JPH04301160A - Fault diagnosing method for isc valve of engine - Google Patents

Abstract

PURPOSE:To detect electric abnormality of an ISC valve such as disconnection and short circuit, and malfunction of mechanical operation of the ISC valve itself accurately with simple method. CONSTITUTION:When a throttle is full closed, acoustic velocity choke air flow quantity, which is obtained on the basis of the flow quantity control signal for controlling an ISC valve as parameter, and the intake air flow quantity, which is detected by an intake air flow quantity sensor, are compared with each other, and in the case that a comparison valve thereof exists within a preset tolerance, normality of the ISC valve is judged, and in the case that the described comparison value exists out of the tolerance, fault of the described ISC valve system is judged.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention compares the sonic choke air flow rate determined according to the opening degree of an ISC (idle speed control) valve with the actual intake air flow rate detected by an intake air amount sensor. , relates to an engine ISC valve fault diagnosis method for diagnosing a fault in an ISC valve system.

0002

[Prior Art] In recent electronically controlled engines,
The engine speed during idle operation is controlled by an ISC valve installed in an air bypass passage that bypasses the throttle valve.

[0003] In general, there are solenoid type, motor type, negative pressure type, etc. actuators for driving and controlling the ISC valve. For example, in the solenoid type ISC valve, the The ISC valve is driven by a set duty pulse, and the flow rate of intake air passing through the air bypass passage is adjusted to control the engine rotation speed to the target rotation speed.

[0004] When this ISC valve becomes uncontrollable,
Since the engine rotational speed becomes unstable and idling operation is significantly hindered, various failure diagnosis methods have been devised and adopted to detect failure of the ISC valve at an early stage.

For example, in Japanese Unexamined Patent Publication No. 1-244143, a duty pulse output to an ISC valve is used to determine whether or not harnesses connected to the ISC valve and the ISC valve are energized. A technique is disclosed in which a determination is made based on the relationship with a monitor voltage for detecting pulses.

[0006]

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, it is possible to detect electrical abnormalities such as circuit failures, disconnections or short circuits in harnesses, and disconnections in excitation coils installed in ISC valves. , fixed due to carbon, oil, etc. intervening in the bypass passage,
Mechanical inoperability, such as so-called valve stick, cannot be detected, and conventionally, this mechanical inoperability has been determined based on the driver's driving sensation.

[0007] Therefore, for example, when the ISC valve is stuck at a predetermined opening degree, the discovery of the failure tends to be delayed because the idle rotation speed is ensured.

The present invention has been made in view of the above circumstances, and is capable of not only detecting electrical abnormalities such as disconnections or short circuits in harnesses, but also easily detecting mechanical and electrical inoperability of ISC valves. It is an object of the present invention to provide a fault diagnosis method for an engine ISC valve that can accurately detect the fault using a method.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a fault diagnosis method for an engine ISC valve according to the present invention uses a flow control signal energized to the ISC valve as a parameter to determine the ISC valve opening when the throttle valve is fully closed. Find the sonic choke air flow rate corresponding to , then compare this sonic choke air flow rate with the intake air flow rate detected by the intake air amount sensor, and if the comparison value of both flow rates is outside the preset tolerance range, It is determined that the above ISC valve has failed.

0010

[Operation] In the above configuration, when the throttle is fully closed, I
A control signal is energized to the SC valve to control the flow of intake air through the ISC valve.

In the meantime, the sonic choke air flow rate corresponding to the ISC valve opening is determined using the flow rate control signal as a parameter, and then this sonic choke air flow rate is compared with the intake air flow rate detected by the intake air amount sensor. If the flow rate comparison value is within the preset tolerance range, I
If the SC valve system is determined to be normal, and on the other hand, the comparison value is outside a preset tolerance range, it is determined that the ISC valve system is malfunctioning.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

The drawings show one embodiment of the invention, and FIG.
A flowchart showing the control procedure of the SC valve, FIG.
Flowchart showing the SC valve failure determination procedure, Figure 3
FIG. 4 is a flowchart showing the injector control procedure.
is a conceptual diagram of the sonic choke air flow rate map, Fig. 5 is a conceptual diagram of the engine control system, Fig. 6 is a circuit diagram of the control device, and Fig. 7
is a vertical cross-sectional view of the ISC valve, and FIG. 8 is a vertical cross-sectional view of the ISC valve, and FIG.
It is a sectional view taken along III.

