JPH0219629A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the startability of an engine by charging and discharging a piezoelectric element at least one time in advance of regular fuel injection at the time of engine starting. CONSTITUTION:When an intake stroke is judged at the time of engine starting, a piezoelectric control signal is outputted of two pulses from an electronic control unit 80. At the time of a startup of this first pulse, a piezoelectric element 46 is discharged, but fuel is not sprayed at all. At the time of falling of the first pulse, the piezoelectric element 46 is charged. Next, at the time of a startup of a second pulse, this element 46 is discharged, and the fuel is sprayed, but this sprayed fuel is a trace quantity, forming a premixed air-fuel ratio, and any ignition delay is kept back, thereby conducting to a good combustion. At the time of falling of the second pulse, the element 46 is recharged, whereby the terminal voltage becomes equalized to a terminal voltage in a stationary state, and regular injection is made executable, thus ordinary regular fuel injection is performed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection device for an internal combustion engine.

[Conventional technology]

In a fuel injection control device that controls fuel injection using a piezoelectric element, a drive control circuit that generates a drive control pulse for the piezoelectric element only during fuel injection is known (see Japanese Patent Laid-Open No. 60-237869). .

[Problem to be solved by the invention]

However, at the beginning of applying a drive control pulse to the piezoelectric element, sufficient electric charge is not charged or discharged to the piezoelectric element, and as a result, the piezoelectric element does not expand or contract sufficiently. Therefore, even if a drive control pulse is applied to the piezoelectric element to inject fuel when starting the engine, the piezoelectric element does not expand or contract sufficiently, so only a small amount of fuel is injected, making it difficult to start the engine. There's a problem.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, high-pressure fuel is constantly supplied to the fuel injection valve during engine operation, and the injection of the high-pressure fuel from the fuel injection valve is controlled by the charging and discharging action of a piezoelectric element. In the injection device, the piezoelectric element is charged and discharged at least once when starting the engine and prior to regular fuel injection.

[For production]

According to the present invention, with the above-described configuration, the piezoelectric element is charged and discharged at least -.times. prior to regular fuel injection when starting the engine. Therefore, since the piezoelectric element charging/discharging potential difference can be made large from the time of the first injection, a sufficient amount of displacement of the piezoelectric element can be obtained, and the startability of the engine is improved.

〔Example〕

Referring to Figures 2 and 3, 1 is the diesel engine body, 2 is the cylinder block, 3 is the cylinder head, and 4 is the cylinder block.
is a piston, 5 is a combustion chamber, 6 is an intake valve, 7 is an exhaust valve, 8
1 represents a fuel injection I/1 valve disposed within the combustion chamber 5, and 9 represents an intake manifold, and an intake portion of the intake manifold 9 is connected to a supercharger.

The fuel injection valve 8 is connected to a fuel accumulator pipe 11 common to each cylinder via a fuel supply pipe IO. The fuel accumulator pipe 11 has a pressure accumulator chamber 12 with a constant volume inside thereof, and the fuel in the pressure accumulator chamber 12 is supplied to the fuel injection valve 8 via the fuel supply pipe 10. On the other hand, the pressure accumulation chamber 12 is connected to the discharge [1] of a fuel supply pump 14 whose discharge pressure can be controlled via a fuel supply pipe 1;3. The suction port of the fuel supply pump 14 is connected to the discharge port of a fuel pump 15, and the suction port of the fuel pump 15 is connected to a fuel tank 16. Further, each fuel injection valve 8 is connected to the fuel reservoir tank 1 via a fuel return conduit 17.
6. The fuel pump 15 is provided to feed the fuel in the fuel reservoir tank 16 into the fuel supply pump 14, and if the fuel can be sucked into the fuel supply pump 14 without the fuel pump 15, the fuel There is no particular need to provide the pump 15. On the other hand, the fuel supply pump 14 is provided to discharge high-pressure fuel, and the high-pressure fuel discharged from the fuel supply pump 14 is accumulated in the pressure accumulation chamber 12.

A pair of disks 72 and 73 are attached to the engine crankshaft, and a crank reference position sensor 67 and a crank angle sensor 66 are arranged opposite the toothed outer circular surfaces of these disks 72 and 73. Crank reference position sensor 67
For example, the crank reference position sensor 67 generates an output pulse indicating that the No. 1 cylinder is at the intake top dead center.
It is possible to determine which cylinder's fuel injection valve 8 is to be operated from the output pulse. Crank angle sensor 6
6 generates an output pulse every time the crank shirt I. rotates by a certain angle, and therefore the engine speed can be calculated from the output pulse of the crank angle sensor 66.

