JP3991526B2 - Piezo injector and method for adjusting injection quantity of piezo injector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezo injector and a method for adjusting an injection amount of the piezo injector.
[0002]
[Prior art]
The piezo injector uses a piezo stack that uses a piezoelectric effect to switch between valve opening and closing, and is used in a common rail fuel injection device of a diesel engine. The piezo injector is configured so that the nozzle hole at the tip of the nozzle is opened and closed by raising and lowering the nozzle needle inserted in the nozzle, and the nozzle needle is raised and lowered by increasing and decreasing the back pressure. The back pressure control unit for switching to a low pressure includes a piezo stack as a back pressure switching means. The piezo stack is switched between an expanded state and a contracted state depending on whether it is charged or discharged via an inductor circuit, and the back pressure of the nozzle needle is switched between high pressure and low pressure.
[0003]
There are two types of back pressure control systems: a piston that defines the back pressure chamber is displaced by the expansion and contraction of the piezo stack, and the pressure in the back pressure chamber is switched between high and low. There is a system in which the pressure in the back pressure chamber is switched between high and low by opening and closing the valve rod of the two-way valve by expansion and contraction of a piezo stack as a structure communicating with the low-pressure source through a two-way valve. In addition, the back pressure chamber is configured to communicate with the high pressure source and the low pressure source via a three-way valve, and the back pressure chamber is communicated with either the high pressure source or the low pressure source by extending or contracting the piezo stack of the valve rod of the three-way valve. There is a switching method (Japanese Patent Laid-Open No. 9-184463). Regardless of the configuration of the back pressure control unit, the interval between the expansion timing and the contraction timing of the piezo stack is defined by the control signal of the piezo stack, and the injection time, that is, the injection amount of the piezo injector is controlled.
[0004]
The injection characteristics such as the responsiveness of the injection start of the piezo injector vary depending on the detailed specifications such as the shape of each part of the injector even if the basic configuration of the piezo injector is the same. For example, a piezo injector using a three-way valve in a back pressure control unit described in JP-A-9-184463 has a high-pressure fluid inflow path from a high-pressure source to a three-way valve, and a high-pressure fluid from a three-way valve to a low-pressure source. Adjust the operating characteristics of the back pressure control unit and set the injection characteristics of the piezo injector by changing the flow rate of the flow path from the outflow path and the three-way valve to the back pressure chamber of the nozzle needle. ing. Even when the throttle is not actively provided, the shape of these flow paths regulates the flow rate and significantly affects the injection characteristics.
[0005]
[Problems to be solved by the invention]
By the way, even in the case of injectors having the same specifications, there are individual differences due to manufacturing variations. Such individual differences appear as non-uniform injection characteristics among individuals. In order to make the injection characteristics uniform among the individual, it is sufficient that the piezo injector can be reworked at the end of the manufacturing process of the piezo injector based on the error of the actual injection amount with respect to the target injection amount of each piezo injector. For example, it suffices if the flow path restricting the operating characteristics of the back pressure control unit can be adjusted.
[0006]
However, once the assembly proceeds until actual injection is possible, it is virtually impossible to correct the shape of each part of the piezo injector.
[0007]
The present invention has been made in view of the above circumstances, and firstly, an object thereof is to provide a piezo injector capable of adjusting the injection amount with a simple configuration. A second object of the present invention is to provide a method for adjusting the injection amount of a piezo injector that can accurately and easily reduce variations in injection amount between individuals.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, the adjustment inductor is connected in series with the piezo stack on the charge path or the discharge path of the piezo stack which switches the nozzle needle between opening and closing depending on whether charging or discharging is performed via the inductor circuit. Is connected so that the inductance of the inductor circuit during charging or discharging of the piezo stack can be corrected individually for each piezo injector.
[0009]
Since the inductance of the inductor circuit is increased and corrected by the adjusting inductor, the charging current or discharging current of the piezo stack is reduced accordingly, and the operation of the piezo stack is delayed. Accordingly, the opening or closing of the nozzle needle is delayed in accordance with the inductance of the adjustment inductor, and the injection amount from the injection hole can be increased or decreased. Even if the manufacturing process of the piezo injector has advanced to the stage where actual injection is possible, the injection amount can be adjusted without changing the shape of each part such as the flow path.
