JP2001063028A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which a head temperature sensor can be corrected more appropriately while reducing the cost. SOLUTION: A temperature sensor 103 outputting a signal corresponding to the inner temperature of a head 10 is built in the head. A monitor circuit 22 for sampling and amplifying the output from temperature sensor 103, and a power supply section 21 generating a single power supply voltage being used commonly by the head and the monitor circuit 22 are provided on an interconnection board 20 carried on a carriage. A voltage dividing circuit 38 connected with the monitor circuit 22 through a cable 8, an A/D conversion circuit 37 for converting an analog output from the voltage dividing circuit 38 into a digital signal, and a control means for monitoring the temperature based on the digital output from the A/D conversion circuit 37 and the output from the temperature sensor 103 are provided on a controller board 30 disposed fixedly in the imaging apparatus.

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 having a print head for discharging ink as a recording agent, such as an ink jet printer.

[0002]

2. Description of the Related Art An ink jet printer is an image forming apparatus employing an ink jet system in which ink droplets are ejected from nozzles using a head having a plurality of nozzles arranged in order to perform printing. There are features. The print head is installed and fixed at a predetermined position on a carriage that reciprocates in the paper width direction, and forms a desired image on the recording paper by discharging ink droplets while scanning the carriage on the recording paper.

[0003] The nozzle is always filled with ink, and a heater element is provided therein. When a heating pulse is applied to the heater element and heated, bubbles are generated and expanded in the nozzle, and the ink in the nozzle is discharged. A part of the ink is pushed out of the nozzle to form an ink droplet, which lands on the recording paper to form a dot.

In order to fill the nozzles with ink, it is necessary to install an ink tank in close contact with the head. This form includes an integrated type in which the head and the ink tank are integrally formed, and a separate type in which the head and the ink tank are separately installed. In a printer using a separate type and a head with a sufficiently long life, the user does not need to replace the head, and only needs to replace the ink tank when the ink runs out. When a head that requires replacement by the user is used, the head is replaced by the user.

As described above, in an ink jet printer, ink droplets can be ejected by heating a heater element. However, in order to maintain stable print quality, it is necessary to keep the power applied to the heater constant. There is. For this reason, a high precision is required for the power supply voltage supplied to the head.

Conventionally, since the head is mounted on a movable carriage, the head is mounted on a relay board provided on the carriage.
A head power supply circuit and a circuit for monitoring the output of the head temperature sensor are provided. The analog output of the head temperature sensor output monitor circuit is converted into a digital signal, and is transferred via a cable to a control circuit (including a CPU) on a controller board fixed in the apparatus.

The head temperature sensor detects the temperature in the head and determines the parameters of the ejection pulse for ejecting ink based on the detection result so that the printing quality is optimized. Therefore, the detection of the head temperature affects the print quality, and therefore, high accuracy is also required.

As a technique for improving the detection accuracy of the head temperature, there is a method of correcting variations in temperature characteristics of a sensor, as disclosed in Japanese Patent No. 2693193. This correction is performed at the time of power-on of the apparatus, at the time of head replacement, or at predetermined time intervals even after power-on. In the latter, a more accurate correction can be performed because a temperature change in which the head adapts to the atmosphere for a predetermined time can be observed.

[0009]

By the way, on the relay board, a power supply voltage different from 24 V for the head power supply circuit and 5 V for the head temperature sensor output monitor circuit has been used.

Providing power supply circuits of different voltages on the relay board as described above has caused an increase in cost. Also,
Since the digitized temperature sensor output signal is transferred to the controller board via the cable, the number of signal lines increases.

Further, conventionally, there have been roughly two types of ink jet printers for correcting a head temperature sensor and controlling power on / off.

First, the head temperature sensor is corrected only once when the power is turned on, and the power is not turned on to the head except during printing. If you do not turn on the head except during printing, the power consumption during standby can be suppressed, or some abnormality occurs in the main unit circuit, the heater in the head will remain on, This is because there is an effect that an unexpected accident such as excessive heating and destruction of the head can be prevented.

A second method is to leave the power of the head constantly on, correct the head temperature sensor at predetermined time intervals, and simultaneously monitor the head temperature to detect an abnormality of the head.

With the above two types of ink jet printers,
The first method has a problem that the head temperature sensor is corrected only once when the power is turned on, so that the detection accuracy of the head temperature is inferior to that performed a plurality of times. In the second method, there is a problem that the power consumption in the standby mode is increased because the power of the head is always turned on.

