JPH10299562A - Combustion start detector for internal combustion engine and control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly grasp by real time a combustion start period based on a cylinder pressure without depending on ability of a processor, so that fuel injection timing can be more properly controlled, relating to a combustion start detector for an internal combustion engine and a control device for the internal combustion engine. SOLUTION: In a cylinder pressure fetching means 11, cylinder pressure detection information is fetched at each prescribed crank angle in a prescribed crank angle range with the compression top dead center of an internal combustion engine serving as the center. In a subtraction means 12, based on this cylinder pressure detection information, from a cylinder pressure of prescribed crank angle in an expansion stroke, a cylinder pressure in the prescribed crank angle at compression stroke time in a symmetric position with the compression top dead center as a boundary relating to the prescribed crank angle in the expansion stroke is subtracted. In a subtraction result decision means 13, when a subtraction result is decided to exceed a prescribed value, in a combustion start decision means 14, combustion is decided to be started between a crank angle in an expansion stroke when the subtraction result exceeds the prescribed value and a crank angle in the preceding time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion start detecting device for an internal combustion engine and a control device for the internal combustion engine suitable for use in an electronically controlled fuel injection type diesel engine.

[0002]

2. Description of the Related Art When controlling an internal combustion engine, particularly a diesel engine, fuel injection control such as fuel injection amount and fuel injection timing is extremely important, and such control greatly affects drivability and exhaust gas. Particularly in vehicle engines, there is a high demand for drivability and exhaust gas.

[0003] For example, the amount of NOx in the exhaust gas is related to the combustion start timing and the combustion speed. In order to reduce NOx in the exhaust gas, it is particularly effective to control the combustion start timing. This combustion start time is determined by the fuel injection start time or EG.
It can be controlled by adjusting R (exhaust gas recirculation device). Therefore, it is conceivable to reduce the NOx in the exhaust gas by controlling the fuel injection start timing and the EGR by feedback control based on the grasped combustion start timing while grasping the actual combustion start timing. .

Therefore, it is necessary to grasp the combustion start timing. However, it is necessary to determine the heat generation in the cylinder using an in-cylinder pressure sensor and determine the start of combustion from the heat release rate. It has been widely practiced. In addition, the fuel injection timing of a distributed injection pump of a diesel engine is controlled by operating a timer piston. In this case, the fuel injection timing generally includes a piston stroke, a rise in pump injection pressure, a needle lift timing, and the like. And the fuel injection timing control can be more appropriately controlled based on the combustion start timing.

[0005]

As described above, in the combustion pressure analysis method for determining the start of combustion by obtaining the heat generation rate in the cylinder from the cylinder pressure detected by the cylinder pressure sensor, as described above, generally, The analysis that measures only the in-cylinder pressure during engine operation and determines the heat generation and heat generation rate in the cylinder to determine the start of combustion is performed afterwards, and the combustion is performed in real time during engine operation. It does not determine the start.

The reason why the analysis is not performed in real time is that it takes time to analyze the start of combustion. That is, in the above-described combustion pressure analysis method, the in-cylinder pressure is detected about every 1 ° CA (crank angle 1 °), and the heat generation and the heat generation rate are obtained by analog arithmetic processing based on each in-cylinder pressure data. Determines the start of combustion. In such an analysis process, it is difficult to judge the start of combustion in real time (at least within one combustion cycle) unless arithmetic processing can be performed at an extremely high speed.

In general, an arithmetic processing unit used for engine control has a limitation in processing speed, and it is difficult to perform such high-speed processing. It is extremely difficult to apply the technique of determining heat generation in the cylinder based on the cylinder pressure while detecting the internal pressure to determine the start of combustion from the heat release rate) for controlling the fuel injection start timing and EGR. is the current situation.

Therefore, it is difficult at present to control the fuel injection timing in the distributed injection pump of the diesel engine based on the combustion start timing. As for the fuel injection timing control, it is necessary to consider the time difference between the drive timing of the distribution type injection pump and the timing at which the fuel is actually spilled, and the time difference between the fuel injection timing and the combustion start timing. It is difficult to perform appropriate fuel injection timing control based on the combustion start timing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems. It is an object to provide a combustion start detection device. It is another object of the present invention to provide a control device for an internal combustion engine, in which a fuel injection timing can be more appropriately controlled by a timer piston while properly grasping a combustion start timing in real time.

[0010]

According to a first aspect of the present invention, there is provided a combustion start detecting apparatus for an internal combustion engine according to the present invention, wherein an in-cylinder pressure intake means, a subtraction means, a subtraction result determination means, and a combustion start determination means are provided. It is composed with and. The in-cylinder pressure intake means captures and stores the in-cylinder pressure detection information in the combustion chamber at every predetermined crank angle within a predetermined crank angle range centered on the compression top dead center of the internal combustion engine, and the subtraction means uses the in-cylinder pressure Based on the in-cylinder pressure detection information taken in by the take-in means, based on the in-cylinder pressure at a predetermined crank angle in the expansion stroke, the compression stroke at a position symmetrical with respect to the compression top dead center relative to the predetermined crank angle in the expansion stroke The in-cylinder pressure at a predetermined crank angle at the time is configured to be subtracted. And the subtraction result determination means,
It is determined whether or not the result of the subtraction by the subtraction means has exceeded a predetermined value. If the result of the subtraction determination by the combustion result determination means determines that the result of the subtraction has exceeded the predetermined value, the result of the subtraction is determined. It is configured to determine that combustion has started between the crank angle in the expansion stroke and the previous crank angle when the predetermined value is exceeded.

According to a second aspect of the present invention, there is provided a combustion start detecting apparatus for an internal combustion engine, comprising: an in-cylinder pressure intake means; a correlation value calculation means;
It comprises a correlation value determining means and a combustion start determining means. The in-cylinder pressure intake means captures and stores in-cylinder pressure detection information in the combustion chamber for each predetermined crank angle within a predetermined crank angle range centered on the compression top dead center of the internal combustion engine. The heat generation rate correlation value is calculated from a plurality of adjacent in-cylinder pressures based on in-cylinder pressure detection information taken into the in-cylinder pressure taking means. The correlation value determining means determines whether the heat generation rate correlation value calculated by the correlation value calculating means has exceeded a predetermined value, and the combustion start determining means determines the heat generation rate by the correlation value determining means. If it is determined that the rate correlation value has exceeded the predetermined value, it is determined that combustion has started between the crank angle in the expansion stroke and the previous crank angle when the heat release rate correlation value has exceeded the predetermined value. It is configured to determine.

