JPH0988U - Recording device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To solve the problem that toner adheres to a photosensitive drum at the end of copy operation or printer operation.
It is to provide a recording device which can be solved by one high-voltage generating device. SOLUTION: A high voltage output circuit 9 for supplying an output to a charger of a recording device and an intermediate voltage output circuit for supplying a developing bias voltage to a developing means are connected to an output side of a transformer 7. The switching means 31 has a first output mode in which the high voltage output circuit outputs a voltage equal to or higher than the discharge start voltage of the charger and the intermediate pressure output circuit outputs intermediate pressure, and a discharge start voltage of the charger. A second output mode in which a smaller voltage is output and the intermediate pressure output circuit outputs an intermediate pressure is selectively switched. The switching means is controlled to the second output mode for at least a predetermined time after the end of the first output mode.

Description

[Detailed description of the device]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a recording device, and in particular, has a high-voltage power supply device capable of outputting at least two types of voltage levels output from a plurality of DC high-intermediate voltage circuits with one device. Recording device

[0002]

[Prior art]

 An example of a conventional high voltage power supply device will be described with reference to FIG. In the figure, 1 is a reference voltage generating means, 2 and 3 are resistors, 4 is a comparator, 5 is a drive control circuit, 6 is a switching transistor, and 7 is a transformer. Further, 8 is a rectifier circuit of the intermediate pressure generating circuit, 9 is a constant voltage output circuit of the intermediate pressure generating circuit, and the intermediate pressure output from the constant voltage output circuit is the developing bias and the chatch up roll. ) Used for voltage, chute bias, etc. Further, 10 is a rectifying circuit of a high voltage generating circuit, 11 is a charging corotron, and the high voltage output from the high voltage rectifying circuit 10 is applied to a charging corotron 11. The high voltage is fed back to the connection point of the resistors 2 and 3 through the monitor resistor 12.

The high-voltage power supply device having the above configuration controls the input of the transformer 7 according to the high-voltage output monitor voltage obtained via the monitor resistor 12, and outputs the high voltage output from the secondary side of the transformer 7. The output and the intermediate pressure output are controlled.

FIG. 6 shows a schematic view of the device arranged around the drum. Reference numeral 21 is a photosensitive drum, 22 is an exposure position, 23 is a developing roll, 24 is a chatchup roll, 25 is a paper conveyance guide, 26 is a transfer corotron, and 27 is a peeling corotron. Further, a is a terminal for the charging corotron to which the high voltage is applied, and b, c and d are terminals for applying the developing bias, the chatchup roll voltage and the cheat bias to which the intermediate pressure is applied, respectively. .

Now, when a copying or printing operation is executed in a recording device such as a copying machine or a printer including the high-voltage circuit having the configuration shown in FIG. 5, for example, a sheet of paper is provided on a paper conveyance path. The input voltage Vin shown in FIG. 5 is applied at an appropriate timing with reference to the time point when the intermediate pressure is sent from the intermediate voltage generating circuit and the high voltage generating circuit. As a result, the intermediate pressure and the high pressure are applied to each of the above-mentioned devices around the photosensitive drum, and a predetermined copy or print operation is performed.

When the operation proceeds and the last copy or print is completed, the input voltage Vin is turned off at a predetermined timing. Then, the intermediate pressure and the high pressure are reduced, and the series of operations is completed.

[0007]

[Problems to be solved by the device]

 Next, with reference to FIG. 7, the operation of the (n-1) th sheet and subsequent sheets when n sheets are copied will be described. As shown in (5) of the figure, the on / off signal is kept on until time t7 when the nth copy is completed, and therefore the applied voltage (1) of the charging corotron 11 is also at this time t7. Is being applied up to.

If the (n-1) th copy is completed at time t1, the original information is interrupted until time t2 when the nth copy is started. It goes to H (high) level as shown in FIG. Next, when the nth copy is started, the drum charge amount in the exposure section 22 changes in accordance with the document information during the nth copy period t2 to t5. After the time t5 when the copying of the nth sheet is completed, the document information is not received, so the drum charge amount in the exposure unit 22 becomes the H level, and this continues until the time t8. Here, the times t7 to t8 correspond to the rotation time from the charging corotron position of the photosensitive drum to the exposing portion position.

Next, the developing bias shown in FIG. 3C will be described. The exposure unit is operated between the (n-1) th copy and the nth copy (time t1 to t2). When the drum surface that has passed through 22, that is, the original information interruption portion comes to a position facing the developing device, the timing at which the original information interruption portion comes to the developing device in order to prevent the toner from being attached thereto The developing bias is set to the H level in accordance with (time t3 to t4). Also, when the n-th copy is completed, it is similarly set to the H level from time t6 to time t7. When the on / off signal is turned off, the H level changes to the L level at the same time. Therefore, the toner adhesion amount at the developing portion becomes 0 at the document information interruption portion as shown in FIG. 4 (4), and unnecessary toner does not adhere to the photosensitive drum.

