JPH0417754A - Fuel injection control device of diesel engine - Google Patents

Abstract

PURPOSE:To compensate for errors in the manufacture and assembly of a diesel engine and aged deterioration of the engine so as to secure constantly stable fuel injection characteristics of the engine by causing the rotational phase of the cam of a fuel injection pump to advance or retreat so that the initial period of the lift of the needle of an injection nozzle coincides with a desired value. CONSTITUTION:The feed rate of fuel by a fuel injection pump 1 depends on the lift characteristic (speed of lift) of a cam but in general constant lift characteristic of the cam is not obtained in all areas. Therefore, the feed rate is increased or decreased by varying the rotational phase of the cam. When the initial period of the lift of the needle of a fuel injection nozzle 2 is detected as being longer than a desired value by a detecting means 4 and a measuring means 5, the starting time of the main lift (main injection) is advanced by enhancing the feed rate, while when the intial period is shorter the starting time is retarded by lowering the feed rate. Then a phase control means 3 causes the cam phase to advance or retreat while comparing the intial period of the lift of the fuel injection nozzle 2 to the desired value, thereby compensating for errors in the manufacture and assembly of a diesel engine or aged deterioration of the engine so as to provide constantly stable fuel injection characteristics of the engine and enhance stability of combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to improving a fuel injection control device for a diesel engine.

(Prior Art) In order to reduce combustion ignition delay in a day cell engine and achieve smooth combustion, there is a fuel control device that performs fuel injection in stages.

There are many proposals for this, including, for example, Japanese Utility Model Application Publication No. 57-25159 and Japanese Utility Model Application Publication No. 63-168272.

A plurality of springs are installed in parallel to bias the needle of the fuel injection nozzle to close, and the first spring works when the needle is in the initial lift stage, and in addition to this, the second spring works once the needle has passed the initial lift stage. By doing so, the fuel injection pressure is lifted in stages, and a large amount of main injection is performed after a small amount of initially injected fuel is ignited, resulting in a stable and smooth process with less ignition delay and therefore less vibration and noise. Ensures combustion.

(Problem to be Solved by the Invention) By the way, fuel is pumped into such a fuel injection nozzle from a fuel injection pump in synchronization with engine rotation, but - for boat fishing, this fuel delivery rate is The cam that drives the fuel injection pump is set to a predetermined characteristic based on the relationship with engine rotation.

For this reason, there may be variations due to manufacturing and assembly errors in the needle, needle holder, spring, etc. of the fuel injection nozzle, or there may be changes over time, resulting in the initial lift period, fuel pressure during main injection, etc. If it fluctuates from that point, the characteristics of the staged fuel injection will become unstable, and the fuel efficiency and exhaust composition will become worse than the designed target values.

However, these measures have not been considered in the past, and combustion variations have been dealt with by thorough quality control. Of course, this is also important, but
There are naturally limits to ensuring even higher quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection control device for a diesel engine that can compensate for such manufacturing and assembly errors and changes over time, and ensure stable fuel injection characteristics at all times.

(Means for Solving the Problems) As shown in FIG. 1, the present invention includes a fuel injection pump 1 that is driven by a cam that rotates in synchronization with an engine to pump high-pressure fuel, and a fuel injection pump 1 that pumps high-pressure fuel according to the pressure of the pumped fuel. A fuel injection control device for a diesel engine comprising a fuel injection nozzle 2 that injects fuel in multiple stages by lifting a needle in stages, comprising: a phase adjustment means 3 that varies the rotational phase of a cam of the fuel injection pump 1; means 4 for detecting the lift amount of the needle of the injection nozzle; means 5 for measuring the initial lift period of the needle; and control for advancing or slowing the rotational phase of the cam so that the initial lift period of the needle matches a target value. means 6.

(Function) The fuel delivery rate by the fuel injection pump depends on the lift characteristics (lift speed) of the cam, but normally the lift characteristics are not constant in all regions.

Therefore, when the rotational phase of the cam is changed, the oil feed rate also increases or decreases.

When the initial lift period of the fuel injection nozzle is longer than the target value, the main lift (main injection) start time is brought forward by increasing the oil feed rate, and when it is short, the main lift start time is brought forward by increasing the oil feed rate. is delayed.

Therefore, by advancing or retarding the cam phase of the fuel injection pump while comparing the detected initial lift period of the fuel injection nozzle with the target value, it is possible to always compensate for the predetermined fuel injection characteristics and stabilize combustion. You can improve your sexuality.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, an example of the fuel injection pump 10 is shown in FIG.
769), the plunger 12 moves up and down as the cam 11 rotates, and the fuel in the pressurizing chamber 13 is force-fed to the fuel injection nozzle 20 via the fuel valve 14.