[0010]
According to a second aspect of the present invention, as a terminal for connecting between the piezo stack and the inductor circuit, a first terminal that conducts with one pole of the piezo stack and a second terminal that conducts with the other pole of the piezo stack. And a third terminal that conducts through one of the poles of the piezo stack and the adjusting inductor.
[0011]
When a current flows through the third terminal, the inductance of the inductor circuit can be corrected to increase according to the inductance of the adjustment inductor of the piezo stack. Thus, the injection amount of the piezo injector is corrected according to the inductance of the adjustment inductor.
[0012]
According to a third aspect of the present invention, the adjustment inductor is connected in series with the piezo stack on a path through which a current flows when the valve is opened, on the charge path or the discharge path.
[0013]
Since the operating speed of the piezo stack at the time of closing the valve when the nozzle needle is opened and closed is not changed among the individual piezo injectors, it can be sharp cut regardless of the individual. It is suitable for fuel injection of an internal combustion engine.
[0014]
According to a fourth aspect of the present invention, when the injection amount is insufficient, the inductance of the adjusting inductor is set so that the inductance of the inductor circuit at the time of valve opening becomes small or the inductance of the inductor circuit at the time of valve closing becomes large. Increase or decrease to increase the injection amount. When the injection amount is excessive, decrease the injection amount by increasing or decreasing the inductance of the adjustment inductor so that the inductance of the inductor circuit at the time of valve opening increases or the inductance of the inductor circuit at the time of valve closing decreases. To do.
[0015]
Even if the injection amount varies among the individual piezo injectors due to manufacturing variations of the piezo injector, etc., the error of the actual injection amount with respect to the target injection amount is offset, and the variation in the injection amount can be reduced. Adjustment is easy because the adjustment inductor is simply reworked.
[0016]
In the invention according to claim 5, the inductance of the adjusting inductor is increased or decreased by changing the number of turns of the coil member.
[0017]
In order to increase the inductance, the number of turns of the coil is increased, and in order to decrease the inductance, the number of turns of the coil is decreased. Therefore, the adjustment of the injection amount is further facilitated.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which a piezo injector of the present invention is applied to a common rail fuel injection device for a diesel engine will be described with reference to FIGS. 1, 2, and 3. In FIG. 2 showing the overall configuration of the common rail fuel injection device, the common rail fuel injection device 1 is provided with a common common rail 12 that communicates with a piezo injector (hereinafter simply referred to as an injector) 11 of each cylinder of a diesel engine. The inside is accumulated by high-pressure fuel pumped from the high-pressure supply pump 13. In the illustrated example, only one injector 11 is shown, but the same basic configuration is provided for the number of cylinders. In the injector 11, the drive circuit 7 constituting the ECU 18 charges and discharges a piezo stack (to be described later) of the injector 11 via a cable, and the pressure inside the combustion chamber of each cylinder is substantially increased from the injector 11 to the combustion chamber of each cylinder at a necessary time. The fuel is injected at the same injection pressure. The pressure in the common rail is detected by the pressure sensor 19, and the ECU 18 controls the intake metering valve 14 based on the detection result to adjust the amount of fuel pumped to the common rail 12. Is controlled so as to obtain an optimum injection pressure that gives good combustion according to the operating conditions known by the above. The injector 11 has a drain line 17.
[0019]
In FIG. 3 which shows the whole cross section of the injector 11, the injector 11 passes through the combustion chamber wall (not shown) of the engine and is attached so that the lower end portion in the drawing protrudes into the combustion chamber. The injector 11 includes a rod-shaped holder 2, and a nozzle portion 11a for high-pressure fuel injection and a back pressure control portion 11b for injection control are formed in the holder 2. Specifically, the holder 2 is configured by closely fitting a plurality of circular members in the vertical direction, and a vertical hole 20 is formed at the axial center position in the inside thereof, and the high-pressure passage 23 and the drain passage 25 are substantially parallel thereto. Is formed.
