JPH08258317A - Powder jet image-forming apparatus - Google Patents

Abstract

PURPOSE: To collect an unnecessary developer not used for printing and supply a fresh developer at all times, by setting voltages to be impressed to a first and a second electrodes and a developer feed roller to satisfy a specific relation in a developer recovery mode and a developer supplementation mode. CONSTITUTION: A toner is supplied to the side of a first electrode 21 by an electric field between a developer (toner) feed roller 1 and the first electrode 21 in a printing head 2. The toner is allowed to pass through a toner penetration hole by an electric field between the first and a second electrodes 21 and 22, and blown/printed to a recording paper P transferred via a base roller (base electrode) 3 and a fixing roller 4. Supposing that voltages impressed to the electrodes 21, 22 and roller 1 are respectively V1R, V2R and VSR, the apparatus controls to impress a constant voltage to satisfy V2R<V1R<VSR if the toner is charged with a negative polarity in a developer recovery mode and V2R<V1R <VSR in a developer supplementation mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder jet image forming apparatus.

[0002]

2. Description of the Related Art The applicant has already developed a powder jet image forming apparatus as shown in FIG. This powder jet image forming apparatus has a print head 2 that controls passage of toner charged with a predetermined polarity, for example, negative polarity.
A toner supply roller 1 for supplying toner to the print head 2, and the toner passing through the print head 2 on the recording paper P.
A base roller 3 for transferring the toner onto the recording paper P and a fixing roller 4 for fixing the toner transferred onto the recording paper P onto the recording paper P are provided.

As shown in FIGS. 8 and 9, the print head 2 includes an insulating substrate 20, a plurality of first electrodes 21 on the surface of which the toner supply roller 1 of the insulating substrate 20 is formed, and an insulating substrate 20. The base roller 3 is provided with a plurality of second electrodes 22 formed on the surface of the saw. A plurality of first electrodes 21
Further, the plurality of second electrodes 22 form a matrix electrode part. Each first electrode 21 and each second electrode 22
A toner passage hole 23 penetrating the print head 2 is formed at each intersection position with and.

An on-voltage (for example -100V) and an off-voltage (for example + 300V) are selectively applied to each first electrode 21. Each second electrode 22 has an on-voltage (for example, 0 V) and an off-voltage (for example, -200 V).
V) and are selectively applied. FIG. 10 shows each first electrode 2
1 shows changes in applied voltage V1-0 to V1-7.
As shown in FIG. 10, each of the first electrodes 21 is subjected to dimic scan control, and the applied voltage is sequentially turned on at predetermined unit time intervals. Then, only when the applied voltage to both the first electrode 21 and the second electrode 22 is the on-voltage, the toner passes through the toner insertion hole 23 at the intersection thereof, and the dot printing is performed.

The recording paper P is moved by the base roller 3 in a direction orthogonal to the first electrode 21 (direction indicated by arrow A in FIG. 8).
Be transported to. For the base roller 3, for example, +50
A voltage of 0V is applied. The toner supply roller 1 is grounded and its surface potential is 0V.

The print head 2 is provided with an ultrasonic vibrator 50 for applying ultrasonic vibration to the print head 2 to prevent the toner insertion hole 23 from being clogged with toner.

[0007]

In the above powder jet image forming apparatus, the toner supply roller 1 and the first electrode 2 are provided.
The toner is supplied from the toner supply roller 1 side onto the first electrode 21 by the electric field between the toner supply roller 1 and the first electrode 21. Then, by the electric field between the first electrode 21 and the second electrode 22, the first electrode 2
The toner accumulated on the sheet 1 passes through the toner insertion hole 23 and is transferred onto the recording paper.

By the way, from the toner supply roller 1 side to the first
Not all of the toner supplied on the electrode 21 is used for printing, so unnecessary toner stays on the first electrode 21. If the amount of toner staying on the first electrode 21 becomes excessive, the toner insertion hole 23 will be clogged and uneven density will occur. Further, when the toner stays on the first electrode 21 for a long time, there is a problem that the charge amount of the staying toner changes due to frictional charging due to vibration, which causes image deterioration.

