Driving apparatus for piezoelectric actuator

[Detailed Description of the Invention]

[Industrial Application] The present invention relates to the Drive a device of the electrostrictive actuator which adjusts the voltage impressed to the electrostrictive actuator which consists of piezoelectric elements.

[Description of the Prior Art] Since the electrostrictive actuator which obtains predetermined displacement conventionally using piezoelectric elements, such as PZT, is provided with high precision and a high-speed response, it is adopted widely. In order to drive the above-mentioned electrostrictive actuator, it is necessary to impress the voltage according to target displacement to an electrostrictive actuator, and the drive shown in Drawing 5 as a drive for it is used. The impressed electromotive force to a piezoelectric element is used about ±500V, it uses drive frequency by 100H2 DC-number, and this has an equipment configuration shown below. displacement sensor HC5 [ namely, ] from which the drive of this piezoelectric element detects the displacement value of electrostrictive actuator ACT -- control circuit CON which computes the target voltage value impressed to electrostrictive actuator ACT based on the output and target displacement value of this displacement sensor HC, Supply of a constant voltage power supply is received from constant voltage power supply circuit C■ which outputs constant voltage, and constant voltage power supply circuit CV, and it comprises a power amplifier AMP section etc. which supply target voltage to a voltage actuator based on the above-mentioned target voltage value. The impressed electromotive force of an electrostrictive actuator is controlled by using the drive of such an electrostrictive actuator by the optimal value which obtains target displacement.

[Problem(s) to be Solved by the Invention] However, the drive of the conventional electrostrictive actuator is not enough for I came., either, and the following subjects are left behind. First, the capability to generate the high pressure which exceeds the maximum voltage of a drive which impresses constant voltage power supply circuit CV to electrostrictive actuator ACT is required constitutionally. For this reason, the source of the high voltage is adopted as constant voltage power supply circuit CV, a device is enlarged, reducing an electric power loss and the amount of Depart carries out in difficulty, it is, and it is .. In supplying the voltage of right and negative (±) to electrostrictive actuator ACT, since it is necessary to generate positive and negative voltage even in constant voltage power supply circuit CV, it has caused enlargement of the device of - layer. Although the target voltage applied to a voltage actuator is controlled by power amplification part AMP, the electric power loss by this power amplification part AMP is large as compared with the power consumption of an electrostrictive actuator, and electric power efficiency is low, and heat dissipation capacity is increasing. While the present invention was made in order to solve the above-mentioned subject, it makes small and lightweight the generating part of the high voltage which makes an electrostrictive actuator generate desired displacement and raises flexibility, The efficiency is raised and it aims at providing the drive of the electrostrictive actuator which can moreover drive an electrostrictive actuator at high speed and with high precision.

[Means for solving problem] Means which the present invention constituted in order to solve the above-mentioned subject, adjusting the voltage impressed to the electrostrictive actuator which consists of a piezoelectric element of predetermined capacity -- the displacement value of the piezo-electric Actuator -- target displacement 1 -- in the drive of the electrostrictive actuator controlled soon the above-mentioned target displacement 1 -- a voltage determination means to determine the impressed electromotive force which is based soon and impressed to the above-mentioned electrostrictive actuator, When the charge voltage which the charged voltage detecting means which detects the charge voltage of the above-mentioned electrostrictive actuator, and the charged voltage detecting means detected is lower than the impressed electromotive force which the above-mentioned voltage determination means determined, The voltage applying means which transforms power supply voltage to impressed electromotive force, and it impresses to an electrostrictive actuator, and when the above-mentioned charge voltage is higher than the above-mentioned impressed electromotive force, The drive of the electrostrictive actuator provided with the discharging means which connects the above-mentioned electrostrictive actuator to the discharge circuit of the damping time constant according to the above-mentioned predetermined capacity is made into the gist.