With the above background, an object of the present invention is to provide an image forming apparatus having a novel circuit configuration related to processing of an output signal of a head temperature sensor.

It is another object of the present invention to provide an image forming apparatus capable of reducing the cost of the apparatus, suppressing the increase in power consumption, and more appropriately correcting the head temperature sensor.

[0017]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention is an image forming apparatus having a detachable ink jet type print head mounted on a carriage, provided inside the head and adapted to the internal temperature of the head. A temperature sensor for outputting a signal, a temperature sensor output monitor circuit provided on a relay board on a carriage, for sampling and amplifying the output of the temperature sensor, and a head and a temperature sensor output provided on the relay board. A head power supply unit for generating a single power supply voltage shared by a monitor circuit, and a voltage divider provided on a controller board fixedly arranged inside the device and connected to the temperature sensor output monitor circuit via a cable. A circuit, provided on the controller board, for converting an analog output of the voltage dividing circuit into a digital signal A digital-to-digital conversion circuit, and control means provided on the controller board for monitoring a temperature based on an output of the temperature sensor based on a digital output of the analog-to-digital conversion circuit; and an output of the temperature sensor output monitor circuit. A signal is sent to the voltage dividing circuit via the cable, and is converted into a digital signal on the controller board side.

As described above, by sharing the power supply of the head and the power supply of the head temperature sensor output monitor circuit,
The cost of the device can be reduced. Accordingly, the output of the temperature sensor output monitor circuit is sent from the relay board to the controller board via a cable in the form of an analog signal of a relatively high voltage (24 V system in the embodiment), and is distributed on the controller board. Press and digitize. By sending the sensor output as an analog signal in this manner, the number of signal lines is reduced, and the signal is transmitted at a relatively high voltage. Therefore, there is an advantage that the influence of noise is reduced as compared with a low voltage signal.

Preferably, an environmental temperature sensor for detecting a temperature in the apparatus is provided, and the control means detects the temperature of the temperature sensor in the head based on both outputs of the environmental temperature sensor and the temperature sensor in the head. Means for correcting the output, the control means, during a period when the printing operation of the head is not performed, to periodically supply power to the head and the temperature sensor output monitor circuit by the head power supply unit, Performs temperature sensor correction and monitors head temperature. This makes it possible to appropriately control the head temperature, to maintain a high print quality, and to provide a safe inkjet printer.

Further, it is preferable not to supply power to the head and the temperature sensor output monitor circuit when detecting that the dust cover is open.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the image forming apparatus of the present invention. In FIG. 1, the recording paper 14
Is based on the drive of the transport motor 15,
Is transported on the platen 12 in the paper transport direction X. The print head 10 as a printing unit for forming an image includes:
The recording paper 14 is held by the carriage 11 and is scanned in a direction Y substantially perpendicular to the transport direction of the recording paper 14 so as to face the recording paper 14. A linear scale 16 is provided in parallel with the scanning path of the carriage 11, and forms a linear scale encoder in cooperation with a linear scale sensor 19 on the carriage 11. The flexible flat cable 8 pulled out from the inside of the plate 9 is connected to an electric circuit on the carriage 11. This electric circuit is formed on a relay board (FIG. 2 described later), which provides an interface between the head 10 and a controller board (described later in FIG. 2).

FIG. 2 is a control block diagram of the image forming apparatus of FIG. This control block is roughly composed of a head 10, a relay board 20, and a controller board 30 from a physical point of view.

The controller board 30 is fixed inside the apparatus, and can be an image scanner, a personal computer, a CAD (Computer).
Aided Design). Based on the image data VD sent from the external device 40, the print head 10 forms an image on recording paper.

The control is performed by a control unit which is an electric circuit on the controller board 30. This control unit receives the image data VD sent from the CPU 33 as the central processing unit and the external device 40, generates various signals, and outputs the signals to the control circuit 101 inside the print head 10 together with the image data VD. Head drive signal generator 35,
Head temperature sensor 10 for detecting the temperature of print head 10
3, a voltage dividing circuit 38 for dividing an output from a temperature sensor output monitoring circuit 22 (described later) for detecting the output signal Sen, an A / D converter 37 for monitoring the output of the voltage dividing circuit 38, and a print head drive signal. An image memory 36 that stores the image data VD from the generation unit 35, a work RAM 31 that is connected to the CPU 33, and temporarily stores data and the like,
Similarly, it is composed of a ROM 32 which is connected to the CPU 33 and stores a program for operating the apparatus and the like, and an I / O port 34 which interfaces with each load section 42.

