JPH0325626B2 - - 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.

[Prior Art] As such a fuel injection timing control device, conventionally,
As shown in Special Publication No. 53-16450,
A system is known in which the fuel injection timing is determined in accordance with the engine speed and the fuel injection amount so as to provide the most appropriate fuel condition for various operating conditions.

[Problems to be solved by the invention] According to this, when the air density is low and the intake pressure is low, such as at high altitudes, the compression pressure does not increase that much, so the ignitability of the fuel is low at the normal injection timing. Unfortunately, there is a problem in that unburned components are generated, which are thermally decomposed and white smoke is generated from the exhaust pipe. Therefore, in the past, when engines were used exclusively at high altitudes, the injection timing was set to be more advanced than in normal engines.
However, according to this, when the atmospheric pressure is high, such as on flat ground, the fuel injection timing is too early and the intake air mass is large, causing the fuel to explode.
There was a problem that so-called diesel lock occurred.

An object of the present invention is to solve the above-mentioned conventional problems. In other words, it is an object of the present invention to provide a fuel injection timing control device for a diesel engine that can reduce and prevent the generation of white smoke and diesel knock caused by changes in intake pressure. It is about providing.

[Means for solving the problems] The present invention has been made to achieve the above object,
A fuel injection timing that calculates a basic fuel injection timing corresponding to a reference atmospheric pressure based on a fuel injection amount and an engine rotational speed, and controls the fuel injection timing of a diesel engine according to the calculated basic injection timing. In the control device, an intake pressure detection means for detecting the intake pressure of the engine, and a correction amount for advancing or retarding the basic injection timing based on the detected intake pressure and the engine rotation speed. a correction amount calculation means for determining whether or not the calculated correction amount exceeds a certain upper limit value set in advance, and changing the correction amount to the upper limit value if the correction amount exceeds the upper limit value; and basic injection timing correction means that advances or retards the basic injection timing based on the correction amount set by the correction amount calculation means or the correction amount upper limit restriction means, The correction amount calculation means calculates an advance angle correction amount for advancing the basic injection timing so that when the intake pressure is lower than the reference atmospheric pressure, the value becomes larger as the intake pressure is lower and the engine speed is higher. Or, when the intake pressure is higher than the reference atmospheric pressure, calculate the retardation correction amount to retard the basic injection timing so that the higher the intake pressure and the lower the engine speed, the larger the value. The gist of the present invention is a fuel injection timing control device for a diesel engine, which is characterized in that it is configured to do the following.

[Function] In the diesel engine fuel injection timing control device of the present invention configured as described above, the correction amount calculation means advances or retards the basic injection timing based on the intake pressure and the engine speed. When the calculated correction amount exceeds a preset upper limit value, the correction amount upper limit setting means detects this and sets the correction amount to the upper limit value. In addition, in the correction amount calculation means, when the intake pressure is lower than the reference atmospheric pressure when calculating the basic injection timing, the basic injection timing is advanced so that the lower the intake pressure is and the higher the engine speed is, the larger the value becomes. Calculate the advance angle correction amount to correct for Calculate the amount of retardation correction for correcting to the angle side. When the advance or retard correction amount of the basic injection timing is set by the correction amount calculation means or the upper limit value setting means in this way, the basic injection timing correction means adjusts the set advance or retard correction amount. The basic injection timing is corrected based on the following.

Therefore, in the present invention, when the intake pressure is lower than the reference atmospheric pressure, the basic injection timing is advanced more greatly as the intake pressure is lower and the engine speed is higher, with a preset upper limit being the upper limit, or When the intake pressure is higher than the reference atmospheric pressure, the basic injection timing is retarded more greatly as the intake pressure is higher and the engine speed is lower, with a preset upper limit being the upper limit.

First, in the correction amount calculating means, when the intake pressure is lower than the reference atmospheric pressure, the lower the intake pressure is and the higher the engine speed is, the higher the advance angle correction amount is set. When the pressure is lower than atmospheric pressure, the air density of the atmosphere decreases, making it difficult to ignite the fuel. Also, when the engine is running at high speeds, the time per engine revolution is shorter than when it is at low speeds, making it suitable for ignition in the cylinder after fuel injection. This is because the rotation angle required to form an air-fuel mixture becomes larger than when the rotation is low.

