JPH04101045A - Fuel injection rate controller of diesel engine - Google Patents

Abstract

PURPOSE:To enable compensation of dispersion in piezoelectric characteristics of a piezoelectric actuator among products and change in fuel properties by correcting reference voltage used by a pilot injection timing control means based on voltage generated at the piezoelectric actuator at the time of main injection. CONSTITUTION:Pressure of fuel in a variable capacity chamber is also raised, and a piezoelectric actuator M3 generates voltage corresponding to the pressure in the variable capacity chamber. When voltage reaches reference voltage, a pilot injection timing control means M4 impresses voltage on the piezoelectric actuator M3. By this impression of the voltage, the piezoelectric actuator M3 is extended and raises pressure of the fuel in the variable capacity chamber so as to carry out a pilot injection by an injection valve. Also, in the process of pressure rise of the fuel in a pressurized chamber, when the variable capacity chamber is shut out from the pressurized chamber after the pilot injection is carried out, a main injection is carried out by the injection valve. At this main injection, pressure in the variable capacity chamber is not affected by the pressurized chamber and the voltage generated at the piezoelectric actuator becomes almost constant. At this main injection, a reference voltage correcting means M5 corrects the reference voltage used by the pilot injection timing control means M4 based on the voltage generated at the piezoelectric actuator M3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel injection rate control device for a diesel engine using a piezoelectric actuator, and more specifically, the present invention relates to a fuel injection rate control device for a diesel engine using a piezoelectric actuator, and more specifically, a variable volume chamber that communicates with a pressurizing chamber in a fuel injection pump. 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 the variable volume chamber using a piezoelectric actuator.

[Conventional technology] From the past. When injecting fuel in a diesel engine, this is done by performing a so-called pilot injection, which is a preliminary injection prior to the main injection. It is known that noise and harmful exhaust gases generated by diesel engines can be reduced. There is a fuel injection rate control device that uses a piezoelectric actuator to perform this pilot injection. In this type of control device, the voltage generated by the piezoelectric actuator corresponds to the phase of the pressure stroke of the fuel injection pump, that is, as the pressure stroke progresses, the piezoelectric actuator contracts and the generated voltage increases. When the generated voltage reaches a predetermined reference voltage, a high voltage is applied to the piezoelectric actuator to extend the piezoelectric actuator and perform a pilot injection.

However, since the reference voltage is always constant in the control device, it is not possible to compensate for changes in the viscosity of the fuel, resulting in the following problems. In other words, when the temperature of the fuel increases, the viscosity of the fuel decreases, so the amount of leakage of the fuel increases, and the pressure applied to the piezoelectric actuator decreases. As a result, high voltage cannot be applied to the piezoelectric actuator at optimal timing.

Therefore, the present applicant has previously proposed a fuel injection rate control device that is provided with a fuel temperature detection means for detecting the temperature of the fuel, and a reference voltage lowering means for lowering the reference voltage as the fuel temperature rises. (Patent Application No. 1-333737). In this device, as the fuel temperature detected by the fuel temperature detection means increases, the reference voltage reduction means lowers the reference voltage.

Therefore, a pressure drop in the piezoelectric actuator due to a rise in fuel temperature can be compensated for by a drop in the reference voltage, and pilot injection can be performed at a stable timing.

[Problems to be Solved by the Invention] However, although the conventional technology can compensate for temperature changes in the fuel as described above, it is difficult to compensate for variations in the piezoelectric characteristics of piezoelectric actuators between products and fuel properties such as the type of diesel oil. are not taken into consideration and cannot be compensated for. In particular, when using fuel with low viscosity, there is a problem in that it takes time to increase the pressure in the pressurizing chamber, resulting in a delay in the timing of pilot injection.

