JP2021055557A - Valve spring failure diagnosis device - Google Patents

Abstract

To provide a valve spring failure determination device capable of detecting failure of a valve spring by using a simple configuration.SOLUTION: A valve spring failure diagnosis device that detects failure of a valve spring 160 that energizes an intake valve 140 opening/closing an intake port 120 of an engine 1 to a valve closing side comprises: an intake pressure sensor 53 detecting internal pressure of an intake pipe 52 connected to the intake port of the engine; and a failure determination section 90 determining failure of the valve spring when the internal pressure of the intake pipe during fuel cut of the engine is higher than a determination value set on the basis of an operating state of the engine.SELECTED DRAWING: Figure 3

Description

The present invention relates to a device for diagnosing a failure of a valve spring that urges an intake valve or an exhaust valve of an engine in a valve closing direction.

In a 4-stroke reciprocating engine, the intake port that introduces fresh air (combustion air) into the combustion chamber and the exhaust port that discharges exhaust gas (burned gas) from the combustion chamber rotate half as much as the crankshaft. It opens and closes at a predetermined valve timing by an intake valve and an exhaust valve driven by a camshaft that rotates at a speed.
The intake valve and exhaust valve are urged in the valve closing direction by a valve spring, which is a compression coil spring provided around the valve stem, and shut off the gas flow between each port and the combustion chamber except when the valve is opened. It is designed to do.
When the valve spring fails and the force for urging the valve in the valve closing direction becomes weak, the valve sealability deteriorates and the combustion state becomes unstable. In addition, there is a concern that failures such as backfire, valve peripheral parts such as rocker arms may fall off, and the fallen parts may be caught.

As a conventional technique for detecting a failure of an intake / exhaust valve and its peripheral parts, for example, in Patent Document 1, the gas component in the cylinder of a diesel engine has a small amount _{of CO 2 and a large amount of O 2 at the} initial stage of combustion, and CO _{2 at the end of combustion.} is focused on many O ₂ is reduced phenomenon, during the compression stroke from the sampling valve provided on the cylinder outlet and the exhaust gas was collected during the period until the exhaust valve opens from the combustion completion, analyzing each sample by the analyzer It is described that the failure determination of the exhaust valve is performed using the analysis value obtained in the above.
In Patent Document 2, in a failure prediction diagnosis device for a gas engine used in a gas cogeneration system, exhaust pressures from a plurality of cylinders measured by an exhaust pressure sensor are sampled at a predetermined cycle, and exhaust gas of each cylinder is discharged. It is described that engine failure such as intake valve blow-by and exhaust valve blow-through is determined based on the variation of the typical atmospheric pressure value.

Japanese Unexamined Patent Publication No. 1-299436 Japanese Unexamined Patent Publication No. 7-293311

In the technique described in Patent Document 1, it is necessary to provide a sampling valve, a component analyzer, a computer for processing analysis results, and the like in the exhaust device of the engine, and the configuration of the device is complicated. Also, in principle of diagnosis, it is difficult to apply to a premixed spark ignition engine such as a general gasoline engine.
Further, also in the technique described in Patent Document 2, it is necessary to sample the exhaust pressure at a predetermined cycle and perform arithmetic processing, which also complicates the configuration of the apparatus.
Therefore, there is a demand for a technique for appropriately detecting a valve spring failure without complicating the configuration of the device by using the output of a sensor normally provided in an existing general engine.
In view of the above-mentioned problems, an object of the present invention is to provide a valve spring failure determination device capable of detecting a valve spring failure with a simple configuration.

The present invention solves the above-mentioned problems by the following solutions.
The invention according to claim 1 is a valve spring failure diagnosis device that detects a failure of a valve spring that urges an intake valve that opens and closes an intake port of an engine to the valve closing side, and is connected to the intake port of the engine. The intake pressure sensor that detects the internal pressure of the intake pipe and the valve spring failure when the internal pressure of the intake pipe during fuel cut of the engine is higher than the determination value set based on the operating state of the engine. It is a valve spring failure diagnosis device including a failure determination unit for determining.
If the valve spring of the intake valve fails and the valve sealability deteriorates, the urging force of the valve spring loses the negative pressure in the cylinder and opens slightly when the fuel is cut. Since the in-cylinder gas is blown back to the intake pipe side, the internal pressure of the intake pipe increases compared to the normal state.
According to the present invention, the intake pressure provided in a general engine is provided by determining the failure of the valve spring when the internal pressure of the intake pipe is higher than the determination value set based on the operating state of the engine. By using a sensor and a simple configuration that does not require the addition of new sensors, it is possible to appropriately detect a failure of the valve spring of the intake valve.

