater incorporated in the fixing unit is energized through drawer connectors provided on the fixing unit side and the apparatus main body side, respectively. 8. The image forming apparatus according to claim 7, wherein the temperature information of the heater is transmitted to the apparatus main body via the drawer connector. 9. An image according to claim 7, wherein the drive current of the heater is controlled by a triac or SSR connected between a drawer connector provided on the apparatus main body side and an AC power supply. Forming equipment. 10. The SSR according to claim 9, wherein the fixing unit is already mounted, the voltage between the terminals of the SSR is abnormal, and the energizing signal of the SSR is in an ON state. An image forming apparatus that determines that an abnormality has occurred. 11. The apparatus according to claim 1, further comprising: heater driving means for controlling a current flowing through the heater; and short detecting means for detecting whether the heater driving means is in a short state. An image forming apparatus, wherein the detection output of the short detection means is invalidated when the attachment / detachment detection switch is in an off state. 12. The apparatus according to claim 1, further comprising heater driving means for flowing to the heater, wherein when the attachment / detachment detection switch is in an off state, the energizing signal of the heater driving means is invalidated. Characteristic image forming apparatus.