阅读说明：本技术 内燃机控制装置 (Control device for internal combustion engine ) 是由 助川义宽 猿渡匡行 佐藤真也 长泽义秋 于 2020-03-27 设计创作，主要内容包括：本发明提供一种内燃机控制装置,能够以对噪声等干扰具有鲁棒性且简易的结构检测燃烧特性来控制发动机。因此,本实施例的内燃机控制装置(ECU12)包括：计算内燃机(发动机(1))的曲柄旋转速度的旋转速度计算部(122a)；计算由旋转速度计算部(122a)计算出的曲柄旋转速度的极值时刻的极值时刻计算部(122b)；和基于由极值时刻计算部(122b)计算出的曲柄速度的极值时刻来推算燃烧状态的燃烧状态推算部(燃烧相位计算部(122c))。(The invention provides an internal combustion engine control device, which can detect combustion characteristics with robustness and simple structure to noise and the like to control an engine. Therefore, the internal combustion engine control device (ECU12) of the present embodiment includes: a rotational speed calculation unit (122a) that calculates the rotational speed of the crank of an internal combustion engine (1)); an extreme value time calculation unit (122b) that calculates the time of an extreme value of the crank rotation speed calculated by the rotation speed calculation unit (122 a); and a combustion state estimation unit (combustion phase calculation unit (122c)) that estimates the combustion state on the basis of the extreme value time of the crank speed calculated by the extreme value time calculation unit (122 b).)

1. A control device for an internal combustion engine, characterized by comprising:

a rotational speed calculation unit that calculates a rotational speed of a crank of the internal combustion engine;

an extreme value time calculation unit that calculates an extreme value time of the crank rotation speed calculated by the rotation speed calculation unit; and

and a combustion state estimating unit that estimates a combustion state based on the extreme value timing of the crank speed calculated by the extreme value timing calculating unit.

2. The internal combustion engine control device according to claim 1, characterized in that:

the internal combustion engine control device includes an internal combustion engine control unit that performs combustion control of the internal combustion engine based on the combustion state estimated by the combustion state estimation unit.

3. The internal combustion engine control device according to claim 1, characterized in that:

the internal combustion engine is configured to drive a generator of a series hybrid system.

4. The internal combustion engine control device according to claim 1, characterized in that:

the waveform indicating the crank rotation speed on the vertical axis relative to the crank angle on the horizontal axis is configured to be sinusoidal.

5. The internal combustion engine control device according to claim 1, characterized in that:

the combustion state estimating unit estimates a combustion phase at which a combustion mass ratio of the internal combustion engine becomes a set value based on a timing at which a crank rotation speed becomes maximum or minimum,

the engine control unit performs combustion control of the internal combustion engine such that the estimated combustion phase becomes a set phase.

6. The control apparatus of the internal combustion engine according to claim 5, characterized in that:

the engine control unit controls an ignition timing of the internal combustion engine so that the estimated combustion phase becomes the set phase.

7. The control apparatus of the internal combustion engine according to claim 5, characterized in that:

the internal combustion engine control unit performs control so that an ignition timing of the internal combustion engine is advanced when the estimated combustion phase is retarded from the set phase.

8. The control apparatus of the internal combustion engine according to claim 5, characterized in that:

the engine control unit controls an EGR valve opening degree of the internal combustion engine so that the estimated combustion phase becomes the set phase.

9. The control apparatus of the internal combustion engine according to claim 5, characterized in that:

the engine control unit controls an opening degree of an EGR valve of the internal combustion engine in a closing direction when the estimated combustion phase is retarded from the set phase.

10. The control apparatus of the internal combustion engine according to claim 8, characterized in that:

the engine control unit controls an EGR valve opening degree of the internal combustion engine such that the estimated combustion phase is an initial combustion period of each cylinder, and a maximum initial combustion period among the initial combustion periods of the cylinders is the set phase.

11. The internal combustion engine control device according to claim 1, characterized in that:

the combustion state estimating unit estimates an initial combustion period of the internal combustion engine based on a timing at which a crank rotation speed becomes maximum or minimum,

the internal combustion engine control unit performs combustion control of the internal combustion engine such that the estimated initial combustion period becomes a set initial combustion period.

12. The internal combustion engine control device according to claim 11, characterized in that:

the engine control unit controls an opening degree of an EGR valve of the internal combustion engine in a closing direction when the estimated initial combustion period is longer than a set initial combustion period.

13. The internal combustion engine control device according to claim 1, characterized in that:

the rotational speed calculation unit calculates the crank rotational speed by performing Fourier series expansion of the time-series values of the crank rotational speed obtained by the rotational angle sensor a finite number of times.

14. The internal combustion engine control device according to claim 13, characterized in that:

the number of truncations of the Fourier series expansion is changed based on the crank rotation speed.

15. The internal combustion engine control device according to claim 1, characterized in that:

the extreme value time calculation unit divides a period of the crank rotation speed time-series value in a period of the crank angle of 720 DEG by the number of cylinders, assigns a crank rotation speed time-series value including a period of the compression top dead center of each cylinder as the crank rotation speed time-series value in the cylinder, and calculates the extreme value time of the crank rotation speed for each cylinder based on the crank rotation speed time-series value assigned to the cylinder.

16. The internal combustion engine control device according to claim 1, characterized in that:

the extreme value time calculation unit approximates the time-series value of the crank rotation speed by using a continuous function based on the discrete time-series value of the crank rotation speed, and calculates the extreme value time of the crank rotation speed by using the continuous function.

Technical Field

The present invention relates to an internal combustion engine control device, and more particularly to a technique for controlling an engine by detecting combustion characteristics with a simple configuration and with robustness against noise and other disturbances.

Background

In recent years, in vehicles such as automobiles, restrictions on fuel consumption (fuel economy) and harmful components in exhaust gas have been strengthened, and these restrictions tend to be strengthened in the future. In particular, the limitation on fuel economy is a matter of great concern due to problems such as an increase in fuel price, an influence on global warming, and exhaustion of energy resources.

