JP2003328836A - Control system for compressed self-ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control system for a compressed self-ignition engine that can more effectively realize a fuel economy improvement when establishing a fixed point operation specified in a range capable of compressed self-ignition combustion. <P>SOLUTION: An ECU 50 sets an operation setting point for realizing a fixed point operation with improved fuel economy in a compressed self-ignition combustion range in dependence on an engine request load. At a generator drive state, after every given time, or the like, indicated specific fuel consumptions are computed at the operation setting point and a plurality of points about it, and the operation setting point is updated at the point of the best indicated specific fuel consumption out of the points, so that the engine is operated at an optimum fuel economy point while an engine load is maintained in a given load range near the engine request load. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a compression self-ignition engine that compresses an air-fuel mixture and causes self-ignition combustion in at least a part of an operating region.

[0002]

2. Description of the Related Art Conventionally, for example, in a gasoline engine, various techniques for performing self-ignition operation by compression heat have been studied. In such compression self-ignition operation, so-called multipoint ignition combustion with an infinite number of spark plugs is realized, so the combustion time is shorter than that by spark ignition, and with a leaner air-fuel ratio. Even if there is, stable combustion can be obtained. However, for example, Combustion Research No. 117 (P33-
As disclosed in 38), in the compression auto-ignition operation, knocking occurs on the high load side, and even if the fuel is used at a high compression ratio (for example, 17.7) with the ignitability improving fuel, the low load side. Since a misfire will occur in the area, it is difficult to achieve it only in a limited and narrow operating area. Therefore, the compression ignition engine is generally put into practical use by using the compression ignition operation together with the spark ignition operation.

In a compression self-ignition engine of this type, for example, in Japanese Patent Laid-Open No. 2001-263067, fuel is densely distributed to the cylinder exhaust side by tumble control and opening / closing timing control of intake / exhaust valves, and internal EGR gas is cylinder-distributed. Disclosed is a technique for expanding the region in which stable compression-ignition combustion is possible by distributing it to the inner exhaust side and performing stratified compression self-ignition on the in-cylinder exhaust side to improve fuel efficiency.
Further, for example, in Japanese Patent Laid-Open No. 2001-248484,
By fuel injection control, tumble control / swirl control, ignition control with multiple spark plugs, EGR control, etc., fuel consumption is improved by selectively operating in multiple combustion modes including premixed compression ignition combustion. Techniques to be achieved are disclosed.

[0004]

By the way, in order to effectively improve the fuel efficiency of a compression ignition engine, an engine that performs a fixed point operation by specifying the compression ignition engine in a region where compression ignition combustion is possible It is desirable to apply it to (engine load device). As one example, it is conceivable to employ a compression self-ignition engine as a drive engine of a generator in a series hybrid vehicle, and perform fixed point operation at a point where fuel economy is good in a preset compression self-ignition combustible region. .

However, since the point of good fuel economy may vary slightly due to individual differences of engines, changes over time, operating environment, etc., in order to achieve more effective fuel economy, such variations are also required. It is necessary to control the engine correspondingly.

The present invention has been made in view of the above circumstances, and is for a compression ignition engine that can more effectively improve fuel consumption when performing fixed point operation by specifying the compression ignition combustion region. An object is to provide a control device.

[0007]

In order to solve the above-mentioned problems, the present invention according to claim 1 provides a control device for a compression ignition engine, in which air-fuel mixture is compressed and self-ignited and burned in at least a part of an operating region. Fixed point operation control means for operating the engine at a fixed point at an operation set point set within the operation region where compression ignition combustion is possible, and the indicated fuel consumption rate at the operation set point and a plurality of points around the operation set point are obtained. Then, an operating set point updating means for updating the operating set point to the point where the indicated fuel consumption rate is the best is provided.

According to a second aspect of the present invention, there is provided a control apparatus for a compression self-ignition engine according to the first aspect of the present invention, in which engine load control is performed to control an engine load at the operation set point when the engine is operated at a fixed point. It is characterized by comprising an operation set point setting means for setting based on a command signal from the means.

According to a third aspect of the present invention, there is provided a control apparatus for a compression ignition engine according to the first or second aspect of the present invention, wherein the operation set point updating means has a plurality of preset calculation methods. From the inside, a predetermined calculation method is selected based on the operating state of the engine to calculate the indicated fuel consumption rate.

A control device for a compression self-ignition engine according to a fourth aspect of the present invention is the control device for a compression self-ignition engine according to any one of the first to third aspects, wherein a fixed point within an operating range in which the compression self-ignition combustion is possible. It is characterized in that a recovery control means is provided for performing recovery control of the engine in response to at least one of knocking, pre-ignition, and misfire during operation.

That is, according to the first aspect of the invention, when the fixed point operation control means performs the fixed point operation of the engine at the operation set point, the operation set point updating means causes the operation set point and a plurality of surrounding points to be set. Further, the fuel consumption is further improved by obtaining the indicated fuel consumption rate and updating the operation set point to the point where the indicated fuel consumption rate is the best among the above points.

According to a second aspect of the invention, in the first aspect of the invention, the operation set point when the engine is operated at a fixed point is based on a command signal from engine load control means for controlling the engine load. Set.

