JPH06105062B2 - Fuel injector control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for a fuel injection valve in an internal combustion engine, and in particular, the expansion / contraction action of an electrostrictive actuator opens and closes the valve, so that a predetermined fuel is supplied. The present invention relates to a control device for a fuel injection valve to be injected.

[Conventional technology]

For example, as disclosed in JP-A-59-58129, JP-A-59-18249, etc., a fuel injection valve has been conventionally used in which the valve lift is adjusted by an electrostrictive actuator to control the injection amount of the fuel injection valve. A control device has been proposed.

Japanese Patent Laid-Open No. 59-58129 discloses a structure in which the voltage applied to the electrostrictive actuator is changed by using an analog element such as an operational amplifier or a transistor in accordance with the ejection signal.

[Problems to be Solved by the Invention]

However, such a conventional configuration requires a complicated configuration capable of withstanding a high voltage and a high current, and has a drawback that the voltage applied to the electrostrictive actuator cannot be efficiently controlled.

In view of this point, the present invention has an object to provide a fuel injection valve control device having a simple structure and high efficiency.

[Means for solving problems]

According to the present invention, there is provided a fuel injection valve control device for injecting a predetermined fuel by lifting a nozzle needle according to a contraction amount of an electrostrictive actuator, for charging the electrostrictive actuator. A first current limiting element and a first switching element, which are provided in series between a DC power source and the electrostrictive actuator, and both ends of the electrostrictive actuator for discharging the electric charge of the electrostrictive actuator. A second current limiting element and a second switch element, which are provided in series between them, a capacitor for removing a part of electric charge of the electrostrictive actuator, and a series between the electrostrictive actuator and the capacitor. And a capacitor voltage setting circuit for controlling the voltage of the capacitor to a predetermined voltage. By discharging the electric charge of the electrostrictive actuator through the third current limiting element and the third switch element to the capacitor set to a predetermined voltage, the applied voltage amplitude of the electrostrictive actuator is changed to be different. The technical means of injecting fuel at the injection rate is adopted, and the voltage of the condenser may be changed according to the engine speed.

[Action]

According to the above configuration, by discharging the electric charge of the electrostrictive actuator through the third current limiting element and the third switch element to the capacitor set to the predetermined voltage by the capacitor voltage setting circuit, It acts so as to perform fuel injection at different injection rates by changing the applied voltage amplitude of the formula actuator.

〔Example〕

FIG. 1 shows an embodiment of a drive circuit 47 used in the fuel injection valve control device according to the present invention. 477 is a high voltage power source of 350V, and 478 is a large voltage source connected in parallel to the high voltage power source 477. A capacitor having a capacity supplies a large transient current required for driving the electrostrictive actuator 2. 471 is the first
A thyristor has a gate input to which a first trigger signal is connected from a trigger generation circuit 43 described later. 474 is a first coil having intactance. The capacitor 478, the first thyristor 471, the first coil 474, and the electrostrictive actuator 2 are connected in series. 475 is also a second coil. A second thyristor 472 has a gate input to which the second trigger signal from the trigger generation circuit 43 is connected. The electrostrictive actuator 2, the second coil 475, and the second thyristor 472 are also connected in series.

476 is a third coil, 473 is a third thyristor, and the gate input thereof is connected to the third trigger signal from the trigger generating circuit 43. Reference numeral 479 is a capacitor for removing a predetermined amount of electric charge of the electrostrictive actuator 2, and its capacitance is about three times that of the electrostrictive actuator 2. Electrostrictive actuator 2, third coil 476, third thyristor 4
73 and a capacitor 479 are also connected in series as shown in the figure. Reference numeral 480 is a transistor for controlling the voltage of the capacitor 479, the collector of which is connected to the high voltage side of the capacitor 479 via a current limiting resistor 481. The emitter of transistor 480 is grounded. 484 is an operational amplifier, the output of which is connected to the base of the transistor 480 via the resistor 485. The non-inverting input of op amp 484 is resistor 48
The high voltage of the capacitor 479 divided by 2, 483 is connected. The reference voltage V _R is applied to the inverting input of the operational amplifier 484 via the terminal 486.