A control sleeve 15 is attached around the 1 langier 12, and the position of this sleeve 15 determines when to start pumping fuel. The sleeve 15 is a fuel chamber 16 into which fuel is fed.
The opening of the passage 17 provided in the plunger 12 that communicates between the pressurizing chamber 13 and the fuel chamber side is opened and closed, and in the process of the plunger 12 rising, the opening of the passage 17 is closed by the lower end of the sleeve 15. Then, communication with the fuel chamber 16 is cut off, and the pressure in the pressurizing chamber 13 begins to increase.

Also, as the plunger 12 rises, the boat 17. which branches from the passage 17. When the port a communicates with the port 15a provided in the middle of the sleeve 15, the pressurizing chamber 13 again communicates with the fuel chamber 16, and the pressure feeding of fuel is completed.

By moving the position of the sleeve 15 up and down using the position control mechanism 18, the time to start pumping fuel can be advanced,
It can be delayed.

Further, since the branch boat 17a is opened as an inclined groove around the plunger, by changing the rotational position of the plunger 12 about the axis t by the rotation control mechanism 19, the timing of communication with the port 15a is changed, and the timing of communication with the port 15a is changed. The end timing of pumping, that is, the amount of fuel injection can be changed.

Next, an example of the fuel injection nozzle 20 is shown in FIG. 3 (see Japanese Patent Application No. 1-190460).
A needle 22 is arranged inside the needle 22.
is seated on the seat portion 25 by first and second springs 23,24.

When the pressure applied to the needle 22 increases to a predetermined value or more due to the fuel pressure from the fuel injection pump IO introduced into the fuel pressure chamber 27, the first spring 23 is compressed via the bushing rod 26, and the needle 22 is is lifted upward by a certain amount.

This is the initial injection, and the fuel pressure increases to the second spring 2.
This state is maintained until the pressure exceeds the set pressure in step 4. Next, the second spring 24 is inserted through the spring seat 28.
While compressing the fuel, the needle 22 lifts significantly, and main injection that supplies a large amount of fuel begins.

In this way, staged fuel injection is performed in which a small amount of fuel is injected during the initial lift (initial injection) period, and then a large amount of fuel is injected during the main lift (main injection) period.

In order to measure the actual lift amount of the needle 22, a needle lift sensor 29 is attached to the upper part of the nozzle holder 21. For example, a magnetostrictive sensor is used as the lift sensor 29, and when the bushing rod 26, which is made of a magnetic material and is interlocked with the needle 22, comes close to the magnetic field generated by the high-frequency coil of the measuring section, a vortex is generated inside the magnetic material. The amount of lift of the needle 22 is detected from the change in inductance of the high-frequency coil that occurs in response to changes in current or magnetic permeability.

Next, FIGS. 4(A) and 4(B) show the fuel injection pump 10.
An example of a phase adjustment mechanism 30 (see Japanese Unexamined Patent Publication No. 58-48719) that advances or retards the cam phase is shown.

This is the pump shaft (camshaft) 10a of the fuel injection pump 1o.
and the rotating body 31 to which the engine rotation is transmitted, and variably adjusts the transmission phase of the engine rotation to the pump shaft 10m.

Shaft portion 32 of rotary disk 33 coaxially coupled to pump shaft 10a
A rotating body 31 is supported so as to be freely rotatable therewith.

In order to impart a phase difference to the rotation transmitted from the rotary body 31 to the rotary disk 33 as necessary, the rotary disk 33 and the rotary body 31 are connected to each other so as to be relatively displaceable in the rotational (circumferential) direction. First, a pair of circular holes 33a are bored in the rotary disk 33 at positions equidistant from its center of rotation, and the first eccentric cam 35 is inserted into these holes. Further, a second eccentric cam 36 is inserted into the circular hole 35a provided in the eccentric cam 35.

The eccentric bin 36b of the second eccentric cam 36 is connected to the rotating body 3.
The eccentric pin 35b of the first eccentric cam 35 penetrates into the piston 37a housed in the cylinder 37 from the side.
Connect to.

The cylinder 37 is integrally attached to the rotary disk 33 in the radial direction of the shaft portion 32, and pressure oil supplied through the inner peripheral passage #r32a of the shaft portion 32 is guided to the oil chamber 37b. The piston 37a receives this supply pressure and the return spring 37
Move to a position where c is in balance.

Therefore, depending on the position of the piston 37a, the eccentric bin 3
5b rotates the first eccentric cam 35, thereby displacing the second eccentric cam 36 in the circumferential direction with respect to the rotary disk 33, and the rotary body 31 and the rotary disk are connected via the eccentric pin 36b. 33 to change the phase of the rotation direction.