According to a third aspect of the present invention, in the first or second aspect of the invention, the operation set point updating means is based on the operating state of the engine from among a plurality of preset calculation methods. Then, a predetermined calculation method is selected to calculate the indicated fuel consumption rate.

Further, the invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein during the fixed point operation in the operation region in which the compression ignition combustion is possible, the recovery control means Knocking, pre-ignition, or
Recovery control corresponding to at least one of misfires is performed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 13 relate to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an engine, FIG. 2 is an explanatory diagram showing valve timing and injection timing for each operating region, and FIG. 3 is operation setting. 4 is a flowchart showing a point setting routine, FIG. 4 is a flowchart showing a first example of the illustrated fuel consumption rate calculation routine, FIG. 5 is an explanatory diagram showing the relationship between the stroke volume and the cylinder pressure, and FIG. 6 is a crank angle and stroke volume. FIG. 7 is an explanatory view showing the relationship between the fuel injection pulse width and the injector fuel injection capacity, FIG. 8 is a flowchart showing a second example of the illustrated fuel consumption rate calculation routine, and FIG. 1 is an explanatory view showing the relationship between the stroke volume and the cylinder pressure at the time of wide open throttle (WOT), FIG. 10 is a flow chart showing the selection routine of the illustrated fuel consumption rate ISFC calculation subroutine, FIG. Is an explanatory view showing the illustrated fuel consumption rate search points, FIG. 12 is a flowchart showing a recovery control routine for knocking, FIG. 13 is a flowchart showing a recovery control routine for premature ignition, and FIGS. 14 and 15 are recovery control routines for misfire. It is a flowchart.

In FIG. 1, reference numeral 1 indicates an engine,
In this embodiment, a 4-cylinder horizontally opposed engine is shown. Cylinder heads 2 are crowned on both banks of the engine 1, and the cylinder head 2 has intake ports and exhaust ports (neither shown) for each cylinder.

The intake ports are collected in the air chamber 6 via the intake manifold 5, and the upstream side of the air chamber 6 is
It is communicated with an intake passage 7 having a throttle device (not shown) interposed. Here, in the present embodiment, the throttle device is composed of an electronically controlled throttle device including a throttle valve (not shown) and a throttle actuator 8 for driving the throttle valve. Control unit (ECU) 50
Controlled by the signal from.

Further, each exhaust port has an exhaust manifold 10.
Is communicated with the exhaust pipe 11 via. An exhaust gas recirculation (EGR) passage 12 for recirculating a part of high-temperature exhaust gas to the air chamber 6 is provided in the middle of the exhaust manifold 10, and further in the middle of the EGR passage 12, an EGR rate (external EGR The EGR control valve 13 for controlling the rate is provided.

In addition, each cylinder head 2 is provided with an in-cylinder injector 15 having an injection hole at the tip facing substantially the center of the combustion chamber, corresponding to each cylinder. Further, each cylinder head 2 is provided with an ignition plug 16 which exposes a discharge electrode at the tip to a combustion chamber, corresponding to each cylinder.
These spark plugs 16 are connected to an igniter 18 via an ignition coil 17. Further, the valve operating mechanism 20 provided in each cylinder head 2 includes an ECU
A known cam variable actuator 21 capable of continuously changing the valve timing by a drive signal from 50 is provided.

The ECU 50 is mainly composed of a microcomputer, and a crank angle sensor 30, a cam angle sensor 31, a water temperature sensor 32, a knock sensor 33, etc. are connected to the input side as sensors, and An in-cylinder pressure sensor 34 attached to the representative cylinder is connected via an amplifier 35. Here, the crank angle sensor 30 is composed of an electromagnetic pickup or the like that is opposed to the crank pulley 36. In the present embodiment, protrusions having 36 teeth are provided around the crank pulley 36 at equal intervals, and the crank angle sensor 30 detects the protrusions and outputs a pulse signal each time the crankshaft rotates 10 degrees. It is like this. Further, the cam angle sensor 31 is composed of an electromagnetic pickup or the like that is opposed to the cam pulley 37.

On the output side of the ECU 50, various actuators such as the above-mentioned throttle actuator 8, EGR control valve 13, in-cylinder injector 15, igniter 18 and cam variable actuator 21 are connected.

In the engine 1 having such a configuration, the combustion modes are set according to the operating state, that is, super-lean compression ignition combustion (for example, premixed compression ignition combustion) having an air-fuel ratio and ordinary spark ignition combustion (for example, premixed compression ignition combustion). , Stratified spark ignition combustion).

That is, when the operating condition is in the operating range where premixed compression autoignition combustion is possible, the ECU 50 sets the throttle valve through the wide open throttle (WOT) through the throttle actuator 8 in order to realize premixed compression autoignition combustion. Control, and as shown in FIG. 2 (a),
The valve timing of the valve operating mechanism 20 is set to a valve timing via the cam variable actuator 21 such that the overlap period in which both the intake valve and the exhaust valve open both before and after the exhaust top dead center becomes small, and the internal EGR rate is set. To control. Furthermore, while controlling the external EGR rate through the EGR control valve 13, as shown in FIG. 2A, the fuel injection control is performed at a relatively early timing after the exhaust valve is closed. By these controls, the compression ratio is set to a relatively low level of about 13 to 16 for the premixed compression self-ignition combustion operation.

