JPH02199255A - Fuel injection control device for diesel engine - Google Patents

Abstract

PURPOSE:To ensure an enough energizing time of a primary current even during acceleration and to enable execution of suitable pilot injection by a method wherein when the acceleration state of a vehicle is detected, the energization starting time of the primary current of a high voltage generating means is advanced. CONSTITUTION:In the fuel injection control device of a diesel engine, the primary current of a boosting part V1 of a high voltage generating means M2 is shut off by a high voltage applying means M3 based on the pressure of a pressurizing chamber P1, a high voltage generated on the secondary side is applied on an electrostriction type actuator M1 to effect expansion contraction drive. In order to ensure a high voltage required for the expansion and contraction, an energization control means M4 usually regulates the energization starting timing of a primary current according to the number of revolutions of an engine. Meanwhile, when the acceleration state of a vehicle is detected by a detecting means M5, an energization starting timing regulated by M4 is advanced by an energization starting timing correction means M6. This constitution ensures an enough energizing time of a primary current even during acceleration and enables realization of suitable pilot injection.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for a diesel engine that performs pilot injection using expansion and contraction of an electrostrictive actuator.

[Prior Art] Fuel injection control devices for diesel engines that perform pilot injection using expansion and contraction of an electrostrictive actuator have been known, for example, as disclosed in Japanese Patent Application Laid-open Nos. 61-25925 and 1982. -279234 or JP-A-63-687
There is a proposal for No. 46.

These proposed devices are equipped with a high voltage generation circuit having a booster section, and when the pressure in the pressurizing chamber of the fuel injection pump reaches a predetermined value, the primary current of the circuit is cut off and the high voltage generated on the secondary side is removed. A voltage is applied to the electrostrictive actuator to cause it to expand and contract, thereby rapidly changing the pressure in the pressurizing chamber and executing a pilot injection. Therefore, in order to generate a high voltage commensurate with the amount of expansion and contraction of the electrostrictive actuator required for pilot jet stripping, it is necessary to ensure a sufficient time for the primary current to flow through the high voltage generation port Y3. Therefore, in the conventional device, the energization time is secured by adjusting the energization start time of the primary current according to the rotation speed of the diesel engine. Specifically, for example, in a 4-cylinder engine, the time required for the crack shaft to rotate half a revolution (hereinafter referred to as 18
The current temperature of 180°C is based on the 0°CA time).
A time T180 minus the time required for primary current energization (hereinafter referred to as required energization time) TD is the time from the current primary current cutoff to the next primary current energization start (hereinafter referred to as cutoff time) TQFF The timing for starting energization was determined as follows.

[Problem to be solved by the invention] However, when the rotation speed of the diesel engine changes rapidly between strips, such as during vehicle acceleration, the next energization start time is set to the current 180° CA time T180. If the determination is made based on this, there is a problem that the required energization time TD cannot be secured and the effect of the pilot injection cannot be sufficiently obtained, and in some cases, there is a problem that the pilot injection is not performed.

It is an object of the fuel injection control device for a diesel engine of the present invention to prevent such problems and to realize suitable pilot injection even during acceleration.

Structure of the Invention [Means for Solving the Problems] As illustrated in FIG. 1, the fuel injection control device for a diesel engine of the present invention includes a variable volume chamber communicating with a pressurizing chamber p1 of a fuel injection pump of a diesel engine. an electrostrictive actuator M1 provided facing p2, and a step-up section v1 that generates a high voltage in a secondary circuit by interrupting the primary current, and the electrostrictive actuator M1 is connected to the secondary circuit. a high voltage generating means M2; a high voltage applying means M3 for cutting off the primary current and applying a high voltage to the electrostrictive actuator M1 based on the pressure in the pressurizing chamber p1; and depending on the rotational speed of the diesel engine. The high voltage generating means M
A fuel injection control device for a diesel engine, comprising: an energization control means M4 that secures the energization time of the primary current by adjusting the energization start time of the primary current to 2, the acceleration state detection means M5 that detects the acceleration state of the vehicle; and energization start timing correcting means M6 for advancing the energization start time by the energization control means M4 when a predetermined acceleration state is detected by the acceleration state detection means M5.

[Function] The fuel injection control device for a diesel engine having the above-mentioned configuration generates a high voltage by blocking the primary current of the boosting part v1 of the high voltage generating means M2 based on the pressure in the pressurizing chamber p1. A high voltage is generated on the secondary side of the voltage generating means M2, and this high voltage is applied to the electrostrictive actuator M1 to drive it to expand and contract. At this time, in order to ensure the high voltage necessary for the expansion and contraction, the energization control means M4 normally adjusts the start time of energization of the primary current according to the rotational speed of the diesel engine.