In other words, by setting the advance angle correction amount to a larger value as the intake pressure is lower than the reference atmospheric pressure and advancing the basic injection timing to a greater extent, the generation of white smoke caused by a delay in fuel ignition due to a decrease in intake air density is prevented. death,
In addition, by increasing the advance angle correction amount as the engine speed increases, it is possible to prevent a delay in fuel ignition at high engine speeds, while also preventing premature ignition of the fuel by advancing the injection timing too much at low engine speeds. This prevents diesel knock from occurring.

Conversely, when the intake pressure is higher than the reference atmospheric pressure, the correction amount calculation means sets the retardation correction amount to a larger value as the intake pressure is higher and the engine speed is lower. This is because the air density of the atmosphere increases, making it easier for the fuel to ignite, and the fuel ignites earlier when the engine is running at low speeds compared to when the engine is at high speeds.
In other words, by setting the retardation correction amount to a larger value as the intake pressure is higher than the reference atmospheric pressure and greatly retarding the basic injection timing, early ignition of fuel due to an increase in intake air density is prevented, and the retardation correction amount is set to a larger value. By increasing the amount as the engine speed decreases, premature ignition of the fuel at low engine speeds can be prevented.
This prevents the injection timing from being delayed too much when the engine rotates at high speeds, which would cause a delay in fuel ignition.

Further, in the present invention, when the correction amount calculated by the correction amount calculation means exceeds a certain upper limit value, the correction amount upper limit setting means changes the correction amount to the upper limit value. If the correction amount becomes too large due to incorrect detection of intake pressure, etc., the basic injection timing is advanced or retarded too much, and the corrected injection timing used for control becomes a value that does not correspond to the operating condition. This is to prevent

In order to prevent over-advancement or over-retardation of the fuel injection timing, it is sufficient to set upper and lower limits for the injection timing after correction, but with such a method, the amount of correction becomes large and injection If the timing exceeds the upper and lower limits, the injection timing will be uniformly set to the upper and lower limits, making it impossible to perform injection timing control according to the basic injection timing set based on the fuel injection amount and engine speed. Therefore, in the present invention, by setting an upper limit value for the correction amount, when the correction amount becomes a large value, the injection timing that is the basic injection timing corrected by the upper limit value (i.e., the injection timing corresponding to the basic injection timing) ) to control fuel injection timing.

Also, in the same way as when calculating the correction amount, the higher the engine speed, the higher the upper limit of the advance angle correction amount, taking into account the difference in time per engine rotation between high engine speed and low engine speed. Although it is possible to set a value and set the upper limit value of the retard angle correction amount to a larger value as the engine speed decreases, in the present invention, a predetermined constant value is used as the upper limit value. If the upper limit value is also set according to the engine speed, taking into account the difference in time per engine revolution between high and low engine speeds, for example, when the engine is at high speeds, If an abnormality occurs in the detected intake pressure value, the basic injection timing, which should normally be controlled based not only on the engine speed but also on the fuel injection amount, will be set to a large upper limit based on the engine speed, regardless of the fuel injection amount. This is because the engine operating condition may suddenly change due to the advance angle being corrected and the injection timing being overadvanced (for example, the fuel may diffuse even though the fuel injection amount is small, resulting in a misfire).

That is, in the present invention, by using a predetermined constant value as the upper limit value of the correction amount, unlike the case where the upper limit value is increased depending on the difference in engine speed, the engine is not operated suddenly due to incorrect detection of intake pressure, etc. This prevents fluctuations from occurring.

[Example] Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a fuel injection pump and a control device suitable for applying the present invention.

A fuel injection pump 1 includes a drive shaft 11 driven by an engine, a gear 12 provided at an end of the drive shaft 11, and a roller 1.
3. A cam plate 14 loosely connected to the roller 13, a pump plunger 15 having a spill port 50 therein and connected to the plate 14 for sending fuel to the injection nozzle 2 of the engine; A fuel pump 17 that sends fuel to the injection nozzle 2 and the timer piston 16, a timer position sensor 18 that electrically detects the position of the timer piston 16, a timing control valve 19 that determines the advance angle adjustment, and a pulse that corresponds to the rotation speed of the gear 12. An electromagnetic pickup sensor 20 as a rotation speed detector that outputs a signal, a spill ring 21 that is driven by a linear solenoid to adjust the injection amount, and a linear solenoid 2 that drives the spill ring 21.
2. Coil 2 constituting the linear solenoid 22
3, a plunger 24 that drives the spill ring 21, a spill position sensor 25 that detects the amount of movement of the plunger 24, and a pump plunger 1.
FCV2 performs on/off control of fuel amount to 5.
6 (consisting of excitation coil 27 and valve 28),
It consists of a delivery valve 56 and a regulating valve 29 for preventing backflow of fuel from the pump plunger 15 and prevention of dripping.

