JP4479909B2 - Idle speed control device for internal combustion engine - Google Patents

Description

  The present invention relates to an idle speed control device in a direct injection internal combustion engine that performs multi-stage injection of main injection and post injection.

There is an internal combustion engine that performs so-called multistage injection in which one or more post injections are performed after the main injection in order to raise the temperature of the exhaust gas.
In this post-injection, the combustion stability is maintained by the combustion of the main injection or the immediately preceding post-injection.
In an internal combustion engine that performs multi-stage injection in this way, during normal driving, the fuel injection amounts of main injection and post injection are prescribed injection amounts determined from the engine speed, accelerator opening, etc. Rotational speed feedback control is performed to set the engine speed to the target speed. The feedback control is conventionally performed by increasing or decreasing the fuel injection amount of the main injection that greatly contributes to torque.

  However, for example, if the fuel injection amount of the main injection is reduced in order to reduce the actual rotational speed of the internal combustion engine, the post-injection combustion that has maintained the combustion stability by the combustion of the main injection becomes unstable, and the internal combustion engine There arises a problem that the rotational stability of the is deteriorated. If the post-injected fuel is not burned, there is a problem that it is discharged into the atmosphere as unburned fuel.

Therefore, a technique for controlling not only the main injection amount but also the post-injection time during idling is disclosed (see Patent Document 1).
JP 2002-235590 A

  However, when the actual rotational speed of the internal combustion engine is reduced as in the technique disclosed in Patent Document 1, it is possible to reduce the torque and reduce the actual rotational speed by retarding the post injection timing. It is possible, however, post-injection combustion stability is maintained by the combustion of the main injection, so that the post-injection combustion stability decreases as the timing of the main injection and post-injection increases. The problem of increased fuel consumption arises.

In addition, when two or more post injections are performed, it is necessary to change the timing of all the posts after the delayed post injection, and the control may be extremely complicated.
The present invention has been made to solve such a problem, and an object of the present invention is to improve rotational stability and suppress torque fluctuations in idling speed control of a multistage injection internal combustion engine. Another object of the present invention is to provide an idling engine speed control device for an internal combustion engine that can maintain the exhaust gas temperature at a high temperature, suppress the discharge of unburned fuel, and suppress the deterioration of exhaust gas and fuel consumption.

In order to achieve the above object, in the idling engine speed control device for an internal combustion engine according to claim 1, the internal combustion engine in which fuel injection that can directly inject fuel into the combustion chamber performs fuel injection that can contribute to torque twice or more. An engine lower limit injection amount setting that sets a minimum fuel injection amount required for stable combustion of fuel injected in the next fuel injection for each fuel injection injected by the fuel injection means And idle speed control means for performing feedback control so that the actual rotational speed of the internal combustion engine becomes a target rotational speed when the internal combustion engine is idle, the idle rotational speed control means includes the target rotational speed and In order to reduce the actual rotational speed, the fuel injection amount is greater than the lower limit injection amount set by the lower limit injection amount setting means, and contributes to torque among the fuel injections Greatest advances the fuel injection angle side to lower the actual rotation speed by reducing the amount of fuel injection in a large range from the following injection amount, when it is necessary to further decrease the actual rotational speed, it reduced the amount of fuel injection When the fuel injection is less than the lower limit injection amount, the fuel is injected in the range larger than the lower limit injection amount in order from the fuel injection on the advance side that is larger than the lower limit injection amount and then has the largest contribution to torque. It is characterized by reducing the actual rotation speed by reducing the injection amount .

That is, in a multi-stage injection internal combustion engine in which fuel injection that can contribute to torque is performed twice or more, the minimum fuel injection amount required for stable combustion of the fuel injected in the next fuel injection is set for the fuel injection When the internal combustion engine is idling, the torque is reduced by reducing the fuel injection amount of the advance side fuel injection that has the largest contribution to the torque among the fuel injection amounts that are larger than the lower limit injection amount. If it is necessary to lower the engine speed and further reduce the engine speed, the target engine speed can be further reduced by reducing the torque by further reducing the torque by reducing the fuel injection amount of the fuel injection on the advance side where the torque contribution is the second largest. And

  According to a second aspect of the present invention, there is provided an idling engine speed control device for an internal combustion engine according to the first invention, wherein when the idling engine speed control means reduces the actual engine speed to obtain the target engine speed, When the fuel injection amount reaches the lower limit injection amount, the actual rotation speed is reduced by reducing the fuel injection amount from the most retarded fuel injection among the fuel injections.

