JP2003343336A - Method for calculating engine torque - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate engine torque with accuracy higher than that in correcting basic torque only by a specified parameter. <P>SOLUTION: When final engine torque Qfin is calculated, basic engine torque TQbse is calculated based on the engine speed and fuel injection quantity of an engine (Step 110). The deviation Qdlt between fuel injection quantity command vale and actual fuel injection quantity is estimated from the control signals (signals of pilot injection quantity Qpl and pilot injection time Intp) of fuel injection quantity and fuel injection time (Step 180). A correction value dTQ is calculated based on the deviation Qdlt as output torque that is the quantity of influence exerted on final engine torque Qfin (Step 190). The final engine torque Qfin is calculated by correcting the basic engine torque TQbse using this correction value dTQ (Steps 100 and 210). <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 method of calculating a basic engine torque based on an engine speed and a fuel injection amount, and correcting the basic engine torque to calculate the engine torque.

[0002]

2. Description of the Related Art Techniques for controlling torque in a vehicle, such as transmission control and ABS (Anti lock Br.
ake system) control, traction control, etc. are known. In these techniques, the engine is controlled so that the actual torque becomes the target torque. Further, regarding the above-described transmission control and the like, a control amount is calculated according to the actual torque of the engine, and the actuator is drive-controlled according to the control amount. For example, in the case of transmission control, the control amount of the shift solenoid valve is calculated according to the actual torque of the engine, and the solenoid valve is driven according to the control amount. By this drive, the hydraulic circuit is switched and a predetermined gear position (first speed, second speed, 3
(Speed etc.) is determined and gear shifting is performed. Further, in the ABS control, the control amount of the brake hydraulic pressure of the wheel cylinder is calculated according to the actual torque of the engine, and the actuator is driven according to the control amount. By this drive, the brake hydraulic pressure is controlled, and the slip ratio between the wheels and the road surface is maintained at a desired value. Therefore, for these transmission controls and the like, it is required to accurately calculate the actual torque (engine torque) in the torque control of the engine.

Here, in an engine, generally, the fuel injection timing, injection pressure, cooling water temperature, etc. change moment by moment depending on environmental conditions, and these changes affect the output torque. That is, the combustion state in the cylinder changes with the above change, and the output of the engine changes even with the same fuel injection amount.

Therefore, for example, Japanese Patent Laid-Open No. 2000-12780.
In No. 7, the engine torque is calculated as follows. First, the basic engine torque is obtained based on the engine rotation speed and the fuel injection amount. Further, the correction coefficient is obtained from parameters that are considered to affect the engine torque, such as intake air amount and intake pressure. Then, the engine torque is calculated by correcting the basic engine torque with this correction coefficient.

[0005]

By the way, in a common rail type diesel engine engine in which fuel injection is divided into main injection and pilot injection prior to the main injection for the purpose of improving combustion, for example, a command is issued at the time of fuel injection control. There may be a difference between the fuel injection amount and the actual fuel injection amount. For example, if the pilot injection timings are different, the actual injection amount will change even if the command values for the same fuel injection amount are changed. The following are possible reasons for such a difference.

(I) Generally, pilot injection is performed before the top dead center of the compression stroke. From this, when the injection timing of the pilot injection is different, that is, when the interval until the next main injection is different, the in-cylinder pressure at the time when the pilot injection is performed is different. For example, the pilot injection timing approaches the compression top dead center as the interval becomes shorter. As a result, the in-cylinder pressure becomes high, the fuel is less likely to be injected during the main injection, and the injection amount decreases even if the injection time is the same.

(Ii) In a common rail type diesel engine, a supply pump is driven by the diesel engine, and fuel is pumped from the supply pump to the common rail. The fuel is temporarily stored in the common rail and then injected into the combustion chamber by opening the valve of the injector. In the diesel engine with this configuration, fuel is pumped from the supply pump to the common rail at a constant pressure. Under this circumstance, the injection of fuel from the injector releases a certain amount of fuel in the pipeline from the supply pump to the injector. With this release, the injection pressure temporarily drops. This decrease in the injection pressure affects the injection pressure of the main injection, but the amount of influence differs depending on the pilot injection timing. As a result, even if the command value of the fuel injection amount is the same, the fuel injection amount of the main injection differs depending on the pilot injection timing.

If a difference occurs between the commanded fuel injection amount and the actual fuel injection amount as described above, the engine torque is affected by the difference. In this respect, in the technique of the above-mentioned publication, only a single correction coefficient is set according to the type of parameter, and the influence of the above-mentioned deviation on the output torque is not considered. With this, if a difference occurs between the command value of the fuel injection amount and the actual fuel injection amount, it is not possible to calculate the engine torque that reflects the difference. Therefore, the method disclosed in the above publication has a limit in improving the calculation accuracy of the engine torque.

The present invention has been made in view of the above circumstances, and an object thereof is to improve the engine torque with higher accuracy than in the case of correcting the basic engine torque with a single correction coefficient according to the type of parameter. It is to provide a calculation method capable of calculating.