The load of each load unit 42 includes a motor for driving a carriage and a conveyance of a recording sheet (FIGS. 1 and 15), various sensors, and the like. The detection signal LS of the linear scale 16 by the sensor 19 is output to the print head drive signal generation unit 35, and the output COVER of the dust cover (upper cover) detection sensor (not shown) is output to the CPU 33. Is Rukoto. Also, CP
U33 controls the operation of the entire apparatus such as each memory and the power supply for the head.

The print head 10 includes a control circuit 101, a heater 102, and a head temperature sensor 103. The printhead drive signal generator 35
When a predetermined signal is input from the, the heater 102 determined by the signal is driven. Although not shown, the heater 1
A plurality of heaters 102 are mounted on the corresponding nozzles in the recording paper conveying direction. When a pulse signal is given to the heater 102 to heat the heater 102 and cause the ink to boil, ink droplets are ejected from the nozzle by the bubble pressure generated thereby.

The relay board 20 includes a temperature sensor output monitor circuit 2 for monitoring the output of the temperature sensor 103 in the head 10.
2 and the heater 102 of the head 10 under the control of the CPU 33.
And a head power supply circuit 21 for controlling the temperature sensor output monitor circuit 22. In the present embodiment, the operating power of the head 10 and the temperature sensor output monitor circuit 22 is supplied from a common power supply (here, DC 24 V). Thereby, cost can be reduced.

Next, the operation of the apparatus in this embodiment
The operation will be described. When the serial image data VD is sent from the external device 40, the print head drive signal generation unit 35 temporarily stores the image data VD for several bands in the image memory 36 in accordance with a command from the CPU 33. The held image data VD is subjected to various types of image processing, and is read out in accordance with scanning of the print head 10 and is read out.
Output the image data VD. In the present embodiment, as described above, the clock signal CLK is generated using the slit detection signal LS output in synchronization with the scan of the print head from the linear encoder, and various controls such as output of image data VD are synchronized. Is taking. Further, in the present embodiment, the print head is constituted by 128 nozzles,
It is divided into eight blocks. Accordingly, the print head drive signal generator 35 generates the enable signals Ben1 to Ben8 of each block and also generates the heater drive pulse signal Hen which is a signal necessary for ink ejection.

The image data VD output from the print head drive signal generator 35 and the block enable signal Ben
1 to 8, the heater driving pulse signal Hen, and the like are transmitted to the print head 10, and the internal control circuit 101 turns on the heater 102 only for the nozzles for which the enable signals Ben and Hen are enabled, thereby ejecting ink. An image image is formed on the recording paper.

The head temperature sensor 103 is disposed inside the print head as described above, and the output Sen is monitored by the head temperature sensor output monitor circuit 22. In the print head drive signal generator 35,
A disenable period of the pulse signal Hen for driving the heater is detected, and the output Sen of the head temperature sensor 103 is sampled only during the disable period to obtain a CP.
SMP for holding the temperature data only when there is a request to read the temperature data of the print head 10 from U33
CLK signal is output. This is head temperature sensor 1
The output Sen of the head temperature sensor is sampled at a timing when no noise is generated so that noise is not induced in the output Sen of 03 by the pulse signal Hen for driving the heater. The head temperature sensor output monitor circuit 22, the voltage dividing circuit 38, and the A / D converter 37 will be described later in detail.

FIG. 3 is a diagram showing the internal structure of the print head drive signal generator 35. 3, the print head drive signal generator 35 mainly includes an image memory controller 211, an image synchronization signal generator 212, and a head block selection signal generator 2.
13, a heater drive signal generator 214, and a CPU interface I / F 215.

The image memory control unit 211 stores the serial image data VD sent from the external device 40 as described above.
Signal for temporarily storing (inputting) the image data VD for several bands in the image memory 36, and outputting the stored image data VD in synchronization with the clock signal CLK in synchronization with the scan of the print head 10. Is generated. The generation of the address signal of the image memory 36 is performed by the external device 4.
The image signal VD is generated at the transmission timing of the image data VD from 0, and the generation of the address signal when it is output therefrom is generated in accordance with the synchronization timing from the image synchronization signal generation unit 212 described later.

The image synchronizing signal generation section 212 synchronizes with the generation of the address signal for outputting the image data VD from the image memory 36 based on the slit detection signal LS from the linear sensor of each load section 42 as described above. Signal Hs
In addition, a latch signal LAT for holding the image data VD by the print head 10 is generated.

The head block selection signal generation section 213
A block enable signal Be for selecting which block of the print head to drive in synchronization with the synchronization signal Hsync
Generation of n1 to n8 is performed.

