JP2001173490A - Starting control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stating device for a diesel engine capable of promptly and smoothly building up an engine to improve starting performance by preventing over rich when starting the engine. SOLUTION: This starting control device for a diesel engine comprises; a cranking discriminating means 2 for discriminating whether an engine 3 is in a cranking state or not; a complete explosion discriminating means 2 for discriminating whether the engine 3 completely explode or not; an engine temperature detecting means 4 and the number of revolutions detecting means 2, 5 for respectively detecting the temperature Tw of engine cooling water and the number of revolutions Ne of the engine 3; a basic injection amount determining means 2 for determining a basic starting fuel injection amount as a stating fuel injection amount according to the detected temperature Tw of the engine cooling water and the number of revolutions Ne; and a reduction controlling means 2 for reducing the basic stating fuel injection amount according to a lapse of time, since the cranking state of the engine 3 has been judged to be completed by the cranking discriminating means 2, until the engine 3 is discriminated to be completely exploded by the complete explosion discriminating means 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start control apparatus for a diesel engine, and more particularly, to control of a fuel injection amount from a start of the engine to a complete explosion.

[0002]

2. Description of the Related Art Normally, when an internal combustion engine is started in a low temperature environment, fuel is difficult to atomize, and the air-fuel ratio of an air-fuel mixture becomes lean by adhering to an intake valve or an inner wall surface of a cylinder. In order to improve the ignition performance of the engine, the starting fuel injection amount (fuel injection amount at the time of starting) is increased. On the other hand, even if the internal combustion engine is started and a complete explosion (the state in which the engine can rotate on its own) continues to increase the starting fuel injection amount, the air-fuel ratio becomes rich. Is controlled to reduce the starting charge injection amount. As a conventional internal combustion engine start control device that performs such control, there is known a device described in Japanese Patent Application Laid-Open No. Sho 62-157246 (Japanese Patent Publication No. 7-42882). In this start control device,
During startup of the internal combustion engine, that is, when the starter motor operates, the internal combustion engine is in a cranking state (a state in which the crankshaft is forcibly driven to rotate by an external force) according to the cooling water temperature of the internal combustion engine. A starting fuel increase coefficient is determined, and the starting fuel injection amount is gradually increased according to the value. The start control device is applied to a gasoline engine. Normally, a gasoline engine starts up quickly and almost completely explodes at the same time as the end of cranking. Therefore, in the above start control device,
From the start of the engine until the complete explosion, the starting fuel injection amount is gradually increased, and for the first time after the complete explosion, the starting fuel injection amount is gradually reduced according to the post-start increasing coefficient according to the engine speed and load condition. .

[0003]

As described above, in the conventional start control apparatus, since the starting fuel injection amount is controlled to be gradually increased until the complete explosion, such control is applied to the diesel engine. Then, there is the following problem.
That is, in the case of a diesel engine, the time from the end of cranking to the complete explosion is longer than that of a gasoline engine.
If the starting fuel injection amount is gradually increased until the complete explosion, the air-fuel ratio becomes over-rich. As a result, the gradual increase in the starting fuel injection amount rather hinders the startup of the engine, and the startup of the engine is delayed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and the engine can be started quickly and smoothly by preventing over-rich when starting the engine. It is another object of the present invention to provide a diesel engine start control device capable of improving the start performance.

[0005]

A start control apparatus for a diesel engine according to the present invention is a start control apparatus for a diesel engine for controlling a starting fuel injection amount from the start of engine start to a complete explosion, Cranking determining means (EC in the embodiment (hereinafter the same in this section) for determining whether or not the engine 3 is in a cranking state;
U2, step 31 in FIG. 4, step 51) in FIG.
Complete explosion determining means (ECU 2, step 1 in FIG. 3) for determining whether the engine 3 has completely exploded, and an engine temperature for detecting the engine temperature of the engine 3 (engine cooling water temperature Tw) and the engine speed Ne, respectively. Detecting means (cooling water temperature sensor 4) and engine speed detecting means (EC
U2, crank angle sensor 5), basic injection amount determining means (ECU2) for determining a basic starting fuel injection amount as a starting fuel injection amount in accordance with the detected engine temperature and engine speed Ne, and cranking determining means From the time when it is determined that the cranking state of the engine 3 has ended to the time when it is determined by the complete explosion determining means that the engine 3 has completely exploded, by reducing the basic starting fuel injection amount according to the elapsed time. (ECU 2, steps 6 and 7 in FIG. 3)
And characterized in that:

[0006] According to this configuration, the starting fuel injection amount supplied to the diesel engine (hereinafter, simply referred to as "engine") from the start to the complete explosion is controlled as follows. That is, first, according to the engine temperature and the engine speed detected by the engine temperature detecting means and the engine speed detecting means, the basic starting fuel injection quantity is determined as the starting fuel injection quantity by the basic injection quantity determining means. This basic starting fuel injection amount is supplied to the engine until the cranking determining means determines that the cranking state of the engine has ended.
The basic start-up fuel injection amount is determined according to the elapsed time from the end of the cranking of the engine by the reduction control means from the time when the cranking state ends to the time when the complete explosion determining means determines that the engine has completely exploded. Weight loss (gradual decrease)
Is done. This makes it possible to prevent the air-fuel ratio from becoming overrich from the end of the cranking state of the engine to the complete explosion, and as a result, it is possible to smoothly increase the engine speed, Rising can be performed quickly.

In this case, the complete explosion determining means determines that the engine 3 has completely exploded when the engine speed Ne reaches a predetermined complete explosion rotational speed Nef, and determines the predetermined complete explosion rotational speed Nef.
Is preferably determined so as to increase as the engine temperature decreases.

According to this configuration, when the engine speed reaches the predetermined complete explosion speed, it is determined that the engine has completely exploded, and the complete explosion speed increases as the engine temperature decreases. It is determined. When the engine temperature is low, since the viscosity of the lubricating oil and the like is high and the friction is large, it is difficult for the engine to be in a stable rotation state, and engine stall is likely to occur. Therefore, with the above configuration, it is possible to appropriately determine that the engine has completely exploded while preventing engine stall at the time of starting.

In these cases, it is preferable that the decrease control means executes a decrease in the basic starting fuel injection amount when the engine speed Ne is equal to or higher than a predetermined lower limit speed NeLMT.

According to this configuration, when the engine speed is equal to or higher than the predetermined lower limit speed, the basic starting fuel injection amount is reduced, and conversely, the engine speed is smaller than the predetermined lower limit speed. Sometimes, the basic starting fuel injection amount is not reduced. Therefore, only after the engine rotation has increased to some extent, the basic starting fuel injection amount is reduced, so that
Engine stall can be reliably prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A diesel engine start control apparatus according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a start control device of the present embodiment, and FIG. 2 shows a relationship between components in the start control device of the present invention. As shown in these drawings, the start control device 1 includes an ECU 2 (cranking determination means, complete explosion determination means, basic injection amount determination means, and reduction control means). The fuel injection amount is controlled according to the operating state of the engine 3 (hereinafter simply referred to as “engine”), and in particular, the starting fuel injection amount is controlled as described later.

The start control device 1 further includes a cooling water temperature sensor 4.
(Engine temperature detecting means) and crank angle sensor 5
(Engine speed detecting means). The cooling water temperature sensor 4 is configured by a thermistor or the like, detects an engine cooling water temperature Tw (engine temperature) which is a temperature of the cooling water circulating in the cylinder block of the engine 3, and sends a detection signal to the ECU 2. Further, the crank angle sensor 5 outputs a CRK signal, which is a pulse signal, to the ECU 2 at every predetermined crank angle with the rotation of a crankshaft (not shown). The ECU 2 determines the engine speed Ne based on the CRK signal.

