JP2765207B2 - Fuel injection rate control device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection rate control device for a diesel engine using a piezoelectric actuator, and more particularly, to a variable volume chamber that communicates with a fuel injection pump and a pressurization chamber. The present invention relates to a fuel injection rate control device in which pilot injection is performed by adjusting the fuel injection rate by increasing or decreasing the volume of a variable volume chamber with a piezoelectric actuator.

[Prior art] Conventionally, during fuel injection of a diesel engine,
It is known that noise and harmful exhaust gas generated in a diesel engine can be reduced by performing pilot injection, which is a preliminary injection prior to the main injection.
There is a fuel injection rate control device using a piezoelectric actuator to perform the pilot injection. In this type of control device, the voltage generated by the piezoelectric actuator corresponds to the phase of the pumping stroke of the fuel injection pump, that is, the piezoelectric actuator contracts and the generated voltage increases as the pumping stroke progresses. When the generated voltage reaches a predetermined reference voltage, a high voltage is applied to the piezoelectric actuator to expand the piezoelectric actuator and perform pilot injection.

However, since the reference voltage is always constant in the control device, it is not possible to compensate for the change in the viscosity of the fuel, and the following problem occurs. That is, when the temperature of the fuel increases, the viscosity of the fuel decreases, so that the amount of leakage of the fuel increases, and the pressure applied to the piezoelectric actuator decreases. As a result, a high voltage cannot be applied to the piezoelectric actuator at an optimal timing.

Therefore, the present applicant has previously proposed a fuel injection rate control device provided with fuel temperature detecting means for detecting the temperature of fuel and reference voltage lowering means for lowering the reference voltage as the fuel temperature rises. (Japanese Patent Application No. 1-333737). In this device, the reference voltage lowering means lowers the reference voltage as the fuel temperature detected by the fuel temperature detecting means increases. Therefore, a decrease in the pressure of the piezoelectric actuator due to an increase in the fuel temperature can be compensated for by a decrease in the reference voltage, and the pilot injection can be executed at a stable timing.

[Problems to be Solved by the Invention] However, in the prior art, although the temperature change of the fuel can be compensated as described above, the variation in the piezoelectric characteristics of the piezoelectric actuator between products and the fuel properties such as the type of light oil are also considered. Are not taken into account and cannot be compensated for. In particular, when a fuel having a low viscosity is used, there is a problem that it takes time to increase the pressure in the pressurizing chamber and the timing of pilot injection is delayed.

FIG. 9 shows the relationship between the piezoelectric element voltage V and the reference voltage Vth. In the figure, α is the target characteristic of the piezoelectric element voltage, and β is the characteristic of the piezoelectric element voltage when a low-viscosity fuel is used. From this figure, it can be seen that in the characteristic α, the piezoelectric element voltage V reaches the reference voltage Vth at the time ta, whereas in the characteristic β, the time ta
At time T later by ΔT, the piezoelectric element voltage V reaches the reference voltage Vth. Therefore, in the characteristic β, the optimal timing t
In a, no voltage is applied to the piezoelectric element.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and its purpose is to compensate for variations in the piezoelectric characteristics of a piezoelectric actuator between products and changes in fuel properties, and to always drive a piezoelectric actuator at an optimal timing. Accordingly, an object of the present invention is to provide a fuel injection rate control device for a diesel engine that can perform pilot injection with stable execution timing.

Means for Solving the Problems The present invention relates to a fuel provided with a fuel injection pump of a type in which a variable volume chamber communicates with a pressurizing chamber during pilot injection and the variable volume chamber is shut off from the pressurizing chamber during main injection. In the injection rate control apparatus, attention is paid to the fact that the voltage generated by the piezoelectric actuator is substantially constant for a predetermined period during the main injection in which the pressure in the variable volume chamber is not affected by the pressurized chamber.