In such a situation, a technique is known in which the state in the combustion chamber of the engine is estimated, and the engine is controlled based on the estimation result. By appropriately controlling the ignition timing, the fuel injection timing, and the like in accordance with the current combustion state, the thermal efficiency of the engine can be improved. An example of such a combustion state estimation technique is disclosed in patent document 1, for example.

Patent document 1 describes "means for calculating the rotational acceleration of an engine and means for estimating the combustion state in a combustion chamber based on the rotational acceleration". Patent document 1 describes "calculating a rotational position at which the rotational acceleration of the engine output shaft becomes an extreme value, and estimating the combustion state based on the rotational position".

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2017-150393

Disclosure of Invention

Problems to be solved by the invention

In recent years, however, hybrid vehicles that drive axles by supplying electric power generated by an engine to a motor have become popular. In the hybrid system, the engine can avoid operation at a low load and a low rotational speed, which are low in thermal efficiency, and the thermal efficiency of the entire system can be improved.

On the other hand, in the hybrid system, the engine is often operated under a constant load condition in which the rotation speed is relatively high, and the rotation speed variation in the engine cycle is smaller than that in a general engine vehicle.

In addition, in the hybrid system, the system becomes more complicated and the number of parts becomes larger than that of the engine vehicle. Therefore, simplification of the system and reduction in cost are problems.

In the internal combustion engine control device described in patent document 1, the state in the combustion chamber of the engine is estimated based on the rotational acceleration of the engine. Since the rotational acceleration is a differential value of the rotational speed, when the change in the rotational speed is small, the SN ratio with respect to the rotational acceleration becomes low, and there is a possibility that the estimation accuracy of the combustion state is deteriorated due to noise or the like.

Further, a circuit or software for calculating the rotational acceleration from the rotational speed needs to be installed in the controller, which may complicate the system and increase the cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a simple and low-cost internal combustion engine control device capable of estimating a combustion state robustly with respect to a rotation state of an engine.

Means for solving the problems

In order to solve the above problem, an internal combustion engine control device according to the present invention includes: a rotational speed calculation unit that calculates a rotational speed of a crank of the internal combustion engine; an extreme value time calculation unit that calculates an extreme value time of the crank rotation speed calculated by the rotation speed calculation unit; and a combustion state estimating unit that estimates a combustion state based on the extreme value timing of the crank speed calculated by the extreme value timing calculating unit.

Effects of the invention

According to the present invention, it is possible to provide an internal combustion engine control device that controls an engine by detecting a combustion characteristic with a robust and simple configuration against noise and other disturbances.

Problems, structures, and effects other than those described above will become apparent from the following description of the embodiments.

Drawings

Fig. 1 is an explanatory diagram showing an example of a system configuration of a hybrid vehicle according to an embodiment of the present invention.

Fig. 2 is an explanatory diagram showing an example of a cross section of an engine according to an embodiment of the present invention.

Fig. 3 is an explanatory diagram illustrating a principle of detecting the rotational speed of the crank angle sensor according to the embodiment of the present invention.

Fig. 4 is a block diagram showing an example of the configuration of the controller according to the embodiment of the present invention.

Fig. 5 is an explanatory diagram showing a processing flow of the rotational speed calculation unit of the controller according to the embodiment of the present invention.

Fig. 6 is an explanatory diagram showing a method of obtaining time-series data of the cycle average rotational speed according to the embodiment of the present invention.

Fig. 7 is an explanatory diagram showing a processing flow of the extremum time calculating unit of the controller according to the embodiment of the present invention.

Fig. 8 is an explanatory diagram showing a stroke sequence of a 3-cylinder 4-stroke engine.

Fig. 9 is an explanatory diagram illustrating a method of determining a cylinder window of a 3-cylinder 4-stroke engine according to an embodiment of the present invention.

Fig. 10 is an explanatory diagram showing the definition of the local crank angle (local crank angle) according to the embodiment of the present invention.

Fig. 11 is an explanatory diagram illustrating a method of calculating the maximum speed time in the embodiment of the present invention.

Fig. 12 is an explanatory diagram illustrating a method of calculating the minimum speed time in the embodiment of the present invention.

Fig. 13 is an explanatory diagram illustrating a method of determining the combustion centroid position from the maximum speed time in the embodiment of the present invention.

Fig. 14 is an explanatory diagram illustrating a method of determining the combustion centroid position from the minimum speed time in the embodiment of the present invention.

Fig. 15 is an explanatory diagram illustrating a method of determining an initial combustion position from the maximum speed time in the embodiment of the present invention.

Fig. 16 is an explanatory diagram illustrating a method of determining an initial combustion position from the minimum speed time in the embodiment of the present invention.

Fig. 17 is an explanatory diagram showing an ignition timing control module according to the embodiment of the present invention.

Fig. 18 is a characteristic diagram showing a relationship between the initial combustion period and the variation rate of the combustion torque.

Fig. 19 is an explanatory diagram showing an EGR control module according to an embodiment of the present invention.

Detailed Description

Hereinafter, an example of a mode for carrying out the present invention (hereinafter, referred to as "embodiment") will be described with reference to the drawings. In the present specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description thereof is omitted.

< 1. embodiment 1 > [ System Structure of hybrid vehicle ]

First, an example of a system configuration of a hybrid vehicle to which the present invention is applied will be described.

Fig. 1 shows an example of a system configuration of a hybrid vehicle according to an embodiment of the present invention. In the hybrid vehicle shown in fig. 1, an engine 1, a speed increasing gear 2, and an induction generator 3 are connected in series. The shaft output of the engine 1 is increased in speed by the speed increasing gear 2 to a rotation speed suitable for the induction generator 3, and drives the induction generator 3. The three-phase ac power generated by the induction generator 3 is converted into dc power by the rectifier 4, and then supplied to the inverter 6 and the battery 5. The dc power is again converted into three-phase ac power by the inverter 6, and then supplied to the induction motor 7. The induction motor 7 drives left and right wheels 9 via a transaxle 8.

