JP2001355492A - Fuel injection timing control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a combustion deterioration under an idling state at an extremely low temperature by removing an influence to an injection timing accompanying with a feed-back control of an idling rotation speed while stabilizing the idling rotation speed by carrying out the feed-back control of the idling rotation speed even under the idling state at the extremely low temperature. SOLUTION: A control means 51 carries out a feed-back control by increasing/decreasing a fuel injection amount such that an idling rotation speed becomes a target value. An operation means 52 operates a target injection timing corresponding to the fuel injection amount after the increase/decrease and a control means 53 controls an injection timing adjustment means 54 so as to become this target injection timing. In this case, a judgment means 55 judges whether or not it is under idling state at an extremely low temperature. A fixing means 56 fixes the target injection timing under the idling state at the extremely low temperature based on this judgment result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection timing control device for a diesel engine.

[0002]

2. Description of the Related Art It is known that feedback control is performed by increasing or decreasing a fuel injection amount so that an idle rotation speed becomes a target value (see Japanese Patent Application Laid-Open No. 8-326592).

[0003]

However, especially in the idle state immediately after the engine is started at extremely low temperatures, the engine speed changes suddenly, possibly due to misfiring due to the failure of normal combustion. It has been found that the fuel injection amount changes suddenly due to the feedback control of the speed, and at this time, the injection timing also changes at the same time, thereby further deteriorating the combustion state.

[0004] To explain this, in the conventional apparatus, the basic injection timing is given by a map value using the fuel injection amount and the engine rotation speed as parameters. Therefore, when the fuel injection amount is increased or decreased by the feedback control of the idle rotation speed due to unstable combustion during the idling operation, the basic injection timing with reference to the map is changed under the influence of the increase or decrease of the fuel injection amount. . In this case, at the moment when the combustion is shifted from the deteriorated state to the normal combustion, the fuel injection amount moves to the decrease side, and accordingly, the injection timing moves to the retard side. Therefore, at extremely low temperatures where the probability of misfiring increases, it is conceivable that the chances of a sudden change in the idle rotation speed increase, and at this time, the injection timing also largely moves to the advance side or the retard side, and the injection timing shifts to the retard side. When moving a large distance, the combustion worsens. This is schematically shown in FIG. It can be seen that the feedback control of the idling rotational speed works to promote the change width of the injection timing.

[0005] In order to avoid such a large fluctuation of the injection timing, it is conceivable to stop the feedback control of the idling rotational speed, but at that time, the idling rotational speed cannot be stabilized.

Accordingly, the present invention provides feedback control of the idle rotation speed by performing feedback control of the idle rotation speed and stabilizing the idle rotation speed while fixing the target injection timing even in an idle state at a very low temperature. It is an object of the present invention to eliminate the influence on the injection timing due to the above and prevent a change in combustion in an idle state at a very low temperature.

[0007]

According to a first aspect of the present invention, as shown in FIG. 19, a means 51 for performing feedback control by increasing or decreasing a fuel injection amount so that an idle rotation speed becomes a target value, Diesel comprising means 52 for calculating a target injection timing according to the increased / decreased fuel injection amount, and means 53 for controlling an injection timing adjusting means (for example, a timer mechanism of a fuel injection pump) 54 to achieve the target injection timing. The engine control device includes means 55 for determining whether the engine is in an idle state at a very low temperature and means 56 for fixing the target injection timing in the idle state at a very low temperature based on the determination result.

In the second invention, the fixed injection timing in the first invention is an injection timing when a predetermined clamp permission time has elapsed after the start.

According to a third aspect of the present invention, in the second aspect of the invention, when a means for performing feedback control is provided so that the actual injection timing becomes the target injection timing, the feedback control of the injection timing is performed when the target injection timing is fixed. To stop.

According to a fourth aspect of the present invention, the fixing of the target injection timing is released when one of the following conditions is satisfied in the second or third aspect of the invention.