The present invention provides an image forming apparatus capable of recovering unnecessary developer that has not been used for printing and is always supplied with fresh developer, which is the developer supplied onto the first electrode. With the goal.

[0010]

A first powder jet image forming apparatus according to the present invention comprises a print head, a developer supply roller and a base electrode arranged so as to sandwich the print head, and the print head comprises: An insulating layer, a plurality of first electrodes formed on the surface of the insulating layer on the side of the developer supply roller, and a plurality of second electrodes formed on the surface of the insulating layer on the side of the base electrode. A matrix-shaped electrode portion is formed on the print head by the second electrode, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode in the print head. The developer is supplied from the developer supply roller side to the first electrode side by the electric field between the first electrode and the developer supplied to the first electrode side is developed by the electric field between the first electrode and the second electrode. Pow passing through the agent insertion hole In over jet image forming apparatus,
As an operation mode, in addition to the printing mode for printing, a developer collecting mode for collecting the developer each time the printing in the printing mode ends and a developer before the printing in the printing mode starts A developer replenishment mode for replenishing the print head is provided, where the voltage applied to the first electrode is V1R, the voltage applied to the second electrode is V2R, and the voltage applied to the developer supply roller is VSR. When the developer is negatively charged, a constant voltage satisfying the relationship of V2R <V1R <VSR is applied to the first electrode, the second electrode and the developer supply roller in the developer recovery mode, V2R <V1R> VSR in developer replenishment mode
When a constant voltage satisfying the relationship is applied to each of the first electrode, the second electrode and the developer supply roller and the developer is positively charged, V2R is applied in the developer recovery mode.
A constant voltage satisfying the relationship of>V1R> VSR is applied to the first electrode, the second electrode and the developer supply roller, respectively, and a constant voltage satisfying the relationship of V2R> V1R <VSR is applied to the first electrode, the second electrode and the developer supply roller. It is characterized in that it is applied to each of the two electrodes and the developer supply roller.

For example, when printing of one page is completed, first, the operation mode is set to the developer collecting mode for a predetermined period, and then the operation mode is set to the developer replenishing mode for a predetermined period.

A second powder jet image forming apparatus according to the present invention is provided between a print head, a developer supply roller and a base electrode provided so as to sandwich the print head, and between the print head and the developer supply roller. And a plurality of first electrodes formed on the surface of the insulating layer on the developer supply roller side,
A plurality of second electrodes formed on the surface of the insulating layer on the base electrode side, and a matrix-shaped electrode portion is formed in the print head by the first electrode and the second electrode. A developer insertion hole is formed at each intersection with the second electrode, and the electric field between the developer supply roller and the first electrode supplies the developer from the developer supply roller side to the first electrode side. In the powder jet image forming apparatus in which the developer supplied to the first electrode side passes through the developer insertion hole by the electric field between the first electrode and the second electrode, the operation mode is the print mode for printing. In addition, a developer collecting mode for collecting the developer each time the printing in the print mode is completed, and a developer replenishing mode for supplying the developer to the print head before the printing in the print mode is started. Set up If the applied voltage to the first electrode is V1R, the applied voltage to the second electrode is V2R, the applied voltage to the developer supply roller is VSR, and the applied voltage to the grid electrode is VGR, the developer is negative. In the developer collecting mode, V2R <V1R <V
A constant voltage satisfying the relationship of GR <VSR is applied to each of the first electrode, the second electrode and the developer supply roller, and a constant voltage satisfying the relationship of V2R <V1R>VGR> VSR in the developer replenishing mode is the first electrode, When the developer is positively charged by being applied to the second electrode and the developer supply roller, respectively, V2R> V1 in the developer recovery mode.
The constant voltage satisfying the relation of R>VGR> VSR is the first electrode,
Applied to the second electrode and the developer supply roller,
V2R> V1R <VGR <VSR in developer replenishment mode
The constant voltage satisfying the relation of is applied to the first electrode, the second electrode and the developer supply roller, respectively.

