JP2006112373A - Torque estimation method and apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque estimation method for an internal combustion engine capable of improving estimation accuracy as compared with the conventional one.
SOLUTION: A first crank angular velocity ω _a ′ is detected within a first crank angle range set between the end of a compression stroke and the beginning of an explosion stroke, and a predetermined crank angle is determined from the first crank angle range. detecting a second crank angular speed omega _{b 'in} the second crank angle range set in the explosion stroke across the estimated torque T _e generated in the cylinder on the basis of the first and second crank angular speed In the torque estimation method for the internal combustion engine, the amount of change in the crank angular speed that represents the influence of the reciprocating inertia force according to the load of the internal combustion engine that occurs in the second crank angle range is expressed as the correction amount ω of the second crank angular speed. _Obtained as _M , the detected value ω _b ′ of the second crank angular velocity is corrected by the correction amount ω _M. Estimating the torque by using the corrected second crank angular speed omega _b.
[Selection] Figure 9

Description

  The present invention relates to a method and apparatus for estimating a torque generated in a cylinder of an internal combustion engine.

As a method for estimating the torque generated by the cylinder of the internal combustion engine, a first crank angular velocity is detected in a first crank angle range between the end of the compression stroke and the early stage of the explosion stroke, and the second crank angle range in the middle of the explosion stroke. In addition, a method is known in which a second crank angular velocity is detected, a change amount of angular velocity energy for each cylinder is detected using these angular velocities, and a torque is estimated from the change amount of the angular velocity energy (Patent Document 1). reference). Considering that the crank angular speed changes due to the reciprocating inertia force generated by the reciprocating motion of the inertial mass such as the piston, the amount of change in the crank angular speed during the fuel supply stop accompanying the deceleration operation of the internal combustion engine is An estimation method has also been proposed in which a detection value of a crank angular velocity is corrected based on the detected value and a torque estimation error due to the influence of a reciprocating inertia force is suppressed (see Patent Document 2). In addition, Patent Documents 3 and 4 exist as prior art documents related to the present invention.
JP-A-9-273444 JP-A-9-280100 JP 2004-92603 A JP 2001-227398 A

  In the estimation method of Patent Document 2 described above, taking into account that the amount of change in the crank angular speed due to the influence of the reciprocating inertia force changes in accordance with the rotational speed of the internal combustion engine (hereinafter sometimes referred to as engine rotational speed). The correspondence between the engine speed and the change amount of the crank angular speed is learned. When correcting the detected value of the crank angular speed, a correction amount of the crank angular speed corresponding to the engine speed is obtained. However, the reciprocating inertia force is also affected by the load of the internal combustion engine. Therefore, in the estimation method of Patent Document 2, if the rotational speed is constant, the correction amount of the crank angular speed is constant regardless of the load. Therefore, the torque estimation error increases as the load increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a torque estimation method and apparatus for an internal combustion engine that can improve estimation accuracy as compared with the prior art.

  The torque estimation method for an internal combustion engine according to the present invention detects a first crank angular velocity within a first crank angle range set between the end of the compression stroke and the initial stage of the explosion stroke, and the first crank angle range. A second crank angular velocity is detected in a second crank angle range set during an explosion stroke separated from a predetermined crank angle from the first crank angular velocity, and a torque generated in the cylinder based on the first and second crank angular velocities is detected. A method of estimating torque of an internal combustion engine for estimation, wherein a change amount of a crank angular speed representing an influence of a reciprocating inertia force according to a load of the internal combustion engine generated in the second crank angle range is expressed as the second crank angular speed. A correction amount of the second crank angular velocity, a step of correcting the detected value of the second crank angular velocity based on the calculated correction amount of the second crank angular velocity, and a corrected second crank angular velocity. A step of estimating the torque and use, by providing, for solving the above problems (claim 1).

  The torque estimation device for an internal combustion engine according to the present invention includes a crank angle signal output means for outputting a signal corresponding to a crank angle, and from the end of the compression stroke to the initial stage of the explosion stroke based on the output signal of the crank angle signal output means. The second crank angle range set during the explosion stroke in which the first crank angular velocity is set within a first crank angle range set between the first crank angle range and a predetermined crank angle is separated from the first crank angle range. The torque estimation of the internal combustion engine comprising: crank angular speed detecting means for detecting the second crank angular speed at each of the above; and torque estimating means for estimating the torque generated in the cylinder based on the first and second crank angular speeds. An amount of change in crank angular velocity representing an influence of a reciprocating inertia force according to a load of the internal combustion engine generated in the second crank angle range. A correction amount obtaining unit for obtaining a correction amount for the rank angular velocity; and an angular velocity correcting unit for correcting the detected value of the second crank angular velocity based on the obtained second crank angular velocity correction amount. The above-described problem is solved by estimating the torque by using the corrected second crank angular velocity (claim 7).

  According to the torque estimation method and the torque estimation device of the present invention, the change amount of the crank angular speed representing the influence of the reciprocating inertia force is obtained according to the load of the internal combustion engine, and the second crank angular speed is corrected by the obtained value. Yes. Therefore, the fluctuation of the reciprocating inertia force accompanying the change in the load of the internal combustion engine can be reflected in the torque estimation, thereby improving the torque estimation accuracy. In particular, in the second crank angle range during the explosion stroke, the detection value of the crank angular speed is lower than the crank angular speed commensurate with the torque generated originally due to the deceleration action due to the reciprocating inertia force, and the first crank angle range is reached. In some cases, the difference between the detected first crank angular velocity and the first crank angular velocity may not be sufficient, or the magnitude relationship may be reversed to make torque estimation difficult. According to the torque estimation method of the present invention, the second crank angular velocity is increased to the original crank angular velocity excluding the amount of deceleration due to the reciprocating inertia force, whereby torque estimation can be performed correctly.

  In one aspect of the torque estimation method of the present invention, a map that associates the rotational speed and load of the internal combustion engine with the correction amount of the second crank angular speed is created in advance and provided in the control device for the internal combustion engine. In the step of storing the map in the storage device and obtaining the correction amount of the second crank angular speed, the second crank angular speed corresponding to the rotational speed and load of the internal combustion engine based on the map stored in the storage device. A correction amount may be acquired (claim 2). According to this aspect, if the relationship between the rotational speed and load of the internal combustion engine and the correction amount of the second crank angular speed is implemented for a representative internal combustion engine and a map is created, The map can be used to obtain the correction amount of the crank angular speed corresponding to the rotational speed and load of the internal combustion engine. As a result, the amount of calculation required for correcting the second crank angular velocity is simplified, and the torque can be estimated quickly.

