JPH04175438A - Fuel injection controller - Google Patents

Abstract

PURPOSE:To maintain characteristic of a proper pilot injection quantity by reflecting a deviation of real opening/closing operation from target opening/ closing operation for a fuel injection valve at the time of pilot injection, on the control of a pressure adjusting means from the next time based on a pilot injection control means. CONSTITUTION:A pressure adjusting means M3 is controlled by a pilot injection control means M4 so that it can perform pilot injection in such a way as the valve body of a fuel injection valve M1 makes in the target opening/closing operation pressure-fed stroke of a fuel injection pump M2. In this case, the operation of the valve body of the fuel injection valve M1 is detected by a valve body operation detecting means M5. A deviation of real opening/closing operation of the valve body of the fuel injection valve M1 at the time of the pilot injection from the target opening/closing operation of the valve body of the fuel injection valve M1 by the pilot injection control means M4 is reflected on the control of the pressure adjusting means M3 from the next time based on the pilot injection control means M4 by a corrective control means M6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control device for a diesel engine.

[Conventional technology]

In diesel engines, pilot injection is performed prior to main injection in order to reduce harmful components (such as NOx) in exhaust gas. In Japanese Unexamined Patent Publication No. 63-285244 and Japanese Utility Model Application No. 63-202752, in order to make pilot injection a target characteristic, the movement of the valve body of an electromagnetic spill valve provided in a fuel injection pump is used as a sensor. The spill valve opening/closing timing is corrected based on the detection signal.

[Problem to be solved by the invention]

However, fuel injection valves commonly used in diesel engines are equipped with a valve body that is biased in the closing direction by a spring, and when the fuel pressure becomes greater than the biasing force of the spring, the valve body opens. The fuel is then injected. This fuel injection valve operates independently of the electromagnetic spill valve, and as the biasing force of the spring of the fuel injection valve decreases over time, the valve opening pressure of the valve body decreases. That is, if the oil delivery characteristics from the fuel injection pump do not change, the fuel injection valve will open earlier and close later, and the amount of fuel injected will increase accordingly.

This change in the valve opening pressure of the fuel injection valve over time generally ranges from a few percent to as much as 20% depending on the conditions. Under these conditions, even if the pilot injection amount is initially adjusted optimally, the injection amount will change over time. will increase significantly, resulting in a significant deterioration of exhaust gas. Furthermore, it is difficult to believe that the drop in the opening pressure of the fuel injection valve is uniform for each cylinder.Also, considering initial product tolerances, it is extremely difficult to make pilot injection have the same characteristics for all cylinders. .

An object of the present invention is to provide a fuel injection control device that can maintain optimal pilot injection amount characteristics.

[Means to solve the problem]

As shown in FIG. 1, this invention is a fuel injection system that includes a valve body that is biased in the valve closing direction by a spring, and that when the fuel pressure becomes greater than the biasing force of the spring, the valve body opens and injects fuel. a valve Ml, a fuel injection pump M2 that supplies high-pressure fuel to the fuel injection valve M1 during a pressure-feeding stroke, and a fuel injection pump M2 that adjusts the pressure of the high-pressure fuel to the fuel injection valve M1 during the pressure-feeding stroke of the fuel injection pump M2. A pressure regulating means M3 for causing pilot injection by the fuel injection valve N11 and a pilot injection are controlled by controlling the pressure regulating means M3 so that the valve body of the fuel injection valve Ml performs a target opening/closing operation. A pilot injection control means M4, a valve body operation detection means M5 that detects the operation of the valve body of the fuel injection valve Ml, and a valve body operation detection means M5 that detects the operation of the valve body of the fuel injection valve Ml during pilot injection. The deviation between the actual opening/closing operation and the target opening/closing operation of the valve body of the fuel injection valve M1 by the pilot injection control means M4 is determined from the next time by the pilot injection control means M4.

The gist of the present invention is a fuel injection control device including a correction control means M6 that is reflected in the control of the pressure adjustment means M3.