On the other hand, when the operating condition is in another operating region, the ECU 50 controls the throttle valve through the throttle actuator 8 to the throttle opening which is approximately proportional to the depression amount of the accelerator pedal in order to realize the stratified spark ignition combustion. In addition, as shown in FIG. 2B, the valve timing of the valve mechanism 20 is set via the cam variable actuator 21 to a valve timing in which the valve overlap period becomes large. Further, as shown in FIG. 2B, the fuel injection timing is, for example, the first injection injected in the first half of the compression stroke and the second injection injected in the second half of the compression stroke.
It is set to two times with injection, and fuel is injected in a distributed manner with these settings.

Next, as an example for effectively improving the fuel consumption of the compression ignition engine 1, the engine 1 will be described.
A description will be made of a case in which a vehicle is mounted on a series hybrid vehicle (not shown) and a generator (not shown) of the hybrid vehicle is driven at a fixed point as an engine load device. in this case,
A generator control unit (not shown) for controlling the generator is connected to the input side of the ECU 50, and the generator control unit represents a required load (that is, an engine required load) L0 for driving the generator. A signal is input.

When the generator is driven, the ECU 50 operates the engine 1 at a fixed point at an operation set point (fuel injection pulse width Ti = Ti0, engine speed N = N0) set in the premixed compression self-ignition combustion region. In this case, the ECU 50
When the drive of the generator is started, an operation set point for operating the engine 1 at a fixed point with good fuel efficiency in the premixed compression auto-ignition combustion region is set based on a preset map or the like. Then, the ECU 50 obtains the indicated fuel consumption rate at the operation set point and a plurality of points around it at the time of starting the driving of the generator or each time a predetermined time elapses, and operates at the point where the indicated fuel consumption rate is the best among the points. By updating the set point, while maintaining the engine load L within a predetermined load region near L0,
Optimize fuel efficiency. In addition, the ECU 50 performs recovery control for knocking, pre-ignition, misfire, and the like during fixed-point operation when they occur. That is, the ECU 5
0 has a function as fixed point operation control means, operation set point update means, and recovery control means.

The operation set point setting routine executed by the ECU 50 will be described with reference to the flowchart of FIG. This routine is executed, for example, every time a set time elapses. First, in step S101, it is determined whether or not the current routine is the first routine immediately after the start of the fixed point operation control.

When it is determined in step S101 that the current routine is not the first routine immediately after the start of the fixed point operation, the process jumps to step S104.

On the other hand, if it is determined in step S101 that this routine is the first routine immediately after the start of the fixed point operation, the process proceeds to step S102. In step S102, based on the engine required load L0 input from the generator control unit, an operation set point (Ti) for realizing a fuel-efficient fixed point operation by premixed compression self-ignition combustion is set from a preset map or the like. = Ti0, N = N
0) is set.

In the following step S103, the engine load L is set through the generator control unit so that the engine speed becomes N = N0 under the condition of the fuel injection pulse width Ti = Ti0.
Perform feedback control to finely adjust.

Then, when the engine speed N converges to N0 in step S103, the process proceeds to step S104, and the indicated fuel consumption rate ISF under the conditions of the fuel injection pulse width Ti = Ti0 and the engine speed N = N0.
Calculate C0. The illustrated fuel consumption rate ISFC0 can be calculated for all cylinders, but in the present embodiment, it is calculated only for the representative cylinder to which the in-cylinder pressure sensor 34 is attached.

The calculation of the indicated fuel consumption rate ISFC0 is performed as shown in FIG.
Alternatively, it is performed according to the illustrated fuel consumption rate calculation subroutine shown in FIG.

First, FIG. 4 will be described. As shown in FIG. 4, in this routine, first, in step S201.
Then, the intake bottom dead center of the representative cylinder is determined based on the pulse signal from the cam angle sensor 31, and the pulse signal input from the crank angle sensor 30 at the intake bottom dead center is set as the reference crank angle signal θ0. In-cylinder pressure Pi every time the crank angle signal θi is input (that is, every rotation angle of 10 degrees)
Is read twice.

In the following step S202, based on the relationship between the crank angle signal θi and the stroke volume Vi, which is obtained in advance and stored in the ECU 50 (see FIG. 6), (P0, V
0) Create a data string of (P72, V72).

In the following step S203, step S2
Based on the data string created in 02, the illustrated work amount W of one cycle in the representative cylinder of the engine 1 is calculated. As shown in FIG. 5, the indicated work amount W in this case is the compression stroke (i = 0 to 17) and the expansion stroke (i = 18 to 3).
5), the exhaust stroke (i = 36 to 53), and the intake stroke (i = 54 to 71) can be calculated by calculating the respective workloads and adding them. Is calculated by the following equation.

[0036]

[Equation 1] In the following step S204, the work rate Wr (KW) is calculated from the indicated work amount W calculated in step S203 by: Wr = (W · N) / (2 · 60 · 1000), where N is the engine speed (rpm). calculate.