However, after the copying of the nth sheet is completed, the H level of the developing bias becomes the L level at the same time when the on / off signal is turned off, so that the photosensitive drum is exposed during the time t7 to t8. There is a problem that unnecessary toner adheres. In order to solve this problem, if the medium voltage generation circuit and the high voltage generation circuit are separately powered, there is a problem that the device becomes large and the cost of the power supply circuit becomes high.

An object of the present invention is to provide a recording apparatus provided with a high voltage power supply means capable of solving the above-mentioned problems of the prior art.

[0012]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a first high voltage output circuit of a high voltage power supply means of a recording apparatus that outputs a voltage equal to or higher than a discharge start voltage of a charger and an intermediate voltage output circuit outputs an intermediate pressure. And a second output mode in which the high-voltage output circuit outputs a voltage lower than the discharge start voltage of the charger and the intermediate-voltage output circuit outputs the intermediate pressure. The switching means is characterized in that the switching means is controlled to the second output mode for at least a predetermined time from the end of the first output mode.

In the first output mode, the high-voltage power supply means outputs a high voltage of a magnitude that discharges the charging corotron from the high-voltage output circuit, and outputs a medium-voltage voltage of the medium-voltage output circuit. Output from. Then, in the second output mode which is switched for at least a predetermined time from the end of the first output mode, the high voltage output circuit outputs a small voltage that does not discharge the charging corotron, and the intermediate voltage output circuit outputs the voltage. , Outputs medium voltage voltage. Therefore, it is possible to eliminate the problem that unnecessary toner adheres to the photosensitive drum after the copying operation, the printer operation, and the like are completed.

[0014]

[Embodiment of the invention]

 Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a circuit diagram of an embodiment of a high voltage power supply means used in the recording apparatus of the present invention. In the figure, 31 is a transistor, 32 to 34 are resistors, and other symbols are the same as or equivalent to those in FIG. The present embodiment is characterized in that the reference voltage Vx applied to the + terminal of the comparator 4 can be set to two voltage values Vx1 and Vx2 by turning on and off the transistor 31.

The operation when the transistor 31 is on / off controlled will be described with reference to FIG. Now, when an L level signal is applied to the base of the transistor 31 (first output mode) while the on / off signal is on, the transistor 31 is turned off and the + terminal of the comparator 4 is turned on. The reference voltage Vx applied to the high voltage becomes a high reference voltage Vx1 as shown. Then, the comparator 4 outputs an H level signal when a potential lower than the reference voltage Vx1 is input to its negative terminal, and the drive control circuit 5 controls the switching transistor 6 so that its ON period becomes longer. . As a result, a large amount of energy is stored in the primary winding of the transformer 7, and a large flyback voltage is generated on its secondary side when the switching transistor 6 is turned off. Therefore, the high voltage generation circuit outputs a voltage VH1 larger than the discharge start voltage Vc1 of the charging corotron 11. Further, the intermediate voltage generating circuit outputs a voltage VM1 which is higher than the minimum voltage Vc2 required to operate the intermediate voltage circuit.

When the base voltage of the transistor 31 is changed to the H level at the time T1 (second output mode), the transistor 31 is turned on and the reference voltage Vx is low as shown in the figure. The reference voltage becomes Vx2. Then, the comparator 4 outputs an L level signal when a voltage higher than the reference voltage Vx2 is input to its negative terminal, and the drive control circuit 5 causes the switching transistor 6 to have its off period longer than that in the above case. To control. As a result, a smaller amount of energy is stored in the primary winding of the transformer 7, and a flyback voltage is generated on its secondary side when the switching transistor 6 is turned off. Therefore, a voltage VH2 smaller than the discharge start voltage Vc1 of the charging corotron 11 is output from the high voltage generation circuit. On the other hand, the medium voltage generation circuit outputs a voltage VM2 larger than the minimum voltage Vc2 required to operate the medium voltage circuit. Further, when the on / off signal is turned off, the input voltage Vin applied to the high-voltage power supply means becomes 0, so that the voltages output from the high-voltage generating circuit and the intermediate-voltage generating circuit also become 0.

Next, the operation when copying is performed using the high-voltage power supply means of this embodiment in a copying machine will be described with reference to FIG. FIG. 3 shows a time chart similar to that of FIG. The difference between FIG. 3 and FIG. 7 is that the on / off signal is turned off at time t8 and a signal that is at H level is applied to the base of the transistor 31 for a period from time t7 to t8. .