  In one aspect of the torque estimation method of the present invention, the method further includes the step of acquiring the combustion pressure of one or more cylinders, and the step of obtaining the correction amount of the second crank angular velocity uses the acquired combustion pressure. A correction amount for the second crank angular velocity may be calculated. According to this aspect, since the second crank angular speed correction amount is acquired by acquiring the combustion pressure of the cylinder of the internal combustion engine, the load of the internal combustion engine is more accurately reflected on the second crank angular speed correction amount. Thus, the torque estimation accuracy can be further improved.

  In one aspect of the torque estimation method of the present invention, the change amount of the crank angular speed representing the influence of the reciprocating inertia force according to the load of the internal combustion engine generated in the first crank angle range is determined as the first crank angular speed. Using the corrected first crank angular speed, the corrected first crank angular speed detection value based on the calculated first crank angular speed correction value, and the corrected first and second crank angular speeds, respectively. And a step of estimating the torque. According to this aspect, the first crank angular velocity can also be corrected in consideration of the effect of the reciprocating inertia force, and the correction amount takes into account the load of the internal combustion engine. Can be improved.

  In one aspect of the torque estimation method of the present invention, a map that associates the rotational speed and load of the internal combustion engine with the correction amount of the first crank angular speed is created in advance and provided in the control device for the internal combustion engine. In the step of storing the map in the storage device and obtaining the correction amount of the first crank angular speed, the first crank angular speed corresponding to the rotational speed and load of the internal combustion engine based on the map stored in the storage device The correction amount may be acquired (claim 5). Alternatively, the method further includes the step of acquiring the combustion pressure of one or more cylinders, and in the step of obtaining the correction amount of the first crank angular velocity, the correction amount of the first crank angular velocity is obtained using the acquired combustion pressure. It may be calculated (claim 6). The advantages of these modes are the same as those of the mode related to the second crank angular velocity correction amount described above.

  The torque estimation apparatus according to the aspect of the invention may further include a storage device that stores a map in which the rotation speed and load of the internal combustion engine are associated with the correction amount of the second crank angular velocity, and the correction amount acquisition is performed. The means may obtain the correction amount of the second crank angular speed corresponding to the rotational speed and load of the internal combustion engine based on the map stored in the storage device.

  In one aspect of the torque estimation apparatus of the present invention, the torque estimation device further includes combustion pressure acquisition means for acquiring the combustion pressure of one or more cylinders, and the correction amount acquisition means uses the acquired combustion pressure to perform the second operation. A crank angular speed correction amount may be calculated (claim 9).

  In one aspect of the torque estimation apparatus of the present invention, the correction amount acquisition means responds to a load of the internal combustion engine generated in the first crank angle range in addition to the correction amount of the second crank angular speed. A change amount of the crank angular speed representing the influence of the reciprocating inertia force is further obtained as a correction amount of the first crank angular speed, and the angular speed correction means is provided in addition to the correction of the second crank angular speed. The detected value of the first crank angular speed may be corrected based on the correction amount of the crank angular speed, and the torque estimating means may estimate the torque by using the corrected first and second crank angular speeds, respectively ( Claim 10).

  In the aspect of obtaining the correction amount of the first crank angular speed, the storage device further stores a map in which the rotational speed and load of the internal combustion engine and the correction amount of the first crank angular speed are associated with each other, and the correction amount The acquiring means may acquire a first crank angular speed correction amount corresponding to the rotational speed and load of the internal combustion engine based on the map stored in the storage device.

  In the aspect which calculates | requires the correction amount of the said 1st crank angular velocity, it further comprises the combustion pressure acquisition means which acquires the combustion pressure of one or more cylinders, The said correction amount acquisition means uses the acquired combustion pressure, The correction amount of the first crank angular velocity may be calculated (claim 12).

  Also in each of the above aspects relating to the torque estimation device, the same advantages as in the aspect relating to the torque estimation method described above can be achieved.

  In the present invention, the detection of the crank angular velocity is not limited to the determination of the crankshaft rotation angle per unit time, but includes a case where a physical quantity equivalent to this is detected. For example, when the time required for the crankshaft to rotate at a certain crank angle is detected, and the calculation processing of the present invention is performed with the detected value of the time being representative of the crank angular velocity, the concept of detecting the crank angular velocity is also included. included.

  As described above, according to the present invention, the correction amount according to the load of the internal combustion engine is used when correcting the detected value of the crank angular speed in consideration of the influence of the reciprocating inertia force. It is reflected in the torque estimation, thereby improving the torque estimation accuracy.

[First embodiment]
FIG. 1 shows a first embodiment in which the torque estimation device of the present invention is applied to an internal combustion engine. In this embodiment, a so-called in-line four-cylinder reciprocating internal combustion engine (hereinafter sometimes referred to as an engine) 1 in which four cylinders 1a to 1d from # 1 cylinder 1a to # 4 cylinder 1d are arranged in a line. Torque is estimated based on the amount of change in the angular velocity of the crankshaft 2 (hereinafter referred to as crank angular velocity). The engine 1 is used, for example, as a driving source for driving an automobile.

  The engine 1 is provided with a crank angle detection device 3 for detecting the rotational position (crank angle) of the crankshaft 2. The crank angle detection device 3 includes a rotor 4 that rotates integrally with the crankshaft 2, and a crank angle sensor 5 as a crank angle signal output means that is disposed so as to face the outer periphery of the rotor 4. Convex portions (not shown) are provided on the outer periphery of the rotor 4 at regular intervals in the circumferential direction, for example, 30 ° intervals, and the crank angle sensor 5 outputs a predetermined detection signal in response to detection of these convex portions. Output. A reference position indicating unit (not shown) such as a notch for determining the rotational position of the crankshaft 2 is provided on the outer periphery of the rotor 4. The crank angle sensor 5 outputs a unique reference detection signal when the reference position indicating unit is detected.