The controller 12 is an example of a hybrid vehicle control device that controls each component of the hybrid vehicle 50 and executes various data processes. For example, the controller 12 obtains a motor output necessary for driving the vehicle from information such as an accelerator, a brake, a vehicle speed, and a gear position, and controls the inverter 6 to supply a predetermined amount of electric power to the induction motor 7. The controller 12 controls the output of the engine 1, the speed increasing ratio of the speed increasing gear 2, and the exciting current of the induction generator 3, and manages the entire power system of the vehicle. As an example, the controller 12 uses an ECU (Electronic Control Unit).

[ engines ]

Fig. 2 shows an example of a cross section of the engine 1. The engine 1 is an example of a spark-ignition 4-stroke gasoline engine, and a combustion chamber is formed by an engine head and a cylinder 13, a piston 14, an intake valve 15, and an exhaust valve 16. In the engine 1, the fuel injection valve 18 is provided in an engine cylinder head, and an injection nozzle of the fuel injection valve 18 penetrates a combustion chamber, thereby constituting a so-called direct cylinder injection type internal combustion engine. Further, an ignition plug 17 is provided in the engine head. The air for combustion is introduced into the combustion chamber through the air filter 19, the throttle valve 20, and the intake port 21. The burned gas (exhaust gas) discharged from the combustion chamber is discharged to the atmosphere through the exhaust port 24 and the catalytic converter 25.

The amount of air introduced into the combustion chamber is measured by an air flow sensor 22 provided on the upstream side of the throttle valve 20. Further, the air-fuel ratio of the gas (exhaust gas) discharged from the combustion chamber is detected by an air-fuel ratio sensor 27 provided on the upstream side of the catalytic converter 25. Further, a cylinder block (not shown) having a structure in which the cylinder 13 and the crankcase are integrated is provided with the knock sensor 10. The knock sensor 10 outputs a detection signal corresponding to a knock state quantity in the combustion chamber.

The exhaust port 24 and the intake port 21 communicate with each other through an EGR pipe 28, and constitute a so-called exhaust gas recirculation system (EGR) in which a part of the exhaust gas flowing through the exhaust port 24 is returned to the inside of the intake port 21. The amount of gas flowing in the EGR pipe 28 is adjusted by an EGR valve 29.

A timing rotor 26 (signal rotor) is provided on the shaft portion of the crankshaft. The crank angle sensor 11 disposed on the timing rotor 26 detects the rotation and phase of the crankshaft, that is, the engine rotational speed, by detecting a signal of the timing rotor 26. The detection signals of the knock sensor 10 and the crank angle sensor 11 are taken into the controller 12, and used for state detection and operation control of the engine 1 in the controller 12.

The controller 12 outputs the opening degree of the throttle valve 20, the opening degree of the EGR valve 29, the fuel injection timing of the fuel injection valve 18, the ignition timing of the ignition plug 17, and the like, and controls the engine 1 to a predetermined operating state.

In fig. 2, only a single cylinder is shown in order to show the structure of the combustion chamber of the engine 1, but the engine 1 according to the embodiment of the present invention may be a multi-cylinder engine composed of a plurality of cylinders.

[ crank angle sensor ]

Fig. 3 is a diagram showing the principle of detecting the engine rotational speed using the crank angle sensor 11 and the timing rotor 26. Signal teeth 26a are provided at regular angular intervals Δ θ on the circumference of a timing rotor 26 attached to a crankshaft 30 of the engine. The time difference Δ t when the adjacent signal tooth 26a passes through the detection unit of the crank angle sensor 11 is detected by the crank angle sensor 11, and the engine rotation speed ω is obtained as Δ θ/Δ t (rad/s). Since the crank angle sensor is a principle of detecting the rotation speed as described above, the engine rotation speed is detected for each rotation angle Δ θ, and the rotation speed becomes an average speed between the rotation angles Δ θ.

[ controller ]

Fig. 4 is a block diagram showing an example of the configuration of the controller 12. The controller 12 includes an input/output unit 121, a control unit 122, and a storage unit 123 electrically connected to each other via a system bus not shown.

The input/output unit 121 includes an input port and an output port, not shown, and performs input and output processing for each device and each sensor in the vehicle. For example, the input/output unit 121 reads a signal of the crank angle sensor and transmits the signal to the control unit 122. The control unit 122 is an arithmetic processing device, and can use a CPU (central processing unit) and an MPU (micro processing unit). The input/output unit 121 outputs control signals to the respective devices in accordance with instructions from the control unit 122.

The control portion 122 controls the powertrain of the vehicle. For example, the control unit 122 controls the ignition timing, the throttle opening degree, and the EGR opening degree in accordance with the combustion phase of the engine 1 constituted by the internal combustion engine.

The control unit 122 includes a rotational speed calculation unit 122a, an extremum timing calculation unit 122b, a combustion phase calculation unit 122c, and an engine control unit 122 d.

The rotational speed calculation unit 122a averages the time-series data of the engine rotational speed and removes the harmonic component, and outputs the obtained time-series data of the engine rotational speed to the extreme value time calculation unit 122 b.

The extreme value time calculation unit 122b obtains the crank angle time at which the rotational speed becomes the maximum value or the minimum value from the time-series data of the engine rotational speed input from the rotational speed calculation unit 122a, and outputs the result to the combustion phase calculation unit 122 c.

The combustion phase calculation unit 122c obtains the combustion phase based on the maximum value time or the minimum value time of the engine rotational speed obtained by the extremum time calculation unit 122b, and outputs the result to the engine control unit 122 d.

The internal combustion engine control unit 122d controls the engine 1 based on the combustion phase obtained by the combustion phase calculation unit 122 c.

