JP3094671B2 - Fuel injection timing control system for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an apparatus for feedback-controlling the fuel injection timing of a diesel engine.

[0002]

2. Description of the Related Art As a fuel injection device for a diesel engine, there is a distribution type fuel injection pump in which fuel injection timing is electronically controlled (Japanese Patent Application Laid-Open No. 55-46036,
reference).

This distribution type injection pump is provided with a low pressure feed pump and a high pressure plunger pump which rotate in synchronization with the engine rotation, and a timer piston for adjusting the fuel injection timing of the plunger pump. The fuel injection timing is controlled according to the engine speed by displacing according to the fuel pressure discharged from the pump and adjusting the compression start timing of the plunger pump via the cam.

[0004]

[SUMMARY OF THE INVENTION However, light fuel instead of normal fuel, the viscosity of the fuel is changed by fueling improper fuel, to vary the leakage amount of the fuel in the feed pump by the fuel viscosity, the engine The discharge pressure of the feed pump for the same rotation changes, and the timer piston deviates from the target position.

[0005] In this case, the past, a sensor for detecting the position of the timer piston, the duty control valve for opening and closing the hydraulic passage leading to the timer piston by the driving pulses provided, so as to the timer piston position is equal to the target position Monogaa Runode, this shall be feedback control
May be applied even when the viscosity of the fuel changes.
Can be

However, even if the position of the timer piston is feedback-controlled to maintain the timer piston position at the target value, the amount of fuel leaking during the compression stroke of the plunger pump also fluctuates due to the change in the viscosity of the fuel. There is a problem that the timing at which the fuel discharge pressure of the pump rises changes, and eventually the injection timing at which fuel is injected from the injection nozzle to each cylinder is shifted.

An object of the present invention is to pay attention to the above problems, correct a target fuel injection timing according to the fuel used, and always accurately control the optimum fuel injection timing according to the operating state. .

[0008]

SUMMARY OF THE INVENTION The present invention provides a low-pressure feed pump and a high-pressure plunger pump that operate in synchronization with engine rotation and adjusts the fuel injection timing of the high-pressure plunger pump based on the fuel pressure discharged from the low-pressure feed pump. in a diesel engine and a timer piston which, as shown in FIG. 1, corresponding to a viscosity of fuel used
Delay in the rise of the fuel discharge pressure of the plunger pump
The target timer piston position that contains that portion of the fuel used viscosity
A means 7 set each time a control mechanism 1 for adjusting the fuel pressure acting on the timer piston, a means 2 for detecting a timer piston position, closer to the timer piston to the target timer over piston position based on the detection value The means 3 for calculating the control amount of the control mechanism 1 as described above, the means 4 for setting a specified value for specifying the fuel to be used based on the magnitude of the basic control amount for the target timer piston position, and the calculated control amount Means 5 for determining the viscosity of the fuel to be used by comparing it with a prescribed value, and based on the determined viscosity of the fuel.
Setting of the target timer piston position setting means 7
Means 6 for switching the value .

A diesel engine having a low-pressure feed pump and a high-pressure plunger pump operating in synchronization with engine rotation, and a timer piston for adjusting fuel injection timing of the high-pressure plunger pump based on fuel pressure discharged from the low-pressure feed pump. In the reference fuel
Of the fuel discharge pressure of the plunger pump corresponding to the viscosity of
A means 11 for setting a basic timer piston position including a rise delay, a control mechanism 1 for adjusting the fuel pressure acting on the timer piston, a means 2 for detecting the timer piston position, and a timer piston based on the detected value. the a means 3 for calculating a control amount of the control mechanism 1 as close to the target timer over piston position, and means 8 for defining the size of the basic control amount for the basic data <br/> timer over piston position, wherein The calculated control amount is compared with the specified value, and a correction coefficient corresponding to a difference from the viscosity of the reference fuel is obtained .
And the rise in the fuel discharge pressure of the plunger pump
Means 9 for calculating a correction coefficient including a rising delay, and means 10 for correcting the basic timer piston position to a target timer piston position in accordance with the correction coefficient.

