JPH074302A - Engine torque detecting method and device therefor - Google Patents

Abstract

PURPOSE:To reduce the sampling frequency of output of a combustion pressure sensor so as to heighten computation processing speed and dissolve possibility causing deterioration of accuracy by searching the engine output torque by the use of output of a combustion pressure sensor nearby a specified time band. CONSTITUTION:In a four cycle engine 10, output of a camshaft angle sensor 32 detecting reference crank position theta0 from the rotation angle of a camshaft 22, a combustion pressure sensor 36, an air flow meter detecting an intake air quantity, an engine cooling water thermometer, etc., are introduced to a digital computer 30. Especially the engine output torque is estimated by the use of the output of the combustion pressure sensor 36. In this method. the engine output torque T is obtained by the use of output of the combustion pressure sensor nearby the time band from a time point t1 when the time differential of combustion pressure dP/dt becomes maximum to a time point t2 when the differential becomes zero. Hereby the sampling frequency of output of the combustion pressure sensor 36 is reduced, and hence the computation processing speed is heightened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine torque detecting method and apparatus for estimating engine output torque from combustion pressure.

[0002]

2. Description of the Related Art Various lean-burn engines have been proposed which operate a spark-ignition gasoline engine at a mixture ratio significantly leaner than a theoretical air-fuel ratio for reasons such as fuel economy improvement and exhaust gas purification. As one of them, there is one that detects a lean combustion limit, that is, a torque fluctuation allowable limit from a combustion state, and feedback-controls an air-fuel ratio, an ignition timing and the like.

Here, it is considered that the combustion state is detected by a combustion pressure sensor. That is, since the change between the combustion pressure (or the average effective pressure) and the torque has a certain correlation, the combustion pressure is used instead of detecting the torque.

Therefore, the combustion pressure in the period from the vicinity of the end of the intake stroke to the expansion stroke is set a plurality of times at fixed time intervals (for example, 5 times).
It was proposed that the torque substitute value [T] be obtained by sampling and sampling based on a certain formula (preprints of academic lectures, published by the Society of Automotive Engineers of Japan, vol. 924, p. 69, 1992).
(October year).

[0005]

However, this method requires sampling a plurality of times within a relatively narrow predetermined crank angle to calculate the torque substitute value [T], which requires a long processing time and is compatible with high-speed engine operation. There was a problem that it could not be done or it became difficult to respond.

Therefore, instead of sampling a plurality of times, it is possible to detect only the maximum value of the combustion pressure and estimate the combustion pressure using this maximum value. However, since this maximum combustion pressure has a weak correlation with the torque, there is a problem that the accuracy of torque estimation is poor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to reduce the number of output samplings of the combustion pressure sensor to increase the arithmetic processing speed and to detect the torque of the engine without the possibility of lowering the accuracy. A primary object is to provide a method. A second object is to provide an apparatus used directly for carrying out this method.

[0008]

According to the present invention, a first object is to estimate the engine output torque by using the output of the combustion pressure sensor, and the time width until the time differential of the combustion pressure becomes 0 from the maximum value. This is achieved by an engine torque detection method characterized in that the engine output torque is obtained using the output of a combustion pressure sensor in the vicinity.

A second object is to provide a reference crank position detecting means and a constant crank angle from the reference crank position in an engine torque detecting device for obtaining an engine output torque by using a time derivative of a combustion pressure output from a combustion pressure sensor. A reference time calculating means for obtaining a reference time L required for the rotation of
Using the calculated reference time L, the time from the reference crank position to the gate opening D = L · (f + r (√L−c)}
(F, r, and c are constants), and the time differential is integrated with respect to time from the time the gate is opened until the time differential of the combustion pressure output by the combustion pressure sensor becomes zero. It is achieved by an engine torque detecting device characterized by including an integrating means for calculating an estimated torque value [T].

[0010]

1 is a block diagram showing the concept of an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram. In FIG. 1, reference numeral 10
Is a 4-cycle engine, 12 is a cylinder, 14 is a piston, 16 is a crankshaft, 18 is an intake valve, and 20 is an exhaust valve. The exhaust valve 20 is opened and closed by an overhead camshaft 22.
Fuel (gasoline) is supplied from the fuel injection valve 26 into the intake passage 24, and the supply amount thereof is variable by controlling the valve opening time. 28 is a spark plug.

