JPH0319376B2 - - Google Patents

Description

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

(Conventional technology) In general, in diesel engines, particulate matter contained in the exhaust gas contains a large amount of HC in the low load range, and as the load reaches the high load range,
It is known that smoke C increases as HC decreases. It is also known that the fuel injection timing of the fuel injection pump has a large effect on HC and the amount of smoke, and that advancing the fuel injection timing will reduce HC, while retarding it will reduce smoke.

By the way, conventionally, there is a demand for advancing the fuel injection timing during acceleration in order to improve output, so it has been known to advance the fuel injection timing during acceleration.

(Problem to be Solved by the Invention) However, since the conventional advance angle during acceleration is a constant advance angle regardless of the load condition, smoke increases in the high load range.
Conversely, if the advance angle is decreased, the
This has the disadvantage that HC increases.

Furthermore, although it has conventionally been known to advance the engine angle in accordance with the load condition, the advance angle is performed regardless of acceleration.

By the way, as a prior art, for example,
As described in Japanese Patent No. 112041, a distribution type fuel injection pump that controls fuel injection timing according to load is known.

The present invention is a fuel injection timing control device for a diesel engine that is capable of improving output during acceleration, and reducing HC in exhaust gas in a low load range and smoke in exhaust gas in a high load range. The purpose is to provide

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention includes a fuel injection timing variable means provided in a fuel injection pump, an acceleration detection means for detecting an acceleration state of an engine, and an acceleration detection means for detecting an acceleration state of an engine. A load detection means detects the load state, and the amount of correction advance angle is set to be large with respect to the reference timing in a low load area during acceleration, and small in a high load area, according to the outputs of both of the above-mentioned detection means. and injection timing setting means for operating the fuel injection timing variable means.

(Operation) During acceleration, the fuel injection timing is further advanced than in normal times to improve output.

At the same time, simply advancing the fuel injection timing by a certain amount causes problems in terms of smoke, so the higher the load, the smaller the advance amount must be. controlling the injection timing variable means,
With respect to the standard timing, in the low load range, the amount of correction advance angle is increased to achieve a low range of HC, while in the high load area, the amount of correction advance angle is decreased to reduce smoke, and the particulate rate during acceleration is reduced. A reduction takes place (see FIG. 5). Note that the reference timing is set in consideration of the load, but when accelerating, load correction is performed because there is a demand for significantly increasing output and accelerating performance.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 and 2, 1 is an indirect injection type four-cylinder diesel engine, 2 is a combustion chamber of each cylinder 3, 4 is an intake passage, and a main intake passage 5.
The combustion chamber 2 of each cylinder 3 is branched from the main intake passage 5.
It consists of four branch intake passages 6 communicating with each other, and each branch intake passage 6 is provided with an air heater 7 for heating intake air.

8 is an intake throttle valve whose opening and closing are controlled by a diaphragm device 9. In the diaphragm device 9, a casing 9a is divided into a first chamber 9c and a second chamber 9d by a diaphragm 9b. 1st
A spring 9e is compressed in the chamber 9c, and a negative pressure passage 11 in which a negative pressure control solenoid valve 10 is interposed is connected. Further, the diaphragm 9b is linked to the intake throttle valve 8 via a link mechanism 9f extending toward the second chamber 9d.

The intake throttle valve 8 has, for example, an engine cooling water temperature (hereinafter simply referred to as water temperature) of 30 to 60°C, an engine load (hereinafter referred to as average effective pressure Pe) of 1 kg/cm ² or less,
In addition, the intake negative pressure is controlled to improve the heating efficiency of the air heater 7 in a region where the engine speed is 2000 rpm or less.

12 is an exhaust gas recirculation passage (hereinafter referred to as EGR passage)
The exhaust passage 13 is connected to the intake passage 4 downstream of the intake throttle valve 8. In the middle of EGR passage 12,
A blocker 16 having a large diameter hole 14 and a small diameter hole 15 is interposed, and first and second exhaust recirculation valves 17 and 18 (hereinafter referred to as
EGR valve) is installed. Each EGR valve 1
7, 18, the casings 17a, 18a are connected to the first chambers 17c, 18c by the diaphragms 17b, 18b.
and second chamber 17d, 18d, first chamber 1
Springs 17e and 18e are compressed to 7c and 18c, and negative pressure control solenoid valves 19 and 2
Negative pressure passages 21 and 22 with 0 interposed therebetween are connected,
Second chamber 17d, 1 of diaphragm 17b, 18b
Valve bodies 17g and 18g for opening and closing the holes 14 and 15 are connected to the 8d side via rod members 17f and 18f.

The first and second EGR valves 17 and 18, together with the intake throttle valve 8, are operated, for example, at a water temperature of 60 to 100°C, an engine load of 6 kg/cm ² or less, and an engine rotation speed of 90 to 100°C.
It is controlled according to the engine load as follows in the range of 3000 rpm and 1st to 4th speed (for a 5th speed car).