In the next step S205, the injector fuel capacity Q is calculated from the relationship between the fuel injection pulse width Ti previously obtained and stored in the ECU 50 and the injector fuel injection capacity Q (mm ³ / st) (see FIG. 7). Read.

In the following step S206, step S2
From the injector fuel injection capacity Q read in 05, the fuel flow rate Qr (g / h) per unit time (h) is Qr = (N.60.Q.γ) / (2.1000) where N; engine Rotation speed (rpm) γ; Calculated by fuel specific gravity (mg / mm ³ ).

Then, in step S207, the indicated fuel consumption rate ISFC (g / KW · h) is calculated by ISFC = Qr / Wr, and then the routine ends.

Next, the second simplified illustrated fuel consumption rate calculation subroutine will be described. As shown in FIG. 8, in this routine, first, in step S301, the intake bottom dead center of the representative cylinder is determined based on the pulse signal from the cam angle sensor 31, and the crank angle sensor 30 detects the intake bottom dead center at the intake bottom dead center. The input pulse signal is used as a reference crank angle signal θ0, and the in-cylinder pressure Pi is read for one rotation each time each crank angle signal θi is input (that is, every rotation angle of 10 degrees).

In the following step S302, based on the relationship between the crank angle signal θi previously obtained and stored in the ECU 50 and the stroke volume Vi (see FIG. 6), (P0, V
0) Create a data string of (P36, V36).

In the following step S303, step S3
Based on the data string created in 02, the illustrated work amount W of one cycle in the representative cylinder of the engine 1 is calculated. Here, as shown in FIG. 9, when the throttle valve is WOT, the pumping loss of the engine 1 is considered to be substantially constant regardless of the engine output. Therefore, the ECU 5 calculates in advance the work amount (pumping loss work amount) Cp in the exhaust stroke and the intake stroke when the throttle valve is WOT.
By storing the value in 0, it is possible to simplify the calculation of the illustrated work capacity W when the throttle valve is WOT as in this example. That is, the illustrated work capacity W in this case is
As is clear from FIG. 9, the compression stroke (i = 0 to 1
7), the work in the expansion stroke (i = 18 to 35) is obtained, and the work can be calculated by subtracting the pumping work loss Cp from these, specifically, by the following formula.

[0043]

[Equation 2] Then, in steps S304 to S307, the indicated fuel consumption rate ISFC is calculated by performing substantially the same processing as steps S204 to S207 described above, and then the routine exits.

Here, the selection routine of the illustrated fuel consumption rate ISFC calculation subroutine shown in FIG. 4 or 8 will be described with reference to the flowchart of FIG.

This routine is executed in step S104 of the operation set point setting routine. First, in step S1041, the output value of the throttle opening sensor 51 (throttle opening θth) is read.

In a succeeding step S1042, it is determined whether or not the throttle opening θth is equal to or more than a predetermined value θf (θf: an opening slightly closer to the throttle than fully open).

If the throttle opening θth is less than the predetermined value θf in step S1042,
It is determined that the throttle opening θth is not fully opened (non-WOT), the process proceeds to step S1043, and the method of the above-mentioned equation 1 (FIG. 4)
After selecting, exit the routine.

On the other hand, in step S1042, if the throttle opening θth is equal to or larger than the predetermined value θf, the process proceeds to step S1044.

In step S1044, it is determined whether or not the current operation set point setting routine is the first time. If the current routine is the first time, the process proceeds to step S1045.
After selecting the method of the above-mentioned equation 2 (FIG. 8), the routine is exited.

On the other hand, if it is determined in step S1044 that the current routine is the second or subsequent routine, the process proceeds to step S1046.

In step S1046, each indicated fuel consumption rate ISFC0 calculated in the previous operation set point setting routine.
.About.ISFC4 (ISFC1 to ISFC4 will be described later), a deviation .DELTA.ISFC between the best value ISFCBEST and the second best value ISFCSECONDBEST is read, and in the subsequent step S1047, .DELTA.ISFC.ltoreq..DELTA.ISF.
Check whether it is Cf. That is, step S10
46 and step S1047, the ISF that is the basis for setting the operation set point in the operation set point setting routine.
The C calculation results are compared and contrasted to determine whether the operating set point has a delicate ISFC slope. It should be noted that ΔISFCf, which is the criterion for the delicate ISFC gradient,
Is a numerical value that is determined from pre-map data (experimental value) of the engine and installed in the ECU 50.

Then, in step S1047, Δ
If ISFC> ΔISFCf, step S1
After proceeding to 048 and selecting the method of the above-mentioned equation 2 (FIG. 8), the routine is exited. On the other hand, if ΔISFC ≦ ΔISFCf is satisfied in step S1047, the flow advances to step S1049 to select the method of Equation 1 (FIG. 4) and then exit the routine.

When the indicated fuel consumption rate ISFC0 at the operation set point is calculated in step S104 and the process proceeds to step S105, the process up to step S118 is performed to update the operation set point.