According to the second aspect of the present invention, the engine has a plurality of cylinders, and the failure determination unit detects a cylinder in which the valve spring has failed based on a time when the internal pressure is periodically increased. The valve spring failure diagnosis device according to claim 1.
According to the present invention, the above-mentioned blow-back of the in-cylinder gas into the intake pipe is mainly generated periodically when the cylinder in which the valve spring has a failure reaches the compression stroke or the exhaust stroke. Based on the time when the internal pressure of the intake pipe is periodically increased, it is possible to appropriately detect the cylinder in which the valve spring has failed.

The invention according to claim 3 is a valve spring failure diagnosis device that detects a failure of a valve spring that urges an exhaust valve that opens and closes an exhaust port of an engine to the valve closing side, and determines the amount of oxygen in the exhaust gas of the engine. An air-fuel ratio sensor that detects the air-fuel ratio based on the air-fuel ratio, and a failure determination unit that determines a failure of the valve spring when the air-fuel ratio is on the rich side of a determination value set based on the operating state of the engine. It is a valve spring failure determination device characterized by being provided.
If the valve spring of the exhaust valve fails and the valve sealability deteriorates, the exhaust gas flows back from the exhaust flow path to the combustion chamber in the intake stroke, and the amount of oxygen in the combustion chamber during combustion decreases. For example, when fuel is injected based on the detection value of the air flow meter, the detection value of the air-fuel ratio sensor shifts to the rich side.
According to the present invention, the air-fuel ratio provided in a general engine is provided by determining the failure of the valve spring when the air-fuel ratio is on the rich side of the determination value set based on the operating state of the engine. By using a sensor and a simple configuration that does not require the addition of new sensors, it is possible to appropriately detect a failure of the valve spring of the exhaust valve.

The invention according to claim 4 includes a speed detection unit that detects the crankshaft rotation speed of the engine, and the failure determination unit has the air fuel ratio on the rich side of the determination value and the crankshaft rotation speed. The valve spring failure determination device according to claim 3, wherein the valve spring failure is determined only when the fluctuation is equal to or greater than a predetermined value.
When the backflow of exhaust gas occurs due to the failure of the valve spring of the exhaust valve, the amount of fresh air that contributes to combustion decreases in the cylinder, and the torque of the engine during the combustion stroke decreases compared to the combustion stroke of other cylinders. Will be done.
According to the present invention, in addition to the above-mentioned enrichment of the air-fuel ratio, the determination accuracy is improved by determining the failure of the valve spring of the exhaust valve only when the crankshaft rotation speed fluctuates by a predetermined value or more. be able to.

In the invention according to claim 5, the engine has a plurality of cylinders, and the failure determination unit detects a cylinder in which the valve spring has failed based on the time when the air-fuel ratio periodically shifts to the rich side. The valve spring failure diagnosis device according to claim 3 or 4, wherein the valve spring failure diagnosis device is characterized in that.
In the invention according to claim 6, the engine has a plurality of cylinders, and the failure determination unit detects a cylinder in which the valve spring has failed based on a time when the crankshaft rotation speed becomes periodically low. The valve spring failure diagnosis device according to claim 3 or 4, wherein the valve spring failure diagnosis device is characterized.
The above-mentioned enrichment of the air-fuel ratio occurs periodically when the cylinder in which the valve spring of the exhaust valve has failed reaches the exhaust stroke, and the fluctuation (decrease) in the crankshaft rotation speed mainly occurs in the valve of the exhaust valve. It occurs periodically when the cylinder with the failed spring reaches the combustion stroke.
According to each of these inventions, a cylinder in which the valve spring of the exhaust valve has failed appropriately is determined based on the time when the air-fuel ratio periodically shifts to the rich side or the time when the crankshaft rotation speed periodically decreases. Can be detected.

As described above, according to the present invention, it is possible to provide a valve spring failure determination device capable of detecting a valve spring failure with a simple configuration.

It is a figure which shows typically the structure of the engine provided with the embodiment of the valve spring failure diagnosis apparatus of this invention. It is a schematic cross-sectional view of the cylinder head of the engine of FIG. It is a flowchart which shows the operation at the time of valve spring failure diagnosis of the intake valve in the valve spring failure diagnosis apparatus of embodiment. It is a flowchart which shows the operation at the time of valve spring failure diagnosis of the exhaust valve in the valve spring failure diagnosis apparatus of embodiment.