The cam plate 14 rotates and reciprocates together with the pump plunger 15. This reciprocating motion is caused by the cam plate 14 riding on the roller 13, which is rotatable but fixed in the axial direction of the shaft. Pump plunger 1
5 rotates to distribute fuel.
In order to adjust the injection quantity, the injection quantity is determined by the effective stroke of the pump plunger 15. Excess fuel in the pump is returned to the pump 17 via the orifice 30. Further, the linear solenoid 22 and FCV 26 in the fuel pump 1 are controlled by the control device 3, and output signals from various sensors are taken in for this purpose. That is, the engine rotation speed signal from the electromagnetic pickup sensor 20
S _N and the output signal S _S of the spill position sensor 25, the output signal S _{P of the intake pressure sensor 6 also provided in the intake manifold 4, the output signal S W of} the water temperature sensor 7 that measures the engine cooling water temperature, and the amount of depression of the accelerator 8. Output signal S _ACC of accelerator sensor 9 that detects
each of them.

FIG. 2 is a detailed block diagram of the control device 3 shown in FIG.

With a central processing unit (CPU) 31 as the core, a read-only memory (ROM) 32 stores processing programs and monitor programs for executing various processes, and temporarily stores calculation contents and output contents of each sensor. A random access memory (RAM) 33 and an input/output circuit 34 have a backup memory that stores calculation contents, set values, etc. even when the power is turned off.
is connected to the CPU 31 via the bus line 35,
A so-called microcomputer is configured.
The output devices connected to and controlled by the CPU 31 are the linear solenoid 22, the FCV 26, and the timing control valve 19. It is driven via a D/A converter 37, a servo amplifier 38, and further via a drive circuit 39. The input/output circuit 34 is for receiving sensor outputs, and receives the outputs of the sensors 5, 6, 7, 9, 18, and 25 (taken out via buffers 40, 41, 42, 43, 44, and 51). Sequentially or select one of them with the multiplexer (MPX) 45,
The data is converted into a digital signal by the A/D converter 46 and then output to the bus line 36. Further, the output signal from the electromagnetic pickup 20, which serves as a rotation speed detector for detecting the engine rotation speed, is waveform-shaped by a waveform shaping circuit 47 and then input to the CPU 31.
A clock circuit 48 is provided for sending clock pulses to each of converter 46 and D/A converter 37.

FIG. 3 is a flowchart showing an embodiment of the present invention. The example shown here is a case where the basic fuel injection timing is calculated based on a flatland (lowland) where the atmospheric pressure is high, and is corrected at a highland where the atmospheric pressure is low.

The fuel injection amount Q is calculated based on the engine rotation speed N _E obtained by the electromagnetic pickup sensor 20 and the accelerator opening A _CCP obtained from the accelerator sensor 9, and the basic fuel is calculated from this fuel injection amount Q and the engine rotation speed N _E. The injection timing _TBASE is calculated in step 101. The basic injection timing T _BASE is determined by storing a map as shown in FIG. 4 in advance. Then, in step 102, the intake pressure is detected by the intake pressure sensor 6.
Pm (mmHgabs) is read, and in step 103, the high altitude injection timing correction amount T _H (℃A) is calculated from the read intake pressure Pm and the engine speed N _E using a map as shown in Fig. 5. . In this map, as shown in Fig. 6, the correction amount T _H is set so that the lower the intake pressure Pm and the higher the engine speed N _E , the more the basic injection timing can be corrected to the advanced side. Atmospheric pressure on flat ground 760mm
720mmHgabs with a slight variation range from Hgabs
As shown in FIG. 7, T _H is set to 0 at around 720 mmHgabs so that advance angle correction can be started using a nearby value as the reference atmospheric pressure.