According to a third aspect of the present invention, there is provided a control apparatus for an internal combustion engine including a plunger pump, a timer piston, a combustion start timing detecting means, a target fuel injection timing setting means, and a control means. . The plunger pump is provided in the fuel injection pump of the diesel internal combustion engine and pressurizes the fuel to a high pressure.The timer piston adjusts the fuel injection timing from the fuel injection valve by adjusting the fuel pressurization timing by the plunger pump. Control, the combustion start timing detection means detects the combustion start timing of the diesel internal combustion engine, and the target fuel injection timing setting means considers the fuel transfer delay and the like with respect to the detection result of the combustion start timing detection means. The target fuel injection timing is set by performing the corrected
The position of the timer piston is controlled in accordance with the target fuel injection timing set by the target fuel injection timing setting means.

According to a fourth aspect of the present invention, there is provided a control apparatus for an internal combustion engine according to the third aspect, further comprising:
Further provided with a rotation speed detecting means,
The high-pressure fuel is delivered to the fuel injection valve, the rotation speed detecting means is configured to detect the rotation speed of the diesel internal combustion engine, and the target fuel injection timing setting means is connected to the high-pressure fuel pipe. The correction is performed in accordance with the length and the rotation speed detected by the rotation speed detection means.

According to a fifth aspect of the present invention, there is provided a control apparatus for an internal combustion engine according to the third or fourth aspect, wherein the target fuel injection timing setting means sets the target fuel injection timing from the start of fuel injection from the fuel injection valve. The correction is performed in accordance with the period up to the start of combustion by.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a first embodiment of the present invention; FIG.
FIG. 10 and FIG. 11 show a control device for an internal combustion engine according to a second embodiment of the present invention, showing a combustion start detection device and a control device for the internal combustion engine according to the embodiment.

First, a combustion start detection device and a control device for an internal combustion engine according to a first embodiment will be described with reference to FIG. This internal combustion engine is a diesel internal combustion engine (diesel engine). As shown in FIG. 1, a plunger pump 5 for pressurizing fuel to a high pressure is provided in a fuel injection pump 50.
1 and an injection timing control mechanism 52 that controls the fuel injection timing from a fuel injection valve (needle valve) 60 by adjusting the fuel pressurization timing by the plunger pump 51.

The injection timing control mechanism 52 adjusts the position (phase angle) of the roller 53 that comes into contact with a face cam (not shown) by adjusting the position of the timer piston 54.
The injection timing control is performed.
Is adjusted by controlling the hydraulic pressure in the timer piston chamber 55 with an electromagnetic timer control valve (TCV) 56.

In order to control the position of the timer piston 54, a timer position controller (control means)
40 are provided. The timer position controller 40 determines that the combustion start timing is a target value (target combustion start timing).
The fuel injection timing is controlled by adjusting the position of the timer piston 54 based on the target combustion start timing information and the actual combustion start timing information.

For this reason, target combustion start timing setting means 30 for setting the target combustion start timing, combustion start detection means (combustion start detection device for an internal combustion engine according to the present invention) 10 for detecting the actual combustion start timing, and target fuel An injection timing setting means 20 is provided. Target combustion start timing setting means 30
Sets the target combustion start timing _TCO as shown in the following equation according to the operating state of the engine, that is, the engine speed Ne and the fuel injection amount Q.

T _CO = f ₁ (Ne, Q) (1) The fuel injection amount Q itself is set based on the engine speed Ne, the engine load (for example, the accelerator pedal depression amount), the coolant temperature, and the like. Is done. Therefore, the target combustion start timing T _CO is set based on information from the engine speed sensor 81, the engine load sensor (accelerator position sensor) 82, and the like.

The combustion start detecting means 10 is one of the major features of this embodiment, and detects the start of combustion based on the in-cylinder pressure information. First, the principle will be described. FIG. 2 shows the change in the in-cylinder pressure near the compression top dead center (crank angle is 0 ° CA) and the heat generation rate in association with each other. In the compression stroke (crank angle is 0 ° CA or less), the in-cylinder pressure increases in accordance with the increase of the crank angle regardless of the presence or absence of combustion. The internal pressure drops. Here, if there is no combustion, the in-cylinder pressure characteristics are symmetrical with respect to the compression top dead center, as indicated by a chain line PL1 in FIG.

That is, α ° CA before the compression top dead center (this is αα CA
° BTDC) and the pressure after compression top dead center
In-cylinder pressure PAα at ° CA (this is referred to as α ° ATDC)
Are equal to each other. For example, a 30 ° BTDC in-cylinder pressure PB ₃₀ and a 30 ° ATDC in-cylinder pressure PA ₃₀ , 20 ° BT
DC in-cylinder pressure PB ₂₀ and 20 ° ATDC in-cylinder pressure PA ₂₀ ,
The in-cylinder pressure PB ₁₀ of 10 ° BTDC and the in-cylinder pressure PA ₁₀ of 10 ° ATDC are equal to each other.

Therefore, if there is no combustion, the following equation holds. PBα = PAα However, when combustion occurs, heat of combustion is generated (see FIG. 2 (B)), and the combustion energy increases the in-cylinder pressure.
Although such symmetry is lost, it is generally considered that combustion starts after compression top dead center (of course, within a period close to compression top dead center to some extent).
If there is combustion before (α ° ATDC) (α ° ATDC is a point close to the compression top dead center to some extent), the following equation holds.