Hereinafter, embodiments of a valve spring failure diagnosis device to which the present invention is applied will be described.
The valve spring failure diagnosis device of the embodiment has, for example, a function of determining a failure of a valve spring that urges an intake valve and an exhaust valve of an engine mounted as a driving power source in an automobile such as a passenger car in the valve closing direction. ..
FIG. 1 is a diagram schematically showing a configuration of an engine provided with the valve spring failure determination device of the embodiment.
The engine 1 is a 4-stroke horizontally opposed 4-cylinder direct injection (in-cylinder injection) gasoline engine mounted as a power source for traveling in an automobile such as a passenger car.
The output of the engine 1 is transmitted to the drive wheels of the vehicle via a power transmission mechanism described later.

The engine 1 has a first cylinder 10 and a second cylinder 20 arranged in order from the front end side (opposite side to the transmission, the front side when mounted vertically, and the upper side in FIG. 1) of a crankshaft (not shown) which is an output shaft. , A third cylinder 30 and a fourth cylinder 40.
In the engine 1, for example, the crankshaft is vertically arranged along the front-rear direction of the vehicle.
The first cylinder 10 and the third cylinder 30 are provided in the right cylinder block RB arranged on the right side in the vehicle width direction, and the second cylinder 20 and the fourth cylinder 40 are provided in the left cylinder block LB arranged on the left side in the vehicle width direction. ing.
A right cylinder head RH and a left cylinder head LH are provided at the ends of the right cylinder block RB and the left cylinder block LB on the outer side in the vehicle width direction (opposite to the crankshaft side).

The first cylinder 10, the second cylinder 20, the third cylinder 30, and the fourth cylinder 40 are arranged so as to face each other with the crankshaft interposed therebetween, with the offset amount of the crankpin of each cylinder shifted.
The firing order (explosion order) in the engine 1 is set in the order of the first cylinder 10, the third cylinder 30, the second cylinder 20, and the fourth cylinder 40, and ignites (combusts) at equal intervals of 180 ° at the crank angle. It has become like.

The first cylinder 10, the second cylinder 20, the third cylinder 30, and the fourth cylinder 40 have a cylinder, a piston, a combustion chamber, an intake / exhaust port, an intake / exhaust valve, a valve drive mechanism, and the like, as well as injectors 11, 21, 1. It has 31, 41, spark plugs 12, 22, 32, 42, and the like.
The injectors 11, 21, 31, and 41 are injection devices that directly inject atomized gasoline into the combustion chamber of each cylinder.
The fuel injection amount and fuel injection timing of the injectors 11, 21, 31, and 41 are controlled by the engine control unit 90 according to the operating state of the engine 1.
The injectors 11, 21, 31, and 41 are introduced with fuel pressurized by a fuel pump (not shown) and accumulated, and at the same time, the injectors are opened in response to an injection signal given from the engine control unit 90 to inject fuel.

The spark plugs 12, 22, 32, and 42 ignite the air-fuel mixture formed in each cylinder by an electric spark.
The ignition timing of the spark plugs 12, 22, 32, and 42 is controlled by the engine control unit 90.

Further, the engine 1 includes an intake device 50, an exhaust device 60, a valve timing variable device (not shown), a cooling device, a lubrication device, an EGR device, and the like.
The intake device 50 introduces combustion air into each cylinder.
The intake device 50 includes an intake duct (not shown) that introduces outside air (atmospheric pressure) as combustion air, an air cleaner (not shown) that filters foreign matter such as dust, a throttle valve 51, an intake manifold 52, an intake pressure sensor 53, and the like.

The throttle valve 51 controls the air flow rate for adjusting the output of the engine 1.
The throttle valve 51 is an electric throttle having a butterfly valve (throttle valve) that is opened and closed by an electric actuator, and its opening degree is controlled by the engine control unit 90 according to a required torque set according to the accelerator operation of the driver. ..
The intake manifold 52 is a branch pipe that introduces the air that has passed through the throttle valve 51 into the intake port of each cylinder.
The intake pressure sensor 53 is a pressure sensor that detects the pressure (negative pressure in the intake pipe) in the intake manifold 52.
The output of the intake pressure sensor 53 is sequentially transmitted to the engine control unit 90.