(Structure) Reference numeral 1 in the figure is the engine body, and the figure shows a horizontally opposed engine.

An air chamber 4 is provided upstream of the intake manifold 3 that communicates with the intake port 2a of the engine body 1.
A throttle chamber 5 is communicated with the throttle chamber 5 through an intake pipe 6, and an air cleaner 7 is installed upstream of the throttle chamber 5 through an intake pipe 6. Note that the reference numeral 3a is a variable intake valve.

On the other hand, the exhaust port 2 of the engine body 1
A catalytic converter 10 is interposed in an exhaust pipe 9 that communicates with the exhaust pipe 9 via an exhaust manifold 8.

Further, a throttle valve 11 is provided in the throttle chamber 5, and an injector 12 is provided directly upstream of the intake port 2a of each cylinder of the intake manifold 3. are communicated via a fuel passage 14. A fuel pump 15 and a fuel filter 16 are interposed in this fuel passage 14 from the fuel tank 13 side, and further,
Each of the injectors 12 is communicated with the fuel tank 13 via a return passage 18 that includes a pressure regulator 17 that regulates the fuel pressure to a predetermined pressure.

Furthermore, the air cleaner 7 of the intake pipe 6
An intake air amount sensor (a hot wire air flow meter in the figure) 19 is installed immediately downstream of the throttle valve 11, and a throttle opening sensor 20a that detects the throttle opening and a throttle opening sensor 20a that detects the throttle opening when the throttle valve 11 is fully closed. An ISC (idle speed control) valve 21 is interposed in an air bypass passage 6a of the intake pipe 6 that bypasses the throttle valve 11. Further, an O2 sensor 22 is located upstream of the catalytic converter 10 in the exhaust pipe 9.

Further, a crank angle sensor 25a for detecting engine rotational speed and the like is provided opposite to a crank rotor 23 which is integrally formed with a crank pulley (not shown), which is pivotally attached to the crankshaft 1a of the engine 1. A cam sensor 25b for detecting cam pulses for cylinder discrimination is provided opposite to a cam rotor 24 integrally formed with a cam sprocket (not shown), which is connected to the camshaft 1b of the engine 1.

[0020]Furthermore, it is attached to the cylinder head 2,
An igniter 27 is connected to a spark plug 26 whose ignition portion faces the combustion chamber. Furthermore, a cooling water temperature sensor 28 is disposed in the cylinder block of the engine main body 1.

Further, as shown in FIGS. 7 and 8, a slider 31 for setting the opening area of the air bypass passage 6a is installed in the valve body 21a of the ISC valve 21 installed in the air bypass passage 6a. A magnet 33 is fixed to the base side of a solenoid shaft 32 to which the slider 31 is pivoted, and a solenoid coil 34 fixed to the valve body 21a is provided around the magnet 33. Note that the slider 31 is moved through the air bypass passage 6a by the biasing force of a return spring (not shown).
is constantly biased in the direction of closing the valve.

(Circuit configuration of control device) On the other hand, reference numeral 36 in FIG. 6 is a control device consisting of a microcomputer or the like.
A CPU (central processing unit) 37 of this control device 36,
ROM 38, RAM 39, backup RAM (nonvolatile RAM) 40, and I/O interface 4
1 are connected to each other via a bus line 42, and a predetermined stabilized voltage is supplied from a constant voltage circuit 43.