  The output signal of the crank angle sensor 5 is guided to an engine control unit (hereinafter referred to as ECU) 6. The ECU 6 is a computer unit having a microprocessor, and controls the operating state of the engine 1 by operating various fuel injection valves (not shown) by executing various engine control programs stored in the storage device 7. The storage device 7 is configured by a semiconductor memory such as a ROM, SRAM, RAM, or the like. The ECU 6 discriminates the crank angle by counting the number of convex detection signals with reference to the reference detection signal output from the crank angle sensor 5. Further, the ECU 6 determines the crank angular speed (or the rotational speed of the engine 1) by detecting the time interval of the detection signal output from the crank angle sensor 5. Thereby, ECU6 functions as a crank angular velocity detection means.

  The ECU 6 functions as correction amount acquisition means, angular velocity correction means, and torque estimation means in the present invention by executing a program for torque estimation stored in the storage device 7. An accelerator opening sensor 8 is connected to the ECU 6 as a sensor used for torque estimation. In addition, the ECU 6 is connected to various sensors such as an air flow meter that detects the amount of intake air and an A / F sensor that outputs a signal corresponding to the air-fuel ratio in the exhaust gas. .

The storage device 7 stores maps shown in FIGS. 2A and 2B as data used when the ECU 6 functions as a correction amount acquisition unit. These maps associate the engine speed Ne and the load Q with the crank angular speed correction amounts ω _{Ma11... Mn} , ω _{Mb11... Mn} (hereinafter sometimes referred to as the correction amount ω _M ). is there. The correction amount ω _M corresponds to the amount of change in the crank angular velocity that represents the influence of the reciprocating inertia force of the engine 1. Hereinafter, a description will be given of a correction amount omega _M torque estimation method using calculation methods and the correction amount omega _M of.

角速度エネルギ変化量Ｗ_ｅは一回の爆発行程中におけるクランク角速度の最小値（第１のクランク角速度）ω_ａ及び最大値（第２のクランク角速度）ω_ｂを利用して次式（２）のように表すことができる。

FIG. 3 shows an example of the relationship between the crank angle and the torque generated in the engine 1 (however, instantaneous torque). The torque periodically changes as the crank angle changes, and the area of the range surrounded by the change curve and the horizontal axis indicating torque = 0 (light gray portion in FIG. 3) is the average axial torque of the crankshaft 2. the T _e. There is a proportional relationship between the average shaft torque _Te and the change rate W _e of the angular velocity energy of the crankshaft 2 as shown in the following equation (1). C is a proportional coefficient, and D is a constant.

The angular velocity energy change amount W _e is expressed by the following equation (2) using the minimum value (first crank angular velocity) ω _a and the maximum value (second crank angular velocity) ω _b of the crank angular velocity during one explosion stroke. Can be expressed as:

By the way, the detected value of the crank angular velocity, that is, the angular velocity ω detected based on the output signal of the crank angle sensor 5, is the twist generated in the crankshaft 2, and the piston 10 and the connecting rod 11 connected to the crankshaft 2 (see FIG. 1). ) And the like are affected by the reciprocating inertia force generated by the reciprocating motion. Therefore, to accurately estimate the torque generated by the combustion, determine the true crank angular speed ω that eliminate these effects, the need to obtain an angular velocity changed energy W _e by Equation (2) using the value is there. This point will be described with reference to FIG.

  FIG. 4 shows the next cylinder in the explosion order after the piston 10 of a specific cylinder (for example, # 1 cylinder 1a furthest away from the flywheel 12 as shown in FIG. 1) reaches the compression top dead center TDC. 1 shows an example of the relationship between the crank angle and the crank angular speed ω until the piston 10 of the # 3 cylinder 1c) reaches TDC. If the influence of the reciprocating inertia force is ignored, as shown by the broken line in FIG. 4, the crank angular speed ω shows a minimum value near the TDC, that is, at a specific crank angle within the range from the end of the compression stroke to the beginning of the explosion stroke. The maximum value is shown at a specific crank angle in the middle period, typically around ATDC 90 °.

On the other hand, the torque (reciprocating inertia torque) that the reciprocating inertia force tries to rotate the crankshaft 2 generally varies in a cycle of 180 ° as shown in FIG. The reciprocating inertia torque acts in the direction of decelerating the crankshaft 2 from TDC to around ATDC 90 °, and the reciprocating inertia torque acts in the direction of accelerating the crankshaft 2 from ATDC 90 ° to 180 °. Due to the influence of such reciprocating inertia torque fluctuation, the maximum value of the crank angular velocity detected in the vicinity of ATDC 90 ° is decelerated from the original angular velocity (shown by a broken line) ω _{b as} shown by a solid line in FIG. ω _b ′. In order to accurately estimate the torque generated in the cylinder, it is necessary to add the change amount ω _M of the crank angular speed reduced by the reciprocating inertia torque to the detected value ω _b ′. Correction of the crank angular velocities ω _a and ω _b considering the influence of such reciprocating inertia torque is shown in the following equation (3).

In equation (3), the correction amount ω _c indicates a correction amount that accompanies an absolute change in crank angular speed during transient operation in which the rotation speed of the engine 1 changes. Further, the correction amount ω _T is a crank angular velocity correction amount representing the influence of twisting generated on the crankshaft 2. That is, even in a steady state where the engine 1 is rotating at a constant rotational speed, the crank angular speed minimum component ω _a ′ detected in the vicinity of the TDC includes a crank angular speed fluctuation component ω _T associated with the twist of the crankshaft 2. in which, in order to obtain an angular velocity energy variation W _e are also necessary to consider the variation component. The correction amounts ω _C and ω _T may be added as necessary, and may be omitted if they are small enough to be ignored. The calculation method of the correction amount ω _T that represents the influence of twisting may be the same as that in the prior art. As shown in FIG. 1, the correction amount ω _C at the time of transient operation is specified using the proportional relationship between the change amount of the detected crank angle speed value ω _a ′ between TDC and the change amount between TDC and ATDC 90 °. That's fine.

Next, a method of calculating the angular velocity change amount ω _M that represents the influence of the reciprocating inertia force will be described. The following calculation of the angular velocity change amount ω _M does not have to be performed for all the engines 1, and represents the same engine group in which the torque performance, more specifically, the correspondence relationship between the rotational speed and the load and the torque is the same. The at least one engine 1 may be implemented. That is, one or more engines from the same engine group are selected as test engines, and the map shown in FIG. 2 is created by calculating the relationship between the angular velocity change amount ω _M and the rotation speed and load using the test engines. May be stored in the storage device 7 of each engine 1 belonging to the same engine group.