Specifically, first, by the processing from step S105 to step S116, for example, as shown in FIG. 11, (Ti1, N0), (Ti0, N1) around the operation set point (Ti0, N0). , (Ti2, N0), and (Ti0, N2) for the convenience of four points, indicated fuel consumption rate ISF
C1-ISFC4 are sequentially calculated. Note that Ti1 = Ti0−Δ
Ti, Ti2 = Ti0 + ΔTi, N1 = N0 + ΔN, N2 = N0−
Let ΔN.

That is, in step S105, the fuel injection pulse width Ti is changed from Ti0 to Ti1 and the engine load L is reduced in advance by ΔL through the generator control unit. Here, the control of the engine load L is performed in order to improve the convergence of the engine speed N in the process of step S106 described later.

In the following step S106, the engine load L is set through the generator control unit so that the engine speed becomes N = N0 under the condition of the fuel injection pulse width Ti = Ti1.
Perform feedback control to finely adjust.

When the engine speed N converges to N0 in step S106, the flow advances to step S107 to calculate the indicated fuel consumption rate ISFC1 using the indicated fuel consumption rate calculation subroutine shown in FIG. 4 or 8. .

Thereafter, step S is performed by substantially the same processing.
The indicated fuel consumption rate ISFC2 is calculated in 108 to S110, and the indicated fuel consumption rate ISFC is calculated in steps S111 to S113.
FC3 is calculated, and the indicated fuel consumption rate ISFC4 is calculated in steps S114 to S116. Note that step S11
In step 1, in order to improve the convergence of the engine speed N in step S112, control for increasing the engine load L in advance by ΔL is performed through the generator control unit.

After proceeding from step S116 to step S117, in step S117, the indicated fuel consumption rate ISFC0 at the operation set point is compared with the indicated fuel consumption rates ISFC1 to ISFC4 around it.

If it is determined in step S117 that the indicated fuel consumption rate ISFC0 at the operation set point is not the minimum, the process proceeds to step S118, and the indicated fuel consumption rates ISFC1 to ISFC4 at the surrounding points are selected. The smallest one is extracted, and the operation set point is updated to the surrounding points corresponding to the extracted indicated fuel consumption rate. Then, the process returns to step S105 to perform further update processing for the new operation set point (Ti0, N0).

On the other hand, if it is determined in step S117 that the indicated fuel consumption rate ISFC0 at the operation set point is the minimum, the operation set point update processing is terminated and the routine exits.

Next, the recovery control routine executed in response to knocking during the fixed point operation of the engine 1 within the premixed compression self-ignition combustion region will be described with reference to the flowchart of FIG. This routine is an interrupt routine executed by the ECU 50 when knocking of the engine 1 is detected by the knock sensor 33, and when the routine starts, first, step S40.
At 1, the current engine speed Nk is read.

In a succeeding step S402, a counter n for measuring the number of times the recovery process for knocking is performed is reset (n = 0), and then the step S40.
Go to 3.

In step S403, in order to suppress knocking, control is performed to reduce the fuel injection pulse width Ti by ΔTi, and control is performed to reduce the engine load L by ΔL through the generator control unit.

After the measurement counter n is incremented (n = n + 1) in the following step S404, the step S40
5, the engine speed N becomes Nk under the condition that the fuel injection pulse width Ti (= Ti-ΔTi) is constant,
Feedback control for finely adjusting the engine load L is performed through the generator control unit.

Then, in step S406, it is checked whether or not knocking is still continued, and if it is determined that knocking is eliminated, the routine exits.

On the other hand, if it is determined in step S406 that knocking is continuing, the process proceeds to step S407, and it is determined whether or not the measurement counter n has reached "10", for example. And the measurement counter n is still
If it is determined that the number has not reached 10 ", step S
Returning to 403, the above processing is repeated. On the other hand, when it is determined that the measurement counter n = 10, the engine 1 is stopped.

Next, the recovery control routine executed in response to the detection of the possibility of premature ignition during the fixed point operation of the engine 1 within the premixed compression self-ignition combustion region is shown in the flowchart of FIG. Follow the instructions below. This routine is an interrupt routine executed by the ECU 50 when the possibility of premature ignition of the engine 1 is detected. Here, the possibility of premature ignition is detected, for example, based on the output fluctuation state of the engine 1, the heat generation state, or the like. When knocking is detected at the same time when the possibility of premature ignition is detected, the above-described recovery control for knocking is preferentially executed.

When this routine starts, first, in step S501, a measurement counter for counting the number of times that pre-ignition is not detected is reset (n = 0).

In the following step S502, the intake bottom dead center of the representative cylinder is determined based on the pulse signal from the cam angle sensor 31, and the crank angle sensor 3 is detected at the intake bottom dead center.
Crank angle signal θ based on the pulse signal input from 0
When the crank angle signal θi is input, the in-cylinder pressure Pi is read from the intake bottom dead center to 20 degrees (i = 16).

In the following step S503, it is determined whether the value of Pi + 1 / Pi is, for example, 3 or more.
At present, it is determined whether pre-ignition has occurred. That is, when premature ignition is not occurring in the engine 1, the main sampling range (intake bottom dead center to BTDC20
C), the in-cylinder pressure Pi cannot change suddenly. Therefore, in the main sampling range, the cylinder pressures Pi and Pi detected every time the crank angle changes by 10 degrees.
Whether or not premature ignition is currently occurring is determined by checking whether or not the ratio to +1 is, for example, three times or more.