The heater drive signal generator 214 generates a heater drive pulse signal Hen and generates a
The pulse signal Hen for driving the heater is stored in the register of F215.
Set the width of The width of the pulse signal Hen can be variably controlled depending on which pulse width is set or which is combined with which. This setting is a sequence in which the output value of the head temperature sensor 103 of the print head 10 is monitored by the CPU 33 using the head temperature sensor output monitor circuit 22, and the setting is performed based on the result.

FIG. 4 is a diagram showing an example of the internal circuit configuration of the head temperature sensor output monitor circuit 22 on the relay board 20 together with the relationship with the controller board 30. The head temperature sensor output monitor circuit 22 is mounted on the relay board 20, and includes a constant current circuit 221, a sample and hold circuit 222,
It comprises an amplifier circuit 223.

The output of the amplifier circuit 223 is connected to a cable (FIG. 1).
8) the voltage dividing circuit 38 on the controller board 30
Supplied to The voltage dividing circuit 38 includes a resistor R connected in series.
8 and a resistor R9. The potential at the connection point of the two resistors, that is, the divided voltage output of the voltage dividing circuit 38 is converted into a digital value by the A / D converter 37 and input to the CPU 33. CPU
33 instructs the head drive signal generation unit 35 on the same controller board 30 to send the relay board 2 via the cable 8
The sample clock SMPCLK is output to the analog switch of the sample hold circuit 222 in the temperature sensor output monitor circuit 22 above 0. SMPCLK is a sampling timing signal when sampling the output Sen of the head temperature sensor 103, and performs sampling of the head temperature sensor 103 during a period in which the heater drive pulse signal Hen is disabled.

Here, a head temperature sensor 103 in which two diodes are connected in series is used. A constant current flows from these constant diodes from a constant current circuit 221 to detect a forward voltage drop of the diodes. Circuit configuration. Since the diode forward voltage drop varies with the diode temperature, the diode forward voltage drop is amplified as the head temperature sensor output,
By sampling the temperature, the temperature of the diode, that is, the temperature in the head can be detected. Here, the head temperature sensor 103 is controlled by the constant current circuit 221.
Considering the current Id flowing through

Id = VH ｛{(R2 / (R1 + R2)}｝ (1 / R3) (1) In the amplifier circuit, the relationship between the input voltage Vi and the output voltage Vo is as follows.

Vo = {(R4 + R5) / (R6 + R7)} · (R7 / R4) · VH

− (R5 / R4) · Vi (2) In the present embodiment, the power supply voltage VH is 24 volts, which is common to the power supply for driving the head, that is, the power supply for the heater of the head 103. In this way, the cost can be reduced by using both power supplies in common, and the output of the amplifying circuit 223 can be converted to a high voltage analog signal of 24 volts using the cable 8.
The signal is transmitted to the controller board 30 via the controller board 30 and is converted into a digital value by dividing the voltage on the controller board 30 side. Therefore, the number of signal lines required in the cable 8 can be reduced as compared with the digital signal, and the voltage can be reduced. The effects of noise can be reduced as compared with analog signals.

FIG. 6 is a graph showing the temperature of the head temperature sensor 103.
This shows the characteristics of the output voltage (sen). The output voltage of the head temperature sensor 103 decreases with the temperature.

Sen = αT + β (3) This characteristic varies depending on the head temperature sensor 103, that is, the head in which the head temperature sensor 103 is incorporated. In particular, there is a large variation in the offset amount, which is the portion β in the equation (3). To compensate for this variation,
A high-precision environmental temperature sensor (not shown) for detecting the environmental temperature is provided outside, and when the head temperature is considered to be the same as the environmental temperature, the head temperature detected by the head temperature sensor 103 and the environmental temperature sensor A correlation with the environmental temperature detected by the computer is determined. This is called head temperature sensor correction.

More specifically, if the ambient temperature is To and the head temperature obtained from the output of the head temperature sensor 103 is T where the To temperature should originally be To, the head temperature sensor correction is performed by adding the offset β. On the other hand, the correction based on the temperature difference (To-T) is performed. Normally, this variation is peculiar to the head, so that the head temperature sensor correction may be performed only when the head is replaced.

However, this correction method is effective only when the head temperature and the environmental temperature are the same, and for example, when a head in a different room with a different temperature is brought and mounted on the apparatus. Due to the difference between the head temperature and the ambient temperature, it may not be possible to make a correct correction.