On the other hand, when the acceleration state detection means M5 detects the acceleration state of the vehicle, the energization start time correction means M6 advances the energization start time by the energization control means M4. As a result, the primary current supply time to the high voltage generating means M2 can be secured even during acceleration, and the high voltage generating means M
A high voltage sufficient to expand and contract the electrostrictive actuator M1 by the required amount can be generated in the secondary circuit of No. 2.

[Example 4] Next, a fuel injection control device for a diesel engine according to the present invention will be described.
An embodiment applied to a distribution type fuel injection pump for a cylinder engine will be described. FIG. 2 shows the system configuration of this embodiment.

As shown in FIG. 2, a fuel injection control device 1 for a diesel engine is fitted into a distributor head 2 of a distribution type fuel injection pump and controls four cylinders (
A plunger 3 that pressurizes and pressure-feeds fuel to a fuel tank (not shown), a pressurizing chamber 4 surrounded by the tip of the plunger 3 and the distributor head 2, and a pressurizing chamber 4 through a fuel passage 3a provided in the plunger 3. 4, an electrostrictive actuator 6 provided facing the variable volume chamber 5, and a high voltage generating circuit 7 that applies a high voltage to the electrostrictive actuator 6 to cause it to expand and contract. accelerator pedal 8
An electronic control unit 10 (hereinafter referred to as ECU) controls energization of the high voltage generating circuit 7 and executes various controls based on various detected values by the accelerator sensor 9 and the like. ).

The plunger 3 rotates in accordance with the rotation of the diesel engine, and is reciprocated in the axial direction by the riding motion of a face cam (not shown) and a cam roller (not shown). Through this rotation and reciprocating motion, the plunger 3 pressurizes the fuel sucked in through the suction boat 3b in the pressurizing chamber 4, and transfers the fuel provided in each cylinder via the distribution boat 3c and the delivery valve 3d. Fuel is force-fed to the injection valve 3e at a predetermined timing. Furthermore, the end timing of fuel pressurization, that is, the end timing of fuel injection, is adjusted by the axial position of a spill ring 3g that is fitted externally so as to close a spill bow 3f provided at the left end of the fuel passage 3a in the drawing.

The electrostrictive actuator 6 includes a piezoelectric element 6b inside a piston 6a provided facing the variable volume chamber 5. The piezoelectric element 6b is a plurality of disc-shaped members made of PZT, which is a ceramic material whose main component is lead zirconate titanate, with electrodes interposed therebetween. When a charge is applied from the high voltage generation circuit 7 via the signal line 6c, the piezoelectric element 6b expands upward in the figure to reduce the volume of the variable volume chamber 5. As a result, the pressure in the pressurizing chamber 4 increases. On the other hand, when the charge is removed via the signal line 6c, the piezoelectric element 6
b contracts in the opposite manner to the above, increasing the volume of the variable volume chamber 5. As a result, the pressure in the pressurizing chamber 4 decreases. On the other hand, since the fuel pressure in the pressurizing chamber 4 acts as a compressive force on the piezoelectric element 6b, the piezoelectric element 6b generates a piezoelectric element voltage VPZT having a value corresponding to the strain caused by the compressive force. ECUI
O can detect this voltage value via the signal line 6c.

The high voltage generation circuit 7 has an in-vehicle dispersion 20 as a primary side.
resistor connected in series with? a, a primary winding 7b, and a primary side transistor c. An energization control signal Sl from the ECUIO is applied to the base of the primary side transistor Fc. Further, the secondary side of the high voltage generation circuit 7 includes a secondary winding 7d, a resistor 7e, and a secondary side transistor 7f connected in series with the piezoelectric element 6b. Secondary side transistor 7
A discharge control signal S2 from ECUlo is given to the base of f. Naq? , a diode 7g is connected in parallel to the secondary side transistor 7f.

In addition to the accelerator sensor 9, the fuel injection control device 1 also includes a rotation speed sensor 91. which detects the rotation speed of the diesel engine. A water temperature sensor 92 that detects the water temperature of the diesel engine. It is equipped with various detectors such as a crank angle sensor 93 that detects the crank angle of the diesel engine.

EC[Jlo is the well-known CP[Jloa, ROMl0
b, RAM 10c, timer 10d, one-person output unit 10f, and a common bus 10e that interconnects these
It is configured as a logic operation circuit. Detection signals of each of the above-mentioned sensors 9, 91 to 93, etc. and piezoelectric element voltage V PZ
T is manually input to the CPU 10a via the human output section 10f, and on the other hand, the CPU 10a outputs control signals S1 and S2 to the high voltage generation circuit 7 via the human output section 10f.