また、エンジン１の図示トルクをτ_ｐ、フリクショントルクをτ_Ｆ、往復慣性トルクをτ_Ｍとすれば、これらのトルクと正味トルクτ_ｎとの関係は（５）式で表すことができる。

ここで、図示トルクτ_ｐは気筒内の圧力（燃焼圧）がピストン１０を押す力によりクランク軸２に発生するトルクである。フリクショントルクτ_Ｆはエンジン１の内部摩擦によって消費されるトルクである。 If the torque output from the engine 1 to the outside is the net torque τ _n , the relationship between the net torque τ _n and the crank angular speed ω can be expressed by the following equation (4). Here, I is the moment of inertia of the engine 1.

If the indicated torque of the engine 1 is τ _p , the friction torque is τ _F , and the reciprocating inertia torque is τ _M , the relationship between these torques and the net torque τ _n can be expressed by equation (5).

Here, the indicated torque τ _p is a torque generated in the crankshaft 2 by the force in the cylinder (combustion pressure) pushing the piston 10. The friction torque τ _F is a torque consumed by the internal friction of the engine 1.

If the equation (4) is integrated with respect to the angular velocity ω, the instantaneous angular velocity ω can be calculated. On the other hand, in order to calculate the net torque τ _n from the equation (5), the indicated torque τ _p and the friction torque τ _F are required. The indicated torque τ _p is calculated by the following equation (6) by mounting a sensor for measuring the combustion pressure (cylinder pressure) P on the engine 1. Incidentally, A _p is the area of the piston 10 receives combustion pressure, P _atm is the atmospheric pressure, F _p is the force the combustion pressure pushes the piston 10. The combustion pressure sensor may be attached to each of the cylinders 1a to 1d.

The friction torque τ _F is measured by rotating the crankshaft 2 of the engine 1 by motoring, that is, by an external drive source. Measurement of friction torque tau _F is the physical quantity that affects the friction torque tau _F, i.e., the engine speed (rotational speed) of the engine 1 coolant temperature, the temperature and viscosity of the lubricating oil or the like as appropriate to within operating region of the engine 1 Implement while changing. Then, a map of the friction torque τ _F using these physical quantities as an argument is created and the measured value is held there. FIG. 6 shows an example of the result of measuring the friction torque τ _F while changing the engine speed. In this example, the friction torque τ _F increases as the engine speed increases.

The reciprocating inertia torque τ _M can be calculated by the following equation (7). As shown in FIG. 7, L is the length of the connecting rod from the piston pin to the crank pin, R is the turning radius of the crank pin, and ρ = R / L in equation (7).

なお、（７）式にて往復慣性トルクを求めるためには角速度ωが必要となる。この場合、初回の計算時にのみクランク角センサ５の出力信号に基づいて特定した角速度ωを使用して（８）式で軸トルクτ_ｎを求め、これを（９）式に代入して角速度ωを算出し、２回目回以降の計算時には（９）式から求めた角速度ωを利用して毎回の軸トルクτ_ｎを求め、それらの値を（９）式の右辺に代入すればよい。この点は後述する図１３の説明においてさらに言及する。 From the above, the angular velocity ω can be calculated by measuring the combustion pressure of the engine 1. That is, the following equation (8) is obtained from the equations (4) and (5), transformed into the equation (8 ′) and integrated to derive the equation (9). The influence of the reciprocating inertia force is included by substituting the indicated torque τ _p obtained by the equation ()), the friction torque τ _F measured by motoring, and the reciprocating inertia torque τ _M represented by the equation (7), respectively, and solving for the angular velocity ω. The obtained angular velocity ω can be obtained.

Note that the angular velocity ω is required in order to obtain the reciprocating inertia torque using the equation (7). In this case, the shaft torque τ _n is obtained by the equation (8) using the angular velocity ω specified based on the output signal of the crank angle sensor 5 only at the first calculation, and this is substituted into the equation (9) to obtain the angular velocity ω. In the second and subsequent calculations, the angular velocity ω _n obtained from the equation (9) is used to determine the axial torque τ _n for each time, and those values are substituted into the right side of the equation (9). This point will be further described in the description of FIG.

Further, by obtaining the angular velocity ω with the reciprocating inertia torque τ _M = 0 in the equation (9), the angular velocity ω excluding the influence of the reciprocating inertia force can be obtained. That is, while substituting the indicated torque τ _p based on the combustion pressure P and the friction torque τ _F obtained by motoring in the equation (8 ′), the differential value of the angular velocity is obtained with the reciprocating inertia torque τ _M = 0, and the value Is integrated to obtain the angular velocity ω from which the influence of the reciprocating inertia force is excluded. Then, the difference between the two angular velocities ω thus obtained becomes an angular velocity change amount ω _M that represents the influence of the reciprocating inertia force. Figure 8 shows a crank angular speed (solid line) in consideration of the reciprocating inertia torque tau _M, reciprocating does not consider the inertia torque τ _M (τ _{M =} 0) of the crank angular speed (dashed line) computed respectively. The difference ω _M between the maximum values of the two crank angular velocities corresponds to the difference (ω _b −ω _b ′) between the crank angular velocities ω _b and ω _b ′ shown in FIG.

The angular velocity change amount ω _M at a specific engine speed and load can be obtained by the above calculation procedure. By carrying out such a calculation procedure for each representative combination of rotational speed and load selected from the operating range of the engine 1, the angular velocity change amount ω _Mb shown in FIG. 2B can be obtained.

Incidentally, in FIG. 1, the change in the angular velocity ω _M due to the influence of the reciprocating inertia force is shown as appearing in the vicinity of the maximum value ω _b , but in the calculation example in FIG. Also appears. In such a case, it is desirable to obtain the change amount ω _Ma of the angular velocity due to the effect of the reciprocating inertia force with respect to the crank angular velocity ω _a as well, and store this in the map as shown in FIG. . In this case, the above-described equation (3) may be corrected as the following equation (10).

