Method and device for detecting misfiring cylinder of reciprocating internal-combustion engine using torsional vibration signal

Abstract

A method for detecting a misfiring cylinder is characterized by: performing frequency analysis on a torsional vibration signal from an internal-combustion engine system to extract an amplitude and a phase of a fundamental frequency component; comparing the amplitude of the fundamental frequency component with the amplitude of the torsional vibration signal to determine whether misfiring has occurred; calculating, when the misfiring is determined to occur, an explosion angle of a misfiring cylinder by using crank angle displacement at which the fundamental frequency component has a maximum value, and a phase of a fundamental frequency component with excitation force; and comparing the calculated explosion angle with an explosion angle of explosion order to detect the position of the misfiring cylinder.

Claims

1. A misfire detection apparatus for a reciprocating internal-combustion engine, comprising: a torsional vibration sensor arranged at a shaft line of the engine for detecting rotational speed fluctuations, the torsional vibration sensor outputting a torsional vibration signal; a camshaft position sensor, optionally included for a 4-stroke engine, arranged at a camshaft of the engine for detecting a reference signal indicative of a top dead center of a reference cylinder, the camshaft positon sensor outputting a camshaft position signal; a signal processing unit configured to obtain amplitudes and phases of a fundamental frequency component and harmonic components by performing a Fast Fourier Transform (FFT) on the torsional vibration signal; an application processing unit configured to detect a misfiring event and determine a misfiring cylinder position by; detecting the misfiring event when the amplitude of the fundamental frequency component exceeds a preset threshold; and identifying the misfiring cylinder position by calculating an explosion angle (FA.sub.i) of the misfiring cylinder according to the relation;
FA.sub.i=ixmax.Math.dx(1/k)(3/2(k)), wherein ixmax.Math.dx is a crank-angle value obtained by multiplying ixmax, an index corresponding to a sample at which the amplitude of the fundamental frequency component of the torsional vibration signal reaches a maximum while a fundamental frequency component of the excitation force attains a minimum having a phase angle (k), by dx, a fixed crank-angle increment between successive torsional vibration signal samples; wherein (k) is calculated from torque harmonic coefficients and an explosion order supplied by an engine manufacturer; wherein, k is 1.0 for a 2-stroke engine and 0.5 for a 4-stroke engine; and wherein, for the 4-stroke engine, a crank-angle reference is synchronized to the top dead center of a reference cylinder using the camshaft position signal; a transmission unit connected the application processing unit and configured to transmit the result of the detected misfiring cylinder; and a display device configured to receive and display the detected misfiring cylinder.

2. A method for detecting a misfiring cylinder in a reciprocating internal combustion engine, the engine having a crankshaft and a camshaft, the method comprising: sensing torsional vibration of the crankshaft during engine operation using a vibration sensor and producing a torsional vibration signal reflecting instantaneous crankshaft speed fluctuations; receiving a camshaft position signal from a camshaft sensor, the camshaft position signal indicating a reference crank-angle position corresponding to a top dead center (TDC) of a reference cylinder in the engine cycle; performing a Fast Fourier Transform (FFT) on the torsional vibration signal to obtain a fundamental frequency component of the torsional vibration; determining a misfire when the amplitude of the fundamental frequency component exceeds a preset threshold; and identifying the misfiring cylinder by calculating an explosion angle (FA.sub.i) of the misfiring cylinder using the fundamental frequency component of the torsional vibration signal and an excitation force function, according to the relation:
FA.sub.i=ixmax.Math.dx(1/k)(3/2(k)), wherein ixmax.Math.dx is a crank-angle value obtained by multiplying ixmax, an index corresponding to a sample at which the amplitude of the fundamental frequency component of the torsional vibration signal reaches a maximum while a fundamental frequency component of the excitation force attains a minimum having a phase angle (k), by dx, a fixed crank-angle increment between successive torsional vibration signal samples; wherein (k) is calculated from torque harmonic coefficients and an explosion order supplied by an engine manufacturer; wherein k is 1.0 for a 2-stroke engine and 0.5 for a 4-stroke engine; and wherein, for the 4-stroke engine, a crank-angle reference is synchronized to the top dead center of a reference cylinder using the camshaft position signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram illustrating method and apparatus for detecting a misfiring cylinder of an internal combustion engine according to the present invention.

(2) FIG. 2 is a mass-spring model of a 4-stroke inline internal combustion engine generator for numerical analysis simulation of torsional vibration.