FIG. 9 shows the relationship between the piezoelectric element voltage (■) and the reference voltage vth, where α is the target characteristic of the piezoelectric element voltage, and β is the characteristic of the piezoelectric element voltage when a fuel with low viscosity is used. From this figure, it can be seen that for the characteristic α, the piezoelectric element voltage V reaches the reference voltage vth at time ta, whereas for the characteristic β, the piezoelectric element voltage V reaches the reference voltage vth at time T, which is delayed by ΔT from the time ta. . Therefore, with the characteristic β, voltage is not applied to the piezoelectric element at the optimal timing ta.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to be able to compensate for product-to-product variations in the piezoelectric characteristics of piezoelectric actuators and changes in fuel properties, and to always drive piezoelectric actuators at optimal timing. 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 provides a fuel injection pump equipped with a type of fuel injection pump in which a variable volume chamber communicates with a pressurizing chamber during pilot injection, and a variable volume chamber is isolated from the pressurizing chamber during main injection. The injection rate control device is designed with the focus on the fact that during main injection, where the pressure in the variable volume chamber is not affected by the pressurizing chamber, the voltage generated by the piezoelectric actuator remains approximately constant for a predetermined period of time.

Therefore, in order to achieve the above object, the present invention is as shown in FIG. As the diesel engine M1 is driven, a plunger inserted into the cylinder reciprocates to create a pressurized chamber that sucks in and pressurizes fuel; a fuel injection pump M2 having a variable volume chamber that communicates with a pressurizing chamber and is shut off during main injection; A piezoelectric actuator M3 that increases the pressure of fuel in the volume chamber to perform pilot injection by the fuel injection valve; and a piezoelectric actuator M3 that increases the pressure of the variable volume chamber when the pressurization chamber of the fuel injection pump M2 and the variable volume chamber communicate with each other. A fuel injection rate control device for a diesel engine, comprising a pilot injection timing control means M4 for applying a voltage to the piezoelectric actuator M3 to perform a pilot injection when the voltage generated by the actuator M3 reaches a reference voltage. A reference voltage correction means M5 is provided for correcting the reference voltage used in the pilot injection timing control means M4 based on the voltage generated by the piezoelectric actuator M3 during injection.

[Operation] According to the present invention, as shown in FIG.
When the plunger of the fuel injection pump M2 reciprocates with the driving of the fuel injection pump M2, fuel is sucked into the pressurizing chamber and the pressure is increased.

When the variable volume chamber is brought into communication with the pressurizing chamber during the process of increasing the pressure of the fuel in the pressurizing chamber, the pressure of the fuel in the variable volume chamber is also increased.

At this time, the piezoelectric actuator M3 generates a voltage according to the pressure inside the variable volume chamber. When this generated voltage reaches the reference voltage, the pilot injection timing control means M4 applies a voltage to the piezoelectric actuator M3.

By applying this voltage, the piezoelectric actuator M3 expands, increases the pressure of the fuel in the variable volume chamber, and causes the injection valve to perform pilot injection.

Further, in the process of increasing the pressure of the fuel in the pressurizing chamber,
When the variable volume chamber is cut off from the pressurizing chamber after the pilot injection is performed, the main injection by the injection valve is performed. 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 remains approximately constant. Based on the voltage generated by the piezoelectric actuator M3 during this main injection, the reference voltage correction means M5 corrects the reference voltage used in the pilot injection timing control means M4.

Therefore, even if the piezoelectric element voltage characteristics vary from the target characteristics due to product-to-product variations in the piezoelectric characteristics of the piezoelectric actuator M3 or fuel properties such as fuel type, the reference voltage for pilot injection is corrected. , the piezoelectric actuator M3 is always driven at optimal timing.

“Embodiment” An embodiment embodying the present invention will be described below with reference to the drawings.

Figure 2 shows the fuel injection rate control device for diesel engine 2.
1 is a diagram showing a schematic configuration of this fuel injection rate control device 1.
A distribution type fuel injection pump 3 that pressurizes and pumps fuel to be supplied to the diesel engine 2, a piezoelectric actuator 4 attached to the fuel injection pump 3, a drive circuit 5 that drives the piezoelectric actuator 4, and a high Voltage power supply 6
and an electronic control device (hereinafter referred to as
It consists of 7 (simply referred to as ECU).

A combustion chamber 8 of the diesel engine 2 is formed by a cylinder 9, a piston 1O, and a cylinder head 11, and a fuel injection valve 12 is disposed in the combustion chamber 8. A water temperature sensor 13 is attached to the cylinder 9 to detect the cooling water temperature Thw of the diesel engine 2.

