JP2000161124A - Failure detecting device for variable valve system engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect a failure of an intake air amount sensor for a variable valve system engine provided with intake- and exhaust valves. SOLUTION: This engine is provided with intake and exhaust valves 3, 4 to control the intake air amount and the discharge of exhaust gas of a cylinder by the opening and closing timings of these valves, and is provided with an intake air amount sensor 21 for measuring the intake air amount in an intake passage 5. In this case, an intake air amount estimating means for estimating the actual intake air amount based on the cylinder inside volume when at least the intake valve 3 is closed, a means for comparing the estimated value to the measured value of the intake air amount sensor 21, and a failure judging means for judging a failure in the intake air amount sensor 21 based on the comparison result, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a failure of a variable valve engine having intake and exhaust valves, and more particularly to a device for detecting a failure of an intake air amount sensor for measuring an intake air amount.

[0002]

2. Description of the Related Art There is an engine in which intake and exhaust valves of an engine are driven by an electromagnetic force instead of being driven by a cam. In this device, the mechanism such as a camshaft can be omitted, the valve opening / closing timing can be set in accordance with the operating state of the engine, and the intake air amount of the cylinder and the discharge of exhaust gas can be controlled by the valve opening / closing timing. (Japanese Patent Laid-Open No. 61
-247807).

[0003] Further, there is one that drives intake and exhaust valves by hydraulic pressure (Japanese Patent Application Laid-Open No. 7-317516). This means that oil pressurized by an oil pump is set for each cylinder that supplies and shuts off oil to a hydraulic chamber defined by a piston that drives intake and exhaust valves and a cylinder that slides the piston. The intake valve and the exhaust valve are controlled to a desired valve opening timing and a desired valve closing timing for each cylinder by supplying the same through the supplied electromagnetic spill valve.

As a method for measuring the engine intake air amount in such an engine, an air flow meter (intake air amount sensor) is provided in an intake passage upstream of a throttle valve, and a basic fuel amount is calculated from the intake air amount measured by the intake air amount sensor and the engine speed. In the case where the fuel injection amount is determined and the fuel injection amount of the fuel injection valve is controlled by performing various corrections based on this, if the intake air amount sensor is abnormal, for example, the fuel injection amount can be appropriately controlled. Disappears.

Conventionally, such a failure detection device for an intake air amount sensor detects the presence or absence of a disconnection in a sensor circuit (Japanese Patent Laid-Open No. Hei 10-68647), and detects an intake air amount from a signal of an oxygen concentration sensor provided in an exhaust system. A method for indirectly determining a sensor failure or a failure of an intake air sensor based on a signal waveform of the intake air sensor, that is, a deviation between a maximum output value and a minimum output value of a signal generated by intake pulsation accompanying opening and closing of an intake valve. (JP-A-5-001930).

[0006]

However, an apparatus for detecting the presence or absence of a disconnection in a sensor circuit cannot detect an abnormality due to a deviation in the output of the intake air amount sensor, and determines the failure of the intake air amount sensor from the signal of the oxygen concentration sensor. Are difficult to distinguish from fuel system failures.

[0007] Further, in the case of determining the failure of the intake air amount sensor from the difference between the maximum output value and the minimum output value of the intake air amount sensor, the intake air amount of the cylinder is controlled by the intake and exhaust valves rather than the throttle valve provided in the intake passage. In the case of controlling the intake air pressure and the like, the intake pulsation changes depending on the opening / closing timing of the intake valve, so that it is not necessarily applied.

The present invention focuses on the fact that, in the case of a variable valve engine that controls the intake air amount of a cylinder by the opening and closing timing of intake and exhaust valves, the intake air amount of the cylinder can be estimated by the opening and closing timing. An object of the present invention is to provide a failure detection device that can accurately detect a failure of an intake air amount sensor by comparing an estimated value and a measurement value of an intake air amount sensor.

[0009]

According to a first aspect of the present invention, the intake and exhaust valves are provided, and the intake air amount of the cylinder and the discharge of exhaust gas are controlled by the opening / closing timing of these valves. In a variable valve engine having an intake air amount sensor for measuring an intake air amount sensor, an intake air amount estimating means for estimating an actual intake air amount based on at least a cylinder internal volume at the time of closing the intake valve, A comparison unit that compares the measured values and a failure determination unit that determines a failure of the intake air amount sensor based on the comparison result are provided.

