JPH11193743A - Engine cylinder pressure detector - Google Patents

Abstract

(57) [Problem] To provide an in-cylinder pressure detecting device capable of detecting, with high accuracy, an in-cylinder pressure suitable for engine control even when there is a change in atmospheric pressure. SOLUTION: In-cylinder pressure detected by an in-cylinder pressure detecting means in a predetermined crank angle range in which it is estimated that the pressure in the cylinder takes a pressure value close to the atmospheric pressure, and intake air detected by an intake pipe internal pressure detecting means. The differential pressure from the absolute pressure in the pipe is calculated, and after calculating the differential pressure, the pressure in the cylinder detected by the in-cylinder pressure detecting means is corrected by the atmospheric pressure by the differential pressure to obtain a final in-cylinder pressure detection value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder pressure detecting device for detecting a pressure in a cylinder of an engine.

[0002]

2. Description of the Related Art It is known to use an in-cylinder pressure sensor for detecting a combustion pressure in a cylinder of an engine, that is, an in-cylinder pressure in order to grasp an operating state of the engine. The in-cylinder pressure sensor usually includes a ring-shaped piezoelectric element as shown in, for example, JP-A-8-50072.
The piezoelectric element is sandwiched between the ignition plug mounting seat surface of the cylinder head and the ignition plug washer, and the ignition plug is screwed and fixed to the cylinder head to be crimped and fixed.

An in-cylinder pressure sensor is provided for each cylinder, generates a signal corresponding to the in-cylinder pressure for each cylinder, and each signal is supplied to an engine control circuit to control the engine control such as a fuel injection amount and an ignition timing. Therefore, it is used as a parameter indicating the engine operating state.

[0004]

However, since the in-cylinder pressure sensor detects the in-cylinder pressure under the atmospheric pressure of the engine environment, if the atmospheric pressure changes, the detected in-cylinder pressure naturally changes. However, an output data map for engine control such as a fuel injection amount using the in-cylinder pressure as an engine parameter is prepared in advance based on the in-cylinder pressure as an absolute pressure or the in-cylinder pressure under a reference atmospheric pressure. Considered normal.
Therefore, it is desired to detect the in-cylinder pressure in consideration of the atmospheric pressure fluctuation.

Accordingly, an object of the present invention is to provide an in-cylinder pressure detecting device capable of detecting an in-cylinder pressure suitable for engine control with high accuracy even if there is a change in atmospheric pressure.

[0006]

An in-cylinder pressure detecting device according to the present invention comprises: an in-cylinder pressure detecting means for detecting a pressure in a cylinder of an engine; an intake pipe internal pressure detecting means for detecting an absolute pressure in an intake pipe of the engine; The pressure in the cylinder detected by the in-cylinder pressure detecting means and the absolute pressure in the intake pipe detected by the in-pipe pressure detecting means in a predetermined crank angle range in which the pressure in the cylinder is assumed to take a pressure value close to the atmospheric pressure. Pressure difference calculating means for calculating a pressure difference from the pressure, and correcting means for correcting the pressure in the cylinder detected by the in-cylinder pressure detecting means by the differential pressure to obtain a final in-cylinder pressure detection value. I have.

That is, according to the present invention, the in-cylinder pressure detected by the in-cylinder pressure detecting means in a predetermined crank angle range in which the in-cylinder pressure is assumed to take a pressure value close to the atmospheric pressure is set as a reference in-cylinder pressure. Calculating the differential pressure between the reference cylinder pressure and the absolute pressure in the intake pipe detected by the intake pipe pressure detection means within a predetermined crank angle range, and correcting the subsequently detected cylinder pressure by the differential pressure. As a result, the final in-cylinder pressure detection value subjected to the atmospheric pressure correction can be obtained.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an in-vehicle engine control device to which the in-cylinder pressure detection device according to the present invention is applied. In this engine control device, an intake pipe internal pressure sensor 3 is provided downstream of a throttle valve 2 of an intake pipe 1 of an internal combustion engine.
Is provided. The intake pipe pressure sensor 3 detects the absolute pressure P _BA in the intake pipe.

