JP5742188B2 - Discharge energy recovery apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a discharge energy recovery apparatus and an image forming apparatus including the same.

  As shown in FIG. 8, in an image forming apparatus that ejects ink droplets and prints on a recording medium by applying a voltage to drive a piezoelectric element (hereinafter also referred to as “actuator”), an actuator driving voltage is used. A method of performing waveform current amplification using a bipolar transistor is generally known. FIG. 8 is a circuit diagram illustrating a configuration of a general piezoelectric element driving circuit device.

  In FIG. 8, the base terminals of the bipolar transistors Q83 and Q84 constituting the current amplifying unit 82 are set to “L” by the control signal from the recording head control unit 81, and the analog switch 86 is turned on. A voltage of + VDD is applied and an actuator charging current A flows, and a voltage Vcom that is a voltage charged to the actuator 85 flows into the GND as an actuator discharging current B.

  However, in the current amplifying circuit using the conventional bipolar transistor shown in FIG. 8, most of the electric power used for driving the actuator is a heat loss of the bipolar transistor, and wastes electric power. there were. A number of inventions have been filed in which the actuator discharge current B from the actuator is collected and reused as actuator drive power, but the effect on the actuator drive voltage waveform itself (for example, the waveform becomes dull and the actuator becomes dull. There is a problem that the drive control is not taken into consideration, and the voltage for collecting the actuator discharge current is too low, so that the amount of power that can be collected is small.

  In Patent Document 1, in order to reduce the power consumption by effectively using the electrical energy accumulated in the actuator, the charging current is charged in the charging capacitor after sequentially charging the discharging current of the actuator into a plurality of charging capacitors. Has been disclosed for reuse as actuator drive power.

  However, since charging and discharging of the actuator is performed by directly connecting the charging capacitor and the actuator, which is the problem described above, the rise time and fall time of the actuator drive voltage waveform cannot be controlled well. The problem that the drive voltage waveform of the actuator becomes dull and control is difficult has not been solved.

  Further, in Patent Document 2, in order to effectively use electric energy accumulated in the actuator and reduce power consumption, the discharge current of the actuator is charged into two charging capacitors and then charged into the charging capacitor. A configuration in which electric power is reused as actuator driving electric power is disclosed.

  However, since the charging potential of the charging capacitor is low, a large amount of power is changed to loss due to heat generation of the transistor, and the actuator discharge current cannot be efficiently recovered, resulting in less power that can be recovered. The problem has not been resolved.

  Therefore, the present invention has been made in view of the above problems, and with a configuration that hardly affects the actuator drive voltage waveform, a part of the power used for driving the actuator is efficiently recovered and used as effective power. It is an object of the present invention to provide a discharge energy recovery device that can be reused and an image forming apparatus including the same.

In order to solve the above problems, an energy recovery device according to the present invention as set forth in claim 1 is a discharge energy recovery device that recovers discharge energy discharged from the piezoelectric element when the piezoelectric element is driven. Drive voltage generating means for generating a voltage for driving the piezoelectric element, discharge voltage monitoring means for monitoring a voltage discharged from the piezoelectric element when the piezoelectric element is driven by the drive voltage generating means, and the discharge The first and second storage circuit elements that store charges corresponding to the voltage monitored by the voltage monitoring means, and the first charge amount corresponding to the capacitance that can be stored in the first storage circuit element. First applied voltage control means for applying the voltage up to the first charge amount, and when the amount of charge stored in the first storage circuit element reaches the first charge amount, Said second storage circuit element having a mass, have a, a second applied voltage control means for applying the voltage up to the second charge amount corresponding to the different capacitances, the first A circuit for reusing the charge accumulated in the storage circuit element in a first circuit different from the circuit for driving the piezoelectric element, and for driving the piezoelectric element using the charge accumulated in the second storage circuit element And reused in a second circuit different from the first circuit .

  Moreover, the energy recovery device according to the present invention is the discharge energy recovery device according to claim 1, wherein the first storage circuit element includes a plurality of capacitors each having a different capacitance, The charge is stored in an ascending order from a capacitor having the smallest capacitance.

  Furthermore, the energy recovery device according to the present invention is the discharge energy recovery device according to claim 1 or 2, wherein the second storage circuit element includes a plurality of capacitors each having a different capacitance, and the plurality of capacitors On the other hand, the charge is stored in an ascending order from the capacitor having the smallest capacitance.