In a second aspect based on the first aspect, the intake air amount estimating means calculates the estimated value of the intake air amount based on the closing timing of the exhaust valve or the opening timing or intake of the intake valve, and the overlap of the exhaust valve. It has correction means for correcting according to the amount.

In a third aspect based on the first aspect, a throttle valve is provided in the intake pipe, and the intake air amount estimating means corrects the estimated value of the intake air amount according to the opening degree of the throttle valve. Has correction means.

In a fourth aspect based on the third aspect, the correction means reduces and corrects the estimated value of the intake air amount as the opening degree of the throttle valve is small and the intake pipe negative pressure is large.

In a fifth aspect based on the first aspect, the failure determination means determines that a difference between the estimated value of the intake air amount by the intake air amount estimation means and the measurement value of the intake air amount sensor is a predetermined value. Is larger than the failure determination reference value, the intake air amount sensor is determined to have failed.

In a sixth aspect based on the first aspect, the failure determination criterion by the failure determination means is set for each engine operating condition including at least the engine speed.

In a seventh aspect based on the first aspect, the intake air amount estimating means determines the intake / exhaust valve opening / closing timing based on the intake / exhaust valve opening / closing control timing.

According to an eighth aspect, in the first aspect, the suction,
A seating sensor for detecting the opening and closing timing of the exhaust valve is provided, and the intake air amount estimating means estimates an actual intake air amount based on a detection value of the intake and opening timing of the exhaust valve by the seating sensor.

According to a ninth aspect, in the first aspect, a display device for displaying a failure of the intake air amount sensor is provided.

[0018]

According to the first and seventh aspects of the invention, it is possible to easily and accurately detect an abnormality due to a deviation in the output of the intake air amount sensor, a failure such as a disconnection of the sensor circuit, and the like.

According to the second aspect, it is possible to obtain an accurate estimated intake air amount with respect to a change due to the closing timing of the exhaust valve, the opening timing of the intake valve, the amount of intake, and the amount of overlap of the exhaust valve.
Failure detection of the intake air amount sensor can be accurately performed.

According to the third and fourth aspects of the present invention, an accurate estimated intake air amount can be obtained even when a throttle valve is provided.
Can respond.

According to the fifth and sixth aspects of the present invention, it is possible to accurately determine the failure of the intake air amount sensor.

According to the eighth aspect, it is possible to accurately detect the failure of the intake and exhaust valves, and to cancel the failure determination of the intake air amount sensor when these failures occur.

According to the ninth aspect, early repair of a failure becomes possible.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, 1 is an engine, 2 is a cylinder (combustion chamber), 3 is an intake valve, 4 is an exhaust valve, 5 is an intake pipe, 6 is an exhaust pipe, 7 is a spark plug, and 8 is fuel. The injection valve 9 is an exhaust gas purifying catalyst.

Electromagnetic actuators 10 and 11 for driving the intake valve 3 and the exhaust valve 4 include two springs 13 and 14 for urging the movable portion 12 in the valve opening direction and the valve closing direction as shown in FIG.
And two electromagnets 15 and 16 for attracting the movable portion 12 in the valve opening direction and the valve closing direction.

When the current of the electromagnetic coil of the electromagnet 15 on the valve opening side is cut off from the state of FIG.
By the spring force of the valve-closing side spring 14, the movable portion 12 passes through the neutral position and approaches the valve-closing-side electromagnet 16, and at this time, the electromagnetic coil of the valve-closing-side electromagnet 16 is energized. The movable portion 12 overcomes the spring force of the valve-opening side spring 13 and is attracted by the valve-closing-side electromagnet 16 to close the valve. Next, when the current of the electromagnetic coil of the electromagnet 16 on the valve-closing side is cut off from this state, the movable portion 1
2 passes through the neutral position, approaches the electromagnet 15 on the valve opening side, and at this time, energizes the electromagnetic coil of the electromagnet 15 on the valve opening side. Is overcome by the spring force of the spring 14 and is attracted by the electromagnet 15 on the valve opening side, and the valve is opened. In addition, both electromagnets 1
When no current flows through the electromagnetic coils 5 and 16,
The movable portion 12 is held at a neutral position (a state in which the intake valve 3 and the exhaust valve 4 are half-opened) separated from the attraction surfaces of the electromagnets 15 and 16 by a predetermined position, respectively, by the spring forces of the springs 13 and 14.