A drive control circuit 82 controls the fuel injection valve 8 based on signals from the crank angle sensor 66, crank reference position sensor 67, starter switch 68, and ignition switch 71.

FIG. 4 shows a side sectional view of the fuel injection valve 8. Referring to FIG. 4, 20 indicates a nozzle body having an injection hole 21 at its tip, and a needle 22 is inserted into the nozzle body 20 so that the injection hole 21 can be opened and closed.

The nozzle body 20 is fitted into the body 23, and the fuel is supplied through a fuel passage 26 equipped with a fuel inlet 24 and a sealing plug 25.
, the fuel is injected from the injection hole 21 via the fuel passage 27, the fuel reservoir chamber 28, and the storage chamber 29.

Fuel injection control by opening and closing the needle 22 is directly controlled by the sea! - Held in section 30. A tapered pressure receiving surface 31 is formed on the needle 22, and when the pressure receiving surface 31 receives fuel pressure, the needle 22 moves in the valve opening direction.

A fuel reservoir chamber 28 is formed around this pressure receiving surface 31. The storage chamber 29 is formed between the fuel reservoir chamber 28 and the injection hole 21, and extends in a long and narrow manner to the vicinity of the injection hole 21. The passage cross-sectional area of this storage chamber 29 is formed to be larger than the cross-sectional area of the fuel passage 27 leading to the fuel reservoir chamber 28. Further, the cross-sectional area of the storage chamber 29 is preferably at least 10 times the total area of the injection holes 21, and the volume of the storage chamber 29 is preferably 0.5 cc or more.

The upper end of the needle 22 is connected to the body 23 via a distance piece 32 and a knock pin 33, and a compression spring 34 is interposed in this portion. The nozzle body 20 is connected to the body 23 by a retaining nut 35. A slight clearance 36 is formed between the upper part of the needle 22 and the inner circumference of the nozzle body 20, and through the clearance 36, fuel flows from the fuel reservoir chamber 28 to a pressure chamber 37 formed upward. It is supposed to be filled.

The pressure chamber 37 is formed between the lower end of the piston 38 and the upper end of the body 23, and the fuel pressure in the pressure chamber 37 can act as a force in the opening/closing direction of the needle 22. The piston 38 is slidably inserted into the case 39 and is biased in the -F direction by a disc spring 4o. Case 3
9 is positioned by the knock bottle 4■, and the pressure chamber 37
is sealed by an O-ring 42 and a puncture amplifier ring 43 provided on the outer periphery of the screw 1-ring 38. The case 39 is fixed to the body 23 via a nut 44.

Electronic actuator 4 that can be expanded and contracted inside the case 39
5 is provided. 46 is a piezoelectric element, and ceramic plates 1-47.48 and metal plates 1-49.50 are provided on both sides thereof. 51 indicates an adjustment shim. The electrostrictive actuator 45 has a lead wire 52
Expansion and contraction are controlled by a drive control circuit 82 connected via.

The fuel inlet 24 is connected to the fuel supply conduit ■0.

In the fuel injection valve configured as described above, the supplied fuel is supplied through the fuel inlet 24, the fuel passage 2G,
27 to the fuel storage chamber 28, and further via the clearance 36 to the pressure chamber 37 and the fuel storage chamber 29 on the injection hole side.
is filled with. When the piezoelectric element 46 contracts, the fuel pressure received by the pressure receiving surface 31 lifts the needle 22 to open the valve, and fuel is injected from the injection hole 21. When the piezoelectric element 4G extends, the pressure in the pressure chamber 37 increases, and the needle 22 is pushed downward through this pressure to close the valve, and the injection ends.

The drive control circuit 82 shown in FIG. 1 is composed of an electronic control unit 80 and a drive circuit 81 (14).

The drive circuit 81 includes a power source 57, a nyristor 53, a charging side coil 54, a discharging side coil 55, and a nyristor 56.
and. One terminal of the piezoelectric element 46 is connected to a negative terminal of a power source 57. Piezoelectric element 4
The other terminal of G is connected to the positive terminal of the power source 57 via the charging coil 54 and thyristor 53 on the one hand, and to the negative terminal of the power source 57 via the discharging coil 55 and thyristor 56 on the other hand. . A number of drive circuits similar to the drive circuit 81 are provided corresponding to the number of fuel injection valves 8, but only one is representatively shown in FIG. Similarly, one each of drive circuits 69 and 70 is shown as a representative.