[0010]

In the first aspect, the fuel pressure acting on the timer piston is adjusted via the control mechanism 1 so that the actual timer piston position becomes the target timer piston position.

In this case, if the viscosity of the fuel changes, the leak amount of the feed pump changes, and the fuel pressure discharged from the feed pump changes accordingly. The acting fuel pressure changes. For this reason, the control mechanism 1 corrects the control amount based on the detection position of the timer piston, and moves the timer piston closer to the target timer piston position.

When the viscosity of the fuel changes, the control amount for the same timer piston position relatively changes. By comparing this control amount with a specified value of the control amount set based on the relationship with the basic fuel, the viscosity of the fuel, that is, the type of the fuel (eg, light fuel or heavy fuel) is specified. Can be.

Since the change in the viscosity of the fuel also affects the amount of leakage in the plunger pump, the fuel injection timing changes even if the timer piston is at the target timer piston position. In order to eliminate the deviation of the fuel injection timing, the viscosity of the used fuel is determined based on the control amount of the control mechanism 1, and in anticipation of the amount of fuel leaking in the compression stroke of the plunger pump, the target timer piston corresponding to the viscosity of the used fuel is determined. By setting the position, even when dissimilar fuel is supplied, the timing at which the fuel discharge pressure of the plunger pump rises can be appropriately maintained, and the fuel injection timing can be appropriately maintained.

In the second invention, the control amount of the control mechanism 1 is compared with a specified value to determine a correction coefficient corresponding to the viscosity of the fuel, and the basic injection timing is corrected by the correction coefficient.

By controlling the position of the timer piston on the basis of the corrected target injection timing, the fuel injection timing can be appropriately maintained even for heterogeneous fuels.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 3, a low-pressure feed pump 13 constituting the distribution type fuel injection pump 11 is driven by a drive shaft 12 in synchronization with engine rotation, and fuel sucked from a tank 40 is supplied to a pump inside a pump housing. The fuel is supplied to the chamber 15, and the fuel in the pump chamber 15 is sent to the high-pressure plunger pump 26 through the suction port 16.

Plunger 1 of high-pressure plunger pump 26
Reference numeral 8 denotes a fixed cam disk 19, which is driven to rotate by the drive shaft 12 via a joint 14.

The cam disk 19 is constantly pressed to the left in the figure by the urging force of the spring 21. The cam disk 19 has the same number of face cams 20 as the number of cylinders of the engine.
And the face cam 2 provided on the roller ring 22
It rotates over the same number of rollers 23 as zero.

As a result, the plunger 18 reciprocates in the axial direction by a predetermined cam lift while rotating, and the fuel sucked from the suction port 16 along with the reciprocating rotation passes through the passage 28 and is supplied to each cylinder. The pressure is fed to a distribution port 24 provided, and then each delivery valve 25
And is supplied to an injection nozzle (not shown) to inject fuel into each cylinder.

The fuel injection amount at this time is adjusted by the position of a control sleeve 31 that opens and closes a cutoff port 30 formed in the plunger 18 in communication with the passage 28. The control sleeve 31 is interlocked with the accelerator via a control lever 32 and the like, and is also controlled by the operation of a governor mechanism 33 driven by the drive shaft 12, so that the fuel injection amount increases or decreases in accordance with the accelerator opening and the engine speed. Is done.

The fuel injection timing is adjusted by the rotation position of the roller ring 22, and the roller ring 22 is rotated by a timer piston 29 which moves upon receiving the fuel pressure discharged from the feed pump 13.

A pressure chamber 35 is provided at both ends of the timer piston 29.
The pressure chamber 35 communicates with the discharge side of the feed pump 13 through the pump chamber 15 and the back pressure chamber 3
6 communicates with the suction side of the feed pump 13.