[operation j the electrostrictive actuator which drives with the drive of the electrostrictive actuator of the present invention - it is a boat fishing electrostrictive actuator and is electrically equivalent to capacity. Therefore, an electrostrictive actuator has the characteristic of storing the supplied electric charge. Then, the charged voltage detecting means in the drive of the present invention has the operation which detects the charge voltage of an electrostrictive actuator, and detects the electric initial value of an electrostrictive actuator when controlling. The voltage determination means of the drive of the present invention determines the impressed electromotive force impressed to an electrostrictive actuator from the target displacement value which an electrostrictive actuator is made to generate. By the above-mentioned charged voltage detecting means and a voltage determination means, if information required for control of an electrostrictive actuator is acquired, the voltage applying means or discharging means which plays the following operations will operate alternatively. The voltage applying means operates, when the charge voltage which the charged voltage detecting means detected is lower than the impressed electromotive force which the voltage determination means determined (i.e., when it is necessary to control the voltage impressed to an electrostrictive actuator more highly than the present charge voltage). And the voltage which transformed power supply voltage even to impressed electromotive force is impressed to an electrostrictive actuator. The discharging means operates, when charge voltage is higher than the above-mentioned impressed electromotive force (i.e., when the voltage which should be impressed to an electrostrictive actuator needs to control lower than charge voltage), and it is connected to the discharge circuit of the damping time constant according to the predetermined capacity in which the electrostrictive actuator has an electrostrictive actuator. The discharge circuit of the damping time constant according to the predetermined capacity of the electrostrictive actuator acts with the predetermined capacity of an electrostrictive actuator, and suits here, and it discharges the charging charge accumulated in the electrostrictive actuator in the desired characteristic. Therefore, it will decrease, the terminal voltage of an electrostrictive actuator, i.e., displacement of an electrostrictive actuator, showing the time change based on the damping time constant of the discharge circuit. Hereinafter, in order to explain the drive of the electrostrictive actuator of the present invention more concretely, an example is given and explained in full detail.