30 is a digital computer (hereinafter CP
U), and the CPU 30 has a camshaft angle sensor 3 for detecting the reference crank position θ ₀ from the rotation angle of the camshaft 22.
2. Outputs of a combustion pressure sensor 36, an air flow meter (not shown) for detecting the amount of intake air, an engine cooling water thermometer, an intake air thermometer, etc. are introduced.

A cam shaft angle sensor 32 provided on the cam shaft 22.
Is the top dead center (TD) of the crankshaft 16 near the end of the intake stroke.
C) Detect the reference crank position θ ₀ when it is in the vicinity.
That is, the position θ _{0 at} which the output θ of the camshaft angle sensor 32 shown in FIG.
Is detected by the reference crank position detecting means 40 provided in the above, and this position θ ₀ is set as the reference crank position, and the time point t ₀ is stored in memory.

The camshaft angle sensor 32 is, for example, the camshaft 2
It has a structure for detecting the passage of a permanent magnet fixed to the second sprocket, and outputs the minimum (minus peak) pulse when it is delayed by a constant crank angle from the reference crank position θ ₀ . While rotating by this constant crank angle, C
The PU 30 counts N sampling pulses of a predetermined frequency unique to the CPU 30. The reference time calculation means 42 of the CPU 30 calculates the reference time L by multiplying the pulse number N by a constant s.

This reference time L is proportional to the time required to rotate a fixed crank angle. This reference time L
Is used for D calculation in the D calculation means 44.

The combustion pressure sensor 36 uses a piezo element and outputs the time derivative dP / dt of the combustion pressure P, and its output waveform is as shown in FIG. 2 (B). CPU30
Has a gate closing detection means 46 and detects a time point t ₂ when dP / dt = 0.

The D calculation means 44 calculates a time point t _{1 at} which the output dP / dt of the combustion pressure sensor 36 becomes maximum.
The time t ₁ may be determined by monitoring the dP / dt in CPU30, but by calculation in this embodiment predicts in advance the time point t _1, when actually reaches this time t ₁ immediately gate G ( 2 (see FIG. 2B).

This calculation is performed by, for example, D = L · {f + r ·
(√L−c)}. Here, f, r, and c are constants, and by properly setting these constants based on experiments or calculations, the time t of the reference crank position is set.
_{It has} been found that the time point t ₁ after a lapse of time D from ₀ coincides well with the position where dP / dt becomes maximum. Therefore, the adding means 48 adds the time D to the reference position t ₀ to obtain the time point t ₁ = t ₀ + D when the gate G is opened.

Various calculations can be made for the calculation of D instead of the above equation. For example, a good result can be obtained by replacing the part of √L in this equation with log L. It was also found that good results can be obtained by using D = τ · (α + β). In this equation, τ is a variable determined by L and is the reciprocal of the crank angular velocity ω (τ = 1 /
ω) and α are constants, β is a variable for adjusting the influence of fluctuations in the engine rotation speed, and β = γ · (ω ^−1/2 −c) (where γ and c are constants).

Reference numeral 50 is an integrating means, which is composed of an analog integrating amplifier independent of the CPU 30. The integrating means 50 integrates the output dP / dt of the combustion pressure sensor 36 during the opening period of the gate G, that is, from time t ₁ to time t ₂ . This integrated value is used as the estimated torque value [T] by the CPU 30.
Entered in. The integrating means 50, as shown in FIG. 2 (C), the difference of the estimated torque value of the combustion pressure P (t ₁₎ of the combustion pressure P (t ₂₎ and the time point t ₁ at time t ₂ [T ] Means to ask.

The CPU 30 obtains the fuel injection amount corresponding to the estimated torque value [T] by the fuel control means 52 and opens the fuel injection valve 26 for a predetermined time. Further, the ignition timing control means 54 calculates the ignition timing corresponding to the estimated torque value [T],
An ignition signal is sent to the ignition circuit 56 such as CDI. As a result, the spark plug 28 generates an ignition spark by this ignition signal.