[0010]

[Means for Solving the Problems] Means for achieving the above-mentioned objects and their effects will be described below. In the invention according to claim 1, the basic engine torque is calculated based on the engine rotation speed and the fuel injection amount of the engine,
In the method of calculating the engine torque by correcting the basic engine torque, the deviation between the fuel injection amount command value and the actual fuel injection amount is estimated from each control signal for the fuel injection amount and the injection timing, The output torque is calculated based on this deviation, and the basic engine torque is corrected with this output torque.

According to the above calculation method, the basic engine torque is calculated based on the engine rotation speed and the fuel injection amount. This basic engine torque is the torque in the standard state of the engine. Further, when the actual fuel injection amount is different from the fuel injection amount command value, the engine torque is affected. Therefore, if the deviation between the fuel injection amount command value and the actual fuel injection amount is known, it is possible to obtain the amount of influence of the deviation on the engine torque. On the other hand, the deviation generally strongly depends on the relationship between the fuel injection amount and the injection timing.

Therefore, in the first aspect of the present invention, the fuel injection amount and the injection timing, which have a close relationship with the deviation, are used, and the deviation is each control signal for the fuel injection amount and the injection timing. It is estimated based on. In this way, the deviation is estimated with high accuracy by using the fuel injection amount and the injection timing for estimating the deviation. Then, based on the estimated deviation, the output torque is calculated as the amount of influence of the deviation on the engine torque. The engine torque is calculated by correcting the basic engine torque with this output torque.

Therefore, even if there is a difference between the fuel injection amount command value and the actual fuel injection amount, and the output torque corresponding to the difference affects the engine torque, the engine torque considering the effect is considered. Will be calculated. As a result, it is possible to improve the calculation accuracy of the engine torque as compared with the case where the basic engine torque is corrected with a single correction coefficient set according to the type of parameter.

According to a second aspect of the present invention, in the first aspect of the present invention, a control signal for fuel injection and a basic control signal for fuel injection in an engine in a warm-up state are used, and the control signal of the control signal is used. The degree of change with respect to the basic control signal is calculated, and the basic engine torque is further corrected based on the degree of change.

Here, in the engine, if the state quantity relating to fuel injection, such as the injection timing, the injection pressure, etc., changes due to changes in the environment, etc. , Engine torque changes under the influence. That is, the combustion state changes as the state quantity related to fuel injection changes, and the output of the engine changes even with the same fuel injection quantity.

In this respect, according to the second aspect of the invention, the "control signal for fuel injection" is used as a signal corresponding to the state quantity. Further, the "basic control signal for fuel injection in the engine in the warmed-up state" is used as a signal corresponding to the basic state quantity. Then, the degree of change of the control signal with respect to the basic control signal is calculated, and the basic engine torque is further corrected based on this degree of change. Therefore, even if the state quantity related to the fuel injection deviates from the basic state quantity and the engine torque changes accordingly, it is possible to calculate the engine torque in consideration of the change amount by correcting the basic engine torque using the degree of change. It becomes possible and the calculation accuracy becomes higher.

According to a third aspect of the present invention, in the second aspect of the present invention, when correcting the basic engine torque, a first correction coefficient corresponding to the degree of change and the engine rotation speed is obtained. The basic engine torque is corrected with the first correction coefficient.

According to the above calculation method, when correcting the basic engine torque, the first correction coefficient corresponding to the degree of change and the engine rotation speed is obtained, and the basic engine torque is corrected by this first correction coefficient. The engine speed is
It is one of the parameters that influence the engine torque. Therefore, by adding the engine rotation speed in this way, it is possible to improve the accuracy of correction of the basic engine torque using the degree of change.

According to the invention described in claim 4,
In the invention as described in any one of 1 above, prior to the correction of the basic engine torque using the output torque, among the second correction coefficients corresponding to the output torque per unit fuel injection amount, the engine rotational speed at that time is set. The output torque is calculated by calculating a corresponding value and correcting the deviation with the second correction coefficient.

Here, in the above-described invention according to claim 1, the deviation between the fuel injection amount command value and the actual fuel injection amount differs depending on the engine speed. In this respect,
According to the invention described in claim 4, the second correction coefficient is calculated separately from the estimation of the deviation between the fuel injection amount command value and the actual fuel injection amount. The second correction coefficient corresponds to the output torque per unit fuel injection amount, and is set for each engine speed. Then, the second correction coefficient corresponding to the engine rotation speed at that time is calculated, and the output torque is calculated by correcting the deviation by the second correction coefficient. Therefore, by using the second correction coefficient in which the engine rotation speed is added in this way, it is possible to improve the calculation accuracy of the output torque.

According to a fifth aspect of the invention, in the fourth aspect of the invention, prior to the correction of the basic engine torque using the output torque, a control signal for fuel injection and fuel for the engine in a warmed-up state are provided. A basic control signal for injection is used to calculate the degree of change of the control signal with respect to the basic control signal, and the output torque after correction using the second correction coefficient is further corrected based on the degree of change. I shall.