When the pressure in the pressure chamber 35 rises, the timer piston 29 moves against the spring 39 and moves the roller ring 22 to advance the compression timing (injection timing) of the plunger pump 26.

The pressure chamber 35 of the timer piston 29 serves as a pressure control mechanism for adjusting the position of the timer piston 29.
A duty control valve 40 is provided in the middle of a passage 37 that communicates with the back pressure chamber 36. The opening of the control valve 40 decreases as the duty ratio of the drive pulse decreases, and the amount of relief to the low pressure side is reduced to move the timer piston 29 to the advance side. Conversely, the opening increases as the duty ratio increases. It increases and moves the timer piston 29 to the retard side.

The control unit 41 receives the detection signals from the pump rotation speed sensor 42 and the sensor 43 for detecting the position of the timer piston 29, and changes the duty ratio of the drive pulse sent to the control valve 40 to 0. 10
By controlling between 0%, the timer piston 29
Is feedback-controlled to a target position corresponding to the engine speed.

By the way, the injection timing of the fuel changes according to the viscosity characteristics of the fuel used. In the case of a fuel having a low viscosity, the injection characteristics are relatively delayed due to fuel leakage. In order to prevent such fluctuations in the fuel injection timing, the control unit 4
Reference numeral 1 denotes a fuel injection timing T with respect to an engine speed during operation using, for example, JIS No. 2 heavy fuel as a reference fuel.
Table (FIG. 4) and a table of the same fuel injection timing T at the time of operation using, for example, the light fuel No. 3 (FIG. 5).
In order to specify the type of fuel used at that time from the duty ratio (control amount) of the drive pulse sent to the control valve 40 when performing feedback control of the fuel injection timing, the fuel injection timing and the basic A map (FIG. 6) is provided that defines the fuel to be used based on the relationship with the control amount.

Although the fuel pressure from the feed pump 13 controlled by the control valve 40 is supplied to the timer piston 20, the discharge pressure of the feed pump 13 relatively changes according to the viscosity of the fuel. Even if the opening degree of 40 is the same, the timer piston 20 is shifted from the target position due to the viscosity of the fuel. For this reason, the control unit 41 corrects the duty ratio of the drive pulse sent to the control valve 40 based on the detection signal of the actual position of the timer piston 20 so that the duty ratio matches the position at which the target injection timing of the timer piston 20 is obtained. Try to let them. Therefore, if the fuel viscosity changes due to the difference in the fuel, the duty ratio of the drive pulse sent to the control valve 40 changes relatively. Therefore, it is necessary to estimate the viscosity of the fuel, in other words, the type of the fuel, from the duty ratio. Can be.

In this embodiment, the type of fuel to be used is determined by comparing the duty ratio of the drive pulse sent to the control valve 40 with a specified value in a map (FIG. 6) for specifying the type of fuel. The target position of the timer piston 29 is switched by selecting a fuel injection timing table (FIG. 4 or FIG. 5) according to the type of the fuel thus set.

The control for switching the injection timing table based on the type of fuel will be described with reference to the flowchart shown in FIG.

First, in steps 1 and 2, the pump rotational speed and the position of the timer piston 29 are read, and in step 3, the engine rotational speed is calculated.

In steps 4 and 5, the injection timing corresponding to the rotation speed at that time is looked up in a table, and a basic control amount corresponding to the injection timing, that is, a specified value which defines a basic control duty is plotted. 6 is calculated by a table lookup, and this basic specified value is compared with the actual control duty.

If the control duty is smaller than the specified value, it is determined that the fuel is light, and if it is larger, it is determined that the fuel is the reference fuel. For example, in the case of a light fuel having a small viscosity, the leak amount of the feed pump 13 is large and the discharge pressure is relatively reduced, so that the pressure generated in the pressure chamber 35 for the same opening degree of the control valve is low. Therefore, based on the position detection signal of the timer piston 29 that is fed back to the control unit 41, the control duty is corrected in a direction to reduce the opening of the control valve 40, that is, the control duty is corrected to be reduced.