Next, the trigger generation circuit 43 will be described. FIG. 2 is a circuit diagram of the trigger generation circuit 43. The pilot injection signal and the main injection signal are input through terminals 431 and 432, respectively, and the first signal is output at the rising edge of the pilot injection signal.
One Shot Multi 436 is triggered. A “0” level signal having a pulse width (about 30 μs) determined by the capacitor 441 and the resistor 442 is output to the output. This signal has resistances 445, 4
It is connected via 51 to the base of a transistor 448. The emitter of the transistor 448 is connected to the power supply, and the collector is connected to the primary side of the pulse transformer 454. When the output of the first one-shot multi 436 is at "0" level, the transistor 448 becomes conductive, current flows in the primary side of the pulse transformer 454, and a signal is generated in the secondary side. This signal is connected to the gate input of the third thyristor 473 via the diode 463 and the resistor 464. The resistor 465 and the capacitor 466 are for noise prevention. The second one-shot multi-435 is triggered by the rising of the main injection signal,
A similar circuit supplies the second trigger signal to the gate input of the second thyristor 472. The pilot injection signal and the main injection signal are ORed by a 2-input OR gate 433 and input to the third one-shot multi 434. The trigger signal is supplied to the gate input of the first thyristor 471 in synchronization with the rising of this signal, that is, in synchronization with the rising of the pilot injection signal and the rising of the main injection signal.

Next, a circuit for generating the pilot injection signal and the main injection signal will be described. FIG. 3 shows the configuration of the computer section. An input interface 411 AD-converts the voltage corresponding to the accelerator opening from the load sensor 53 and the voltage corresponding to the water temperature from the temperature sensor 54, and connects it to the bus line 415. Further, the engine speed is counted by the signals from the reference sensor 52 and the angle sensor 51 and connected to the bus line 415. A CPU 412 takes in the data from the input interface 411 and performs an operation according to a ROM 413 storing various data and programs. 414 is a RAM used for the calculation of the CPU 412. A bus line 415 is a path for exchanging data between various constituent circuits such as the input interface 411. 416 is an output interface, which is the CPU 41
When the data of the calculated injection signal of 2 is set, a predetermined counting operation is performed, and the pilot injection signal and the injection signal are output at a predetermined timing.

The operation of the above configuration will be described. For convenience of explanation, in FIG. 1, the voltage of the capacitor 479 is charged to 325V, and the voltage of the electrostrictive actuator 2 is 500V. Therefore, the electrostrictive actuator 2 is extended and the injection is stopped. At the rising of the pilot injection signal, a third trigger signal is generated (Fig. 4 (C)), and the third thyristor 473 becomes conductive. Electrostrictive actuator voltage is 500
Since it is V and the voltage of the capacitor 479 is 325V,
A current flows from the electrostrictive actuator 2 to the capacitor 479 via the coil 476. Since the electrostrictive actuator 2 and the capacitor 479 are capacitive and the third coil 476 is inductive, series resonance occurs, a sinusoidal current flows through the circuit, and when the current value becomes zero. The third thyristor 473 commutates and becomes non-conductive. At this time, the voltage of the electrostrictive actuator 2 will drop to +150 V if the capacity of the capacitor 479 is infinite and there is no loss in the circuit, but in reality, the capacitor 479 has three times the voltage of the electrostrictive actuator 2. Since it is a capacitance, and its voltage also rises as the current flows, the voltage of the electrostrictive actuator finally becomes 325V (Fig. 4 (F)), and the voltage of the capacitor 479 becomes about 380V (fourth). (Figure (G)). Therefore, the voltage of the electrostrictive actuator 2 is decreased by 175V, and contraction corresponding to the decreased amount of the voltage occurs. First
From Fig. 16, the needle lift amount of the injector 1 at this time is 1/3 of the full lift amount, and the injection amount is also 1/3 (Fig. 4 (H)).

This injection amount characteristic is shown in FIG. Due to the responsiveness limitation, the minimum injection amount was 3 mm ³ when the lift amount was 0.2 mm.
If it is 0.5 mm, 1 mm ³ can be injected as the minimum injection amount. In order to realize this, it is necessary to control the applied voltage of the electrostrictive actuator 2 and finely control the amount of contraction, but this can be realized by the present invention.