Therefore, in order to achieve the above object, as shown in FIG. 1, according to the present invention, a pressurizing device that draws fuel and pressurizes fuel by reciprocating a plunger inserted in a cylinder with driving of a diesel engine M1. A fuel injection pump M2 having a chamber and a variable volume chamber communicated with the pressurizing chamber during pilot injection prior to main injection in the process of reciprocating the plunger, and shut off during main injection; A piezoelectric actuator M3 that generates a voltage corresponding to the pressure of the fuel cell, expands by applying the voltage, boosts the fuel in the variable volume chamber to perform pilot injection by the fuel injection valve, and pressurizes the fuel injection pump M2. When the voltage generated by the piezoelectric actuator M3 due to the pressure increase in the variable volume chamber when the chamber communicates with the variable volume chamber reaches the reference voltage, the voltage is applied to the piezoelectric actuator M3. And a reference voltage used in the pilot injection timing control means M4 based on a constant voltage generated in the piezoelectric actuator M3 during the main injection. Is provided with a reference voltage correcting means M5 for correcting.

[Operation] According to the present invention, as shown in FIG.
When the plunger of the fuel injection pump M2 reciprocates with the driving of M1, the fuel is sucked and pressurized in the pressurizing chamber. When the variable volume chamber communicates with the pressure chamber in the process of increasing the pressure of the fuel in the pressure chamber, the fuel in the variable volume chamber is also pressurized. At this time, the piezoelectric actuator M3 generates a voltage according to the pressure in the variable volume chamber. When the generated voltage reaches the reference voltage, pilot injection timing control means M4 applies a voltage to piezoelectric actuator M3. Due to the application of this voltage, the piezoelectric actuator M3 expands, pressurizes the fuel in the variable volume chamber, and performs pilot injection by the injection valve.

Further, in the process of pressurizing the fuel in the pressurized chamber, if the variable volume chamber is shut off from the pressurized chamber after the pilot injection is performed, the main injection is performed by the injection valve. During this main injection, the pressure in the variable volume chamber is not affected by the pressurizing chamber, and the voltage generated by the piezoelectric actuator is substantially constant. Based on the voltage generated by the piezoelectric actuator M3 during the main injection, the reference voltage correction means M5 corrects the reference voltage used for the pilot injection timing control means M4.

Therefore, even if the piezoelectric characteristics of the piezoelectric actuator M3 vary between products or the characteristics of the piezoelectric element voltage fluctuate from the target characteristics due to fuel properties such as the type of fuel, the reference voltage for pilot injection is corrected, Piezo actuator
M3 is always driven at the optimal timing. Particularly, in the above configuration, the variable volume chamber is isolated from the pressurizing chamber during the main injection, so that the pressure fluctuation in the pressurizing chamber is not propagated to the variable volume chamber. Therefore, even if the pressure in the pressurizing chamber fluctuates due to the reciprocating operation of the plunger or the variation in the valve opening state of the fuel injection valve, the pressure in the variable volume chamber does not affect the pressure fluctuation. I will not receive it. As a result, the voltage generated by the piezoelectric actuator M3 does not fluctuate irrespective of the piezoelectric characteristics and the fuel properties, and more accurate correction of the reference voltage is performed in this regard.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a schematic configuration of a fuel injection rate control device 1 for a diesel engine 2. The fuel injection rate control device 1 is a distribution type fuel injection device that pressurizes and supplies fuel supplied to the diesel engine 2. A pump 3, a piezoelectric actuator 4 attached to the fuel injection pump 3, a drive circuit 5 for driving the piezoelectric actuator 4, a high-voltage power supply 6, and pilot injection timing control means for controlling these and reference voltage correction means. (Hereinafter simply referred to as ECU) 7.

A combustion chamber 8 of the diesel engine 2 is formed by a cylinder 9, a piston 10, and a cylinder head 11, and a fuel injection valve 12 is disposed in the combustion chamber 8. A water temperature sensor 13 for detecting a cooling water temperature Thw of the diesel engine 2 is attached to the cylinder 9.