(3) FIG. 3 is a graph of torsional vibration excitation force and vibration response of a 4-stroke inline internal combustion engine generator during normal firing.

(4) FIG. 4 is a graph of torsional vibration excitation force of the 4-stroke inline internal combustion engine generator during misfiring.

(5) FIG. 5 is a graph of torsional vibration response of a 4-stroke inline internal combustion engine generator during misfiring.

(6) FIG. 6 is a graph of torsional vibration response according to a change in torsional vibration measurement position when misfiring of a specific cylinder (J4, Misfiring Cyl. #3) in FIG. 2 occurs.

(7) FIG. 7 is a graph of torsional vibration excitation force of a 2-stroke inline internal combustion engine propulsion shaft during misfiring.

(8) FIG. 8 is a graph of torsional vibration response of the 2-stroke inline internal combustion engine propulsion shaft during misfiring.

(9) FIG. 9 is a graph of torsional vibration excitation force of a 4-stroke V-type internal combustion engine generator during misfiring.

(10) FIG. 10 is a graph of torsional vibration response of the 4-stroke V-type internal combustion engine generator during misfiring.

BEST MODE

(11) A misfiring cylinder detection method for a reciprocating internal-combustion engine using a torsional vibration signal includes: calculating an amplitude X0(k) and a phase (k) of a fundamental frequency component by frequency analysis of the torsional vibration signal x(t), in detecting the misfiring cylinder using the torsional vibration signal of the reciprocating internal-combustion engine system; comparing the amplitude X.sub.0(k) of the fundamental frequency component with the amplitude of the torsional vibration signal x(t) to determine whether the misfiring has occurred; calculating, when the misfiring is determined to occur, a crank angle i.sub.xmaxdx having a maximum value of the fundamental frequency component defined as in [Equation 1] below with a top dead center of a reference cylinder as an origin of crank angle displacement; calculating an explosion angle FA.sub.i of the misfiring cylinder defined as in [Equation 2] below using the crank angle i.sub.xmaxdx having the maximum value and an excitation force phase (k) of the fundamental frequency component derived by the calculation of the excitation force of the internal combustion engine system; and comparing the calculated explosion angle FA.sub.i with the explosion angle of an explosion order to specify the position of the misfiring cylinder.

MODE FOR INVENTION

(12) For a reciprocating internal-combustion engine system in Table 1, numerical analysis simulation of torsional vibration is performed, and torsional vibration excitation force and torsional vibration response are obtained. Since the torsional vibration excitation force and torsional vibration response, which are simulation results, correspond to the excitation force and response of the actual internal combustion engine system, the torsional vibration response is assumed to be the torsional vibration signal x(t) measured in the actual system, and the method of the present invention detects whether misfiring has occurred and the misfiring cylinder.

(13) Hereinafter, a misfiring cylinder detection method and device using a torsional vibration signal according to the present invention will be described with reference to the proposed Equation and accompanying drawings.

(14) FIGS. 4 and 5 illustrate torsional vibration excitation force and vibration response during misfiring of each cylinder in Case 1 of 4-stroke inline internal combustion engine generator in Table 1. In FIG. 5, a torsional vibration synthesis response (Synth) graph is a torsional vibration signal x(t) detected by the torsional vibration detection unit 3 in FIG. 1, and the signal processing unit 4 extracts an amplitude X.sub.0(k) and a phase (k) of a fundamental frequency component through frequency analysis, and obtains the fundamental frequency component (0.5 order) graph in FIG. 5.

(15) The application processing unit 5 in FIG. 1 determines that the misfiring cylinder has occurred when the amplitude X.sub.0(k) of the fundamental frequency component (0.5 order) in FIG. 5 is greater than a certain level compared to the synthesized amplitude (Synth). When it is determined that the misfiring has occurred, for the 4-stroke internal combustion engine system, as additionally illustrated in FIG. 5, when the current rotational speed pulse signal used for frequency analysis is a pulse signal that coincides with a camshaft position sensor pulse signal, a preceding pulse signal, which is the current rotational speed pulse, is identified as a pulse indicating a top dead center of a reference cylinder, otherwise a following pulse is identified as a pulse indicating the top dead center of the reference cylinder, and the top dead center of the identified reference cylinder is corrected to an origin of crank angle displacement to recalculate the phase (k) of the fundamental frequency component (0.5 order) and a crank angle i.sub.xmaxdx at a maximum value.