Therefore, in the present embodiment, the head temperature sensor correction is performed when the power is turned on and when the head is replaced. However, the head temperature sensor correction is performed at regular intervals after the head is replaced. The head temperature sensor correction is performed at the time when the temperature is sufficiently adjusted to the ambient temperature (for example, 60 minutes), and finally, the head temperature sensor correction at this time is effective. Also,
The temperature of the head is monitored regularly to prevent accidents.

As described above, it is necessary to monitor the output of the head temperature detection sensor 103 other than during printing.
At this time, as shown in FIG. 4, VH, that is, the power supply for driving the heater of the head 10 is turned on.

Referring to FIG. 5, a processing flow relating to ON / OFF of the head power supply in this embodiment will be described.

When the power of the apparatus is turned on, first, the head power is turned on to perform temperature sensor correction, and then the head power is turned off (S11 to S13). Thereafter, if there is a print command (S14, yes), the head power is turned on (S1).
5) A printing operation is performed (S16). When the printing operation is completed, the head power supply is turned off (S17). When a predetermined time has passed without printing instruction (S18, Yes), the head power supply is temporarily turned on (S19), the head temperature sensor is corrected, and the head temperature is monitored (S20). The correction value obtained by the head temperature sensor correction is held in the non-volatile memory (or battery backup memory) even during the OFF period of the apparatus power. When an abnormal temperature of the head or the like is detected by monitoring the head temperature, predetermined error processing is performed. After that, turn on the head power supply.
FF is performed (S21).

Although not shown, power is supplied to the head 10 and the temperature sensor output monitor circuit 22 for safety while detecting that the dust cover is open based on the output COVER of the dust cover detection sensor. Not performed.

While the preferred embodiment of the present invention has been described above, various modifications and changes are possible.

[0053]

According to the image forming apparatus of the present invention, the head temperature sensor can be corrected more appropriately while reducing the apparatus cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a control block diagram of the image forming apparatus of FIG.

FIG. 3 is a configuration diagram of the inside of a print head drive signal generation unit 35 shown in FIG. 2;

4 is a diagram showing an example of a circuit configuration inside a head temperature sensor output monitor circuit 22 on a relay board 20 together with a relationship with a controller board 30. FIG.

FIG. 5 shows ON / OF of a head power supply in the present embodiment.
It is a flowchart which shows the processing flow regarding F.

FIG. 6 shows a head temperature sensor 103 according to the embodiment.
4 is a graph showing the temperature-output voltage (sen) characteristics of FIG.

[Explanation of symbols]

 8 Cable 10 Head 11 Carriage 20 Relay Board 22 Temperature Sensor Output Monitor Circuit 30 Controller Board 33 CPU 35 Head Drive Signal Generation Unit 37 A / D Converter 38 Voltage Divider Circuit 103 Head Temperature Sensor 221 Constant Current Circuit 222 Sample Hold Circuit 223 Amplifier Circuit

Claims (3)

[Claims] An image forming apparatus having a detachable ink jet type print head mounted on a carriage, a temperature sensor provided inside the head and outputting a signal corresponding to the internal temperature of the head, and a relay on the carriage A temperature sensor output monitor circuit provided on a board, for sampling and amplifying the output of the temperature sensor; and a single power supply voltage provided on the relay board and shared by the head and the temperature sensor output monitor circuit. A head power supply unit for generating, a voltage dividing circuit provided on a controller board fixedly disposed inside the apparatus, and connected via a cable to the temperature sensor output monitoring circuit; and a voltage dividing circuit provided on the controller board, An analog-to-digital conversion circuit for converting an analog output of the voltage dividing circuit into a digital signal; Control means for monitoring the temperature based on the output of the temperature sensor based on the digital output of the analog-to-digital conversion circuit, and outputting the output signal of the temperature sensor output monitor circuit via the cable. An image forming apparatus, wherein the image signal is sent to the voltage dividing circuit and converted into a digital signal on the controller substrate side. 2. An apparatus according to claim 1, further comprising: an environmental temperature sensor for detecting a temperature in the apparatus, wherein the control unit detects a temperature of the temperature sensor in the head based on both outputs of the environmental temperature sensor and a temperature sensor in the head. The control unit performs power supply to the head and the temperature sensor output monitor circuit periodically by the head power supply unit during a period in which the printing operation of the head is not performed, and controls the temperature. 2. The image forming apparatus according to claim 1, wherein the sensor temperature is corrected and the head temperature is monitored. 3. The image forming apparatus according to claim 1, wherein power is not supplied to the head and the temperature sensor output monitoring circuit when the opening of the dust cover is detected. .