[0020]
A nozzle hole 21 through which high-pressure fuel as a high-pressure fluid is injected opens at the lower end of the holder 2 and communicates with the lower end portion of the vertical hole 20 via a sack 22. A high pressure port 26 is provided at the upper end of the holder 2 and is connected to a high pressure fuel line 16 (FIG. 2) that leads to the common rail 12 (FIG. 2) that holds the high pressure fuel. High pressure fuel is introduced into the injector 11 for injection and control from the high pressure port 26. An outlet port 27 is also provided at the upper end of the holder 2, and is connected to a drain line 17 (FIG. 2) that leads to a fuel tank 15 (FIG. 2) that is a low pressure source.
[0021]
The nozzle part 11a is demonstrated. The vertical hole 20 of the holder 2 has a cone shape in which the diameter of the connecting end 201 with the sack 22 increases toward the upper side, and serves as a valve seat 201 on which a nozzle needle 31 described later is seated.
[0022]
A rod-like nozzle needle 31 penetrates through a portion of the lower hole about 1/3 of the vertical hole 20 so as to be movable up and down, and a needle cylinder 203 which is the upper half of the portion holds the nozzle needle 31 slidably. is doing. The nozzle needle 31 is formed with a cone-shaped valve surface 311 whose diameter decreases toward the lower side at the lower end portion, and is seated on the valve seat 201.
[0023]
An annular oil reservoir 202 is formed on the outer periphery of the nozzle needle 31 at the lower end of the needle cylinder 203. The oil reservoir 202 is in communication with the high-pressure passage 23, and high-pressure fuel is supplied through the high-pressure port 26 located at the upstream end of the high-pressure passage 23. The high-pressure fuel supplied to the oil reservoir 202 passes through the gap between the valve surface 311 of the nozzle needle 31 and the valve seat 201 when the nozzle needle 31 is lifted, and is injected from the injection hole 21 via the sack 22. .
[0024]
In addition, high-pressure fuel always acts on an annular portion of the nozzle needle 31 that is not in close contact with the valve seat 201 of the cone-shaped lower end surface, and urges the nozzle needle 31 upward, that is, in the valve opening direction.
[0025]
A deep hole-like depression is formed on the upper end surface of the nozzle needle 31, and a spring 32 is interposed in a compressed state between the depression bottom surface and a valve rod 33 of a spill valve portion 111b described later. It is biased downward, that is, in the valve closing direction.
[0026]
Above the nozzle needle 31, a space is defined by the wall surface of the needle cylinder 203 and the upper end surface of the nozzle needle, which is a control hydraulic pressure chamber 204 that is a back pressure chamber. The control hydraulic chamber 204 is electrically connected to the high-pressure passage 23 via the in-orifice 24 so that high-pressure fuel is supplied from the high-pressure passage 23, and a back pressure that urges the nozzle needle 31 downward, that is, in the valve closing direction is applied. appear.
[0027]
The back pressure control unit 11b that controls the back pressure of the nozzle needle 31 will be described. The back pressure control unit 11b includes a spill valve unit 111b and a piezo actuator unit 112b. The spill valve portion 111b has a valve rod 33 penetrating the vertical hole 20 above the spring 32. The valve rod 33 is provided with an umbrella portion 331 at the lower end portion of the rod portion 332 and is slidably held by the rod portion 332 in the piston cylinder 208 which is a part of the vertical hole 20. The diameter of the vertical hole 20 is increased immediately below the piston cylinder 208, and an annular passage 207 is formed on the outer periphery of the rod portion 332. The annular passage 207 is in communication with the drain passage 25.
[0028]
An outlet hole 205 is formed between the control hydraulic chamber 204 and the annular passage 207 in the vertical hole 20. The outlet hole 205 is formed in a cone shape in which the opening peripheral portion on the control hydraulic chamber 204 side is enlarged in diameter on the lower side. The valve seat 206 receives the cone-shaped surface of the umbrella portion 331 whose diameter increases toward the lower side as the valve surface 3311. That is, the spill valve portion 111b in the figure is an open valve, and when the valve rod 33 is displaced downward, that is, toward the control hydraulic chamber 204, the valve surface 3311 is separated from the valve seat 206 to open the outlet hole 205, thereby opening the control hydraulic chamber 204. Is discharged to the drain passage 25 through the outlet hole 205 and the annular passage 207.