Further, a fuel foot pump 16, a pulse carrier 17, and a coupling 18 are connected to a drive shaft 15 that is inserted through and supported at the rear part of the fuel injection pump 3 (left side in FIG. 2). and. 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 rotate together with the drive shaft 15.

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

The plunger 23 is connected to the coupling 18 at the front end of the drive shaft 15 so that it can rotate integrally with the coupling 18 and can reciprocate in the front-rear direction. That is, a low cylinder 25 is rotatably connected to the front end of the drive shaft 15, and a plurality of cam rollers 26 are rotatably attached to the outer periphery of the low cylinder 25. On the other hand, plunger 2
A cam plate 27 having a cam face is provided at the rear end of 3.
The plunger 23 and the cam plate 27 are urged rearward by a spring 28.

Therefore, as the drive shaft 15 rotates, the plunger 23 rotates and reciprocates in the front-rear direction, distributing and pumping the fuel.

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

FIG. 3 is an enlarged cross-sectional view of the plunger 23 and cylinder 21, and the front end of the plunger 23 has an outer periphery. The same number of intake ports 30 as the number of cylinders of the diesel engine 2 are formed. A central port 31 is formed at the axis of the plunger 23, and the front end of this central port 31 opens into the pressurizing chamber 24. An annular groove 32 is formed on the outer periphery of the plunger 23 near the rear of the suction port 30, and the annular groove 32 communicates with the central port 31 through a port 33.

Further, distribution ports 34 of the same number as the number of cylinders of the diesel engine 2 are recessed at rear positions of the annular groove 32 on the outer periphery of the plunger 23, and each distribution port 34 communicates with the center port 3I.

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 on the outer peripheral surface of the plunger 23. ing. This spill port 35
is for overflowing the excess fuel pressurized in the pressurizing chamber 24.

On the other hand, the block 20 includes a suction passage 37 that communicates the low pressure chamber 36 in the fuel injection pump 3 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 to communicate the fuel injection valve 12 of the diesel engine 2 with the inner surface of the cylinder 21, and a delivery valve 39 is provided in the middle of each distribution passage 38. Or is provided.

The piezoelectric actuator 4 includes a casing 40 screwed to the lower part of the block 20, a piston 41 fitted into the space inside the casing 40 so as to be slidable in the vertical direction, and an upper half inserted into the piston 4I. , 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 for electric charges generated by the piezoelectric element 42 or electric charges supplied to the piezoelectric element 42. . A space surrounded by the casing 40, piston 41, and 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 disc-shaped members made of PZT (lead zirconate titanate). When an electric charge is supplied through the signal line 43, the piezoelectric element 42 expands and causes the piston 4I to slide upward, so that the volume of the variable volume chamber 44 decreases.

In contrast to the above, when the electric charge is discharged through the signal line 43, the piezoelectric element 42 contracts and causes the piston 41 to slide downward, so that the volume of the variable volume chamber 44 increases. Note that when compressive force acts on the piezoelectric element 42 as the fuel pressure inside the variable volume chamber 44 increases, the piezoelectric element 42 discharges an amount of charge to the signal line 43 in accordance with the strain caused by the compressive force.

In the fuel injection pump 3 configured as described above, as the drive shaft 15 rotates, the fuel foot pump 16
When the cam plate 27 and the plunger 23 rotate and the cam plate 27 rides down from the cam roller 26 of the roller link 25, the plunger 23 moves rearward and performs a fuel suction stroke.

In this suction stroke, as shown in FIG.
is in communication with the suction passage 37, or the distribution port 34 is blocked from the distribution passage 38.

On the other hand, 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. During pilot injection, as shown in FIG. 5, the suction port 30 is blocked 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. Furthermore, at the end of the pilot injection, although not shown, the suction port 30 is shut off from the suction passage 37, the annular groove 32 from the communication hole 45, and the distribution port 34 from the distribution passage 38. Furthermore, during 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.
Distribution port 34 communicates with distribution passageway 38.