PBα <PAα Therefore, the main combustion start detecting means (combustion start detecting device) 10
In the vicinity of the compression top dead center (for example, -35 ° CA to 35 °
In the period of CA, a predetermined crank angle (for example, 5 °)
(In each CA), the in-cylinder pressure is taken (detected), and the in-cylinder pressure PB at a crank angle that is symmetrical about the compression top dead center
alpha, and calculates the difference between PAα ΔPα (= PAα-PBα) , this difference DerutaPiarufa is, reaches the reference value (target pressure difference) [Delta] P ₀ set in advance, it is determined that combustion has already started, the determination The detected value information of the combustion start timing is output based on the time.

Note that the target pressure difference ΔP _{0 in} this case can be set corresponding to an appropriate time point of the initial combustion. In this case, the target pressure difference ΔP ₀ is one of the total combustion heat (the total heat amount generated in one combustion).
The target pressure difference ΔP ₀ is set corresponding to the time when 0% occurs. In order to perform such combustion start detection, the main combustion start detection means (combustion start detection device) 10 includes an in-cylinder pressure intake means 11, a subtraction means 12, a subtraction result determination means 13, a combustion A start determination unit 14 is provided.

The in-cylinder pressure intake means 11 includes an in-cylinder pressure sensor 83
Based on each detection information from the crank angle sensor 84, the in-cylinder pressure in the combustion chamber of the engine is captured and stored within a predetermined crank angle range around the compression top dead center of the crank angle. Here, 35 ° CA before compression top dead center
The in-cylinder pressure detection information is fetched from (35 ° BTDC) to 35 ° CA (35 ° ATDC) after the compression top dead center every θs (for example, 5 ° CA), and sequentially addresses i (i = 1, 2, 3,...).

That is, address 1 is the cylinder pressure PB _{35 at} 35 ° BTDC, address 2 is the cylinder pressure PB _{30 at} 30 ° BTDC, address 3 is the cylinder pressure PB _{25 at} 25 ° BTDC, and address 4 is 20 °. cylinder pressure PB ₂₀ in BTDC, the address-cylinder pressure PB ₁₅ in 15 ° BTDC to 5, the cylinder pressure PB ₁₀ in 10 ° BTDC to address 6, the in-cylinder pressure PB ₅ is in 5 ° BTDC to address 7, the address 8 The in-cylinder pressure PB _{0 at} TDC (compression top dead center) is stored.

Address 9 is the cylinder pressure PA _{5 at} 5 ° ATDC, address 10 is the cylinder pressure PA _{10 at} 10 ° ATDC, address 11 is the cylinder pressure PA _{15 at} 15 ° ATDC, and address 12 is 20 °. ATDC
Cylinder pressure PA ₂₀ , address 13 has 25 ° ATD
In-cylinder pressure PA _{25 at} C, 30 ° AT at address 14
In-cylinder pressure PA _{30 at} DC, 35 ° A at address 15
The in-cylinder pressure PA _{35 at} TDC is stored.

Based on the in-cylinder pressure information taken in by the in-cylinder pressure intake means 11, the subtraction means 12 calculates the compression top dead center for the predetermined crank angle of the expansion stroke from the cylinder pressure at the predetermined crank angle of the expansion stroke. Is subtracted from the in-cylinder pressure at a predetermined crank angle at the time of the compression stroke which is located symmetrically with respect to. That is, from the in-cylinder pressure PAα at a certain point in time α ° CA (α ° ATDC) of the expansion stroke (that is, after the compression top dead center), the compression stroke (ie , Before compression top dead center) −α ° CA (α ° BTD
The in-cylinder pressure PBα in C) is subtracted.

Here, α ° = 5 °, 10 °, 15 °,
Since they are 20 °, 25 °, 30 °, and 35 °, the subtraction means 12 specifically performs subtraction as follows. When α ° = 5 °, 5 stored in address 9
The in-cylinder pressure PB ₅ at 5 ° BTDC stored at the address 7 is subtracted from the in-cylinder pressure PA ₅ at ATDC.

When α ° = 10 °, the data stored in the address 10 is stored.
In-cylinder pressure PA at 10 ° ATDC _TenTo address 6
In-cylinder pressure PB at 10 ° BTDC stored_TenSubtract
You. When α ° = 15 °, 15 ° stored in the address 11
° In-cylinder pressure PA at ATDC _FifteenIs stored at address 5
Cylinder pressure PB at 15 ° BTDC_FifteenIs subtracted. α ° =
At 20 °, the 20 ° ATDC stored at address 12
Cylinder pressure PA ₂₀To 20 ° B stored at address 4
In-cylinder pressure PB at TDC₂₀Is subtracted.

When α ° = 25 °, the data stored in the address 13 is stored.
In-cylinder pressure PA at 25 ° ATDC _{twenty five}To address 3
In-cylinder pressure PB at 25 ° BTDC stored_{twenty five}Subtract
You. When α ° = 30 °, 30 ° stored in the address 14
° In-cylinder pressure PA at ATDC ₃₀From address 2
In-cylinder pressure PB at 30 ° BTDC₃₀Is subtracted. α ° =
At 35 °, the 35 ° ATDC stored at address 15
Cylinder pressure PA ₃₅35 ° B stored at address 1 from
In-cylinder pressure PB at TDC₃₅Is subtracted.

In the subtraction result judging means 13, the subtracting means 12
The subtraction result by, compared with a predetermined value (target pressure difference [Delta] P _0), the subtraction result is determined whether exceeds a predetermined value (target pressure difference [Delta] P _0). When the subtraction result determination means 13 determines that the subtraction result exceeds a predetermined value, the combustion start determination means 14 determines the crank angle in the expansion stroke when the subtraction result exceeds the predetermined value (this is referred to as θ _i). °
Determines a CA) and the combustion is started with the last ([theta] s ° CA before the crank angle) [(θ _i -θs) ° CA], estimates the combustion start timing by using the interpolation method.

That is, the crank angle θ in the expansion stroke
_{When the} subtraction result exceeds the predetermined value ΔP ₀ for the first time at _i ° CA, the pressure difference ΔP _i detected at the time of the crank angle θ _i ° CA (a certain point in the expansion stroke corresponding to the address i) and the pressure difference ΔP _i immediately before ( The pressure difference ΔP _(i-1) detected at a crank angle θ _(i-1) ° CA corresponding to the address i-1 before 5 ° CA ₎ and a predetermined value (target pressure difference) ΔP ₀ , The combustion start timing θ using an interpolation method as shown in the following equation.
Estimate _c .