In this embodiment, since the integrating means 50 is composed of an analog circuit, the calculation of the CPU 30 is simple and fast. However, it goes without saying that the CPU 30 may have the function of the integrating circuit 50. Further, the estimated torque value [T] may be obtained using data of an appropriate number of sampling points instead of integration. Further, in this embodiment, the time point t ₂ at which the gate G is closed is calculated from dP / dt = 0.
The open period G may be set by G = L · w (w is a constant). In this case, the time point t ₂ when the gate G is closed is t ₂ = t ₁
It can be set by + L · w.

FIG. 3 is a block diagram showing a second embodiment, and FIG. 4 is an operation flow chart thereof. In this embodiment, the time t for obtaining the estimated torque value [T] = {P (t ₂ ) −P (t ₁ )}
The method of setting ₁ and t ₂ is different from that of the embodiment shown in FIGS.

In FIG. 3, the output θ _c of the crank angle sensor 34 provided in the engine 10 and the output dP / dt of the combustion pressure sensor 36 composed of a piezo element are input to the A / D converter 60, where they are respectively digitalized. Converted to signal and C
It is input to the PU 30A. The output θ _c of the crank angle sensor 34 is a reference crank angle pulse signal θ ₀ that changes between positive and negative at a reference crank position near top dead center for each rotation of the crank shaft, and a crank angle that is constantly output at each predetermined crank angle. And a pulse signal θ _p .

The CPU 30A performs the operation shown in FIG. 4 using the operation program stored in the memory 62 and a predetermined arithmetic expression. If the engine 10 is not stopped (step 100), the input of the reference crank angle pulse signal θ ₀ is awaited (step 102). When this signal θ ₀ is input,
The CPU 30A constantly inputs the crank angle pulse θ
Using _P crankshaft rotation speed R (unit R.P.M)
Is calculated and output. In the case of a 4-cycle engine, the reference crank angle pulse θ ₀ is detected once every two rotations of the crankshaft.

The CPU 30A is similar to that of the above embodiment,
Since the output of the crank angle sensor 34 becomes maximum (plus peak), the reference crank angle position (θ ₀ ) is obtained, and at this time t = t ₀ . Then, the time until this output becomes the minimum (minus peak), that is, the reference time L is obtained (step 104). CPU30A also reference crank angle position of the positive peak to be t = t ₀ (θ
_{At 0} ), the timer is reset to zero and integration is started (step 106).

On the other hand, the CPU 30A obtains t ₁ and t ₂ by a predetermined arithmetic expression (step 108). This formula is stored in the memory 62 in advance, but various formulas such as the following can be used. The expression of A is a linear expression of L. B, C and D are quadratic expressions or polynomials of L.

[0027]

## EQU1 ## A: t ₁ = μL + ν t ₂ = t ₁ + λL B: t ₁ = μL + νL ² t ₂ = t ₁ + λL + kL ² C: t ₁ = μL + νL ^3/2 t ₂ = t ₁ + λL + kL ^3/2 D: t ₁ = μL + ν · L / log L t ₂ = t ₁ + λL + k · L / log L

Which equation is used depends on the output waveforms of the engine 10 and the combustion pressure sensor 36, etc., but should be determined experimentally. When t = t ₁ (step 110), the CPU 30A obtains and stores the combustion pressure P (t ₁ ) at that time (step 112). This combustion pressure P (t ₁ )
Is obtained by integrating the output dp / dt of the combustion pressure sensor 46.

Next, when t = t ₂ (step 11
4), P (t ₂ ) is calculated, and the estimated torque value [T] = {P
(T ₂ ) −P (t ₁ )} is calculated (step 11
6). The CPU 30A further integrates the estimated torque value [T] with a constant T ₀ to obtain the torque T = T ₀ ·.
[T] is obtained and output (step 118). Then, the process returns to step 100 and the above operation is repeated. The operation cycle of steps 100 to 118 is sufficiently faster than the rotation cycle of the engine, and the operation of one cycle is performed substantially instantaneously, so that the delay due to the calculation hardly poses a problem.