Here, in the engine, if the state quantity relating to fuel injection, such as the injection timing, the injection pressure, etc., changes due to environmental changes, etc., and deviates from the basic state quantity relating to fuel injection in a warmed-up engine. , Engine torque changes under the influence. That is, the combustion state changes as the state quantity related to fuel injection changes, and the output of the engine changes even with the same fuel injection quantity.

In this respect, in the invention described in claim 5, the "control signal for fuel injection" is used as a signal corresponding to the state quantity. Further, the "basic control signal for fuel injection in the engine in the warmed-up state" is used as a signal corresponding to the basic state quantity. Then, the degree of change of the control signal with respect to the basic control signal is calculated, and the output torque after correction using the second correction coefficient is further corrected based on this degree of change. Therefore, even if the state quantity related to fuel injection deviates from the basic state quantity and the engine torque changes accordingly, it is possible to calculate the output torque in consideration of the change by the correction using the degree of change.

According to the invention of claim 6, the inventions of claims 1 to 5
In one aspect of the present invention, a plurality of fuels including a predetermined fuel injection and a fuel injection immediately before that affects a fuel injection amount of the predetermined fuel injection during one combustion stroke of the engine. It is assumed that the injection is performed and the deviation is estimated based on the control signal regarding the injection amount of the immediately preceding fuel injection and the control signal regarding the injection timing.

According to the above calculation method, the injection amount and the injection timing of the immediately preceding fuel injection having a close relationship with the deviation are used, and the deviation is used as each control signal for the injection amount and the injection timing. It is estimated based on Therefore, in an engine that performs a plurality of fuel injections during one combustion stroke, it is possible to calculate the deviation and thus the engine torque with high accuracy.

According to the invention described in claim 7, in the invention described in claim 6, the plurality of fuel injections in the one combustion stroke include a main injection and a pilot injection performed prior to the main injection. The deviation is estimated based on a control signal for the pilot injection amount and a control signal for the pilot injection timing.

According to the above calculation method, the injection amount and the injection timing of the pilot injection, which have a close relationship with the deviation, are used, and the deviation indicates the pilot injection amount control signal and the pilot injection timing. It is estimated based on the control signal. Therefore, in the engine that performs the pilot injection and the main injection during one combustion stroke, it is possible to calculate the deviation and thus the engine torque with high accuracy.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. FIG. 1 is a schematic configuration diagram of a diesel engine 11 mounted on a vehicle. The diesel engine 11 has a plurality of cylinders 12. The diesel engine 11 is provided with injectors 13 corresponding to the combustion chambers of the cylinders 12, respectively, and fuel is injected from the injectors 13 into the combustion chambers. The injector 13 is a solenoid valve 1 for injection control.
4, the fuel injection by the injector 13 is controlled based on the opening / closing operation of the electromagnetic valve 14. The combustion of this fuel rotates the crankshaft (not shown) that is the output shaft. The rotation of the crankshaft is changed by a transmission (not shown), and the changed rotation is transmitted to the drive wheels.

Here, the combustion process in the diesel engine 11 can be roughly divided into a premixed combustion period and a diffusion combustion period following the premixed combustion period. In the premixed combustion period,
The fuel injected into the combustion chamber becomes a combustible mixture and self-ignites, so that the combustion of the fuel rapidly progresses. Then, in the diffusion combustion period, the fuel is injected into the combustion gas generated in the combustion chamber during the premixed combustion period, so that the combustion of the fuel continues. By the way, during the premixed combustion period, since the combustion rapidly progresses as described above, the rate of increase of the combustion pressure in the combustion chamber tends to increase, and the combustion temperature tends to become extremely high. Therefore, if this premixed combustion period becomes long, that is, if the proportion of fuel that burns rapidly due to self-ignition increases,
Increased combustion noise and nitrogen oxides (NOx
) Will be increased.

In order to prevent such combustion noise and NOx increase, the diesel engine 11 of the present embodiment is designed to perform pilot injection. That is, after a part of fuel to be injected into the combustion chamber is injected (pilot injection), the fuel injection is temporarily interrupted.
Then, when the pilot-injected fuel is in the ignition state, the remaining fuel is again injected (main injection). The execution of such pilot injection shortens the premixed combustion period and reduces the proportion of fuel that burns rapidly due to self-ignition, so that the combustion pressure rises slowly and the combustion temperature in the combustion chamber also decreases. Therefore, it is possible to prevent an increase in combustion noise and an increase in NOx in the exhaust gas.

In general, pilot injection is performed when the diesel engine 11 is under low load and low rotation. this is,
This is because if the pilot injection is executed even at the time of high load or high rotation, the smoke concentration will increase and the engine output will tend to decrease. Therefore, the fuel injection mode is set to a mode in which pilot injection and main injection are executed (hereinafter referred to as "pilot injection mode") and a mode in which only main injection is executed (hereinafter referred to as "main injection mode"). It is designed to switch according to the operating conditions.