The exhaust device 60 discharges exhaust gas (burned gas) discharged from the combustion chambers of the cylinders 10, 20, 30, and 40 via the exhaust port.
The exhaust device 60 includes an exhaust manifold 61, an exhaust pipe 62, a catalytic converter 63, a silencer 64, an air-fuel ratio sensor 65, a rear O ₂ sensor 66, and the like.

The exhaust manifold 61 is a collecting pipe that collects the exhaust gas emitted from the exhaust ports of the cylinders 10, 20, 30, and 40.
The exhaust pipe 62 is a pipeline for discharging the exhaust gas collected in the exhaust manifold 61 to the outside.

The catalyst converter 63 is an exhaust gas aftertreatment device provided in the middle portion of the exhaust pipe 62.
The catalyst converter 63 is a three-way catalyst in which a noble metal such as platinum, rhodium, or palladium is supported on a carrier such as alumina.
The catalytic converter 63 has a function of reducing _{HC, CO, and NO X} in the exhaust gas in a predetermined active region where the air-fuel ratio of the engine 1 is near the stoichiometric value.

The silencer 64 is a silencer provided on the downstream side (outlet side) of the catalytic converter 63 in the exhaust pipe 62 to reduce acoustic energy.

The air-fuel ratio sensor 65 is provided near the inlet of the catalytic converter 63 and generates different output voltages depending on the air-fuel ratio in the engine 1.
The engine control unit 90 performs air-fuel ratio feedback control for setting the fuel injection amount so that the air-fuel ratio in the engine 1 is within the active range of the three-way catalyst according to the output of the air-fuel ratio sensor 65.

The rear O ₂ sensor 66 is provided near the outlet of the catalytic converter 63 and generates different output voltages depending on _{the O 2 concentration in the exhaust gas.}
The output of the rear O ₂ sensor 66 is transmitted to the engine control unit 90.

The engine 1 further includes a crank angle sensor 70, a water temperature sensor 80, and the like.
The crank angle sensor 70 is a magnetic angle sensor that detects an angular position (crank angle / CA) of a crankshaft (not shown) which is an output shaft of the engine 1.
The crank angle sensor 70 includes a sensor plate 71, a position sensor 72, and the like.

The sensor plate 71 is a disk-shaped member fixed to the rear end of the crankshaft, and has a sprocket-like shape formed by radially projecting a plurality of vanes (teeth) at predetermined angular intervals on the outer peripheral edge. It has a shape.
The position sensor 72 is a magnetic pickup arranged so as to face the outer peripheral edge of the sensor plate 71, and has a magnet, a core, a coil, a terminal, and the like.
The position sensor 72 outputs a predetermined pulse signal when the vane of the sensor plate 71 passes immediately before the position sensor 72.
The engine control unit 90 can calculate the rotation speed (crankshaft rotation speed) of the engine 1 and the crank angle based on the output of the crank angle sensor 70.
The engine control unit 90 has a function as a speed detection unit that detects the rotation speed of the crankshaft of the engine 1.

The water temperature sensor 80 detects the temperature of the cooling water (coolant) flowing in the water jacket, which is the cooling water flow path formed in the cylinder head and the cylinder.
The outputs of the crank angle sensor 70 and the water temperature sensor 80 are transmitted to the engine control unit 90.

The engine control unit (ECU) 90 comprehensively controls the engine 1 and its accessories.
The engine control unit 90 includes, for example, an information processing device such as a CPU, a storage device such as a RAM or a ROM, an input / output interface, and a bus connecting these.
The engine control unit 90 has, for example, a throttle valve opening degree, a fuel injection amount, which are not shown so that the actual torque substantially matches the required torque according to the required torque set based on the accelerator operation of the driver or the like. Controls fuel injection timing, ignition timing, valve timing, etc.
Further, the engine control unit 90 executes a fuel cut that temporarily stops fuel injection when the traveling state of the vehicle satisfies a predetermined fuel cut condition.
Further, the engine control unit 90 has a function as a failure determination unit of a valve spring failure diagnosis device for detecting deterioration of the intake valve spring 160 and the exhaust valve spring 170, which will be described later, due to a decrease in the spring constant, and damage such as breakage.
This point will be described in detail later.

FIG. 2 is a schematic cross-sectional view of the cylinder head of the engine of FIG.
FIG. 2 shows a cross section cut along a plane including the valve stem axis of the intake valve and the exhaust valve of the first cylinder 10 in the cylinder head, but other cylinders have the same configuration.
The cylinder head 100 includes a combustion chamber 110, an intake port 120, an exhaust port 130, an intake valve 140, an exhaust valve 150, an intake valve spring 160, an exhaust valve spring 170, an intake camshaft 180, an exhaust camshaft 190, and the like. Has been done.