The storage unit 123 is a volatile Memory such as a RAM (Random Access Memory) or a nonvolatile Memory such as a ROM (Read Only Memory). The storage unit 123 stores a control program to be executed by the control unit 122 (arithmetic processing unit) included in the controller 12. The control unit 122 reads out the control program from the storage unit 123 and executes the control program, thereby realizing the functions of the respective blocks of the control unit 122. The controller 12 may have a nonvolatile auxiliary storage device such as a semiconductor memory, and the control program may be stored in the auxiliary storage device.

The present invention is preferably applied to engine control of a hybrid vehicle in which the engine is a type dedicated to power generation. However, it is needless to say that the present invention can also be applied to a hybrid vehicle in which the engine is not exclusively used for power generation. The present invention can also be applied to a non-hybrid vehicle that uses only an engine as a drive source of the vehicle.

[ rotation speed calculation section ]

Fig. 5 shows an example of the flow of the processing performed by the rotational speed calculation unit 122 a. The rotation speed calculation unit 122a obtains time-series data of the cyclically averaged engine rotation speed from the engine rotation speed data detected by the crank angle sensor 11 (S1). This is to prevent the estimation result of the combustion state from being adversely affected when the engine rotation speed varies in each cycle.

A specific method of obtaining time-series data of the cycle-averaged engine rotational speed will be described with reference to fig. 6. The rotational speed calculation unit 122a takes in the rotational speed data obtained by the crank angle sensor 11 at regular crank angles Δ θ as time-series data of the engine 1 cycle amount (during the period of 720 ° crank angle). For example, when Δ θ is 10 °, time-series data of the rotational speed composed of the total 72 points of the crank angles 10 ° to 720 ° is taken in by the rotational speed calculation unit 122 a. The left side of fig. 6 shows an example of the time-series data of the rotation speed for each cycle thus captured.

The acquisition of the rotational speed data for each cycle is repeated for a predetermined number of cycles N (for example, 100 cycles), and the time-series data of the engine rotational speed averaged over the cycles is obtained from equation (1). The time-series data of the engine rotational speed from which the cycle variation is removed is obtained by averaging the engine rotational speed data at each discrete point by the predetermined cycle number N.

[ formula 1]

ω: rotational speed

θ: crank angle

N: number of cycles averaged

i: number of cycles

Returning to fig. 5, the flow of the process of the rotational speed calculation unit 122a will be described. Next, the rotational speed calculation unit 122a obtains time-series data of the engine rotational speed obtained by removing the harmonic component from the time-series data of the cyclically averaged engine rotational speed (S2).

This processing is performed to remove a fluctuation component unrelated to combustion from the engine rotational speed. The fluctuation component of the rotation speed unrelated to the combustion includes, for example, a rotation fluctuation due to mechanical looseness of the speed-increasing machine 2 provided between the engine 1 and the generator 3, an electrical noise included in the signal of the crank angle sensor 11, and the like. These are usually fluctuations having a shorter cycle than the engine rotational fluctuations caused by the combustion torque, and can therefore be removed by removing harmonic components from the rotational speed data. By removing the fluctuation component irrelevant to combustion from the rotational speed data, the estimation accuracy can be improved in the estimation of the combustion state based on the engine rotational fluctuation.

In order to remove the harmonic component from the rotational speed data, the rotational speed calculation unit 122a reconstructs time-series data of the engine rotational speed using the fourier series expansion represented by equation (2). In the fourier series expansion, the original function is reconstructed by adding sinusoidal functions having different frequencies. In equation (2), k is the number of stages of the sine function, and a higher k is a sine function having a higher frequency. Therefore, when reconstructing time-series data of the engine rotational speed using fourier series expansion, if the addition of the sine function is terminated by an appropriate number of stages, frequency components higher than the number of stages can be removed from the original data.

[ formula 2]

Original cyclic average rotational speed

Reconstructed cyclic average rotational speed

k: number of times of sine function

θ: crank angle

Θ: during the cycle

In a general 4-cylinder 4-stroke gasoline engine, the number of truncations (the number of stages) n of the sine function for removing the higher harmonic components not related to combustion from the rotational speed data is preferably about 3 to 5. However, the number of times n of cutoff is considered to be appropriate and varies depending on the structure and operating conditions of the engine. For example, if the number of engine cylinders is increased, the frequency of engine rotation fluctuation due to combustion torque becomes high, so the number of times of truncation can be increased in order to appropriately reconstruct the fluctuation component. Further, when the engine rotation speed is increased, the frequency of the engine rotation fluctuation due to the combustion torque is also increased, so that the number of times of cutoff can be increased. Therefore, if the number of times n of truncation of the sine function is changed based on the engine rotational speed, the estimation accuracy can be improved in a wide operating range in the estimation of the combustion state based on the engine rotational fluctuation.

As described above, the rotational speed calculation unit 122a calculates the crank rotational speed by performing fourier series expansion of the time-series value of the crank rotational speed obtained by the rotational angle sensor a finite number of times (number of stages). Further, it is preferable that the number of times of truncation of the fourier series expansion is changed based on the crank rotation speed.

The extreme value time calculation unit 122b divides the period of the crank rotation speed time-series value in the period of the crank angle of 720 ° by the number of cylinders, and assigns the crank rotation speed time-series value in the period including the compression top dead center of each cylinder as the crank rotation speed time-series value in the cylinder. The extreme value timing calculation unit 122b preferably calculates the extreme value timing of the crank rotation speed for each cylinder from the crank rotation speed time-series value assigned to each cylinder. Preferably, the extreme value time calculation unit 122b approximates the time-series value of the crank rotation speed by using a continuous function based on the discrete time-series value of the crank rotation speed, and calculates the extreme value time of the crank rotation speed by using the continuous function.

[ extreme value time calculation Unit ]

Next, the processing of the extremum time calculating unit 122b in the controller 12 will be described.

Fig. 7 shows an example of the flow of the processing of the extremum time calculating unit 122 b.