That is, when the actual engine speed is further reduced when the fuel injection amount of all fuel injections reaches the lower limit injection amount during idling, the fuel injection amount of the most retarded fuel injection is set to maintain combustion stability. The rotational speed is reduced by reducing the lower injection amount below the lower limit.
According to a third aspect of the present invention, there is provided an idle speed control device for an internal combustion engine according to the first or second aspect, wherein the idle speed control means fixes each fuel injection timing of the fuel injection.

That is, the fuel injection timing is fixed during idling, and the rotational speed is controlled by adjusting only the fuel injection amount.
According to a fourth aspect of the present invention, there is provided an idle speed control device for an internal combustion engine according to the first or second aspect, wherein the idle speed control means fixes each fuel injection interval of the fuel injection.

  That is, the engine speed is controlled by fixing the fuel injection interval during idling and adjusting only the fuel injection amount.

According to the idling engine speed control device for an internal combustion engine according to claim 1 of the present invention using the above means, in the multistage injection internal combustion engine, it is the minimum necessary for stable combustion of the fuel injected in the next fuel injection. set the lower limit injection amount, to reduce the actual rotational speed from the idling torque contribution is greater the advance side of the fuel injection to thereby reduced the amount of fuel injection in a large range from the lower limit injection amount, further reduce the actual rotational speed If there is a need to be, then from the fuel injection contribution of a large advance side of the torque during idling in Rukoto reduce the amount of fuel injection in the order, of the fuel injection without consuming useless fuel injection combustion stability ensured, Shinano maintain the fuel injection exhaust gas Atsushi Nobori a large contribution retard side can reduce the number et rotation of.

As a result, the rotational stability in the rotational speed control during idling can be improved and torque fluctuations can be suppressed, the exhaust temperature can be maintained at a high temperature, and the discharge of unburned fuel can be suppressed to reduce exhaust gas and fuel consumption. Deterioration can also be suppressed.
According to the idling engine speed control device for an internal combustion engine according to claim 2, even when the fuel injection amount of all fuel injections reaches the lower limit injection amount during idling, the fuel injection amount of the most retarded fuel injection is set to the lower limit. By reducing the injection amount below the injection amount, it is possible to further reduce the actual rotational speed while suppressing deterioration in combustion stability.

According to the idling engine speed control device for an internal combustion engine according to the third aspect of the present invention, since the fuel injection timing is fixed during idling and only the fuel injection amount is adjusted to control the engine speed, the engine speed can be easily controlled.
According to the idling engine speed control device for an internal combustion engine according to claim 4, the fuel injection interval is fixed during idling, and only the fuel injection amount is adjusted to control the engine speed, so that the first fuel injection that can contribute to torque Even when the timing changes, it is possible to make it easy to change the fuel injection timing thereafter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of an idling engine speed control device for an internal combustion engine according to the present invention. With reference to FIG. 2, fuel during normal operation of the idling engine speed control device for an internal combustion engine according to the present invention. An injection timing chart is shown.
As shown in FIG. 1, the engine 1 (internal combustion engine) is a common rail type diesel engine. Specifically, the high pressure fuel accumulated in the common rail is supplied to the fuel injection valve 2 (fuel injection means) of each cylinder. The fuel injection valve 2 can be injected into the combustion chamber 4 of each cylinder at the injection timing and the injection amount.

  Each cylinder of the engine 1 is provided with a piston 6 that can slide up and down, and the piston 6 is connected to a crankshaft 10 via a connecting rod 8. Further, a flywheel 12 is provided at one end of the crankshaft 10, and a crank angle sensor 14 that detects the rotational speed of the crankshaft 10 is provided in the flywheel 12.