FIG. 5 is an operation flow chart of the third embodiment.
In this embodiment, the crank angle θ is obtained by using the crank angle pulse θ _p which the crank angle sensor 34 constantly outputs for each minute rotation angle of the crank shaft, and the crank angles θ are t ₁ and t _2.
Combustion pressure P (θ ₁₎ in which the angle theta ₁ theta ₂ corresponds to, P
(Θ _{2 1} is obtained.

That is, in FIG. 5, similarly to FIG. 4, the reference crank angle position (θ ₀ ) is obtained (step 102), and the crank rotation speed R and the reference time L are obtained (step 1).
04), t ₁ and t ₂ are calculated (step 108). Then, the crank angles θ ₁ and θ ₂ corresponding to t ₁ and t ₂ obtained in step 108 are obtained. This calculation is performed using the crankshaft rotation speed R (RPM) in step 108A.
It is performed by the formula shown in.

When the crank angle θ becomes θ ₁ (step 1
10A), and the combustion pressure P (θ ₁ ) at this time is obtained and stored (step 112A). Similarly, when θ ≧ θ ₂ (step 114A), the estimated torque value [T] is changed to [T] =
({P (θ ₂ ) −P (θ ₁ )}) (step 116A). The torque T is calculated from T = T ₀ · [T] (step 118). According to this embodiment, the timer is used. Becomes unnecessary.

FIG. 6 is a block diagram showing a fourth embodiment, and FIG. 7 is an operation flow chart thereof. In FIG. 6, 64 is a charge amplifier, which integrates the output dP / dt of the combustion pressure sensor 36 and converts it into an analog signal indicating the combustion pressure P. C
The PU 30B detects the reference crank angle (θ ₀ ) (step 102) and calculates and outputs the rotation speed R (step 104B).

The CPU 30B obtains the differential value dP / dt of the combustion pressure P obtained by the charge amplifier 64 (step 20).
0), the time point at which this differential value dP / dt reaches the maximum value is t ₁
(Step 202). Then, the combustion pressure P (t ₁ ) at this time point t ₁ is stored (step 204).
The CPU 30B calculates dP / dt again (step 206), and obtains the time point t ₂ when dP / dt = 0 (step 208). Then, the combustion pressure P (t ₂ ) at this time is stored.

Next, the difference between the combustion pressures P (t ₂ ) and P (t ₁ ) is set as the estimated torque value [T] (step 212), and the torque T is calculated by T ₀ · [T] (step 11).
8). In this figure, the same parts as those in FIGS. According to the embodiment shown in FIG. 7, since the maximum dP / dt and the time points t ₁ and t ₂ at 0 are detected and the combustion pressure at that time is obtained, the torque T can be accurately calculated even if the engine speed R varies. Is required. Further, the maximum and 0 of dP / dt can be determined by the program of the CPU 30B, and the integration of dP / dt can also be processed by the program, so the configuration is simple.

FIG. 8 is a diagram for explaining another embodiment of the method of setting t ₁ and t ₂ . In the above-mentioned first to fourth embodiments,
The combustion pressures P (t ₁ ) and P (t ₂ ) are obtained at times t ₁ and t ₂ at which dP / dt becomes maximum and 0. However, the present invention may be performed in the vicinity of these time points t ₁ and t ₂ , and for example, the combustion pressures P (t ₁ ′) and P (t _{2 at} t ₁ ′, t ₂ , ′ and t ₁ ″ shown in FIG. ′) And P (t ₁ ″) may be used.

In FIG. 8, t ₁ ′ and t ₂ ′ are advanced by a fixed time Lα, Lβ from t ₁ and t ₂ , respectively. Here, L is a reference time, and α and β are constants. If t = t ₀ is used as a reference (see FIG. 2), t ₁ = D
Therefore, t ₁ ′ becomes t ₁ ′ = (D−Lα), and t
₂ ′ = (D + Lw−Lβ). Here, Lw is shown in FIG.
Corresponding to (t ₂ −t ₁ ). t ₂ ″ is obtained by delaying t ₂ by Lβ. Therefore, t ₂ ″ is t
₂ ″ = (D + Lw + Lβ).