[Effect]

The pilot injection control means M4 controls the pressure adjustment means M3 so that the valve body of the fuel injection valve Ml performs the target opening/closing operation, and adjusts the pressure of high-pressure fuel to the fuel injection valve Ml during the pressure feeding stroke of the fuel injection pump M2. Adjust to perform pilot injection. , and the correction control means M6 detects the actual opening/closing operation of the valve body of the fuel injection valve Ml by the valve body operation detection means M5 during pilot injection, and the pi-lot injection control means M
The deviation from the target opening/closing operation of the valve body of the fuel injection valve M1 due to the operation of the fuel injection valve M1 is reflected in the next control of the pressure adjustment means M3 by the pilot injection control means M4. Therefore, even if the biasing force of the spring of the fuel injector Ml changes over time or the biasing force of the spring of the fuel injector Ml differs in each cylinder of the engine, optimal pilot injection amount characteristics are ensured. .

[Example] An example embodying the present invention will be described below with reference to the drawings.

FIG. 2 shows an inner cam type distribution fuel injection pump 50. As shown in FIG. A drive shaft 2 that rotates in synchronization with the rotation of the day cell engine is inserted into the pump housing l.
It is rotatably supported via a bush 3. At the tip of the drive shaft 2 (right side in Figure 2) is a distribution rotor 4.
are formed in one piece, the distribution rotor 4 of which is rotatably housed in a cylinder 6 provided in the distribution head 5.

At the outer end of the distribution head 5 (on the right side in FIG. 2) is a vane feed pump 8 for pumping fuel from the fuel tank 7.
is provided. This vane feed pump 8 includes a casing 9 attached to the cylinder 6 and a distribution rotor 4.
A plurality of vanes 11 are slidably fitted into the pump rotor lO.

Then, when the pump rotor 10 is rotated in synchronization with the rotation of the distribution port 4, fuel is pumped up from the suction port 12,
Pressurized fuel is discharged from the discharge port 13. moreover,
After the pressure of the fuel is regulated by a pressure regulating valve 14, it is discharged into an annular gear rally 15 formed in the distribution head 5.

The cylinder 6 is formed with a plurality of intake passages 16 communicating with the gear rally 15, a plurality of distribution passages 17 for supplying fuel to each cylinder of the engine, and a plurality of spill passages 18. Each distribution passage 17 communicates via a distribution passage 19 provided in the distribution head 5 with a delivery valve 20 for supplying fuel to each cylinder of the engine.

A cylindrical hole 21 is formed in the distribution rotor 4, and a pair of plungers 22 are slidably housed in the cylindrical hole 21 in an oil-tight state.
is formed.

A shoe 2 is provided at the radially outer end of each plunger 22.
4, and a roller 25 is rotatably held in the shoe 24. An inner cam ring 26 having a plurality of cam ridges on the inner surface is arranged on the outer surface of the roller 25. Then, based on the rotation of the distribution rotor 4, the roller 25 slides on the cam surface on the inner periphery of the inner cam ring 26, so that the roller 25 reciprocates in the radial direction of the inner cam ring 26 along the cam surface. This reciprocating motion is transmitted to the plunger 22 via the shoe 24.

The stroke in which the plunger 22 moves outward in the radial direction of the distribution rotor 4 is a suction stroke in which fuel is taken in, and the stroke in which the plunger 22 moves inward in the radial direction is a pressure stroke (discharge stroke) in which the fuel pressurized in the plunger chamber 23 is discharged. ).

The distribution rotor 4 has an intake passage 28 communicating with the plunger chamber 23 via a fuel passage 27 passing through the center of the rotor 4.
, a distribution passage 29, and a spill passage 30 are formed. Based on the rotation of the distribution rotor 4, this suction passage 28
It is arranged so as to communicate with the suction passage/path 16 of the cylinder 6 during the fuel suction stroke, and to close during the pumping stroke. The distribution passage 29 and the spill passage 30 communicate with each distribution passage 17 and each spill passage 18 of the cylinder 6 during the pressure feeding stroke.