Next, after a lapse of time τp (eg 100 μsec) corresponding to a predetermined pilot injection amount (eg 1 mm ³ ), the pilot injection signal falls to “0” level (FIG. 4 (A)). In synchronization with this, the first trigger signal is generated (Fig. 4 (D)),
The first thyristor 471 becomes conductive. Then, a current flows from the power source through the first coil 474, and the electrostrictive actuator is charged to + 500V again (Fig. 4 (F)), so that it extends to the initial length and pushes down the nozzle needle 113 to stop injection. (FIG. 4 (H)). Next, after a lapse of the interval τd between the predetermined pilot injection and the main injection, the main injection signal becomes “1” level this time (FIG. 4 (B)). As a result, the second trigger signal is generated (FIG. 4 (E)), and the second thyristor 472 becomes conductive. Therefore, the electrostrictive actuator 2,
A series resonance circuit composed of the second coil 475 is formed, and the voltage of the electrostrictive actuator 2 drops to −200V (fourth
(Figure (F)). From FIG. 16, at this time, the nozzle needle 113
Performs full lift (0.2 mm) and performs main injection. The main injection amount is determined by the time τm of the "1" level of the main injection signal. A first trigger is generated in synchronization with the fall of the main injection signal (FIG. 4 (D)), and the first thyristor 471 becomes conductive. Then, similarly to the above, the electrostrictive actuator 2
Since + 500V is applied to the nozzle to expand it, the nozzle needle 113
To end the injection (FIG. 4 (H)). By the way, since the capacitor 479 is charged to 380V, the injection amount at the next pilot injection will be further reduced if this is left as it is. You need to set it to 325V as explained at the beginning. The operation will be described below. The voltage (380V) of the capacitor 479 is, for example, 1/100 by the resistors 482 and 483.
Connected to the non-inverting input of op amp 484. Inverting is connected to the reference voltage V _R to the input, this voltage is assumed to be 3.25V, the output of the operational amplifier 484 to conduct the transistor 480 through the now resistor 485 increases.
Therefore, the electric charge of the capacitor 479 is discharged through the current limiting resistor 481 and the voltage of the capacitor 479 decreases. When this voltage drops to 325V, the output of the operational amplifier 484 becomes low, the transistor 480 is cut off, and the voltage no longer drops. That is, the reference voltage V _R × 100
It will be controlled to double the voltage value. Current limiting resistor 481
Assuming that the resistance value is 100Ω and the capacity of the capacitor 479 is 3μF, the time required for discharge is 300μsec or less, and the voltage of the capacitor 479 is the original 325V by the next injection process. Can be realized.

The calculation of the pilot injection signal and the main injection signal is performed by the above-mentioned arithmetic circuit 41 (FIG. 3). Input interface 411
Engine speed N _E , accelerator opening θ, water temperature T
Under a predetermined engine condition from the map read in and stored in the ROM 413 in advance by the bench test. The pilot-main injection time τd and the main injection time τm are calculated using the pilot injection timing θp and the pilot injection time τp. These values are output to the output interface 416. The output interface 416 has a reference signal, an angle signal,
The pilot injection signal and the main injection signal are output at a predetermined timing according to the reference clock signal.

As explained above, the charge of the electrostrictive actuator is
By discharging the capacitor 479 controlled to a constant initial voltage value, it is possible to control the expansion / contraction amount of the electrostrictive actuator to a smaller amount than in the past, so the injector injection operation can be performed with pilot injection and main injection. Injection can be switched to two stages of different flow rates, and in particular, pilot injection has an excellent effect that a minute amount of injection that could not be achieved in the past can be stably and accurately performed.