On the other hand, the electronic control unit 80 is composed of a digital computer, and includes a ROM (read only memory) 61, a RAM (random access memory) 62, a CI (microprocessor) 63, and an input port controller that are interconnected by a bidirectional bus 6o. 4 and an output port 5. The output pulses of the crank angle sensor 66 and the crank reference position sensor 67 are input to the manual port 4.

Further, a starter switch 68 is connected to the input port 4. On the other hand, the output port 5 has a corresponding drive circuit 69
, 70 to the gate terminals of each of the cyrisks 53, 56. Further, the electronic control unit 1-80 is connected to the ignition switch 71, and power is supplied to the electronic control unit 80 when the ignition switch 71 is turned on.

FIG. 5 shows a time chart of the drive control of the piezoelectric element 46 after a while after the drive control of the piezoelectric element 46 is started. At the rising edge of the control signal of the electronic control unit 80, a trigger pulse is applied to the gate of the Cyrisk 56, turning the Nylister 56 on. When the thyristor 56 is turned on, the electric charge charged in the piezoelectric element 46 is discharged via the discharging coil 55 and the thyristor 56, and thus the piezoelectric element 4
6 terminal voltage decreases. At this time, the terminal voltage of the piezoelectric element 46 becomes 0 (V) or less due to the oscillation circuit consisting of the discharge coil 55 and the piezoelectric element 46. As a result, the piezoelectric element 46 contracts and the pressure inside the pressure chamber 37 decreases, so that the fuel pressure received by the pressure receiving surface 31 lifts the twenty-one dollar 22 and starts fuel injection.

Next, when the control signal of the electronic control unit 80 falls,
A trigger pulse is given to the gate I of the thyristor 53,
(The Noiristor 53 turns on. When the thyristor 53 turns on, the power supply 57 connects the thyristor and the charging coil 5.
4, the piezoelectric element 46 is gradually charged with electric charge, and the terminal voltage of the piezoelectric element 46 gradually increases accordingly. At this time, the terminal voltage of the piezoelectric element 32 is applied to the power supply 52 by an oscillation circuit consisting of a charging coil 54 and the piezoelectric element 32 (which can be regarded as a capacitor).
becomes higher than the voltage E of . Next, when a reverse voltage is applied to the thyristor 53, the thyristor 53 is turned off.

As a result, the piezoelectric element 46 expands and the pressure in the pressure chamber 37 increases, which pushes the needle 22 downward and stops fuel injection.

When the electric charge charged in the piezoelectric element 46 is discharged, fuel injection is started, and when the electric charge is charged, the fuel injection is stopped, so the fuel injection is started at the rising edge of the control signal of the electronically controlled Uniso I-80, Fuel injection will stop at the time of falling.

FIG. 5 shows the state some time after the drive control of the piezoelectric element 46 was started as described above, and at this time the piezoelectric element 46 is charged with a sufficient amount of electric charge. However, immediately after starting drive control of the piezoelectric element 46, the amount of charge charged and discharged to the piezoelectric element 46 is small, and therefore the amount of expansion and contraction of the piezoelectric element 46 becomes small. Next, this will be explained with reference to FIG.

FIG. 6 shows the terminal voltage of the piezoelectric element 46,
As shown in FIG. 6, before the drive control of the piezoelectric element 46 is started, the terminal voltage of the piezoelectric element 46 is 0.
(V). Incidentally, the amount of charge that can be charged to the piezoelectric element 46 is proportional to the difference ΔV between the voltage E of the power source 57 and the terminal voltage of the piezoelectric element 46. Therefore, t,
Then, an amount of charge proportional to ΔV is charged. On the other hand, the amount of charge that can be discharged from the piezoelectric element 46 is proportional to the terminal voltage Δ■2 of the piezoelectric element 46. Therefore, at t2, an amount of charge proportional to ΔV2 is discharged, and as a result, the terminal voltage of the piezoelectric element 46 is 0 (V).
The following is true. Next, in (3), the amount of charge proportional to Δv3 is charged, so the amount of charged charge increases, and the terminal voltage Δ■4 of the piezoelectric element 4G increases.Next, in L4, the amount of charge proportional to Δv3 increases. As the piezoelectric element 46 is repeatedly charged and discharged, the amount of charge discharged increases, and the terminal voltage of the piezoelectric element 46 further decreases.As shown in FIG. It increases and finally settles down to a constant value. This time is shown in FIG. 5. Therefore, when the drive control of the piezoelectric element 46 is started, the amount of charge charged and discharged to the piezoelectric element 46 is small. In this case, the amount of expansion and contraction of the piezoelectric element 46 is small (therefore, only a small amount of fuel can be injected. Therefore, even if the piezoelectric element 46 is driven to inject fuel at the time of starting the engine, only a small amount of fuel is injected. The desired amount of fuel can be injected after the piezoelectric element 46 is driven several times to charge a sufficient amount of electric charge to the piezoelectric element 46. Therefore, it takes time to start the engine. Therefore, in the present invention, when starting the engine, the piezoelectric element 46 is charged and discharged at least once before the regular fuel injection, and when the regular fuel injection should be performed, the piezoelectric element 46 is charged and discharged at least once. The element 46 is allowed to charge and discharge a sufficient amount of charge, thereby making it easier to start the engine.