A cooling water passage 16 through which the cooling water passes is formed around each cylinder, and the engine 1 is provided with a cooling water temperature sensor 18 for detecting the temperature of the cooling water.
An intake passage 20 and an exhaust passage 22 communicate with the combustion chamber 4.
The intake passage 20 is provided with an intake valve 24 that communicates and shuts off the combustion chamber 4 and the intake passage 20, and the exhaust passage 22 is an exhaust valve that communicates and shuts off the combustion chamber 4 and the exhaust passage 18. 26 is provided.

The vehicle is provided with an external load device 28 such as an air conditioner driven by the engine 1, and the external load device 28, the fuel injection valve 2, the crank angle sensor 14, and other various devices and various sensors are ECUs. The electronic control unit 30 is electrically connected to the ECU 30, and the ECU 30 controls various devices based on information from various sensors.
For example, when the engine 1 is running normally, the ECU 30 controls the fuel injection valve 2 by setting the fuel injection amount based on the engine speed and the accelerator opening. In the present embodiment, as shown in FIG. 2, the main injection injected immediately after the top dead center (TDC) of the expansion stroke, three post injections A, B, C for injecting additional fuel after the main injection, and It is assumed that pilot injection multistage injection is performed before main injection. Note that the fuel injection timings of the post injections A, B, and C are fixed, and the specified fuel injection amount is set in advance. Further, it is assumed that pilot injection does not contribute to torque.

Further, when the engine 1 is idling, the ECU 30 performs feedback control in an idle speed control unit 30a (idle speed control means) provided in the ECU 30 so as to maintain the actual speed of the engine 1 at the target speed. Do.
Specifically, referring to FIG. 3, a block diagram shows an internal configuration of the idle speed control unit 30a of the ECU 30 of the internal combustion engine idle speed control apparatus according to the present invention. The input / output relationship of the control unit 30a will be described.

First, when the ECU 30 detects the idle operation state of the engine 1, the idle rotation speed control unit 30a inputs the crankshaft rotation speed data detected by the crank angle sensor 14 to the actual rotation speed detection unit 32, and the actual rotation speed. In the detection unit 32, the actual rotational speed of the engine 1 is calculated.
In addition, load data of the external load device 28 such as an air conditioner and cooling water temperature data detected by the cooling water temperature sensor 18 are input to the target rotation number setting unit 34, and the target rotation number setting unit 34 loads the load data and cooling water. A target rotation speed corresponding to the temperature data is set.

The actual rotational speed data calculated by the actual rotational speed calculation unit 32 and the target rotational speed data set by the target rotational speed setting unit 34 are input to the rotational speed comparison unit 36, and the actual rotational speed comparison unit 36 The rotation speed is compared with the target rotation speed.
On the other hand, the coolant temperature data detected by the coolant temperature sensor 18 is also input to the lower limit injection amount setting unit 34 (lower limit injection amount setting means). In the post-injection, a lower limit injection amount that is a minimum fuel injection amount at which the next injection is stably burned is set.

The lower limit injection amount data set by the lower limit injection amount setting section 38 and the comparison result data of the rotation speed comparison section 36 are input to the fuel injection situation determination section 40, and the fuel injection situation determination section 40 compares the rotation speed. Based on the result data, the state of fuel injection injected by the fuel injection valve 2 is determined using the input lower limit injection amount data.
Subsequently, the determination result in the fuel injection situation determination unit 40 is input to the fuel injection amount setting unit 42, and the fuel injection amount setting unit 42 determines the contribution ratio of the main injection and each post injection to the torque based on the determination result. A corresponding fuel injection amount is set.

Then, the fuel injection amount set by the fuel injection amount setting unit 42 is injected into the combustion chamber 4 by the fuel injection valve 2.
The operation of the idling engine speed control apparatus for an internal combustion engine according to the present invention constructed as above will be described below.
FIGS. 4 to 6 are flowcharts showing an idle speed control routine executed by the idle speed control device for an internal combustion engine of the present invention. FIG. 7 shows an idle speed control of the internal combustion engine according to the present invention. A fuel injection timing chart in each situation of the apparatus is shown, and will be described based on the flowchart and the timing chart.