On the other hand, the intake pipe 5 forming a part of the intake passage
Is provided with an air flow meter (intake air amount sensor) 21 for detecting an intake air amount of the engine as a means for detecting an operation condition of the engine, and a signal thereof is input to the control unit 20. As means for detecting the operating conditions of the engine, a rotation speed sensor (crank angle sensor) 22 for detecting an engine speed and a crank angle, an accelerator opening sensor 23 for detecting an accelerator opening, and detecting a cooling water temperature of the engine. A water temperature sensor 24, an intake air temperature sensor 25 for detecting an intake air temperature, and the like are provided. These signals are also input to the control unit 20.

Based on these sensor signals, the control unit 20 controls the opening and closing timing of the intake and exhaust valves 3 and 4 via the drive circuit 17 and controls the fuel injection amount of the fuel injection valve 8 and the like. The failure determination of the intake air amount sensor 21 is performed.

In this case, the opening timing of the intake valve 3 is controlled to be advanced as the engine speed increases with reference to the intake top dead center, for example, and the closing timing is determined based on the accelerator opening, engine speed and the like. The crank angle (intake stroke section, compression stroke section) for obtaining the intake air amount is controlled. Basically, the intake air amount is controlled by the closing timing of the intake valve 3.

The closing control timing (crank angle) of the intake valve 3
Is obtained by searching a close control timing map in which the close control timing of the intake valve 3 is set based on the accelerator opening and the engine speed as shown in FIG. 3, for example. In this closing control timing map,
In the fully open range of the accelerator opening, the crank angle at which the maximum intake amount enters the cylinder is set (adapted by experiments, etc.), and in the partial load range, the crank angle is advanced or retarded with respect to the fully open range to obtain the required intake air. The crank angle is set to obtain the amount. Note that the crank angle at which the maximum amount of intake air enters the cylinder in the fully open region of the accelerator opening is substantially at the piston bottom dead center in the low engine speed region, and is closer to the compression stroke in the high engine speed region.

The opening timing of the exhaust valve 4 is controlled near the bottom dead center of the piston between the expansion stroke and the exhaust stroke, and the closing timing is controlled near the top dead center of the intake according to the engine speed.

The closing control timing (crank angle) of the exhaust valve 4
Is obtained by searching a close control timing map in which the close control timing of the exhaust valve 4 is set based on the accelerator opening and the engine speed, not shown.

The fuel injection amount of the fuel injection valve 8 is determined by the basic injection amount based on the intake air amount detected (measured) by the intake air amount sensor 21 and the engine speed, similarly to general fuel injection amount control. Are determined by performing various corrections, and are controlled.

In the drawing, reference numeral 26 denotes a display device for displaying a failure of the intake air amount sensor 21, which is provided on an operation panel or the like.

Next, the failure determination of the intake air amount sensor 21 will be described with reference to the flowcharts of FIGS.

As shown in FIG. 4, in step 1, the cylinder internal volume V at the closing timing of the intake valve 3 is calculated. this is,
It is calculated from the crank angle at the time of closing control of the intake valve 3, that is, the position of the piston.

Here, assuming that the stroke of the piston is x, the distance between the connecting rod axes is h, and the crank radius is r, when the displacement angle θ from the top dead center (crank angle), x = r (1−COSθ) + λr [1- (1-SIN θ ² / λ ² )
^1/2 ] λ = h / r, and simply, x ≒ r (1−COSθ) + r (1−COS2θ) / 4λ, and the cylinder internal volume V is V = Vcc + Vcyl = Vcc + x · S where Vcc: It is determined from the combustion chamber volume, Vcyl: stroke volume, S: cylinder cross-sectional area = π (bore / 2) ² .