An ultrasonic transducer is provided in the print head,
It is possible to drive the ultrasonic vibrator at a fixed cycle in the print mode, and to drive the ultrasonic vibrator in the developer recovery mode so that the average value of the vibration energy by the ultrasonic vibrator becomes larger than that in the print mode. preferable.

When the voltage applied to the base electrode is VBR, when the developer is negatively charged, a constant voltage satisfying the relationship of VBR <V2R is applied to the base electrode in the developer recovery mode, When the developer is positively charged, it is preferable to apply a constant voltage satisfying the relationship of VBR> V2R to the base electrode in the developer collecting mode.

[0015]

In the first powder jet image forming apparatus according to the present invention, in addition to the print mode for printing as the operation mode, the developer recovery for recovering the developer each time the printing in the print mode is completed A mode and a developer replenishment mode for replenishing the print head with the developer before printing in the print mode is started.

The voltage applied to the first electrode is V1R, the voltage applied to the second electrode is V2R, and the voltage applied to the developer supply roller is VSR. When the developer is negatively charged, V2R <V1R <VSR in the developer recovery mode
A constant voltage satisfying the relationship is applied to the first electrode, the second electrode and the developer supply roller, respectively. Further, in the developer replenishing mode, constant voltages satisfying the relationship of V2R <V1R> VSR are applied to the first electrode, the second electrode and the developer supply roller, respectively.

When the developer is positively charged, a constant voltage satisfying the relationship of V2R>V1R> VSR is applied to the first electrode, the second electrode and the developer supply roller in the developer recovery mode. To be done. Further, in the developer replenishment mode, constant voltages satisfying the relationship of V2R> V1R <VSR are applied to the first electrode, the second electrode and the developer supply roller, respectively.

In the second powder jet image forming apparatus according to the present invention, in addition to the print mode for printing as the operation mode, the developer recovery for recovering the developer each time the printing in the print mode is completed A mode and a developer replenishment mode for replenishing the print head with the developer before printing in the print mode is started.

The voltage applied to the first electrode is V1R, the voltage applied to the second electrode is V2R, the voltage applied to the developer supply roller is VSR, and the voltage applied to the grid electrode is VGR.
When the developer is negatively charged, a constant voltage satisfying the relationship of V2R <V1R <VGR <VSR is applied to the first electrode, the second electrode and the developer supply roller in the developer recovery mode. It Further, in the developer replenishing mode, constant voltages satisfying the relationship of V2R <V1R>VGR> VSR are applied to the first electrode, the second electrode and the developer supply roller, respectively.

When the developer is positively charged, V2R>V1R>VGR> in the developer recovery mode.
A constant voltage satisfying the relationship of VSR is applied to each of the first electrode, the second electrode and the developer supply roller. Further, in the developer replenishing mode, constant voltages satisfying the relationship of V2R> V1R <VGR <VSR are applied to the first electrode, the second electrode and the developer supply roller, respectively.

[0021]

Embodiments of the present invention will be described below with reference to FIGS.

(1) Description of the configuration of the powder jet image forming apparatus.

FIG. 1 shows the structure of a powder jet image forming apparatus.

In this powder jet image forming apparatus,
The recording paper P is guided by the guide plate 5, passes through the base roller (base electrode) 3 and the fixing roller 4, and is discharged. The print head 2 is disposed below the base roller 4.

Toner is supplied to the print head 2 from the toner supply unit 10. The toner is assumed to be negatively charged in this example.

The toner supply unit 10 includes a casing 11 filled with toner, a stirring pad 6 rotatably arranged in the casing 11, and a toner supply roller 1 rotatably arranged in the casing 11. . Stirring pad 6
The toner supply roller 1 is driven to rotate in a predetermined direction by a motor (not shown).

As shown in FIGS. 2 to 4, the print head 2 includes an insulating substrate (insulating layer) 20 and a plurality of first electrodes 21 formed on the surface of the insulating substrate 20 on the toner supply roller 1 side.
And a plurality of second electrodes 22 formed on the surface of the insulating substrate 20 on the base roller 3 side. Multiple first electrodes 2
The one and the plurality of second electrodes 22 form a matrix electrode. Each first electrode 21 and each second electrode 22
A toner passage hole 23 penetrating the print head 2 is formed at each intersection position with and.