First, when the ECU 30 detects an idle state of the engine 1, the engine speed calculation unit 32 calculates the actual engine speed of the engine 1 in step S1.
Subsequently, in step S2, the target rotational speed setting unit 34 sets a target rotational speed.
In the next step S3, the lower limit injection amount setting unit 38 sets the lower limit injection amounts of the main injection and the post injections A and B, respectively.

In step S4, it is determined whether or not the actual rotational speed calculated in step S1 in the rotational speed comparison unit 36 is smaller than the target rotational speed set in step S2. If the determination result is false (No), that is, if the actual rotational speed is greater than the target rotational speed and control is performed to reduce the actual rotational speed, the process proceeds to step S10.
In step S10, the fuel injection state determination unit 40 determines whether or not the fuel injection amount of the main injection is larger than the lower limit injection amount of the main injection set in step S3. If the determination result is true (Yes), the process proceeds to step S11.

In step S11, as shown by a solid line arrow in FIG. 7A, the fuel injection amount setting unit 42 sets a decrease amount of the fuel injection amount according to the contribution ratio to the torque of the main injection to be larger than the lower limit injection amount. The fuel injection amount calculated by the range and the fuel injection amount of the main injection reduced by the reduction amount is set.
On the other hand, if the determination result in step S10 is false (No), that is, if the fuel injection amount of the main injection is less than or equal to the lower limit injection amount, the process proceeds to step S12.

In step S12, it is determined whether or not the fuel injection amount of the post injection A injected next to the main injection is larger than the lower limit injection amount of the post injection A. If the determination result is true (Yes), the process proceeds to step S13.
In step S13, as shown by the solid line arrow in FIG. 7B, the reduction amount of the fuel injection amount is calculated in a range larger than the lower limit injection amount according to the contribution ratio of the post injection A to the torque, and the reduction amount A fuel injection amount is set by reducing the fuel injection amount of the minute post-injection A.

On the other hand, if the determination result in step S12 is false (No), that is, if the fuel injection amount of the post injection A is less than or equal to the lower limit injection amount, the process proceeds to step S14.
In step S14, it is determined whether or not the fuel injection amount of the post injection B injected after the post injection A is larger than the lower limit injection amount of the post injection B. If the determination result is true (Yes), the process proceeds to step S15.

In step S15, as shown by the solid line arrow in FIG. 7C, the reduction amount of the fuel injection amount is calculated in a range larger than the lower limit injection amount according to the contribution ratio of the post injection B to the torque. A fuel injection amount obtained by reducing the fuel injection amount of the minute post-injection B is set.
On the other hand, if the determination result in step S14 is false (No), that is, if the fuel injection amount of the post injection B is less than or equal to the lower limit injection amount, the process proceeds to step S16.

In step S16, it is determined whether the fuel injection amount of the post injection C that is injected next to the post injection B is greater than 0, that is, whether the post injection C is being performed. If the determination result is true (Yes), the process proceeds to step S17.
In step S17, as indicated by the solid line arrow in FIG. 7D, a decrease amount of the fuel injection amount corresponding to the contribution ratio of the torque of the post injection C is calculated, and the fuel injection amount of the post injection C corresponding to the decrease amount is calculated. Set the reduced fuel injection amount.

On the other hand, if the determination result in step S16 is false (No), that is, if the fuel injection amount of the post injection C is 0, that is, if the post injection C is not performed, the process proceeds to step S18.
In step S18, it is determined whether or not the fuel injection amount of post injection B is greater than zero. If the determination result is true (Yes), that is, if the fuel injection amount is greater than 0 and the post-injection B equal to or lower than the lower limit injection amount is performed based on the determination result in step S14, the process proceeds to step S19. move on.

In step S19, as indicated by the solid line arrow in FIG. 7 (e), a reduction amount of the fuel injection amount corresponding to the contribution ratio of the torque of the post injection B is calculated, and the fuel injection amount of the post injection B is calculated by the reduction amount. Set the reduced fuel injection amount.
On the other hand, when the determination result of step S18 is false (No), that is, when the fuel injection amount of post injection B is 0, that is, when post injection B is not performed, the process proceeds to step S20.