() When the engine load is 5 to 6 kg/cm ² ...
The first EGR valve 17 is closed, the second EGR valve 18 is open, and the intake throttle valve 8 is fully open.

() When the engine load is 4.5 to 5 Kg/cm ² ...
The first EGR valve 17 is open, the second EGR valve 18 is closed, and the intake throttle valve 8 is fully open.

() When the engine load is 0 to 4.5Kg/ ^cm2 ...
The degree of closing of the intake throttle valve 8 is controlled by opening the first EGR valve 17 and closing the second EGR valve 18.

() If the engine load is 0Kg/ ^cm2 or less...
The first EGR valve 17 is closed, the second EGR valve 18 is closed, and the intake throttle valve 8 is opened at a constant degree.

Reference numeral 30 denotes a fuel injection pump, which has a timer piston 33 that slides inside a cylinder 32 formed in a housing 31, and a timer 34 as a fuel injection timing variable means for controlling fuel injection timing.
It is equipped with The timer piston 33 is connected to a roller holder 36 via a swingable lever 35. A spring 37 is compressed on one side of the cylinder 32 with the timer piston 33 in between, and a feed pump (not shown) is installed.
A first hydraulic chamber 38 to which the suction side fuel pressure acts is formed, and a second hydraulic chamber 41 to which the fuel pressure of the pump chamber 40 acts through a hydraulic passage 39 provided in the timer piston 33 is formed on the other side. The first hydraulic chamber 38 and the second hydraulic chamber 41 are connected through a connection path 43 in which an on-off valve 42 whose duty is controlled by a control unit 60, which will be described later, is interposed.

Therefore, basically, the position of the timer piston 33 is determined by the differential pressure between the first hydraulic chamber 38 and the second hydraulic chamber 39, that is, the fuel pressure according to the engine speed, and the elastic force of the spring 37. That is, the position of the roller holder 36 in the inner circumferential direction is determined via the lever 35, and thereby the injection timing is determined. However, by controlling the duty of the on-off valve 42, the differential pressure can be adjusted, and the injection timing is determined. Timing correction is performed.

50 is an intake pressure sensor that is arranged in the intake passage 5 downstream of the intake throttle valve 8 and detects the intake pressure, 51 is a water temperature sensor that detects the engine cooling water temperature, and 52 is a shift position where a shift lever (not shown) is located. 5-speed switch 53 and 54 are load sensors (load detection means) and rotational speed sensors provided in the fuel injection pump 30 to detect the engine load and rotational speed, and 55 is a rotational speed sensor that detects the position of the timer piston 33. It is a position sensor.

60 is a control unit that controls the operation of the engine 1, and includes an air heater 7, negative pressure control solenoid valves 10, 19, 20, an intake pressure sensor 50, a water temperature sensor 51, a 5-speed switch 52, and a load sensor 5.
3. Rotation speed sensor 54, timer piston 34 of fuel injection pump 30 and position sensor 55
are electrically linked and function as timing setting means.

Incidentally, the advance angle of the fuel injection pump 30 is controlled by the control unit 60 as follows.

() Water temperature below 30℃, engine load below 0Kg/ ^cm2 , engine speed below 2000rpm, and intake temperature
In the area below 10℃, the advance angle is controlled according to the water temperature, rotation speed, and intake air temperature.

() In each water temperature range of 30-60℃ or less and 60-100℃, engine load 6Kg/cm ² or less, engine speed 900-3000rpm, intake temperature 10℃ or more, and 1st-4th gear (for 5-speed vehicles) ), the load,
Advance angle control according to rotation speed.

() In areas other than () and () above, the advance angle is controlled according to the engine speed.

As shown in detail in FIG. 2, the control unit 60 determines a reference fuel injection timing (hereinafter referred to as reference timing) using a load signal from a load sensor 53 and a rotation signal from a rotational speed sensor 54 using a timing calculation circuit 101. On the other hand, the acceleration detection circuit 102 determines whether or not it is an acceleration based on the rotation signal, and if it is an acceleration, the correction amount calculation circuit calculates the correction advance amount with respect to the reference timing according to the degree of acceleration. 103 (the amount of corrected advance angle is large in a low load area and small in a high load area). Then, the reference timing is corrected, a duty ratio is set in the duty ratio control circuit 104 according to the corrected injection timing, and the on-off valve 42 is duty-controlled according to the duty ratio to determine the position of the timer piston 33. , controls fuel injection timing.

The acceleration detection circuit 102 includes a differentiation circuit 105 which calculates acceleration by differentiating the rotation signal, and a first differentiation circuit 105 which compares the acceleration with a set value to detect sudden acceleration.
It has a comparison circuit 106 and a second comparison circuit 107 that detects slow acceleration.

A signal from the 5th speed switch 52 (5th speed signal) is input to the correction amount calculation circuit 103 as a cancel signal.

In the duty ratio control circuit 104, a timing detection circuit 108 detects the actual injection timing based on the position signal of the timer piston 33 from the position sensor 55, and a correction signal is inputted based on the result.