Each injector 13 is connected to a common rail 15 common to each cylinder 12. The common rail 15 is connected to a discharge port 18a of a supply pump 18 via a supply pipe 17 provided with a check valve 16.

Intake port 18b of the supply pump 18
Are connected to a fuel tank 21 via a filter 19. In addition, the return port 18 of the supply pump 18
c and the return port 14a of the solenoid valve 14 are both
The return pipe 22 is connected to the fuel tank 21.

The supply pump 18 has a plunger (not shown) that reciprocates in synchronization with the rotation of the crankshaft of the diesel engine 11, and pressurizes the fuel in the pressurizing chamber (not shown) by the plunger. , The pressurized fuel is pumped from the discharge port 18a to the common rail 15. The fuel pumping amount of the supply pump 18 is adjusted based on the opening / closing operation of a pressure control valve (hereinafter abbreviated as “PCV”) 23 provided near the discharge port 18a.

Various sensors are provided to detect various state quantities relating to the operation of the diesel engine 11.
For example, in the vicinity of the accelerator pedal 24, the pedal 24
An accelerator sensor 31 for detecting the depression amount (accelerator opening ACCP) is provided. Further, the common rail 15 is provided with a fuel pressure sensor 32 for detecting the fuel pressure (fuel pressure PC) therein.

A crank sensor 33 is provided near the crankshaft, and a cam sensor 34 is provided near a camshaft (not shown) that rotates in synchronization with the rotation of the crankshaft. The crank sensor 33 and the cam sensor 34 are sensors for detecting the rotational speed of the crankshaft per hour (engine rotational speed NE) and the rotational angle of the crankshaft (crank angle CA).

The output signals of these sensors 31 to 34 are
Electronic control unit of diesel engine 11 (hereinafter referred to as "EC
(Abbreviated as “U”) 41. ECU 41 is C
It is configured to include a PU, a memory, an input / output circuit, a drive circuit (all not shown), and the like. The ECU 41 executes reading and calculation of various state quantities relating to the operation of the diesel engine 11 based on the output signals of the sensors 31 to 34, and controls the solenoid valve 14 and the PCV 23 to control the fuel injection. To execute.

That is, the ECU 41 uses the accelerator sensor 3
The accelerator opening ACCP and the fuel pressure PC are read based on the respective output signals of 1 and the fuel pressure sensor 32.
Further, the ECU 41 determines the engine speed NE based on the output signals of the crank sensor 33 and the cam sensor 34.
And the crank angle CA are calculated.

Further, the ECU 41 executes control relating to the fuel injection mode, injection amount, injection timing, and injection pressure (fuel pressure PC of the common rail 15) based on the above-mentioned various state quantities. The outline of such fuel injection control will be described below.

[Setting of fuel injection mode] When setting the fuel injection mode, the ECU 41 determines, for example, the accelerator opening ACCP.
And the basic injection amount Qmain based on the engine speed NE
Calculate b. This basic injection amount Qmainb most accurately reflects the operating state of the diesel engine 11, and is used when calculating various control values related to fuel injection control.

Next, for example, the basic pilot injection amount Qplb is calculated based on the basic injection amount Qmainb and the engine speed NE. This basic pilot injection amount Qplb
Is the amount most suitable for the engine operating state when a sufficient time has elapsed since the fuel injection mode was switched from the main injection mode to the pilot injection mode in consideration of combustion noise, smoke concentration, etc. Is set.

Next, the fuel injection mode is set based on the engine operating state. For example, when the engine operating state is in the low load / low speed region, the pilot injection mode is selected as the fuel injection mode. On the other hand, when the engine operating state is in the high load and high rotation range, the main injection mode is selected as the fuel injection mode.

[Fuel injection timing control and fuel injection amount control]
Next, the control relating to the fuel injection timing and the fuel injection amount, which is executed based on the fuel injection mode selected as described above, will be described.

FIG. 3 is a timing chart showing the manner of changing the on / off state of the solenoid valve 14 controlled by the ECU 41. FIG.
(B) shows the same change mode in the main injection mode, respectively.

[Pilot injection mode] When the pilot injection mode is selected as the fuel injection mode,
The ECU 41 executes both pilot injection and main injection. That is, as shown in FIG.
1 indicates that the current crank angle CA is the pilot injection timing Int
When it becomes p, an ON signal (valve opening signal) is output to the solenoid valve 14. In response to this signal, the injector 13
Is opened and pilot injection is started.

The pilot injection timing Intp is defined as a relative angle before the main injection timing Inj with reference to the main injection timing Inj. Therefore, the pilot injection timing Intp corresponds to the time interval (crank angle interval, interval) between the pilot injection start timing and the main injection start timing.

The main injection timing Inj is a timing at which the main injection is started, and is calculated based on, for example, the engine speed NE and the basic injection amount Qmainb. The main injection timing Inj is defined as a relative angle after the compression top dead center with reference to the compression top dead center (indicated as “TDC” in the figure) of the cylinder 12 that is trying to inject fuel.