Therefore, by comparing the control duty with a specified value that defines the basic control duty, the viscosity of the fuel, in other words, the type of fuel can be specified.

As shown by the broken line in FIG. 6, the prescribed value of the basic duty is given a certain hysteresis on the increasing side of the duty ratio to absorb the fluctuation of the viscosity due to the fuel temperature, thereby ensuring the control stability. .

If it is determined that the fuel used is the reference fuel, the process proceeds to step 6, where the table shown in FIG. 4 is searched based on the engine speed at that time. Proceeds to step 7 and searches the table shown in FIG.

In step 8, the opening of the control valve 40 is feedback-controlled to control the position of the timer piston 29 so that the target fuel injection timing can be obtained based on one of the tables.

By switching the injection timing table according to the type of fuel used in this way, the deviation of the fuel injection timing due to the fuel leak in the plunger pump 26 is corrected.

In the conventional apparatus in which only the position of the timer piston 29 is feedback-controlled, the timer piston 2
Even if the timing at which the plunger 18 reciprocates via the valve 9 is maintained at the target value, the amount of fuel leaking during the compression stroke of the plunger 18 varies due to the difference in the viscosity of the fuel.
The rise time of the fuel discharge pressure guided from the plunger pump 26 to each delivery valve 25 fluctuates, causing a shift in the timing at which fuel is injected from an injection nozzle (not shown) to each cylinder through each delivery valve 25.

In this embodiment, by changing the target position of the timer piston 29 in accordance with the type of the fuel used, the difference in the fuel injection timing depending on the viscosity of the fuel is corrected, and the proper fuel injection is always performed. Time can be maintained.

Next, another embodiment shown in FIGS. 8 to 10 will be described. This is because the control unit 41 calculates the viscosity of the fuel to be used from the duty ratio of the driving pulse sent to the control valve 40, and sets the viscosity in advance. Instead of switching from the plurality of fuel injection timings set, the target fuel injection timing is corrected according to the viscosity of the fuel, and the target position of the timer piston 29 is gradually changed.

In this case, the control unit 41
Table (FIG. 4) of the injection timing T when the reference fuel is used, and the difference x between the duty at the time of operation when the reference fuel is used and the duty with respect to the currently used fuel when the feedback control is performed based on this table. And a table (FIG. 9) for calculating a correction coefficient K for correcting the injection timing T based on the difference x.

The operation of correcting the target fuel injection timing corresponding to the viscosity of the fuel will be described with reference to the flowchart shown in FIG.

First, at step 1, the pump speed is read, at step 2, the position of the timer piston 29 is read, and at step 3, the engine speed is calculated.

In step 9, the fuel injection timing corresponding to the engine speed is searched based on the characteristics shown in FIG. 4, and the control duty of the control valve 40 controlled in accordance with the search is obtained.

In step 10, the difference x between the actual control duty for the currently used fuel and a specified value that defines the basic duty during operation using the reference fuel is calculated according to the map shown in FIG. This difference x changes according to the viscosity of the fuel.

In step 11, based on the difference x, FIG.
The correction coefficient K is obtained from the table of FIG. The correction coefficient k changes in proportion to the duty difference x,
In step 12, the final fuel injection timing is calculated by a formula of T × K.

As described above, in this embodiment, the target position of the timer piston 29 can be finely controlled in accordance with the viscosity of the fuel. Without being affected
The fuel injection timing can be properly maintained.

[0049]

As described above, the first invention uses
The fuel discharge of the plunger pump according to the viscosity of the fuel
Target timer piston position including pressure rise delay
A means is provided in advance to set the unit for each viscosity of the fuel used.
In this case, the pressure of the fuel discharged from the feed pump is adjusted by a control mechanism, the position of the timer piston is feedback-controlled by the adjusted fuel pressure, and the viscosity of the fuel used is determined based on the control amount at this time. /> , It corresponds to the determined viscosity of the fuel.
By switching the set value of the setting means, even when dissimilar fuel is supplied, the timing at which the fuel discharge pressure of the plunger pump rises is appropriately maintained, and fuel is supplied to each cylinder.
The actual firing timing to be injected can be appropriately maintained.