As shown in FIG. 2, the drive circuit 5 that drives the piezoelectric actuator 4 includes a capacitor 46 connected in parallel to the high voltage power supply 6, and a current-carrying thyristor connected in series between the capacitor 46 and the piezoelectric actuator 4. 47 and the energizing coil 48, the discharging thyristor 49 and the discharging coil 50 connected in parallel to the piezoelectric actuator 4, and the E
A trigger pulse is output to the energizing thyristor 47 at the rising edge of a rectangular signal that is a drive circuit control signal output from the CU 7, and a trigger pulse is output to the discharging thyristor 49 at the falling edge of the rectangular signal. It is composed of a generator 51.

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 becomes conductive at the rise of the rectangular signal from the ECU 7, the charge stored in the capacitor 46 is transferred to the piezoelectric actuator. On the other hand, when the discharging thyristor 49 becomes conductive at the fall of the rectangular signal from the ECU 7, the charge stored in the piezoelectric actuator 4 is discharged.

By the way, the fuel injection rate control device 1 of the diesel engine 2 includes, as detectors, an accelerator sensor 52 that detects the opening degree of the accelerator pedal, and an accelerator sensor 52 that detects the opening degree of the accelerator pedal, in addition to the rotational speed sensor 29 and the water temperature sensor 13 described above. A crank angle sensor 53 is provided close to the signal disc plate.

The ECU 7 includes a CPU 54, a ROM 55, and a RAM 56.
, and a timer 57, which are connected to an input/output section 59 via a common bus 58. The detection signals of the rotational speed sensor 29, the water temperature sensor 13, the accelerator sensor 52, and the piezoelectric element voltage of the piezoelectric element 42 are input to the CPU 54 via the input/output section 59, and the CPU 54 is driven via the input/output section 59. circuit 5
and outputs a control signal to the high voltage power supply 6. Also, ROM
55 stores the reference voltage Vmo of the piezoelectric element 42 during main injection of the fuel injection pump 3.

Note that the drive circuit 5 and the ECU 7 include an on-vehicle battery 60.
Electric power is supplied from the ignition switch 61 through the ignition switch 61.

Next, the processing executed by the ECU 7 will be explained based on the flowcharts shown in FIGS. 6 and 7.

The injection amount calculation process shown in Fig. 6 is as follows. diesel engine 2
It is repeatedly executed at predetermined time intervals upon activation of the . First, in step 100, from the detection results of the rotational speed sensor 29, the accelerator sensor 52, and the water temperature sensor 13, the engine rotational speed Ne, the accelerator opening Accp, and the cooling water temperature Th
Load w.

In subsequent steps 110 to 150, various values related to the pilot injection, ie, control reference voltage vth, application time TI, short time T2. Falling time T3. The dwell time TDUEL (see FIG. 8) is calculated.

To explain in detail, the control reference voltage vth is a piezoelectric element voltage when applying a high voltage to the piezoelectric actuator 4 in order to execute pilot injection, and is a piezoelectric element voltage when applying a high voltage to the piezoelectric actuator 4 to execute pilot injection, and
e, accelerator opening Accp, and cooling water temperature T h w as variables. Therefore, in step 110, a three-dimensional map stored in advance in the ROM 55 is used to calculate the engine speed Ne, accelerator opening Accp, and cooling water temperature Thw read in step 100.
The control reference voltage vth is calculated based on.

In addition, the application time Tl, the short time T2, and the fall time T3 are various values that determine the pilot injection rate, and the dwell time TDUEL is the time for storing electricity in the capacitor 46 for pilot injection, and these values are based on the engine rotation speed. They are each defined with Ne as a variable.

For this reason, in steps 120 to 150, the ROM
Using the one-dimensional map stored in 55, step 1
Based on the engine rotation speed Ne read at 00, the application time T1, short time T2, fall time T3
and dwell time TDUEL are calculated respectively.