Next, examples of the present invention will be described. In the previous embodiment, the reference voltage V _R was constant at, for example, 3.25 V, but the injection rate can be continuously changed by changing this voltage. FIG. 6 is a graph showing the relationship of the injection rate when the reference voltage V _R is changed. Originally, the V _R should be (a portion indicated by A) the same level as the conventional full lift of the injection rate if the OV, because the capacitance of the capacitor 479 is not infinite, becomes only about 2/3. At a reference voltage of 2.5 V or higher, the injection rate can be controlled to a near limit. Therefore, by using this part, the reference voltage V _R
The V _R can be controlled injection rate of the injector. The drive circuit of this embodiment is the same as that of FIG. 1, but the arithmetic circuit is different from that of FIG. 3, and the DA conversion circuit 417 generates the reference voltage V _R as shown in FIG. It is like this. In FIG. 7, the DA conversion circuit 417 is connected to the bus line 415, and outputs the reference voltage V _R according to the injection rate calculated by the CPU 412. The control method will be described. As described above, in order to improve the output at the time of high engine rotation, it is necessary to inject a predetermined maximum injection amount (30 mm ³ ) within a limited injection period (30 ° CA). Due to this limitation, the injection rate of the injector is adjusted to the maximum injection amount at the maximum rotation (5000 rpm), so that the injection period becomes too short at low speed or the lower limit of the minimum injection amount is large to perform pilot injection. Although there is a problem that it is too long, according to the present embodiment, the injection is performed at the maximum injection rate by the full lift as in the conventional case at the high speed, but at the low speed, the injection rate is lowered according to the engine speed to perform the slow combustion. As a result, noise and vibration can be reduced.

Now consider that the maximum injection amount required by the engine is 30 mm ³ and that this injection amount is injected within 30 ° CA. Injection quantity q (mm ³ ), injection rate Q (mm ³ / sec), injection period τ (se
c), where the engine speed is N (rpm), q = Q × τ (1) Equation, q = 30 mm ³ , Substituting for, we get Q = 6N (2). Therefore, the relationship between the engine speed N and the reference voltage V _R is as shown in FIG. At 1000 rpm and above, noise and vibration are not a serious problem, so full lift control is performed as before. The above control is performed by the arithmetic circuit 4 shown in FIG.
Perform at 1 '. The CPU 412 takes in the engine speed N, the accelerator opening θ, and the water temperature T from the input interface 411, and calculates the injection amount q and the injection timing θ required by the engine. Further, it is determined whether the engine speed N is 1000 rpm or more, and if it is 1000 rpm or more, the injection period τ is calculated from the equation (1) with Q = 30000 mm ³ / sec, and is output to the main injection signal of the output interface 416. Engine speed N is 1000rp
If m or less, the injection rate Q is calculated from the equation (2), and the injection period τ is calculated from the equation (1).
It outputs to the pilot injection signal of 416. At the same time, the reference voltage V _R for the engine speed N is calculated from FIG.
Output to the conversion circuit 417. FIG. 9 shows changes in the injection rate due to the above operation.

Next, a third embodiment of the present invention will be described. First and second
In this embodiment, the nozzle of the injector is a hole nozzle, but this embodiment is applied to a throttle nozzle. Generally, the relationship between the injection rate and the needle lift of the throttle nozzle is shown in FIG. Unlike the hole nozzle, it has a throttle part, so it has a low injection rate (first
20A) and a high injection rate portion (FIG. 20B).
If the first embodiment is applied to the throttle nozzle, there is a feature that the expansion / contraction amount of the electrostrictive actuator fluctuates to some extent during pilot injection, and the error in the injection rate is small even if the lift amount varies. By controlling the expansion / contraction amount of the electrostrictive actuator in two steps, the injection pattern as shown in FIG. 10 is realized.

FIG. 19 is a structural diagram of an injector using a throttle nozzle. Since the structure is almost the same as that using the hole nozzle of FIG. 14, only the differences will be described. 110 'is a nozzle body, on the center axis of which the needle cylinder 11
There is 1'and there is a nozzle needle in the needle cylinder 111 '.
Nozzle needle 11
The pressure in the pump chamber 105 acts on the upper end surface of 3 '. The upper end surface of the nozzle needle 113 'is a flat surface so that it comes into close contact with the lower end surface of the distance piece 107 when the nozzle needle 113' moves upward. At this time, the through hole 10
8 can be closed. Nozzle needle 11
3'slides in the needle cylinder 111 ', but a part of the outer circumference is cut to have a width across flats and has a slight clearance 112'. The lower part of the nozzle needle 113 'is tapered and the nozzle body 1
Since it is in close contact with the seat portion 115 'of the 10', when the nozzle needle 113 'moves downward, the injection port 11
6'is closed, and when the nozzle needle 113 'moves upward, the injection port 116' is opened to inject fuel. At the lower end of the nozzle needle 113 ', there is a throttle portion 122 having a diameter slightly smaller than that of the injection port 116', and at the tip thereof there is a tapered projection 123 for expanding the spray angle. A throttle is formed by the clearance between the throttle portion 122 and the injection port 116 ', and the area has a low injection rate. When the nozzle needle 113 'is lifted, the overlapping portion between the throttle portion 122 and the injection port 116' disappears and the throttling effect disappears, resulting in a high injection rate region. At the bottom of the needle cylinder, a ring-shaped enlarged fuel reservoir 114 'is provided.
Communicates with the fuel passage 118.