Next, a torque estimation procedure by the ECU 6 will be described with reference to FIGS. In the following description, it is assumed that both the crank angular velocities ω _a and ω _b are corrected for the influence of the reciprocating inertia force. FIG. 9 shows a torque estimation routine that the ECU 6 repeatedly executes at a constant cycle in order to estimate the torque. In a first step S1 of this torque estimation routine, ECU 6 discriminates on the basis of whether or not the detected timing of the crank angular speed omega _a of the output signal of the crank angle sensor 5. Detection timing of the crank angular speed omega _a is the crank angular speed omega _{a 'is} set as detected by the first crank angle range is set between the end of the compression stroke toward the explosion stroke initial.

If it is determined that the detection timing of the crank angular speed omega _a step S1, ECU 6 detects crank angular speed omega _{a 'proceeds} to step S2. As an example, when a signal indicating the compression stroke top dead center TDC of each cylinder 1a to 1d is output from the crank angle sensor 5, the ECU 6 determines that the detection signal of the next convex portion of the rotor 4 is a crank signal from the detection signal of the TDC. The crank angular velocity ω _a ′ is detected by acquiring the time interval until the output from the angle sensor 5. The time interval in this case depends on the pitch of the convex portions provided on the rotor 4, and strictly speaking, in step S2, the average value of the crank angular velocity in the time interval of the output signal of the crank angle sensor 5 is detected. The detection time may be set so that the detected value best represents the minimum value of the crank angular velocity ω in one explosion stroke.

After detecting the crank angular velocity ω _a ′, the ECU 6 proceeds to step S3 to obtain the crank angular velocity correction amount ω _Ma representing the influence of the reciprocating inertia force from the map of FIG. A correction amount ω _M acquisition routine is executed. The contents of the routine of FIG. 10 will be described later. In subsequent step S4, ECU 6 obtains the correction amount omega _T of the angular velocity due to torsion of the crankshaft 2. In the next step S5, ECU 6 calculates a crank angular speed omega _a according to equation (9). Thereafter, the ECU 6 proceeds to step S6. If it is determined that it is not the detection timing of the crank angular speed omega _a step S1, ECU 6 proceeds to step S6 by skipping the process of step S2 to S5.

In step S6, the ECU 6 determines whether or not it is the detection time of the crank angular speed ω _b ′ based on the output signal of the crank angle sensor 5. Crank angular speed omega _{b 'detection} timing of the crank angular speed omega _b in the second crank angle range in the expansion _stroke' is set as detected. If it is determined that the detection time is reached, the ECU 6 proceeds to step S7 to detect the crank angular velocity ω _b ′. In the above example, the ECU 6 is a time interval from when the crank angle sensor 5 outputs the detection signal corresponding to ATDC 90 ° to when the detection signal of the next convex portion of the rotor 4 is output from the crank angle sensor 5. Is obtained to detect the crank angular velocity ω _b ′. The time interval in this case also depends on the pitch of the convex portions provided on the rotor 4, and strictly speaking, in step S7, the average value of the crank angular velocity in the time interval of the output signal of the crank angle sensor 5 is detected. The detection time may be set so that the detected value best represents the maximum value of the crank angular velocity ω in one explosion stroke.

After detecting the crank angular velocity ω _b ′, the ECU 6 proceeds to step S8 to obtain the crank angular velocity correction amount ω _Mb representing the influence of the reciprocating inertia force from the map of FIG. A correction amount ω _M acquisition routine is executed. In subsequent step S < _b > 9, the ECU 6 acquires the angular velocity correction amount ωc associated with the transient operation of the engine 1. Thereafter, ECU 6 proceeds to step S10, calculates a crank angular speed omega _b on the basis of the equation (9). Thereafter, the ECU 6 proceeds to step S11, where the change amount Δω ² is obtained by the equation (2) using the crank angular velocities ω _a and ω _b calculated in step S5 and step S10, and a cylinder is generated based on the change amount an estimate of the average axial torque T _e to be calculated by the equation (1). After the estimation of the torque _Te, the current routine is finished. If it is determined that it is not the detection timing of the crank angular velocity omega _b in step S6, ECU 6 terminates this routine skips steps S7 to S11.

Next, the correction amount omega _M acquisition routine of FIG. In the correction amount ω _M acquisition routine, the ECU 6 detects the rotational speed Ne of the engine 1 on the basis of the output signal of the crank angle sensor 5 in step S101, and the engine 1 on the basis of the output signal of the accelerator opening sensor 8 in the subsequent step S102. The load Q is detected. Thereafter, the ECU 6 proceeds to step S103, acquires the correction amount ω _Ma or ω _Mb corresponding to the rotational speed Ne and the load Q acquired in the current routine from the map of FIG. 2A or FIG. Return to processing. When the routine of FIG. 10 is executed as the subroutine of step S3 of FIG. 9, the map of FIG. 2A is used. When the routine of FIG. 10 is executed as the subroutine of step S8 of FIG. Select each of the maps in b).

According to the above processing, the correction amount ω _{M of the} crank angular speed representing the influence of the reciprocating inertia force is appropriately selected in association with the rotational speed Ne of the engine 1 and the load Q, and the crank angle is determined based on the correction amount ω _M. Torque estimation is performed after the detected angular velocity values ω _a ′ and ω _b ′ are corrected. Therefore, compared with the prior art in which the influence of the reciprocating inertia force is specified in association with only the rotational speed of the engine 1, the change amount Δω ² more accurately reflects the operating state of the engine 1, thereby estimating the torque. Accuracy is improved. In addition, while the combustion pressure is measured by the engine under test, the correction amount ω _M is calculated in association with the engine speed and the load to create a map, and this is stored in the storage device 7 of the ECU 6. It is not necessary to acquire the combustion pressure when performing torque estimation. Thereby, there is an advantage that it is not necessary to provide a combustion pressure sensor. Further, the correction amount omega _M ECU 6 because it is not necessary to calculate, calculating the load of the ECU 6 is reduced.

[Second form]
Next, a second embodiment of the present invention will be described. In this embodiment, the map of FIG. 2 described above is omitted, and instead of this, as shown in FIG. 11, the combustion pressure sensor 21 is attached to the engine 1 to detect the combustion pressure, and the correction described above based on the detected value. to perform the calculation of the amount ω _M at ECU6. The combustion pressure sensor 21 may be provided in at least one cylinder. In the example of FIG. 11, the combustion pressure sensor 21 is provided only for the # 4 cylinder 1 d closest to the flywheel 12. This is because the influence of the twist of the crankshaft 2 is the smallest in the cylinder closest to the flywheel 12. In FIG. 11, the same reference numerals are given to the portions common to FIG.