As a result, the rotational phase of the pump shaft 10a of the fuel injection pump 10, that is, the cam 11, changes with respect to the engine rotation,
The fuel delivery rate changes.

Oil pump 39 guided to oil chamber 37b of cylinder 37
The oil pressure in the cylinder changes depending on the opening degree of the control valve 38, and as the control valve opening degree increases, the oil pressure decreases.

In the present invention, the key point is to control the rotational phase of the cam 11 of the fuel injection pump 1o so that the initial lift period of the fuel injection nozzle 2o matches a preset target value, and this is the fifth point. It is controlled by a controller 5o shown in the figure.

By correctly setting the initial lift period of the fuel injection nozzle 2o to the target value, stable combustion without ignition delay can be achieved, but if the initial lift period is too long or short, the combustion becomes more unstable. As a result, fuel efficiency and exhaust composition deteriorate.

To compensate for variations in the initial lift period, the invention:
The initial lift period is set to a predetermined value by changing the fuel feeding rate from the fuel injection pump 10, increasing the oil feeding rate when the initial lift period is longer than the target, and lowering the oil feeding rate when it is shorter than the target. It is designed to converge.

Therefore, in order to adjust the oil feed rate of the fuel injection pump 10,
The rotational phase of the cam 11 is controlled by the controller 50 via the phase control mechanism 30.

The controller 50 includes a CPU as a calculation section and an RO as a storage section.
It is composed of a microcomputer, etc., consisting of M, RAM, and an input/output part Ilo.

Detection signals from the engine speed sensor 51, accelerator opening sensor 52, needle lift sensor 29, etc. are input to the controller 50, and based on these, the controller 50 appropriately controls the fuel injection timing, fuel injection amount, and cam phase. , a position control mechanism 18 and a plunger 12 for the sleeve 15, respectively.
rotation control mechanism 19, cam phase adjustment mechanism 30 (control valve 3
8).

The control operation in the controller 50 will now be described with reference to the flowchart in FIG.

First, in step 510, the engine speed Ne, the accelerator opening degree A
ce, needle lift amount Vn, then basic fuel injection amount Q, basic fuel injection timing IT, basic cam phase DQ,
A basic counter value Co is determined by table lookup (step 520).

As shown in Figure 7, the basic fuel injection IQ is the engine speed N
Based on e and the accelerator opening Ace, the basic fuel injection timing IT is predetermined to have the optimum characteristics, as shown in FIG. 8, also based on the rotational speed Ne and the accelerator opening Ace.

The basic cam phase DQ is the engine speed Ne and the accelerator opening A.
cc is set to the characteristics shown in FIG. 9, which controls the fuel feed rate (injection rate), and as shown in FIG. 11, the cam 11 of the fuel injection pump 10 Since the cam speed (lift speed) differs depending on the phase of the cam, the fuel delivery rate can be changed by changing the cam phase.

Fuel pumping period from the fuel injection pump 10 (sleeve 15
Even if the period from when the communication between the pressurizing chamber 13 and the fuel chamber 16 is cut off to when the communication is resumed is the same, if the cam phase is advanced, the region where the cam speed is high can be utilized, so the oil feed rate can be reduced. On the other hand, if the angle is retarded, the oil delivery rate will be lowered.

The basic fuel oil supply rate is set to increase as the accelerator opening degree Ace becomes smaller, and therefore, the advance value of the cam phase is increased in the low accelerator opening area.

Next, the initial lift period of the fuel injection nozzle 20 is set by the basic counter setting value CO, which corresponds to the initial lift (pre-lift) period of the needle 22, and also depends on the rotation speed Ne and the accelerator opening. It is predetermined based on the degree Acc as shown in FIG.

Basically, the initial lift period is set to be long in the region where the accelerator opening Ace is small, and the initial lift period is shortened in the region where the accelerator opening is large. Achieve output.

After reading each of these basic values by table lookup, in step 530, the output value Vn of the second lift sensor 29 is set within a predetermined range representing the initial lift (prelift) period, that is, VL and VL2. Determine whether it is between.

As shown in FIG. 12 (A>), this is the value corresponding to the initial lift from when the needle 22 or the first spring 23 is compressed to when the second spring 24 starts being compressed. When the lift amount of 22 is within this range,
It is determined whether it is the initial lift period.

In addition, Fig. 12 (B) shows that depending on the operating conditions, the
Since the lift characteristic of 2 may end with only a pre-lift in this way, in such a case, the period during which Vn is greater than VL is determined.

While the needle lift is vL1≦V n <V L 2, the counter continues counting (step 540), and when Vn becomes larger than VL2, the counting is stopped and the counter set value Co and this count value C are By determining the difference between , it is determined whether the initial lift period matches the target value.