As described above, when the ON signal is output to the solenoid valve 14 and the predetermined period Tp elapses after the injector 13 is opened, the ECU 41 causes the solenoid valve 14 to output the OFF signal ( The valve closing signal) is output. In response to this signal, the injector 13 is closed and pilot injection is stopped. The predetermined period Tp is, for example, the pilot injection amount Qpl and the fuel pressure P of the common rail 15.
It is determined based on C and. Here, the pilot injection amount Qpl is the amount of fuel injected into the combustion chamber during execution of pilot injection. After the pilot injection is thus executed, the fuel injection by the injector 13 is performed for a predetermined period Toff.
During that time, it will be temporarily stopped.

Next, a predetermined period T from the pilot injection stop
When the current crank angle CA reaches the main injection timing Inj after off has passed, the ECU 41 turns on the solenoid valve 14.
Output a signal. In response to this signal, the injector 13 is opened again and the main injection is started.

Then, the ECU 41 outputs the OFF signal to the solenoid valve 14 again after a lapse of a predetermined period Tm from the start of the main injection. In response to this signal, the injector 13 is closed and main injection is stopped. The predetermined period Tm is determined based on, for example, the final main injection amount Qmain and the fuel pressure PC of the common rail 15. Here, the final main injection amount Qmain is the amount of fuel injected into the combustion chamber during execution of the main injection, and is the basic injection amount Q
It is calculated by subtracting the pilot injection amount Qpl from mainb.

[Main injection mode] On the other hand, when the main injection mode is selected as the fuel injection mode, the ECU 41 executes only the main injection. That is, as shown in FIG. 3B, the ECU 41 outputs an ON signal to the solenoid valve 14 when the current crank angle CA reaches the main injection timing Inj. In response to this signal, the injector 13 is opened and main injection is started.

Here, the main injection timing Inj is defined as a relative angle after the compression top dead center with reference to the compression top dead center like the main injection timing Inj in the pilot injection mode.

Then, when the predetermined period Tm has elapsed since the main injection was started, the ECU 41 determines that the solenoid valve 14
An OFF signal is output to. In response to this signal, the injector 13 is closed and main injection is stopped.

[Fuel Injection Pressure Control] Next, the fuel injection pressure,
That is, the control related to the fuel pressure of the common rail 15 will be described.

The ECU 41 calculates a basic injection pressure Pcrb which is a target pressure related to the fuel pressure of the common rail 15.
The basic injection pressure Pcrb is set based on, for example, the engine rotational speed NE and the basic injection amount Qmainb so as to be a pressure most suitable for the engine operating state in consideration of combustion noise, smoke concentration, and the like.

The ECU 41 calculates the injection pressure Pcr by correcting the basic injection pressure Pcrb thus calculated. Then, the ECU 41 feedback-controls the open / closed state of the PCV 23 so that the fuel pressure PC of the common rail 15 detected by the fuel pressure sensor 32 matches the injection pressure Pcr, and adjusts the fuel pressure feed amount from the supply pump 18. To do.

In addition, the ECU 41 controls the engine torque of the diesel engine 11 (final engine torque TQ
(fin) is calculated. Next, the procedure for calculating the final engine torque TQfin will be described with reference to the flowchart of FIG.

First, in step 110, the ECU 41 starts the basic engine torque TQbs, which is the torque of the diesel engine 11 in the standard state (fully warmed up state).
Calculate e. In this calculation, for example, the engine speed NE and the fuel injection amount (basic injection amount Qmainb)
Refer to the two-dimensional map that defines the relationship with the basic engine torque TQbse. The engine speed NE and the fuel injection amount are parameters considered to have a relatively large influence on the final engine torque TQfin. The above map shows the final engine torque TQ obtained by variously changing the engine speed NE and the fuel injection amount through experiments or the like.
It was created by measuring fin. At the time of this measurement, among the parameters that are considered to affect the final engine torque TQfin, the parameters other than the engine speed NE and the fuel injection amount described above, such as the intake air amount, are kept constant. Then, the basic engine torque TQbse in the operating state at that time, that is, the basic engine torque TQbse corresponding to the engine rotation speed NE and the fuel injection amount is obtained from the map.

Next, at step 120, it is judged if the fuel form set based on the engine operating condition is the pilot injection mode. If this determination condition is satisfied (pilot injection mode), step 13
At 0 and 140, the first correction coefficient a, b, c, d is calculated. These first correction coefficients a to d are coefficients corresponding to the amount of change in the final engine torque TQfin when the predetermined parameter affecting the final engine torque TQfin changes by a unit amount.

Specifically, at step 130, the degree of change of the control signal of the diesel engine 11 with respect to the basic control signal is calculated. Here, the control signal is a control signal for fuel injection of the diesel engine 11, and is, for example, the injection pressure Pcr, the main injection timing Inj, the pilot injection amount Qpl, and the pilot injection timing Intp. The basic control signal is a control signal regarding the injection pressure, the main injection timing, the pilot injection amount, and the pilot injection timing when the diesel engine 11 is in a sufficiently warmed-up state. Basic injection pressure Pcrb, basic main injection timing Injb,
The basic pilot injection amount Qplb and the basic pilot injection timing Intpb correspond to this basic control signal.