In the extreme value timing calculation unit 122b, time-series data of the engine rotational speed over the entire engine cycle (crank angle 0 to 720 °) is converted into a local crank angle synchronized with the cycle of each engine cylinder (S3). Next, a crank angle timing at which the engine rotational speed becomes maximum (or minimum) is calculated from the time-series data of the engine rotational speed converted into the local crank angle (S4).

The conversion process of the local crank angle (S3) in the rotational speed calculation unit 122a will be described with reference to fig. 8 to 10.

Fig. 8 shows the sequence of the strokes of a 3-cylinder 4-stroke engine. In a 4-stroke engine, 4 strokes of intake, compression, expansion, and exhaust are performed in this order. In a 3-cylinder engine, the stroke between cylinders is offset by 240 ° from the crank angle each time. If the ignition of the engine is performed in the order of the 2 nd cylinder, the 1 st cylinder, and the 3 rd cylinder, the stroke of the 1 st cylinder is delayed by 240 ° with respect to the 2 nd cylinder, and further the stroke of the 3 rd cylinder is delayed by 240 ° with respect to the 1 st cylinder.

The combustion state is strongly reflected in the vicinity of the compression top dead center of each cylinder in which the in-cylinder pressure becomes maximum. Therefore, in step S3, the rotational speed data of the entire cycle (crank angle 0 to 720 °) is divided into 240 ° crank angle intervals around the compression top dead center of each cylinder. Then, each window is assigned as the rotational speed data of the cylinder containing the compression top dead center within the window.

Fig. 9 is an example in which a window having a width of 240 ° around the compression top dead center of each cylinder is set for time-series data of the engine rotational speed. The compression top dead center of the 3 rd cylinder is included in the interval of 0-240 DEG of the crank angle, so the compression top dead center is distributed as the 3 rd cylinder window. Similarly, the section of the crank angle of 240-480 DEG is allocated as the 2 nd cylinder window, and the section of the crank angle of 480-720 DEG is allocated as the 1 st cylinder window.

If the windows are thus allocated, the combustion state of the 3 rd cylinder is reflected more strongly in the rotational speed data of the 3 rd cylinder window than in the rotational speed data of the other cylinder windows.

Similarly, the combustion state of the 2 nd cylinder is reflected more strongly in the rotation speed data of the 2 nd window than in the rotation speed data of the other windows, and the combustion state of the 1 st cylinder is reflected more strongly in the rotation speed data of the 1 st window than in the rotation speed data of the other windows. Therefore, by using the rotational speed data of each window, the combustion state can be estimated for each cylinder.

Then, in step S3, the rotational speed data of each window is converted into a local crank angle based on the compression top dead center of each cylinder. Fig. 10 shows an example in which the rotational speed data of each window is converted into a local crank angle. In this example, the time-series data of the rotational speed was newly defined using a local crank angle of-120 ° to 120 ° in which the compression top dead center of each cylinder was set to zero. In step S3, time-series data converted into the rotational speed of the local crank angle is generated for all the cylinder windows, and the data is passed to step S4.

Next, in step S4, the time when the rotational speed becomes maximum or the time when the rotational speed becomes minimum is calculated from the time-series data of the rotational speed converted into the local crank angle.

Fig. 11 shows a method of calculating the maximum time of the rotational speed in step S4.

Since the time-series data of the rotational speed is discrete point data, the maximum timing of the rotational speed in the discrete point data deviates from the maximum timing of the actual rotational speed (rotational speed indicated by a broken line in fig. 11). Therefore, in step S4, the rotation speed is approximated by the polynomial for discrete point data, and the maximum time of the rotation speed is obtained from the approximate expression.

Therefore, in the process S4, the data point n where the rotation speed is the largest is first searched for from the time-series data of the rotation speed as discrete point data. Then, a local crank angle θ at n is extracted_nAnd a rotation speed omega_nN local crank angle theta at data point before time 1_n-1And a rotation speed omega_n-1N, local crank angle θ at data point after time 1_n+1And a rotation speed omega_n+1。

Further, in step S4, the rotation speed ω is approximated by equation 3 as a quadratic function of the local crank angle θ. Here, a, b, c are constants. In the processing S4, θ is substituted into equation 3 by solving_n、ω_n、θ_n-1、ω_n-1、θ_n+1、ω_n+1The three simultaneous equations thus obtained are used to obtain a, b and c.

[ formula 3]

ω＝aθ²+bθ+c

Since the differential value of equation 3 becomes zero at the point where the rotational speed becomes the extreme value, the local crank angle θ (maximum speed time) at which the rotational speed becomes maximum is obtained from equation 4 in step S4_max. Theta of each cylinder is obtained by the same flow_maxAnd passes them to the combustion phase calculation unit 122 c.

[ formula 4]

In addition, when the minimum time of the rotational speed is obtained in step S4, the minimum time is also obtained by the same method as the method for obtaining the maximum time of the rotational speed.

Fig. 12 shows a method of calculating the minimum time of the rotational speed in step S4.

In the process S4, first, a data point n with the smallest rotational speed is searched for from time-series data of rotational speeds as discrete point data. Then, a local crank angle θ at n is extracted_nAnd a rotation speed omega_nN local crank angle theta at data point before time 1_n-1And a rotation speed omega_n-1N, local crank angle θ at data point after time 1_n+1And a rotation speed omega_n+1. Then, in step S4, using these values, constants a, b, and c of the quadratic function are obtained from equation 3, and further, local crank angle (minimum speed time) θ at which the rotation speed is minimum is obtained from equation 4_min. Theta of each cylinder is obtained by the same flow_minAnd passes them to the combustion phase calculation unit 122 c.

Further, in the above-described embodiment, the rotational speed ω is approximated with the quadratic function of the local crank angle θ, but the present invention is not limited thereto. The rotation speed ω can be approximated using various continuous functions such as a cubic function and a sinusoidal function of the local crank angle θ, for example.

[ Combustion phase calculation section ]

Next, a method of calculating the combustion phase by the combustion phase calculation unit 122c in the controller 12 will be described with reference to fig. 13.