The print head 2 is provided with an ultrasonic transducer 50 for applying ultrasonic vibration to the print head 2 to prevent the toner insertion hole 23 from being clogged with toner.

A grid electrode 30 is arranged between the print head 2 and the toner supply roller 1. The grid electrode 30 is a thin metal plate in which a plurality of slits 31 extending in the lengthwise direction of the second electrode 22 are formed at equal intervals in the lengthwise direction of the first electrode 21. Both sides of the grid electrode 30 are provided with the print head 2 via the spacer 40.
The grid electrode 30 is attached to the print head 2 by being fixed to the print head 2.

The reason why the grid electrode 30 is provided is as follows. That is, the toner is supplied from the toner supply roller 1 to the print head 2 by the action of the electric field (toner supply electric field) generated by the difference between the potential of the toner supply roller 1 and the potential of the first electrode 21. However, since the outer surface of the toner supply roller 1 is a curved surface, the distance between each first electrode 21 of the print head 2 and the outer surface of the toner supply roller 1 is different. Therefore, the toner supply electric field in the vicinity of each first electrode 21 varies. Therefore,
The grid electrode 30 is provided in order to make the toner supply electric field near each of the first electrodes 21 constant.

The recording paper P is moved by the base roller 3 in a direction orthogonal to the first electrode 21 (direction indicated by arrow A in FIG. 2).
Be transported to.

The operation modes of this image forming apparatus include a printing mode for printing on a page-by-page basis, a toner collection mode for collecting toner in the toner supply unit 10, and a toner collection mode for the first electrode 21 side. There is a toner replenishment mode for replenishment. A process in the toner collecting mode and a process in the toner replenishing mode are performed between the end of printing one page in the print mode and the start of printing the next one page. That is, the operation mode is set to the toner collecting mode for a certain period immediately after the printing of one page is completed in the print mode. After the processing in the toner collecting mode is completed, the operation mode is set to the toner replenishing mode for a certain period.

The toner collecting mode is provided for collecting the toner excessively accumulated on the first electrode 21, the toner accumulated in the toner insertion hole 23, and the like to the toner supply unit 10. The toner replenishment mode is provided to compensate for the shortage of the amount of accumulated toner on the first electrode 21 immediately after the toner recovery mode.

(2) Description of operation in print mode

FIG. 5 shows changes in the potential of each part in the print mode.

The toner supply roller 1 is applied with a periodic voltage having two values, for example, 0V and + 200V.

The grid electrode 30 has, for example, +50.
A periodic voltage having two values of V and + 150V is applied.

An on-voltage (for example -100V) and an off-voltage (for example + 300V) are selectively applied to each first electrode 21. The first electrodes 21 are controlled by the dimic scan, and the applied voltage is sequentially turned on at predetermined unit time intervals.

An on-voltage (for example, 0 V) and an off-voltage (for example, -200 V) are selectively applied to each second electrode 22 based on image information. And the first
Only when the applied voltage to both the electrode 21 and the second electrode 22 is the ON voltage, the toner passes through the toner insertion hole 23 located at the intersection of these electrodes, and dot printing is performed.

For the base roller 3, for example, +200
A constant voltage of V is applied.

The ultrasonic transducer 50 is on / off controlled in synchronization with the dynamic scanning of the first electrode 21.

When the potential of the grid electrode 30 is higher than the potential of the toner supply roller 1, the toner moves from the toner supply roller 1 to the grid electrode 30 side, and the grid electrode 30
Passing through the slit 31 of. In addition, when the potential of the first electrode 21 is higher than the potential of the grid electrode 30 (first electrode 21
When an off voltage is applied to the grid electrode 3
The toner that has passed through the 0 slit 31 is supplied to the first electrode 21, and the toner is deposited on the first electrode 21. At this time, since the distance between each first electrode 21 and the grid electrode 30 is constant, the toner supplying electric field generated between each first electrode 21 and the grid electrode 30 becomes uniform.