Then, in this step 130, the ratio (Pcr / Pcrb) of the injection pressure Pcr to the basic injection pressure Pcrb is calculated as ΔPcr. The ratio (Inj / Injb) of the main injection timing Inj to the basic main injection timing Injb is ΔInj
Calculate as The ratio (Qpl / Qplb) of the pilot injection amount Qpl to the basic pilot injection amount Qplb is calculated as ΔQpl. The ratio of the pilot injection timing Intp to the basic pilot injection timing Intpb (Intp / Intpb) is Δ
Calculate as Intp.

Next, at step 140, the first correction coefficient a based on the engine speed NE and the ratio ΔPcr.
And a first correction coefficient b is calculated based on the engine speed NE and the ratio ΔInj. Engine speed NE
Also, the first correction coefficient c is calculated based on the ratio ΔQpl, and the first correction coefficient d is calculated based on the engine rotation speed NE and the ratio ΔIntp. When calculating these, for example, a two-dimensional map that defines the relationship between the engine rotation speed NE, the ratio ΔPcr, and the like and the first correction coefficient a and the like is used. For example, regarding the map for calculating the first correction coefficient a, how much the final engine torque TQfin changes when the actual injection pressure Pcr changes with respect to the basic injection pressure Pcrb is measured for each engine rotation speed. Then, the first correction coefficient a (0 <a ≦ 1) is determined based on the measurement result. In this way, when the first correction coefficients a to d are calculated from the corresponding two-dimensional maps, these values are stored in the memory and then the process proceeds to step 170.

On the other hand, if the determination condition of step 120 is not satisfied (main injection mode), the first correction coefficients a to d are calculated in steps 150 and 160.

First, in step 150, the degree of change of the control signal of the diesel engine 11 with respect to the basic control signal is calculated in the same manner as in step 130. However, pilot injection is not performed in the main injection mode (Qpl = 0). This is the basic engine torque TQbs
In order not to affect the correction of e, it is necessary to set the first correction coefficients c and d related to pilot injection to "1" as described above. First correction coefficient c, d
Is known, it is not necessary to calculate the ratios ΔQpl and ΔIntp. Therefore, in step 150, the ratios ΔPcr (= Pcr / Pcrb) and ΔInj (= Injj irrelevant to the pilot injection are generated.
/ Injb) only is calculated.

In step 160, the engine speed N
A first correction coefficient a is calculated based on E and the ratio ΔPcr,
The first correction coefficient b is calculated based on the engine speed NE and the ratio ΔInj. The first correction coefficients c and d are set to "1". Then, these first correction coefficients a to
After storing d in the memory, the process proceeds to step 170.

In step 170, the corrected torque TQcor is calculated according to the following equation (1). That is, the first correction coefficient a calculated in step 140 or 160
The corrected torque TQcor is calculated by correcting the basic engine torque TQbse using .about.d.

TQcor = a.b.c.d.TQbse (1) By complying with the above equation (1), the basic engine torque TQbs
A corrected torque TQcor is calculated by correcting e based on the injection pressure Pcr, the main injection timing Inj, the pilot injection amount Qpl, and the pilot injection timing Intp.

Here, the above-mentioned steps 130 and 14
When the injection timing, the injection pressure, the injection amount, etc. of the pilot injection are changed under the constant fuel injection amount, the combustion state that changes accordingly is calculated as the corrected torque TQcor by performing the processes of 0 and 170. . By the way, the corrected torque TQcor does not include a change amount of the final engine torque TQfin when the fuel injection amount changes. Therefore, this deficiency is eliminated in the next step 180
It is calculated by the processing of ~ 200.

In step 180, the deviation Qdlt between the fuel injection amount command value and the actual injection amount is estimated. Here, the deviation Qdlt is one of the factors that influence the final engine torque TQfin, and strongly depends on the relationship between the pilot injection amount Qpl and the pilot injection timing Intp. Therefore, for example, a two-dimensional map that defines the relationship between the deviation Qdlt and the pilot injection amount Qpl and the pilot injection timing Intp is created in advance. Then, by using this map, the deviation Qdlt corresponding to the pilot injection amount Qpl and the pilot injection timing Intp at that time is estimated.

In step 190, the correction value dTQ is calculated as the output torque which is the amount of influence of the deviation Qdlt on the final engine torque TQfin. Specifically, the second correction coefficient α corresponding to the engine rotation speed NE at that time is obtained. The second correction coefficient α is a coefficient corresponding to the output torque (correction value dTQ) per unit fuel injection amount. That is, the deviation Qdlt differs depending on the engine speed NE, and the output torque (correction value dT
Q) is also different. Therefore, for example, a one-dimensional map that defines the relationship between the engine rotation speed NE and the second correction coefficient α is created in advance. By referring to this map,
A second correction coefficient α corresponding to the engine rotation speed NE at that time is calculated. Then, the correction value dTQ is calculated according to the following equation (2).