An injector 4 is provided near the intake port of each cylinder (four cylinders in this embodiment) of the engine body 7. The injector 4 is driven by an ECU (engine control unit) 5 and injects fuel for the driven time. Note that only one cylinder is shown in FIG. Each cylinder of the engine body 7 is provided with an in-cylinder pressure sensor 6 for detecting the pressure in the cylinder as a relative pressure with respect to the atmospheric pressure. Each in-cylinder pressure sensor 6 for each cylinder is shown in FIG.
As shown in the figure, a sensor element portion 6a made of a piezoelectric element,
An amplification unit 6b for integrating (or averaging) and amplifying the voltage generated from the sensor element unit 6a.

As shown in FIG. 2, an ignition plug 13 is screwed and fixed in a screw hole 12 of each cylinder head 11 of the engine body. Washer 13
The sensor element portion 6a of the in-cylinder pressure sensor 6 is sandwiched together with the washer 15 and fixed by pressure. ECU
5 is a CPU 31, ROM 32, RA
M33, A / D converter 34, actuator drive circuit 3
5 and counters 36 and 37, which are connected to each other by a common bus. A plurality of sensors are connected to the A / D converter 34, and an actuator such as an ignition device 41 is connected to the drive circuit 35 in addition to the injector 4. Although omitted in the figure, the injector 4 and the ignition device 41 are provided for each cylinder. A
As a sensor as operating state detecting means connected to the / D converter 34, in addition to the intake pipe pressure sensor 3 and the in-cylinder pressure sensor 6, a cooling water temperature sensor for detecting a cooling water temperature T _W of the internal combustion engine. 42. There is an engine parameter sensor such as a throttle opening sensor (not shown) for detecting the opening of the throttle valve 2. Each time the crankshaft 8 rotates once, the A / D converter 34 converts the analog output voltage of each sensor into a digital value in a predetermined order, outputs the digital value for each sensor, and repeatedly updates the digital value. The counters 36 and 37 are supplied with crank pulses synchronized with each rotation of the crankshaft 8 from the crank angle sensor 38. The counter 36 measures the generation interval of the crank pulse output from the crank angle sensor 38 by counting the number of clock pulses generated, and generates a signal indicating the engine speed Ne. The crank angle sensor 38 has a reference position signal indicating a time point when the rotation angle of the crankshaft 8 is at a predetermined angle position, and a TDC indicating the time point of the top dead center of the piston of each cylinder.
And the signals are supplied to the CPU 31 together with the crank pulse. The reference position signal is supplied to a counter 37, and the counter 37 is reset according to the reference position signal and counts pulses output from the crank angle sensor 38, and the counted value indicates the crank angle θ.

The CPU 31 of the ECU 5 operates in accordance with a program stored in the ROM 32 in advance, reads output values of the plurality of sensors via the A / D converter 34, and
A signal for driving the actuators such as the injector 4 and the ignition device 41 is stored in the AM 33 and is supplied to the drive circuit 35 in accordance with the output values of the sensors. In using the in-cylinder pressure Pi for engine control, the CPU 31 repeatedly performs the in-cylinder pressure differential pressure calculating operation and the in-cylinder pressure correcting operation in synchronization with the crank pulse. The in-cylinder pressure differential pressure calculating operation and the in-cylinder pressure correcting operation are performed for each cylinder. However, since the in-cylinder pressure differential pressure calculating operation and the in-cylinder pressure correcting operation are the same for all cylinders, the cylinder pressure for one cylinder is used here. An internal pressure differential pressure calculation operation and an in-cylinder pressure correction operation are shown.