In step S20, it is determined whether or not the fuel injection amount of the post injection A is greater than zero. If the determination result is true (Yes), that is, if the fuel injection amount is greater than 0, and the post-injection A equal to or less than the lower limit injection amount is performed based on the determination result in step S12, the process proceeds to step S21. move on.
In step S21, as indicated by the solid line arrow in FIG. 7 (f), a decrease amount of the fuel injection amount corresponding to the contribution ratio of the torque of the post injection A is calculated, and the fuel injection amount of the post injection A corresponding to the decrease amount is calculated. Set the reduced fuel injection amount.

On the other hand, when the determination result of step S20 is false (No), that is, when the fuel injection amount of post injection A is 0, that is, when post injection A is not performed, the process proceeds to step S22.
In step S22, as shown by the solid line arrow in FIG. 7 (g), a reduction amount of the fuel injection amount corresponding to the contribution ratio of the torque of the main injection is calculated, and the fuel injection amount of the main injection is reduced by the reduction amount. Set the fuel injection amount.

In step S23, the fuel injection amount set in step S11, S13, S15, S17, S19, S21, or S22 is injected from the fuel injection valve 2 into the combustion chamber 4, and the routine is exited.
If the determination result in step S4 is true (Yes), that is, if the actual rotational speed is less than the target rotational speed and control is performed to increase the actual rotational speed, the process proceeds to step S30.

In step S30, the fuel injection state determination unit 40 determines whether or not the fuel injection amount of the main injection is smaller than the lower limit injection amount of the main injection set in step S3. If the determination result is true (Yes), the process proceeds to step S31.
In step S31, as indicated by a chain line arrow in FIG. 7 (g), the fuel injection amount setting unit 42 sets the increase amount of the fuel injection amount according to the contribution ratio to the torque of the main injection to be smaller than the lower limit injection amount. The fuel injection amount calculated by the range and the fuel injection amount of the main injection increased by the increase amount is set.

On the other hand, if the determination result of step S30 is false (No), that is, if the fuel injection amount of the main injection is greater than or equal to the lower limit injection amount, the process proceeds to step S32.
In step S32, it is determined whether or not the fuel injection amount of the post injection A is smaller than the lower limit injection amount of the post injection A. If the determination result is true (Yes), the process proceeds to step S33.
In step S33, as shown by the chain line arrow in FIG. 7 (f), the increase amount of the fuel injection amount corresponding to the contribution ratio of the post injection A to the torque is calculated in a range smaller than the lower limit injection amount, and the increase amount A fuel injection amount obtained by increasing the fuel injection amount of the minute post-injection A is set.

On the other hand, if the determination result in step S32 is false (No), that is, if the fuel injection amount of the post injection A is greater than or equal to the lower limit injection amount, the process proceeds to step S34.
In step S34, it is determined whether or not the fuel injection amount of the post injection B is smaller than the lower limit injection amount of the post injection B. If the determination result is true (Yes), the process proceeds to step S35.
In step S35, as shown by the chain line arrow in FIG. 7 (e), the increase amount of the fuel injection amount corresponding to the contribution ratio of the post injection B to the torque is calculated in a range smaller than the lower limit injection amount, and the increase amount A fuel injection amount obtained by increasing the fuel injection amount of the minute post-injection B is set.

On the other hand, if the determination result in step S34 is false (No), that is, if the fuel injection amount of the post injection B is equal to or greater than the lower limit injection amount, the process proceeds to step S36.
In step S36, it is determined whether or not the fuel injection amount of the post injection C is smaller than a preset specified injection amount of the post injection C. If the determination result is true (Yes), the process proceeds to step S37.

In step S37, as indicated by a chain line arrow in FIG. 7D, an increase amount of the fuel injection amount corresponding to the contribution ratio of the post injection C to the torque is calculated, and the fuel injection amount of the post injection C corresponding to the increase amount. The fuel injection amount with increased is set.
On the other hand, if the determination result in step S36 is false (No), that is, if the fuel injection amount of the post injection C is the specified injection amount, the process proceeds to step S38.

