JP2002213282A - Engine fuel injection control method and its control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control method and its control apparatus enhancing an operating property by regulating engine speed for the prevention of seizure during startup, and avoiding a sudden change in the engine speed when this regulation is canceled. SOLUTION: A method of controlling fuel injection employs split fuel injection as a portion of fuel injection which continues for a predetermined period of time after complete explosion in the engine, and employs normal fuel injection as another portion of fuel injection which starts after the elapse of the predetermined period of time, based on a fuel increase/decrease signal coming from the outside. The predetermined period of time is divided into a first half period which gets longer the lower the temperature of engine cooling water, and a second half period which follows the first half period. Different engine speeds are predetermined for different temperatures of the engine cooling water. The split fuel injection effected during the first half period maintains the engine speed at or below a predetermined engine speed, and the split fuel injection effected during the second half period is based on the fuel increase/decrease signal coming from the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control method and a control apparatus for an engine, mainly a diesel engine with a supercharger for construction machinery.

[0002]

2. Description of the Related Art Conventionally, in construction engine engines, the engine is often started by setting an accelerator lever to a high idle position. In this case, the engine rotates at high speed before the lubricating oil reaches all parts of the engine. Would. As a result, lubrication may be insufficient and seizure may occur.
In particular, in an engine with a supercharger, the supercharger rotates at a high speed together with the engine main body, and seizure easily occurs in bearings of the supercharger. This is because the bearing of the supercharger is usually located at a position separated from the lubricating oil pressure source of the engine, so that the rotation of the lubricating oil after the engine is started is slow, and the turbocharger rotates at a higher speed than the engine body.

As a solution to the above problem, a control device and a control method of a rotational speed at the time of starting a supercharged engine are known from Japanese Patent Application Laid-Open No. Hei 6-212935. This means that the lubricating oil pressure of the engine is measured, and when the lubricating oil pressure is equal to or less than a predetermined value, the rotation speed of the engine is regulated to low idle rotation regardless of the position of the accelerator lever. This is a control for releasing the rotation speed regulation after waiting for the elapse.

[0004]

However, the above control device and control method have the following problems. For example, when the engine is started with the accelerator lever in the high idle position, the engine speed immediately after the start is restricted to the low idle speed. However, after the lubricating oil pressure exceeds a predetermined value and a predetermined time has elapsed, the engine speed is released from the regulation, and the engine speed suddenly changes from low idle rotation to high idle rotation. For this reason, the traveling speed and the working machine speed change suddenly, and the operability deteriorates.

The present invention focuses on the above-mentioned conventional problems, and combines the above-mentioned prior art for preventing seizure at the time of starting by restricting the engine speed with the split fuel injection, which is also a well-known technique, to cancel the restriction. It is an object of the present invention to provide a control method and a control device for an engine at the time of starting, which suppresses a sudden change in rotation speed of the engine and improves operability.

[0006]

In order to achieve the above object, the present invention provides a fuel injection system for a predetermined period of time after a complete explosion of an engine is defined as a split fuel injection, and the fuel injection after a predetermined period of time has elapsed from the outside. A normal fuel injection based on a fuel increase / decrease signal of
The predetermined time is divided into a first half, which is longer as the engine cooling water temperature is lower, and a second half following the first half, and a predetermined engine rotation speed is predetermined for each engine cooling water temperature, and the split fuel injection in the first half is determined by a predetermined period. , And the split fuel injection in the latter period is an injection based on a fuel increase / decrease signal from the outside.