Θ _c = θ _(i-1) + θs × (ΔP ₀ −ΔP _(i-1) ) / (ΔP _i −ΔP _(i-1) ) (2) Target fuel injection timing setting means 20 Is the PI controller 2
1 and a correction function section (correction means) 22.
In the PI controller 21, the difference from the target combustion start timing theta _a set by the target combustion start timing setting section 30, by subtracting the actual combustion start time theta _c detected by the combustion start detecting means (combustion start detector) 10 (Θ _a −θ _c ) or the target pump injection timing θ corresponding to the difference (θ _a −θ _c )
The difference Δθ between the _PO and pump injection timing θ _P (= θ _PO -
PI control processing is performed based on θ _P ).

In the correction means 22, the target combustion start timing θ _a
Is corrected in response to a fuel transfer delay or the like, and the target combustion start timing _θa is converted into _a target fuel injection timing _θaj and output. Here, the contents of the correction by the correction unit 22 will be described. The control of the fuel injection timing is performed by moving the timer piston 54. What is adjusted by the timer piston 54 is the timing of pressurizing the fuel by the plunger pump 51 of the fuel injection pump 50 to a high pressure. However,
It is the fuel injection valve (needle valve or injection nozzle) 60 that is separated from the fuel injection pump 50 that actually injects fuel into the cylinder. The fuel pressurization timing by the plunger pump 51 of the fuel injection pump 50 and the injection nozzle 6
There is a transfer delay between the zero fuel injection timing and the fuel injection timing.

That is, as shown in FIG. 3, a fuel supply pipe 58 is interposed between the fuel injection pump 50 and the fuel injection valve (needle valve) 60, and the plunger pump 51 of the fuel injection pump 50 When the pressurization is performed, the fuel injection by the fuel injection valve 60 is performed after the pressure transmission time in the fuel supply pipe 58. As shown in the following equation, this pressure transmission time takes a time dependent on the pipe length (pipe length) between the fuel injection pump 50 and the fuel pressurization timing.

Pressure transmission time = pipe length / sound speed Therefore, if the engine layout is determined, the pressure transmission time is also determined to be a fixed time. Therefore, the crank angle required for this pressure transmission is proportional to the engine speed Ne (rpm). For example, if the pipe length is about 0.83 m, the sound speed in the fuel supply pipe is 1355 m / s. The crank angle required for transmission is as follows.

Crank angle required for pressure transmission = [(Ne / 60) × 360] × (0.83 / 1355) ≒ 0.0037 × Ne Therefore, in calculation, for example, if the engine speed Ne is 1000 rpm, 3 0.7 (° CA).

On the other hand, according to the experimental results under the same conditions, when the engine speed Ne is 1000 rpm, about 4 ° CA
It was found that the transfer delay was of the order, and the transfer delay occurred almost as theoretically. Although a delay occurs between the start of the lift of the injection nozzle 60 and the rise of the combustion pressure (that is, the start of combustion), the fuel mass passing through the nozzle is almost proportional to the injection pressure, and the injection pressure is Since the delay is proportional to the engine speed Ne, this delay has little dependence on the engine speed Ne, but can be expressed as a function of the combustion start timing θ _C and the engine speed Ne as follows.

Delay of rise of combustion pressure = f ₂ (θ _C , Ne) For example, a straight line LL1 shown in FIG. 4 shows an injection start timing characteristic, and a straight line LL2 shows a combustion start timing characteristic.
As shown in the figure, from the start of fuel injection to the start of combustion, it can be seen that there is a delay period (for example, 8 ° CA) corresponding to a substantially constant crank angle regardless of the engine speed.

The correction means 22 takes into account such a transfer delay between the fuel injection pump 50 and the injection nozzle 60 and a delay in the rise of the combustion pressure, and considers the actual pump injection timing θ _P and the target pump injection timing. θ _PO can be calculated by the following equation. θ _P = θ _C −θd + Ka · Ne + f ₂ (θ _C , Ne) (3) θ _PO = θ _CO −θd + Ka · Ne + f ₂ (θ _CO , Ne) (4) where θd is the maximum delay Is a position, and Ka is a constant determined by the pipe length. For example, Ka = 0.0037, and f ₂
Is a combustion start delay function.

The timer position controller (control means) 40 calculates a timer stroke adjustment amount ΔST, calculates a timer control valve drive current duty T _CVON in accordance with the adjustment amount ΔST, and adjusts the stroke of the timer piston. The above target pump injection timing θ
The difference Δθ between the _PO and pump injection timing θ _P (= θ _PO -
θ _P ) corresponds to the timer stroke adjustment amount (difference between the target timer stroke and the actual timer stroke) ΔST of the timer piston.
ST can be expressed by the following equation.

ΔST = θ _PO −θ _P = Δθ _P (5) Then, the timer control valve drive current duty T _CVON can be calculated by the following equation. _{T CVON = k PTCV · ΔST (} i) + k iTCV ΣΔST (i) + T CV (θ PO, Ne) Note ··· (6), k _PTCV is feedback gain, the first and second term of the above equation PI A feedback term and a third term relating to control and correction are basic duty terms, which are determined by learning control in accordance with the target pump injection timing θ _PO and the engine speed Ne.

In addition, if the correction means 22 is supplemented,
The detection of the combustion start timing may not be directly detected by the rise of the combustion pressure, but may be detected based on a parameter corresponding to the combustion start timing or the state of the operating member. Since the control device and the combustion start detection device of the internal combustion engine as the first embodiment of the present invention are configured as described above, for example, the fuel injection timings θ _P and θ _PO are set as shown in FIG. Based on this, the timer control valve drive current duty T _CVON is set as shown in FIG. 6, and the fuel injection timing (combustion timing) is controlled to an optimal state.