The combustion chamber 110 is a portion that cooperates with the crown surface of the piston (not shown) and the inner peripheral surface of the cylinder sleeve to form a space portion in which the air-fuel mixture is ignited and burned.
The combustion chamber 110 is, for example, a pent roof type formed as a recess in which a surface portion inside the cylinder of the cylinder head is recessed.

The intake port 120 is a flow path connected to the intake manifold 52 to introduce fresh air (air) into the combustion chamber 110.
The exhaust port 130 is a flow path for discharging exhaust gas (burned gas) from the combustion chamber 110 to the exhaust manifold 61.
The intake port 120 and the exhaust port 130 are formed, for example, bifurcated, and two intake valves 140 and two exhaust valves 150 are provided for each cylinder.

The intake valve 140 opens and closes the intake port 120 at a predetermined valve timing.
The intake valve 140 is normally opened from the end of the exhaust stroke to the beginning of the compression stroke through the intake stroke.
The intake valve 140 has a valve head 141 and a valve stem 142.
The valve head 141 is a disk-shaped portion provided at the end of the intake valve 140 on the combustion chamber 110 side.
The valve head 141 functions as a valve body that closes the end of the intake port 120 on the combustion chamber 110 side when the intake valve 140 is closed.
The valve stem 142 is a columnar portion provided so as to project from a surface portion of the valve head 141 opposite to the combustion chamber 110 side.
The valve stem 142 is inserted into a cylindrical stem guide provided in the cylinder head 100, and is slidably supported with respect to the cylinder head 100 along the longitudinal direction thereof.

The exhaust valve 150 opens and closes the exhaust port 130 at a predetermined valve timing.
The exhaust valve 150 is usually opened from the end of the combustion stroke, through the exhaust stroke, to the beginning of the intake stroke.
The exhaust valve 150 has a valve head 151 and a valve stem 152.
The valve head 151 is a disk-shaped portion provided at the end of the exhaust valve 150 on the combustion chamber 110 side.
The valve head 151 functions as a valve body that closes the end of the exhaust port 130 on the combustion chamber 110 side when the exhaust valve 150 is closed.
The valve stem 152 is a columnar portion provided so as to project from a surface portion of the valve head 151 opposite to the combustion chamber 110 side.
The valve stem 152 is inserted into a cylindrical stem guide provided in the cylinder head 100, and is slidably supported with respect to the cylinder head 100 along the longitudinal direction thereof.

The intake valve spring 160 is a spring element that urges the intake valve 140 to the valve closing side.
The exhaust valve spring 170 is a spring element that urges the exhaust valve 150 to the valve closing side.
The intake valve spring 160 and the exhaust valve spring 170 are, for example, compression coil springs, and the camshaft-side portion of the valve stems 142 and 152 of each valve in the longitudinal direction is inserted into the inner diameter side thereof.
The ends of the intake valve spring 160 and the exhaust valve spring 170 on the combustion chamber 110 side are in contact with the seat portion formed on the cylinder head 100.
The ends of the intake valve spring 160 and the exhaust valve spring 170 on the camshaft side are in contact with the spring seats 161, 171 that project from the ends of the valve stems 142 and 152 to the outer diameter side in a brim shape.

The intake camshaft 180 and the exhaust camshaft 190 are shaft-shaped members that rotate at half the rotation speed of the crankshaft of the engine 1.
The intake camshaft 180 and the exhaust camshaft 190 are rotatably attached to the cylinder head 100 around a rotation axis parallel to the crankshaft.
The intake camshaft 180 and the exhaust camshaft 190 have cam portions that open the intake valve 140 and the exhaust valve 150 at predetermined valve timings, respectively.
A cam sprocket (not shown) is provided at the ends of the intake camshaft 180 and the exhaust camshaft 190.
The cam sprocket is rotationally driven in conjunction with the crankshaft via a crank sprocket and a timing chain (not shown) provided on the crankshaft.
The cam sprocket is provided with a variable valve timing mechanism that changes the phase of the intake cam shaft 180 and the exhaust cam shaft 190 with respect to the cam sprocket according to the operating state of the engine 1 to change the valve timing.
The variable valve timing mechanism is controlled by the engine control unit 90.

