JPH01262344A - Pilot injection control device for diesel-engine - Google Patents

Abstract

PURPOSE:To always obtain optimum pilot injection in a pilot injection control device in which the increasing rate of the pressure of fuel in a fuel pressurizing chamber is controlled in accordance with an elongation of a piezoelectric element, by increasing the electric charge applied to the piezoelectric element in accordance with an increase in load of an internal combustion engine upon pilot injection. CONSTITUTION:In a distribution type injection pump 1, when a pluger 9 is moved leftward, fuel in a fuel pressurizing chamber 20 is pressurized, and thereafter when a voltage is applied to a piezoelectric element 37 which is therefore elongated, the pressure of fuel in a pressure control chamber 39 and the pressurizing chamber 20 rapidly increase so that a fuel injection valve 25 performs pilot injection. When the plunger 9 is further moved to pressurize fuel in the pressurizing chamber 20, main injection is carried out. In this arrangement, there is provided a load sensor 43 so as to control such that an electric charge applied to the piezoelectric element 57 in accordance with a detected increase in the load of an engine upon pilot injection, and accordingly, the injection rate is increased in accordance with an increase in the load, thereby it is possible to always obtain optimum pilot injection.

Description

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

[Conventional technology]

It is equipped with a fuel pressurizing chamber pressurized by a plunger and a piezoelectric element for increasing the fuel pressure in the fuel pressurizing chamber, and as the amount of expansion of the piezoelectric element increases, the fuel pressure in the fuel pressurizing chamber increases. A diesel engine is known (Japanese Unexamined Patent Application Publication No. 61-25925) in which the fuel injection rate is increased and fuel in a fuel pressurizing chamber is injected from a fuel injection valve. In this diesel engine, a certain high voltage is applied to the piezoelectric element during pilot injection to cause the piezoelectric element to expand by a certain amount, thereby increasing the fuel pressure in the fuel pressurizing chamber and performing pilot injection from the fuel injection valve. I have to.

On the other hand, a diesel engine is known in which the injection period is controlled while the injection rate during pilot injection is maintained almost constant in order to control the pilot injection amount according to the operating state of the engine. -217758).

[Problem to be solved by the invention]

By the way, in a diesel engine, the ratio of the pilot injection amount to the main injection amount has a large effect on noise generation and NOx emissions. That is, if the ratio of the pilot injection amount to the main injection amount is too small, the ignition delay period will be long, and when ignition occurs, the pressure will rise rapidly and the combustion pressure will become high. Such a sudden pressure rise causes large combustion noise, and as the combustion pressure increases, the combustion temperature also increases, resulting in a large amount of NOx being generated. On the other hand, if the ratio of the pilot injection amount to the main injection amount becomes too large, the combustion pressure starts to rise immediately after the pilot injection, resulting in a high maximum combustion pressure, and as a result, a large amount of NOx is generated. Therefore, there is an optimal value for the ratio of the pilot injection amount to the main injection amount, and if the pilot injection amount is set to the optimal value relative to the main injection amount, gentle combustion will occur, and the maximum combustion pressure will also be lower, which will cause combustion noise. and no.

The occurrence of can be suppressed.

However, in the diesel engine described in JP-A No. 61-25925, the pilot injection amount is almost constant regardless of the engine load, that is, the main injection amount, so the ratio of the pilot injection amount to the main injection amount is determined by the engine load. Therefore, if the ratio of the pilot injection amount to the main injection amount is small, combustion noise and a large amount of NOx will be generated, and if it is large, a large amount of NOx will be generated.

On the other hand, in the diesel engine described in JP-A-58-217758, the pilot injection amount is controlled by controlling the pilot injection period, but in reality the period from the completion of pilot injection to the start of main injection is extremely short. Therefore, when lengthening the pilot injection period, there is a problem that either the pilot injection start time must be earlier than the optimal start time, or the main injection start time must be delayed than the optimal start time.

[Means to solve the problem]

In order to solve the above problems, the present invention includes a fuel pressurizing chamber pressurized by a plunger, and a piezoelectric element for increasing the fuel pressure in the fuel pressurizing chamber,
In a diesel engine in which the fuel pressure in the fuel pressure chamber increases as the amount of expansion of the piezoelectric element increases, and the fuel in the fuel pressure chamber is injected from the fuel injection valve, the piezoelectric element increases depending on the engine load. The piezoelectric element is equipped with a supply charge amount control device that controls the amount of charge supplied to the piezoelectric element, and increases the amount of charge supplied to the piezoelectric element in response to an increase in engine load during pilot injection, thereby increasing the amount of elongation of the piezoelectric element. ing.