That is, as shown in FIG.
Start time θ_CIs detected (step A10). This detection
Is combustion start detection means (combustion start detection device for internal combustion engine)
10, which will be described later. Next
The target combustion start timing θ_COSet (set) (Step
A20). This setting is performed by the target combustion start timing setting means 3
0, but the target combustion start timing θ _COIs the previous expression
As shown in (1), the engine speed Ne and the fuel injection amount Q
It is set according to. Note that the fuel injection amount Q
The engine speed Ne and the engine load (for example, accelerator pedal depression)
Volume) and cooling water temperature.

Next, the actual fuel injection timing θ _P at the pump side
Then, the target fuel injection timing θ _PO on the pump side is calculated (step A30). The fuel injection timings θ _P and θ _PO are determined by the target fuel injection timing setting means 20 according to the equations (3) and (4).
Is calculated from the actual combustion start timing θ _C detected or set in each of the above steps, the target combustion start timing θ _CO, and the engine speed Ne detected by the engine speed sensor 81.

The timer position controller (control means) 40 sets the actual fuel injection timing θ thus set.
_{Based on P} and the target fuel injection timing θ _PO , as shown in FIG. 6, a calculation is performed by a timer interruption for a predetermined time (for example, 10 msec). First, a timer stroke adjustment amount ΔST is calculated (step B10). . That is, using the previous equation (5), the timer stroke adjustment amount (the difference between the target timer stroke and the actual timer stroke) is defined as the difference Δθ (= θ _PO −θ _P ) between the target pump injection timing θ _PO and the pump injection timing θ _P. Difference) ΔST is calculated.

Next, the drive current duty T _CVON of the timer control valve 56 is calculated using the above equation (6) (step B10). Thereby, the drive current duty of the timer control valve 56 (that is, the control amount)
T _CVON is the actual combustion start timing θ _C and the target combustion start timing θ _CO
Is set based on the feedback control while taking into account the delay in fuel transfer and the delay from fuel injection to combustion.

Therefore, the diesel engine distribution type
The fuel injection timing control of the injection pump
When the pump is driven and when the fuel spill is actually performed
Time difference between the fuel injection timing and the combustion start timing
Independent of time difference, based on combustion start time
It can be done properly. By the way, actual combustion
Start time θ_CExplain the detection of
Period θ _CIn the detection of the noise, as shown in FIGS.
While performing each process of the rank angle interrupt routine, FIG.
Detection is performed as shown.

That is, as shown in FIG. 7, a predetermined crank angle cycle (sample interval)
The process is performed with θs (here, θs = 5 ° CA). First, the crank angle is set within a predetermined range (here, 35 ° before compression top dead center to 35 ° after compression top dead center (that is, compression top dead center). It is determined whether or not it is within the range of −35 ° to + 35 ° with respect to the dead center (step C10).

If the crank angle is not within this range, the process is not performed. If the crank angle is within this range, the detected in-cylinder pressure value is fetched from the in-cylinder pressure sensor 83 (step C20). Is stored in the memory (i) (step C30). Note that i is a memory address, and as shown in FIG.
° (ie, when the crank angle reaches -35 °)
Interrupt routine (35 ° B interrupt routine)
= 1 (step D10).

[0053] Therefore, when the crank angle reaches -35 °, the memory address i = 1, cylinder pressure detection value P ₁ at this time is detected is stored. And a memory address i
Is increased to i = i + 1 (step C40). next,
When the crank angle rotates by θs (= 5 ° CA), the processing of steps C10 to C40 is repeated again.

[0054] That is, when the crank angle reaches -30 °, cylinder pressure detection value P ₂ detected when the memory address i = 2 is stored, when the crank angle reaches -25 °, a memory address i = 3 cylinder pressure detection value P _3, which is detected at this time is stored, when the crank angle reaches -20 °, so that cylinder pressure detection value P ₄ detected at this time in the memory address i = 4 is stored Then, the cylinder pressure detection value is stored until the crank angle reaches 35 °.

As a result, in-cylinder pressure data for each crank angle θs (= 5 °) from memory address i = 1 (crank angle is −35 °) to memory address i = 15 (crank angle is 35 °) Stored in memory. Thus, when the cylinder pressure data is stored in the memory, as shown in FIG. 9, to detect the actual combustion start timing theta _C.

First, the in-cylinder pressure taking-in means 1
1. Based on the in-cylinder pressure information taken in by step 1, based on the in-cylinder pressure at a predetermined crank angle in the expansion stroke, the predetermined crank during the compression stroke at a position symmetrical with respect to the compression top dead center with respect to the predetermined crank angle in the expansion stroke The in-cylinder pressure at the angle is subtracted (step E10). That is, the expansion stroke (i.e., the compression top after dead center) from the cylinder pressure P _i at point in (a time of memory i), certain compression top dead center and the point symmetrical position on the border, the compression stroke ( that is, subtracting the in-cylinder pressure P _j at the time before the compression top dead center) (the time the memory j).

Therefore, for example, a cylinder 5 ° after the compression top dead center
Injection pressure [Detection of in-cylinder pressure stored in memory (i = 9)
Value] P₉Injection pressure at 5 ° before compression top dead center [memory
(In-cylinder pressure detection value stored in (i = 7)) P₇Is subtracted (P
₉−P₇). Furthermore, in-cylinder injection at 10 ° after compression top dead center
Injection pressure [in-cylinder pressure detection value stored in memory (i = 10)]
P _TenFrom the cylinder injection pressure [memory (i
= In-cylinder pressure detection value stored in 6)] P₆Is subtracted (P_Ten−
P₆).

Thus, the subtraction value (P ₉ -P ₇ ),
_{(P 10 -P 6), (} P 11 -P 5), (P 12 -P 4),
_{(P 13 -P 3), (} P 14 -P 2), is calculated respectively (P ₁₅ -P ₁₎ (step E20). Then, the subtraction result determining means 13 compares the subtraction result by the subtracting means 12 with a predetermined value (target pressure difference ΔP ₀ ) to determine whether the subtraction result exceeds a predetermined value (target pressure difference ΔP ₀ ). To determine the sampling point at which the crank angle θ _ic
Ask for.