Further, as apparent from the above description, it is necessary to know the friction torque τ _F in order to calculate the correction amount ω _M from the combustion pressure. Therefore, in this embodiment, a map in which the friction torque τ _F measured by motoring is associated with arguments of the engine speed Ne and the engine water temperature Tw is created as shown in FIG. to use in the calculation of ω _M. Therefore, a water temperature sensor 22, etc. are connected required to obtain the friction torque tau _F in ECU6 as shown in FIG. 11.

Even in the second embodiment, the ECU 6 executes the torque estimation routine of FIG. 9 to estimate the torque. As a subroutine for obtaining the correction amount ω _M representing the influence of the reciprocating inertia force, the ECU 6 executes the routine of FIG. Instead, the routine of FIG. 13 is executed. In the correction amount ω _M acquisition routine of FIG. 13, the ECU 6 first acquires the combustion pressure P in step S201. When the combustion pressure sensor 21 is provided in only one cylinder, the measurement of the combustion pressure P is performed once while the crankshaft 2 rotates by a predetermined angle, for example, 720 ° corresponding to 4 cycles. May be acquired in step S1 as the combustion pressure P of all the cylinders in the subsequent control. Alternatively, the combustion pressure P may be measured a plurality of times within a predetermined angle range, and a value representative of those measurement values (as an example, an average value) may be acquired in step S1 as the combustion pressure P in the subsequent control. When the change in the combustion pressure P when the engine 1 is operating in the transient state affects the torque estimation accuracy, it is determined whether or not the engine 1 is operating in the steady state, and is determined to be in the steady state. The combustion pressure P may be acquired only when

In subsequent step S202, ECU 6 calculates the indicated torque tau _P by substituting acquired combustion pressure P in equation (6). In the next step S203, ECU 6 obtains the friction torque tau _F corresponding to the current engine speed Ne and the water temperature Tw by using a map of Figure 12. In the next step S204, the ECU 6 calculates the shaft torque τ _nR when the reciprocating inertia torque τ _M = 0 using the equation (8), and in the subsequent step S205, the obtained torques τ _p , τ _F and substituting tau _nR equation (9) determining the crank angular velocity omega _R by. The crank angular speed ω _{R obtained} here is a crank angular speed that does not include the influence of the reciprocating inertia torque τ _M.

In subsequent step S206, ECU 6 determines whether the calculated value of the crank angular speed calculated in the previously executed correction amount omega _M acquisition routine omega (value determined at step S210) is present. In other words, the routine determines whether or not it is first executed with respect to the calculation of the correction amount omega _M. For example, when the RAM of the storage device 7 is initialized and the past calculation result is deleted when the engine 1 is started, the condition of step S206 is denied when the routine of FIG. In the subsequent routine, the condition of step S206 is affirmed.

If the condition in step S206 is negative, the ECU 6 proceeds to step S207 and sets the initial value ω _init of the crank angular speed ω. The initial value ω _init is determined using the output signal of the crank angle sensor 5. For example, the average value of the detected value of the crank angular speed at the time when the process of step S207 is executed, more specifically, the average value in a range retroactive by a predetermined angle (180 ° or 720 °) with reference to the execution time of step S207 or the like is an initial value. Set as ω _init . On the other hand, when the condition in step S206 is affirmed, the ECU 6 proceeds to step S208, and the angular velocity ω used in the calculation of the shaft torque τ _M in step S208 is used as the crank angular velocity ω calculated in step S210 during the previous routine execution. Set as.

After setting the angular velocity ω in step S207 or S208, the ECU 6 proceeds to step S209, and calculates the reciprocating inertia torque τ _M by the equation (7) using the set angular velocity ω. Next, the ECU 6 proceeds to step S210, and calculates the crank angular velocity ω using the equation (9). The crank angular velocity ω obtained here is a value considering the influence of the reciprocating inertia force.

Subsequently, the ECU 6 subtracts the crank angular velocity ω obtained in step S210 from the crank angular velocity ω _R obtained in step S205, thereby obtaining a crank angular velocity correction amount ω _M (= ω _R −ω) representing the influence of the reciprocating inertia force. Ask. After finishing the above processing, the ECU 6 returns to the processing of FIG. When the routine of FIG. 13 is executed as a subroutine corresponding to step S3 of FIG. 9, the correction amount ω _M becomes the correction amount ω _Ma corresponding to the angular velocity ω _a and is executed as a subroutine corresponding to step S8 of FIG. In this case, the correction amount ω _M becomes the correction amount ω _Mb corresponding to the angular velocity ω _b .

According to the above embodiment, since the seek correction amount omega _M based on the combustion pressure P measured in the engine 1 itself becomes the estimation target torque, the estimated torque more accurately as compared with the first embodiment can do. In particular, even when the rotation speed and the load are the same, other engine control parameters that affect the torque, for example, even when the combustion injection timing and the fuel injection amount are different, the correction amount ω _M that reflects these changes can be obtained. There is. Regarding the calculation of the correction amount ω _M , the combustion pressure of the other cylinder is estimated using the combustion pressure P detected by the combustion pressure sensor 21, and the estimated value of each combustion pressure is used for each cylinder. 13 routine may be obtained correction amount omega _M of each cylinder running. Alternatively, the routine of FIG. 13 is executed only for the cylinder provided with the combustion pressure sensor 21, and torque estimation is executed for the other cylinders using the correction amount ωM obtained by the routine of FIG. May be. In any case, the combustion pressure sensor 21 is provided only for a single cylinder, and the correction amount ω _M for all the cylinders is obtained based on the detected value, so it is not necessary to actually measure the combustion pressures of all the cylinders. The number of combustion sensors required for torque estimation can be reduced, and the number of assembly steps and the number of parts of the engine 1 can be reduced.

  In the above embodiment, the ECU 6 functions as a correction amount acquisition unit by executing the routine of FIG. 10 or FIG. 13, and the ECU 6 functions as an angular velocity correction unit by executing steps S5 and S10 of FIG. 9 is executed, the ECU 6 functions as torque estimating means. However, the present invention is not limited to the above embodiment, and may be implemented in various forms.