The intake camshaft 180 and the exhaust camshaft 190 are connected to the ends of the intake valve 140 and the valve stems 142 and 152 of the exhaust valve 150 via rocker arms 181, 191 that swing around the support shaft provided in the cylinder head 100. Press to open the intake valve 140 and the exhaust valve 150.
The rocker arms 181 and 191 are provided with hydraulic lash adjusters 182 and 192 that automatically adjust the valve clearance.

Hereinafter, the operation of the valve spring failure diagnosis device of the embodiment will be described.
FIG. 3 is a flowchart showing the operation of the intake valve at the time of valve spring failure diagnosis in the valve spring failure diagnosis device of the embodiment.
Hereinafter, each step will be described step by step.

<Step S01: Judgment during fuel cut execution>
The engine control unit 90 determines whether or not a fuel cut for temporarily stopping the fuel injection of the engine 1 is being executed.
If the fuel cut is being executed, the process proceeds to step S02, and in other cases, a series of processes is completed (returned).

<Step S02: Engine operating state detection>
The engine control unit 90 detects a parameter indicating the current operating state of the engine 1.
For example, the rotation speed of the crankshaft (so-called engine speed) detected by the crank angle sensor 70, the opening degree of the throttle valve 51, the fresh air flow rate in the intake device 50 detected by the air flow meter (not shown), the valve timing, and the EGR rate. , Get information about atmospheric pressure, etc.
Then, the process proceeds to step S03.

<Step S03: Acquisition of intake manifold internal pressure history>
The engine control unit 90 acquires the internal pressure (intake pipe pressure) of the intake manifold 52 detected by the intake pressure sensor 53, and records and accumulates the history over a predetermined period.
Then, the process proceeds to step S04.

<Step S04: Valve spring failure judgment value setting>
The engine control unit 90 sets a valve spring failure determination value (for determination based on the intake pipe pressure) based on the operating state of the engine 1 acquired in step S02.
The valve spring failure determination value is set based on, for example, the intake pipe pressure that can normally be obtained in the current operating state of the engine 1 when the intake valve spring 160 is normal.
Then, the process proceeds to step S05.

<Step S05: Valve spring failure determination using intake manifold internal pressure>
The engine control unit 90 compares the internal pressure of the intake manifold 52 acquired in step S03 with the valve spring failure determination value set in step S04.
As the internal pressure used here, for example, an average value for a predetermined period or a value obtained by removing a high frequency region by a predetermined low-pass filter can be used in order to exclude a peak value instantaneously generated due to inspiratory pulsation or the like.
If the internal pressure of the intake manifold 52 is equal to or higher than the valve spring failure determination value, the process proceeds to step S06, and in other cases, a series of processes is completed (returned).

<Step S06: Valve spring failure judgment established>
The engine control unit 90 establishes a failure determination of the intake valve spring 160.
Then, the process proceeds to step S07.

<Step S07: Identifying the failed cylinder>
The engine control unit 90 identifies the cylinder in which the intake valve spring 160 has failed based on the history of the internal pressure of the intake manifold 52 acquired in step S03.
For example, it can be identified that the intake valve spring 160 has failed in the cylinder that is in the compression stroke when the internal pressure of the intake manifold 52 is periodically increased.
Then, the process proceeds to step S08.

<Step S08: Engine control safe mode / warning output>
The engine control unit 90 switches to safe mode engine control that limits the output torque and the number of revolutions (crankshaft rotation speed) of the engine 1 to a predetermined upper limit or less in order to prevent the damage of the engine 1 from progressing.
Further, the engine control unit 90 outputs a warning indicating that a bulb spring failure has occurred by using a warning light or an image display device provided on an instrument panel (not shown).
After that, a series of processes is completed.

FIG. 4 is a flowchart showing an operation at the time of valve spring failure diagnosis of the exhaust valve in the valve spring failure diagnosis device of the embodiment.
Hereinafter, each step will be described step by step.

<Step S11: Judgment during fuel cut execution>
The engine control unit 90 determines whether or not a fuel cut for temporarily stopping the fuel injection of the engine 1 is being executed.
If the fuel cut is being executed, the series of processes is completed (returned), and in other cases, the process proceeds to step S12.

<Step S12: Engine operating state detection>
The engine control unit 90 detects a parameter indicating the current operating state of the engine 1.
Then, the process proceeds to step S13.

<Step S13: Acquisition of air-fuel ratio sensor output history>
The engine control unit 90 acquires the detected value of the air-fuel ratio detected by the air-fuel ratio sensor 65, and records and accumulates the history over a predetermined period.
After that, the process proceeds to step S14.