[0029]
The valve rod 33 is urged by the hydraulic pressure of the control hydraulic chamber 204 and the compressed spring 32 in the valve closing direction.
[0030]
The piezo actuator unit 112b will be described. The piezo actuator portion 112b is a portion that drives the valve rod 33 of the spill valve portion 11b. An upper portion of the vertical hole 20 above the piston cylinder 208 is an actuator chamber 209 having a larger diameter than the piston cylinder 208, and the piston 34 is inserted above the valve rod 33 through the piston cylinder 208 and the actuator chamber 209. . The piston 34 has a small-diameter shaft portion 341 extending from a lower end surface of a cylindrical holding portion 342 having a large diameter and an open upper end. The shaft portion 341 is slidable with the valve rod 33 on the piston cylinder 208. The lower end surface thereof is in contact with the upper end surface of the valve rod 33.
[0031]
The upper holding portion 342 of the piston 34 is stored in the actuator chamber 209 so as to be movable up and down. Between the holding portion 342 and the bottom surface of the actuator chamber 209, a disc spring 35 is interposed on the outer periphery of the shaft portion 341 of the piston 34 in a compressed state, and urges the piston 34 upward.
[0032]
The piezo stack 5 is fitted in the cylindrical holding portion 342 of the piston 34. The piezo stack 5 can extend and contract in the vertical direction, and pushes down the piston 34 when the piezo stack 5 extends.
[0033]
A connector portion 11 c that receives a cable for charging / discharging the piezo stack 5 is provided at the upper end portion of the injector 11.
[0034]
In FIG. 1A showing a cross section of the injector 11 in the vicinity of the piezo stack 5, a pair of lead wires 51 extending from the top surface of the piezo stack 5 are provided above the piezo stack 5 at the upper end of the vertical hole 20 of the holder 2. A circular member 36 holding 52 is fitted, and the upper small diameter portion thereof is screwed to the holder 2 via a cylindrical member 37, and the upper end position of the piezo stack 5 is fixed. Upper portions of the holder 2, the circular member 36, and the cylindrical member 37 are covered with a resin lid 38.
[0035]
A cylindrical projecting portion is formed on the top surface of the lid portion 38 and serves as a receiving port 381 for receiving the connector at the cable end. Three terminals 41, 42, and 43 are surrounded by the receiving port 381 and protrude from the lid portion 38 to constitute the connector portion 11 c together with the receiving port 381. Each of the terminals 41 to 43 comes into contact with the terminal of the cable end connector to be paired when the receiving port 381 and the cable end connector are fitted.
[0036]
The first terminal 41 is electrically connected to the first lead wire 51 drawn from the positive electrode of the piezo stack 5, and the second terminal 42 is electrically connected to the second lead wire 52 drawn from the negative electrode of the piezo stack 5. The third terminal 43 is electrically connected to the first lead wire 51 via the adjustment inductance coil 6 which is an adjustment inductor disposed above the circular member 36.
[0037]
The adjustment inductance coil 6 is formed by winding a coil member 62 around a ring-shaped core 61 for several turns. In the final manufacturing process of the injector 11, the number of turns of the adjustment inductance coil 6 is adjusted for each injector 11 in a state where actual injection is possible, and a predetermined inductance is given to the adjustment inductance coil 6. After the adjustment is completed, the adjustment inductance coil 6 is resin-molded and mechanically fixed. The lid member 38 is molded at this time. The number of turns of the adjustment inductance coil 6 will be described later.
[0038]
In FIG. 1B showing a drive system circuit of the piezo stack 5, a drive circuit 7 is a DC-DC converter that is common to the piezo stack 5 of each injector 11 and converts a battery voltage into a DC voltage of a predetermined magnitude. 70 and a capacitor 71 for holding electric energy by charging from the DC-DC converter 70. The DC-DC converter 70 and the capacitor 71 are connected when the main switch 76 is turned on, and the DC-DC converter 70 charges the capacitor 71.