For example, in the second embodiment, the combustion pressure P is measured by the combustion pressure sensor 21, but acquisition of the combustion pressure P is not limited to this. An operation model of the engine 1 may be mounted on the ECU 6 to estimate the combustion pressure corresponding to the operation state. In the second embodiment has been determined an angular velocity ω in consideration of the reciprocating inertia torque tau _M by calculation of ECU 6, the angular velocity is detected based on the output signal of the crank angle sensor 5 are those containing the influence of the reciprocating inertia force This corresponds to the angular velocity indicated by the solid line in FIG. Therefore, instead of calculating the angular velocity ω in consideration of the reciprocating inertia force, the detected value of the angular velocity by the crank angle sensor 5 is used, and the indicated torque τ _P based on the combustion pressure P and the friction torque τ _F obtained from the map of FIG. The angular velocity ω (corresponding to the broken line in FIG. 8) excluding the influence of the reciprocating inertia force is calculated by the ECU 6 according to the equation (9), and the correction amount ω _M may be obtained from the difference therebetween. Each calculation of FIG. 13 may be performed by a computer unit different from the ECU 6. In this case, the correction amount omega _M acquisition routine may be configured as shown in FIG. 14. That is, determine the crank angular velocity omega _R which includes the effect of the reciprocating inertia force to step S201~S205 running similarly in FIG. 13, followed by the crank angular velocity omega _R by step S211 to this, the crank angle sensor 5 by subtracting the detection value omega crank angular speed based on the output signal may be obtained correction amount omega _M.

In the first and second embodiments described above, the correction amounts ω _Ma and ω _Mb representing the influence of the reciprocating inertia force are obtained for both the first crank angular velocity ω _a and the second crank angular velocity ω _b. only the second crank angular speed omega _b may be corrected by the correction quantity omega _M. In other words, it in order to maintain a proportional relationship between the angular velocity the kinetic energy of the variation [Delta] [omega ² and the torque T _e exactly the correcting by the correction amount omega _M representing the influence of the reciprocating inertia force of both angular velocity omega _a, omega _b Desirably, as long as it is limited to the purpose of compensating for the decrease in angular velocity affected by the reciprocating inertia force appearing in the second crank angle range near ATDC 90 °, the second crank angular velocity is expressed as shown in equation (3). It is only necessary to perform correction using the correction amount ω _M only for ω _b .

In each of the above embodiments, the case where the center of the crankshaft 2 exists on the centerline of the piston 10 of the engine 1 (FIG. 7) has been described, but the present invention shows that the centerline of the piston 10 and the crankshaft as shown in FIG. The present invention can also be applied to an engine having a so-called offset crank mechanism in which the centers of the two are displaced from each other. Hereinafter, a calculation example of the correction amount ω _{M in} the case of the offset crank mechanism will be described. In FIG. 14, L is the length of the connecting rod from the piston pin to the crank pin, R is the turning radius of the crank pin, e is the crank offset amount, α is the offset angle, β is the connecting rod tilt angle, and θ is the crank angle. .

また、クランク軸２の回りの回転質量をＭ_ｃ、クランク角θにおけるクランク角加速度の検出値をａ_{ｃｒａｎｋ}（θ）、燃焼圧をＰ（θ）、燃焼圧を受けるピストン面積をＡ_ｐとすれば、軸トルクτ_ｎは次式（１２）のように表すことができる。

ここで、角加速度ａ_{ｃｒａｎｋ}（θ）は次式（１３）で与えられる。ω_ｎはクランク角速度の検出値、ω_ｎ−１は前回のクランク角速度の検出値であり、ΔＴはクランク角速度の検出の時間間隔である。

In the offset crank mechanism of FIG. 15, the relationship between the combustion pressure P and the indicated torque τ _p can be expressed as the following equation (11).

By addition, around the rotating mass of the crankshaft 2 M _c, a _crank detection value of the crank angular acceleration at the crank angle theta _(theta), the combustion pressure P (theta), the piston area for receiving combustion pressure and A _p For example, the shaft torque τ _n can be expressed as the following equation (12).

Here, the angular acceleration a _crank (θ) is given by the following equation (13). ω _n is a detected value of the crank angular speed, ω _n−1 is a detected value of the previous crank angular speed, and ΔT is a time interval of detecting the crank angular speed.

The reciprocating inertia torque τ _M can be expressed by the following equation (14) when the estimated acceleration value of the piston 10 at the crank angle θ is a _piston (θ).

以上から、クランク角θにおける往復慣性力の影響を除外したクランク角速度ω_Ｒ（θ）は次式（１６）で表すことができる。

そして、クランク角センサ５の出力信号に基づいて検出した第２のクランク角速度をω_ｂ′とすれば、往復慣性力の影響を表す角速度の変化量ω_Ｍは次式（１７）にて求めることができる。

このような手順でクランク角速度の変化量ω_Ｍを算出すれば、上述した第１の形態又は第２の形態と同様の構成によりオフセットクランク機構の場合における第２のクランク角速度ω_ｂを正しく求めてトルクの推定精度を向上させることができる。 From the above, the piston speed V _piston (θ) at the crank angle θ can be expressed by the following equation (15).

From the above, the crank angular velocity ω _R (θ) excluding the influence of the reciprocating inertia force on the crank angle θ can be expressed by the following equation (16).

Then, if the second crank angular velocity detected based on the output signal of the crank angle sensor 5 is ω _b ′, the angular velocity variation ω _M representing the effect of the reciprocating inertia force is obtained by the following equation (17). Can do.

If the change amount ω _M of the crank angular speed is calculated by such a procedure, the second crank angular speed ω _b in the case of the offset crank mechanism is correctly obtained by the same configuration as the first form or the second form described above. Torque estimation accuracy can be improved.

The figure which shows the structure of the internal combustion engine to which the torque estimation apparatus which concerns on the 1st form of this invention was applied. The figure which shows the map of the angular velocity correction amount which the memory | storage device of ECU memorize | stores. The figure which shows an example of the relationship between a crank angle and a torque. The figure which shows an example of the relationship between a crank angle and a crank angular velocity. The figure which shows an example of the relationship between a crank angle and a reciprocating inertia torque. The figure which shows an example of the relationship between an engine speed and friction torque. The figure which shows schematic structure of the crank mechanism of an internal combustion engine. The figure which shows an example of the calculation example of crank angular velocity. The flowchart which shows the torque estimation routine which ECU performs. 10 is a flowchart showing a correction amount acquisition routine executed by the ECU as a subroutine of FIG. 9 in the first embodiment. The figure which shows the structure of the internal combustion engine to which the torque estimation apparatus which concerns on the 2nd form of this invention was applied. The figure which shows the map of the friction torque which the memory | storage device of ECU memorize | stores. 10 is a flowchart showing a correction amount acquisition routine executed by the ECU as a subroutine of FIG. 9 in the second embodiment. 14 is a flowchart showing a correction amount acquisition routine of another form in which the routine of FIG. 13 is partially changed. The figure which shows schematic structure of the offset crank mechanism of an internal combustion engine.