A) when the engine is no longer in an idle state; b) when a state in which misfiring is unlikely to occur (when the engine water temperature exceeds a predetermined value or when the elapsed time after the engine complete explosion exceeds a predetermined value); c) When exceeding a predetermined engine rotation range, in the fifth invention, when the target injection timing is set even in accordance with the engine water temperature in the fourth invention, the engine water temperature is released after the fixing of the target injection timing is released. Slowly approach the target injection timing according to.

In a sixth aspect of the present invention, in the fifth aspect, the processing for slowly approaching is a ramp processing.

[0013]

According to the first and second aspects of the present invention, the engine speed rapidly changes due to unstable combustion in the idle state at a very low temperature, and the feedback control of the idle speed in response to the sudden change. Therefore, even if the fuel injection amount increases or decreases, the target injection timing does not change in accordance with the increased or decreased fuel injection amount, so that excessive combustion deterioration can be prevented.

Some engines having an electronically controlled fuel injection pump have means for performing feedback control of the injection timing so that the actual injection timing becomes the target injection timing in an idle state. In this method, when the target injection timing changes, the actual injection timing attempts to follow the target by feedback control of the injection timing. However, when the change of the target injection timing is continuous, the control of the control is rather performed by the feedback control of the injection timing. It also impairs stability.
On the other hand, according to the third aspect, the feedback control of the injection timing is also stopped when the target injection timing is fixed, so that the stability of the control is not hindered.

If the target injection timing is fixed until the engine is no longer in the idle state, the injection timing cannot be given according to the accelerator request. However, according to the fourth aspect, the injection timing can be adjusted to the accelerator request.

Since it is not necessary to fix the target injection timing when a misfire is unlikely to occur even in the idle state, unnecessary control is not required according to the fourth aspect of the present invention.

According to the fourth aspect of the present invention, unnecessary control is not performed since the rotation becomes stable when the engine rotation speed becomes higher than the predetermined rotation range and the target injection timing does not need to be fixed. . In some cases, the idle rotation speed is increased in order to enhance the heating performance. In this case, in the fourth invention, the injection timing for improving the heating performance can be set by releasing the fixation of the target injection timing. it can.

If the target injection timing is set according to the engine water temperature, the target injection timing changes to the retard side as the water temperature rises, so that a step in the injection timing occurs when the target injection timing is released, Although the combustion state of the engine changes suddenly, according to the fifth and sixth aspects, such a sudden change in the combustion state can be prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an electronically controlled distribution type fuel injection pump (face cam pumping system) which is well known.

First, fuel is sucked from an inlet (not shown) of the pump body by a feed pump 3 driven by a drive shaft (connected to an engine output shaft) 2, and the fuel guided to a pump chamber 5 is operated. At the same time as the lubrication of the part is performed, it is sent to the high pressure plunger pump 7 through the suction port 6.

The plunger 8 of the pump 7 is fixed to a cam disk 9 connected to the drive shaft 2, and is driven by the drive shaft 2 via the joint 2A in synchronization with the engine rotation. The cam disk 9 has the same number of face cams 10 as the number of cylinders of the engine, and reciprocates by a predetermined cam lift each time the face cam 10 gets over the rollers 12 disposed on the roller ring 11 while rotating.

When the plunger 8 reciprocates while rotating in this manner, the fuel sucked from the suction port 6 is pumped from the distribution port 13 to the injection nozzle (not shown) through the delivery valve 14 by the reciprocation. .

On the other hand, the fuel injection amount is determined by the position of the control sleeve 16 covering the cutoff port 15 formed in the plunger 8. For example, if the opening of the cut-off port 15 crosses the right end of the control sleeve 16 by moving the plunger 8 to the right side, the distribution port 1 is moved from the plunger high-pressure chamber 7A until then.
3 is released to the low-pressure pump chamber 5 through the cut-off port 15, so that the pumping to the distribution port 13 ends.