Then, in step S503, Pi +
If 1 / Pi <3 and it is determined that pre-ignition has not occurred, the process proceeds to step S504, and the measurement counter n
Is incremented (n = n + 1), and then step S5
Go to 05.

In step S505, it is checked whether the measurement counter n has reached "10", for example, and the measurement counter n
If it is determined that the value has not reached "10", it is determined that the possibility of premature ignition has not been resolved, and the process returns to step S502. On the other hand, when the measurement counter n has reached "10" and the pre-ignition has not been detected 10 times in a row, it is determined that the possibility of pre-ignition has been eliminated, and the routine exits.

On the other hand, in step S503, Pi + 1
If / Pi ≧ 3 and it is determined that premature ignition is currently occurring, the process proceeds to step S506.

At step S506, the current external EGR
Check whether the rate is controlled to "0" and check the external EGR
When the rate is not 0, the process proceeds to step S507, the external EGR rate is reduced by a predetermined amount to eliminate the premature ignition, and then the process returns to step S501.

On the other hand, in step S506, the external EG
If it is determined that R ratio = 0, step S50
Go to 8.

In step S508, it is checked whether or not the valve overlap period is "0". If the valve overlap period ≠ 0, the process proceeds to step S509, in which the negative ignition is canceled in order to eliminate the premature ignition. After the valve overlap period is reduced by a predetermined amount to reduce the internal EGR rate, the process returns to step S501.

On the other hand, when it is determined in step S508 that the valve overlap period = 0,
Stop the engine.

Next, the recovery control routine executed in response to the detection of the possibility of misfire during the fixed point operation of the engine 1 within the premixed compression self-ignition combustion region is shown in the flowcharts of FIGS. Follow the instructions below. This routine is an interrupt routine executed by the ECU 50 when the possibility of misfire of the engine 1 is detected. Here, the possibility of misfire is detected based on, for example, the output fluctuation state of the engine 1 and the heat generation state. If knocking is detected at the same time when the possibility of misfire is detected, the above-described recovery control for knocking is preferentially executed.

When this routine starts, first, in step S601, a measurement counter for counting the number of times misfire is not detected is reset (n = 0).

In the following step S602, the intake bottom dead center of the representative cylinder is determined based on the pulse signal from the cam angle sensor 31, and the crank angle sensor 3 is detected at the intake bottom dead center.
Crank angle signal θ based on the pulse signal input from 0
When the crank angle signal θi is input, the in-cylinder pressure Pi is read for one rotation.

In the following step S603, step S6
The maximum value Pmax is selected from the in-cylinder pressures Pi at each crank angle read in 02.

In a succeeding step S604, it is determined whether or not a misfire is currently occurring depending on whether or not the maximum value Pmax of the selected in-cylinder pressure is equal to or less than the threshold value Pfix. Here, the threshold Pfix is Pfix = Pm + ΔP, where Pm; Pm at the time of motoring with the throttle valve WOT
ax (experimental value) ΔP; it is set by a predetermined value (margin).

Then, in step S604, Pma
If x> Pfix and it is determined that no misfire is detected, the process proceeds to step S605, the measurement counter n is incremented (n = n + 1), and then step S606.
Proceed to.

In step S606, it is checked whether or not the measurement counter n has reached "10", and the measurement counter n
If it is determined that the number has not reached "10", it is determined that the possibility of misfire has not yet been resolved and step S
Return to 602. On the other hand, when the measurement counter n has reached “10” and no misfire is detected 10 times in a row, it is determined that the possibility of misfire has been eliminated, and the routine exits.

On the other hand, in step S604, Pmax
If ≦ Pfix and it is determined that a misfire is currently occurring, steps S607 to S613 are executed to take measures to increase the engine load set point in small steps. When the misfire determination is made even after performing this measure 10 times, the process proceeds to step S614.

Then, in order to shift to stratified spark ignition combustion,
The spark ignition control is started (step S614), and the fuel injection pulse width Ti is increased by ΔTi (step S61).
5) After changing the fuel injection timing in the latter half of the compression stroke (step S616), the process proceeds to step S617.

In step S617, under the condition that the fuel injection pulse width Ti (= Ti + ΔTi) is constant, feedback control is performed to finely adjust the engine load L through the generator control unit so that the engine speed N becomes N0.

Then, in step S618, the measurement counter n is reset (n = 0), and in step S619, the cylinder pressure Pi for each crank angle signal θi input is read for one rotation based on the intake bottom dead center, and in step S620. After selecting the maximum value Pmax from the in-cylinder pressure Pi in step S6,
Proceed to 21.

In a succeeding step S621, it is determined whether or not a misfire is currently occurring depending on whether or not the maximum value Pmax of the selected in-cylinder pressure is equal to or less than the threshold value Pfix.

Then, in step S621, Pma
If x> Pfix and it is determined that no misfire is detected, the process proceeds to step S622, the measurement counter n is incremented (n = n + 1), and then step S623.
Proceed to.