More specifically, the crank angle θ is calculated based on the above equation using a map in which the cylinder volume V is set.

In step 2, the intake air amount (new air mass) of the cylinder 2 is estimated based on the cylinder internal volume V. This is performed according to the flow of FIG.

FIG. 5 is a flow chart showing the steps from Step 12 to Step 1 when the exhaust valve 4 is closed before the intake valve 3 is closed.
The process from 3 to 16 is started.

[0042] At step 13, it reads the crank angle of the closing timing of the exhaust valve 4, in step 14, calculates the cylinder remaining volume V ₀ from the crank angle. If the closing timing of the exhaust valve 4 is the intake top dead center, the cylinder remaining volume V ₀ is the combustion chamber volume, and if it is more retarded than the intake top dead center, the combustion chamber volume is calculated from the closing timing crank angle. by adding the volume to calculate the cylinder remaining volume V _0.

This cylinder remaining volume V ₀ is also calculated using a map in which the cylinder volume V is set for the aforementioned crank angle θ.

[0044] At step 15, it calculates the exhaust pressure, in step 16, calculates the residual gas mass in the cylinder 2 from the cylinder the residual volume V ₀ and exhaust the exhaust gas temperature. The exhaust pressure and the exhaust temperature are based on the engine speed, the accelerator opening, the cooling water temperature, etc., respectively, and are shown in FIGS. 6 and 7 by an experiment or the like. Determine using the map.

The residual gas mass of the cylinder: G is obtained from a gas state equation G = PV / RT.

Where P: exhaust pressure, V: remaining cylinder volume,
R: gas constant = constant of combustion gas (fixed value), T: exhaust temperature After the exhaust valve 4 is closed, when the intake valve 3 is closed, the process proceeds from step 11 to steps 17 to 20.

In step 17, the fresh air volume in the cylinder is calculated. This cylinder fresh air volume is calculated from the cylinder volume V calculated in step 1 of FIG.
Calculate by subtracting the residual gas content calculated in.

In this case, if the state of the combustion gas when the exhaust valve is closed is pressure P ₀ , volume V ₀ , temperature T ₀ , and the state when the intake valve is open is pressure P ₁ , volume V ₁ , temperature T ₁ (however, , P ₁ is affected by the intake pipe negative pressure) is basically _{P 1 V 1 / T 1 =} P 0 V 0
Since / T ₀ = GR, V ₁ = (P ₀ / P ₁ ) (T ₁ / T ₀ ) V ₀ is obtained, and this V ₁ is subtracted from the cylinder volume V as the remaining gas amount to obtain the cylinder fresh air volume. Ask.

In step 18, the intake air temperature is set in step 1.
In step 9, the intake pressure (intake pipe negative pressure) is measured. When the intake valve is provided with a throttle valve to obtain the intake pipe negative pressure,
Since the pressure varies depending on the opening degree of the throttle valve, the intake pressure is detected. As a detection method, a map as shown in FIG. 8 obtained in advance by an experiment or the like from the engine speed and the throttle valve opening may be referred to, or measurement may be performed by providing an intake pressure sensor.
However, when the intake pressure is detected, the fresh air volume in the cylinder in step 17 may be corrected by the intake pressure.

In step 20, an estimated cylinder fresh air mass is calculated from the cylinder fresh air volume, intake air temperature and atmospheric pressure or intake pressure. When the throttle valve is provided, the estimated fresh air mass in the cylinder is corrected to decrease as the intake pipe negative pressure increases.

In this case, the fresh air mass in the cylinder is shown in FIGS.
As shown in FIG. 11, the engine speed, the closing timing of the exhaust valve 4, the opening timing of the intake valve 3, the intake, and the amount of overlap between the exhaust valves 3, 4 change. The estimated fresh air mass in the cylinder is corrected according to the closing timing, the opening timing of the intake valve 3, and the amount of overlap between the intake and exhaust valves 3, 4. For the closing timing of the exhaust valve 4, a correction value is obtained from a map set to a characteristic as shown in FIG. 9, and for the opening timing of the intake valve 3, a correction value is obtained from a map set to a characteristic as shown in FIG. When the intake and exhaust valves 3 and 4 overlap, the correction value is calculated from the map set to the characteristic as shown in FIG. Multiply. FIG. 10 shows a case where the opening timing of the intake valve 3 is on the retard side from the intake top dead center.