Therefore, when the control sleeve 16 is displaced to the right relative to the plunger 8, the fuel injection end timing is delayed and the fuel injection amount is increased. Conversely, when the control sleeve 16 is displaced to the left. The fuel injection end timing is advanced and the fuel injection amount is reduced.

The control sleeve 16 is supported by a ball 23 eccentrically provided at the tip of a rotor (rotary shaft) 22 of a rotary solenoid (a kind of proportional solenoid) 21. The control sleeve 16 corresponds to the rotation angle of the rotor 22 shown in FIG. The position is displaced. As also shown in FIG.
That is, the rotational movement of the rotor 22 is converted into a linear movement of the control sleeve 16 in the left-right direction.

In FIG. 3, as the clockwise rotation angle of the rotor 22 increases, the rightward movement amount of the control sleeve 16 increases (the fuel injection amount increases), so that the duty value given to the rotary solenoid 21 is increased. The rotation angle of the rotor 22 in the clockwise direction is increased in proportion to (the ON time ratio per fixed time).

The fuel injection timing is adjusted by changing the relative position between the face cam 10 and the roller 12 by the roller ring 11.

The roller ring 11 is connected via a timer slide pin 25 to a timer piston 26 which is rotatable in a rotational tangential direction of the roller ring 11. As shown in FIG. 4, the timer piston 26 slides in the cylinder 27.
The fuel pressure in the pump chamber 5 is guided to the high pressure chamber 28 on one end face of the pump chamber 5 through the passage 29, and the low pressure chamber 30 on the opposite side communicates with the suction side of the feed pump 3 to be in a pressure state lower than the atmospheric pressure. However, the timer piston 26 is pushed back by the elastic force of the spring 31.

When the fuel pressure in the pump chamber 5 rises due to the increase in the engine speed, the timer piston 30 is pushed rightward in FIG. 4, thereby rotating the roller ring 11 in the direction opposite to the rotation of the cam disk 8. , So that the injection timing is relatively advanced. Since the fuel is injected when the face cam 10 of the cam disk 9 rides on the roller 12, when the roller ring 11 is rotated in a direction opposite to the rotation direction of the cam disk 9, the timing for riding on the roller 12 of the face cam 10 Therefore, the fuel injection timing with respect to the crank angle can be advanced.

However, the fuel pressure in the pump chamber 5 is
Since the injection timing increases linearly in proportion to the engine rotation speed, the injection timing can basically be linearly advanced only in proportion to the engine rotation speed. For this reason, the timing control valve 33 provided in the bypass passage 32
When the fuel in the high-pressure chamber 28 is leaked to the low-pressure side by opening the opening, the injection timing can be delayed even at the same rotation speed. The leakage flow rate to the low pressure side is adjusted by a duty value (hereinafter referred to as TCV duty value) given to the timing control valve 33.

However, the TCV duty value is not the ON time ratio per fixed time, but the OFV per fixed time.
The F time ratio. When the TCV duty value is 100% (that is, when the timing control valve 33 is in the fully closed position), the maximum advance angle is obtained, and when the TCV duty value is 0% (when the timing control valve 33 is in the fully open position), the minimum advance angle (the leakage flow rate to the low pressure side is maximum). That is. The OFF time ratio of 100% means that the timing control valve 33 is in the non-energized state, and the timing control valve 33 is in the fully closed position in the non-energized state for fail-safe. For example, when the wiring to the timing control valve 33 is broken, the timing control valve 33 is in a fully closed state (that is, the same state as when the timing control valve 33 is not provided).

FIG. 5 is a control system diagram of the electronically controlled injection pump.

The control sleeve position sensor 38 is
As shown in FIG. 2, the rotary solenoid 21 is integrally attached to the rotor 22 and outputs a signal corresponding to the rotation angle of the rotor 22. As shown in FIG. 4, the timer piston position sensor 39 converts the displacement of the timer piston 26 into a voltage value and outputs the voltage value.