[Example] Drawing 1 is a schematic diagram of the system which used the capacitive electrostrictive actuator for the diesel engine over the period (fuel injection duration) ordered the pressurized fuel at the actuator of the fuel injection valve which carries out injection supply. Fuel injection valve 3 (3a, 3b, 3c, 3d) which performs fuel injection is provided in the combustion chamber at each cylinder of diesel engine 1 so that it may illustrate. The air intake to this diesel engine 1 is performed via air intake manifold 7 from supercharger 5. Fuel injection valve 3 is the publicly known composition of having used the electrostrictive actuator, links the needle valve which opens and closes the injection hole by which fuel is injected, and electrostrictive actuator 9 (9a, 9b, 9c, 9d-) to build in, and drives a needle valve by elasticity of the electrostrictive actuator 9. Such a fuel injection valve 3 is connected with fuel pressure accumulation pipe 13 common to each cylinder via fueling pipe 11. Fuel pressure accumulation pipe 13 is capacity to that inside. - It has pressure accumulation room 15 of a law, and the fuel in this pressure accumulation room 15 is supplied to fuel injection valve 3 via fueling pipe 11. On the other hand, pressure accumulation room 15 was connected with the discharge mouth of fueling pump 19 in which discharge pressure control is possible via fueling pipe 17, and has received supply of the fuel pressurized by even the specified pressure from fueling pump 19. To this fueling pump 19, the fuel in fuel reservoir tank 23 is fed from fuel pump 21. Fuel injection valve 3 is connected with fuel reservoir tank 23 via fuel return lead pipe 25, respectively, and forms a circulating route of fuel. Fuel which was not supplied to diesel engine 1 in A jet April is returned to reservoir tank 23. Fuel pump 21 is formed in order to send in the fuel in fuel reservoir tank 23 in fueling pump 19, and even if there is no fuel pump 21, in particular when it is possible to inhale fuel in fueling pump 19, it is not necessary to form fuel pump 21. In order to detect operational status to diesel engine 1, The fuel pressure sensor 35 grade which detects the fuel pressure in number-of-rotations sensor 27 which detects the number of rotations of a crankshaft, cylinder distinction sensor 29 which outputs a signal in the degree of predetermined crank angle, cooling coolant temperature sensor 31 which detects engine cooling water temperature, charge pressure sensor 33 which detects charge pressure, and pressure accumulation room 15 provides, Being done. In order to detect the demand load to diesel engine 1, it has accelerator sensor 39 which detects the amount of treading in of accelerator 37. Battery 41 is a source of +12V voltage for the usual mount. Electric power is supplied to electrostrictive actuator drive 45 which drives an electrostrictive actuator of internal organs to engine controller 43 and each fuel injection valve 3 so that it may illustrate. Here, based on the output of each sensor mentioned above, the fuel oil consumption and fuel Inspiring time of diesel engine 1 are computed in engine controller 43, Signal SVx which shows target displacement value VX to electrostrictive actuator drive 45 is outputted, and a control signal is outputted to pump drive 47 which drives fueling pump 19. Therefore, high-speed and highly precise information processing capability is required of engine controller 43, and it is constituted by the logic circuit consisting mainly of CPU, ROM, and RAM in order to satisfy this. Next, the composition of electrostrictive actuator drive 45 is explained based on Drawing 2. Since each electrostrictive actuator 9a thru/or 9d which fuel injection valve 3 builds in is driven independently, respectively, drive 45 of an electrostrictive actuator has four drive blocks 45a thru/or 45d. These four drive pro An 45a thru/or 45d are the composition same to mutual, and the value and its human power timing of target displacement value signal SVx by which human power is carried out from engine controller 43 only differ from each other. Therefore, only the block diagram of drive block 45a which drives electrostrictive actuator 9a is shown in Drawing 2, and explanation of other drive blocks is omitted in order to avoid duplication. Drive block 45a shown in Drawing 2 will be Is if it divides roughly, Displacement of electrostrictive actuator 9a Control circuit 60 which outputs command value IVil and drive signal Vd based on displacement feedback signal Vf and target displacement value signal 5Vxa from engine controller 43 which are the detection signals of displacement sensor 50 to detect and the displacement sensor 50, its command value 1Vil, and drive signal Vd It is constituted by three parts of power circuit 70 which wins popularity and outputs drive voltage vp to electrostrictive actuator 9a. This example explains displacement X which appears in electrostrictive actuator 9a, and drive voltage vp impressed as a thing in proportionality relation. First, control circuit 60 is explained. Instructions of drive voltage vp which human power of displacement Feed Punk signal Vf from displacement sensor 50 and the target displacement 1 direct signal 5Vxa from engine controller 43 is carried out to arithmetic control circuit 62, and is impressed to electrostrictive actuator 9a here (1iVi is computed.) That is, the present displacement value and target displacement value of electrostrictive actuator 9a are compared, and a signal required in order to Addition-value-control the displacement value of actual electrostrictive actuator 9a to a target displacement value is computed as command value Vi. Therefore, arithmetic control circuit 62 is constituted so that the operation based on the drive characteristic of electrostrictive actuator 9a which is a controlled object may be performed. Human power of the command value Vi outputted from arithmetic control circuit 62 is carried out to absolute-value circuit 64, and command value IV11 which is changed into an absolute value here and is actually given to power circuit 70 is created. Although command value ■[this [ whose ] is an operation result of target displacement value 5Vxa and displacement Feed Punk signal Vf changes as "positive" "negative" Here, power circuit 70 of this example is for controlling drive voltage Vp impressed to electrostrictive actuator 9a only as "positive" voltage. Human power of the command value Vi of arithmetic control circuit 62 is carried out also to a polar change and charge-and-discharge controller 66. The monitor which is a detection result on monitor circuit the 6th which detects drive voltage vp actually impressed to electrostrictive actuator 9a besides command value Vi in a polar change and charge-and-discharge circuit 66 (Ii V m is inputted and drive signal Vd as shown in Table 1 is outputted based on these two data.) It is although the signal wire single as drive signal Vd has been expressed in writing in Drawing 2 since it is easy, As shown in Table 1 in fact, it had six signal wires to A~F, and the output voltage of each signal wire A thru/or F is switched to High (it is called the following and "H") or Low (henceforth "L") based on command value Vi and monitor value Vm. Table 1 Next, like Above, human power of command value 1■11 and six drive signals Vd which carry out and are outputted from control circuit 60 is carried out, and power circuit 70 which transforms the voltage of battery 41 suitably and it impresses to electrostrictive actuator 9a as drive voltage Vp is explained. Variable voltage boost portion 80 with which power circuit 70 transforms the power supply voltage of battery 41 according to instructions fllVil by which human power is carried out from Le control circuit 60, Two portions with the polar change and charge and discharge part 90 which changes output voltage VO outputted from the variable voltage boost portion 80 to positive and reverse polarity, and is impressed by electrostrictive actuator 9a, or makes the charging charge of electrostrictive actuator 9a discharge are comprised. It explains per introduction and variable voltage boost portion 80. Bunty Li's 41 power source line is connected to the primary Rising pressure transformer 82 side via chopper circuit 81 which is a part of variable voltage boost portion 80. Therefore, a primary Rising pressure transformer 82 side is intermittently magnetized by switching operation of chopper circuit 81, and the voltage based on the switching frequency of chopper circuit 81 and the winding ratio of Rising pressure transformer 82 is induced by the secondary of Rising pressure l and lance 82. In this way, the voltage of the exchange induced by the secondary of Rising pressure transformer 82 is changed and outputted to the direct-current voltage (output voltage Vo) stable through rectification and a smoothing circuit. It is PWM controller 84 which plays the operation which controls the switching timing of the above-mentioned chopper circuit 81, and changes the value of output voltage ■0 according to command value IVi. That