Further, the rate of change detection circuit 10
9 detects the rate of change in the engine load, and if the rate of change is on the (minus) side by a predetermined value or more, it is determined that a gear change is required. The duty ratio is fixed for a certain period of time.

Next, the control operation of the control unit 60 will be explained with reference to FIGS. 3 to 6.

First, in step S1, a rotation signal is input from the rotation speed sensor 54, and in step S2, a rotation signal is input to the load sensor 54.
A load signal is input from step 3, and the step
At S3, the reference timing is read from the control map (see Fig. 4) according to the engine speed and engine load and is stored.

The rotation signal is differentiated in step S4, and based on the result, it is determined in step S5 whether or not it is accelerating.
In the case of YES, the process moves to step S6, while in the case of NO, the process returns to step S1.

In step S6, it is determined whether the gear is in the 1st to 4th gears based on the signal from the 5th gear switch 52, and YES.
If so, the process moves to step S7, while if NO, that is, if the gear is in fifth gear, it is determined in step S8 that the advance (advance angle) is large. In step S7, it is determined whether or not there is sudden acceleration. Since it is desirable to change the absolute value of the advance angle correction amount depending on whether there is sudden acceleration or not, in the case of sudden acceleration, advance is set to medium in step S9. On the other hand, if the acceleration is not rapid, that is, if the acceleration is slow, the advance is determined to be small in step S10. Therefore, during acceleration, in the case of 5th gear, the advance angle correction amount is larger than in the case of 1st to 4th gears, and in the case of 1st to 4th gears, in the case of sudden acceleration, in the case of 5th gear. Although the advance angle correction amount is smaller than in the case of slow acceleration, the advance angle correction amount is larger than in the case of slow acceleration. Note that the load correction lines between step 9 and step S10 do not need to be parallel (that is, the difference in advance angle correction amount between step 9 and step S10 under the same load does not always need to be constant);
The advance angle correction amount is smaller on the high load side than on the low load side, and for the same load, the advance angle correction amount in step 9 only needs to be larger than the advance angle correction amount in step S10. Note that the advance angle correction amount is arbitrarily set based on the relationship between smoke and HC.

Subsequently, load correction is performed in step S11. Specifically, in a high load range, the correction advance angle is corrected to the retard side, that is, the correction advance amount becomes small, and in a low load area, the correction advance angle is corrected to the advance side, that is, the correction advance angle becomes large (see FIG. 5). This acceleration characteristic according to the load is achieved by adjusting the opening degree of the on-off valve 42 interposed in the connection path 43 in the timer 34 as a fuel injection timing variable means. That is, by controlling the duty of the on-off valve 42, the connecting path 43 is narrowed to advance the angle, and by opening it, the angle is retarded. The reason for performing load correction during acceleration is that although the reference timing is set taking into account the engine load, during acceleration there is a desire to increase the output and improve acceleration performance compared to normal times. Taking into account the particulate rate of HC, smoke, etc., instead of simply advancing the angle by a certain amount, the amount of advance decreases as the load increases.

Based on the result of step S11, the fuel injection timing is calculated in step S12, the load signal is differentiated in step S13 to calculate the load change rate, and based on the load change rate, in step S14, the fuel injection timing is determined to be below a predetermined value on the - (minus) side. Determine whether it exists or not. However, if YES in step S14, it is determined that a gear change has not been performed, so step S14 is determined to be YES.
In step S12, the duty is controlled in step S15 so that the injection timing is the same as that calculated in step S12, and then the process returns to step S1, and this process is repeated.

If NO in step S14, it is determined that a gear change is being performed, so the duty ratio is fixed in step S14, and it is determined in step S17 whether a certain period of time has elapsed. returns to step S14 and repeats this process. on the other hand,
If YES, it is determined that the gear change has been completed, and the process returns to step S1.

(Effects of the Invention) As described above, the present invention has a structure in which the amount of correction advance angle is large with respect to the reference timing in the low load area during acceleration, and is small in the high load area. It is possible to improve the output, and by increasing the amount of correction advance angle relative to the reference timing at low loads to reduce HC, and decreasing it at high loads to reduce carbon C.
It is also possible to reduce particulate matter during acceleration.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram of a fuel injection timing control device for a diesel engine, FIG. 2 is a block diagram showing the configuration of a control unit, and FIGS. FIG. 6 is a flowchart showing the flow of processing by the control unit. DESCRIPTION OF SYMBOLS 1... Diesel engine, 30... Fuel injection pump, 33... Timer piston, 34... Timer, 53... Load sensor, 54... Rotational speed sensor, 60... Control unit.

Claims (1)

[Claims] 1. A variable fuel injection timing means provided in the fuel injection pump, an acceleration detection means for detecting the acceleration state of the engine, a load detection means for detecting the load state of the engine, and an acceleration control device according to the outputs of both of the detection means. and injection timing setting means for operating the fuel injection timing variable means so that the corrected advance amount is large with respect to the reference timing in a low load range and small in a high load range. Fuel injection timing control device for diesel engines.