The ECU 2 has an I / O interface, C
It is configured by a microcomputer having a PU, a RAM, a ROM (all not shown), and the like. The detection signals from the cooling water temperature sensor 4 and the crank angle sensor 5 are input to the CPU after being subjected to A / D conversion and shaping by the I / O interface. When a starter motor (not shown) is operating, that is, when the engine 3 is in a cranking state, a signal indicating that fact is input to the CPU via the I / O interface. The CPU determines the operating state of the engine 3 according to these input signals, and according to the operating state, via the injector 6 according to a control program or the like stored in the ROM or data stored in the RAM. The fuel injection amount to be supplied to the engine 3 is calculated, and a drive signal based on the calculation result is output to the injector 6 to control the fuel injection amount.

Next, the control operation of the starting fuel injection amount of the engine 3 will be described with reference to FIGS. FIG. 3 shows the starting fuel injection amount (hereinafter referred to as “starting Q” as appropriate).
It is a flowchart of a process of calculating. This process
The calculation of the starting fuel injection amount from the start of the start of the engine 3, that is, from when the ignition switch is turned on to the off state until the complete explosion of the engine 3, is executed every predetermined time (for example, about 100 milliseconds). Is done. In this process, first, in step 1 (illustrated as “S1”; the same applies hereinafter), the engine speed Ne of the engine 3 is set to
It is determined whether or not the engine 3 has completely exploded by checking whether or not a predetermined complete explosion rotation speed Nef has been reached.
Specifically, the predetermined complete explosion rotation speed Nef is based on a table stored in the ROM, for example, as shown in FIG. 8, which shows a relationship between the engine cooling water temperature Tw and the predetermined complete explosion rotation speed Nef. It is determined. In the table shown in the figure, the lower the engine coolant temperature Tw, the lower the predetermined complete explosion speed N
ef is set to be high. After the start of the start of the engine 3, the engine rotation speed Ne becomes a predetermined complete explosion rotation speed Ne.
When it becomes larger than f (Step 1: No), that is, when it is determined that the engine 3 has completely exploded, the present program is ended.

On the other hand, when it is determined in step 1 that the engine 3 has not completely exploded, the engine speed Ne (rpm)
m) and the engine coolant temperature Tw (° C.), a basic start-up fuel injection amount (mm ³ ) (hereinafter, referred to as a map) as shown in FIG.
(Referred to as “basic Q”) as needed (step 2). In this map, the basic startup fuel injection amount is set to decrease as the engine speed Ne and the engine coolant temperature Tw increase.

Next, an increase flag setting process is executed (step 3). In the increasing flag setting process, as shown in FIG. 4, first, it is determined whether or not the starter motor is operating (step 31). When the starter motor is operating (step 31: Yes), the starting fuel is determined. It is determined whether the injection amount is smaller than a predetermined upper limit fuel injection amount (hereinafter, appropriately referred to as “upper limit Q”) (Step 3).
2). The predetermined upper limit fuel injection amount is an upper limit value provided to prevent an excessive increase in the starting fuel injection amount. When the starting fuel injection amount is smaller than the predetermined upper limit fuel injection amount (step 32: Yes), the increase flag is set to "1" (step 33). Also, in step 31,
If it is determined that the starter motor is not operating (step 31: No), or if the starting fuel injection amount is equal to or more than the predetermined upper limit fuel injection amount (step 32: No), the increase flag is set. Is set to "0" (step 34). After setting the increase flag to “1” or “0” as described above, an increase calculation process for calculating an increase in the starting fuel injection amount (hereinafter, appropriately referred to as “increase Q”) is executed ( Step 4).

As shown in FIG. 5, in this increase calculation processing, it is first determined whether or not the increase flag set in step 3 is "1" (step 41). When the increase flag is "1" (step 41: Ye
s), the increase Q calculated in the previous increase calculation process
It is determined whether or not (hereinafter, appropriately referred to as “previous increase Q”) is 0 (step 42). That is, it is determined whether the current increase calculation processing is the first processing or the second or later processing. When it is determined in this step 42 that the increase calculation processing is the first time (step 42: Yes), a predetermined value (hereinafter, appropriately referred to as “set increase Q”) is set as the increase Q (step 43). ).