Also, the rear part of the fuel injection pump 3 (the left part in FIG. 2).
A fuel feed pump 16, a pulse gear 17, and a coupling 18 are connected to a drive shaft 15 that is inserted and supported. When the driving force of the diesel engine 2 is transmitted to the drive shaft 15 via the drive pulley 19, the fuel feed pump 16 and the like
It is designed to rotate together with 15.

On the other hand, a block 20 is attached to the front part (the right part in FIG. 2) of the fuel injection pump 3, and a cylinder 21 is fixed on the block 20 on the same axis as the drive shaft 15. A plunger 23 is slidably inserted into the cylinder 21, and a space surrounded by the block 20, the plunger 23, and the cylinder 21 is a pressurizing chamber 24 for sucking and increasing the pressure of fuel.

The plunger 23 is connected to the coupling 18 at the front end of the drive shaft 15 so as to be integrally rotatable and to be able to reciprocate in the front-rear direction. That is, the drive shaft
A roller ring 25 is integrally rotatably connected to a front end of the cam 15, and a plurality of cam rollers 26 are rotatably mounted on an outer peripheral portion of the roller ring 25. On the other hand, a cam plate 27 having a cam face is connected to the rear end of the plunger 23, and the plunger 23 and the cam plate 27
Urged rearward. Therefore, the rotation of the drive shaft 15 causes the plunger 23 to reciprocate in the front-rear direction while rotating, thereby distributing and pumping the fuel.

A rotation speed sensor 29 is disposed near the outer periphery of the pulse gear 17, and the rotation speed sensor 29 detects the engine rotation speed Ne of the diesel engine 2 from the rotation speed of the drive shaft 15.

FIG. 3 is an enlarged sectional view showing the plunger 23 and the cylinder 21.
As many intake ports 30 as the number of cylinders of diesel engine 2
Are formed. Center port at the axis of plunger 23
A front end of the central port 31 is connected to the pressurizing chamber 24.
It is open to. An annular groove 32 is formed in the outer periphery of the plunger 23 near the rear of the suction port 30, and the annular groove 32 is formed.
Is connected to the central port 31 through a port 33.

Further, on the outer periphery of the plunger 23, at the rear position of the annular groove 32, the same number of distribution ports 34 as the number of cylinders of the diesel engine 2 are recessed.
Is in communication with Further, as shown in FIG. 2, a spill port 35 extends radially outward from the rear end of the central port 31 in the plunger 23, and the spill port 35 opens to the outer peripheral surface of the plunger 23. ing. The spill port 35 is for overflowing the surplus of the fuel pressurized in the pressurizing chamber 24.

On the other hand, the block 20 is formed with a suction passage 37 that communicates between the low-pressure chamber 36 in the fuel injection pump 3 and the inner surface of the cylinder 21 and communicates the fuel injection valve 12 of the diesel engine 2 with the inner surface of the cylinder 21. The same number of distribution passages 38 as the number of cylinders of the diesel engine 2 are provided.
A delivery valve 39 is provided in the middle of each of 38.

The piezoelectric actuator 4 includes a casing 40 screwed to a lower portion of the block 20, a piston 41 slidably fitted in a space in the casing 40 in a vertical direction, and an upper half part inserted into the piston 41. A piezoelectric element 42 whose lower end is fixed to the inner bottom surface of the casing 40, and a signal line 43 which is a conduction path of electric charges generated by the piezoelectric element 42 or electrification supplied to the piezoelectric element 42. . The space surrounded by the casing 40, the piston 41 and the block 20 is a variable volume chamber 44. This variable volume chamber 44
Communicates with the inner surface of the cylinder 21 through a communication hole 45 formed in the block 20.

The piezoelectric element 42 is formed by laminating a plurality of disk-shaped members made of PZT (lead zirconate titanate). Then, when charges are supplied via the signal line 43,
Since the piezoelectric element 42 expands and slides the piston 41 upward, the volume of the variable volume chamber 44 decreases. Conversely, when electric charges are discharged via the signal line 43, the piezoelectric element 42 contracts and slides the piston 41 downward, so that the volume of the variable volume chamber 44 increases. When a compressive force acts on the piezoelectric element 42 in accordance with an increase in the fuel pressure inside the variable volume chamber 44, the piezoelectric element 42 discharges an electric charge to the signal line 43 in an amount corresponding to the strain caused by the compressive force.