(16) As illustrated in FIG. 5, for each cylinder misfiring, according to Equation 1, the crank angle i.sub.xmaxdx, in which the fundamental frequency component of the torsional vibration signal has the maximum value, is obtained as i.sub.xmaxdx=[55-167.5-290-420-550-667.5]. The angle displacement at which the fundamental frequency component with the excitation force is minimized when the misfiring of the reference cylinder (usually cylinder No. 1) obtained by the provided or known method occurs, is i.sub.Fmindx=62.5 as illustrated in FIG. 4, so a phase in an expression of a sine function of the fundamental frequency component F.sub.k(t) with excitation force is calculated as (k)=238.75.

(17) Now, by substituting the phase of the fundamental frequency component with excitation force, (k)=238.75, the crank angle with the maximum vibration response, i.sub.xmaxdx=[55-167.5-290-420-550-667.5] into Equation 2, an explosion angle of a firing cylinder that performs an explosion stroke, FA.sub.i=[7.5, 105, 227.5, 357.5, 487.5, 605] can be found at the position where the vibration response has the maximum value. Comparing this with explosion angles [0, 120, 240, 360, 480, 600] according to the explosion order in Table 1, it can be seen that the position of the misfiring cylinder is accurately specified.

(18) In the same way, in Case 2 of a 2-stroke inline propulsion shafting system in Table 1, as illustrated in FIG. 8, since the maximum value of the fundamental frequency component of the torsional vibration signal during misfiring is i.sub.xmaxdx=[10, 60, 115, 165, 220, 267.5, 322.55], in FIG. 7, the angle displacement at which the fundamental frequency component with excitation force is minimized during misfiring of reference cylinder (Cyl. #1) is i.sub.Findx=25, the phase of the fundamental frequency component with excitation force is (k)=245, by substituting them into Equation 2, the explosion angle of the firing cylinder performing the explosion stroke at the position where the vibration response has the maximum value is calculated as FA.sub.i=[15, 35, 90, 140, 195, 242.5, 297.5]. Comparing this with the explosion angle [0, 51.5, 104.5, 153.1, 208.0, 255.8, 310.2] according to the explosion order in Table 1, it can be seen that the position of the misfiring cylinder is accurately specified.

(19) When the same method is applied to Case 3 of a 4-stroke V-type engine generator in Table 1, since as illustrated in FIG. 10, the crank angle in which the fundamental frequency component of the torsional vibration signal has the maximum value during misfiring is i.sub.maxdx=[70, 152.5, 237.5, 320, 405, 500, 600, 697.5], and as illustrated in FIG. 9, the angle displacement at which the fundamental frequency component with excitation force is minimized during the misfiring of the reference cylinder (Cyl. #1) is i.sub.Fmindx=60 and the phase of the excitation force of the fundamental frequency component is (k)=240, by substituting them into Equation 2, the explosion angle of the misfiring cylinder is calculated as FA.sub.i=[10, 92.5, 177.5, 260, 345, 440, 540, 637.5]. By comparing this with the explosion angle [0, 90, 180, 270, 360, 450, 540, 630] in Table 1, the position of the misfiring cylinder may be specified.

INDUSTRIAL APPLICABILITY

(20) The present invention relates to a method for detecting a misfiring cylinder, which is one of the main causes of malfunction in an internal combustion engine system such as ships, automobiles, power generation facilities, and petrochemicals, and more particularly, to a method and device for detecting whether a cylinder is misfiring and a position of a misfiring cylinder by frequency analysis of a torsional vibration signal of a reciprocating internal-combustion engine system.

(21) According to the present invention, a misfiring cylinder detection device is configured to include a detection unit (3) for measuring a torsional vibration signal; a signal processing unit (4) for frequency analysis of the measured torsional vibration signal and extracting an amplitude and a phase of a fundamental frequency component; and an application processing unit (5) for determining whether misfiring has occurred using the extracted amplitude and phase and specifying the misfiring cylinder, thereby effectively detecting the misfiring and its position using the torsional vibration signal which is easy to measure. In this way, it is possible to prevent a disaster from being caused by the occurrence of misfiring and reduce time and cost for maintenance, thereby improving the lifetime and performance of internal-combustion engine equipment components, and thus, contribute to the development of industries using the internal combustion engine.

(22) In addition, the present invention has industrial applicability because it has not only sufficient possibility of commercialization or business, but also realistically and clearly practicable.