Next, in step 3 of FIG. 4, the measured value of the intake air amount sensor (AFM) 21, that is, the intake air mass (temperature correction,
After the pressure is corrected, the intake air mass is compared with the estimated in-cylinder fresh air mass in step 4 and the intake air amount sensor 2
1 is determined.

In the failure determination of the intake air amount sensor 21, when the difference between the intake air mass and the estimated in-cylinder fresh air mass is larger than a predetermined amount (determination reference value), it is determined that a failure has occurred.

FIG. 12 shows an example of a failure criterion based on the engine speed. When the engine speed is low and the intake air is easily sucked into the cylinder 2, an accurate estimated fresh air mass in the cylinder is obtained. Therefore, when the engine speed is low, the difference between the intake air mass and the estimated fresh air mass in the cylinder is small. A criterion is set so that a failure is determined when the difference is relatively small or larger, and a failure is determined when the difference is greater as the engine speed increases.

Further, a failure criterion can be set based on the engine speed and the accelerator opening as shown in FIG. In this case, since the estimated fresh air mass in the cylinder varies due to a delay in opening and closing the intake valve 3 and the like, the error rate increases as the accelerator opening is small and the opening period of the intake valve 3 is short. Therefore, when the accelerator opening is large and the engine speed is low, it is determined that a failure has occurred when the difference between the intake air mass and the estimated fresh air mass in the cylinder is at least a relatively small difference, and the accelerator opening is small and the engine speed is high. A criterion is set so that a failure is determined when the difference is as large as possible.

When it is determined that a malfunction has occurred, a malfunction of the intake air amount sensor 21 is displayed on a display device 26 provided on an operation panel or the like.

As described above, the actual intake air amount of the cylinder 2 is estimated, and the failure of the intake air amount sensor 21 is determined based on the estimated value. Failures such as disconnections can be easily and accurately detected.

In this case, the intake air amount of the cylinder 2 is estimated based on the cylinder volume at the time of closing the intake valve 3, and
By correcting this in accordance with the closing timing of the exhaust valve 4, the opening timing of the intake valve 3, and the amount of overlap between the intake and exhaust valves 3 and 4, a highly accurate estimated intake air amount can be obtained.

A failure criterion is set for each engine operating condition including the engine speed, and the measured value of the intake air amount sensor 21 when the accuracy of the estimated intake air amount is high, that is, when the engine speed is low. It is determined that a failure occurs when the difference between the estimated intake air amount and the difference is equal to or greater than a relatively small difference.

Accordingly, the failure of the intake air amount sensor 21 can be accurately detected. In addition, since the driver is notified by the display device 26 at the time of failure, repair can be performed at an early stage.

On the other hand, in the present engine, the amount of intake air of the cylinder 2 is controlled by the closing timing of the intake valve 3 and the like. Since the intake air amount is corrected according to the degree, that is, the intake air amount is estimated by adding the intake pipe negative pressure, it is possible to cope with the case where a throttle valve is provided.

In this example, the control unit 2
The opening and closing timings of the intake and exhaust valves 3 and 4 are determined based on the opening control timing and the closing control timing of the intake and exhaust valves 3 and 4. However, as shown in FIG. Sensors 30 and 31 may be provided, and the seating sensors 30 and 31 may detect the opening and closing timing of the intake and exhaust valves 3 and 4. As the seat sensors 30 and 31, for example, gap sensors and non-contact position sensors are used, and are installed in the electromagnetic actuators 10 and 11 of the intake and exhaust valves 3 and 4, for example. In this way, a valve failure can be detected and
When the valve fails, the failure determination of the intake air amount sensor 21 can be canceled. Further, it is possible to reduce a variation in the estimated intake air amount due to a delay in opening and closing the intake valve 3 and the like.

In this embodiment, the present invention is applied to an electromagnetically driven variable valve. However, the present invention can also be applied to a variable valve engine that drives intake and exhaust valves by hydraulic pressure.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view showing a first embodiment.