In a fuel injection control device for an engine, the fuel injection at a predetermined time after the complete explosion of the engine is defined as split fuel injection, and the fuel injection after the predetermined time has elapsed is a normal fuel injection based on a fuel increase / decrease signal from the outside. The predetermined time period is set to be longer as the cooling water temperature of the engine is lower, the former period and the latter period divided in advance into the latter period following the previous period, and the predetermined engine rotation speed predetermined for each engine cooling water temperature. The engine cooling water temperature at the time of or immediately before the complete explosion of the engine is memorized, and the first half, the second half, and the predetermined engine speed of the length corresponding to this cooling water temperature are read from the memory, and the read first half is From the fuel injection nozzle, split fuel injection is performed to maintain the engine speed at or below a predetermined value. Perform a split fuel injection based on al fuel increase or decrease signal, the predetermined time has passed after injection, the fuel injection nozzle, and performs the normal fuel injection based on the fuel decrease signal from the outside.

Further, in the above-described method for controlling fuel injection of an engine or the control device thereof, the temperature of the engine cooling water may be the temperature of the lubricating oil of the engine.

According to the above control method or control device,
When the engine is started, the split fuel injection is performed for a predetermined time, and the rotation speed is restricted in the first half of the split fuel injection time, and the rotation speed is released in the second half. Therefore, even when the accelerator operation for requesting the high-speed rotation of the engine is performed at the time of releasing the rotation speed restriction, the split fuel injection is still performed at this time,
Sudden changes in rotation speed can be suppressed, and operability is improved.
Also, the lower the cooling water temperature or lubricating oil temperature, the lower the upper limit value of the rotation speed of the regulated engine is, and the longer the regulated time. The engine is warmed up for a longer period of time at a lower rotational speed, and is more severely protected from troubles such as bearing seizure.

[0010] Supplementally, split fuel injection is performed by pre-injecting a small amount of fuel a plurality of times (pilot injection) before injecting a large amount of fuel (main injection).
It is known as a technique for starting a spark in a cylinder with a small amount of fuel injected first and assisting ignition of a large amount of fuel injected later, and particularly, as a technique for easily starting an engine in cold weather. However, split fuel injection is said to reduce the efficiency of the engine and slow down the response of the rotational speed to the accelerator operation, for unknown reasons, and is not often used during normal operation. However, according to the above control method or control device,
By utilizing the property of slowing down the responsiveness, it is possible to prevent a sudden increase in the rotation speed when the restriction on the rotation speed is released.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a diagram of a control device according to the first embodiment is shown in FIG. The engine 1 includes a rotation sensor 2 for measuring a rotation speed N of the engine 1, a water temperature sensor 3 for measuring a cooling water temperature T of the engine 1, and a rotation speed N and a water temperature sensor 3 for the engine 1 measured by the rotation sensor 2.
The controller 4 outputs a signal in accordance with the measured cooling water temperature T of the engine 1 and a signal output from the controller 4. In response to the signal, each of the cylinders 1 a of the engine 1 is input.
And a fuel injector 5 which makes it possible to adjust the fuel injection to the fuel injector.

The fuel injector 5 includes a common rail 5a for accumulating high-pressure fuel, a nozzle 5b for introducing fuel from the common rail 5a into each cylinder 1a and injecting the fuel into each cylinder 1a, and a nozzle 5b from the common rail 5a. And an electromagnetic valve 5c that can be opened and closed freely. The solenoid valve 5c receives a signal output from the controller 4 and intermittently switches between the common rail 5a and the nozzle 5b in response to the signal, so that the injection amount and the injection pattern of the fuel injected from the nozzle 5b can be adjusted. .

The controller 4 controls the fuel injection amount and the fuel injection pattern by giving a signal to the fuel injector 5 to open and close each solenoid valve 5c. As a result, the elapsed time t from the time of the complete explosion becomes the first time corresponding to the water temperature T of the engine 1.
Until the predetermined time t1, the engine speed is changed to the first predetermined engine speed N1 corresponding to the engine water temperature T.
The fuel injection amount is adjusted to regulate as follows. At the same time, until the elapsed time t from the time of the complete explosion reaches a second predetermined time t2 corresponding to the engine water temperature T, the fuel injection pattern is split fuel injection, and after the second predetermined time t2, only the main injection is performed. Fuel injection pattern. The controller 4 also has an accelerator operating means 10 which normally receives the operation of the accelerator operating means 10 and gives a signal to the fuel injector 5 so as to obtain a desired engine rotational speed. The control for adjusting is performed. However, until the first predetermined time t1 elapses from the time of the complete explosion, the above-described control for regulating the rotation speed has priority over the control by operating the accelerator operation means 10. The specific processing procedure is as follows.