On the other hand, in step 42, the previous increase Q
Is not 0 (Step 42: N
o) That is, when the increase calculation processing is the second or subsequent time, in step 45, it is determined whether or not one second has elapsed since the increase Q was increased. If the determination result in step 45 is No, the previous increase Q is maintained as the increase Q (step 47). On the other hand, step 45
If the determination result is Yes, a value obtained by adding the set increase Q to the previous increase Q is set as the increase Q (step 46). As described above, the increment Q is incremented by the set increment Q every one second during cranking.

In step 41, when it is determined that the increase flag is not "1" (increase flag = "0") (step 41: No), that is, when the cranking state is ended, or when the starting fuel injection amount is increased. Is larger than the upper limit fuel injection amount, the increase Q is held at the previous increase Q (step 44).

After calculating the increase Q as described above,
The amount reduction flag setting process of step 5 is executed. In this reduction flag setting process, as shown in FIG. 6, first, it is determined whether or not the starter motor is stopped (step 5).
1) When the starter motor is stopped (step 51: Yes), it is determined whether or not the engine speed Ne is equal to or higher than a predetermined lower limit speed NeLMT (step 5).
2). The predetermined lower limit rotational speed NeLMT is a lower limit value of the engine rotational speed for preventing the starting from becoming unstable by reducing the starting fuel injection amount at an excessively low rotational speed of the engine 3, for example, 500 rpm. is there.
When the engine speed Ne is equal to or higher than the predetermined lower limit speed NeLMT (step 52: Yes), the reduction flag is set to "1" (step 53). Step 5
In step 1, if it is determined that the starter motor is not stopped (step 51: No), or step 52
, The engine speed Ne is equal to a predetermined lower limit speed Ne.
If it is smaller than LMT (Step 52: No), the weight reduction flag is set to “0” (Step 54). After setting the reduction flag to “1” or “0” in this way, a reduction calculation process for calculating a reduction in the starting fuel injection amount (hereinafter, appropriately referred to as “reduction Q”) is executed ( Step 6).

As shown in FIG. 7, in this weight loss calculation processing, it is first determined whether or not the weight reduction flag set in step 5 is "1" (step 61). When the weight reduction flag is "1" (step 61: Ye
s), the weight loss Q calculated in the previous weight loss calculation process
It is determined whether or not (hereinafter, appropriately referred to as “previous decrease Q”) is 0 (step 62). That is, it is determined whether the current weight loss calculation process is the first process or the second or later process. When it is determined in this step 62 that the weight loss calculation process is the first time (step 62: Yes), a predetermined value (hereinafter, appropriately referred to as “set weight loss Q”) is set as the weight loss Q (step 63). ).

In step 61, when it is determined that the reduction flag is not "1" (reduction flag = "0") (step 61: No), that is, whether the starter motor is operating or the engine speed Ne Is larger than the predetermined lower limit rotation speed NeLMT, the reduction Q is set to 0 (step 64).

On the other hand, in step 62, the previous
Is not 0 (step 62: N
o), that is, if the weight loss calculation processing is the second or subsequent time, it is determined in step 65 whether or not one second has elapsed since the weight loss Q was increased. If the determination result in step 65 is No, the previous decrease Q is maintained as the decrease Q (step 67). On the other hand, if the result of the determination in step 65 is Yes, a value obtained by adding the above-mentioned set reduction Q to the previous reduction Q is set as the reduction Q (step 66). As described above, the reduction Q is increased by the set reduction Q every one second after the cranking ends.

After the decrease Q is calculated as described above, in step 7, the starting Q (= basic Q + increase Q-decrease Q) is calculated using the basic Q, the increase Q and the decrease Q. Then, the following limit check is performed for the calculated start Q, and the program ends. That is, the start Q is compared with the upper limit Q (step 8). If the start Q is equal to or smaller than the upper limit Q (step 8: Yes), the program is terminated as it is. If it exceeds (Step 8: N
o), an upper limit Q is set as the starting Q (step 9),
Exit this program.