The reference pulse (Ref signal) is one pulse per rotation of the injection pump, and the scale pulse is 36 pulses per rotation of the injection pump. These pulses from the injection pump and the sensor signals of the control sleeve position sensor 38 and the timer piston position sensor 39 detect the accelerator opening sensor 36, the water temperature sensor 40, the air conditioner switch 42, and the selector position of the automatic transmission. Along with the signal from the inhibitor switch 43, an ECU (Electronic Control Unit) 35 inputs the
The CU 35 controls both the amount of driving applied to the rotary solenoid 21 and the timing control valve 33.

The control executed by the ECU 35 will be described focusing on an idle state immediately after starting. First, the fuel injection amount control is as follows (for details, see JP-A-3-3
26592). That is, the accelerator-equivalent injection amount Qdrv corresponding to the engine rotation speed and the accelerator opening is given by the map value. In addition, a starting increase injection amount Qst corresponding to the cooling water temperature and the engine rotation speed is provided as a map value for a cold start, and the starting increase is performed by adding this Qst to the accelerator-equivalent injection amount Qdrv at the start. . In idle state, cooling water temperature, battery voltage,
A target rotation speed NSET according to the air conditioner state or the like is determined in advance, and the idle correction amount Qidle is set so that the actual idle rotation speed matches this target rotation speed NSET.
Is calculated and added to the accelerator-equivalent injection amount Qdrv to perform feedback control of the idle rotation speed. The injection amount determined in this manner is the target injection amount Q
Becomes

On the other hand, a pump characteristic (a characteristic of a fuel injection amount according to a control sleeve position and an engine speed) is provided, and the target injection amount Q is converted into a target control sleeve position Uαsol using the pump characteristic. . This target value is used as the control sleeve position sensor 38.
The control sleeve movement amount is obtained by PID control by comparing the control sleeve position with the actual control sleeve position detected by, and is converted into a PWM signal and output to the rotary solenoid 21.

Next, the injection timing control is as follows (for details, see Japanese Patent Application Laid-Open No. Hei 8-112231). That is, the basic injection timing IT0 according to the engine speed and the accelerator opening is given by the map value. In addition, a water temperature correction amount ITTw corresponding to the cooling water temperature and the engine rotation speed is provided as a map value for a low water temperature, and the injection timing is advanced by adding this ITTw to the above basic injection timing IT0 at a low water temperature. Correct to the side. The injection timing determined in this way is the target injection timing ITs1.

The target injection timing ITs1 is determined by the actual injection timing IT detected by the timer piston position sensor 39.
Compared with i, the movement amount of the timer piston is obtained by PID control, and this is converted into a drive signal and output to the timing control valve 33.

The accelerator opening is actually obtained from the control lever position of the injection pump. Based on the Ref signal and the scale pulse from the injection pump, EC
The pump rotation speed is calculated in U35, and based on this pump rotation speed, the engine rotation speed (2 of the pump rotation speed) is calculated.
It goes without saying that Ne) is calculated.

The known injection amount and injection timing are controlled as described above. In the present embodiment, the injection timing is clamped (fixed) only in an idle state at a very low temperature.
This will be described with reference to FIG. 6. FIG. 6 shows changes in the water temperature and the injection timing in the idle state immediately after the start at the extremely low temperature.

In the idle state immediately after the start, the cooling water temperature Tw is extremely low, for example, -25 ° C. or less. At such extremely low temperatures, the combustion state deteriorates and misfires tend to occur, and it is attempted to suppress rotation fluctuation due to misfires. Under the influence of the feedback control of the idle rotation speed, the target injection timing fluctuates greatly to the advanced side and the retard side, and the large shift of the injection timing to the retard side further deteriorates the combustion state. In the present embodiment, the target injection timing is clamped at a timing t1 when the engine rotation speed is stabilized to some extent after the complete explosion determination, that is, at a timing t1 at which a predetermined clamp permission time has elapsed since the complete explosion determination (see the dashed line). This prevents the deterioration of the combustion state due to the influence of the feedback control of the idle speed.