[0039]
The capacitor 71 is connected to the piezo stack 5 via the inductor circuit 7a. The inductor circuit 7 a includes inductance coils 72 and 73 that are two inductors, and forms a charging path and a discharging path of the piezo stack 5. The charging path passes from the capacitor 71 through the first charging switch 77 and the charging inductance coil 72 connected in series to the positive electrode of the piezo stack 5 via the third terminal 43 of each injector 11. The discharge path passes from the positive electrode of the piezo stack 5 of each injector 11 through the first terminal 41 to the discharge inductance coil 73 and discharge switch 78 connected in series to the capacitor 71.
[0040]
A second charge switch 79 and a discharge diode 74 are connected to the second terminal 42 that is electrically connected to the negative electrode of the piezo stack 5 of each injector 11, and the negative electrode of the piezo stack 5 is grounded via these. The second charging switch 79 forms the ground side of the charging path, and the discharging diode 74 forms the ground side of the discharging path.
[0041]
By turning on the first charging switch 77 and the second charging switch 79 of the injector 11 corresponding to the injection cylinder in a pulsed manner, the capacitor 71 from the charged state passes through the charging inductance coil 72 and the adjusting inductance coil 6 to piezo. A charging current flows through the stack 5. When the piezo stack 5 is charged, the piezo stack 5 extends. The charging voltage of the piezo stack 5 is substantially proportional to the charge amount of the charge supply source due to the inductive action of the charging inductance coil 72 and the adjusting inductance coil 6.
[0042]
Further, when the piezo stack 5 is in a charged state, the discharge switch 78 is turned on in a pulsed manner, whereby a discharge current flows from the piezo stack 5 through the discharge inductance coil 73 in the direction opposite to the charging current. Discharges. The piezo stack 5 is discharged through a discharge diode 74 that is forward biased during discharge. The energy loss associated with charging / discharging of the piezo stack 5 is supplemented by turning on the main switch 76, and is prepared for fuel injection of the injector 11 corresponding to the next injection cylinder.
[0043]
As shown in the figure, a negative voltage prevention diode 75 is provided in parallel with the piezo stack 5 and the discharge diode 74 connected in series, so that the positive side of the piezo stack 5 becomes the anode in common to all the injectors 11. This negative voltage prevention diode 75 is for preventing the piezo stack 5 from being overdischarged and causing the voltage of the piezo stack 5 to become negative. The voltage of the piezo stack 5 is always restored to 0V by discharge. Yes.
[0044]
Each of the switches 76 to 79 can be controlled to be turned on and off by a calculation unit that constitutes the ECU 18, for example, a microcomputer.
[0045]
The operation of this injector will be described. When the charging switches 77 and 79 are turned on in a pulse shape, the piezo stack 5 extends to push down the piston 34, and the spill valve portion 111b is opened.
[0046]
When the outlet hole 205 is opened, the hydraulic pressure in the control hydraulic chamber 204 is reduced, thereby reducing the back pressure of the nozzle needle 31 and acting on the nozzle needle 31 in the valve opening direction (upward acting on the lower end surface of the nozzle needle 3). The oil pressure) becomes dominant, and the nozzle needle 31 rises. Thus, fuel injection is started from the nozzle hole 21.
[0047]
When the discharge switch 78 is turned on at a predetermined timing calculated from the operating state, the electric charge of the piezo stack 5 is released and the voltage drops to return to the state before charging (0 V). As a result, the piezo stack 5 is reduced to its original length, and the piston 34 and the valve rod 33 of the spill valve portion 111b are pushed up by the spring force of the disc spring 35, the hydraulic pressure of the control hydraulic chamber 204, and the spring force of the spring 32. , The outlet hole 205 is closed. As a result, the conduction between the control hydraulic chamber 204 and the drain passage 25 is interrupted, and the hydraulic pressure of the control hydraulic chamber 204 is restored by the high-pressure fuel flowing from the high-pressure passage 23, and the valve closing direction urging force to the nozzle needle 31 is prevailed again. The nozzle needle 31 descends to the seating position, closes the nozzle hole 21 and stops fuel injection. Thus, fuel injection can be performed in a predetermined period defined by the timing when the charging switches 77 and 79 are turned on and the timing when the discharging switch 78 is turned on.