In step S623, the measurement counter n
Check whether the counter has reached "10", and the measurement counter n
If it is determined that the number of fires has not reached 10 ", it is determined that the possibility of misfire has not been resolved and step S61.
Return to 9. On the other hand, if the measurement counter n has reached “10” and no misfire is detected 10 times in a row,
Judge that the possibility of misfire has been resolved and exit the routine.

On the other hand, in step S621, Pmax
If ≦ Pfix and it is determined that a misfire is currently occurring, the engine 1 is stopped.

In such an embodiment, the operation set point for realizing the fixed point operation with good fuel economy in the compression ignition combustion region is set based on the engine load demand, and when the generator drive is started or a predetermined time elapses. For each time, the indicated fuel consumption rate at the operation set point and a plurality of surrounding points is calculated, and the operation set point is updated to the point where the indicated fuel consumption rate is the best among the points, so that the specified load near the engine required load is determined. The engine can be operated at the optimum fuel consumption point while maintaining the engine load within the load range.

Therefore, the engine can be suitably used as a power unit of a series hybrid vehicle.

Further, when the throttle opening is WOT, the indicated fuel consumption rate is calculated by obtaining the indicated work amount as a fixed value calculated in advance for the exhaust stroke and the intake stroke (pumping loss work amount). It can be simplified.

Further, when knocking, premature ignition, misfire, etc. occur, recovery control for these is performed to improve the practicality of fixed-point operation control at the operation set point in the compression ignition combustion region. You can In particular, damage to the engine due to knocking or the like can be effectively prevented.

Further, by using premixed compression ignition combustion as the compression ignition combustion, improvement of fuel consumption and reduction of emissions can be effectively realized. In this case, the fuel can be premixed effectively by making the injection hole of the injector face the substantially center of the combustion chamber.

16 and 17 relate to the second embodiment of the present invention, FIG. 16 is a flow chart showing an operation set point setting routine, and FIG. 17 is an explanatory diagram showing indicated fuel consumption rate search points. The present embodiment is mainly different from the above-described first embodiment in that the operation set point is set corresponding to the case where the engine request load is changed from the generator control unit or the like. Descriptions of other points similar to those of the first embodiment will be omitted.

In this embodiment, the operation set point setting routine executed by the ECU 50 will be described with reference to the flowchart of FIG. This routine is executed every time a predetermined time elapses and is executed when an instruction to change the engine required load L0 is input from the generator control unit. First, in step S701, the routine of this time is a fixed point. It is determined whether or not it is the first routine immediately after the start of operation.

If it is determined in step S701 that the current routine is not the first routine immediately after the start of the fixed point operation, the process proceeds to step S702. Step S
In 702, it is checked whether or not this routine is executed by the input of the change command of the engine required load L0, and if not, the step S705.
Jump to.

On the other hand, if it is determined in step S701 that the current routine is the first routine, or if it is determined in step S702 that the current routine is based on the change command input of the engine required load L0. Advances to step S703.

In step S703, based on the engine load demand L0 input from the generator control unit, a preset map or the like is used to set a driving condition for realizing a fuel-efficient fixed point operation by premixed compression self-ignition combustion. Point (T
i = Ti0, N = N0) is set (or reset (see FIG. 17)).

In the following step S704, the engine load L is set through the generator control unit so that the engine speed becomes N = N0 under the condition of the fuel injection pulse width Ti = Ti0.
Perform feedback control to finely adjust.

When the engine speed N converges to N0 in step S704, the process proceeds to step S705, and the fuel injection pulse width Ti = Ti0 is calculated using the illustrated fuel consumption rate calculation subroutine shown in FIG. 4 or 8. Further, the indicated fuel consumption rate ISFC0 under the condition of the engine speed N = N0 is calculated.

Then, in step S705, the indicated fuel consumption rate ISFC0 at the operation set point is calculated, and in step S7
When the processing proceeds to 06, the operation set point update processing is performed by the processing up to step S713.

Specifically, first, as a result of the processing from step S706 to step S711, for example, as shown in FIG. 17, (Ti0, N1) and (Ti0, N1) around the operation set point (Ti0, N0). The indicated fuel consumption rates ISFC1 and ISFC2 are sequentially calculated at two points of (N2). It is assumed that N1 = N0 + ΔN and N2 = N0−ΔN.

That is, in step S706, control for reducing the engine load L by ΔL is performed in advance through the generator control unit. Here, the control of the engine load L is performed in order to improve the convergence of the engine speed N in the process of step S707 described later.

In the following step S707, the engine load L is set through the generator control unit so that the engine speed becomes N = N1 under the condition of the fuel injection pulse width Ti = Ti0.
Perform feedback control to finely adjust.

When the engine speed N converges to N1 in step S707, the flow advances to step S708 to calculate the indicated fuel consumption rate ISFC1 using the indicated fuel consumption rate calculation subroutine shown in FIG. 4 or 8. .

In the following step S709, step S
In order to improve the convergence of the engine speed N at 710, control for increasing the engine load L by ΔL is performed through the generator control unit.

Then, in steps S710 and S711,
The indicated fuel consumption rate ISFC2 is calculated by substantially the same processing as steps S707 and S708 described above.