The CPU 31 calculates the in-cylinder pressure differential pressure.
As shown in FIG. 4, first, the crank angle θ output from the counter 37 is read (step S1), and it is determined whether or not the crank angle θ falls within a predetermined angle range θ _{0 to} θ ₁ . (Step S2). Predetermined angle range θ ₀
Θθ ₁ corresponds to a period during which the in-cylinder pressure does not rise during the exhaust stroke and the intake stroke for each cylinder, that is, a period during which it is estimated to take a pressure value close to the atmospheric pressure. If θ ₀ <θ <θ ₁ is satisfied, the variable n is increased by 1 (step S3),
The current intake pipe absolute pressure P _BA detected by the intake pipe internal pressure sensor 3 is read as P _BA (n) (Step S).
4) The in-cylinder pressure Pi detected by the in-cylinder pressure sensor 6 is read as the reference in-cylinder pressure P ₀ (n) (step S5). The initial value of the variable n is 0. Therefore, steps S1 to S5
By repeating P _BA (1), P _BA (2), P _BA (3),
… And P ₀ (1), P ₀ (2), P ₀ (3),..., The absolute pressure in the intake pipe every time the crankshaft rotates once in the angle range θ ₀ <θ <θ _1. P _BA (n) and the reference in-cylinder pressure P ₀ (n) are obtained and stored in the RAM 33.

In step S2, the CPU 31 determines that θ ₀
If it is determined that <θ <θ ₁ is not satisfied, it is determined whether or not the variable n is greater than 0 (step S6). n
If> 0, since the intake pipe absolute pressure P _BA within the angle range of θ ₀ <θ <θ ₁ has been completely read, the intake pipe absolute pressures P _BA (1) to P _BA (n) calculating an average value P _Bave and the reference cylinder pressure P ₀ of (1) to P ₀ the mean value P _0AVE of (n) by the following equation (step S7, S8).

[0014]

(Equation 1)

When the average values P _BAVE and P _0AVE are calculated, the differential pressure ΔP between the average values P _BAVE and P _0AVE is calculated (step S9), and the pressure difference within the angle range θ ₀ <θ <θ ₁ in the next cycle is calculated. In order to read the intake pipe absolute pressure _PBA and the in-cylinder pressure Pi, the variable n is made equal to 0 (step S10). In the in-cylinder pressure correcting operation, as shown in FIG.
The in-cylinder pressure Pi detected by the in-cylinder pressure sensor 6 is used for A / D
The pressure is read from the converter 34 (step S11), and the value obtained by subtracting the differential pressure ΔP from the in-cylinder pressure Pi is set as the in-cylinder pressure Pi (final in-cylinder pressure detection value) corrected for atmospheric pressure (step S1).
2).

The average value P _0AVE of the reference cylinder pressure P ₀ , which is the reference value of the cylinder pressure Pi detected by the cylinder pressure sensor 6 within the crank angle range θ ₀ <θ <θ ₁ , is _equal to the intake pipe absolute pressure P.
If it is lower than the average value P _{BAVE of BA} (1) to P _BA (n), then if the in-cylinder pressure Pi changes as shown by the solid line A in FIG. Value P _0AVE
Is forcibly made equal to the average value P _BAVE , the detected in-cylinder pressure Pi is corrected upward by ΔP as shown by the broken line characteristic B. Further, θ ₀ <θ <θ ₁ of the crank angle range within the mean value P _{0AV E} of the reference cylinder pressure P ₀ of the in-cylinder pressure Pi detected by the cylinder pressure sensor 6 is the intake pipe absolute at pressure P _BA (1) ~P _BA (n)
Mean value is higher than the P _Bave is then if the cylinder pressure Pi which changes as indicated by a solid line C in FIG. 7 is detected by the cylinder pressure sensor 6, to force the average value P _0AVE average value P _Since it is made equal to _BAVE , the detected in-cylinder pressure Pi is corrected downward by ΔP as shown by the broken line D. The in-cylinder pressure Pi obtained by correcting the atmospheric pressure in this way is used for engine control as a final in-cylinder pressure detection value.