The processing procedure of the controller 4 in the first embodiment will be described based on a control flowchart shown in FIG. In step S1, which is an initial state, the controller 4 gives a signal to the fuel injector 5 so that the rotation speed N of the engine 1 is not regulated (control of only accelerator operation), and the fuel injection pattern is limited to main injection only. To step S2. Next, in step S2, the rotation speed N detected by the rotation speed sensor 2 is compared with zero. The formula "N
If> 0 "is true, it is determined that the engine 1 is in normal operation, and the control is terminated by maintaining the initial state.
If ">0" is false, it is determined that the engine 1 is stopped, and the process proceeds to step S3.

In step S3, the controller 4 determines a first predetermined time t according to the water temperature T of the engine 1 at this time.
1. Second predetermined time t2 and first predetermined engine speed N
1 is calculated, and the value of the elapsed time t is reset to zero. Here, the first predetermined time t1 corresponding to the water temperature T, the second predetermined time t1,
The values of the predetermined time t2 and the first predetermined engine rotation speed N1 are stored in, for example, the controller 4 in the form of a control map. The higher the water temperature T, the shorter the first predetermined time t1 and the second predetermined time t2, and the first predetermined engine speed N1 is set to be higher, and the second predetermined time t2 is longer than the first predetermined time t1. Set to be. Further, in step S3, the controller 4 gives a signal to the fuel injector 5 to regulate the rotation speed N of the engine 1 to a first predetermined rotation speed N1 or less, and sets the fuel injection pattern to split fuel injection. After this, the process moves to step S4. In step S4, the rotational speed N is compared with a second predetermined engine rotational speed N2 stored in advance. If the expression “N> N2” is true, it is determined that the engine 1 has completely exploded, and the process proceeds to step S5. If the expression “N> N2” is false, it is determined that the engine 1 has not yet been completely exploded. Returning to S3, steps S3 and S4 are repeated until the expression "N>N2" becomes true.

In step S5, 1 is added to the value of the elapsed time t, and the process proceeds to step S6. In step S6, the elapsed time t is compared with a first predetermined time t1. The formula “t> t
If “1” is false, the process returns to step S5, and the expression “t> t1”
Are repeated until the value becomes true (timer function). If the expression “t> t1” is true, the process proceeds to step S7, where the controller 4
To remove the restriction that the engine speed N is set to be equal to or lower than the first predetermined speed N1. After that, the process moves to step S8.

In step S8, the elapsed time t is compared with a second predetermined time t2. If the expression “t> t2” is false, the process returns to step S5, and the processes of steps S5 and S6 are repeated until the expression “t> t2” becomes true (timer function). If the expression “t> t2” is true, the process proceeds to step S9, where the controller 4 supplies a signal to the fuel injector 5 to stop the split fuel injection, and sets the fuel injection pattern to include only the main injection. After this, the control ends.

According to the control of the first embodiment, when the engine 1 is started, the controller 4 completes the engine 1 when the rotation speed N of the engine 1 rises from zero and exceeds the second predetermined rotation speed N2. Consider it as an explosion. And
Until the first predetermined time t1 has elapsed from the time of the complete explosion, the fuel injection from the nozzle 5b is performed at the engine speed N
Is limited to a first predetermined engine speed N1 or less. Then, the first predetermined time t1
From the time when the second predetermined time t2 elapses to the time when the second predetermined time t2 elapses.
The split fuel injection is performed according to the operation of “0”. That is, the end of the split fuel injection is later than the release of the restriction on the rotation speed. The lower the cooling water temperature T at the time of the complete explosion,
Since the predetermined engine rotation speed N1 is low and the first predetermined time t1 is long, the warm-up operation is performed at a lower rotation speed for a longer period of time when the engine 1 is at a lower temperature where lubricating oil does not easily flow to each part of the engine. Is done.