In step S712, the indicated fuel consumption rate ISFC0 at the operation set point is compared with the indicated fuel consumption rates ISFC1 and ISFC2 in the surroundings in step S712.

If it is determined in step S712 that the indicated fuel consumption rate ISFC0 is not the minimum, the flow proceeds to step S713, and the indicated fuel consumption rate ISFC0.
1. The operation set point is updated to the point where the indicated fuel consumption rate is the minimum in ISFC2, and the process returns to step S706 to perform further update processing for the new operation set point (Ti0, N0).

On the other hand, if it is determined in step S712 that the indicated fuel consumption rate ISFC0 is the minimum, the update processing for the operation set point is terminated and the routine is exited.

According to such an embodiment, in addition to the effects substantially similar to those of the above-described first embodiment, it is possible to increase the range of the required load from the applied engine load device. Play.

In each of the above-mentioned embodiments, the premixing type compression compression ignition system has been described as an example.
The present invention is not limited to this, and for example, a stratified type may be adopted as the compression ignition combustion method.

[0118]

As described above, according to the present invention, it is possible to more effectively realize the improvement in fuel consumption when the fixed point operation is performed by specifying the region in which the compression ignition combustion can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a valve timing and an injection timing for each operation region.

FIG. 3 is a flowchart showing an operation set point setting routine.

FIG. 4 is a flowchart showing a first example of the illustrated fuel consumption rate calculation routine.

FIG. 5 is an explanatory diagram showing the relationship between the stroke volume and the cylinder pressure.

FIG. 6 is an explanatory view showing the relationship between crank angle and stroke volume.

FIG. 7 is an explanatory diagram showing a relationship between a fuel injection pulse width and an injector fuel injection capacity.

FIG. 8 is a flowchart showing a second example of the illustrated fuel consumption rate calculation routine.

FIG. 9 is an explanatory diagram showing the relationship between stroke volume and cylinder pressure when the throttle valve is a wide open throttle (WOT).

FIG. 10 is a flowchart showing a selection routine of an illustrated fuel consumption rate ISFC calculation subroutine shown in FIG.

FIG. 11 is an explanatory diagram showing the indicated fuel consumption rate search points.

FIG. 12 is a flowchart showing a recovery control routine for knocking.

FIG. 13 is a flowchart showing a recovery control routine for premature ignition.

FIG. 14 is a flowchart showing a recovery control routine for misfire.

FIG. 15 is a flowchart showing a recovery control routine for misfire.

FIG. 16 is a flowchart showing an operation set point setting routine according to the second embodiment of the present invention.

FIG. 17 is an explanatory diagram showing the indicated fuel consumption rate search points.

[Explanation of symbols]

1 ... Engine (compression ignition engine) 50 ... Engine control unit (fixed point operation control means,
Operation set point updating means, recovery control means) 51 ... Throttle opening sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 13/02 F02D 13/02 H J K 29/06 29/06 D 41/02 351 41/02 351 41 / 22 380 41/22 380B F term (reference) 3G023 AA02 AA06 AB06 AC05 AG02 AG03 3G084 AA01 BA03 BA13 BA15 BA16 BA20 BA23 CA05 CA07 DA02 EB12 EB22 EC01 EC03 EC04 EC05 FA10 FA13 FA01 FA13 A01 A09 A01 A09 A39 A02 A39 A02 A39 A09 A02 AA17 AB02 AC02 BA03 BA08 BB01 BB06 CA01 DA01 DA02 DA08 DA12 DC09 EA11 EA17 EB04 EC01 FA15 FA16 FA24 FA29 FA40 GA08 HA06Z HB01Z HC01Y HC05X HC06X HC06Y HE01X HE03Z HE04Z 3 04) FA07 3G301 HA01 HA02 HA13 HA16 HA19 JA02 JA21 JA22 JA23 JA31 KA21 KA28 MA11 MA18 ND02 NE23 PA11Z PB03Z PC01B PC01Z PC08Z PC09B PE01A PE 03Z PE04Z

Claims (4)

[Claims] 1. A control device for a compression ignition engine, which compresses an air-fuel mixture to perform self-ignition combustion in at least a part of an operation region, wherein a fixed point of the engine is set at an operation set point set in an operation region in which compression ignition combustion is possible. A fixed point operation control means for operating, an indicated fuel consumption rate at the operation set point and a plurality of points around the operation set point, and an operation for updating the operation set point to a point having the best indicated fuel consumption rate among the points. A control device for a compression ignition engine, comprising: a set point updating means. 2. A driving set point setting means for setting the driving set point when the engine is operated at a fixed point based on a command signal from an engine load control means for controlling an engine load. Item 2. A control device for a compression ignition engine according to Item 1. 3. The operation set point updating means calculates the indicated fuel consumption rate by selecting a predetermined calculation method from a plurality of preset calculation methods based on the operating state of the engine. The control device for the compression ignition engine according to claim 1 or 2. 4. A recovery control means for performing recovery control of the engine in response to at least one of knocking, pre-ignition, and misfire during fixed point operation in the operation region where compression self-ignition combustion is possible. The control device for a compression ignition engine according to any one of claims 1 to 3, wherein