Further, a spill passage 49 is provided at the end of the spill passage 18 and communicates with the gear rally 15.
A spill valve 31 is provided in the middle of the pipe 9 as a pressure regulating means. This spill valve 3] employs a spill valve using an electrostrictive actuator. That is, the cylinder 32
A piston 33 is housed inside, and the piston 33 slides on the inner peripheral surface of the cylinder 32 in an oil-tight manner. Also, inside the cylinder 32 are a piezo stack 34 and a coil spring 35.
is arranged, and the coil spring 35 is connected to the piezo stack 3
4 is placed in a compressed state so that a force in the direction of contraction (preset load) is applied.

Then, when a voltage is applied, the piezo stack 34 expands and slides the piston 33 downward. This piston 3
3 pressurizes the inside of the pressure chamber 36 and the spill passage 4
A valve body 37 that opens and closes the valve 9 is closed against the biasing force of a spring 38. When the voltage application to the piezo stack 34 is removed from this state, the valve body 37 opens.

Then, when the drive shaft 2 is rotationally driven by the engine, the fuel injection pump 50 is activated by the feed pump 8.
The pressure of the fuel discharged from the fuel tank is regulated by the pressure regulating valve 14. After that, the fuel is transferred to the gear rally 1 during the intake stroke of the plunger 22.
5 into the plunger chamber 23. The fuel sucked into the plunger chamber 23 is fed under pressure to the delivery valve 20 of each cylinder in accordance with the injection order during the pressure feeding stroke (discharge stroke) of the plunger 22.

Further, the delivery valve 20 includes a fuel injection valve 3 shown in FIG.
9 is connected to each cylinder. In the same figure, a nozzle needle 41 as a valve body is disposed in a nozzle body 40 of a fuel injection valve 39, and the nozzle needle 41 is urged downward by a pressure spring 43 via a pressure pin 42 to form a nozzle body. The seat surface C of 40 is closed. The high-pressure fuel during the pressure stroke of the fuel injection pump 50 passes through the oil passage 44 in the nozzle body 40 and reaches the oil reservoir 45 on the lower side of the nozzle body 40 . As the pressure of this oil reservoir 45 increases, a force that pushes the end face of the nozzle needle 41 works, and when the force becomes larger than the biasing force of the pressure spring 43, the nozzle needle 4
1 is pushed up and fuel is injected. When the pressure feeding of fuel from the fuel injection pump 50 is completed, the pressure in the oil reservoir 45 decreases, and the nozzle needle 41 is brought into close contact with the seat surface C of the nozzle body 40 by the pressure spring 43, and injection ends.

Then, in the pressure feeding stroke of the fuel injection pump 50, pilot injection is performed at a timing prior to the main injection. That is, when the pressure in the pressure chamber 36 of the spill valve 31 in the fuel injection pump 50 is reduced, the valve body 37 is operated to open and the plunger chamber 2 is opened.
No. 3 fuel is depressurized and pilot injection is performed.

Further, the fuel injection valve 39 is provided with a nozzle lift sensor 46 as a valve body operation detection means.

That is, a magnetic body 47 is provided on the upper surface of the pressure pin 42, and a detection coil 48 is arranged opposite to the magnetic body 47. Then, when fuel is pumped from the fuel injection pump 50 and the nozzle needle 41 is lifted, the magnetic body 47 approaches the detection coil 48 and the inductance of the coil 48 changes. This change in inductance is the change in nozzle needle 4.
This corresponds to a lift amount of 1.

In FIG. 2, 51 is a hydraulic timer, and the fuel injection timing is adjusted by rotating the inner cam ring 26 via a slide pin 53 so as to correspond to the position of the timer piston 52. There is.

Next, the electrical configuration of the fuel injection control device will be explained based on FIG. 4.

Engine control unit (hereinafter referred to as ECU)
54, a microcomputer 55 as a pilot injection control means and a correction control means, and a waveform shaping circuit 56.
58, an A/D converter 59, a D/A converter 60, and a drive circuit 61. The microcomputer 55 includes a central processing unit (hereinafter referred to as CPU) 62, a ROM 63, and a ROM 63.
It is composed of AM64.