For example, the subtraction values (P ₉ −P ₇ ), (P ₁₀ −
P ₆ ) does not exceed the target pressure difference ΔP ₀ , but the subtracted value (P ₁₁
-P ₅₎ If exceeds the target pressure difference [Delta] P _0, sample points subtraction result exceeds the target pressure difference [Delta] P ₀ is i = 11, the crank angle theta ₁₁ at this point, the 15 ° CA.
Then, in the combustion start determining means 14, the crank angle in the expansion stroke when the subtraction result exceeds a predetermined value (this is assumed to be θ _ic ° CA) and the crank angle [(θ _ic − 5) [CA]], the combustion start time is estimated using an interpolation method.

[0060] The simplest using linear interpolation, and the pressure difference [Delta] P _ics that are detected at the crank angle θ _ic ° CA (point in the expansion stroke corresponding to the address ics), the immediately preceding (5 ° CA The pressure difference ΔP detected at the crank angle θ _(ic-1) ° CA corresponding to the address ic-1 before _{)
From (ic-1)} and the predetermined value (target pressure difference) ΔP ₀ , the combustion start timing θ _c is calculated (estimated) using the above equation (2).

In this way, a small amount of sampling data [here, one combustion cycle (crank angle 720 °)
With 15 data], the combustion start timing θ _c can be easily and reliably estimated, and the engine can be operated without imposing a load on the arithmetic processing system and without using a processing device having a particularly excellent arithmetic processing capability. There is an advantage that the start of combustion can be determined in real time while driving.

Since the start of combustion can be easily determined in this manner, various controls of the engine such as the control of the fuel injection timing (particularly the fuel injection start timing) as in the present embodiment and the control of the EGR are performed. The start timing can be appropriately determined based on this while appropriately grasping the start timing in real time. Next, a combustion start detection device for an internal combustion engine according to a second embodiment of the present invention will be described.

This combustion start detection device detects the start of combustion based on the in-cylinder pressure, as in the first embodiment. However, in this embodiment, the point at which the heat generation rate increases with the start of combustion is described. Focusing on this heat release rate, the start of combustion is determined. That is, based on the in-cylinder pressure, the heat generation rate (heat generation amount per unit crank angle) dQ /
dθ is calculated, and the heat release rate dQ / dθ is set to a predetermined value dQ.
If it exceeds ₀ , it is determined that combustion has started.

For this reason, the present combustion start detecting apparatus is provided with the configuration shown in FIG.
As shown in the figure, in-cylinder pressure intake means 11, correlation value calculation means 1
5, a correlation value determining means 16 and a combustion start determining means 17 are provided. The in-cylinder pressure intake means 11 includes an in-cylinder pressure sensor 83 and a crank angle sensor 84, as in the first embodiment.
The cylinder pressure in the combustion chamber of the engine is fetched for each predetermined crank angle within a predetermined crank angle range centered on the compression top dead center of the crank angle based on each detection information from the CPU and stored in a memory (not shown).

The correlation value calculating means 15 calculates a heat generation rate correlation value from a plurality of adjacent in-cylinder pressures based on the in-cylinder pressure detection information taken into the in-cylinder pressure taking means 11. dθ can be expressed as the following equation. dQ / dθ = [1 / (k−1)] · [V (dP / dθ) + kP (dV / dθ)] (7) where k = C _P / C _V , C _P : constant pressure specific heat, C _V : Constant volume specific heat V: In-cylinder volume (corresponding to piston position), P: In-cylinder pressure When the equation (7) is approximated with respect to the differential value of P at the time point i, dP / dθ | _i = (P _i −P _{i −1} ) / Δθ dQ / dθ | _i = [A / (k−1)] · [V _i (P _i −P _i−1 ) / Δθ) + kP _i (dV / dθ | _i )] = [A / (k-1)] - _{[V i / Δθ + k (dV} / dθ | i) ] P _i - [A / (k-1)] _{· V i P i-1 /} Δθ = α i P i -β i P _i-1 ... (8) α _i , β _i : weighting factors, and the heat release rate dQ in a certain sampling period i
/ D [theta] | _i may be calculated from the cylinder pressure P _i-1 in-cylinder pressure P _i and the preceding sampling period i-1 in this sampling period i. Hereinafter, dQ /
In the description, dθ is omitted from dθ.

The correlation value calculating means 15 calculates the approximate heat release rate from the in-cylinder pressure P _i (i = 1 to n) taken in each sampling cycle based on the above equation (8). (Heat generation rate correlation value) dQ _i is calculated. The weighting factors α _i and β _i are stored in advance as, for example, table values. In the correlation value determining means 16, the correlation value calculating means 1
5 the heat release rate correlation value dQ _i calculated in determines whether exceeds a predetermined value dQ _0.

Then, in the combustion start judging means 17, the correlation value judging means 16 determines that the heat release rate correlation value dQ _i is a predetermined value d.
If it is determined that Q ₀ has been exceeded, the crank angle (this is θ _ic ° CA) in the expansion stroke when this heat release rate correlation value exceeds a predetermined value (the sampling period at this time is ic). ) and determined that combustion has started between the previous (crank angle [theta] s ° CA before) [(θ _ic -θs) ° CA].

That is, the crank angle θ in the expansion stroke
_{I c}Heat release rate correlation value dQ at ° CA_{I c}Is prescribed for the first time
Value dQ₀Over this crank angle θ_{I c}° CA
Calculated at the point (at some point in the expansion stroke corresponding to address ic)
The issued heat release rate correlation value dQ _{I c}And immediately before (θs ° C
A, crank angle θ corresponding to address ic-1_(i
c-1)° CA), the heat release rate correlation value dQ calculated at
_ic-1And a predetermined value dQ₀From the following formula, the interpolation method
Combustion start time θ using_cIs estimated.

Θ _c = θ _(ic-1) + θs × (dQ ₀ −dQ _ic-1 ) / (dQ _ic −dQ _ic-1 ) (9) The internal combustion engine according to the second embodiment of the present invention Since the combustion start detection device is configured as described above, detection of the combustion start timing θ _C is performed as follows. First, in detecting the actual combustion start timing θ _C , as in the case of the above-described first embodiment, while performing each processing of the crank angle interrupt routine as shown in FIGS. 7 and 8, as shown in FIG. To perform detection.