  The energy recovery device according to the present invention is the discharge energy recovery device according to any one of claims 1 and 3, wherein the drive voltage generating means includes a current amplifier, and the voltage discharged from the piezoelectric element is: When switching from application to the first storage circuit element to application to the second storage circuit element, a voltage value applied to the current amplifier is controlled based on a voltage value for driving the piezoelectric element. It is characterized by.

  Furthermore, an image forming apparatus according to the present invention includes the discharge energy recovery device according to any one of claims 1 to 4.

  According to the present invention, it is possible to efficiently collect the discharge current of the actuator without affecting the actuator driving voltage waveform, and to reduce the power consumption by reusing it as effective power. .

1 is a structural diagram illustrating a basic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating functional blocks of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating recording head control of the image forming apparatus according to the embodiment of the present invention. It is a circuit diagram explaining the structure of the discharge energy recovery apparatus in embodiment of this invention. It is a figure which shows the voltage waveform in the discharge energy recovery apparatus in embodiment of this invention. It is a circuit diagram explaining the structure of the discharge energy recovery apparatus in other embodiment of this invention. It is a circuit diagram explaining the structure of the discharge energy recovery apparatus in further another embodiment of this invention. It is a circuit diagram explaining the structure of a general piezoelectric element drive circuit device.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. The present invention relates to a discharge energy recovery device that recovers discharge energy discharged from a piezoelectric element when the piezoelectric element is driven. When the actuator discharge current is recovered, the charging capacitor to be connected is changed according to the change of the discharge voltage. It is characterized by switching.

  FIG. 1 shows a basic configuration of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the carriage 11 is held by a guide lot 12 and scans in the main scanning direction (left and right direction in FIG. 1) via a pulley 14 that is passed between the carriage 11 and the main scanning motor 13. For example, a recording head 19 that discharges ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K) is mounted on the carriage 11, and is arranged on the recording head 19. Ink is ejected from the ink ejection nozzle 18.

  An image is formed on the recording medium by ejecting ink droplets at a necessary position while moving the carriage 11 in the main scanning direction. The position information of the carriage 11 is obtained by reading a pattern recorded at equal intervals on the encoder sheet 15 fixed to the housing while moving the encoder sensor 16 fixed to the carriage 11 and adding / subtracting the count. Can do.

  By performing the carriage movement in the main scanning direction and the ink ejection operation once, an image can be formed on a band having the same width as the length of the nozzle row. If the scanning motor 17 is driven to move the recording medium in the sub-scanning direction (vertical direction in FIG. 1) and repeat the image forming operation for one band, an image is formed at an arbitrary place on the recording medium. can do.

  Next, functional blocks of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram illustrating functional blocks of the image forming apparatus according to the embodiment of the present invention. Firmware for controlling the hardware of the image forming apparatus and drive waveform data of the recording head are stored in a ROM (Read Only Memory) 23. When a print job (image data) is received from a host PC (Personal Computer) 21, the CPU A (Central Processing Unit) 22 stores image data in a RAM (Random Access Memory) 24, and the main scanning control unit 25 moves the carriage 11 on which the recording head 19 is mounted to an arbitrary position on the recording medium.

  The recording head control unit 27 links the image data stored in the RAM 24, the recording head drive waveform stored in the ROM 23, and the control signal in conjunction with the positional information of the carriage 11 obtained from the main scanning encoder 29. Forward to. The recording head drive unit 28 drives the recording head 19 based on the data transferred from the recording head control unit 27 to eject ink droplets.

  Next, the recording head control unit 27 of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram illustrating recording head control of the image forming apparatus according to the embodiment of the present invention. An ink droplet is ejected by displacing the actuator 31 installed in the recording head 19.

  By applying the charging voltage Vcom to the actuator 31, the actuator 31 is displaced by turning the analog switch 32 ON / OFF. Based on information from the image data control unit 33, the analog switch 32 is controlled to be turned on / off. The charging voltage Vcom for the actuator 31 is generated by performing current amplification based on information from the drive waveform controller 34 of the recording head controller 27.