<Step S14: Crank angle sensor output history acquisition>
The engine control unit 90 acquires the angular position of the crankshaft detected by the crank angle sensor 70, and records and accumulates the history over a predetermined period.
Then, the process proceeds to step S15.

<Step S15: Air-fuel ratio determination value setting>
The engine control unit 90 sets a valve spring failure determination value (for determination based on the air-fuel ratio) based on the operating state of the engine 1 acquired in step S12.
The valve spring failure determination value is set based on, for example, the air-fuel ratio that can normally be taken in the current operating state of the engine 1 when the exhaust valve spring 170 is normal.
Then, the process proceeds to step S16.

<Step S16: Rotation fluctuation determination value setting>
The engine control unit 90 sets a valve spring failure determination value (for determination based on rotational fluctuation) based on the operating state of the engine 1 acquired in step S12.
The valve spring failure determination value is, for example, a rotation fluctuation (for example, a crank angle of 180 degrees corresponding to the combustion stroke of each cylinder) that can normally occur in the current operating state of the engine 1 when the exhaust valve spring 170 is normal. It is set based on the difference between the maximum and minimum values of the average rotation speed for each cylinder in the range).
Then, the process proceeds to step S17.

<Step S17: Valve spring failure determination using air-fuel ratio>
The engine control unit 90 compares the detected value of the air-fuel ratio sensor 65 acquired in step S13 with the valve spring failure determination value set in step S15.
If the air-fuel ratio detected by the air-fuel ratio sensor 65 is on the rich side of the valve spring failure determination value, the process proceeds to step S18, and in other cases, a series of processes is completed (returned).

<Step S18: Valve spring failure determination using rotational fluctuation>
The engine control unit 90 compares the fluctuation of the rotation speed of the crankshaft acquired in step S14 with the valve spring failure determination value set in step S16.
If the absolute value of the variation in the rotational speed detected by the crank angle sensor 70 is equal to or greater than the valve spring failure determination value, the process proceeds to step S19, and in other cases, a series of processes is completed (returned).

<Step S19: Valve spring failure determination established>
The engine control unit 90 establishes a failure determination of the exhaust valve spring 170.
Then, the process proceeds to step S20.

<Step S20: Identifying the failed cylinder>
The engine control unit 90 identifies the cylinder in which the failure of the exhaust valve spring 170 has occurred based on the history of the air-fuel ratio acquired in step S13.
For example, it can be identified that the failure of the exhaust valve spring 170 has occurred in the cylinder whose exhaust stroke is in the period when the air-fuel ratio is periodically rich.
Then, the process proceeds to step S21.

<Step S21: Engine control safe mode / warning output>
The engine control unit 90 switches to safe mode engine control that limits the output torque and the number of revolutions (crankshaft rotation speed) of the engine 1 to a predetermined upper limit or less in order to prevent the damage of the engine 1 from progressing.
Further, the engine control unit 90 outputs a warning indicating that a bulb spring failure has occurred by using a warning light or an image display device provided on an instrument panel (not shown).
After that, a series of processes is completed.

As described above, according to the present embodiment, the following effects can be obtained.
(1) When the internal pressure of the intake manifold 52 is higher than the determination value set based on the operating state of the engine 1 (when the intake pipe pressure is abnormally higher than the normal intake pipe pressure), the intake valve spring 160 fails. By determining, the intake pressure sensor 53 provided in a general engine can be used, and a failure of the intake valve spring 160 can be appropriately detected by a simple configuration that does not require the addition of new sensors. it can.
(2) By detecting the cylinder in which the intake valve spring 160 has failed based on the time when the internal pressure of the intake manifold 52 is periodically increased, the cylinder in which the failure has occurred can be appropriately identified by a simple configuration.
(3) Failure of the exhaust valve spring 170 when the air-fuel ratio is on the rich side of the judgment value set based on the operating state of the engine 1 (when the air-fuel ratio is abnormally rich with respect to the normal air-fuel ratio). By using the air-fuel ratio sensor 65 provided in a general engine, the failure of the exhaust valve spring 170 can be appropriately detected by a simple configuration that does not require the addition of new sensors. Can be done.
(4) In addition to enriching the air-fuel ratio, it is possible to improve the determination accuracy by determining the failure of the exhaust valve spring 170 only when the rotation speed fluctuation (rotational fluctuation) of the crankshaft exceeds a predetermined value. it can.
(5) By detecting the cylinder in which the exhaust valve spring 170 has failed based on the time when the air-fuel ratio periodically shifts to the rich side, the cylinder in which the failure has occurred can be appropriately identified by a simple configuration.