FIG. 2 is a configuration diagram of an electromagnetically driven intake and exhaust valve.

FIG. 3 is a characteristic diagram of an example of an intake valve closing control timing map;

FIG. 4 is a flowchart showing control contents.

FIG. 5 is a flowchart showing control contents.

FIG. 6 is a characteristic diagram of an example of an exhaust pressure map.

FIG. 7 is a characteristic diagram of an example of an exhaust gas temperature map.

FIG. 8 is a characteristic diagram of an example of an intake pressure map.

FIG. 9 is a characteristic diagram of an intake air amount with respect to an exhaust valve closing timing.

FIG. 10 is a characteristic diagram of an intake air amount with respect to an intake valve opening timing.

FIG. 11 is a characteristic diagram of an intake air amount with respect to a valve overlap amount.

FIG. 12 is a characteristic diagram showing an example of a criterion for an engine speed.

FIG. 13 is a characteristic diagram showing an example of a criterion for an engine speed and an accelerator opening.

[Explanation of symbols]

 2 Cylinder 3 Intake valve 4 Exhaust valve 5 Intake pipe 6 Exhaust pipe 8 Fuel injection valve 10, 11 Electromagnetic actuator 17 Drive circuit 20 Control unit 21 Intake amount sensor 22 Speed sensor (crank angle sensor) 23 Accelerator opening sensor 24 Water temperature sensor 25 intake air temperature sensor 26 display device 30, 31 seating sensor

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takahiko Hirasawa 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. F-term (reference) 3G084 BA23 BA33 DA27 DA30 EA11 EB09 EB12 EB22 FA00 FA02 FA07 FA10 FA11 FA33 3G092 AA11 DA07 EA10 EC01 EC10 FB02 FB06 HA01Z HA04Z HA05Z HA06Z HA13Z HE01Z

Claims (9)

[Claims] 1. A variable valve having intake and exhaust valves, which controls an intake air amount of a cylinder and an exhaust gas exhaust according to the opening and closing timing of these valves, and an intake air amount sensor which measures an intake air amount in an intake passage. In the valve engine, intake air amount estimating means for estimating an actual intake air amount based on at least the cylinder internal volume at the time of closing the intake valve; comparing means for comparing the estimated value with a measured value of the intake air amount sensor; A failure detection device for a variable valve engine, comprising: failure determination means for determining a failure of an intake air amount sensor based on a comparison result. 2. The intake air amount estimating means has a correcting means for correcting an estimated value of the intake air amount in accordance with the closing timing of the exhaust valve, the opening timing of the intake valve, or the amount of overlap of the intake and exhaust valves. The variable valve engine failure detection device according to claim 1. 3. The intake valve according to claim 1, wherein a throttle valve is provided in the intake pipe, and the intake air amount estimating unit has a correcting unit that corrects an estimated value of the intake air amount according to an opening degree of the throttle valve. Variable valve engine failure detection device. 4. The failure detection device for a variable valve engine according to claim 3, wherein said correction means reduces and corrects the estimated value of the intake air amount as the opening degree of the throttle valve is small and the intake pipe negative pressure is large. 5. The failure determination unit according to claim 1, wherein a difference between an estimated value of the intake air amount by said intake air amount estimation unit and a measurement value of the intake air amount sensor is larger than a predetermined failure determination reference value. 2. The failure detection device for a variable valve engine according to claim 1, wherein the failure of the intake air amount sensor is determined. 6. The variable valve engine failure detection apparatus according to claim 1, wherein a failure determination criterion by said failure determination means is set for each engine operating condition including at least the engine speed. 7. The variable valve engine failure detection device according to claim 1, wherein the intake air amount estimating means determines the intake / exhaust valve opening / closing timing based on the intake / exhaust valve opening / closing control timing. 8. An intake air amount estimating means for detecting an opening / closing timing of an intake / exhaust valve, wherein the intake air amount estimating means detects an actual intake air amount based on a detection value of the intake / exhaust valve opening / closing timing by the seating sensor. The variable valve engine failure detection device according to claim 1, wherein: 9. The variable valve engine failure detection device according to claim 1, further comprising a display device for displaying a failure of the intake air amount sensor.