Next, in step 104, the correction amount obtained above is
Determine whether T _H is a negative value and determine whether T _H <0℃A
If so, the process moves to step 106 and the correction amount T _H is uniformly set to 0°C. If T _H ≧0℃A, the process moves to step 105, where it is determined whether or not the correction amount T _H is greater than or equal to the upper limit value 3℃A, and if T _H ≧3℃.
If it is ℃A, the process moves to step 170 and the correction amount T _H
is set to an upper limit of 3°C.

In addition, when T _H <0℃A, the correction amount T _H is
The basic injection timing is to uniformly set the temperature to 0℃A.
This is to prevent T _BASE from being retarded.
Also, when T _H ≧3℃A, the correction amount T _H is determined in step 107.
The reason for uniformly setting 3℃A is the basic injection timing.
This is to prevent T _BASE from advancing too much.
In other words, for example, due to a malfunction of the intake pressure sensor, the amount of correction
If T _H is calculated to be a very large value, or if the correction amount is determined by other external factors, the correction amount for the basic injection timing may become a very large value, which may adversely affect the engine injection timing. Therefore, in order to prevent such a situation from occurring, in this embodiment, an upper limit value of 3℃A is set for the high altitude injection timing correction amount T _H , and the correction amount T _H is kept below this upper limit value of 3℃A. be.

Then, in the following step 108, the step
The basic injection timing T _BASE is advanced by adding the injection timing correction amount T _H obtained in steps 103, 106, or 107 to the basic injection timing T _BASE obtained in step 101 (T _BASE + T _H ). Correct this and set this as the final injection timing.
Let it be T _FIN . Further, in step 109, the current injection timing T _P is calculated based on the output signal of the timer piston sensor 18. In step 110, this T _P is subtracted from T _FIN obtained in step 108 (T _FIN -T _P ) to calculate the deviation ΔT. Next, in step 111, the drive output (duty) of the timing control valve 19 is determined based on ΔT.
is calculated, and the duty determined in step 112 is output to the timing control valve 19 to perform injection timing control.

As explained above, in this embodiment, in a diesel engine in which the basic injection timing T _BASE is set based on flat ground, the intake pressure Pm is lower than the reference atmospheric pressure (in this embodiment, a value around 720 mmHgabs).
The higher the engine speed N _E , the more the basic injection timing.
T _BASE is corrected to the advanced angle side. For this reason, when the intake pressure (that is, atmospheric pressure) Pm decreases as the diesel engine moves to higher altitudes, and the air density of the atmosphere decreases, the ignitability of the fuel is ensured, and the unburned components of the fuel It is possible to prevent white smoke from being generated, and also to prevent knocking from occurring due to early ignition of fuel caused by advancing the basic injection timing too much when the engine rotates at low speeds.

Also, the correction amount T _H for this advance angle correction is set to an upper limit value of 3°C A, and the correction amount T _H obtained from the intake pressure Pm and the engine speed N _E is set to an upper limit value of 3°C A.
If the value exceeds this value, the correction amount T _H is changed to the upper limit of 3℃A, so if the correction amount T _H becomes a very large value due to a malfunction of the intake pressure sensor, etc., the overadvance angle can be prevented.

Here, in the above embodiment, since we considered the case where the basic injection timing is set based on flat ground,
The basic injection timing was advanced as we moved to higher altitudes (i.e., as the intake pressure Pm decreased), but the basic injection timing was set based on the higher altitudes, and as we moved to lower altitudes (i.e., as the intake pressure Pm increased), the basic injection timing advanced. The injection timing may be delayed.

In this case, when calculating the correction amount in step 103 of FIG. 3, for example, as shown in FIG.
Hgabs is the standard atmospheric pressure at high altitude, and the intake pressure Pm
In order to be able to retard the basic injection timing T _BASE as the pressure increases from this reference atmospheric pressure,
It is sufficient to use a map such as that shown in Fig. 5, in which the value near 500 mmHgabs is set to 0, and the absolute value of T _H , which becomes negative as the intake pressure Pm increases, is set as the low-altitude injection timing correction amount T' _H (℃A). In step 108, the low-altitude injection timing correction amount T′ _H obtained using this map is subtracted from the basic injection timing T _BASE (T _BASE −
T′ _H ) to retard the basic injection timing T _BASE .