(Modification example)
The present invention is not limited to the embodiments described above, and various modifications and modifications can be made, and these are also within the technical scope of the present invention.
(1) The configuration of the valve spring failure diagnosis device and the engine is not limited to the above-described embodiment, and can be changed as appropriate.
For example, the cylinder layout of the engine, the number of cylinders, the fuel injection method, the presence / absence of a supercharger, and the like are not limited to the configuration of the above-described embodiment, and can be appropriately changed.
(2) In the embodiment, the failure diagnosis of the exhaust valve spring is performed by comparing the air-fuel ratio and the rotation fluctuation of the crankshaft with the set valve spring failure judgment values, but only the judgment using the air-fuel ratio is performed. The failure determination may be established by.
(3) In the embodiment, the cylinder in which the exhaust valve spring failure occurs is specified by using the fluctuation of the air-fuel ratio, but the present invention is not limited to this, and the exhaust valve spring is not limited to this, based on the history of the rotation speed of the crankshaft. The cylinder in which the failure has occurred may be identified. For example, a cylinder that is in the combustion stroke when the rotation speed is periodically decreasing may be specified as a failure-causing cylinder.

1 Engine 10 1st cylinder 11 Injector 12 Spark plug 20 2nd cylinder 21 Injector 22 Ignition plug 30 3rd cylinder 31 Injector 32 Ignition plug 40 4th cylinder 41 Injector 42 Spark plug 50 Intake device 51 Throttle valve 52 Intake manifold 53 Intake pressure Sensor 60 Exhaust Manifold 61 Exhaust Manifold 62 Exhaust Pipe 63 Catalytic Converter 64 Silencer 65 Air Fuel Ratio Sensor 66 Rear O ₂ Sensor 70 Crank Angle Sensor 71 Sensor Plate 72 Position Sensor 80 Water Temperature Sensor 90 Engine Control Unit (ECU)
100 Cylinder head 110 Combustion chamber 120 Intake port 130 Exhaust port 140 Intake valve 141 Valve head 142 Valve stem 150 Exhaust valve 151 Valve head 152 Valve stem 160 Intake valve spring 161 Spring seat 170 Exhaust valve spring 171 Spring seat 180 Intake camshaft 181 Rocker Arm 182 Hydraulic Crash Adjuster 190 Exhaust Camshaft 191 Rocker Arm 192 Hydraulic Crash Adjuster

Claims (6)

A valve spring failure diagnosis device that detects a failure of the valve spring that urges the intake valve that opens and closes the intake port of the engine to the valve closing side.
An intake pressure sensor that detects the internal pressure of the intake pipe connected to the intake port of the engine,
It is characterized by including a failure determination unit that determines a failure of the valve spring when the internal pressure of the intake pipe during fuel cut of the engine is higher than a determination value set based on the operating state of the engine. Valve spring failure diagnostic device. The engine has multiple cylinders
The valve spring failure diagnosis device according to claim 1, wherein the failure determination unit detects a cylinder in which the valve spring has failed based on a time when the internal pressure is periodically increased. A valve spring failure diagnosis device that detects a failure of the valve spring that urges the exhaust valve that opens and closes the exhaust port of the engine to the valve closing side.
An air-fuel ratio sensor that detects the air-fuel ratio based on the amount of oxygen in the exhaust gas of the engine, and
A valve spring failure determination device including a failure determination unit that determines a failure of the valve spring when the air-fuel ratio is on the rich side of a determination value set based on the operating state of the engine. A speed detection unit for detecting the rotation speed of the crankshaft of the engine is provided.
The claim is characterized in that the failure determination unit determines a failure of the valve spring only when the air-fuel ratio is on the rich side of the determination value and the fluctuation of the crankshaft rotation speed is equal to or greater than a predetermined value. Item 3. The valve spring failure determination device according to item 3. The engine has multiple cylinders
The valve spring according to claim 3 or 4, wherein the failure determination unit detects a cylinder in which the valve spring has failed based on a time when the air-fuel ratio periodically shifts to the rich side. Failure diagnosis device. The engine has multiple cylinders
The valve spring failure according to claim 3 or 4, wherein the failure determination unit detects a cylinder in which the valve spring has failed based on a time when the crankshaft rotation speed becomes periodically low. Diagnostic device.

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