In the fuel injection pump 3 configured as described above, with the rotation of the drive shaft 15, the fuel feed pump 16,
When the cam plate 27 and the plunger 23 rotate and the cam plate 27 gets off the cam roller 26 of the roller ring 25, the plunger 23 moves rearward to perform a fuel suction stroke. In this suction stroke, as shown in FIG.
30 communicates with the suction passage 37, but the distribution port 34 is
Cut off from 38.

Conversely, when the cam plate 27 rides on the cam roller 26 of the roller ring 25, the plunger 23 moves forward to perform a fuel compression stroke and perform pilot injection and main injection. At the time of pilot injection, as shown in FIG. 5, the suction port 30 is shut off from the suction passage 37, but the annular groove 32 communicates with the communication hole 45, and the distribution port 34 communicates with the distribution passage 38.
Further, at the end of the pilot injection, although not shown, the suction port 30 is cut off from the suction passage 37, the annular groove 32 is cut off from the communication hole 45, and the distribution port 34 is cut off from the distribution passage 38. Further, at the time of the main injection, as shown in FIG. 3, the suction port 30 is cut off from the suction passage 37 and the annular groove 32 is cut off from the communication hole 45, respectively, but the distribution port 34 communicates with the distribution passage 38.

As shown in FIG. 2, a driving circuit 5 for driving the piezoelectric actuator 4 includes a capacitor 46 connected in parallel to a high-voltage power supply 6, and the capacitor 46 and the piezoelectric actuator 4.
And a discharging thyristor 49 and a discharging coil 50 connected in parallel to the piezoelectric actuator 4, and a rectangular which is a drive circuit control signal output from the ECU 7. A trigger pulse is output to the energizing thyristor 47 when the signal rises,
When the rectangular signal falls, the discharging thyristor 49
And a trigger generator 51 that outputs a trigger pulse.

The drive circuit 5 temporarily stores the high voltage generated by the high voltage power supply 6 in the capacitor 46, and when the energizing thyristor 47 is turned on at the time of the rise of the rectangular signal from the ECU 7, the electric charge stored in the capacitor 46 is stored in the piezoelectric actuator. When the discharging thyristor 49 becomes conductive at the time of the falling of the rectangular signal from the ECU 7, the electric charge stored in the piezoelectric actuator 4 is discharged.

Incidentally, the fuel injection rate control device 1 of the diesel engine 2 is provided as a detector in addition to the rotation speed sensor 29 and the water temperature sensor 13 as well as an accelerator sensor 52 for detecting an opening degree of an accelerator pedal and a crankshaft. And a crank angle sensor 53 disposed close to the signal disc plate.

The ESU 7 is configured as a logical operation circuit mainly including a CPU 54, a ROM 55, a RAM 56, and a timer 57, and these are configured as a common bus 58.
Is connected to the input / output unit 59 via the. Detection signals of the rotation speed sensor 29, the water temperature sensor 13, and the accelerator sensor 52,
And the piezoelectric element voltage of the piezoelectric element 42 is CP via the input / output unit 59.
The CPU 54 outputs a control signal to the drive circuit 5 and the high-voltage power supply 6 via the input / output unit 59. Also,
The ROM 55 stores a reference voltage Vmo of the piezoelectric element 42 at the time of the main injection of the fuel injection pump 3. Note that power is supplied to the drive circuit 5 and the ECU 7 from the vehicle-mounted battery 60 via an ignition switch 61.

Next, the processing executed by the ECU 7 will be described based on the flowcharts shown in FIGS.