Next, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. FIG. 3 shows a diagram of a control device according to the second embodiment. The difference from the first embodiment is that a hydraulic pressure sensor 6 that measures the lubricating oil pressure of the engine 1 (for example, the oil pressure in an oil passage that supplies lubricating oil to a bearing) P
(May be a hydraulic switch) in the engine 1, and the controller 4 outputs a signal according to the lubricating oil pressure P of the engine 1 measured by the oil pressure sensor 6 and the cooling water temperature T of the engine 1 measured by the water temperature sensor 3. is there. The specific processing procedure is as follows.

The processing procedure of the controller 4 in the second embodiment will be described with reference to the control flowchart shown in FIG. In step S1, which is an initial state, the controller 4 gives a signal to the fuel injector 5 so that the rotation speed N of the engine 1 is not regulated (control of only accelerator operation), and the fuel injection pattern is limited to main injection only. To step S2a. Next, in step S2a, the lubricating oil pressure P detected by the oil pressure sensor 6 is compared with zero, that is, the atmospheric pressure. If the expression “P> 0” is true, it is determined that the engine 1 is in normal operation, and the control is terminated by maintaining the initial state. If the expression is false, it is determined that the engine 1 is stopped and step S3a is performed. Move to.

In step S3a, the controller 4 sets a first predetermined time t according to the water temperature T of the engine 1 at this time.
1. Second predetermined time t2 and first predetermined engine speed N
1 is calculated, and the value of the elapsed time t is reset to zero. Here, the first predetermined time t1 corresponding to the water temperature T, the second predetermined time t1,
The values of the predetermined time t2 and the first predetermined engine rotation speed N1 are stored in, for example, the controller 4 in the form of a control map. The higher the water temperature T, the shorter the first predetermined time t1 and the second predetermined time t2, and the first predetermined engine speed N1 is set to be higher, and the second predetermined time t2 is longer than the first predetermined time t1. Set to be. Further, in step S3a, the controller 4 gives a signal to the fuel injector 5 to regulate the engine speed N to the first predetermined speed N1 or less, and sets the fuel injection pattern to split fuel injection. After this, step S
4a. In step S4a, the lubricating oil pressure P is compared with a predetermined engine lubricating oil pressure P1 stored in advance. If the expression “P> P1” is true, it is determined that the engine 1 has completely exploded, and the process proceeds to step S5. If false, it is determined that the engine 1 has not been completely exploded, and the process returns to step S3a. Since the control from step S5 is the same as in the first embodiment, the description is omitted.

According to the control of the second embodiment, when the engine 1 is started, the controller 4 completes the explosion of the engine 1 when the lubricating oil pressure P of the engine 1 rises from zero and exceeds a predetermined engine lubricating oil pressure P1. Consider time. Until the first predetermined time t1 has elapsed since the time of the complete explosion, the fuel injection from the nozzle 5b is a split fuel injection that regulates the engine speed N to the first predetermined engine speed N1 or less. . Then, the first predetermined time t
From the time point when 1 elapses to the time point when the second predetermined time t2 elapses, the fuel injection from the nozzle 5b is a split fuel injection corresponding to the operation of the accelerator operation means 10. That is, the end of the split fuel injection is later than the release of the restriction on the rotation speed. The lower the cooling water temperature T at the time of the complete explosion,
Since the predetermined engine rotation speed N1 is lower, the lower the temperature at which the lubricating oil is less likely to flow to each part of the engine, the lower the temperature.
The engine 1 is warmed up at a lower rotation speed.