FIG. 13 shows the maximum time θ of the engine rotational speed_maxCorrelation with combustion center of gravity position MFB50And (4) figure of nature. Here, the Mass combustion ratio (MFB: Mass Fraction Burned) is a ratio of the Mass of a Burned portion to the Mass of the entire air-fuel mixture, and the combustion center of gravity position MFB50 represents a crank angle at which the combustion Mass ratio becomes 50%. Maximum time θ of engine rotational speed_maxThere is a strong correlation with the combustion center of gravity position MFB50, and the relationship is substantially linear as shown in fig. 13. The reason for this will be explained below.

The temporal change in the engine rotational speed is represented by the equation of motion of the rotating body shown in equation 5. Wherein, T_cIs the combustion torque, T_LIs the load torque. From equation 5, the rotational acceleration d ω/dt and the combustion torque T_cIn a proportional relationship, when the combustion torque changes, the rotational acceleration changes. For example, if the combustion center of gravity position is retarded, the timing of combustion torque generation is retarded, and in synchronization with this, the timing at which the rotational acceleration becomes maximum is retarded. Therefore, a strong correlation occurs between the maximum timing of the rotational acceleration and the combustion center of gravity position.

[ formula 5]

ω: rotational speed

T_c: combustion torque

T_L: load torque

I: moment of inertia

t: time of day

On the other hand, at the load torque T_LWhen the change in combustion torque is small, the time change in combustion torque is substantially sinusoidal. This is because the arm length of the crank, which determines the magnitude of the combustion torque, changes in a sinusoidal manner as the crankshaft rotates. When the rotational acceleration is sinusoidal, the rotational speed obtained by integrating the rotational acceleration is also sinusoidal, and the time variation waveform of the rotational acceleration and the time variation waveform of the rotational speed are kept at a constant phase difference. Therefore, the phase of the maximum time of the rotational acceleration and the maximum time of the rotational speedThe head difference is also constant, and the combustion center of gravity position has a strong correlation not only with the maximum timing of the rotational acceleration but also with the maximum timing of the rotational speed. That is, in the present embodiment, it is preferable that the waveform indicating the crank angle of the crank rotation speed on the vertical axis with respect to the horizontal axis is a sine wave.

Maximum time θ of engine rotational speed_maxThe correlation line with the combustion center of gravity position MFB50 is obtained in advance by calibration or the like, and is stored in the ROM of the controller 12 in the form of a correlation equation or a reference table. The combustion phase calculation unit 122c uses the maximum time θ of the engine rotational speed shown in fig. 13_maxThe maximum time θ of the current engine rotational speed transmitted from the extremum time calculation unit 122b is the line related to the combustion center of gravity position MFB50_{max_current}Determining a current combustion center of gravity position MFB50_current. The current combustion center of gravity position MFB50 is determined for each cylinder in the same flow_currentAnd passes them to the engine control unit 122d of the controller 12.

In addition, even if the minimum time θ of the engine rotational speed is used_minOr the maximum time θ of the engine rotational speed_maxThe combustion center of gravity position is determined in the same manner as in the case of (1).

FIG. 14 shows the minimum time θ of the engine rotational speed_minA graph of the correlation with the combustion center of gravity position MFB 50. Minimum time θ of engine rotational speed_minThere is a strong correlation with the combustion center of gravity position MFB50, and the relationship is substantially linear as shown in fig. 14. The reason for this will be explained below.

As described above, at the load torque T_LWhen the change of (3) is small, the temporal change of the engine rotational speed becomes sinusoidal. Therefore, the maximum timing of the rotational speed and the minimum timing of the rotational speed are substantially constant phase differences. Therefore, the combustion center of gravity position has a strong correlation not only with the maximum timing of the rotational speed but also with the minimum timing of the rotational speed.

Minimum time θ of engine rotational speed_minAnd burningThe correlation line of the combustion center of gravity position MFB50 is obtained in advance by calibration or the like, and is stored in the ROM of the controller 12 in the form of a correlation equation or a reference table. The combustion phase calculation unit 122c uses the minimum time θ of the engine rotational speed shown in fig. 14_minThe line relating to the combustion center of gravity position MFB50 is derived from the minimum time θ of the current engine rotational speed transmitted from the extremum time calculation unit 122b_minCurrent determines the current combustion center of gravity position MFB50_current. The current combustion center of gravity position MFB50 is determined for each cylinder in the same flow_currentAnd passes them to the engine control unit 122d of the controller 12.

In addition, the maximum time θ of the engine rotational speed may be used_maxTo find an initial combustion position MFB10 (mass combustion ratio 10% position).

FIG. 15 shows the maximum time θ of the engine rotational speed_maxA map of the correlation with the initial combustion position MFB 10. Maximum time θ of engine rotational speed_maxThere is a strong correlation with the initial combustion position MFB10, and as shown in fig. 15, the relationship is approximately linear. This is because, when the initial combustion position changes, the generation timing of the combustion torque changes accordingly. Therefore, if the maximum time θ of the engine rotational speed is obtained by calibration or the like in advance_maxThe correlation line with the initial combustion position MFB10 can be determined according to the maximum time θ of the current engine rotational speed_{max_current}Using the maximum time θ of the engine rotational speed shown in fig. 15_maxThe current initial combustion position MFB10 is obtained from the correlation line between the initial combustion position MFB10 and the current initial combustion position MFB10_current. In addition, by using MFB10_currentMinus the current ignition moment theta_{ig_current}The current initial combustion period Δ θ can also be obtained_{ig10_current}。

The combustion phase calculation unit 122c determines the current combustion center of gravity position MFB10 for each cylinder in the same flow_currentDuring initial combustion, delta theta_{ig10_current}And passes them to the engine control unit 122d of the controller 12.

In addition, can makeBy the minimum time theta of engine speed_minTo obtain an initial combustion position MFB 10.