〔Example〕

Referring to FIG. 2, reference numeral 1 designates a distribution type injection pump, and the injection pump 1 has a housing 2 which projects into a fuel chamber 3 within the housing 2 and which is connected to a crankshaft (not shown) of the engine via a pulley 4. A drive shaft 5 that is rotationally driven is arranged. A fuel supply pump 6 is integrally formed in the housing 2, and in order to make it easier to understand the structure of the fuel supply pump 6, FIG.
It is shown rotated by a degree. A rotor 7 of a fuel supply pump 6 , a timing gear 8 disposed within the fuel chamber 3 , and a coupling 10 for driving a plunger 9 are fixed to the drive shaft 5 .

A cylinder 11 is formed within the housing 2, and the right end portion of the plunger 9 is inserted into the cylinder 11. On the other hand, a disk-shaped cam plate 13 having a cam surface 12 formed thereon and a coupling 10 are fixed to the left end of the plunger 9. In this way, the plunger 9 and the drive shaft 5 are connected to each other via the coupling 10, so that when the drive shaft 5 rotates, the plunger 9 is rotated accordingly. The coupling 10 connects the drive shaft 5 and the plunger 9 so that the plunger 9 can move in the axial direction, and therefore the plunger 9 can move in the axial direction while rotating.

A roller ring 14 is arranged in the fuel chamber 3 so as to surround the coupling 10.
can rotate around the axis of the plunger 9. The roller ring 14 is provided with a lever 15 extending downward, and a cam roller 16 is rotatably mounted on the roller ring 14, the roller ring 14 moving on the cam surface 12 in contact with the cam surface I2. A timer cylinder 18 having a timer piston 17 is provided below the roller ring 14, and the lower end of the lever 15 engages with the timer piston 17. In order to make it easier to understand the structure of the timer piston 17, the timer cylinder 18 is shown rotated by 90 degrees in FIG. It is possible to move in the direction. When the timer piston 17 moves in this manner, the roller ring 14 is rotated accordingly. This timer piston 17 is provided to rotate the roller ring 14 and control the injection timing.

Note that the fuel discharged from the fuel supply pump 6 is transferred to the fuel chamber 3.
supplied within.

On the cam surface 12 of the cam plate 13, there are the same number of cylinders as the number of cylinders.
For example, four convex portions are formed, and the cam surface 12 has a return spring 1.
It is constantly pressed onto the cam roller 16 by the spring force of 9. When the drive shaft 5 rotates, the plunger 9 is moved in the axial direction when the convex portion of the cam surface 12 engages with the cam roller 16, so that the plunger 9 reciprocates four times during one revolution of the drive shaft 5.

On the other hand, the plunger 9 has a fuel discharge port 21 and a fuel relief hole 22 that communicate with a fuel pressurizing chamber 20 formed in the cylinder 11, and further has a fuel discharge port 21 on the inner peripheral surface of the cylinder 11. Four fuel outflow holes 23 are formed that can communicate with the outlet 21. These fuel outflow holes 23 are each connected to a fuel injection valve 25 of a corresponding cylinder via a delivery valve 24.

When the plunger 9 moves to the left, the fuel in the fuel chamber 3 is supplied into the fuel pressurizing chamber 20 via the fuel supply path 26, and when the plunger 9 moves to the right, the fuel in the fuel pressurizing chamber 20 is supplied to the fuel pressurizing chamber 20. Compressed. Next, after the fuel discharge port 21 of the plunger 9 communicates with one of the fuel outflow holes 23, the high pressure fuel in the fuel pressurization chamber 20 is injected from the fuel injection valve 25.

In this manner, the fuel discharge port 21 of the plunger 9 sequentially communicates with the four fuel outflow holes 23, so that fuel is sequentially injected from the fuel injection valve 25 of each cylinder.

On the other hand, the fuel relief hole 2 of the plunger 9 is located on the plunger 9.
A spill ring 27 capable of closing 2 is slidably inserted into the fuel chamber 3, and a lever 28 for moving the spill ring 27 is inserted into the fuel chamber 3.