When the potential of the second electrode 22 is higher than the potential of the first electrode 21 (when the ON voltage is applied to both electrodes), the toner deposited on the first electrode 21 has the toner insertion hole 23. Pass through. Then, due to the potential difference between the second electrode 22 and the base roller 3, the toner that has passed through the toner insertion hole 23 is transferred to the recording paper P.

(3) Description of operation in toner recovery mode

In the toner collecting mode, the toner supply roller 1, the grid electrode 30, each first electrode 21, and each second electrode 22 are applied with a constant voltage satisfying the relationship represented by the following formula 1. In Formula 1, V2R is the second electrode 22
Applied voltage to the first electrode 21, V1R is applied voltage to the first electrode 21,
GR represents the voltage applied to the grid electrode 30, and VSR represents the voltage applied to the toner supply roller 1.

[0046]

(1) V2R <V1R <VGR <VSR

In the toner recovery mode, the voltage applied to the toner supply roller 1, the grid electrode 30, each first electrode 21 and each second electrode 22 is set so as to satisfy the relationship of the above-mentioned mathematical expression 1 to obtain the following. An electric field is generated.

Between the second electrode 22 and the first electrode 21,
An electric field that moves the toner from each second electrode 22 to the first electrode 21 is generated. Between each of the first electrodes 21 and the grid electrode 30, the first to second grid electrodes 30 are provided.
An electric field that moves the toner is generated. Further, an electric field that moves toner from the grid electrode 30 to the toner supply roller 1 is generated between the grid electrode 30 and the toner supply roller 1. Therefore, the print head 2
Excess toner staying in the toner is collected in the toner supply unit 10.

The voltage applied to the toner supply roller 1, the grid electrode 30, the first electrodes 21 and the second electrodes 22 in the toner collecting mode can be set in the printing mode as long as the relation of the above expression 1 can be satisfied. It may be set to one of the binary voltages applied to them. This eliminates the need to provide a new power supply circuit for toner recovery.

Also in the toner collecting mode, it is preferable to drive the ultrasonic vibrator 50 in order to improve the toner collecting efficiency. In particular, it is preferable to drive and control the ultrasonic transducer 50 so that the average vibration energy applied to the print head 2 is larger than that in the print mode.

6 (b), (c) and (d) are shown in FIG. 6 (a).
Is a vibration caused by the ultrasonic transducer 50 in the print mode, a method of increasing the average vibration energy applied to the print head 2 as compared with the print mode is shown.

In FIG. 6B, the amplitude of vibration by the ultrasonic transducer 50 is made larger than that in the print mode. Figure 6
In (c), the duty ratio of vibration by the ultrasonic transducer 50 is made larger than that in the print mode. In FIG. 6D, vibration is constantly applied by the ultrasonic transducer 50.

The applied voltage VBR to the base roller 3
Is preferably smaller than the applied voltage V2R to the second electrode 22. The reason for this is as follows. During printing, the applied voltage VBR to the base roller 3 is higher than the applied voltage V2R to the second electrode 22. When the voltage VBR applied to the base roller 3 is made higher than the voltage V2R applied to the second electrode 22 even during the toner recovery, the toner in the toner insertion hole 23 is caused by the potential difference between the second electrode 22 and the base roller 3. The inside of the insertion hole 23 may be moved toward the base roller 3 side. This may occur especially when the ultrasonic transducer 50 is being driven during toner recovery.

The applied voltage VBR to the base roller 3 is set to the second value.
By setting the voltage applied to the electrode 22 to a value smaller than V2R, it is possible to prevent the toner in the toner insertion hole 23 from moving to the base roller 3 side. (4) Description of operation in toner supply mode

In the toner replenishment mode, a constant voltage is applied to the toner supply roller 1, the grid electrode 30, each first electrode 21, and each second electrode 22 so as to satisfy the relationship shown in the following mathematical formula 2. In Formula 2, V2R is the second electrode 22
Applied voltage to the first electrode 21, V1R is applied voltage to the first electrode 21,
GR represents the voltage applied to the grid electrode 30, and VSR represents the voltage applied to the toner supply roller 1.