The curve P shown in FIG. 8 has a small slope near t _{2 and a} large slope near t ₁ , so that α <β should be set. Since it is desirable that t ₂ ′ is located on the t ₂ side with respect to the middle of t ₁ and t ₂ , β / w
Should be set to <0.5. Thus t ₁ ′, t
_{When 2} ′ or t ₂ ″ is obtained, the estimated torque value [T] is, for example, {P (t ₂ ′) −P (t ₁ ′)},
It can be obtained by {P (t ₂ ″) −P (t ₁ ′)} etc. Therefore, using this [T], the torque T can be further calculated.
Can be obtained by, for example, T = T ₀ · [T].

The obtained estimated torque value [T] can be used not only for controlling the fuel injection amount and ignition timing as in the embodiment, but also for controlling the EGR amount and the secondary air amount added to the exhaust gas. it can. When the variable valve timing function is provided in which the opening / closing timing of the intake / exhaust valve is variable, this valve timing may be controlled using the estimated torque value [T].

[0040]

As described above, according to the first aspect of the present invention, the combustion in the vicinity of the time width from the time (t ₁ ) at which the time differential dP / dt of the combustion pressure reaches its maximum value to the time (t ₂ ) at which it reaches 0. Since the engine output torque (estimated torque value [T]) is obtained using the pressure sensor output, the number of samplings of the output of the combustion pressure sensor is reduced, and the processing speed can be increased. In addition, the accuracy is improved because the torque is not estimated using only the maximum value of the combustion pressure.

When a piezo element is used as the combustion pressure sensor, the output of the piezo element is a time derivative of the combustion pressure, and if this is integrated by an analog integrator amplifier, the arithmetic processing of the CPU becomes even faster (claim 2). ). The time point (t ₁ ) at which the time derivative dP / dt becomes maximum, that is, the time point when the gate G opens may be calculated (claim 3). Since determined this time t ₁ prior to the time point t ₁ According to this calculation, delay in operation speed of the CPU is improved even more precision not matter. Furthermore, the invention of claim 4 provides an apparatus which is used directly for carrying out the method.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of its operation.

FIG. 3 is a block diagram of a second embodiment.

[Fig. 4] Flow chart of its operation

FIG. 5 is an operation flow chart of the third embodiment.

FIG. 6 is a block diagram of a fourth embodiment.

FIG. 7: Flow chart of the operation

FIG. 8 is a diagram illustrating another method of setting t ₁ and t ₂ .

[Explanation of symbols]

 10 Engine 30, 30A, 30B CPU 32 Camshaft Angle Sensor 34 Crank Angle Sensor 36 Combustion Pressure Sensor 40 Reference Crank Position Detecting Means 42 Reference Time Calculating Means 44 D Calculating Means 50 Integrating Means

Claims (4)

[Claims] 1. A method for estimating engine output torque using the output of a combustion pressure sensor, wherein the engine output is obtained by using the combustion pressure sensor output in the vicinity of the time width from the maximum value of the combustion pressure to zero. A method for detecting torque in an engine, characterized by obtaining torque. 2. The engine torque detecting method according to claim 1, wherein the combustion pressure sensor outputs a time derivative of the combustion pressure by a piezo element, and the combustion pressure is obtained by integrating the output of the combustion pressure sensor by an analog integrating amplifier. 3. The time at which the time derivative of the combustion pressure becomes maximum is
From the reference time point output at a constant crank angle position, the following equation: D
= L · {f + r (√L−c)} (where L is a variable representing a reference time, f, r, and c are constants): The time D obtained by Method. 4. A torque detecting device for an engine for obtaining an engine output torque by using a time derivative of a combustion pressure output from a combustion pressure sensor, a reference crank position detecting means, and a reference required for rotating a reference crank position by a constant crank angle. Reference time calculating means for obtaining the time L and the obtained reference time L
Time from the reference crank position to gate opening using D = L · (f + r (√L−c)} (f, r and c are constants)
And the D calculation means for calculating the above, and the time derivative of the combustion pressure output by the combustion pressure sensor from the time the gate is opened until the time derivative becomes 0, the time derivative is integrated with respect to time to obtain an estimated torque value [T]. An engine torque detection device comprising: an integrating means.