After executing step 150, the process proceeds to step 160, where the voltage Vm generated by the piezoelectric element 42 during the main injection is read. In the following step 170, the generated voltage V+n read in step 160 is divided by the reference voltage Vmo stored in advance in the ROM 55 to calculate a correction coefficient K (-Vm/Vmo). After that, the process moves to step 180, and the step 11
A new control reference voltage v th'' is calculated by multiplying the control reference voltage vth calculated in step 0 by the correction coefficient K. After executing step 180, the process exits to rNEXT'' and ends this process. Thereafter, this process is repeatedly executed at predetermined time intervals.

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

First, in step 200, a process of reading the piezoelectric element voltage V is performed. In the following step 210, it is determined whether the read piezoelectric element voltage V exceeds the new control reference voltage v th''' calculated in step 180. Here, it is determined whether the piezoelectric element voltage V or the control reference voltage v th"
If it is determined that the injection amount has been exceeded, the process proceeds to step 220, where the application time TI, short time T2, fall time T3, and dwell time TD calculated in the injection amount calculation process described above are calculated.
A process for controlling the drive circuit 5 is executed so that the piezoelectric actuator 4 is controlled according to the UEL.

After executing step 220, the process exits to ``rRETURN'', and thereafter this injection rate control process is performed by the crank angle sensor 53.
The process is repeated and executed each time the reference position signal is detected.

Note that if it is determined in step 210 that the piezoelectric element voltage V does not exceed the control reference voltage v th'', step 2
Skip step 20 and exit to rRETURNJ.

Next, the injection rate control achieved by the injection amount calculation process and the injection rate control process will be described with reference to the timing chart of FIG. 8.

When the fuel injection pump 3 shifts to the compression stroke, the cam lift amount begins to increase, and the fuel pressure inside the pressurizing chamber 24, the communication hole 45, and the variable volume chamber 44 increases.

Due to this increase in fuel pressure, the piezoelectric element 42 in the piezoelectric actuator 4 receives a compressive force, and the piezoelectric element voltage V increases. Between the start of the compression stroke and the elapse of the dwell time TDUEL, the capacitor 46 is closed for pilot injection.
Electricity is stored in the

Then, at time t1 after the dwell time TDUEL has elapsed, the piezoelectric element voltage V exceeds the control reference voltage v th''.Then, the charge stored in the capacitor 46 is discharged, causing the piezoelectric actuator 4 to have a predetermined value. As a result, the piezoelectric element 42 expands and the volume of the variable volume chamber 44 decreases.

Therefore, the internal pressure of the fuel injection pipe increases and exceeds the opening pressure of the fuel injection valve, so that injection (pilot injection) of sufficiently pressurized fuel is started, and the injection rate is rapidly increased.

At time t2, after the application time TI has elapsed from time t1, the charge applied to the piezoelectric actuator 4 is discharged. Therefore, the piezoelectric element 42 contracts and the variable volume chamber 4
The volume of 4 increases. Therefore, the pressure inside the fuel injection pipe decreases and becomes lower than the opening pressure of the fuel injection valve, so that fuel injection ends and the injection rate quickly decreases.

Thereafter, the cam lift i continues to rise and the piezoelectric element 42 continues to contract. Therefore, at time t3, the pressure inside the fuel injection pipe increases again and exceeds the opening pressure of the fuel injection valve. As a result, main injection of fuel starts again and the injection rate increases rapidly. During this main injection, the variable volume chamber 44 is cut off from the pressurizing chamber 24, so the piezoelectric element voltage V remains at a predetermined value (occurrence 1 [pressure Vm)] for a certain period of time. Thereafter, the pressure inside the fuel injection pipe decreases as the cam lift amount decreases, and fuel injection ends at time t4, and the injection rate also quickly decreases.

In this way, in this embodiment, either the variable volume chamber 44 or the pressurizing chamber 24
During the main injection cut off from the piezoelectric actuator 4
The control reference voltage vth for determining the timing of voltage application to the piezoelectric actuator 4 is corrected based on the generated voltage Vm generated in the piezoelectric actuator 4.

Then, when the piezoelectric element voltage of the piezoelectric actuator 4 exceeds the corrected control reference voltage v th'', the piezoelectric actuator 4 is driven to reduce the volume of the variable volume chamber 44 and execute a pilot injection. I made it.