Next, referring to FIG. 7, a piezoelectric element 46 according to the present invention
A first embodiment of the drive control method will be described.

Referring to FIG. 7, when starting the engine, the ignition switch 71 is turned on, and then the starter switch 68 is turned on. After the starter switch 68 is turned on, if it is determined that it is the intake stroke of the first cylinder, for example, the electronic control unit 80 outputs two pulses of the piezoelectric element control signal of the first cylinder. As a result, the piezoelectric element 46 is dummy driven.

A control signal for dummy driving the piezoelectric element 46 (
The width of one pulse of the first dummy pulse (hereinafter referred to as "dummy pulse") is shorter than the width of one pulse of the signal that controls regular fuel injection in the normal operating state (for example, set to o, tma. At the rising edge of the pulse ■, the piezoelectric element 46 of the first cylinder is discharged.However, at this time, since the piezoelectric element 4G is not originally charged, the terminal voltage of the piezoelectric element remains O■. Therefore, no fuel is injected. At the falling edge of the first dummy pulse, the piezoelectric element 46 of the first cylinder is charged. At this time, the terminal voltage of the piezoelectric element 46 is v.
It is l. Next, at the rising edge of the second dummy pulse, the piezoelectric element 46 is discharged.

At this time, fuel is injected, and the fuel injection time is Q, l
Since the time is very short (ms), the amount of fuel injected is very small. This injected fuel forms a premixture, which prevents ignition delay and contributes to good combustion. At the falling edge of the second dummy pulse (3), the piezoelectric element 46 is charged again. The terminal voltage (2) of the piezoelectric element 46 at this time is approximately equal to the terminal voltage V of the piezoelectric element 46 in a steady state, and it is possible to carry out regular injection for rotationally driving the engine without any trouble. state. At the timing (3) when regular fuel injection is to be performed, regular fuel injection is performed. Thereafter, regular fuel injection is performed at every timing when regular fuel injection is to be performed, thereby rotationally driving the engine. Similarly, in other cylinders, when starting,
Prior to regular fuel injection, each piezoelectric element 46 is dummy driven during the intake stroke of each cylinder.

As described above, according to this embodiment, the piezoelectric element 46 is charged and discharged prior to regular fuel injection, and a sufficient amount of charge can be charged and discharged to the piezoelectric element 46 when regular fuel injection should be performed. , a desired amount of fuel can be injected from the beginning of regular fuel injection, thus ensuring a good engine start.

A routine for executing the above embodiment is shown in FIG.

This routine is executed by an interrupt at every fixed crank angle. When the ignition switch 71 is turned on, the flag FX is set to 0, the counter C is set to 8,
This routine is activated when starter switch 68 is turned on.

First, in step 90, it is determined whether the counter C is not 0 or not. At the initial stage of startup, since C=8, an affirmative determination is made and the process proceeds to step 91. In step 91, it is determined whether the X-th cylinder whose crank angle is between the suction bottom dead center and the compression top dead center is at the first dummy drive timing. For example, if the crank angle of the first cylinder is between the suction bottom dead center and the compression top dead center, x-1 is established, and it is determined whether the first cylinder is at the first dummy drive timing. If an affirmative determination is made, the dummy drive time TD is set to 0.1 ms in step 110, and then step 9
2, the piezoelectric element 46 of the first cylinder is dummy driven. In step 93, the flag FX Zunawara flag F
1 is set to 1.

In step 94, C is decremented by 1, and in this case, for example, C=7. If a negative determination is made in step 91, it is determined in step 95 whether Fx=1.