Further, the second invention relates to the viscosity of the reference fuel.
In response, the rise in the fuel discharge pressure of the plunger pump is delayed.
A means to set the basic timer piston position including minute
It is provided in advance, in this case, the control amount of the control mechanism and the regulation
Compared with the reference value, repair according to the difference from the viscosity of the reference fuel
It is a positive coefficient and the fuel discharge pressure of the plunger pump rises.
Calculate the correction coefficient including the rise delay and calculate the correction coefficient.
Correct the basic timer piston position according to the number
By setting the target timer piston position ,
Regardless of the degree of the viscosity, the timing at which the fuel discharge pressure of the plunger pump rises can be appropriately maintained, and the actual injection timing can be appropriately maintained.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a diagram corresponding to claims.

FIG. 3 is a cross-sectional view of the fuel injection pump showing the embodiment.

FIG. 4 is a table of injection timing when a reference fuel is used.

FIG. 5 is a table of injection timing when light fuel is used.

FIG. 6 is a map for determining the type of fuel.

FIG. 7 is a flowchart showing control contents.

FIG. 8 is a map for obtaining a difference x in a duty ratio with respect to when a reference fuel is used in another embodiment.

FIG. 9 is a table for calculating a correction coefficient K;

FIG. 10 is a flowchart showing the same control contents.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 timer piston control mechanism 2 timer piston position detection means 3 control amount calculation means 4 specified value of used fuel area setting means 5 used fuel viscosity determination means 6 target timer piston position switching means 7 target timer piston position setting means 8 Means for defining basic control amount 9 Means for calculating correction coefficient 10 Means for calculating target timer piston position 11 Means for setting basic timer piston position

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 395 F02D 1/00-1/18

Claims (2)

(57) [Claims] 1. A diesel engine comprising: a low pressure feed pump and a high pressure plunger pump operating in synchronization with engine rotation; and a timer piston for adjusting fuel injection timing of the high pressure plunger pump based on fuel pressure discharged from the low pressure feed pump. In the plunger pump fuel corresponding to the viscosity of the fuel used
Means for setting the target timer piston position including the delay in the rise of the discharge pressure for each viscosity of the fuel used; a control mechanism for adjusting the fuel pressure acting on the timer piston; means for detecting the timer piston position; Set the timer piston to the target timer based on the value
Means for calculating a control amount of the control mechanism so as to approach over piston position, means for setting a specified value that identifies the use fuel from the size of the basic control amount to the target timer piston position, the calculated control amount Means for determining the viscosity of the fuel to be used by comparing the target timer with the specified value; and the target timer based on the determined viscosity of the fuel.
Means for switching the set value of the piston position setting means, the fuel injection timing control apparatus for a diesel engine. 2. A diesel engine comprising a low-pressure feed pump and a high-pressure plunger pump operating in synchronization with engine rotation, and a timer piston for adjusting fuel injection timing of the high-pressure plunger pump based on fuel pressure discharged from the low-pressure feed pump. The fuel of the plunger pump corresponding to the viscosity of the reference fuel.
A means for setting a basic timer piston position including a rising delay in discharge pressure; a control mechanism for adjusting a fuel pressure acting on the timer piston; a means for detecting a timer piston position; and a timer piston based on the detected value. The goal timer
Comparing means for calculating a control amount of the control mechanism so as to approach over piston position, and means for defining the magnitude of the basic control amount for the basic timer over piston position, the calculated control amount and the prescribed value A correction coefficient corresponding to the difference from the reference fuel viscosity,
The rise in the fuel discharge pressure of the plunger pump
Means for calculating a correction factor including, fuel injection timing control device for a diesel engine, characterized in that a means for the target timer piston position by correcting the basic timer piston position in accordance with the correction factor.