In the first and second embodiments, the lubricating oil temperature may be used instead of the cooling water temperature as control data. In this case, an oil temperature sensor for measuring the lubricating oil temperature is provided instead of the water temperature sensor for measuring the cooling water temperature. The fuel injector is not limited to the common rail type as long as the split fuel injection can be freely performed.

As described above with reference to the two embodiments,
ADVANTAGE OF THE INVENTION According to this invention, in the warm-up operation at the time of starting of the engine which uses both the rotation speed regulation and the split fuel injection, the end of the split fuel injection is performed after the completion of the warm-up and after the release of the rotation speed regulation. . Therefore, a sharp increase in the rotation speed due to the accelerator operation at the time when the restriction on the rotation speed is released is suppressed by the split fuel injection, and the operability is improved. Further, as the temperature such as the cooling water temperature or the lubricating oil temperature is lower, the upper limit value of the regulated engine rotation speed is lower, and the regulated time is longer. The more the engine is warmed up for a longer time at a lower speed,
It is more strictly protected from troubles such as bearing seizure.

[Brief description of the drawings]

FIG. 1 is a diagram of a control device according to a first embodiment.

FIG. 2 is a flowchart according to the first embodiment.

FIG. 3 is a diagram of a control device according to a second embodiment.

FIG. 4 is a flowchart according to a second embodiment.

[Explanation of symbols]

1 ... engine, 2 ... rotation speed sensor, 3 ... water temperature sensor,
4 Controller, 5 Fuel injector, 5b Nozzle, 6
... oil pressure sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 314 F02D 45/00 314B F02N 11/08 F02N 11/08 PF term (Reference) 3G084 AA01 BA03 BA11 BA13 BA15 CA01 CA02 DA11 DA19 EA07 EA11 EC01 EC04 FA00 FA20 FA33 3G301 HA02 HA04 JA00 JA04 KA01 KA05 MA23 MA27 NC04 NE17 NE19 NE23 PE00Z PE01Z PE08Z

Claims (4)

[Claims] 1. A fuel injection control method according to claim 1, wherein the fuel injection at a predetermined time after the complete explosion of the engine is defined as a split fuel injection, and the fuel injection after a predetermined time is determined as a normal fuel injection based on an external fuel increase / decrease signal. The predetermined time is divided in advance into a first half, which is longer as the engine cooling water temperature is lower, and a second half following the first half, and a predetermined engine rotation speed is predetermined for each engine cooling water temperature, and the split fuel injection in the first half is performed at a predetermined time. A fuel injection control method for an engine, characterized in that the injection is maintained at or below the engine speed, and the split fuel injection in the latter period is an injection based on an external fuel increase / decrease signal. 2. The fuel injection control method for an engine according to claim 1, wherein the engine coolant temperature is an engine lubricating oil temperature. 3. The fuel injection control device according to claim 1, wherein the fuel injection at a predetermined time after the complete explosion of the engine is a split fuel injection, and the fuel injection after a predetermined time elapses is a normal fuel injection based on a fuel increase / decrease signal from the outside. The predetermined period is divided into a first period, which is longer as the engine cooling water temperature is lower, and a second period following the previous period, and the first and second periods, and a predetermined engine rotation speed predetermined for each engine cooling water temperature are stored. Receiving the cooling water temperature of the engine at or immediately before the complete explosion of the engine, reading the first half, the second half, and the predetermined engine speed of the length corresponding to the cooling water temperature from the memory, and reading the fuel in the first half. From the injection nozzle (5b)
Split fuel injection is performed to maintain the engine speed at or below the predetermined value, and in the later stage of reading, the fuel injection nozzle (5b)
Performs split fuel injection based on an external fuel increase / decrease signal, and after a predetermined time has elapsed, the fuel injection nozzle (5
(b) a fuel injection control device for an engine, which performs normal fuel injection based on a fuel increase / decrease signal from the outside; 4. The fuel injection control device for an engine according to claim 3, wherein the cooling water temperature of the engine is a lubricating oil temperature of the engine.