The rotation angle sensor 65 outputs a signal accompanying the rotation of the crank, and the signal is waveform-shaped by the waveform shaping circuit 58 and sent to the CPU.
62. The CPU 62 detects the engine rotation speed from this signal. The accelerator opening sensor 66 detects the accelerator opening, and the cooling water temperature sensor 67 detects the temperature of the engine cooling water. Signals from the accelerator opening sensor 66 and the cooling water temperature sensor 67 are then taken into the CPU 62 via the A/D converter 59.

The signal from the nozzle lift sensor 46 for each cylinder is waveform-shaped by a waveform shaping circuit 56, as shown in FIG. 7, and then taken into the CPU 62. Then, the CPU 62 determines the injection start timing (valve opening timing) θi of the fuel injection valve 39 from the input of the cylinder discrimination signal to the rise of the pulse wave.
In addition, the period from the input of the cylinder discrimination signal to the fall of the pulse wave is detected as the injection end timing (valve closing timing) θie. However, the subscript i indicates the cylinder, and N is the number of engines.

Further, the CPU 62 drives and controls the piezo stack 34 of the spill valve 31 via the D/A converter 60 and the drive circuit 61.

Next, the operation for pilot injection in the fuel injection control device configured as described above will be explained using the flowcharts shown in FIGS. 5 and 6 and the time chart shown in FIG. 7.

The CPU 62 executes a control routine for the spill valve 31 shown in FIG. 5 at a predetermined timing. First, in step 100, the CPU 62 determines the accelerator opening degree α and the engine coolant temperature Tw.
and engine rotational speed NB are taken in to detect the operating state of the engine. Then, in step 101, the CPU 62 calculates the control amount of the spill valve 31 so that the nozzle needle 41 of the fuel injection valve 39 has a target opening period (target fuel injection amount) according to the operating state of the engine. That is, the valve opening timing θ from the input of the cylinder discrimination signal to the spill valve 31 is calculated (see FIG. 7).

Note that the target spill valve opening timing θ corresponding to the operating state of the engine is stored in the ROM 63 in advance.

Thereafter, in step 102, the CPU 62 multiplies the target spill valve opening timing θ by a correction coefficient Ki prepared for each cylinder to determine the target spill valve opening timing θ.
Calculate i. Then, in step 103, the CPU 62 controls the spill valve 31 for each cylinder based on θi.

On the other hand, the CPU 62 executes the correction processing routine shown in FIG. 6 at predetermined time intervals.

The CPU 62 determines that the engine speed NE is 7 in step 200.
It is determined whether or not the idle rotation region is below 0 Orpm. Then, if the CPU 62 is in the idle rotation region, the CPU 62 performs step 2.
At 01, the injection start timing (valve opening timing) θis and injection end timing (valve closing timing) θie of the fuel injection valve 39 based on the signal from the nozzle lift sensor 46 are taken in. C
In step 202, the PU62 determines the difference Δθi (=θie−θi) between the valve opening timing θis and the valve closing timing θie.
s) to calculate the actual opening period of the nozzle needle 41 of the fuel injection valve 39. Further, the CPU 62 determines the target spill valve opening timing θ obtained in step 102 in FIG.
A target opening period Ai of the nozzle needle 41 of the fuel injection valve 39 is calculated by multiplying i by a coefficient a.

Then, in step 203, the CPU 62 determines that the difference between Δθi and Ai (=Δθi − Ai) is within a predetermined range (±ε
) or not. The CPU 62 is (Δθi −Ai)
If it is smaller than -ε, step 204 adds a predetermined value β to the correction coefficient Ki to form a new correction coefficient Ki. Also, C
If (Δθi - Ai) is larger than +ε, the PU 62 subtracts a predetermined value β from the correction coefficient Ki in step 205 to obtain a new correction coefficient Ki. Further, if (Δθi - Ai) is within a predetermined range (±ε), the correction coefficient Ki is not corrected.

Thereafter, the flow shown in FIG. 5 is executed using this correction coefficient Ki.

The process shown in FIG. 6 is performed for each cylinder, and the correction coefficient Ki for each cylinder is corrected.