This lever 28 is rotatably attached to the housing 2 by a pivot pin 28a, and the lower end of the lever 28 is fitted into a groove formed on the outer peripheral surface of the spill ring 27. On the other hand, the upper end of the lever 28 is connected to a control lever 30 via a control spring 29. The control lever 30 is rotatably supported by the housing 2.
is connected to the accelerator pedal 31. accelerator pedal 3
When the amount of depression 1 becomes smaller, the lever 28 is rotated clockwise. As a result, since the spill ring 27 moves to the left, when the plunger 9 moves to the right, the fuel relief hole 22 of the plunger 9 opens into the fuel chamber 3 at a relatively early stage, and the fuel from the fuel injection valve 25 is released. Fuel injection action stops. On the other hand, when the accelerator pedal 31 is depressed and the spill ring 27 is moved to the right, the plunger 9 is moved considerably to the right until the fuel escape hole 22 opens into the fuel chamber 3. Therefore, the fuel injection amount is controlled by the position of the spill ring 27, that is, by the depression of the accelerator pedal 31. Further, a governor 33 is provided within the fuel chamber 3 and is rotated by a gear 32 that meshes with the timing gear 8 .

This governor 33 has a centrifugal weight 34 and a centrifugal weight 3.
4, the governor sleeve 35 moves to the right as the rotation speed increases.

When the governor sleeve 35 moves, the lever 28 is rotated accordingly, so that the governor 33 also controls the fuel injection amount.

On the other hand, the piezoelectric actuator 36 is coaxially connected to the plunger 9.
is placed. The piezoelectric actuator 36 includes a piezoelectric element 37, a piston 38 driven by the piezoelectric element 37, a pressure control chamber 39 defined by the piston 38, and is arranged within the pressure control chamber 39 so as to direct the piston 38 to the right. The pressure control chamber 39 is connected to the fuel pressurizing chamber 20 through a communication hole 41.

On the other hand, for example, four protrusions 4a are formed on the pulley 4,
A reference signal generator 42 is provided which generates an output pulse when approaching the protrusion 4a.

Further, a load sensor 43 that detects the rotation angle of the control lever 30, that is, the engine load, is connected to the control lever 30. Output signal S1 of these reference signal generators 42
The output signal S2 of the load sensor 43 is input to the control circuit 45. The output voltage V of a high voltage power supply 50 is applied to the piezoelectric element 37 via a drive circuit 60. Drive circuit 60
is controlled by the output signal S3 of the control circuit 45, and the output voltage V of the high voltage power supply 50 is controlled by the output signal S4 of the control circuit 45.
controlled by

Next, referring to FIG. 1, the control circuit 45 shown in FIG. 2 receives the output signal S of the reference signal generator 42 as shown in FIG.
1, and a delay circuit 47 that delays the rectangular wave shaped by the shaping circuit 46 for a predetermined period of time, and the output signal S of the delay circuit 47
3 is supplied to the drive circuit 60. Furthermore, the control circuit 45 is an applied voltage control circuit 4 that controls a control signal S4 applied to the high voltage power supply 50 in accordance with the output signal S2 of the load sensor 43.
8. In response to control signal S4, high voltage power supply 50 generates an output voltage V that increases in proportion to engine load, as shown in FIG. This high voltage power supply 50 is, for example, a DC-D
The output voltage V is controlled by controlling this DC-DC converter using a control signal S4.

The drive circuit 60 includes a capacitor 61 and a first thyristor 62.
, a charging coil 63, a second thyristor 64, a discharging coil 65, and a trigger generator 66 that controls the first thyristor 62 and the second thyristor 64 based on the output signal S3 of the delay circuit 42. .

Next, injection control according to the present invention will be explained with reference to FIG. In addition, in FIG. 3, the solid line shows the time of high load operation, and the broken line shows the time of low load operation.