That is, after calculating the correction value as ΔC=Co−C in step 550, in step 580, the cam phase correction amount ΔDQ is calculated based on this correction value ΔC by table lookup.

Figure 13 shows the cam phase correction characteristics. If ΔC=O, the initial lift matches the set target value, so the cam phase correction amount is zero, that is, the amount of correction relative to the basic cam phase DQ. The correction amount is zero, but if it is not, the cam phase correction amount ΔD is determined from the value of ΔC according to FIG.
Find Q.

When the initial lift period is longer than the target value, ΔC takes a negative value and ΔDQ takes a positive value, and when the initial lift period is short, ΔDQ takes a negative value.

Therefore, as in step 570, cam phase DQ
=DQ+ΔDQ is corrected by advancing the basic cam phase DQ when the initial lift period is longer than the target value, and by retarding it when it is shorter.

As shown in FIG. 11 described above, when the force phase is advanced, the fuel feed rate increases due to fuel pressure in the region where the cam speed is high, and when the force phase is retarded, the fuel feed rate decreases.

Therefore, when the initial lift period is long and the start of the main lift is late, the cam phase is advanced to increase the fuel delivery rate, increase the amount of fuel pumped per unit time, and increase the flow rate of the needle 22. The transition to main lift (main injection) can be accelerated.

On the other hand, when the initial lift period is short and the main lift starts too early, the cam phase is corrected to the retarded side, lowering the fuel delivery rate, reducing the amount of fuel pumped, and delaying the start of main injection. It can be delayed until the target value is reached.

In this way, while measuring the actual initial lift period, it is corrected by controlling the cam phase so that it matches the target period determined by the operating condition. Sometimes there is
Alternatively, even if the initial lift period changes due to changes over time, etc., it is possible to always perform appropriate initial lift injection.

Note that in step 570, along with this cam phase DQ,
The already calculated basic injection amount Q and basic injection timing IT are stored in a predetermined address in the memory, and a series of control routines is completed.

Of course, this control operation is repeatedly performed in synchronization with the engine rotation, and is updated with new data each time.Based on this, the controller 50 controls the rotation of the position control mechanism 18 of the sleeve 15 and the plunger 12. The operation of the control mechanism 19 and the cam phase adjustment mechanism 30 is controlled.

Note that since the actual fuel injection timing can be detected from the output of the needle lift sensor 29, by controlling the feed pump of the position adjustment mechanism 18 based on this, it is also possible to accurately match the fuel injection timing with the target value. becomes.

(Effects of the Invention) As described above, according to the present invention, fluctuations in the initial lift period of the fuel injection nozzle are constantly adjusted to the target value by adjusting the force l and phase of the fuel injection pump and changing the fuel feed rate. As a result, even if there are manufacturing or assembly errors or changes over time in the fuel injection nozzle, initial injection can be performed with an appropriate initial lift period, resulting in stable combustion without ignition delay. This makes it possible to maintain good fuel efficiency and exhaust composition.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the present invention, Fig. 2 is a sectional view of a fuel injection pump showing an embodiment of the invention, Fig. 3 is a sectional view of a fuel injection nozzle, and Fig. 4 (A>, (B) is A sectional view and a front view of the main parts of the cam phase adjustment iWI, Figure 5 is a block diagram of the controller, Figure 6 is a flowchart of the control operation, and Figures 7 to 10 are the basic fuel injection amount and basic fuel injection timing, respectively. , control characteristic diagram of basic cam phase and basic counter setting value,
Figure 11 is a cam lift characteristic diagram, Figure 12 (A), (B)
13 is a needle lift characteristic diagram, and FIG. 13 is a control characteristic diagram of a cam phase correction value. DESCRIPTION OF SYMBOLS 10... Fuel injection pump, 18... Sleeve position control mechanism, 19... Plunger rotation control mechanism, 20...
・Fuel injection nozzle, 22...needle, 23.24・
...Spring, 30...Cam phase control mechanism, 50.
··controller. Figure 2 Fuel injection sleeve position! Control machine Keyaki plunge fuel injection

Claims (1)

[Claims] 1. A diesel engine equipped with a fuel injection pump that is driven by a cam that rotates in synchronization with the engine to pump high-pressure fuel, and an injection nozzle that injects fuel in multiple stages by lifting the needle in stages according to the pressure of the pumped fuel. In the fuel injection control device, a phase adjusting means for varying the rotational phase of a cam of the fuel injection pump, a means for detecting a lift amount of a needle of the injection nozzle, a means for measuring an initial lift period of the needle, and a needle A fuel injection control device for a diesel engine, comprising control means for advancing or slowing the rotational phase of the cam so that an initial lift period of the cam coincides with a target value.