FIG. 10 is obtained by the control described above.
An example of a transition according to the elapsed time of the fuel injection amount and the engine speed Ne is shown. Referring to FIG.
Before the start of the engine 3, that is, before the start of the engine 3,
The ignition switch is OFF, and the starter motor and the engine 3 are stopped. In this state, when the ignition switch is turned on (time t1), the basic Q is set as the starting Q, and the fuel corresponding to the starting Q is injected and supplied to the engine 3. Then, at time t2, the starter motor starts to operate, whereby the engine 3 is driven to rotate and enters the cranking state.

In this cranking state, step 31 of the increase flag setting process becomes Yes, and unless the start Q exceeds the upper limit Q, "1" is continuously set to the increase flag (step 33). The increase Q is gradually increased in accordance with the elapsed time. Specifically, the increase Q is
Immediately after the start of cranking, the amount is increased by the set amount Q, and thereafter, the amount is increased stepwise by the set amount Q every one second until the cranking ends. On the other hand, in the weight loss flag setting process of step 5, the weight loss flag is kept set to "0" (step 54), and accordingly, the weight loss Q is maintained at 0 (step 64). Therefore, by these processes, the starting Q becomes the sum of the substantially constant basic Q and the increase Q gradually increased in accordance with the elapsed time, and as shown in FIG. 10, until the upper limit Q is reached, that is, from time t2 to t3.
Gradually increase between. Then, the starting Q is kept at the upper limit Q until the cranking state of the engine 3 ends (time t4).

When the cranking of the engine 3 is completed (time t4), "0" is set to the increase flag in the increase flag setting process (step 3).
4) The previous increase Q is maintained as the increase Q (step 44). On the other hand, in the reduction flag setting process, the reduction flag is set to "1" unless the engine speed Ne falls below a predetermined lower limit rotation speed NeLMT (step 5).
3) Accordingly, the decrease Q is gradually increased in accordance with the elapsed time in the same manner as the increase of the increase Q described above. That is,
The weight loss Q is increased by the set weight loss Q immediately after the end of cranking, and thereafter, is increased stepwise by the set weight loss Q every one second until the complete explosion of the engine 3 ends. Accordingly, since the weight loss Q gradually increases according to the elapsed time by these processes, the starting Q becomes a value obtained by subtracting the gradually increasing weight loss Q from the sum of the substantially constant basic Q and the constant weight gain Q,
As shown in FIG. 10, when the engine speed Ne reaches a predetermined complete explosion speed Nef (Step 1: Yes),
It gradually decreases until the engine 3 completely explodes, that is, between times t4 and t5. Then, after the engine speed Ne reaches the predetermined complete explosion speed Nef (after time t5), the routine shifts to normal fuel injection amount control.

FIG. 11 shows an example of the start-up (engine speed Ne) of the engine 3 under the control of the above-described fuel injection amount (starting fuel injection amount) in comparison with the start-up of the engine under the conventional control. As shown in FIG. 3B, in the case of the conventional control, the starting fuel injection amount is not gradually reduced after the termination of the cranking state as described above, so that the air-fuel ratio becomes over-rich and the engine speed N
e cannot be raised smoothly, and the rise is slow.

On the other hand, as shown in FIG.
In the present embodiment, by the above-described control, the air-fuel ratio is prevented from becoming over-rich by gradually reducing the starting fuel injection amount according to the elapsed time from the time when the cranking state ends, and from the cranking state. Even after the termination, the engine speed Ne smoothly increases and the start-up of the engine 3 can be hastened.

Further, according to the present embodiment, the complete explosion of the engine 3 is determined by the fact that the engine speed Ne has reached a predetermined complete explosion speed Nef. The table shown in FIG. 8 determines that the engine cooling water temperature Tw is increased as the engine cooling water temperature is lower. Therefore, it is possible to appropriately determine that the engine 3 has completely exploded while preventing engine stall at the start. In addition, since the starting fuel injection amount is reduced when the engine speed Ne is equal to or higher than a predetermined lower limit speed NeLMT,
Only after the rotation of the engine 3 has increased to some extent can the engine stall be reliably prevented by reducing the basic starting fuel injection amount.