[0048]
The inductance coil 6 for adjustment has a larger inductance as the number of turns increases, the charging current to the piezo stack 5 decreases, the extension speed of the piezo stack 5 decreases, the operating speed of the spill valve portion 111b decreases, and the above charging is performed. The valve opening response of the nozzle needle 31 to the operation of the switches 77 and 79 is delayed. Thereby, the injection time is shortened and the injection amount is reduced. Since the adjusting inductance coil 6 is provided for each injector 11, the injection amount can be corrected independently of the other injectors 11 by adjusting the number of turns of each injector 11.
[0049]
The number of turns of the adjusting inductance coil 6 can be adjusted by adjusting the actual injection amount before the resin molding after the injector main body portion such as the nozzle portion 11a and the spill valve portion 111b is formed in the manufacturing process. Based on this. Therefore, for example, the injection amount can be corrected without reworking the shape of the element (for example, the cross-sectional area of the in-orifice 24) that constitutes the spill valve portion 111b and defines its operating characteristics.
[0050]
Here, when the actual injection amount is less than the target injection amount, the number of turns of the adjusting inductance coil 6 is reduced to reduce the inductance so that the inductance of the inductor circuit 7a at the time of valve opening, that is, the inductance of the charging path is reduced. And increase the injection amount. If the actual injection amount is more than the target injection amount, the inductance is increased by increasing the number of turns of the adjustment inductance coil 6 so that the inductance of the inductor circuit 7a at the time of valve opening, that is, the inductance of the charging path is increased, Reduce the injection amount. Thereby, the individual difference of the injection amount of the injector 11 is offset, and the uniformity of the injection amount is improved.
[0051]
It should be noted that the initial number of turns before adjustment is preferably set in consideration of variations in the injection amount because it defines the amount of decrease in inductance.
[0052]
In this embodiment, the inductance coil for adjustment adjusts the inductance by the number of turns of the coil member wound around the core. However, the core is made of a material (permeability) and shape (cross-sectional area, diameter) different from each other. You may adjust by replacing with.
[0053]
In addition, the injector according to the present embodiment has a configuration in which an adjustment inductor is molded with resin in a holder, but has only a pair of terminals that are electrically connected to both poles of the piezo stack. An adjustment connector that relays the connector portion and the charging / discharging cable may be fitted into the connector portion of the injector main body portion), and the adjustment inductance coil may be stored in the adjustment connector. That is, the adjustment connector is provided with a positive electrode terminal and a negative electrode terminal on the injector main body side for connection with the terminal of the connector portion of the piezo injector main body portion, and a terminal of the cable end connector on the charge / discharge cable side. Three terminals for conducting are provided. In the adjustment connector, of the three terminals, the first terminal is connected to the positive terminal connected to the positive electrode of the piezo stack, and the second terminal is connected to the negative terminal connected to the negative electrode of the piezo injector. Then, the third terminal and the positive terminal are connected by an adjustment inductance coil. The adjustment of the inductance of the adjustment inductance coil may be performed by the number of turns as described above, or a plurality of types of adjustment connectors having different inductances of the adjustment inductance coil are prepared, and according to the required adjustment amount of the injection amount. This may be done by replacing the adjustment connector.
[0054]
Even in such a configuration, the valve opening response of the nozzle needle can be changed according to the inductance of the adjustment inductance coil.
[0055]
In this embodiment, the adjustment inductance coil is connected in series with the charging inductance coil to adjust the valve opening response of the nozzle needle. This is because the sharp cut is not impaired regardless of the adjustment amount of the adjustment inductance coil, which is desirable in the case of fuel injection as in this embodiment. Of course, the adjustment inductance coil is connected in series with the discharge inductance coil. And the valve closing response of the nozzle needle may be adjusted between the individual. That is, for an injector that requires an increase in the injection amount, increasing the inductance of the adjusting inductance coil slows down the discharge speed of the piezo stack and reduces the operating speed of the spill valve. Delay the valve closing timing. Even if it does in this way, injection time can become long and the injection amount can be increased. Conversely, for an injector with an excessive injection amount, the injection amount is reduced by reducing the inductance of the adjustment inductance coil.