Explanation of symbols

1 engine (internal combustion engine)
1a, 1b, 1c, 1d Each cylinder 2 Crankshaft 3 Crank angle detection device 4 Rotor 5 Crank angle sensor (Crank angle signal output means)
6 Engine control unit (correction amount acquisition means, angular velocity correction means, torque estimation means)
7 storage device 8 accelerator opening sensor 10 piston 11 connecting rod 12 flywheel 21 combustion pressure sensor (combustion pressure acquisition means)
22 Water temperature sensor

Claims (12)

During an explosion stroke in which a first crank angular velocity is detected within a first crank angle range set between the end of the compression stroke and the beginning of the explosion stroke, and a predetermined crank angle is separated from the first crank angle range. A torque estimation method for an internal combustion engine that detects a second crank angular speed in a second crank angle range set to, and estimates torque generated in a cylinder based on the first and second crank angular speeds;
Obtaining a change amount of a crank angular speed that represents an influence of a reciprocating inertia force according to a load of the internal combustion engine generated in the second crank angle range as a correction amount of the second crank angular speed;
Correcting the detected value of the second crank angular speed based on the obtained correction amount of the second crank angular speed;
Estimating the torque using the corrected second crank angular velocity;
A torque estimation method for an internal combustion engine, comprising:   A map in which the rotational speed and load of the internal combustion engine and the correction amount of the second crank angular velocity are associated with each other is created in advance, and the map is stored in a storage device provided in the control device of the internal combustion engine, and the second And obtaining a correction amount of the second crank angular speed corresponding to the rotational speed and load of the internal combustion engine based on the map stored in the storage device. Item 2. The torque estimation method according to Item 1.   The method further includes the step of acquiring the combustion pressure of one or more cylinders, and in the step of obtaining the correction amount of the second crank angular velocity, the correction amount of the second crank angular velocity is calculated using the acquired combustion pressure. The torque estimation method according to claim 1, wherein: Obtaining a change amount of a crank angular speed, which represents an influence of a reciprocating inertia force according to a load of the internal combustion engine, generated in the first crank angle range as a correction amount of the first crank angular speed;
Correcting the detected value of the first crank angular speed based on the obtained correction amount of the first crank angular speed;
Estimating the torque using the corrected first and second crank angular velocities, respectively;
The torque estimation method according to claim 1, further comprising:   A map in which the rotational speed and load of the internal combustion engine and the correction amount of the first crank angular velocity are associated with each other is created in advance, and the map is stored in a storage device provided in the control device of the internal combustion engine. In the step of obtaining the crank angular speed correction amount, the first crank angular speed correction amount corresponding to the rotational speed and load of the internal combustion engine is acquired based on the map stored in the storage device. The torque estimation method according to claim 4.   The method further includes the step of acquiring the combustion pressure of one or more cylinders, and in the step of obtaining the correction amount of the first crank angular velocity, the correction amount of the first crank angular velocity is calculated using the acquired combustion pressure. The torque estimation method according to claim 4, wherein: Crank angle signal output means for outputting a signal corresponding to the crank angle;
Based on the output signal of the crank angle signal output means, the first crank angular speed is set within the first crank angle range set between the end of the compression stroke and the initial stage of the explosion stroke. Crank angular speed detection means for detecting a second crank angular speed in a second crank angle range set during an explosion stroke separated from the crank angle by a predetermined crank angle;
A torque estimation device for an internal combustion engine, comprising: a torque estimation unit that estimates torque generated in a cylinder based on the first and second crank angular velocities;
A correction amount obtaining means for obtaining, as a correction amount for the second crank angular velocity, a change amount of the crank angular velocity that represents the influence of the reciprocating inertia force according to the load of the internal combustion engine that occurs in the second crank angle range;
Angular velocity correction means for correcting the detected value of the second crank angular velocity based on the obtained correction amount of the second crank angular velocity,
The torque estimation device for an internal combustion engine, wherein the torque estimation means estimates the torque by using the corrected second crank angular velocity.   A storage device for storing a map in which the rotational speed and load of the internal combustion engine and the correction amount of the second crank angular velocity are associated with each other; and the correction amount acquisition means is based on the map stored in the storage device The torque estimation device according to claim 7, wherein a correction amount of the second crank angular speed corresponding to the rotational speed and load of the internal combustion engine is acquired.   Combustion pressure acquisition means for acquiring the combustion pressure of one or more cylinders is further provided, and the correction amount acquisition means calculates the correction amount of the second crank angular velocity using the acquired combustion pressure. The torque estimation device according to claim 7. The correction amount acquisition means, in addition to the correction amount of the second crank angular speed, changes in the crank angular speed representing the influence of the reciprocating inertia force generated in the first crank angle range according to the load of the internal combustion engine. An amount as a correction amount of the first crank angular velocity,
The angular velocity correction means corrects the detected value of the first crank angular velocity based on the obtained correction amount of the first crank angular velocity in addition to the correction of the second crank angular velocity,
The torque estimation means estimates the torque using the corrected first and second crank angular velocities, respectively.
The torque estimation device according to any one of claims 7 to 9, wherein   The storage device further stores a map in which the rotational speed and load of the internal combustion engine and the correction amount of the first crank angular velocity are associated with each other, and the correction amount acquisition unit is based on the map stored in the storage device. The torque estimation device according to claim 10, wherein a correction amount of the first crank angular speed corresponding to the rotational speed and load of the internal combustion engine is acquired.   Combustion pressure acquisition means for acquiring the combustion pressure of one or more cylinders is further provided, and the correction amount acquisition means calculates the correction amount of the first crank angular velocity using the acquired combustion pressure. The torque estimation device according to claim 10.

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