The injection amount calculation process shown in FIG. 6 is repeatedly executed at predetermined time intervals when the diesel engine 2 is started. First, in step 100, the engine rotation speed Ne, the accelerator opening Accp, and the cooling water temperature Thw are read from the detection results of the rotation speed sensor 29, the accelerator sensor 52, and the water temperature sensor 13.
In the following steps 110 to 150, various values relating to the pilot injection, that is, the control reference voltage Vth, the application time T1, the short time T2, the fall time T3, and the dwell time TDUEL (see FIG. 8) are calculated.

More specifically, the control reference voltage Vth is a piezoelectric element voltage when a high voltage is applied to the piezoelectric actuator 4 in order to execute the pilot injection, and the engine rotation speed Nth
e, the accelerator opening Accp and the cooling water temperature Thw are defined as variables. Therefore, in step 110, the engine speed Ne and the accelerator opening read in step 100 are read using the three-dimensional map stored in the ROM 55 in advance.
The control reference voltage Vth is calculated based on the Accp and the cooling water temperature Thw.

In addition, application time T1, short time T2 and fall time
T3 is various values that determine the pilot injection rate, dwell time TDUEL is the power storage time in the capacitor 46 for pilot injection, and these values are defined using the engine speed Ne as a variable. For this reason, in steps 120 to 150, the one-dimensional map stored in the ROM 55 in advance is used, and the application time T1 and the short time
Calculate T2, fall time T3, and dwell time TDUEL, respectively.

After execution of step 150, the process proceeds to step 160, where the voltage Vm generated at the piezoelectric element 42 at the time of the main injection is read. In the following step 170, the generated voltage Vm read in step 160 is
By dividing by the reference voltage Vmo stored in advance in M55, the correction coefficient K
(= Vm / Vmo) is calculated. Thereafter, the process proceeds to step 180, where a new control reference voltage Vth ^* is calculated by multiplying the control reference voltage Vth calculated in step 110 by the correction coefficient K. After execution of step 180, the process exits to "NEXT" and ends this processing. Thereafter, this process is repeatedly executed at predetermined time intervals.

The injection rate control device shown in FIG. 7 is executed every time the crank angle sensor 53 detects a reference position signal indicating that the piston 10 of the diesel engine 2 is at a predetermined position before the top dead center. You.

First, in step 200, processing for reading the piezoelectric element voltage V is performed. In the following step 210, it is determined whether or not the read piezoelectric element voltage V has exceeded the new control reference voltage Vth ^* calculated in step 180. Here, if it is determined that the piezoelectric element voltage V has exceeded the control reference voltage Vth ^* , the process proceeds to step 220, where the application time T1, the short time T2, the fall time T3, and the dwell time calculated in the above-described injection amount calculation processing. A process for controlling the drive circuit 5 is performed so that the piezoelectric actuator 4 is controlled according to TDUEL.

After the execution of step 220, the process exits to "RETURN", and thereafter, this injection rate control process is repeatedly executed each time the crank angle sensor 53 detects the reference position signal.

If it is determined in step 210 that the piezoelectric element voltage V does not exceed the control reference voltage Vth ^* , the processing in step 220 is skipped, and the process returns to “RETURN”.

Next, the injection rate control achieved by the injection amount calculation processing and the injection rate control processing will be described with reference to the timing chart of FIG.

When the fuel injection pump 3 shifts to the compression stroke, the cam lift starts to increase, and the pressurizing chamber 24, the communication hole 45, and the variable volume chamber 44
The internal fuel pressure increases. This increase in fuel pressure causes the piezoelectric element 42 in the piezoelectric actuator 4 to receive a compressive force,
The piezoelectric element voltage V increases. Between the start of the compression stroke and the elapse of the dwell time TDUEL, power is stored in the capacitor 46 for pilot injection. Then, when the dwell time TDUEL has elapsed and time t1 has elapsed, the piezoelectric element voltage V exceeds the control reference voltage Vth ^* . Then capacitor 4
By discharging the electric charge stored in 6, the high voltage Vp is applied to the piezoelectric actuator 4 for a predetermined application time T1. As a result, the piezoelectric element 42 expands and the variable volume chamber 44
Volume is reduced. Accordingly, since the pressure in the fuel injection pipe increases and exceeds the valve opening pressure of the fuel injection valve, injection of sufficiently boosted fuel (pilot injection) is started, and the injection rate rapidly increases.