In this embodiment, when calculating the starting fuel injection amount, in step 7, the increased Q is added to the basic Q.
, And subtraction of the reduction Q, the starting fuel injection amount may be determined by multiplying the basic Q by an appropriate coefficient and increasing or decreasing this coefficient with time. Further, time t2 to t3 shown in FIG.
In the above, the starting fuel injection amount is gradually increased. However, depending on the engine to be applied, the starting fuel injection amount may be set only by the basic starting fuel injection amount when the ignition switch is turned on.

[0032]

As described above in detail, the start control apparatus for a diesel engine according to the present invention can quickly and smoothly start up the engine by preventing over-rich at the time of engine start. This has the effect that the starting performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a start control device for a diesel engine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a relationship between components of the present invention.

FIG. 3 is a flowchart showing a process of calculating a starting fuel injection amount by the starting control device of FIG. 1;

FIG. 4 is a flowchart showing an increase flag setting process.

FIG. 5 is a flowchart showing a process of calculating an increase in a starting fuel injection amount.

FIG. 6 is a flowchart showing a reduction flag setting process.

FIG. 7 is a flowchart showing a process of calculating a decrease in a starting fuel injection amount.

FIG. 8 shows a table for determining a complete explosion speed according to the temperature of engine cooling water.

FIG. 9 shows a map for determining a basic starting fuel injection amount according to an engine coolant temperature and an engine speed.

10 is a time chart showing an operation example according to the flowchart of FIG. 3, wherein (a) shows an ignition switch and a starter motor, (b) shows a fuel injection amount, and (c) shows an engine speed.

FIGS. 11A and 11B are time charts for explaining the start-up of the engine in comparison with each other, wherein FIG. 11A shows an operation example by the control of the present embodiment, and FIG. 11B shows an operation example by the conventional control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Start-up control apparatus 2 ECU (Cranking discrimination means, complete explosion discrimination means, basic injection amount determination means, reduction control means) 3 Diesel engine 4 Cooling water temperature sensor (engine temperature detection means) 5 Crank angle sensor (engine rotation number detection means) 6) Injector Tw Engine cooling water temperature (engine temperature) Ne Engine speed Nef Complete explosion speed NeLMT Lower limit speed

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 312 F02D 45/00 312Q 362 362K (72) Inventor Masaki Nishio 1-chome, Chuo, Wako, Saitama No. 4 F-term in Honda R & D Co., Ltd. (Reference) 3G084 AA01 BA13 BA29 CA01 DA09 EA11 EB08 FA20 FA33 FA38 3G301 HA02 JA03 KA01 LB11 MA11 NA08 NB12 NC04 NE08 NE17 NE19 PB03A PE01Z PE08Z

Claims (3)

[Claims] 1. A diesel engine start control device for controlling a start fuel injection amount from a start of an engine start to a complete explosion, wherein a cranking determination for determining whether or not the engine is in a cranking state. Means, complete explosion determining means for determining whether the engine has completely exploded, engine temperature detecting means and engine speed detecting means for detecting the engine temperature and engine speed of the engine, respectively, Basic injection amount determining means for determining a basic starting fuel injection amount as the starting fuel injection amount according to the engine temperature and the engine speed, and the cranking determining means determines that the cranking state of the engine has ended. Until the engine is determined to have completely exploded by the complete explosion determining means. Start control device for a diesel engine, characterized in that it comprises a reduction control means, the to lose weight in accordance with the elapsed time fuel injection quantity. 2. The complete explosion determining means determines that the engine has completely exploded when the engine speed reaches a predetermined complete explosion speed, and the predetermined complete explosion speed is determined by the engine speed. 2. The method according to claim 1, wherein the temperature is determined to increase as the temperature decreases.
2. A start control device for a diesel engine according to claim 1. 3. The fuel injection control device according to claim 1, wherein the reduction control means executes the reduction of the basic starting fuel injection amount when the engine rotation speed is equal to or higher than a predetermined lower limit rotation speed. A start control device for a diesel engine as described in the above.