JP2578247B2 - Misfire detection device for internal combustion engines for vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device that detects a misfire of an internal combustion engine from a minute change in the angular velocity of a crankshaft, and more particularly to a misfire detection device of a vehicular internal combustion engine.

2. Description of the Related Art When a misfire occurs in an internal combustion engine, unburned air-fuel mixture is discharged as it is, which not only causes an increase in harmful components in the exhaust gas, but also causes a decrease in output and a decrease in engine stability. Invite.
Therefore, it is easy to determine whether a misfire has occurred in recent years.
For example, there is a demand for a misfire detection device that detects a fire in a normal operation state.

As one of the misfire detection techniques, it has been considered to detect a minute change in the angular velocity of the crankshaft due to the misfire using, for example, an electromagnetic pickup or the like. For example, JP-A-57
Japanese Patent Application Laid-Open No. 188748 discloses that a rotating plate having a projection piece is fixed to a crankshaft at every crank angle of 180 °, and proximity switches are provided at two positions having phases different by 90 °, and the speed difference at two positions different by 90 ° is provided. 1 shows an apparatus for detecting the presence or absence of a misfire. More specifically, the difference between the times required for one of the protrusions to pass through an angle near each proximity switch is compared with a certain value, and when the time difference becomes smaller than a certain value, a misfire has occurred. Is determined.

However, in the conventional example described above, the presence or absence of a misfire can be detected only during the idling operation in which the internal combustion engine is normally rotating and disconnected from the power transmission system such as the transmission. That is, in a state where the engine is mechanically connected to the power transmission system, the decrease in energy due to the misfire is affected by fluctuations in the kinetic energy held by the vehicle, and does not accurately appear as fluctuations in the angular speed of the crankshaft. In particular, if the speed reduction ratio of the power transmission system is different, the degree of the effect changes,
In a vehicular internal combustion engine in which the reduction ratio greatly changes, it is substantially difficult to detect misfire.

As shown in FIG. 1, a misfire detecting apparatus for a vehicle internal combustion engine according to the present invention measures a time required for a crankshaft to rotate a predetermined angle from a predetermined crank position.
An internal combustion engine for a vehicle, comprising: means for detecting a change amount of the required time sequentially measured; and means for performing a misfire determination of the internal combustion engine by comparing the change amount with a predetermined misfire determination value. Wherein the means for correcting the misfire determination value is provided in accordance with the speed reduction ratio of the vehicle.

The change in the angular velocity of the crankshaft is measured in a predetermined cycle of the time required for the crankshaft to rotate from a predetermined crank angle position by a predetermined angle, and is captured by the amount of change. Then, by comparing the amount of change with a predetermined misfire determination value, it is determined whether or not a misfire has occurred in the engine. The misfire determination value is set by, for example, correcting a reference value in consideration of a fuel injection amount or the like in accordance with a vehicle reduction ratio.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory view showing a mechanical structure of one embodiment of the present invention, wherein 11 is an internal combustion engine, 12 is an intake passage, and 13 is an exhaust passage. In this embodiment, a 4-cycle in-line 6-cylinder internal combustion engine will be described as an example.

In the intake passage 12, a fuel injection valve 14 for supplying fuel toward each intake port is provided for each cylinder, and a throttle valve 15 is interposed.The throttle valve 15 is provided upstream of the throttle valve 15. ,
For example, a hot wire type air flow meter for detecting the intake air amount Q
Sixteen are arranged. The throttle valve 15 is provided with a throttle valve opening sensor 17 for detecting the opening TVO.

 Reference numeral 18 denotes a vehicle speed sensor that detects a vehicle speed VSP.

Reference numeral 19 denotes a crank angle sensor provided at the end of the camshaft, inside the distributor, or the like to detect the engine speed Ne and the crank angle position. The crank angle sensor 19 includes a pulse signal (REF signal) for detecting a reference position of each cylinder, for example, a top dead center position, and a unit crank angle (for example, 2 °) for detecting a rotation angle from the reference position. And a pulse signal (POS signal) for each CA). The REF signal is output at every 120 ° CA for a six-cylinder engine, and is output at a predetermined angle before the top dead center of each cylinder. More specifically, the pulse width of the pulse corresponding to each cylinder is different, which makes it possible to detect the compression top dead center position of the # 1 cylinder and thereby determine the cylinder of each cylinder (FIG. 3 ( a)). Therefore, in this embodiment, the REF signal is used as the reference position detection signal of the crankshaft 20.

On the other hand, a ring gear 21 that can mesh with a starter motor (not shown) is attached to the rear end of the crankshaft 20 together with a flywheel. The teeth of the ring gear 21 are formed at equal intervals, for example, every 6 CA. A ring gear sensor 22 including an electromagnetic pickup or the like is provided near the ring gear 21. The ring gear sensor 22 forms an ON-OFF pulse signal and outputs an AC current generated by the passage of the teeth of the ring gear 21, thereby obtaining a pulse train as shown in FIG. 3 (b). Can be Although the crank angle sensor 19 can be provided for the camshaft or the like, it is difficult to detect the angular velocity fluctuation due to misfiring from the POS signal because the accuracy of the POS signal is affected by the backlash of the valve train. It is. In contrast, the ring gear sensor 22
Detects the rotational speed of the ring gear 21 directly connected to the crankshaft 20, so that it is possible to reliably detect fluctuations in angular velocity.