The constant voltage circuit 43 is connected to a battery 45 via a control relay 44, and a key switch 46 is turned on.
When the relay contact of the control relay 44 is closed, it supplies power for control to each part, and is directly connected to the battery 45, and provides backup power to the backup RAM 40 even when the key switch 46 is turned off. supply.

[0024] Also, the I/O interface 41
Each of the above sensors 19, 20a, 22, 2 is connected to the input port of
5a, 25b, 28, in addition to the idle switch 20b,
Atmospheric pressure sensor 51, neutral switch 52 (for automatic transmission vehicles, inhibitor switch 53 that detects the N or P range of the select lever)
), a vehicle speed sensor 54, and an air conditioner switch 55 are connected, and the positive terminal of the battery 45 is also connected, and the terminal voltage is monitored.

On the other hand, an igniter 27 is connected to the output port of the I/O interface 41, and the injector 12, the pump relay (not shown) of the fuel pump 15, and the ISC valve 21 are connected via the drive circuit 47.
A solenoid coil 34 and an ECS (electronic control system) lamp 56 disposed on an instrument panel (not shown) are connected.

The ROM 38 stores control programs, fixed data, and the like. The fixed data includes a sonic choke air flow rate map MAP (Qc).

Further, the RAM 39 stores data after processing the output signals of the sensors, data processed by the CPU 37, and the like. Furthermore, the backup RAM 40 has ON/OFF control of a key switch 46.
Backup power is always supplied regardless of the engine operation, and even if the key switch 46 is turned OFF to stop the engine operation, the stored contents are not lost, and trouble data such as ISC valve abnormality data, which will be described later, is stored.

This trouble data can be read by connecting a failure diagnosis serial monitor or the like to a failure diagnosis connector (not shown) connected to the output port of the I/O interface 41.

Furthermore, in the CPU 37, the ROM 3
According to the control program stored in 8, the above RAM
39. Based on various data stored in the backup RAM 40, the fuel injection pulse width Ti for driving the injector 12 is calculated for each cylinder, and the I
The duty ratio for driving the SC valve 21 is calculated, and the amount of intake air is controlled so that the engine speed becomes the target speed.

(Function) Next, the function of the embodiment having the above configuration will be explained.

ISC valve control routine: During engine operation, if it is determined in the main routine that the idle operating condition is satisfied, the ISC valve control routine shown in FIG. 1 is executed by interruption.

The idle operating conditions are, for example, vehicle speed = 8 km/h or less, and the idle switch 20b is ON (throttle fully closed), or the neutral switch 52 (inhibitor switch 53 in the case of an automatic transmission vehicle) is turned on. If it is ON and the idle switch 20b is ON, it is determined that it is established.

First, step (hereinafter abbreviated as "s") 10
1, in order to bring the engine speed closer to the target speed,
Duty ratio ISCDTY for driving ISC valve 21
Calculate.

[0034] The target rotation speed is set based on the cooling water temperature, ON/OFF of the air conditioner switch 55, etc., and the duty ratio ISCDTY takes into account various correction factors based on electrical load characteristics, battery voltage, etc. has been done.

Then, in s102, the duty ratio I
A drive pulse corresponding to SCDTY is output to the solenoid coil 34 of the ISC valve 21.

Then, the solenoid shaft 32 of the ISC valve 21 rotates by a predetermined angle in the direction around the axis in FIG. 8 against the biasing force of a return spring (not shown) by an amount corresponding to the duty ratio ISCDTY, and the air bypass passage is opened. Control the air flow rate passing through 6a.

Note that in an operating range where the idle operating conditions are not satisfied (for example, deceleration running), the solenoid coil 34 of the ISC valve 21 is set to a fixed duty ratio IS.
A drive pulse corresponding to CDTY is output.

:ISC valve failure determination: On the other hand, after starting the engine, the ISC valve failure determination flow shown in FIG.
．． An interrupt is executed every SEC.