  Next, the configuration of the discharge energy recovery apparatus in the embodiment of the present invention and the voltage waveform in the discharge energy recovery apparatus in the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a circuit diagram for explaining the configuration of the discharge energy recovery apparatus in the embodiment of the present invention, and FIG. 5 is a diagram showing voltage waveforms in the discharge energy recovery apparatus in the embodiment of the present invention.

  When the actuator 31 discharges, the recording head controller 27 controls the switching elements Q1, Q2, Q3, and Q4 of the actuator discharge current recovery unit 46.

  First, when the charging voltage Vcom for the actuator 31 is discharged at a high voltage, that is, in the initial discharging state, the switching element Q1 is turned on (VG_Q1 in FIG. 5), and the charging capacitor C1 is charged (VC1 in FIG. 5).

  When the charging voltage Vcom for the actuator 31 is balanced with the voltage due to the charge stored in the charging capacitor C1, the charging capacitor C1 can no longer be charged, so the switching element Q1 is turned OFF (VG_Q1 in FIG. 5), and switching is performed. By turning on the element Q2 (VG_Q2 in FIG. 5), the uncharged charging capacitor C2 is charged (VC2 in FIG. 5). Then, the switching elements Q3 and Q4 are turned ON / OFF as appropriate, and are recovered by the voltage of the high voltage circuit (drive system) 47 and the voltage of the low voltage circuit (logic system) 48, respectively.

  The charging voltage Vcom for the actuator 31 is measured by the Vcom voltage monitoring unit 49, and the switching timing of the switching elements Q1, Q2 is controlled. That is, since the discharge current B from the actuator 31 is charged to a plurality of capacitors according to the change with time of the Vcom voltage with respect to the actuator 31, a high voltage circuit (drive system) 47 and a low voltage circuit (logic system) ) The recovery current can be obtained with a plurality of types of voltage values such as 48, and by recovering these, it can be reused in circuits of different voltage systems, and the recovered power can be efficiently obtained.

Next, another embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably.
FIG. 6 is a circuit diagram illustrating a configuration of a discharge energy recovery device according to another embodiment of the present invention.

  In this embodiment, a charging capacitor for storing power in the high voltage circuit (drive system) side 47 that generates the recovered power and a low voltage circuit (logic system) side 48 is replaced by a high voltage circuit 47 and a low voltage circuit 48. The charging capacitors C1 and C2 (where the capacitance is C1 <C2) and C3 and C4 (where the capacitance is C3 <C4) are different from each other. In the recovery unit 61, the recording head control unit 27 can select a capacitor to be charged.

  In the case of this embodiment, when the number of actuators to be driven is small, or when the total discharge amount from the actuators is small, the high voltage circuit 47 is a capacitor C1 having a small capacitance, and the low voltage circuit 48 is By connecting C3, which is a capacitor with a small electrostatic capacity, by turning on switching elements Q1, Q2, and Q5, Q6, respectively, and maintaining the balance between the total discharge amount from the actuator and the charging voltage of the capacitor quickly. The power consumed by the switching elements Q1, Q2, and Q5, Q6 is reduced.

  When the total discharge amount from the actuator exceeds the charging capacity of the capacitor C1 or C3, the switching element Q3 is connected in the high voltage circuit 47 or the low voltage circuit 48 so as to be connected to the capacitor C2 or C4 having a larger capacitance. Alternatively, Q7 is turned on, but when the charging capacitor to be connected is switched, the time constant of the circuit, that is, the constant representing the time taken for charging and discharging changes.

  By controlling the voltage applied to the base terminals of the transistors Q43 and Q44 of the current amplifying unit 42 from the potential of the charging voltage Vcom for the actuator 31 and the capacitance value of the newly connected charging capacitor, The amount of current to be passed through the emitter terminal of the transistor Q44 is calculated and controlled.

  Assuming that the time constant of the charging capacitor is τ, α is a proportional constant, and the current flowing through the emitter terminal of the transistor Q44 is I (t), the change Vf (t) of the voltage during discharge (t) is Vf (t). t) = αI (t) exp (−t / τ). As a result, the accuracy of the drive waveform of the actuator can be improved as a result.