Next, each control signal S1. S2 and electrostrictive actuator 6
The relationship with the operation will be explained.

As shown in the timing chart of FIG. 3(a), when the energization control signal S1 is applied to the base of the primary transistor 7c, the transistor 7c is turned on, and the primary current 1 is not energized in the high voltage generation circuit 7. Started (time [(
1). In this state, no high voltage is generated in the secondary circuit, and the piezoelectric element 6b remains in its contracted state. By the way, the plunger 3 performs a fuel pressurizing operation in synchronization with the rotation of the diesel engine, and when the pressure in the pressurizing chamber 4 increases, the piezoelectric element voltage V PZT of the piezoelectric element 6b also increases correspondingly. . The ECU 10 detects this piezoelectric element voltage V PZT;
When PZT reaches a predetermined value V Tll, the primary side transistor C is turned off (time H2).

As a result, a high voltage is instantaneously generated in the secondary circuit of the high voltage generation circuit 7, and this high voltage is applied to the piezoelectric element 6b (time H3). As a result, the piezoelectric element 6b expands, the pressure in the pressurizing chamber 4 rises rapidly, and pilot injection is started.

Thereafter, when a predetermined short time TA has elapsed, the ECU 10 applies a discharge control signal S2 to the secondary side transistor 7f for a predetermined time TB (times H4 to H6').

As a result, the secondary side circuit of the high voltage generation circuit 7 is short-circuited, and the discharge current I2 from the piezoelectric element 6b flows. (Time H
4-H5). Along with this, the piezoelectric element 6b contracts, and the pressure in the pressurizing chamber 4 suddenly decreases, thereby ending the pilot injection.

Thereafter, control signals Sl, S are sent to the high voltage generation circuit 7 in the same manner.
2 repeatedly to perform fuel injection with pilot injection.

The value of the high voltage generated by the high voltage generating circuit 7 is determined by the conduction time TC of the primary current (1) controlled by the conduction control signal S1. The end time of the primary current 1 is determined by the piezoelectric element voltage V PZ corresponding to the pressure in the pressurizing chamber 4, as described above.
Therefore, the actual energization time is determined by the primary current cutoff time T determined by the energization control process shown in FIG.
Determined by OFF. The energization control process for controlling the cutoff time TOFF to ensure the required energization time TO will be explained based on the timing chart of the 81 signal in FIG. 3(b) and the flowchart in FIG. 4.

In the energization control process, first, based on the detected value of the crank angle sensor 93, the previous and current 180° CA time T18
0', calculate T180 (step 100.11
0). Next, based on the detected value of the accelerator sensor 9, the accelerator change rate ACC is calculated from the accelerator opening change amount within a predetermined time.
Calculate P (Step 120). The calculated accelerator change rate ACCP is compared with the reference accelerator change rate ACCPO to determine whether the vehicle is in an acceleration state (step 130). The reference accelerator change rate ACCPO is a value for determining a transient state in which the engine speed suddenly changes, and can be predetermined depending on the engine type and the like. Note that the reference accelerator change rate ACCPO may be made variable depending on the engine speed.

When the accelerator 8 is depressed and ACCP≧A CCPO, it is determined that the vehicle is in a predetermined acceleration state, and the flag F indicating the acceleration state is set to 1 (step 140), and the cutoff time TOFF is calculated based on the following formula. (Step 15
0).

TOFF =T180-(T180'-T18
0)-TD...(1) Here, the required energization time TO in this embodiment is the energization time required to generate a high voltage of, for example, 400 V in the secondary side circuit of the high voltage generation circuit 7. , rotation speed sensor 9
1. Based on the detected value of the water temperature sensor 92, etc., the ROM 10b
This is the value found from the map within.

Thereafter, when the driver finishes depressing the accelerator, a negative determination is made in step 130, and the process proceeds to step 160 and subsequent steps.

In step 160, it is determined whether flag F is 1 or not. Immediately after step 130 becomes a negative determination, since F=1, the process proceeds to step 170 and counts up the elapsed time counter C after the accelerator operation. Next, it is determined whether the value of counter C exceeds a predetermined value (In CO).
Step 180).

If the counter C is less than the predetermined value CO, step 15
0 and calculates the cutoff time TOFF based on equation (1). The predetermined value f[cO represents the time during which the acceleration transient state occurs after the accelerator is operated, and is set in advance in the ROM 10b.

On the other hand, after a predetermined time has elapsed since the accelerator operation, the flag F is set to 0 (step 190), and the cutoff time TOFF is calculated based on equation (2) (step 200).

TOFF=T180-TD (2) After that, if the vehicle is in a steady state, step 13
0 and 160 are both negative, the counter C is reset (step 210), and the cutoff time TOFF is calculated based on equation (2) (step 200).