First, in s201, the idle switch 20
It is determined whether b is ON (throttle valve 11 is fully closed), and if it is ON, the process proceeds to s202, and if it is OFF (throttle valve 11 is open), the process proceeds to s213. Throttle valve 11 is fully closed (idle switch 20b is O)
In the N) state, the intake air is supplied only from the air bypass passage 6a, so the failure determination condition for the ISC valve is satisfied.

When the process proceeds to s202, the delay counter N is counted up (N←N+1), and in s204, this delay counter N and a set value NSET (for example, NSE
T=10), and if N<NSET, the routine is exited, and if N≧NSET, that is, for example,
If NSET=10, if it is determined that the idle operation condition has been satisfied for at least 1 SEC, s205
Proceed to.

Immediately after the throttle valve 11 is closed, the negative pressure in the air chamber 4 may not have fallen completely yet.
A sufficient delay time (NSET) is required for the negative pressure inside to decrease by closing the throttle valve 11.

[0042] Then, in s204 above, N≧NSET
When it is determined that the above-mentioned ISC is
Duty ratio ISCDT set in valve control routine
The sonic choke air flow rate Qc is set using Y or the fixed duty ratio ISCDTY as a parameter.

Sonic choke is a phenomenon in which the air flow rate no longer increases when the negative pressure is reduced to approximately 0.5 atmospheres or less, and the air flow rate passing through the air bypass passage 6a is reduced by the ISC.
The sonic choke air flow rate determined by the opening degree of the valve 21 (
critical air flow rate).

[0044] The sonic choke air flow rate map MAP (
In each region of Qc), the duty ratio ISCDTY and I
The duty ratio ISCDT is calculated in advance through experiments, assuming that the opening degree of the SC valve 21 corresponds to 1:1.
The sonic choke air flow rate Qc for Y is stored.

Thereafter, in s206, the sonic choke air flow rate Qc and the ISC when the throttle is fully closed are determined.
Comparison value RERR with the actual intake air amount Qa detected by the intake air amount sensor 19 corresponding to the intake air flow rate passing through the balgo 21 (RERR = (Qa/Qc) x 100)
is calculated, and in s207, this comparison value RERR (%) is compared with a comparison lower limit value RERRLo (for example, 70%) and a comparison upper limit value RERRHi (for example, 130%),
It is determined whether this comparison value RERR falls within the allowable range.

RERRLo ≧RERR, that is,
If the intake air amount Qa is significantly lower than the sonic choke air flow rate Qc, the process advances to s208 and it is determined whether the sonic choke condition is satisfied.

The sonic choke conditions are as follows, assuming that the charging efficiency for each cylinder is 40% or less.

Qa/(2.Ne)<0.4.γ.
DQa: Intake air amount (g/sec) Ne: Engine speed (rps) γ: Air density (g/lit.) D: Total displacement per cylinder (lit.) The above sonic choke condition is satisfied. In this case, the above ISC valve 21
Electrical failure of harnesses or ISC valve 2
After determining that the slider 31 is not opening as specified due to a mechanical or electrical failure of 1 itself, the ECS lamp 56 is turned on in s209 (at the same time, the abnormality code number is stored in the corresponding address of the backup RAM 40). , get out of routine.

Furthermore, if it is determined in s208 that the sonic choke condition is not satisfied, the comparison value RERR set under the failure of the sonic choke condition may be determined by other factors (for example, supercharging by a supercharger). It is determined that this is included, and without determining that there is a failure in the ISC valve system, the program proceeds to s210, and exits the routine after turning off the ECS lamp 56.

Furthermore, in s207 above, RERRHi
＞RERR ＞RERRLo If it is determined that IS
Determining that the C valve 21 is operating normally, s210
After the ECS lamp 56 is turned off, the routine is exited.

[0051] Furthermore, in the above s207, RERRHi ≦
RERR, it is determined that the ISC valve 21 is not closed as specified, and in order to avoid runaway, the ECS lamp 56 is turned on in s211 without determining the sonic choke condition (at the same time, the corresponding address in the backup RAM 40 is After warning the driver of the failure of the ISC valve 21, proceed to s212 and immediately set the fuel cut flag FLGFC (FL
GFC ← 1, fuel cut) and then exits the routine.

