Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
1998-12-08
2003-04-22
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with diverse-type art device
C399S069000, C399S070000
Reexamination Certificate
active
06552304
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to a thermal fixing unit which is for use in an image forming apparatus including an electrophotographic recording apparatus such as a copying machine, facsimile and laser printer using a toner, and which thermally fixes an image transferred onto a record medium, and more particularly, relates to a method and system for controlling a temperature of the thermal fixing unit, and further to an image forming apparatus based upon that temperature control technique for the thermal fixing unit.
2) Description of the Related Art
In general, in an image forming apparatus (which will be referred hereinafter to as a printer) including an electrophotographic recording appartus such as a copying machine, a facsimile and a laser printer using a toner, a thermal fixing unit, which thermally fixes a toner image transferred onto a record medium (paper), is located along a record medium conveyance path on the downstream side of a transferring system.
FIG. 16
is an illustration of a common construction of the thermal fixing unit and a temperature control system therefor.
As shown in
FIG. 16
, a thermal fixing unit, designated at numeral
191
, is made up of a heating roller
192
containing a heat source
193
such as a halogen lamp, and a pressure roller (backup roller)
194
for pressing a record medium against the heating roller
192
.
In addition, a temperature measuring section
195
and a temperature control section
196
are provided as a temperature control system which takes charge of controlling a surface temperature of the heating roller
192
. The temperature measuring section
195
is for measuring the surface temperature of the heating roller
192
, and is constructed with a thermo-sensitive device such as a thermister, while the temperature control section
196
is for executing the ON (lights)/OFF (lights-out) -control for the heat source
193
.
Secondly, referring to the flow chart (steps S
1
to S
8
) of
FIG. 17
, a description will be made hereinbelow of a prior control operation in a printer including the aforesaid thermal fixing unit
191
, and more specifically, of an operation to be taken for when an operational variation takes place from an ordinary printing operation to a Consecutive printing operation or a stand-by mode.
After the completion of a predetermined initializing operation, upon receipt of print data from a host unit such as a host computer, a printer starts to print the print data onto a paper sheet (record medium) (step S
1
). At this time, as will be described herein later, the surface temperature of the heating roller
192
in the thermal fixing unit
191
is controlled by the temperature control section
196
in accordance with various kinds of printing conditions or requirements, for example, whether or not the printer is in a consecutive printing operation and whether or not being in a starting operation (intermittent printing; the first printing to be done when the printing resumes from the stand-by mode).
After the completion of the printing of the print data from the host unit, in the case of receiving the next print data before a paper discharge sensor (not shown) detects a rear end portion of the paper sheet (YES route from step S
2
), the temperature control section
196
sets the desired temperature of the heating roller
192
to a target temperature to be controlled for consecutive printing which will be mentioned herein later (step S
3
), before a printing operation starts (step S
1
). Incidentally, the aforesaid paper discharge sensor is designed to sense the fact that the paper sheet rear end portion passes through the thermal fixing unit
191
.
On the other hand, in the case that the reception of the next print data does not take place before the paper discharge sensor detects the paper sheet rear end portion (NO route from step S
2
), the temperature control section
196
gets the controlled target temperature for the beating roller
192
to a tempetature Tsb for a stand-by mode which will be mentioned herein later (step S
4
). Incidentally, in the step S
4
, in order to prevent the excessive heating resulting from the event that the pressure roller
194
comes into contact with the heating roller
192
, the controlled target temperature by the heating roller
192
is merely set to the stand-by mode temperature Tsb lower than the controlled target temperature for the regular printing, which does not signify the actual advancement to the stand-by mode.
Following this, a decision is made as to whether the next print data is received or not (step S
5
), and a further decision is made on whether the time t elapsed after the paper sheet rear end portion passes by the paper discharge sensor of the thermal fixing unit
191
exceeds a predetermined time (for example, 5 seconds) (step S
6
).
If the reception of the next print data occurs before the time t exceeds 5 seconds (NO route from step S
6
and YES route from step S
5
), the operational flow advances to the step S
3
to continue the printing in a consecutive printing mode.
On the other hand, if no transmission of the next print data takes place although the time t exceeds 5 seconds (NO route of step S
5
and YES route of step S
6
), the printer stops in accordance with a given stop sequence, and issues a stop command or the like to stop the rotation of its photosensitive drum (step S
7
) and then goes into the stand-by mode to wait for the next print data (print instruction) from the host unit (step S
8
).
Meanwhile, in case where the host unit such as a host computer makes a request for printing to a printer, the print data is evolved in the host unit or in a controller of the printer, and then transferred, together with a print instruction, from the controller to a mechanism control section within the printer. At this time, since the evolution or development time of the print data depends upon printing patterns, the evolution can be shorter or longer than the time required for the preceding printing (preceding print time).
In the case of accomplishing the printing of a plurality of identical patterns, or in the case that a print data evolution time is shorter than the preceding print time as mentioned above, for example as shown in
FIG. 18A
, the printer implements the consecutive printing while conveying paper sheets at its maximum print speed and at the minimum interval (distance) between the paper sheets.
FIG. 18A
is an illustration of an example of an output of a paper discharge sensor attainable when the printer conducts the consecutive printing while conveying the paper sheets at the maximum print speed and at the minimum interval.
On the other hand, if the next printing instruction (print data) does not arrive in the printer because of no completion of the evolution of the print data, although a predetermined time (for example, 5 seconds) elapses, as mentioned before with reference to
FIG. 17
, the printer stops the operations of the rotating system such as the photosensitive drum in accordance with a given stop sequence, and proceeds to the stand-by mode to go into the ready condition until receiving the next printing instruction. Thereafter, when the printing instruction comes, the printing is done in a predetermined printing start sequence. In an extreme example, in the case that a printing instruction comes immediately after a predetermined stand-by time elapses, after once stopping the printing in accordance with a stop sequence, the printer immediately resumes the printing through a restart sequence.
Furthermore, even in the case that the print data evolution time exceeds the preceding print time, for example as shown in
FIG. 18B
, the printer waits for the arrival of the next printing instruction by a predetermined time (for example, 5 seconds) after the completion of the preceding printing while operating the rotational drive system such as the rollers
192
,
194
of the fixing unit
191
, thereby surely suppressing the decrease in throughput.
FIG. 18B
is an illustration of an outp
Hirose Kazunori
Matsuya Takashi
Armstrong Westerman Hattori McLeland & Naughton LLP
Fuqua Shawntina
Walberg Teresa
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