As explained above, in this embodiment, in the acceleration state, the primary current cutoff time T OFF until the next start of energization is calculated based on equation (1), so that energization is performed according to the current rotation speed. Time interval (T1 shown by the dotted line in Figure 3 (b))
It is possible to start supplying the primary current to the high voltage generation circuit 7 at a time earlier than the supply start time determined by 8O-TO). Therefore, even in the acceleration state, the required energization time TD
li: [can be maintained, and suitable pilot injection by the fuel injection control device 1 can be realized. As a result, noise and shaking during acceleration can be reduced.

Furthermore, since the system is configured to determine that an acceleration transient state exists when the accelerator change rate ACCP exceeds a predetermined value ACPO (step 130), trivial accelerator operations during driving are not detected.

Furthermore, after ACCP≧ACCPO, C
Since the configuration is such that the correction control based on equation (1) is executed only during the period 0 (step 180), the correction control can be executed only during acceleration transients that truly require correction.6 In other words, in this embodiment, Only for acceleration transient conditions that truly require correction (1
), otherwise (
2) Since the energization start time is determined based on the formula, rotational fluctuations occurring during steady operation are not captured.

Therefore, over-correction due to rotational fluctuations does not occur, the power consumption can be reduced, and the capacity of the vehicle battery 20 does not need to be increased more than necessary.

In addition, when making corrections in response to sudden changes in engine speed, the conditions for making corrections are not determined by changes in engine speed, but by the accelerator change rate, and the amount of correction is determined by changes in engine speed. There is no possibility of detecting rotational fluctuations (instantaneous rotational speed changes due to variations in fuel injection amount to each cylinder, etc.) during steady operation and making incorrect corrections.

Note that instead of formula (1), a configuration may be used in which the primary current energization start time is always advanced by a predetermined period of time in the acceleration transient state to prevent pilot rJfA injection failure in the acceleration transient state. Furthermore, if the fuel injection amount command value well represents the change in accelerator opening degree, the start time of the correction control may be determined based on the case where the fuel injection command value changes suddenly instead of the accelerator change rate. Furthermore, in the correction control, for example, simply the correction amount (T 180' -
1" 180) and subtract that value from the open T OFF at shutoff calculated in step 200.

Furthermore, the same control can be performed not only during acceleration but also during deceleration by setting the value of ACCPO to a negative value and setting ACCP≦ACCPO in step 130. In this case, the effect of saving power consumption is large. It is.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. be.

As explained above, according to the fuel injection control device for a diesel engine of the present invention, the primary current of the high voltage generating means is started earlier in the acceleration state, so that the primary current is increased even during acceleration. This makes it possible to secure sufficient energization time and realize suitable pilot injection. As a result, noise and vibration during acceleration can be reduced.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram illustrating the configuration of the present invention, Figure 2 is a system configuration diagram of an embodiment of the present invention, and Figure 3 (A) is an E
A timing chart showing the relationship between the control signal by CUIO and the voltage applied to the piezoelectric element, (b) a timing chart showing the energization control signal S1 during acceleration transition,
FIG. 4 is a flowchart showing step 11 [6] of the energization control process of the embodiment. Ml... Electrostrictive actuator M2... High voltage generation means M3... High voltage application means M4... Energization control means M5... Acceleration state detection means M6... Energization timing correction means 1...・Diesel engine fuel injection control device 2...
- Distributor head section 3... Plunger 4... Pressurizing chamber 5... Variable volume chamber 6... Electrostrictive actuator 6b... Piezoelectric element 7
...High voltage generation circuit 7b...Primary winding 7d...Secondary winding 8...Accelerator pedal 9...Accelerator sensor lO...Electronic control unit (ECU) Agent: Patent attorney Tsutomu Sadatachi (2 idiots) Figure 1

Claims (1)

[Scope of Claims] An electrostrictive actuator provided facing a variable volume chamber communicating with a pressurizing chamber of a fuel injection pump of a diesel engine, and a booster that generates a high voltage in a secondary circuit by interrupting the primary current. and a high voltage generating means having the electrostrictive actuator connected to the secondary circuit, and applying a high voltage to the electrostrictive actuator by cutting off the primary current based on the pressure in the pressurizing chamber. and energization control means for securing the energization time of the primary current by adjusting the start timing of energization of the primary current to the high voltage generating means according to the rotation speed of the diesel engine. The fuel injection control device includes an acceleration state detection means for detecting an acceleration state of the vehicle, and an energization start timing correction for advancing the energization start time by the energization control means when a predetermined acceleration state is detected by the acceleration state detection means. A fuel injection control device for a diesel engine, comprising: means.