[0056]

[Formula 2] V2R <V1R> VGR> VSR

In the toner replenishing mode, the voltage applied to the toner supply roller 1, the grid electrode 30, each first electrode 21 and each second electrode 22 is set so as to satisfy the relationship of the above mathematical expression 2 to obtain the following. An electric field is generated.

An electric field for moving the toner from the toner supply roller 1 to the grid electrode 30 is generated between the toner supply roller 1 and the grid electrode 30. A grid electrode 3 is provided between the grid electrode 110 and each first electrode 21.
An electric field that moves the toner from 0 to each first electrode 21 is generated.

Therefore, the toner moves from the toner supply roller 1 to the grid electrode 30 side and passes through the slit 31 of the grid electrode 30. Then, the toner that has passed through the slits 31 of the grid electrode 30 is supplied to the first electrode 21, and the toner is deposited on the first electrode 21. As a result, the toner is replenished on the first electrode 21.

Between the second electrode 22 and the first electrode 21,
An electric field that moves the toner from each second electrode 22 to the first electrode 21 is generated. This prevents the toner from entering the toner insertion hole 23 in the toner replenishment mode.

The voltage applied to the toner supply roller 1, the grid electrode 30, the first electrodes 21 and the second electrodes 22 in the toner replenishing mode can be set in the printing mode as long as the relation of the above-mentioned expression 2 can be satisfied. It may be set to one of the binary voltages applied to them. This eliminates the need to provide a new power supply circuit for toner recovery.

When the charge polarity of the toner is positive, the magnitude relationship of the applied voltage to each portion in the toner collecting mode and the toner replenishing mode is opposite to that described above.

Table 1 shows specific examples of the voltages applied to the respective parts in the printing mode, the toner collecting mode and the toner replenishing mode.

[0064]

[Table 1]

In the above embodiment, the grid electrode 30 is used.
However, the present invention can also be applied to a powder jet image forming apparatus in which the grid electrode 30 is not provided. The present invention can also be applied to a powder jet image forming apparatus that is not provided with the ultrasonic transducer 50.

[0066]

As described above, according to the present invention, it is possible to collect the developer supplied onto the first electrode, which is not used for printing. Therefore, it is possible to constantly supply fresh developer to the print head. Further, it is possible to avoid a shortage of the developer at the start of the next printing due to the developer recovery.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a powder jet image forming apparatus.

FIG. 2 is a plan view showing a print head.

3 is a cross-sectional view taken along the line aa of FIG.

FIG. 4 is a cross-sectional view showing a relationship between a print head and a toner supply roller.

FIG. 5 is a time chart showing the voltage applied to each part in the print mode.

FIG. 6 is a time chart showing an example of drive control of the ultrasonic transducer in the toner recovery mode.

FIG. 7 is a configuration diagram showing a schematic configuration of a powder jet image forming apparatus developed by the applicant.

FIG. 8 is a plan view showing a print head.

9 is a sectional view taken along line bb of FIG.

FIG. 10 is a time chart showing changes in the voltage applied to each first electrode.

[Explanation of symbols]

 1 Toner Supply Roller 2 Print Head 3 Base Roller 20 Insulating Layer 21 First Electrode 22 Second Electrode 23 Toner Insertion Hole 30 Grid Electrode

Claims (5)