In step S38, it is determined whether or not the fuel injection amount of the post injection B is smaller than the prescribed injection amount of the post injection B. If the determination result is true (Yes), the process proceeds to step S39.
In step S39, as indicated by a chain line arrow in FIG. 7C, an increase amount of the fuel injection amount corresponding to the contribution ratio of the post injection B to the torque is calculated, and the fuel injection amount of the post injection B corresponding to the increase amount. The fuel injection amount with increased is set.

On the other hand, if the determination result in step S38 is false (No), that is, if the fuel injection amount of the post injection B is the specified injection amount, the process proceeds to step S40.
In step S40, it is determined whether or not the fuel injection amount of the post injection A is smaller than the prescribed injection amount of the post injection A. If the determination result is true (Yes), the process proceeds to step S41.
In step S41, as indicated by a chain line arrow in FIG. 7B, an increase amount of the fuel injection amount corresponding to the contribution ratio of the post injection A to the torque is calculated, and the fuel injection amount of the post injection A corresponding to the increase amount. The fuel injection amount with increased is set.

On the other hand, if the determination result in step S38 is false (No), that is, if the fuel injection amount of the post injection A is the specified injection amount, the process proceeds to step S42.
In step S42, as indicated by a chain line arrow in FIG. 7A, an increase amount of the fuel injection amount corresponding to the contribution ratio of the torque of the main injection is calculated, and the fuel injection amount of the main injection is increased by the increase amount. Set the fuel injection amount.

In step S23, the fuel injection amount set in step S31, S33, S35, S37, S39, S41, or S42 is injected from the fuel injection valve 2 into the combustion chamber 4, and the routine is exited.
Note that in the idle speed control, all fuel injection timings are fixed.
As described above, in the engine speed control at the time of idling in the engine 1 that performs multi-stage injection that performs two or more fuel injections, when the actual engine speed is higher than the target engine speed and the actual engine speed is decreased, first the torque The fuel injection amount of the main injection that has the largest contribution to is reduced in a range larger than the lower limit injection amount, and the torque is reduced to reduce the actual rotational speed. Even when the fuel injection amount of the main injection reaches the lower limit injection amount, when the actual rotational speed needs to be reduced, the order of post injection A, post injection B, post injection C, that is, the order in which the contribution of torque is large. That is, the actual rotational speed is reduced by reducing the fuel injection amount within a range equal to or greater than the lower limit injection amount from the post-injection on the advance side.

Further, when it is necessary to reduce the actual rotational speed even when all of the main injection and the post injection reach the lower limit injection amount, the order of post injection C, post injection B, post injection A, main injection, that is, combustion For the sake of stability, the actual rotational speed is reduced by reducing the fuel injection amount from the retard side fuel injection to the range from the lower limit injection amount to zero.
On the other hand, when the actual rotational speed is lower than the target rotational speed and the actual rotational speed is increased, the flow of decreasing the actual rotational speed is returned, and first, the fuel injection on the advance side where the contribution of torque is large is changed to the lower limit injection. Secure the amount.

When the lower limit injection amount is secured for all the fuel injections, the prescribed injection amount is secured from the retarded fuel injection that greatly contributes to the exhaust gas temperature increase.
As described above, in each fuel injection, the minimum injection amount necessary for stable combustion of the fuel injected in the next fuel injection is set and the rotational speed control at idling is performed, which is useless. The rotational speed can be adjusted while ensuring the combustion stability of each fuel injection without injecting the fuel.

The exhaust gas temperature can be maintained at a high temperature by maintaining the retarded fuel injection that greatly contributes to the exhaust gas temperature increase.
Furthermore, since the fuel injection timing is fixed, the idling speed control can be easily performed.
As described above, the idling engine speed control device for an internal combustion engine according to the present invention can improve the rotation stability in the engine speed control during idling, suppress torque fluctuations, and maintain the exhaust temperature at a high temperature. In addition, the discharge of unburned fuel can be suppressed, and the deterioration of exhaust gas and fuel consumption can also be suppressed.

Although the description of the embodiment of the idling engine speed control device for an internal combustion engine according to the present invention has been completed, the embodiment is not limited to the above embodiment.
For example, in the above-described embodiment, the engine 1 is a common rail diesel engine, but may be a gasoline engine as long as it is an internal combustion engine that can directly inject fuel into the combustion chamber and perform multi-stage injection. .