Therefore, according to this embodiment, if the piezoelectric characteristics of the piezoelectric actuator 4 vary between products or if fuel with low viscosity is used, the piezoelectric element of the piezoelectric actuator 4 may Even if the time when the voltage V reaches the control reference voltage vth is later than the characteristic α, by compensating the control reference voltage vth, the control reference voltage vth is changed by an amount corresponding to the time delay ΔT. be able to.

Therefore, the timing of voltage application to the piezoelectric actuator 4, ie, the pilot injection timing, can be determined at the optimal timing ta. This makes it possible to always perform pilot injection at stable timing.

Further, since the above-mentioned generated voltage Vm can be detected every time main injection is performed during injection rate control, real-time compensation is possible. Furthermore, unlike the peak voltage, the generated voltage Vm has a substantially constant value during a predetermined period (during main injection), so the detection accuracy of the generated voltage Vm is high. In this embodiment, since the control reference voltage vth is corrected by directly reading the voltage Vm generated by the piezoelectric element 42, there is no need to detect the fuel temperature in the prior art and to use a fuel temperature sensor for the detection.

[Effects of the Invention] As detailed above, according to the fuel injection rate control device for a diesel engine of the present invention, the generated voltage generated in the piezoelectric actuator during main injection when the variable volume chamber is cut off from the pressurizing chamber. Based on this, the reference voltage for determining when to apply voltage to the piezoelectric actuator is corrected, and when the piezoelectric element voltage of the piezoelectric actuator exceeds this corrected reference voltage, the piezoelectric actuator is driven to open the variable volume chamber. Since the volume of the pilot injection was reduced and the pilot injection was performed,
It is possible to compensate for product-to-product variations in the piezoelectric characteristics of the piezoelectric actuator and changes in fuel properties, and the piezoelectric actuator can always be driven at the optimal timing to perform stable pilot injection.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is a diagram showing the schematic configuration of a fuel injection rate control device for a diesel engine according to an embodiment of the present invention, and Fig. 3 is a diagram showing the main injection time. FIG. 4 is a partial enlarged sectional view of the vicinity of the plunger during fuel intake, FIG. 5 is a partial enlarged sectional view of the vicinity of the plunger during pilot injection, and FIG. 6 is a partial enlarged sectional view of the vicinity of the plunger during pilot injection. 7 is a flowchart of the injection rate calculation process, FIG. 8 is a timing chart of each product value, and FIG. 9 is a diagram showing the relationship between the piezoelectric element voltage and the control reference voltage together with the problems of the prior art. Ml...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...Electronic control unit (ECU) as pilot injection timing control means and reference voltage correction means, l2...Fuel injection valve, 21...Cylinder , 23... plunger, 24...
...pressure chamber, ■...piezoelectric element voltage, Vm...generated voltage, vth...control reference voltage. Patent applicant Toyota Motor Corporation agent Patent attorney Hironobu Onda (and one other person)a T Time

Claims (1)

[Claims] 1. As the diesel engine is driven, a plunger inserted into the cylinder reciprocates to draw in and pressurize the fuel, and a pressurized chamber is provided during the pilot injection prior to the main injection during the reciprocating process of the plunger. A fuel injection pump has a variable volume chamber that communicates with a pressure chamber and is shut off during main injection; and a fuel injection pump that generates a voltage according to the pressure within the variable volume chamber, expands upon application of the voltage, and expands the variable volume chamber. a piezoelectric actuator that increases the pressure of fuel to perform pilot injection by a fuel injection valve; and a voltage generated by the piezoelectric actuator as the pressure of the variable volume chamber increases when the pressurization chamber of the fuel injection pump and the variable volume chamber communicate with each other. A fuel injection rate control device for a diesel engine, comprising pilot injection timing control means for applying a voltage to the piezoelectric actuator to perform a pilot injection when the piezoelectric actuator reaches a reference voltage. A fuel injection rate control device for a diesel engine, comprising a reference voltage correction means for correcting a reference voltage used in the pilot injection timing control means based on a voltage generated in the pilot injection timing control means.