In the above embodiment, θ ₀ <
Average value P of intake pipe absolute pressure P _BA within the angle range θ <θ ₁
The average value P _0AVE of the _BAVE and the reference in-cylinder pressures P ₀ (1) to P ₀ (n) was calculated, but θ ₀ <θ <θ ₁ without calculating such an average value.
It is also possible to simply read the intake pipe absolute pressure _PBA and the cylinder pressure Pi within the angle range of and to set the differential pressure to ΔP. In the above embodiment, the in-cylinder pressure sensor 6 corresponds to the in-cylinder pressure detecting means, the intake pipe internal pressure sensor 3 corresponds to the intake pipe internal pressure detecting means, and the CPU 31 performs the in-cylinder pressure differential pressure calculating operation. The CPU 31 performs an in-cylinder pressure correcting operation, which corresponds to a correcting unit.

[0018]

As described above, according to the present invention, the pressure in the cylinder detected in a predetermined crank angle range in which the pressure in the cylinder assumes a pressure value close to the atmospheric pressure and the absolute pressure in the intake pipe are determined. After calculating the differential pressure from the pressure, the detected pressure in the cylinder is corrected by the atmospheric pressure by the differential pressure to obtain the final detected value of the cylinder pressure. Therefore, since the final cylinder pressure detection value obtained in this way is a value in consideration of the atmospheric pressure, appropriate engine control can be performed by using the final cylinder pressure detection value for engine control.

[Brief description of the drawings]

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

FIG. 2 is a view showing attachment of a sensor element of an in-cylinder pressure sensor.

FIG. 3 is a block diagram showing a configuration of an ECU of the apparatus shown in FIG.

FIG. 4 is a flowchart showing an in-cylinder pressure differential pressure calculation operation by a CPU in an ECU.

FIG. 5 is a flowchart showing an in-cylinder pressure correcting operation by a CPU in an ECU.

FIG. 6 shows that the average value P _0AVE of the reference cylinder pressure P ₀ is the average value P _BAVE.
It is a figure which shows the in-cylinder pressure correction operation | movement in case it is lower.

FIG. 7: Average value P _0AVE of reference cylinder pressure P ₀ is average value P _BAVE
It is a figure which shows the in-cylinder pressure correction operation | movement in case of being higher.

[Description of Signs of Main Parts]

 Reference Signs List 1 intake pipe 2 throttle valve 3 intake pipe internal pressure sensor 4 injector 5 ECU 6 cylinder internal pressure sensor 7 engine body 8 crankshaft 38 crank angle sensor 42 cooling water temperature sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunori Sawamura 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Hironao Fukuchi 1-4-1 Chuo, Wako-shi, Saitama (72) Inventor Hideyuki Oki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Research Institute Co., Ltd. (72) Inventor Hiroaki Kato 1-4-1 Chuo, Wako-shi, Saitama Company Honda R & D Center

Claims (2)

[Claims] 1. An in-cylinder pressure detecting means for detecting a pressure in a cylinder of an engine, an in-pipe internal pressure detecting means for detecting an absolute pressure in an intake pipe of the engine, and a pressure value in which the pressure in the cylinder is close to the atmospheric pressure. Calculating a differential pressure between a pressure in the cylinder detected by the cylinder pressure detecting means and an absolute pressure in the intake pipe detected by the intake pipe pressure detecting means in a predetermined crank angle range estimated to be taken; In-cylinder pressure detection, comprising: differential pressure calculation means; and correction means for correcting the pressure in the cylinder detected by the in-cylinder pressure detection means by the differential pressure to obtain a final in-cylinder pressure detection value. apparatus. 2. The pressure difference calculating means includes: an average value of the pressure in the cylinder detected by the in-cylinder pressure detection means in the predetermined crank angle range; and an internal pressure of the intake pipe detected by the intake pipe internal pressure detection means. 2. The in-cylinder pressure detecting device according to claim 1, wherein a difference from an average value of the absolute pressure is calculated as the differential pressure.