FIG. 16 shows the minimum time θ of the engine rotational speed_minA map of the correlation with the initial combustion position MFB 10. Minimum time θ of engine rotational speed_minThere is a strong correlation with the initial combustion position MFB10, and the relationship is approximately linear as shown in fig. 16. Therefore, if the minimum time θ of the engine rotational speed is obtained by calibration or the like in advance_minThe correlation line with the initial combustion position MFB10 can be based on the minimum time θ of the current engine rotational speed_minCurrent, using the minimum time θ of the engine rotational speed shown in fig. 16_minThe current initial combustion position MFB10 is obtained from the correlation line between the initial combustion position MFB10 and the current initial combustion position MFB10_current. In addition, by using MFB10_currentMinus the current ignition moment theta_{ig_current}The current initial combustion period Δ θ can also be obtained_{ig10_current}。

The combustion phase calculation unit 122c determines the current combustion center of gravity position MFB10 for each cylinder in the same flow_currentDuring initial combustion, delta theta_{ig10_current}And passes them to the engine control unit 122d of the controller 12. As described above, the internal combustion engine control device (ECU12) of the present embodiment includes: a rotational speed calculation unit 122a that calculates the crank rotational speed of the internal combustion engine (engine 1); an extreme value time calculation unit 122b that calculates an extreme value time of the crank rotation speed calculated by the rotation speed calculation unit 122 a; and a combustion state estimating unit (combustion phase calculating unit 122c) that estimates the combustion state based on the extreme value timing of the crank speed calculated by the extreme value timing calculating unit 122 b.

[ control section of internal Combustion Engine ]

Next, the control of the engine by the internal combustion engine control unit 122d will be described.

In order to improve the thermal efficiency of the engine, it is necessary to appropriately control the combustion phase. If the combustion phase is too early, the work of compressing the gas in the compression stroke increases, so the losses increase. Further, if the combustion phase is too slow, the exhaust gas temperature rises and the heat loss due to the exhaust gas increases. Since the combustion phase at which the thermal efficiency becomes maximum is defined by the combustion center of gravity position MFB50, the thermal efficiency of the engine can be improved by controlling the ignition timing so that the combustion center of gravity position MFB50 becomes a predetermined value. Therefore, the engine control based on the combustion center of gravity position MFB50 is performed in the internal combustion engine control unit 122 d.

Fig. 17 is a control block diagram of the ignition timing in the controller 12. In the control of the ignition timing in the controller 12, the current MFB50 calculated by the combustion phase calculation unit 122c is used as the basis_{_current}The engine control unit 122d calculates the ignition timing of the deviation from the target MFB50, and transmits an ignition signal to the engine 1 at the calculated ignition timing.

The engine control unit 122d is constituted by a PID controller, and adjusts the ignition timing so that MFB50 may be controlled_{_current}The deviation from the target MFB50 becomes small. More specifically, at MFB50_{_current}When retarded from the target MFB50, the ignition timing is advanced to advance the combustion phase. In addition, in MFB50_{_current}When advanced from the target MFB50, the ignition timing is retarded to retard the combustion phase.

The internal combustion engine control device (ECU12) of the present embodiment includes an internal combustion engine control unit 122d that performs combustion control of the internal combustion engine (engine 1) based on the combustion state estimated by the combustion state estimation unit (combustion phase calculation unit 122 c). Further, the internal combustion engine (engine 1) is preferably configured to drive the generator 3 of the series hybrid system.

Further, the combustion state estimating unit (combustion phase calculating unit 122c) of the internal combustion engine control device (ECU12) estimates the combustion phase at which the combustion mass ratio of the internal combustion engine (engine 1) becomes the set value based on the timing at which the crank rotation speed becomes maximum or minimum, and the internal combustion engine control unit 122d performs combustion control of the internal combustion engine (engine 1) so that the estimated combustion phase becomes the set phase. The engine control unit 122d controls the ignition timing of the internal combustion engine (engine 1) so that the estimated combustion phase becomes the set phase. Specifically, the combustion state estimating unit (combustion phase calculating unit 122c) calculates a combustion phase (combustion center position MFB50) at which the combustion mass ratio is 50% and a combustion phase (initial combustion position MFB10) at which the combustion mass ratio is 10%. Further, the engine control unit 122d preferably controls the ignition timing so that the estimated combustion phase (combustion center of gravity position MFB50) is, for example, 8 ° to 15 ° after top dead center. Further, the engine control unit 122d preferably controls the ignition timing so that the estimated combustion phase (initial combustion position MFB10) is within 15 ° after ignition, for example.

That is, the internal combustion engine control unit 122d controls the EGR valve opening degree of the internal combustion engine (engine 1) so that the estimated combustion phase (initial combustion position MFB10) becomes the set phase (for example, within 15 ° after ignition). When the estimated combustion phase (initial combustion position MFB10) is retarded from the set phase (for example, within 15 ° after ignition), the engine control unit 122d controls the EGR valve opening degree of the internal combustion engine (engine 1) in the closing direction.

When the estimated combustion phase (combustion center of gravity position MFB50, initial combustion position MFB10) is retarded from the above-described set phase, the internal combustion engine control unit 122d performs control so that the ignition timing of the internal combustion engine (engine 1) is advanced. In contrast, when the estimated combustion phase (combustion center of gravity position MFB50, initial combustion position MFB10) is advanced from the set phase described above, engine control unit 122d performs control so that the ignition timing of the internal combustion engine (engine 1) is retarded.

Further, the combustion phase calculation unit 122c obtains the current combustion center of gravity position MFB50 for each cylinder_{_current}Therefore, MFB 50-based implementation is preferably implemented for each cylinder_{_current}The ignition timing of (1). In a multi-cylinder engine, combustion phases may differ among cylinders due to variations in intake air amount and the like. However, by MFB50 on a per cylinder basis_{_current}To control the ignition timing of each cylinder, the combustion phase of each cylinder can be optimized, and the thermal efficiency and emission performance can be improved. Further, MFB50 for each cylinder may be used_{_current}Cylinder averaged MFB50_{_current}And controls the ignition timing based thereon. In this case, the ignition timing is the same for all cylinders, as forThe thermal efficiency and the emission performance may be reduced as compared with the case where the ignition timing is controlled per cylinder, but there is an advantage that the control is simplified.