That is, in the in-cylinder pressure intake means 11, as shown in FIG. 7, the crank angle is set within a predetermined range (35 ° before compression top dead center to 35 ° after compression top dead center (that is, compression top dead center). It is determined whether or not the angle is within a range of −35 ° to + 35 ° with respect to the point (step C10). If the crank angle is within this range, the in-cylinder pressure detection value is taken from the in-cylinder pressure sensor 83 ( Step C20), and stores the detected in-cylinder pressure value in the memory (i) (Step C30).

The memory address i is, as shown in FIG.
An interrupt routine (35) when the crank angle is 35 ° before the compression top dead center (that is, when the crank angle reaches −35 °)
I = 1 has been reset by the ° B interrupt routine) (step D10). Therefore, when the crank angle is -3.
When 5 ° is reached, the memory address i = 1, cylinder pressure detection value P ₁ at this time is detected is stored. Then, the memory address i is increased to i = i + 1 (step C4).
0) One after another, the process of steps C10 to C40 is repeated for each predetermined crank angle θs (= 5 ° CA), and the detected in-cylinder pressure value Pi corresponding to each memory address _i is stored.

As described above, each in-cylinder pressure data is stored in the memory.
Once delivered, as shown in FIG. 11, the actual combustion start timing
θ_CIs detected. First, the correlation value calculating means 15
Based on the in-cylinder pressure detection information captured by the internal pressure intake means 11,
From the plurality of adjacent in-cylinder pressures according to equation (8).
Detection cylinder pressure P _iHeat release rate dQ depending on_iIs calculated.
Step F10).

DQ _i = α _i P _i −β _i P _i-1 (8) Next, the correlation value determination means 16 determines the heat release rate correlation value dQ _i calculated by the correlation value calculation means 15 as a predetermined value. It is determined whether or not the value dQ ₀ has been exceeded (step F20). Then, the combustion start determination unit 17, when the ic-th heat release rate correlation value dQ _ic is determined that exceeds the predetermined value dQ ₀ by the correlation value determining section 16, the heat generation rate correlation value exceeds a predetermined value (Θ _ic ° CA) and the crank angle of the previous time (θs ° CA) [(θ _ic −θs) °
CA] and the crank angle θ
the heat release rate correlation value dQ _ic calculated at the time of _ic ° CA,
From the heat release rate correlation value dQ _ic-1 calculated immediately before (before θs ° CA) and the predetermined value dQ ₀ , the combustion start timing θ _c is calculated by the equation (9) using an interpolation method.

In this manner, a small amount of sampling data [here, one combustion cycle (crank angle 720 °)
With 15 data], the combustion start timing θ _c can be easily and reliably estimated, and the engine can be operated without imposing a load on the arithmetic processing system and without using a processing device having a particularly excellent arithmetic processing capability. There is an advantage that the start of combustion can be determined in real time while driving.

As described above, since the start of combustion can be easily determined, various controls of the engine such as the control of the fuel injection timing (particularly the fuel injection start timing) as in the present embodiment and the control of the EGR are performed. The start timing can be appropriately determined based on this while appropriately grasping the start timing in real time. In each of the embodiments, primary interpolation is used as the simplest example, but the interpolation method is not limited to this.

The range of the crank angle for sampling the in-cylinder pressure is an example in each embodiment.
This range may be at least near the start of combustion (generally near the compression top dead center), and may be narrower depending on the engine (for example, a range from -15 ° CA to + 15 ° CA or a range narrower than this). It is also possible to limit.

Further, in the combustion start detecting device according to the first embodiment, the in-cylinder pressure at a crank angle symmetrical back and forth with respect to the compression top dead center is required, but in the second embodiment, this is not necessary. Therefore, in the case of the combustion start detection device of the second embodiment, the range of the crank angle for sampling the in-cylinder pressure may be set to, for example, a range of −10 ° CA to + 20 ° CA.

In each of the embodiments, the sampling cycle θs of the in-cylinder pressure is set to 5 ° CA. However, this is merely an example, and depending on the case where the crank angle range of the in-cylinder pressure sampling is narrowed or the performance of the processing device, etc. Alternatively, the sampling period θs may be shorter (for example, 2 ° CA). The determination thresholds ΔP ₀ and dQ ₀ can be set to appropriate values.

[0079]

As described above in detail, according to the combustion start detecting apparatus for an internal combustion engine according to the first aspect of the present invention, the in-cylinder pressure at the predetermined crank angle in the expansion stroke is changed to the predetermined crank angle in the expansion stroke. On the other hand, a pressure difference is calculated by subtracting the in-cylinder pressure at a predetermined crank angle at the time of the compression stroke at a position symmetrical with respect to the compression top dead center, and when the pressure difference exceeds a predetermined value, it is assumed that combustion has occurred. Thus, it can be determined that combustion has started between the crank angle in the expansion stroke when the pressure difference exceeds a predetermined value and the previous crank angle.

Therefore, the start of combustion can be determined from the small in-cylinder pressure sample detected corresponding to the crank angle without imposing a load on the arithmetic processing system, and of course, in real time while operating the engine. be able to. Thus, for example, the fuel injection timing can be more appropriately controlled by the timer piston.

According to the combustion start detecting apparatus for an internal combustion engine of the present invention, the heat release rate correlation value is calculated from a plurality of adjacent in-cylinder pressures detected by the in-cylinder pressure detecting means.
If the heat release rate correlation value exceeds a predetermined value, it can be considered that combustion has occurred, and the crank angle in the expansion stroke when the heat release rate correlation value exceeds the predetermined value and the previous crank angle Can be determined that combustion has started.

Therefore, the start of combustion can be more appropriately determined from the small in-cylinder pressure sample detected corresponding to the crank angle without imposing a load on the arithmetic processing system. Can be determined. Thus, for example, the fuel injection timing can be more appropriately controlled by the timer piston.