  Next, still another embodiment of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. FIG. 7 is a circuit diagram illustrating a configuration of a discharge energy recovery apparatus in still another embodiment of the present invention. 6 differs from the other embodiments of FIG. 6 in that a variable inductor L1 and a variable resistor R1 are provided at the emitter terminal of the transistor Q44 (FIG. 6) as means for adjusting the charging current when the charging capacitor is switched from C1 to C2. Since the circuit configuration of the other parts is the same as that of the other embodiments in FIG. 6, the detailed description is omitted.

  When switching a plurality of connected charging capacitors in the actuator discharge current recovery unit 61 (FIG. 6), the time constant of the circuit, that is, the constant representing the time required for charging and discharging changes. The variable inductor L1 and the variable resistor R1 connected in series to the charging capacitor are controlled from the potential of the charging voltage Vcom (FIG. 6) and the capacitance value of the newly connected charging capacitor.

  Assuming that the time constant is τ, α is a proportionality constant, and the current is I (t), the change Vf (t) of the voltage during discharge per time (t) is Vf (t) = αI (t) exp (−t / Τ). In the case of the RL circuit, τ = L / R, and in the case of the RC circuit, τ = CR. Using this, the variable amount to be set is calculated and controlled by the recording head control unit 27. As a result, the accuracy of the drive waveform of the actuator can be improved as a result.

  As described above, according to the present invention, the actuator discharge current can be efficiently generated without affecting the actuator drive voltage waveform by switching the charging capacitor connected according to the change of the discharge voltage. Can be recovered.

  Even when the number of actuators to be driven is increased, the transistors are connected to a plurality of charging capacitors having different electrostatic capacities according to the amount of discharge energy from the actuators. It is possible to suppress and efficiently recover the actuator discharge current.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

DESCRIPTION OF SYMBOLS 11 Carriage 12 Guide lot 13 Main scanning motor 14 Pulley 15 Encoder sheet 16 Encoder sensor 17 Sub scanning motor 18 Ink discharge nozzle 19 Recording head 22 CPU
23 ROM
24 RAM
25 main scanning control unit 26 sub scanning control unit 27 recording head control unit 28 recording head driving unit 29 main scanning encoder 31 actuator 32 analog switch 33 image data control unit 34 drive waveform control unit 42 current amplification unit 46 actuator discharge current recovery unit 47 High voltage circuit (drive system)
48 Low voltage circuit (logic system)
49 Vcom voltage monitor

Japanese Patent No. 4152757 JP 2002-103603 A

Claims (5)

A discharge energy recovery device for recovering discharge energy discharged from the piezoelectric element when the piezoelectric element is driven,
Drive voltage generating means for generating a voltage for driving the piezoelectric element;
A discharge voltage monitoring means for monitoring a voltage discharged from the piezoelectric element when the piezoelectric element is driven by the drive voltage generating means;
First and second storage circuit elements for storing charges corresponding to the voltage monitored by the discharge voltage monitoring means;
First applied voltage control means for applying the voltage until reaching a first charge amount corresponding to a capacitance that can be stored in the first storage circuit element;
When the amount of charge stored in the first storage circuit element reaches the first charge amount, the second storage circuit element having a different capacitance from the capacitance has the different capacitance. a second applied voltage control means for applying the voltage up to the second charge amount corresponding, was perforated in,
Reusing the charge accumulated in the first storage circuit element in a first circuit different from the circuit driving the piezoelectric element;
A discharge energy recovery apparatus , wherein charges accumulated in the second storage circuit element are reused in a second circuit different from the circuit for driving the piezoelectric element and the first circuit .   The first storage circuit element is composed of a plurality of capacitors having different capacitances, and the order in which the charges are stored in the plurality of capacitors is ascending from the capacitor having the smallest capacitance. The discharge energy recovery apparatus according to claim 1.   The second storage circuit element includes a plurality of capacitors having different capacitances, and the order in which the charges are stored in the plurality of capacitors is ascending from the capacitor having the smallest capacitance. The discharge energy recovery device according to claim 1, wherein the discharge energy recovery device is a discharge energy recovery device.   The drive voltage generating means includes a current amplifier, and drives the piezoelectric element when a voltage discharged from the piezoelectric element is switched from being applied to the first storage circuit element to being applied to the second storage circuit element. The discharge energy recovery apparatus according to any one of claims 1 to 3, wherein a voltage value applied to the current amplifier is controlled based on a voltage value to be controlled.   An image forming apparatus comprising the discharge energy recovery device according to claim 1.

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