Thereafter, when the water temperature Tw rises to a state where a misfire is unlikely to occur, that is, at a timing t2 when the water temperature Tw becomes a predetermined value A [° C.] Release the clamp at the timing exceeding the value).

However, as the water temperature Tw rises, the water temperature T
Since the target injection timing ITs1 calculated in accordance with w gradually changes to the retard side (see the solid line), if the characteristic is switched to the solid line simultaneously with the release of the clamp, a step occurs in the injection timing and the combustion state suddenly changes. Since it is not preferable, ramp processing is performed to smoothly connect to a solid line characteristic (see a dashed line).

The contents of this control executed by the ECU 35 will be described with reference to the following flowchart.

FIG. 7 is for calculating the target injection timing ITs1, and is executed in synchronization with a predetermined time (for example, every 10 ms). In step 1, the engine rotation speed Ne
[Rpm], the target fuel injection amount Q [mg / st], and the cooling water temperature Tw [° C.] are read.

The target fuel injection amount Q is a value calculated in another injection amount control routine (not shown). For example, the accelerator opening equivalent injection amount Qdrv corresponding to the rotation speed Ne and the accelerator opening ACC, Idle injection amount Qidl determined by battery voltage, operating condition of air conditioner, etc.
e (feedback correction amount for matching the actual rotation speed to the target idle rotation speed NSET).

In step 2, the basic injection timing IT0 [mm] is calculated from the target fuel injection amount Q and the rotational speed Ne by referring to a map having the contents shown in FIG. IT0 is a value that increases (becomes more advanced) as the target fuel injection amount Q increases. This is because even if the injection amount Q increases,
This is because, in order to make the injection end timing the same, the injection timing must be advanced as the injection amount Q increases.

Although the injection timing is treated in units of millimeters from the viewpoint of control, a value obtained by multiplying 0.244 [° / mm] is the crank angle before the compression top dead center. Therefore, the larger the value, the more the value on the advance side.

In step 3, the cooling water temperature Tw and the rotation speed N
e, a water temperature correction amount ITTw [mm] is calculated by referring to a map having the contents shown in FIG. 9, and in step 4 based on the ITTw and the basic injection timing IT0.

[0050]

## EQU1 ## The target injection timing ITs1 [mm] is calculated by the following equation: ITs1 = IT0 + ITTw.

As shown in FIG. 9, the value of ITTw is maximized at the time of idling. IT at idle speed
The value of Tw is set to the maximum value because the combustion temperature is low and the white smoke is likely to be emitted at the time of idling with a small injection amount. Further, the reason why the value of ITTw is increased as the Tw becomes lower is that it takes a longer time for the fuel to burn at a low temperature and the amount of white smoke increases accordingly, so that the fuel is better burned by the advance angle. .

FIG. 10 is for determining the clamp permission condition. In step 1, the idle switch 44
(See FIG. 5), the cooling water temperature Tw is read. In step 12, the clamp permission flag is checked. Since the clamp permission flag is 0 at the start of the engine, the process proceeds to step 13 and the subsequent steps to determine a clamp permission condition. This condition determination is performed by checking the contents of steps 13 to 15 one by one. Clamping is permitted when all of the items are satisfied, and clamping is prohibited when even one is not satisfied. That is, when (1) a predetermined clamp permission time has elapsed after the start, (2) the cooling water temperature Tw is equal to or less than a predetermined value, and (3) an idle condition is satisfied (idle switch ON), a step is performed. At 16, the clamp is permitted (clamp permission flag = 1), otherwise, the process proceeds to step 17 to prohibit the clamp (clamp permission flag = 0).

Here, the clamp permission time of <1> is a time to wait for the engine rotation speed to reach the rotation speed at which the clamping of the present embodiment may be started after the engine is started. This is because the engine speed greatly changes immediately after a cold start due to an increase in fuel. <2> is a condition for determining the extremely low water temperature, and the predetermined value is, for example, −25.
It is a value of about ° C. Since combustion is not stable at extremely low water temperature, if a misfire occurs, the rotational speed is suddenly changed during idling. The reason for <3> is that the operating condition in which the rotational speed is originally unstable during idling.