Next, another engine control performed by the internal combustion engine control unit 122d will be described.

In order to improve the thermal efficiency of an engine, Exhaust Gas Recirculation (EGR) control is widely performed in which exhaust gas is mixed with intake air of the engine. If EGR is introduced, the amount of gas sucked into the cylinder increases, and therefore pumping loss at part load can be reduced. In addition, since the combustion temperature is lowered by the inert gas, the cooling loss can be reduced. In addition, EGR is also effective in suppressing knocking at high load. Generally, the larger the proportion of EGR in the intake gas (EGR rate), the higher the effect of EGR. On the other hand, if the EGR rate becomes large, the combustion becomes unstable, and concerns about misfire, increase in emissions, and the like become high.

FIG. 18 shows the initial combustion period Δ θ_ig10An example of the relationship with the cyclic variation rate of the combustion torque. During initial combustion Δ θ_ig10Indicating the ease of ignition of the mixture, Δ θ_ig10Large means low ignitability to the mixture. Therefore, if Δ θ_ig10When the engine speed becomes large, misfire is likely to occur, and the cyclic variation of the combustion torque increases. Especially when Δ θ_ig10When the engine speed becomes larger than the predetermined value, the misfire cycle increases rapidly, and the increase in torque variation accelerates.

Thus, the instability of combustion caused by EGR is caused by the initial combustion period Δ θ_ig10So that the EGR rate is controlled so that the initial combustion period Delta theta_ig10The engine has a predetermined value, and can improve the thermal efficiency of the engine while preventing misfire and deterioration of emission. Therefore, the initial combustion period Δ θ is implemented in the internal combustion engine control unit 122d_ig10The engine control of (1).

The combustion state estimation unit of the control unit 122 estimates the initial combustion period Δ θ of the internal combustion engine (engine 1) based on the timing at which the crank rotation speed is at the maximum or minimum_ig10The engine control unit 122d performs combustion control of the internal combustion engine (engine 1) such that the estimated value is calculatedDuring initial combustion of_ig10The initial combustion period is set. Specifically, the engine control unit 122d calculates the initial combustion period Δ θ_ig10When the period is longer than the set initial combustion period, the opening degree of an EGR valve of an internal combustion engine (engine 1) is controlled in the closing direction. In addition, during the estimated initial combustion period Δ θ_ig10If the period is shorter than the set initial combustion period, the engine control unit 122d controls the EGR valve opening degree of the internal combustion engine (engine 1) in the closing direction.

Fig. 19 is a control block diagram of EGR in controller 12. In the control of EGR in the controller 12, the current initial combustion period Δ θ calculated by the combustion phase calculation unit 122c is based on_{ig10_current}With a target delta theta_ig10The engine control unit 122d calculates the EGR valve opening degree, and operates the engine 1 at the calculated EGR valve opening degree. Here, the initial combustion period Δ θ_{ig10_current}From the initial combustion period Delta theta of each cylinder_{ig10_current}Select the largest Δ θ_{ig10_current}Based on this, EGR control is performed. Here, the largest Δ θ is selected_{ig10_current}This is because, as described above, the combustion stability is relative to the initial combustion period Δ θ_ig10The increase in (2) tends to be rapidly worsened, and Δ θ is preferentially performed_{ig10_current}The maximum cylinder stability is improved. The engine control unit 122d controls the EGR valve opening degree of the internal combustion engine (engine 1) so that the estimated combustion phase becomes the initial combustion period of each cylinder, and the largest initial combustion period among the initial combustion periods of each cylinder becomes the set phase.

The engine control unit 122d is constituted by a PID controller, and adjusts the EGR valve opening degree to Δ θ_{ig10_current}With a target delta theta_ig10The deviation of (2) becomes small. More specifically, at Δ θ_{ig10_current}Target ratio delta theta_ig10In a case where the EGR rate is large, the EGR valve opening degree is decreased to decrease the EGR rate. At Delta theta_{ig10_current}Target ratio delta theta_ig10When the EGR rate is small, the EGR valve opening degree is increased to increase the EGR rate.

Thus, based on the current initial combustion period Δ θ_{ig10_current}To control EGR without compromisingThe EGR rate is maximized under the condition of combustion stability, and the efficiency of the engine can be improved.

In the present invention, the combustion phase is determined based on the maximum timing of the engine rotational speed. Therefore, it is not necessary to perform differentiation processing for obtaining the engine rotational acceleration as in the conventional technique, and there is an advantage that it is less susceptible to disturbance such as noise. In addition, since the differential processing is not required, the configuration of the controller becomes simpler, and there is an advantage that the number of software manufacturing steps and the circuit cost are reduced.

The present invention is not limited to the above embodiments, and various other application examples and modifications can be made without departing from the spirit of the present invention described in the claims.

For example, in the above-described embodiment, the application example of the present invention to a series hybrid vehicle is shown, but the present invention is not limited to this. For example, the present invention can be applied to a parallel hybrid vehicle and an engine-dedicated vehicle.

A part or all of the configuration, function, processing unit, and the like of the controller 12 may be realized by hardware by, for example, designing an integrated circuit.

Description of the reference numerals

1 … engine, 3 … induction generator, 5 … battery, 7 … induction motor, 10 … knock sensor, 11 … crank angle sensor, 12 … controller, 17 … spark plug, 20 … throttle valve, 26 … timing rotor (timing rotor), 28 … EGR pipe, 29 … EGR valve, 122 … control section, 121 … input/output section, 122a … rotation speed calculation section, 122b … extreme point time calculation section, 122c … combustion phase calculation section, 122d … internal combustion engine control section, 123 … storage section.