According to the third aspect of the present invention, the position of the timer piston is controlled by the control means in accordance with the target fuel injection timing set by the target fuel injection timing setting means. Although the fuel pressurization timing by the pump is adjusted, the target fuel injection timing setting means sets the target fuel injection timing by correcting the detection result of the combustion start timing detection means in consideration of the fuel transfer delay and the like. Therefore, it is possible to set a target fuel injection timing while avoiding a shift in combustion timing due to a fuel transfer delay, and it is possible to appropriately control the combustion start timing by appropriately controlling the fuel injection timing. There are advantages.

According to the control device for an internal combustion engine of the present invention, the target fuel injection timing setting means starts combustion in accordance with the length of the high-pressure fuel pipe and the rotation speed detected by the rotation speed detection means. Correction to the detection result of the timing detection means enables the target fuel injection timing to be set while reliably correcting the fuel transfer delay, and the appropriate control of the fuel injection timing to appropriately control the combustion start timing. There are advantages to being able to.

According to the control device for an internal combustion engine of the present invention, the target fuel injection timing setting means controls the combustion start timing detection means according to the period from the start of fuel injection to the start of combustion by the injected fuel. Since the detection result is corrected, the target fuel injection timing can be set appropriately,
By controlling the fuel injection timing appropriately, there is an advantage that the combustion start timing can be appropriately controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a combustion start detection device and a control device of an internal combustion engine according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating detection of combustion start by a combustion start detection device for an internal combustion engine according to a first embodiment of the present invention, wherein FIG. 2A shows a cylinder pressure change characteristic, and FIG. Are shown corresponding to the in-cylinder pressure change characteristics.

FIG. 3 is a diagram illustrating transfer delay correction by a control device for an internal combustion engine according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining transfer delay correction by the control device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 5 is a flowchart (injection timing setting routine) illustrating fuel injection timing control by the control device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 6 is a flowchart (timer interrupt routine) illustrating fuel injection timing control by the control device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 7 is a flowchart (crank angle interrupt routine) illustrating detection by the combustion start detection device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 8 is a flowchart (crank angle interrupt routine) illustrating detection by the combustion start detection device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 9 is a flowchart (combustion start timing detection routine) illustrating combustion start detection by the combustion start detection device for the internal combustion engine according to the first embodiment of the present invention.

FIG. 10 is a block diagram illustrating a configuration of a combustion start detection device for an internal combustion engine according to a second embodiment of the present invention.

FIG. 11 is a flowchart (combustion start timing detection routine) illustrating combustion start detection by a combustion start detection device for an internal combustion engine according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Combustion start detecting means (combustion start detecting device of internal combustion engine) 11 In-cylinder pressure intake means 12 Subtraction means 13 Subtraction result judgment means 14 Combustion start judgment means 15 Correlation value calculation means 16 Correlation value judgment means 17 Combustion start judgment means 20 Target Fuel injection timing setting means 21 PI controller 22 Correction function unit (correction means) 30 Target combustion start timing setting means 40 Timer position controller (control means) 50 Fuel injection pump 51 Plunger pump 52 Injection timing control mechanism 54 Timer piston 56 Timer control valve (TCV) 58 Fuel supply pipe 60 Fuel injection valve (needle valve) 81 Engine speed sensor 82 Engine load sensor (accelerator position sensor) 83 In-cylinder pressure sensor 84 Crank angle sensor

Claims (5)

[Claims] 1. An in-cylinder pressure intake means for acquiring and storing in-cylinder pressure detection information in a combustion chamber for each predetermined crank angle within a predetermined crank angle range centered on a compression top dead center of an internal combustion engine; Based on the in-cylinder pressure detection information taken in by the take-in means, based on the in-cylinder pressure at a predetermined crank angle in the expansion stroke, the compression stroke at a position symmetrical with respect to the compression top dead center with respect to the predetermined crank angle in the expansion stroke. Subtraction means for subtracting the in-cylinder pressure at a predetermined crank angle at the time; subtraction result determination means for determining whether the subtraction result by the subtraction means has exceeded a predetermined value; Combustion start determining means for determining that combustion has started between the crank angle in the expansion stroke and the previous crank angle when the subtraction result exceeds the predetermined value. A combustion start detection device for an internal combustion engine, comprising: 2. In-cylinder pressure intake means for acquiring and storing in-cylinder pressure detection information in a combustion chamber for each predetermined crank angle within a predetermined crank angle range centered on the compression top dead center of the internal combustion engine; Correlation value calculating means for calculating a heat generation rate correlation value from a plurality of adjacent in-cylinder pressures based on the in-cylinder pressure detection information taken into the taking means; and the heat generation rate correlation calculated by the correlation value calculating means. A correlation value determining means for determining whether or not the value exceeds a predetermined value; and if the correlation value determining means determines that the heat release rate correlation value exceeds the predetermined value, the heat release rate correlation value becomes Combustion start detection means for determining that combustion has started between a crank angle in an expansion stroke when the predetermined value is exceeded and a previous crank angle. apparatus. 3. A plunger pump provided in a fuel injection pump of a diesel internal combustion engine to pressurize fuel to a high pressure, and a fuel injection timing from a fuel injection valve is adjusted by adjusting a fuel pressurization timing by the plunger pump. A timer piston for controlling, a combustion start timing detecting means for detecting a combustion start timing of the diesel internal combustion engine, and a target fuel by performing a correction in consideration of a fuel transfer delay or the like to a detection result of the combustion start timing detecting means. Target fuel injection timing setting means for setting the injection timing; and control means for controlling the position of the timer piston according to the target fuel injection timing set by the target fuel injection timing setting means. Control device for an internal combustion engine. 4. A target fuel injection timing setting means, further comprising: a high-pressure fuel pipe for delivering high-pressure fuel to the fuel injection valve; and a rotation speed detection means for detecting a rotation speed of the diesel internal combustion engine. 4. The control device for an internal combustion engine according to claim 3, wherein the controller performs the correction in accordance with the length of the high-pressure fuel pipe and the rotation speed detected by the rotation speed detection means. 5. The target fuel injection timing setting means performs the correction in accordance with a period from the start of fuel injection from the fuel injection valve to the start of combustion with the injected fuel. A control device for an internal combustion engine according to claim 4.