FIG. 11 is for determining the clamp release condition. In step 21, the idle switch 4
The CPU reads the signal of No. 4, the cooling water temperature Tw, and the engine rotation speed Ne, and checks the clamp permission flag in step S22. Since the clamp must be released as a prerequisite for releasing the clamp, the process proceeds to the determination of the clamp release condition after step 23 only when the clamp permission flag = 1. This condition determination is also performed by checking the contents of steps 23 to 26 one by one. When at least one of the items is satisfied, the clamp is released, and when all the items are not satisfied, the clamp is not released. That is, <4> idle condition is not satisfied (idle switch OFF), <5>
A predetermined clamping time according to the cooling water temperature Tw has elapsed; <6> the cooling water temperature Tw has exceeded a predetermined value A;
<7> When it is out of the predetermined engine speed range, the clamp is released in step 27 (clamp release flag = 1), otherwise, the process proceeds to step 28 and the clamp is not released (clamp release flag = 0).

Here, the reason why the clamp is released when the idle condition is deviated is that it is necessary to set the injection timing in accordance with the accelerator request. Fig. 1 shows the clamping time for <5>.
As shown in FIG. 2, the value becomes longer as the temperature becomes lower. Conversely, when the water temperature Tw is in the range of 0 ° C. or higher, the injection timing control of the present embodiment is not required. <6> releases the clamp when the temperature reaches a temperature at which misfire is unlikely to occur. <7> releases the clamp when the rotation speed is higher than the normal idle rotation speed. This is because if the rotation speed is high, the rotation is stabilized without performing the injection timing control of the present embodiment. Further, there are cases where the idle rotation speed is increased in order to enhance the heating performance, and in this case, it is necessary to give priority to this.

FIG. 13 is for calculating the command injection timing ITs according to the clamp permission flag and the clamp release flag set as described above.

In step 31, the target injection timing ITs1 is read. In step 32, a clamp permission flag is checked. If the clamp permission flag = 1, the value of the previous clamp permission flag is checked in step 33. When the clamp permission flag was 0 last time (that is, when the clamp permission flag is switched from 0 to 1), the process proceeds to steps 34 and 35, and the target injection timing ITs1 is changed to the clamp injection timing ITcl.
mp, and set the clamp injection timing to the command injection timing IT.
Set as s.

In this case, if the clamp permission flag is set to 1 last time, the routine proceeds to step 36, where the clamp release flag is checked. When the clamp release flag = 0, the processing of step 35 is executed. If the state of the clamp release flag does not change thereafter, the process of step 35 is repeated.

Eventually, the clamp time elapses or the water temperature Tw
Rises and the clamp release flag = 1, the process proceeds from step 36 to step 37 and thereafter, and the command injection timing ITs
Is returned to the target injection timing ITs1 at a constant speed, so-called ramp processing is performed. In other words, the command injection timing ITs is constant during the period from when the clamp permission flag = 1 to when the clamp release flag = 1, and the value at this time is when the clamp permission flag = 1 (at the start of clamping). Is the target injection timing ITs1.

At step 37, the target injection timing ITs1 is compared with ITsz which is the previous value of the command injection timing. Since ITsz is larger at the beginning when the clamp release flag = 1, the process proceeds to step 38, and a value obtained by subtracting a constant value ΔIT (positive value) from ITsz, which is the previous value of the command injection timing, is the present value of the command injection timing. ) Calculate as ITs.
By repeating the process of step 38, ITs gradually decreases. Then, when ITsz becomes ITs1 or less, the process proceeds from step 37 to step 39,
The target injection timing ITs1 is set as the command injection timing ITs. In this manner, the clamp process is set to 0 in step 40 to end the ramp process. From this clamp permission flag = 0, the process proceeds from step 32 to step 41 from the next time, and the target injection timing ITs1 becomes the command injection timing ITs as it is.