The above is the structural difference from FIG. Next, the operation will be described. The operation is the same as that of the first embodiment.
However, the lift amount of the nozzle needle 113 'is double, 0.4mm
I am doing it.

Next, the control circuit will be described. The arithmetic circuit 41 is the same as that of FIG. 3 and generates a pilot injection signal and a main injection signal. However, only the rising timing of the pilot injection signal is important, and the pulse width has no meaning. The drive circuit 47 is a trigger generation circuit different from that of FIG.
Only 43 is different. FIG. 11 shows a trigger generation circuit 43 'in this embodiment. The difference from FIG. 2 is that the 2-input OR gate is eliminated and the main injection signal is directly connected to the trigger input of the third one-shot multi 434. The operation of the above configuration will be described.

FIG. 12 is a time chart used for the invention. For explanation, the electrostrictive actuator 2 is set to 500V and the capacitor 47
9 V _R is to be put into a 3.25V to 325V. First, the third trigger signal is generated at the rising of the pilot injection signal (Fig. 12 (C)). As a result, the third thyristor 473 becomes conductive, and the voltage of the electrostrictive actuator drops to 325V as described in the first embodiment. (Fig. 12 (F)). For this reason, the needle 113 'is moved by 0.1 mm, which is 1/4 of the full lift.
Lifts and performs the injection in the low injection rate region as shown in FIG. 20 (FIG. 12 (H)). Next, the second trigger signal is generated at the rise of the main injection signal (FIG. 12 (D)), and the second thyristor 472 is made conductive. Therefore, the voltage of the electrostrictive actuator 2 drops to -200V (Fig. 12 (F)),
Since the needle 113 'is fully lifted, injection is performed in the high injection rate region shown in FIG. 20 (FIG. 12 (H)). When the main injection signal falls after the predetermined injection period, the first trigger signal is generated (FIG. 12 (E)), and the first thyristor 471 becomes conductive.
Since the electrostrictive actuator 2 is charged to 500V (Fig. 12 (F)), the needle 113 'is pushed down and the injection is stopped (Fig. 12 (H)). As described in the first embodiment, the voltage of the capacitor 479 is returned to the predetermined 325V by the next injection stroke.

As described above, in the third embodiment, the injection rate can be changed during one injection period by using the low injection rate area and the high injection rate area of the throttle nozzle.
The initial injection rate can be reduced, which is effective in reducing noise and vibration. Furthermore, in the low injection rate region, the injection rate does not change due to the throttle part, even if the lift amount fluctuates slightly,
There is a feature that there is little error.

〔The invention's effect〕

As described above, according to the present invention, the amount of charge accumulated in the electrostrictive actuator is directly discharged to the capacitor via the switching element such as a thyristor, which not only simplifies the circuit configuration, Since the switching element is on / off control, there is little loss and the problem of heat generation is almost solved. Further, the high voltage can adjust the applied voltage to the electrostrictive actuator by setting the voltage of the capacitor without directly changing the applied voltage to the electrostrictive actuator, and the applied voltage can be easily adjusted. .