In the above-described embodiment, the fuel injection timing is all fixed in the idle speed control, but the fuel injection interval after the first fuel injection that can contribute to the torque may be fixed, which contributes to the torque. Even when the obtained initial fuel injection timing changes, it is not necessary to calculate the subsequent fuel injection timing, and the control can be facilitated.
Moreover, in the said embodiment, although post injection is performed 3 times, there is no restriction | limiting in the frequency | count of the said post injection.

In the above embodiment, the main injection is performed immediately after the top dead center. However, it may be performed near the top dead center. For example, the main injection may be performed immediately before the top dead center.
Moreover, in the said embodiment, although pilot injection is performed before main injection, it is not necessary to perform the said pilot injection.
In the above embodiment, the target rotational speed is set according to the external load such as an air conditioner and the cooling water temperature, and the lower limit injection amount is set according to the cooling water temperature, but may be set according to other factors. I do not care.

1 is a schematic configuration diagram of an idle speed control device for an internal combustion engine according to the present invention. 3 is a time chart showing fuel injection during normal operation of the idling engine speed control device for an internal combustion engine according to the present invention. It is a block diagram which shows the internal structure of ECU in the idle speed control apparatus of the internal combustion engine which concerns on this invention. It is a part of flowchart which shows the control routine which ECU in the idle speed control apparatus of the internal combustion engine which concerns on this invention performs. FIG. 4 is the remaining part of the flowchart showing the control routine following FIG. 3. FIG. FIG. 4 is the remaining part of the flowchart showing the control routine following FIG. 3. FIG. It is a fuel-injection timing chart in each situation of the idle speed control apparatus of the internal combustion engine which concerns on this invention.

Explanation of symbols

1 engine (internal combustion engine)
2 Fuel injection valve (fuel injection means)
14 Crank angle sensor 16 Cooling water passage 18 Cooling water temperature sensor 28 External load device 30 ECU
30a Idle speed controller (idle speed controller)
32 actual rotation speed calculation section 34 target rotation speed setting section 36 rotation speed comparison section 38 lower limit injection amount setting section (lower limit injection amount setting means)
40 Fuel Injection Status Determination Unit 42 Fuel Injection Amount Setting Unit

Claims (4)

An internal combustion engine that performs fuel injection two or more times that can contribute to torque by fuel injection means capable of directly injecting fuel into a combustion chamber,
For each fuel injection injected by the fuel injection means, lower limit injection amount setting means for setting a minimum fuel injection amount necessary for stable combustion of fuel injected in the next fuel injection;
Idle speed control means for performing feedback control so that the actual rotational speed of the internal combustion engine becomes a target rotational speed when the internal combustion engine is idle,
When the idle speed control means decreases the actual speed to obtain the target speed,
The fuel injection amount is larger than the lower limit injection amount set by the lower limit injection amount setting means. The fuel injection on the advance side having the largest contribution to the torque among the fuel injections in the range larger than the lower limit injection amount. Decrease the injection amount to reduce the actual rotation speed ,
Further, when it is necessary to reduce the actual rotational speed, when the fuel injection with the reduced fuel injection amount falls below the lower limit injection amount, the fuel injection amount is larger than the lower limit injection amount, and then the contribution to torque is large. advance from the corner side of the fuel injection in the order, the lower limit injection amount idling speed control system for an internal combustion engine, characterized in isosamples reduce the amount of fuel injection to reduce the actual rotational speed in a large range from. When the idling engine speed control means decreases the actual engine speed to obtain the target engine speed, when all the fuel injection amounts of the fuel injection have reached the lower limit injection amount,
2. An idling engine speed control device for an internal combustion engine according to claim 1, wherein the actual engine speed is reduced by reducing the fuel injection amount from the most retarded fuel injection among the fuel injections.   The idle speed control device for an internal combustion engine according to claim 1 or 2, wherein the idle speed control means fixes each fuel injection timing of the fuel injection.   The idle speed control device for an internal combustion engine according to claim 1 or 2, wherein the idle speed control means fixes each fuel injection interval of the fuel injection.

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