At time t2 after application time T1 has elapsed from time t1,
The electric charge applied to the piezoelectric actuator 4 is discharged. Therefore, the piezoelectric element 42 contracts, and the volume of the variable volume chamber 44 increases. Therefore, the pressure in the fuel injection pipe decreases and falls below the valve opening pressure of the fuel injection valve, so that the fuel injection is completed and the injection rate is rapidly reduced.

Thereafter, the cam lift amount is still increased, and the piezoelectric element 42 continues to contract. Therefore, at time t3, the pressure in the fuel injection pipe increases again, and exceeds the valve opening pressure of the fuel injection valve. As a result, the main injection of the fuel is started again, and the injection rate increases rapidly. During the main injection, the variable volume chamber 44 is cut off from the pressurizing chamber 24, so that the piezoelectric element voltage V has a predetermined value (generated voltage Vm) for a certain period of time. Thereafter, the pressure in the fuel injection pipe decreases as the cam lift decreases, and the fuel injection ends at time t4, and the injection rate also decreases rapidly.

As described above, in the present embodiment, at the time of the main injection in which the variable volume chamber 44 is cut off from the pressurizing chamber 24, the voltage application timing to the piezoelectric actuator 4 is determined based on the generated voltage Vm generated in the piezoelectric actuator 4. Control reference voltage Vt for judgment
Correct h. Then, when the piezoelectric element voltage V of the piezoelectric actuator 4 exceeds the corrected control reference voltage Vth ^* , the piezoelectric actuator 4 is driven to reduce the volume of the variable volume chamber 44 so as to execute the pilot injection. did.

Therefore, according to the present embodiment, the piezoelectric characteristics of the piezoelectric actuator 4 are varied among products, or a low-viscosity fuel is used, as shown by the characteristic β in FIG. Even if the time at which the voltage V reaches the control reference voltage Vth is later than the characteristic α, the control reference voltage Vth is compensated, so that the control reference voltage Vth is changed by Vth ^* by an amount corresponding to the time transmission ΔT. Can be. Therefore, the timing of voltage application to the piezoelectric actuator 4, that is, the pilot injection timing, can be determined at the optimal timing ta. This makes it possible to always perform pilot injection at a stable timing.

Further, since the above-described generated voltage Vm can be detected every time the main injection is performed during the injection rate control, it is possible to perform compensation in real time. Further, in the present embodiment, the variable volume chamber 44 is cut off from the pressurizing chamber 24 at the time of the main injection, so that the pressure fluctuation in the pressurizing chamber 24 does not propagate to the variable volume chamber 44. The generated voltage Vm has a substantially constant value during the main injection. Therefore, as compared with a configuration in which the generated voltage Vm is detected as a peak voltage, for example, the generated voltage Vm can be detected with high accuracy without separately providing a peak hold circuit or the like.

By the way, as described above, at the time of the main injection, the fuel in the pressurizing chamber 24 is pressurized with the reciprocation of the plunger 23, and when the pressure in the pressurizing chamber 24 reaches a predetermined pressure, the fuel injection valve 12 , The reciprocating operation by the plunger 23 and the open state of the fuel injection valve 12 are slightly different for each injection. When the reciprocating operation of the plunger and the valve opening state of the fuel injection valve vary, the pressure in the pressurizing chamber fluctuates due to the variation.

In this regard, according to the present embodiment, even if the above-described pressure fluctuation occurs in the pressurizing chamber during the main injection, the variable volume chamber
The pressure in 44 is not affected by this pressure fluctuation,
The voltage generated by the piezoelectric actuator 4 does not fluctuate irrespective of its piezoelectric characteristics and fuel properties. as a result,
More accurate correction of the reference voltage is performed, and the execution timing of the pilot injection can be further stabilized. In this embodiment, the control reference voltage Vth is corrected by directly reading the generated voltage Vm of the piezoelectric element 42, so that the fuel temperature detection and the fuel temperature sensor for the detection in the related art are not required.