[Claims] 1. A print head, a developer supply roller and a base electrode provided so as to sandwich the print head, the print head being formed on an insulating layer and a surface of the insulating layer on the developer supply roller side. A plurality of first electrodes and a plurality of second electrodes formed on the surface of the insulating layer on the base electrode side are provided, and a matrix electrode portion is formed in the print head by the first electrodes and the second electrodes. A developer insertion hole is formed at each intersection of the first electrode and the second electrode in the print head, and the electric field between the developer supply roller and the first electrode causes the developer supply roller to move from the first electrode to the first electrode. In the powder jet image forming apparatus in which the developer is supplied to the first side and the developer supplied to the first electrode side passes through the developer insertion hole by the electric field between the first electrode and the second electrode, For printing In addition to the print mode, a developer collection mode for collecting the developer each time printing in the print mode is completed, and a developer for supplying developer to the print head before printing in the print mode is started A replenishment mode is provided. When the voltage applied to the first electrode is V1R, the voltage applied to the second electrode is V2R, and the voltage applied to the developer supply roller is VSR, the developer is negatively charged. In this case, a constant voltage satisfying the relationship of V2R <V1R <VSR is applied to the first electrode, the second electrode and the developer supply roller in the developer collecting mode, and V2R <in the developer replenishing mode.
A constant voltage satisfying the relationship of V1R> VSR is applied to the first electrode and the second electrode.
When the developer is positively charged and applied to the electrode and the developer supply roller, respectively, a constant voltage satisfying the relationship of V2R>V1R> VSR is applied to the first electrode and the second electrode in the developer collecting mode. And V2R> V1R in the developer replenishing mode.
A powder jet image forming apparatus, wherein a constant voltage satisfying the relationship of <VSR is applied to each of the first electrode, the second electrode and the developer supply roller. 2. A print head comprising: a print head; a developer supply roller and a base electrode provided so as to sandwich the print head; and a grid electrode provided between the print head and the developer supply roller. An insulating layer, and a plurality of first electrodes formed on the surface of the insulating layer on the developer supply roller side,
A plurality of second electrodes formed on the surface of the insulating layer on the base electrode side, and a matrix-shaped electrode portion is formed in the print head by the first electrode and the second electrode. A developer insertion hole is formed at each intersection with the second electrode, and the electric field between the developer supply roller and the first electrode supplies the developer from the developer supply roller side to the first electrode side. In the powder jet image forming apparatus in which the developer supplied to the first electrode side passes through the developer insertion hole due to the electric field between the first electrode and the second electrode, the operation mode is the print mode for printing. In addition, a developer collection mode for collecting the developer each time printing in the print mode is completed, and a developer replenishment mode for supplying developer to the print head before printing in the print mode is started. Set up If the applied voltage to the first electrode is V1R, the applied voltage to the second electrode is V2R, the applied voltage to the developer supply roller is VSR, and the applied voltage to the grid electrode is VGR, the developer is When the toner is negatively charged, a constant voltage satisfying the relationship of V2R <V1R <VGR <VSR is applied to the first electrode, the second electrode and the developer supply roller in the developer recovery mode, and the developer is supplied. V2R <V1R in replenishment mode
When a constant voltage satisfying the relation of>VGR> VSR is applied to the first electrode, the second electrode and the developer supply roller and the developer is positively charged, V2R> in the developer recovery mode. A constant voltage satisfying the relationship of V1R>VGR> VSR is applied to each of the first electrode, the second electrode and the developer supply roller, and V2R is applied in the developer replenishment mode.
The constant voltage that satisfies the relation of> V1R <VGR <VSR is the first
A powder jet image forming apparatus characterized by being applied to an electrode, a second electrode and a developer supply roller, respectively. 3. An ultrasonic vibrator is provided in the print head, the ultrasonic vibrator is driven at a constant cycle in the print mode, and the average value of the vibration energy by the ultrasonic vibrator is printed in the developer recovery mode. The powder jet image forming apparatus according to claim 1, wherein the ultrasonic transducer is driven so as to be larger than that in the mode. 4. When a voltage applied to the base electrode is VBR, a constant voltage satisfying the relationship of VBR <V2R is applied to the base electrode in the developer recovery mode when the developer is negatively charged. 4. When the developer is positively charged, a constant voltage satisfying the relationship of VBR> V2R is applied to the base electrode in the developer recovery mode. The powder jet image forming apparatus according to any one of 1. 5. When printing of one page is completed, first, the operation mode is set to the developer collecting mode for a predetermined period, and then the operation mode is set to the developer replenishing mode for a predetermined period. The powder jet image forming apparatus according to claim 1, 2, 3, or 4.