With this configuration, in a diesel engine where the basic injection timing T _BASE is set based on high altitude, the intake pressure Pm is higher than the reference atmospheric pressure (in this case, a value around 500mmHgabs), and the engine speed N _E is The lower the base injection timing T _BASE
is corrected to the retarded side, and it is possible to prevent knocking when fuel becomes more likely to ignite as the intake pressure (i.e., atmospheric pressure) Pm increases.
Further, as in the above embodiment, fuel ignition can be optimally controlled according to the engine speed.

[Effects of the Invention] As detailed above, in the diesel engine fuel injection timing control device of the present invention, the basic fuel injection timing corresponding to the reference atmospheric pressure calculated based on the fuel injection amount and the engine rotation speed is As the intake pressure is lower than the reference atmospheric pressure and the engine speed is higher, the angle is corrected to the advanced side, or as the intake pressure is higher than the reference atmospheric pressure and the engine speed is lower, the angle is corrected to the retarded side, and this corrected fuel injection timing controls the fuel injection control. It will be done.
As a result, diesel engines are moved to higher altitudes,
When the atmospheric pressure drops, or when the diesel engine moves to a low-lying area and the atmospheric pressure rises, it is now possible to optimally control the fuel injection timing according to the engine speed, thereby adjusting the fuel ignition timing. This makes it possible to reduce white smoke, prevent misfires, reduce and prevent diesel knock, etc., at the timing required by the engine. In addition, a certain upper limit value is set for the correction amount for correcting the basic injection timing, and if the correction amount exceeds the upper limit value, it is necessary to change the correction amount to the upper limit value, so erroneous detection of intake pressure When the correction amount becomes large due to reasons such as this, it is possible to prevent the basic injection timing from being advanced or retarded too much.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram around a fuel injection pump suitable for applying the present invention, FIG. 2 is a detailed block diagram of the control device 3 shown in FIG. 1, and FIG. 3 is a flowchart showing an embodiment of the present invention. Chart, Figure 4 is the basic injection timing
An explanatory diagram showing the map used to calculate T _BASE ,
FIG. 5 is an explanatory diagram showing a map used for calculating the high altitude injection timing correction amount T _H , FIGS. 6 and 7 are diagrams explaining the characteristics of the map for calculating the high altitude injection timing correction amount shown in FIG. FIG. 8 is a diagram illustrating the characteristics of a map for calculating the low-altitude injection timing correction amount when retarding the basic injection timing. 1...Fuel injection pump, 3...Control device, 6...
...Intake pressure sensor, 9...Accelerator sensor, 15...
... Pump plunger, 18 ... Timer position sensor, 19 ... Timing control valve, 20 ... Electromagnetic pick-up sensor, 21 ... Spill ring, 2
2... Linear solenoid, 31... Central processing unit, 32... Read only memory (ROM), 33... Random access memory (RAM), 34... Input circuit, 35... Bus line, 36 , 39, 49...drive circuit, 37...
D/A converter, 38... Servo amplifier, 42, 4
3... Buffer, 47... Waveform shaping circuit.

Claims (1)

[Claims] 1. A basic fuel injection timing corresponding to a reference atmospheric pressure is calculated based on the fuel injection amount and the engine rotational speed, and the diesel engine fuel injection is performed according to the calculated basic injection timing. A fuel injection timing control device that controls the timing, includes an intake pressure detection means that detects the intake pressure of the engine, and advances or retards the basic injection timing based on the detected intake pressure and the engine rotation speed. a correction amount calculation means for calculating a correction amount for the correction; correction amount upper limit limiting means for changing the correction amount to an upper limit value; and basic injection timing correction for advancing or retarding the basic injection timing based on the correction amount set by the correction amount calculating means or the correction amount upper limit limiting means. means, and the correction amount calculation means is configured to advance the basic injection timing so that when the intake pressure is lower than the reference atmospheric pressure, the value becomes larger as the intake pressure is lower and the engine speed is higher. or to retard the basic injection timing so that the higher the intake pressure and the lower the engine speed, the larger the value when the intake pressure is higher than the reference atmospheric pressure. A fuel injection timing control device for a diesel engine, characterized in that it is configured to calculate a retardation correction amount.