is, PWM controller 84 carries out human power of the output of current detecting circuit 87 which detects the output current of error amplifier 86 which amplifies the difference of voltage detector circuit 85 which detects output voltage VO of variable voltage boost portion 80, and command value IVi, and variable voltage boost portion 80, Output voltage Vo was fed back and correspondence with command value IVil is secured. Human power of the output of variable voltage boost portion 80 is carried out to the polar change and charge and discharge part 90 which operates based on six drive signals which above-mentioned polar change and charge-and-discharge controller 66 output. The detailed composition of this polar change and charge-and-discharge gB90 is expressed to Drawing 3. Transistor Tra which uses a polar change and charge and discharge part 90 as a switching element so that it may illustrate, Bridge connection of Trb, Trc, and the Trd was carried out, and also resistor R and transistor Tre are connected to transistor Trb and parallel, and resistor R and transistor T "f are connected to transistor Trc and parallel. And the output terminal is connected to the both ends of electrostrictive actuator 9a which is a controlled object. Electric capacity C1 each transistor T to which electrostrictive actuator 9a has resistance r of resistor R "it is a value which judges synthetically of switching performance, the drive frequency of electrostrictive actuator 9a, etc., and is determined suitably. Six drive signals Vd outputted from charge-and-discharge controller 66 during a polar change as the base signal of these six transistors Tr, i.e., a 0N10FF signal, are used, In transistor Tr of "H", the output of drive signal Vd will be in an ON state, and transistor Tr of rLJ will be in an OFF state. The connection method takes correspondence with subscripts raJ thru/or rfJ of each transistor Tr, and output systems rAJ thru/or rFJ of drive signal Vd, and is held so that it may illustrate. Since drive signal Vd of Continuing is outputted 6 system by the specification shown in the above-mentioned table 1, the polar change and charge and discharge part 90 which operates in response control drive voltage Vp of electrostrictive actuator 9a as follows. First, it is command value ■l>=0, and when the voltage of the "positive" direction should be impressed to electrostrictive actuator 9a, it explains per. That further needs to raise the voltage impressed to electrostrictive actuator 9a now with command value V1 >= monitor value V m at this time. Therefore, output voltage VO which the "H" signal is outputted only to transistor TraTrc and outputted to electrostrictive actuator 9a with variable voltage boost portion 80 is impressed by polarity as it is. In this way, it is although the impressed electromotive force of electrostrictive actuator 9a is raised and generating displacement is brought close to target displacement, This generating displacement is detected by displacement sensor 50, and since it is fed back to control circuit 60, drive voltage Vp impressed so that generating displacement of electrostrictive actuator 9a may turn into target displacement correctly is further tuned finely. On the contrary, when it is instruction fiVi< monitor value Vm, it is necessary to drop the terminal voltage of electrostrictive actuator 9a. In this case, the "H" signal is outputted only to transistor TrcTre. The discharge circuit which makes a course transistor Trc, resistor R, and transistor Tre is formed in electrostrictive actuator 9a by this, and electric discharge of the charging charge according to the damping time constant determined with electric capacity C which electrostrictive actuator 9a has, and resistance r of resistor R in a discharge circuit is started. Descent of the electrostrictive actuator 9a Asthma voltage by electric discharge of charging charge, Since it is always detected with monitor value Vm and reduction of generating displacement of electrostrictive actuator 9a by descent of terminal voltage is also detected with displacement sensor 50, A discharge circuit is formed only during the period which becomes command value Vi= mini monitor m, and Addition value feedback control of the generation rate * of electrostrictive actuator 9a is carried out to target displacement after all. Change of the terminal voltage of electrostrictive actuator 9a by the operation of such a polar change and a charge and discharge part 90 is illustrated to Drawing 4. It changes command value Vi and drive voltage Vp impressed to electrostrictive actuator 9a being completely in agreement, if transistor TraTrc will be in an ON state, as shown in a figure. When the terminal voltage of electrostrictive actuator 9a becomes large from command value Vi, Transistor Tra will be replaced and transistor Tre will be in an ON state, - To which always does command value Vi and drive voltage Vp one as a result by transistor Tra being in an ON state again if sincerity a few and drive voltage Vp fall [ drive voltage Vp ] from command value Vi in the characteristic according to the damping time constant of the discharge circuit -- feedback control is carried out like. transistor T which has the above circuit operations of a polar change and charge and discharge part 90 in the object position of a bridged circuit in the period whose command value Vi is "negative" -- "-- it being alike and accepting it -- rF (since J signal is given (refer to Eclectic 1), the voltage of the above and reverse polarity is impressed or the discharge circuit to an opposite direction is formed.) Therefore, Addition value feedback control of the generating displacement of piezo-electric bitter taste child Operator 9a will always be carried out to target displacement like the above. the drive of the electrostrictive actuator of this example which is constituted as mentioned above and of which J operation is done -- getting twisted -- the following effects are clear. The drive of the electrostrictive actuator of an example is the composition of obtaining the high voltage which the drive of Boost and electrostrictive actuator 9a takes the power supply voltage of rose dust 41 by the chopper control based on the absolute value of command value Vi at the optimal value. Therefore, a large-sized high-voltage power supply with weight cannot be made equally required, but a device can be constituted in the amount * of width, and small size. Since it has a polar change and charge and discharge part 90, it is a thing of the simple composition which generates "positive" voltage as a source of voltage, and control of electrostrictive actuator 9a is attained enough. Thereby, much more miniaturization of a power supply section and a weight saving are attained. Although the drive of the electrostrictive actuator of an example applies digital art skillfully and obtains the high voltage like the above, on the other hand, it cannot draw charging charge of electrostrictive actuator 9a in the power supply part. However, a polar change and charge and discharge part 90 of an example can form easily the discharge circuit which draws the charging charge of electrostrictive actuator 9a by instructions of drive signal Vd, and equivalent trouble does not have it in electric discharge of charging charge. And resistor R of resistance f[r suitably selected according to electric capacity C etc. which electrostrictive actuator 9a has is inserted in the discharge circuit. " -- for this reason, it is avoided that drive voltage Vp of electrostrictive actuator 9a falls too much by fault electric discharge as compared with command value v1 (refer to the 4th figure), and the control capability of electrostrictive actuator 9a improves more, and effective use of the source of electric power is achieved. The above-mentioned example is although it was explained that generating displacement of electrostrictive actuator 9a was proportional to drive voltage Vp, Even if the charge between these shows hysteresis characteristics etc., it can go up to changing the logic of control circuit 60, and can respond easily, and the system which is rich in the control accuracy of the above-mentioned example and the flexibility which has a response can constitute easily similarly. In the above-mentioned example, the discharge circuit which a polar change and charge and discharge part 90 constitute is constituted using resistor R and transistor Tre or Trf, and electric discharge of charging charge is always performed via resistor R at the time of electric discharge of electrostrictive actuator 9a. However, as mentioned above, resistor R is suitably determined according to the drive frequency of electrostrictive actuator 9a and electric capacity C, the switching performance of transistor Tr, etc. Therefore, various kinds of resistance r1, r2.r3 when building the system which changes the drive frequency of electrostrictive actuator 9a ... Embodiment To is good by various modes which do not deviate from the gist of the present invention, such as making a plurality of discharge circuits selectable using a resistor.