DTQ = α · Qdlt (2) In step 200, the above-mentioned step 140 or 16
Using the first correction coefficients a to d previously calculated at 0 and the correction value dTQ obtained at step 190, the final correction value TQdlt is calculated according to the following equation (3).

TQdlt = a.b.c.d.dTQ (3) The final correction value TQdlt calculated according to the above equation (3) is
The state is not sufficiently warmed up but corresponds to the operating state of the diesel engine 11 which is changing every moment.

Next, at step 210, the final engine torque TQfin is calculated according to the following equation (4) using the corrected torque TQcor obtained at step 170 and the final correction value TQdlt obtained at step 200. .

TQfin = TQcor + TQdlt (4) Then, after the processing of step 210, the engine torque calculation routine is completed.

According to this embodiment described in detail above, the following effects can be obtained. (1) Deviation Q between the actual fuel injection amount and the fuel injection amount command value
Paying attention to the close relationship between dlt and the fuel injection amount and injection timing, each control signal (pilot injection amount Qpl, pilot injection timing Intp) for these fuel injection amount and injection timing is estimated. Used (step 1
80). Therefore, the deviation Qdlt can be estimated with high accuracy. Therefore, even if a difference occurs between the fuel injection amount command value and the actual fuel injection amount, and the output torque corresponding to the difference influences the final engine torque TQfin, the final engine torque considering the influence TQfin can be calculated. As a result, in the present embodiment, the final engine torque TQfin is compared with the prior art in which only a single correction coefficient is set according to the type of parameter and the influence of the deviation on the final engine torque TQfin is not considered. The calculation accuracy of can be improved.

(2) Particularly, in this embodiment, pilot injection and main injection are performed during one combustion stroke of the diesel engine 11. The pilot injection affects the fuel injection amount of the main injection. The deviation Qdlt between the actual fuel injection amount and the fuel injection amount command value described above strongly depends on the relationship between the injection amount (pilot injection amount Qpl) and the injection timing (pilot injection timing Intp) in the pilot injection. For example, the point that the pilot injection timing Intp affects the deviation Qdlt is as described in the related art.

In this respect, in the present embodiment, the pilot injection amount Q having a close relationship with the deviation Qdlt as described above.
Since pl and the pilot injection timing Intp are used for estimation (step 180), the obtained deviation Qdlt is highly accurate.

(3) In the diesel engine 11, the state quantity relating to fuel injection, such as the injection timing and the injection pressure, changes due to environmental changes, etc., and the basic state quantity relating to fuel injection in the warm-up state diesel engine 11 , The final engine torque TQfin changes under the influence. That is, the combustion state changes as the state quantity related to fuel injection changes, and the final engine torque TQfin changes even with the same fuel injection quantity.

In this respect, in the present embodiment, the injection pressure Pcr, the main injection timing Inj, the pilot injection amount Qpl and the pilot injection timing Intp are used as those corresponding to the state quantity related to the fuel injection. Further, the basic injection pressure Pcrb, the basic main injection timing Injb, the basic pilot injection amount Qplb and the basic pilot injection timing Intpb are used as those corresponding to the basic state amount. In addition to the correction using the correction value dTQ and the final correction value TQdlt, the degree of change of the control signal with respect to the basic control signal (ratio ΔPcr, ΔInj, Δ
Qpl, ΔIntp) is calculated, and the basic engine torque TQbse is corrected based on the degree of change thereof (steps 130 to 170). Therefore, even if the state quantity related to the fuel injection deviates from the basic state quantity and the final engine torque TQfin changes accordingly, the final engine torque TQfin considering the amount of change is corrected by correcting the basic engine torque TQbse using the degree of change. Can be calculated.

(4) In correcting the basic engine torque TQbse, the degree of change (ΔPcr, ΔInj, ΔQpl, ΔInt)
p) and the engine speed NE, the first correction coefficients a to d are calculated (steps 130 to 160), and the basic engine torque TQbse is calculated by these first correction coefficients a to d.
Is corrected (step 170). Here, the engine rotation speed NE is one of the parameters that influence the final engine torque TQfin. Therefore, by adding the engine speed NE in this manner, the accuracy of correction of the basic engine torque TQbse using the degree of change can be increased.

(5) Deviation Qdlt is the engine speed NE
Will vary depending on. In this regard, in the present embodiment, the second correction coefficient α is calculated separately from the estimation of the deviation Qdlt (step 190). The second correction coefficient α corresponds to the output torque per unit fuel injection amount and is set for each engine rotation speed NE. Then, the second correction coefficient α corresponding to the engine rotation speed NE at that time is calculated,
The output torque (correction value dTQ) is calculated by correcting the deviation Qdlt by the second correction coefficient α (step 190). Therefore, the engine speed NE
By using the second correction coefficient α in consideration of, the calculation accuracy of the output torque (correction value dTQ) can be increased.