[0056]
Further, the nozzle needle is configured such that the spill valve is opened by charging the piezo stack and the back pressure is lowered and lifted, but the nozzle needle may be lifted by discharging the piezo stack depending on special circumstances. In this case, as the inductance coil for adjustment is connected in series with the inductance coil for discharge and the inductance coil for adjustment is made larger, the valve opening timing can be delayed and the injection amount can be reduced.
[0057]
In the present embodiment, the inductor circuit of the drive circuit includes two inductors, ie, a charging inductance coil and a discharging inductance coil. However, a configuration including a common inductor for charging and discharging may be used. In this case, since the piezo injector has the above three terminals in the connector portion, the common inductor in the drive circuit is connected to the first terminal directly connected to the piezo stack positive electrode of the injector and the piezo through the adjustment inductor. A change-over switch connected to any one of the third terminals that communicate with the stack positive electrode may be provided.
[0058]
Moreover, although this embodiment showed what was applied to the common rail type fuel-injection apparatus, this invention is applicable also to the injector of another use.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view of a main part of a piezo injector according to the present invention, and FIG. 1B is a circuit diagram of a piezo stack drive system.
FIG. 2 is a configuration diagram of a common rail fuel injection device for a diesel engine to which the piezo-tack of the present invention is applied.
FIG. 3 is a partial cross-sectional side view of the piezo injector of the present invention.
[Explanation of symbols]
11 Piezo injector
11a Nozzle part
11b Back pressure control unit
11c Connector part
12 Common rail (high pressure source)
2 Holder (nozzle)
21 nozzle hole
31 Nozzle needle
41, 42, 43 terminals
5 Piezo stack
6 Adjustment inductance coil (Adjustment inductor)
61 core
62 Coil member
7 Drive circuit
7a Inductor circuit

Claims (5)

A nozzle to which a high-pressure fluid from a high-pressure source is supplied, a nozzle needle that is inserted into the nozzle and opens and closes a nozzle hole formed at the tip of the nozzle, and a piezo stack that is charged and discharged via an inductor circuit extends and contracts the nozzle needle. In a piezo injector that has a back pressure control unit that switches the back pressure between high pressure and low pressure and operates the on / off valve of the nozzle needle, an adjustment inductor is connected in series with the piezo stack on the charge path or discharge path of the piezo stack At least, the piezo injector is capable of individually correcting the inductance of the inductor circuit when charging or discharging the piezo stack. 2. The piezo injector according to claim 1, wherein a first terminal connected to one pole of the piezo stack and a second conductive connected to the other pole of the piezo stack are connected as terminals between the piezo injector and the inductor circuit. A piezo injector provided with a terminal, one pole of a piezo stack, and a third terminal electrically connected through the adjustment inductor. 3. The piezo injector according to claim 1, wherein the adjustment inductor is connected in series with a piezo stack on a path through which a current flows when the valve is opened, on the charge path or the discharge path. 4. . 4. The method for adjusting an injection amount of a piezo injector according to claim 1, wherein when the injection amount is insufficient, the inductance of the inductor circuit at the time of valve opening is reduced or the inductance of the inductor circuit at the time of valve closing is reduced. Increase or decrease the inductance of the adjustment inductor to increase the inductance, and increase the injection amount. When the injection amount is excessive, the inductance of the inductor circuit at the time of valve opening increases, or the inductor at the time of valve closing A method for adjusting the injection amount of a piezo injector, wherein the injection amount is reduced by increasing or decreasing the inductance of the adjustment inductor so that the inductance of the circuit is reduced. 5. The method for adjusting the injection amount of a piezo injector according to claim 4, wherein the inductance of the adjustment inductor is increased or decreased by changing the number of turns of the coil member.

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