The reference signal S1, indicated by a in FIG. (3rd
Figure b). The trigger generator 66 opens the gate of the first thyristor 62 when the rectangular pulse signal S3 rises, and opens the gate of the second thyristor 64 when the rectangular pulse signal falls. When the first thyristor 62 is turned on, the output voltage V of the high voltage power supply 50 is boosted by the charging coil 63 and applied to the piezoelectric element 37 . The amount of elongation of the piezoelectric element 37 is proportional to the electric charge l charged in the piezoelectric element 37,
The amount of charge charged to the piezoelectric element 37 is determined by the high voltage power supply 50.
is proportional to the output voltage V. Therefore, the amount of expansion of the piezoelectric element 37 is proportional to the output voltage V of the high voltage power supply 50.

The first thyristor 62 is connected to the fuel pressurizing chamber 2 by the plunger 9.
It is turned on after the pressurization of the fuel in the tank 0 is started and the fuel discharge port 21 communicates with the fuel outlet 23. When the first thyristor 62 is turned on and the piezoelectric element 37 expands, the fuel pressure in the pressure control chamber 39 and the fuel pressurizing chamber 20 rises rapidly, and thus fuel is injected from the fuel injection valve 25 for pilot injection. (e in Figure 3) is started. Then the second
When the thyristor 64 is turned on, the electric charge stored in the piezoelectric element 37 is discharged through the discharge coil 65, so that the piezoelectric element 37 contracts. When the piezoelectric element 37 contracts, the volume inside the pressure control chamber 39 increases.
The fuel pressure within zero is reduced, thus completing the pilot injection. Then, the plunger 9 opens the fuel pressurizing chamber 2.
When the fuel in 0 is pressurized and the fuel pressure rises, fuel injection from the fuel injection valve 25 is started again and main injection is performed (f in FIG. 3). Next, when the spill ring 27 opens the fuel escape hole 22, the main injection is completed.

On the other hand, as described above, when the engine load increases, the output voltage V of the high voltage power supply 50 increases (C in Figure 3), and as a result, the amount of expansion of the piezoelectric element 37 increases (D in Figure 3).
. When the amount of expansion of the piezoelectric element 37 increases, the rate of increase in fuel pressure in the fuel pressurizing chamber 20 and the pressure control chamber 39 increases, so that the injection rate increases and the amount of fuel injection increases. That is, when the engine load increases and the main injection amount increases, the pilot injection amount also increases accordingly, so that the ratio of the pilot injection amount to the main injection amount is not too small regardless of the engine load. The ratio can be maintained within a certain range that is not too large.

Curve a in Figure 5 is when no pilot injection is performed, curve C is when the ratio of pilot injection amount to main injection amount is too small, curve d is when the ratio of pilot injection amount to main injection amount is too large. shows a case where the ratio of the pilot injection amount to the main injection amount is maintained within a certain range as in the present invention. It can be seen from FIG. 5 that in the case of the present invention, the pressure rise is gradual and the maximum combustion pressure is low, so that the generation of noise and NO2 can be suppressed.

〔Effect of the invention〕

Since the ratio of the pilot injection amount to the main injection amount can be maintained within an optimal constant range regardless of the engine load, combustion noise and generation of NOx can be suppressed. Furthermore, since the injection rate is increased in response to an increase in the engine load, the injection time does not become very long, so pilot injection and main injection can be started at optimal timings.

[Brief explanation of the drawing]

Figure 1 is a block circuit diagram for injection control, Figure 2 is a side sectional view of the injection pump, Figure 3 is a time chart for injection control, Figure 4 is a diagram showing the output voltage of the high voltage power supply, and Figure 4 is a diagram showing the output voltage of the high voltage power supply. 5
The figure is a diagram showing cylinder internal pressure. 42... Reference signal generator, 43... Load sensor, 4
5... Control circuit, 60... Drive circuit. □High load 11111 Low load 3rd cause Question 5

Claims (1)

[Claims] It is equipped with a fuel pressurizing chamber pressurized by a plunger and a piezoelectric element for increasing the fuel pressure in the fuel pressurizing chamber, and as the amount of expansion of the piezoelectric element increases, the fuel pressure in the fuel pressurizing chamber increases. A diesel engine with an increased rate of rise and in which fuel in the fuel pressurizing chamber is injected from a fuel injection valve is equipped with a supply charge amount control device that controls the amount of charge supplied to a piezoelectric element in accordance with engine load. A pilot injection control device for a diesel engine that increases the amount of electric charge supplied to the piezoelectric element in response to an increase in engine load during pilot injection, thereby increasing the amount of expansion of the piezoelectric element.