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a drive circuit for an electrostrictive actuator in a fuel injection valve control device used for carrying out a control method according to the present invention, and FIG. FIG. 3 is a circuit diagram showing an embodiment of a trigger signal generating circuit in the valve control device, and FIG. 3 is a block diagram showing an embodiment of a circuit for arithmetically generating a pilot injection signal and a main injection signal in the fuel injection valve control device. 4, FIG. 4 is a timing chart for explaining the operation when the drive circuit shown in FIG. 1 is driven by the trigger signal generating circuit shown in FIG. 2, and FIG. 5 is shown in FIG. FIG. 7 is a diagram showing an injection amount characteristic of a fuel injection valve when a drive circuit is used. FIG. 6 is a diagram showing an injection characteristic when the reference voltage input to the drive circuit shown in FIG. 1 is changed. The figure shows the above pyro FIG. 8 is a block diagram showing another embodiment of the operation generation circuit for the injection signal and the main injection signal, and FIG. 8 shows a case where the reference voltage is changed according to the engine speed using the circuit shown in FIG. FIG. 9 is a timing chart showing an example of controlling the injection rate in accordance with the engine speed using the circuit shown in FIG. 7, and FIG. 10 shows the present invention. FIG. 11 is a timing diagram for explaining the operation of the throttle nozzle type fuel injection valve when applied to the fuel injection valve. FIG. 11 is a circuit diagram showing another embodiment of the trigger signal generation circuit shown in FIG. FIG. 12 is a timing chart for explaining the operation when the drive circuit shown in FIG. 1 is driven by the trigger signal generation circuit shown in FIG. 11, and FIG. 13 is a fuel controlled by the present invention. The general structure of the internal combustion engine including the injection valve is FIG. 14 is a cross-sectional view showing the structure of a fuel injection valve controlled by the present invention, FIG. 15 is a timing diagram showing an example of controlling the fuel injection valve according to the prior art, FIG. 16 is a diagram showing the injection characteristic of the fuel injection valve shown in FIG. 14, FIG. 17 is a diagram showing an example of a drive circuit of an electrostrictive actuator in the prior art, and FIG. 18 is shown in FIG. FIG. 19 is a timing diagram for explaining the operation of the drive circuit shown in FIG. 19, FIG. 19 is a sectional view showing the structure of a throttle nozzle type fuel injection valve controlled by the present invention, and FIG. 20 is shown in FIG. It is a figure which shows the injection characteristic of fuel injection. (Description of symbols) 1 ... Fuel injection valve 2 ... Electrostrictive actuator 4 ... Control circuit 41, 41 '... Operation circuit 43, 43' ... Trigger pulse generation circuit 47 ... Electrostrictive actuator drive circuit 471 …… First thyristor 472 …… Second thyristor 473 …… Third thyristor 479 …… Capacitor for removing a part of actuator charge 484 …… Op-amp 49 …… Conventional electrostrictive gutator drive circuit 5 …… Diesel engine

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Sakakibara 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Stock Company Japan Automotive Parts Research Institute (72) Inventor Masahiro Takigawa 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Stock Association (56) Reference JP-A-59-58129 (JP, A) JP-A-59-18249 (JP, A)

Claims (4)

[Claims] 1. A fuel injection valve control device for injecting a predetermined fuel by lifting a nozzle needle according to a contraction amount of an electrostrictive actuator, wherein a direct current is supplied to charge the electrostrictive actuator. A first current limiting element and a first switching element, which are provided in series between a power source and the electrostrictive actuator, and between both ends of the electrostrictive actuator for discharging electric charge of the electrostrictive actuator. A second current limiting element and a second switching element provided in series, a capacitor for removing a part of electric charge of the electrostrictive actuator, and a series connection between the electrostrictive actuator and the capacitor. The third switch element is provided, and a capacitor voltage setting circuit for controlling the voltage of the capacitor to a predetermined voltage, the capacitor voltage setting circuit By discharging the electric charge of the electrostrictive actuator through the third current limiting element and the third switch element to the capacitor set to a constant voltage, the applied voltage amplitude of the electrostrictive actuator is changed to perform different ejection. A control device for a fuel injection valve, characterized in that fuel injection is performed at a rate. 2. The control device for a fuel injection valve according to claim 1, wherein the electrostrictive actuator is composed of a piezoelectric element. 3. The voltage of the capacitor can be changed according to the engine speed.
A control device for a fuel injection valve according to the item. 4. A control device for a fuel injection valve according to claim 1, wherein a throttle nozzle is used as a nozzle of the fuel injection valve.