For example, in this case, since x=1, it is determined whether it is Fl-1 or not. In the case of FINl, since the first dummy drive has not been executed, this routine ends without executing anything. If F1=1, the process proceeds to step 96, where it is determined whether or not it is the first cylinder second dummy drive timing. That is, flag F
Depending on whether x = 1 or not, if dummy driving is to be performed, the first dummy driving is always performed. If an affirmative determination is made in step 96, the dummy drive time T D is set to O, l ms in step Lit, and then in step 7 block 97, the second dummy drive is executed. After this, in step 94, C is further reduced by 1, for example to 6 in this case. After executing the first and second dummy drives, it is determined in step 98 whether or not it is the first cylinder normal injection timing. If the determination is affirmative, normal injection is executed in step 99. The injection time and injection time of regular injection are calculated by another routine not shown. If the determination is negative, this routine ends without executing anything.

Next, when the compression top dead center of the first cylinder is passed, X is set to 3, and the same process is executed for the third cylinder.

Thereafter, X is sequentially set to 4 and 2 in the same way, and similar processing is executed. The counter C is decremented by 1 every time the dummy drive is performed, and becomes C-0 when the dummy drive is executed twice for all cylinders. After reaching C-0, dummy drive is not executed, only regular injection is executed, and normal engine operation is performed.

Next, the second embodiment will be explained with reference to FIG.

Referring to FIG. 9, when the ignition switch 71 is turned on (at time Lb when lQOms have elapsed from 5), the first dummy drive is executed simultaneously on all cylinders, and further from t6 to 1QOms.
The second dummy drive is executed at time t7 when 0+ms has elapsed. Thereafter, the starter switch 68 is turned on to start the engine, and regular injection 1 is executed at each regular injection timing for each cylinder.

According to this embodiment, as in the first embodiment, a desired amount of fuel can be injected from the beginning of regular injection, and a good engine start can be ensured.

Furthermore, in this embodiment, since the piezoelectric element 46 is dummy-driven before the engine is started, the pressure accumulator 12 (second
There is no pressure on the fuel inside (see figure). Therefore, there is no fear that fuel will be injected by the dummy drive.

FIG. 10 shows a routine for executing the second embodiment. This routine is activated only when the engine is started.

First, in step lOO, it is determined whether or not the ignition switch 71 is on. Only when it is determined that 1 is constant, the process proceeds to step 101 and the dummy drive time '1'' I) is set to 0.11113. In step 102, the timer is started. In step 103, the timer count value '1'' is set to 0.11113.
It is determined whether I"l is 100m5 or more. [Only when it is determined that r is constant, the process proceeds to step 104, and the first dummy drive is executed. In step 105, another timer is driven, and in step 106, this timer is timer) J runt value T
It is determined whether or not 2 is greater than or equal to lQms. If the determination is affirmative, the second dummy drive is executed in step 107, and this routine ends. Thereafter, after the starter engine 8 is turned on, normal injection is executed by another routine.

〔Effect of the invention〕

According to the present invention, the piezoelectric element is charged and discharged prior to regular fuel injection. As a result, when regular fuel injection should be performed, the piezoelectric element can be charged and discharged with an additional amount of electric charge, so that the desired amount of fuel can be injected from the beginning of regular fuel injection, thus ensuring a good engine performance. It is possible to ensure the start of the engine.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the piezoelectric element drive control circuit, Figure 2
The figure is a plan view schematically showing a four-cylinder diesel engine, Figure 3 is a side sectional view of the diesel engine, Figure 4 is a side sectional view of the fuel injection valve, and Figure 5 is drive control of the piezoelectric element. Fig. 6 is a time chart showing the terminal voltage of the piezoelectric element when drive control of the piezoelectric element is started, and Fig. 7 is a time chart of the drive control after a while has elapsed since the start of the drive control. A time chart of the drive control of the piezoelectric element according to the embodiment, FIG. 8 is a flowchart 1 for executing the first embodiment, and FIG. 9 is a time chart of the drive control of the piezoelectric element according to the second embodiment. Chart, No. 10
The figure shows a flowchart 1- for implementing the second embodiment. 8...Fuel injection valve, 46...Piezoelectric element, 8
2... Drive control circuit.

Claims (1)

[Claims] High-pressure fuel is constantly supplied to the fuel injection valve during engine operation,
In the fuel injection device in which the injection of the high-pressure fuel from the fuel injection valve is controlled by the charging and discharging action of a piezoelectric element, the piezoelectric element is charged and discharged at least once before regular fuel injection when starting the engine. Fuel injection system for internal combustion engines.