FIG. 14 is for performing feedback control of the injection timing.

In step 51, the command injection timing ITs and the rotational speed Ne are read, and the basic TCV duty value D is referred to by referring to a map having the contents shown in FIG.
TY [%] is calculated. As shown in FIG. 15, the value of DTY becomes smaller toward the retard side. This is because the smaller the TCV duty value is, the more the timing control valve 33 becomes.
Are opened, the amount of leakage from the high pressure chamber 28 to the low pressure side increases, and the position of the timer piston 26 moves to the retard side. In addition, since the injection timing needs to be advanced as the rotation speed decreases, the rotation speed Ne is also used as a parameter in FIG.

In steps 53 and 54, a clamp permission flag and a clamp release flag are checked. Clamp enable flag =
Only when 1 and the clamp release flag = 0 (during clamping), the process proceeds to steps 55 and 56, and the feedback control of the injection timing is stopped. That is, the basic TCV duty value DTY is used as it is as the command TCV duty value DTY.
SET is set, and is transferred to the output register in step 56.

On the other hand, when the clamp is not being performed, the routine proceeds to step 57 and thereafter, and feedback control of the injection timing is performed as in the conventional case. In step 57, the timer piston position C
tp [V] is read, and the value of Ctp is read from step 5
In step 8, the actual injection timing ITi [mm] is calculated by referring to the table having the contents shown in FIG.

In step 59, the difference ITh [mm] between the actual injection timing and the command injection timing is calculated.

[0066]

## EQU2 ## The feedback correction amount DDTY [mm] is calculated from the difference ITh by referring to a table having the contents shown in FIG.

In step 61, the value obtained by adding the feedback correction amount DDTY to the above DTY is set as a command TCV duty value DTYSET, and then the operation of step 56 is executed.

From the command TCV duty value DTYSET set in this way, ON and OFF pulses are generated and output to the timing control valve 33.

Here, the operation of the present embodiment will be described.

In the present embodiment, when it is determined that the engine is idling at a very low temperature, the clamp permission flag is set to 1, and the injection timing is clamped from this timing (t1 in FIG. 6) to maintain a constant value (FIG. 6). In the uppermost line). As a result, the engine speed rapidly changes due to combustion instability in the idle state at a very low temperature, and even if the fuel injection amount increases or decreases due to the feedback control of the idle speed in response to this sudden change, the increase or decrease also occurs. Since the injection timing does not change according to the fuel injection amount, excessive combustion deterioration can be prevented.

In the idle state, the actual injection timing IT
When feedback control is performed so that i becomes the target injection timing, the actual injection timing tries to follow the target by feedback control of the injection timing when the target injection timing changes, but the change of the target injection timing is continuous. in case of,
The feedback control of the injection timing also impairs the stability of the control. On the other hand, in the present embodiment, the feedback control of the injection timing is also stopped, so that the stability of the control is not hindered.

If the injection timing is clamped until the engine is no longer in the idle state, the injection timing cannot be given according to the accelerator request. However, in the present embodiment, the clamp is released when the engine is no longer in the idle state.
It can be adjusted to the accelerator request.

In the idle state, the clamp is not required when the misfire is unlikely to occur. Therefore, according to the present embodiment, when the misfire is unlikely to occur (the water temperature Tw exceeds the predetermined value A). In some cases, unnecessary control is not performed by releasing the clamp (when a predetermined clamp time has elapsed after the complete explosion determination).

When the idling rotational speed becomes higher than the predetermined rotational range and becomes higher, the rotational speed becomes stable and no clamping is required. It is not necessary to perform a simple control. In some cases, the idle rotation speed is increased in order to enhance the heating performance. In this case as well, the injection timing for improving the heating performance can be set by releasing the clamp.