The control unit 23 to which the detection signals of the above-described sensors are input uses a so-called microcomputer system, and performs the air-fuel ratio control by the fuel injection valve 14, the ignition timing control of an ignition system (not shown), and the like. Based on the detection signal of the ring gear sensor 22, a misfire determination, which will be described later, is performed.If a predetermined misfire is detected, a failure code corresponding to the predetermined misfire is stored, and alarm means such as an alarm lamp 24 is activated. It has become. Further, the failure code can be read by external means.

 Next, the misfire detection operation of the above embodiment will be described.

First, the detection of the angular velocity of each cylinder will be described with reference to FIG. 3. As shown in FIG.
After detecting the REF signal output every time, the ring gear sensor 22
Is started, and when a predetermined number of teeth, for example, P teeth are detected, the control unit 23
A first trigger as shown in FIG. 4C is output by a preset counter (not shown). Furthermore, from now on
When the number of teeth is detected, a preset counter (not shown) outputs a second trigger as shown in FIG. That is, during this time, the crankshaft 20 rotates by the crank angle corresponding to the number of m teeth. The timer in the control unit 23 measures the required time T during the period from the first trigger to the second trigger.

The measurement of the required time T is repeatedly performed every time the REF signal is output, that is, every 120 ° CA. Then, the latest data as T _1, the previous data as T _2, is stored in the form of sequentially updates, based on the difference between the two, it is made as misfire determination as described below.

The phase for measuring the required time T should, of course, be set by selecting a period in which the angular velocity fluctuation due to misfire appears most remarkably. By focusing only on the phase within a certain range, there is no influence on the other periods even if there is an angular velocity fluctuation due to friction or the like.

Next, FIG. 4 is a main flowchart showing a specific processing flow in the control unit 23.
First, the required time T is measured as described above (step S
1).

Subsequently, the count value CNT is incremented (step S2), and it is determined whether or not the count value CNT exceeds a predetermined value CCNT (step S2). One misfire as described later
It is not determined that misfire has occurred just by being detected twice,
When a misfire is detected at a predetermined frequency or more within a predetermined period, it is determined that a misfire has occurred.
The period is detected by comparing T with a predetermined value CCNT.

When the count value CNT exceeds the predetermined value CCNT, the count value CNT and the misfire detection frequency CNG (n) of each cylinder described later are reset to “0” (step S4), and when the count value CNT is less than the predetermined value CCNT, the process proceeds to step S5. move on.

In a step S5 calculates the time difference ΔT required time T ₁ measured time and duration T ₂ of the last measurement for each cylinder (step S5).

Next, each variable KT _P for setting the misfire determination value JDT,
K _GP and _KT are sequentially obtained (steps S6 to S8). Variable KT _P is set in proportion to the fuel injection quantity T _P as shown in FIG. 5 (computed based on the intake air amount Q / engine speed Ne), the variable K _GP
Is the reduction ratio GP (vehicle speed VSP / engine speed Ne) as shown in FIG.
), And the variable _KT is set in proportion to the cube of the required time T as shown in FIG. In addition,
Each variable KT _P, K _GP, K _T is previously stored in each memory as the values T _P, GP, T map data.

Here, we describe the reason for setting the variables KT _P, K _GP, the K _T as described above. Considering first the kinetic energy E _T when the vehicle is traveling at a constant speed is as follows.

E _T = E _C + E _R (1) where E _C is running energy and E _R is rotational energy. The running energy E _C is expressed by the following equation.

However, v is the vehicle speed (VSP), D is diameter of a tire, r is the reduction ratio (GP), the r _M transmission section reduction ratio, the r _D is final reduction ratio. The rotational energy E _R is represented by the following equation.

_{However, C 1, C 2, C} 3 are predetermined constants, I _e is the rotation inertia moment at the duty post extending from the engine to the transmission, I _t is the rotational moment of inertia at the duty post leading to final reduction unit from the transmission, I _d is the rotational moment of inertia from the final deceleration section to the tire. Then, the constant parts in the second and third expressions are replaced with constants A and B as follows, When the second and third equations are substituted into the first equation, the above kinetic energy E _T is expressed by the following equation.

E _T = (A + B) · _Ne ² = C · _Ne ² (6) where C = A + B. Now, the variation ΔE of the kinetic energy E _T in a predetermined period can be shown by the following equation.

ΔE = C (N _e2 ² −N _e1 ² ) (7) where _{Ne 1} is the current engine speed and _{Ne 2} is the engine speed before a predetermined period.

On the other hand, the kinetic energy ΔE _f lost due to a change in the fuel injection amount T _p or misfire is represented by the following equation, where T _{f is} the resistance torque and θ is the crank angle (range) receiving the resistance torque T _f .