According to the present embodiment, since the L-level voltage is applied to the base of the transistor 31 until time t7, the same operation as in the conventional case is performed, and the high voltage generating circuit and the medium voltage generating circuit operate. , The voltage is generated until time T1 in FIG. That is, the high-voltage generating circuit generates a voltage VH1 that is higher than the discharge start voltage of the charging corotron 11, and the intermediate-voltage generating circuit generates a voltage VM1 having a magnitude that prevents toner from adhering to the photosensitive drum 21. As a result, the charging corotron 11 performs a predetermined discharge, and the developing roll 23 operates so that the toner does not adhere to the document information interruption portion.

Now, at time t7, when an H level voltage is applied to the base of the transistor 31, the high voltage generating circuit and the medium voltage generating circuit generate the voltage of the magnitude shown at time T1 to T2 in FIG. To occur. That is, the high voltage generating circuit generates a voltage VH2 smaller than the discharge start voltage of the charging corotron 11, and the medium pressure generating circuit generates a voltage VM2 having a magnitude that prevents toner from adhering to the photosensitive drum 21. As a result, the charging corotron 11 stops discharging and the developing roll 23 operates so that toner does not adhere during the period from time t7 to t8.

As a result of the above operation, the toner adhesion amount at the developing portion on the photosensitive drum 21 becomes 0 after time t7 as shown in FIG. 3 (4), which is unnecessary. It is possible to prevent the toner from adhering to the photosensitive drum.

FIG. 4 shows a second embodiment of the present invention. This embodiment differs from the first embodiment in that a series connection circuit of a transistor 35 and a resistor 36 is connected in parallel with the resistor 32. According to this embodiment, when an L level signal is applied to the base of the transistor 35, the high voltage generating circuit and the medium voltage generating circuit obtain the high voltage output and the medium voltage output shown in the periods T1 to T2 of FIG. On the other hand, when an H level signal is applied to the base of the transistor 35, the high voltage generating circuit and the medium voltage generating circuit obtain the high voltage output and the medium voltage output before the time T1 in FIG. In other words, the level of the control signal applied to the base of the transistor 35 can be reversed as compared with that of the first embodiment.

Although the reference voltage Vx applied to the + terminal of the comparator 4 is switched by turning on / off the transistors 31 and 35 in the above embodiment, the present invention is not limited to this. Instead, another switching element may be used for switching.

[0023]

[Effect of the invention]

 As described above, according to the recording apparatus of the present invention, the high voltage capable of discharging the charged corotron and the first output mode capable of simultaneously generating the developing bias voltage, and the large size that does not discharge the charged corotron. A switching means for selectively switching between a high output voltage and a second output mode capable of simultaneously generating a developing bias voltage. The switching means is configured to switch the second output mode for at least a predetermined time from the end of the first output mode. Since the output mode is controlled to the second output mode, there is an effect that it is possible to solve the problem that the toner adheres to the photosensitive drum at the end of the copy operation or the printer operation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation.

FIG. 3 is a time chart showing a voltage applied to a device around a photosensitive drum such as a copying machine, a drum charge amount, and a toner adhesion amount when the high-voltage power supply unit of the embodiment is used as a power source for the device. is there.

FIG. 4 is a circuit diagram of a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional device.

FIG. 6 is a schematic configuration diagram showing devices arranged around a photosensitive drum.

FIG. 7 is a time chart showing a voltage applied to the device by a conventional high-voltage power supply device, a drum charge amount, and a toner adhesion amount.

[Explanation of symbols]

4 ... Comparator, 5 ... Drive control circuit, 6 ... Switching transistor, 31, 35 ... Transistor

Claims (1)

[Utility model registration claims] 1. A photoconductor, a charging device for uniformly charging the photoconductor, an exposing means for exposing the photoconductor uniformly charged by the charging device according to document information, and an exposing means. Developing means for developing the electrostatic latent image to form a toner image, a high voltage output circuit for supplying an output to the charger to the output side of one high voltage transformer, and a developing bias voltage for the developing means. By controlling the input of the high-voltage transformer by connecting a medium-voltage output circuit and comparing the high-voltage output monitor voltage with a reference voltage, the output voltages of the high-voltage output circuit and the medium-voltage output circuit are controlled. And a first output mode in which the high voltage output circuit outputs a voltage equal to or higher than a discharge start voltage of the charger and the intermediate pressure output circuit outputs an intermediate pressure. , The high voltage output A switching means for selectively switching between a second output mode in which the path outputs a voltage lower than the discharge start voltage of the charger and the intermediate pressure output circuit outputs an intermediate pressure; and the switching means comprises: The recording apparatus is controlled to the second output mode for at least a predetermined time from the end of the first output mode.