Therefore, as shown in FIG. 8, the fuel injection valve 39
When the biasing force of the pressure spring 43 decreases (deteriorates), the valve opening pressure of the nozzle needle 41 decreases. That is,
If the oil delivery characteristics from the fuel injection pump 50 do not change, the fuel injection valve 39 will open earlier and close later, and the amount of fuel injected will increase accordingly. However, a decrease in the biasing force of the pressure spring 43 of the fuel injection valve 39 is detected by the nozzle lift sensor 46, and the correction coefficient Ki is decreased, the target spill valve opening timing θi is accelerated, and the injection characteristics are returned to the initial setting state. can be maintained.

In this embodiment, the nozzle lift sensor 46 (valve body operation detection means) is configured to detect the operation of the nozzle needle 41 (valve body) of the fuel injection valve 39, and the microcomputer 55 (pilot injection control means and correction The control means) controls the spill valve 31 (pressure adjustment means) so that the nozzle needle 41 of the fuel injection valve 39 performs the target opening/closing operation.
The nozzle needle 41 of the fuel injection valve 39 is controlled by the nozzle lift sensor 46 during pilot injection in the idle rotation region.
Actual opening/closing operation (valve opening period Δθ of the nozzle needle 41
i) and the target opening/closing operation of the nozzle needle 41 of the fuel injection valve 39 (valve opening period Ai of the nozzle needle 41) (Δθi - Ai) by correcting the correction coefficient Ki. It was made to reflect in the control of 31. As a result, the biasing force of the pressure spring 43 of the fuel injection valve 39 may change over time, and the pressure of the pressure spring 43 of the injection valve 39 may change over time.
Even if the urging forces of 3 are different, optimum pilot injection amount characteristics can be ensured.

Note that this practice is not limited to the above examples,
Although the fuel injection pump used in the above embodiment is an injection pump of the cam type, a face cam type injection pump may be used. Also, Δθi and Ai at step 202 in FIG.
may be sampled multiple times and use the average value.

〔Effect of the invention〕

As detailed above, according to the present invention, an excellent effect of maintaining optimum pilot injection amount characteristics is exhibited.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to complaints, Fig. 2 is a sectional view of the inner cam type distribution type fuel injection pump of the embodiment, Fig. 3 is a sectional view of the fuel injection valve, and Fig. 4 is the electrical configuration of the fuel injection control device. 5 is a flowchart, FIG. 6 is a flowchart, FIG. 7 is a time chart, and FIG. 8 is a time chart. 31 is a spill valve as a pressure adjustment means, 39 is a fuel injection valve, 41 is a nozzle needle as a valve body, 43 is a pressure spring, 46 is a nozzle lift sensor as a valve body operation detection means, 50 is a fuel injection pump, 55 is a microcomputer as a pilot injection control means and a correction control means. Patent applicant Nippondenso Co., Ltd. Agent Patent attorney On 1) Hironobu (and 1 other person) M2
M1 (Shizuku Ishi Shun)

Claims (1)

[Claims] 1. A fuel injection valve includes a valve body biased in a valve closing direction by a spring, and the valve body opens and injects fuel when fuel pressure becomes greater than the biasing force of the spring; and a high pressure is applied to the fuel injection valve during a pressure feeding stroke. a fuel injection pump that supplies fuel; a pressure adjustment means for adjusting the pressure of high-pressure fuel to the fuel injection valve during the pressure feeding stroke of the fuel injection pump to cause the fuel injection valve to perform pilot injection; pilot injection control means for controlling the pressure adjusting means to perform pilot injection so that the valve body of the fuel injection valve performs a target opening/closing operation; and a valve body operation detection unit for detecting the operation of the valve body of the fuel injection valve. and a discrepancy between the actual opening/closing operation of the valve element of the fuel injection valve by the valve element operation detection means during pilot injection and the target opening/closing operation of the valve element of the fuel injection valve by the pilot injection control means. A fuel injection control device comprising: correction control means for causing the pilot injection control means to reflect this in the control of the pressure adjustment means from the next time onwards.