When the target injection timing is set according to the water temperature Tw, the target injection timing changes to the retard side as the water temperature Tw rises, so that the clamp is released (t2 in FIG. 6). Although a step in the injection timing occurs, and the combustion state of the engine changes suddenly, according to the present embodiment, after the clamp is released, the target injection timing is slowly approached to the target injection timing according to the water temperature Tw (the uppermost stage in FIG. 6). ), It is possible to prevent such a sudden change in the combustion state.

Although the embodiment has been described with reference to an engine having a distribution type fuel injection pump, the invention is not limited to this. As an example, when calculating the target injection timing for an engine having a distribution type fuel injection pump of the inner cam pumping type, in addition to the water temperature correction amount, the load correction coefficient is calculated using a map value using the fuel injection amount and the engine speed as parameters. And replace the above equation (1) with

[0077]

In some, the target injection timing ITs1 is calculated by the formula: ITs1 = IT0 + ITTw × load correction coefficient. At this time, in addition to the basic injection timing IT0, the load correction coefficient fluctuates under the influence of the feedback control of the idle rotation speed, so that the application of the present invention is effective.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electronic control distribution type fuel injection pump.

FIG. 2 is a perspective view of a rotary solenoid.

FIG. 3 is a diagram showing a positional relationship between a rotary shaft of a rotary solenoid and a control sleeve.

FIG. 4 is a sectional view of a timer part.

FIG. 5 is a control system diagram of the electronic control injection pump.

FIG. 6 is a waveform chart for explaining the operation of the embodiment.

FIG. 7 is a flowchart for explaining calculation of a target injection timing.

FIG. 8 is a map characteristic diagram of a basic injection timing.

FIG. 9 is a map characteristic diagram of a water temperature correction amount.

FIG. 10 is a flowchart for explaining determination of a clamp permission condition.

FIG. 11 is a flowchart for explaining determination of a clamp release condition.

FIG. 12 is a table characteristic diagram of a clamp time.

FIG. 13 is a flowchart for explaining calculation of a command injection timing.

FIG. 14 is a flowchart for explaining feedback control of the injection timing.

FIG. 15 is a map characteristic diagram of a basic TCV duty value.

FIG. 16 is a table characteristic diagram of actual injection timing.

FIG. 17 is a table characteristic diagram of a feedback correction amount.

FIG. 18 is a waveform chart for explaining the operation of the conventional device.

FIG. 19 is a diagram corresponding to claims of the first invention.

[Explanation of symbols]

 16 Control Sleeve 26 Timer Piston 33 Timing Control Valve 35 ECU 36 Accelerator Sensor 40 Water Temperature Sensor 44 Idle Switch

Claims (6)

[Claims] A means for performing feedback control by increasing or decreasing the fuel injection amount so that the idle rotation speed becomes a target value; a means for calculating a target injection timing according to the increased or decreased fuel injection amount; A control unit for controlling the injection timing adjusting means so as to attain the target injection timing; a control unit for determining whether or not the engine is in an idle state at a cryogenic temperature; and Means for fixing the target injection timing in an idle state. 2. The fuel injection timing control device for a diesel engine according to claim 1, wherein the fixed injection timing is an injection timing when a predetermined clamp permission time has elapsed after the start. 3. The method according to claim 2, wherein the feedback control of the injection timing is stopped when the target injection timing is fixed, when a means for performing the feedback control is provided so that the actual injection timing becomes the target injection timing. Item 3. A fuel injection timing control device for a diesel engine according to item 2. 4. The following conditions are satisfied: a) when the engine is no longer in an idle state; b) when a state in which misfiring is unlikely to occur; c) when a predetermined engine rotation range is exceeded. The fuel injection timing control device for a diesel engine according to claim 2 or 3, wherein the fixed injection timing is released. 5. When the target injection timing is set also according to the engine water temperature, the target injection timing is released from being fixed, and then gradually approaches the target injection timing according to the engine water temperature. The fuel injection timing control device for a diesel engine according to claim 4. 6. The fuel injection timing control apparatus for a diesel engine according to claim 5, wherein the processing for slowly approaching is a ramp processing.