On the other hand, in the above s201, the idle switch O
It is determined that FF (throttle valve 11 is open) and s2
Proceeding to step 13, the delay counter N is reset (N←0
), in s214, the fuel cut flag FLGFC is reset (FLGFC←0, fuel injection is permitted), and then the routine exits.

Injector control routine: As shown in FIG. 3, in the flow for setting the fuel injection pulse Ti that drives the injector 12, which is executed for each cylinder at every predetermined crank angle, engine operation is controlled based on the output signals of each sensor. After detecting the state, in s301, the fuel cut flag F
It is determined whether the LGFC is set (FLGFC=1, fuel cut), and if FLGFC=1, it is due to a failure of the ISC valve 21 or deceleration driving, etc., and the fuel injection pulse width Ti is determined in s302 without calculating the fuel injection pulse width Ti. A fuel cut signal (Ti = 0) is output to the injector 12 and the routine is exited.

[0054] Even if the ISC valve 21 is out of order, the intake air amount Qa will not exceed the sonic choke air flow rate Qc.
(RERRLo≧RERR
), fuel cut (FLGF) will not cause runaway.
C=1), driving by accelerator work is ensured.

On the other hand, in the above s301, the fuel cut flag F
LGFC is reset (FLGFC=0, fuel injection permitted)
If it is determined that
Then, a drive pulse corresponding to this fuel injection pulse width Ti is outputted to the cylinder corresponding to fuel injection at a predetermined timing, and the routine is exited.

In this way, in this embodiment, a failure of the ISC valve 21 is always diagnosed when the throttle valve 11 is fully closed (the idle switch 20b is ON), so high reliability and safety can be obtained. Can be done.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, the ISC valve may be driven by a motor type or a negative pressure type.

[0058] In addition, if the ISC valve 21 fails while it is fully open, the engine is equipped with a fail-safe function that cuts fuel intermittently, regulates the upper limit of engine speed, and ensures minimum running speed. You may also do so.

[0059]

[Effects of the Invention] As explained above, according to the present invention,
When the throttle valve is fully closed, the sonic choke air flow rate is determined according to the ISC valve opening degree using the flow control signal energized to the ISC valve as a parameter, and then this sonic choke air flow rate and the intake air flow rate detected by the intake air amount sensor are calculated. If the comparison value of both flow rates is outside the preset allowable range, it is determined that the above ISC valve is malfunctioning, so it is of course possible to detect electrical abnormalities such as disconnection or short circuit in the harness. About IS
Excellent effects such as being able to accurately detect mechanical and electrical inoperability of the C-valve itself with a simple method are achieved.

[Brief explanation of drawings]

[Fig. 1] Flowchart showing the control procedure of the ISC valve

[Figure 2] Flowchart showing the failure determination procedure of the ISC valve

[Figure 3] Flowchart showing the injector control procedure

[Figure 4] Conceptual diagram of sonic choke air flow map

[Figure 5]
Conceptual diagram of engine control system

[Figure 6] Circuit configuration diagram of control device

[Figure 7] Longitudinal cross-sectional view of ISC valve

[Figure 8] VIII-VIII cross-sectional view in Figure 7

[Explanation of symbols]

11... Throttle valve 21...ISC valve Qc...sonic choke air flow rate Qa...Intake air flow rate RERR...Comparison value

Claims (1)

[Claims] [Claim 1] When the throttle valve is fully closed, the sonic choke air flow rate is determined according to the ISC valve opening using the flow control signal energized to the ISC valve as a parameter, and then this sonic choke air flow rate and the intake air amount sensor are used to detect the sonic choke air flow rate. A failure diagnosis method for an ISC valve in an engine, characterized in that the flow rate of intake air is compared with the flow rate of intake air, and if the comparison value of both flow rates is out of a preset tolerance range, it is determined that there is a failure in the ISC valve system.