(6) Based on the first correction coefficients a to d corresponding to the degree of change (ΔPcr, ΔInj, ΔQpl, ΔIntp) and the engine speed NE in (3) above,
Output torque after correction using the second correction coefficient α (correction value d
TQ) is further corrected (step 200). Therefore, even if the state quantity related to fuel injection deviates from the basic state quantity and the final engine torque TQfin changes accordingly, the degree of change, that is, the first correction coefficients a to d.
By using the correction, the final correction value TQdlt can be calculated as the output torque in consideration of the change.

The present invention can be embodied in another embodiment shown below. The present invention is applicable to an engine of the type in which fuel is injected multiple times during one combustion stroke. That is, the present invention can be applied to an engine in which a plurality of fuel injections including a predetermined fuel injection and a fuel injection immediately before affecting the fuel injection amount of the predetermined fuel injection are performed during one combustion stroke. In this case, the deviation between the actual fuel injection amount and the fuel injection amount command value strongly depends on the relationship between the injection amount and the injection timing in the immediately preceding fuel injection. Therefore, the injection amount and the injection timing of the immediately preceding fuel injection having a close relationship with the deviation are used, and the deviation is estimated based on the control signals for the injection amount and the injection timing. Therefore, the deviation obtained by this estimation is highly accurate.

Step 120 to the above embodiment
The processing of 160, that is, the correction processing of the basic engine torque TQbse based on the degree of change of the control signal with respect to the basic control signal may be omitted. In this case, in step 210, the basic engine torque TQbse is used instead of the corrected torque TQcor.

The processing of step 200 in the above embodiment, that is, the correction value dT using the first correction coefficients a to d
The correction process of Q may be omitted. In this case, step 2
In 10, the correction value dTQ is used instead of the final correction value TQdlt.

The method of calculating the engine torque of the present invention is
It can be applied not only to diesel engines but also to gasoline engines.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine to which an engine torque calculation method is applied in an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for calculating engine torque.

FIG. 3A is a timing chart showing a change mode of an on / off state of a solenoid valve in a pilot injection mode, and FIG. 3B is a timing chart showing the same change mode in a main injection mode.

[Explanation of symbols]

11 ... Diesel engine, a, b, c, d ... First correction coefficient, α ... Second correction coefficient, dTQ ... Correction value (output torque), Inj ... Main injection timing, Injb ... Basic main injection timing, Intp ... Pilot Injection timing, Intpb ... Basic pilot injection timing, NE ... Engine speed, Pcr ... Injection pressure, Pcrb ... Basic injection pressure, Qpl ... Pilot injection amount, Q
plb: Basic pilot injection amount, Qdlt: Deviation, TQbse
… Basic engine torque, TQfin… Final engine torque (engine torque), ΔPcr, ΔInj, ΔQpl, ΔInt
p ... ratio (degree of change).

Claims (7)

[Claims] 1. A method of calculating a basic engine torque on the basis of an engine speed and a fuel injection amount of an engine and calculating the engine torque by correcting the basic engine torque. A deviation from the injection amount is estimated from each control signal for the fuel injection amount and the injection timing, an output torque is calculated based on this deviation, and the basic engine torque is corrected by this output torque. How to calculate engine torque. 2. A control signal for fuel injection and a basic control signal for fuel injection in a warmed-up engine are used to calculate the degree of change of the control signal with respect to the basic control signal, and based on this degree of change. The method of calculating the engine torque according to claim 1, wherein the basic engine torque is further corrected. 3. When correcting the basic engine torque, a first correction coefficient corresponding to the degree of change and the engine rotation speed is obtained, and the basic engine torque is corrected by the first correction coefficient. The method for calculating the described engine torque. 4. Prior to the correction of the basic engine torque using the output torque, a value corresponding to the engine rotation speed at that time is calculated among the second correction coefficients corresponding to the output torque per unit fuel injection amount. The engine torque calculating method according to claim 1, wherein the output torque is calculated by correcting the deviation with the second correction coefficient. 5. A basic control signal for fuel injection and a basic control signal for fuel injection in a warm-up engine are used to correct the basic engine torque using the output torque before correction of the basic engine torque. The engine torque calculating method according to claim 4, wherein a degree of change with respect to the control signal is calculated, and the output torque after correction using the second correction coefficient is further corrected based on the degree of change. 6. A plurality of fuel injections including a predetermined fuel injection and a fuel injection immediately before affecting a fuel injection amount of the predetermined fuel injection are performed during one combustion stroke of the engine, and The engine torque calculation method according to claim 1, wherein the deviation is estimated based on a control signal regarding the injection amount of the immediately preceding fuel injection and a control signal regarding the injection timing. 7. A plurality of fuel injections in the one combustion stroke consist of main injection and pilot injection performed prior to the main injection, and the deviation is related to a control signal for pilot injection amount and pilot injection timing. The method for calculating the engine torque according to claim 6, which is estimated based on the control signal.