[Effect of the Invention] As mentioned above, as the example was given and explained in full detail, the drive of the electrostrictive actuator of the present invention generates the drive voltage applied to an electrostrictive actuator, only when required, and carries out Addition value feedback control of the generating displacement of an electrostrictive actuator to target displacement. Therefore, Person power consumption and generation of heat are prevented, and the outstanding effect that the power-saving nature and small voltinism of a system improve together is produced. The discharging means which performs electric discharge of an electrostrictive actuator is equipped with the discharge circuit of the damping time constant according to the capacity which a piezoelectric element has. For this reason, also when reducing the terminal voltage of an electrostrictive actuator, discharging charging charge more than needed is avoided, Effective use of a power supply is achieved, and also it excels also in controllability and a response and analog control of displacement of the impressed electromotive force to an electrostrictive actuator and an electrostrictive actuator serves as a drive of an easy electrostrictive actuator.

[Brief Description of the Drawings]

Drawing 1 is a composition explanatory view of the fuel injection system using the drive of the electrostrictive actuator which is an example of the present invention, Drawing 2 shows the block diagram of the electrostrictive actuator drive, and, in Drawing 3, the electric diagram of its polar change and charge-and-discharge gf5 and Drawing 4 show the said polarity change and the charge and discharge part, and the composition explanatory view of the drive of the electrostrictive actuator of the former [ Drawing / 5 ]. It is [ 53 / ... Variable voltage boost portion 90 / ... A polar change and charge and discharge part representative / Patent attorney Standing Drawing 4 of A study (two others) / ... Displacement sensor 60 ... Control circuit 80 ] -9a... Electrostrictive actuator 41 ... Battery 45a ... Drive block diagram vp -----Vi