ΔE _f = T _f · θ (8) Then, if ΔE = ΔE _f , the following equation is established.

_{T f · θ = C (N} e2 2 -N e1 2) ...... (9) Further, the engine speed N _e, when the crank angle for measuring the required time T (range) and theta _x, the following equation expressed.

However, m ₁ is a predetermined constant.

Next, when the tenth equation is substituted into the ninth equation, the following equation is obtained.

However, the required time T ₁ is measured this time, as described above, T ₂
Is the required time measured last time.

Then, when this is solved for the time difference ΔT = T ₂ −T ₁ ,
It becomes like the following formula.

Here, m ₂ is a predetermined constant.

Thus, the time difference ΔT is proportional to the fuel injection quantity T _P, inversely proportional to the reduction ratio GP (the C in the 12 formula is the sum of the fourth expression of the A and the fifth formula of B, a function of reduction ratio GP ), Required time T
Is considered to be proportional to the third power of the above variables KT _P , K _GP , K _T
Is explained.

Each variable KT _P as described above, K _GP, when K _T is obtained, performs the following calculation, to set a misfire determination value JDT (step S9).

_{JDT = KT P · K GP ·} K T ...... (13) Next, the time difference ΔT calculated in step S5 described above to determine whether it exceeds the misfire judgment value JDT (step S1
0). This determination is made for each cylinder.

If the time difference ΔT exceeds the misfire determination value JDT, the misfire detection circuit CNG (n) of the cylinder is incremented (step S11), and the misfire detection circuit CNG (n) of each cylinder is incremented.
Is greater than or equal to a predetermined value JC (step S1).
2). Here, as described above, until the count value CNT exceeds the predetermined value CCNT, the time difference ΔT is equal to the misfire determination value JDT.
If the number of misfires exceeds the predetermined value JC, the misfire detection circuit CNG (n) is incremented to determine whether the misfire frequency is equal to or higher than a predetermined frequency. It is determined that a misfire has occurred at a predetermined frequency or higher, and the misfire determination flag FLGMF (n) of the corresponding cylinder is set to "1" (step S13). The misfire determination flag FLGMF
When (n) becomes "1", as described above, the alarm lamp 24
Lights up.

As described above, in this embodiment, the angular speed variation of the crankshaft 20 the ring gear 21 measures the required time T required for a predetermined angular rotation from a predetermined reference position, a required time measured this time and duration T ₂ of the last measurement The time difference ΔT from T ₁ is obtained,
The time difference ΔT is compared with the misfire determination value JDT, and the time difference ΔT
If exceeds the misfire determination value JDT, it is determined that a misfire has occurred. Misfire determination value JDT is variable KT _P be set in proportion to the fuel injection quantity T _P, variables to be set in inverse proportion to the reduction ratio GP
K _GP , a variable K _T set in proportion to the cube of the required time _T
Set based on Therefore, not only during idling, but also when the angular speed of the crankshaft fluctuates due to factors other than misfire during driving, etc., the misfire determination value JD
Since T is set, accurate misfire determination can always be performed.

In the above-described embodiment, the speed reduction ratio GP has been calculated from the vehicle speed VSP and the engine rotational speed N _e, a sensor for detecting the position of the speed change gear is provided, on its detection position as shown in FIG. 8 it may set the variable K _GP accordingly.

Effect of the Invention As is clear from the above description, according to the misfire detection device for a vehicle internal combustion engine according to the present invention, the misfire determination value is corrected in accordance with the speed reduction ratio, so that the speed reduction ratio changes during traveling operation. In such a case, misfire detection can be performed accurately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a claim correspondence diagram showing the configuration of the present invention, FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the present invention, and FIG. 3 explains the operation of this embodiment. Time chart for the fourth
Figure is a flow chart for explaining the operation of this embodiment, Figure 5 is a graph showing the relationship between the fuel injection quantity T _P and variables KT _P, graph Figure 6 is showing the relationship between the reduction ratio GP and variables K _GP,
7 graph figure showing the relationship between the required time T and the variables K _T, 8
Figure is a graph showing a relationship between gear position and variables K _GP relating to another embodiment of the present invention. 1 required time measuring means 2 required time change amount detecting means 3 misfire determination means 4 misfire correction means 23
control unit.

Continuation of the front page (56) References JP-A-62-118031 (JP, A) JP-A-57-188748 (JP, A) JP-A-2-49955 (JP, A) JP-A-2-112646 (JP) JP-A-2-26853 (JP, A) JP-A-3-206337 (JP, A) JP-A-3-249359 (JP, A)

Claims (1)

(57) [Claims] A means for measuring a time required for the crankshaft to rotate from a predetermined crank angle position by a predetermined angle; a means for detecting an amount of change in the required time which is sequentially measured; A misfire detection device for a vehicular internal combustion engine, comprising: means for performing misfire determination of the internal combustion engine by comparing the misfire determination value with a determination value; wherein a means for correcting the misfire determination value according to a vehicle reduction ratio is provided. Misfire detecting device for a vehicular internal combustion engine.