[Effects of the Invention] As described above in detail, according to the fuel injection rate control device for a diesel engine of the present invention, the constant volume generated by the piezoelectric actuator during the main injection in which the variable volume chamber is shut off from the pressurizing chamber. Based on the voltage, the reference voltage for determining when to apply the voltage to the piezoelectric actuator is corrected. When the piezoelectric element voltage of the piezoelectric actuator exceeds the corrected reference voltage, the piezoelectric actuator is driven to drive the variable volume chamber. Since the pilot injection is executed by reducing the volume of the piezoelectric actuator, it is possible to compensate for variations in the piezoelectric characteristics of the piezoelectric actuator between products and changes in fuel properties. This has the effect that the pilot injection can be performed. In particular, in the present invention, since the variable volume chamber is isolated from the pressurizing chamber during the main injection, the voltage generated by the piezoelectric actuator is reduced due to the reciprocating operation of the plunger and the variation in the opening state of the fuel injection valve. It does not fluctuate irrespective of the piezoelectric characteristics and fuel properties, and it is possible to correct the reference voltage more accurately and to further stabilize the execution timing of the pilot injection.

[Brief description of the drawings]

1 is a diagram showing a basic configuration of the present invention, FIG. 2 is a diagram showing a schematic configuration of a fuel injection rate control device for a diesel engine according to an embodiment of the present invention, and FIG. , FIG. 4 is a partially enlarged sectional view of the vicinity of the plunger at the time of fuel intake, FIG. 5 is a partially enlarged sectional view of the vicinity of the plunger at the time of pilot injection, and FIG. FIG. 7 is a flowchart of an injection rate calculation process, FIG. 8 is a timing chart of various values, and FIG. 9 is a diagram showing a relationship between a piezoelectric element voltage and a control reference voltage together with problems of the prior art. M1 …… Diesel engine, M2 …… Fuel injection pump, M3 ……
Piezoelectric actuator, M4 ... Pilot injection timing control means, M5 ... Reference voltage correction means, 2 ... Diesel engine, 3 ... Fuel injection pump, 4 ... Piezoelectric actuator, 7 ... Pilot injection timing control means and reference voltage Electronic control unit (ECU) as correction means, 12 ...
... Fuel injection valve, 21 ... Cylinder, 23 ... Plunger, 24
…… Pressurizing chamber, V …… Piezo element voltage, Vm …… Generating voltage, Vt
h: Control reference voltage.

Continuation of the front page (56) References JP-A-64-73152 (JP, A) JP-A-62-182445 (JP, A) JP-A-2-49953 (JP, A) JP-A-62-248853 (JP) , A) JP-A-61-275532 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-41/40

Claims (1)

(57) [Claims] 1. A pressurizing chamber for sucking and boosting fuel by reciprocating a plunger inserted into a cylinder with driving of a diesel engine, and prior to main injection in a process of reciprocating the plunger. A fuel injection pump having a variable volume chamber communicated with the pressurizing chamber during pilot injection and shut off during main injection, generating a voltage corresponding to the pressure in the variable volume chamber, and performing an expansion operation by applying the voltage; A piezoelectric actuator for increasing the pressure of the fuel in the variable volume chamber to perform pilot injection by the fuel injection valve; and, when the pressurizing chamber and the variable volume chamber of the fuel injection pump communicate with each other, increasing the pressure of the variable volume chamber. When the voltage generated by the piezoelectric actuator reaches the reference voltage, a pilot injection timing that applies a voltage to the piezoelectric actuator to perform pilot injection Control means, and reference voltage correction means for correcting a reference voltage used in the pilot injection timing control means based on a constant voltage generated in the piezoelectric actuator during the main injection. A fuel injection rate control device for a diesel engine.