JPH0569981B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for an engine that recirculates a portion of exhaust gas from the exhaust system to the intake system to suppress the generation of NOx. It is something.

(Prior art) Generally, in an exhaust gas recirculation system, when part of the exhaust gas is recirculated from the exhaust system to the intake system through the recirculation passage, an EGR valve is provided in the recirculation passage to adjust the recirculation amount of the exhaust gas to the engine operation. It is controlled according to the situation. In addition, electronically controlled exhaust gas recirculation devices are being adopted for the purpose of strictly controlling the recirculation amount to always keep it to the minimum necessary amount, as the recirculation of exhaust gas has a negative effect on engine drivability, fuel efficiency, etc. It's getting old.

As an example of this electronically controlled exhaust gas recirculation system, there is one that employs a position feedback control system, as seen in Japanese Patent Laid-Open No. 107526/1983. This position feedback control is equipped with a position sensor that detects the lift value of the valve body of the EGR valve, and uses the target lift value of the EGR valve determined according to the engine operating condition and the actual measurement using the position sensor. A control signal corresponding to the difference between the lift value and the lift value is output to the EGR valve so that the two match.

However, if the position sensor that detects the lift value of the EGR valve fails, the exhaust gas recirculation control cannot be performed accurately, resulting in a decrease in emission performance due to insufficient exhaust gas recirculation, or a large amount of exhaust gas recirculation. As a result, drivability deteriorates, and problems such as poor starting and insufficient output may occur.

Therefore, in response to the above position sensor failure,
If you try to switch from position feedback to open control, that is, depending on the operating condition,
When calculating the open control amount of the EGR valve and outputting a control signal based on this control amount to the EGR valve to control exhaust gas recirculation, the position feed is used to calculate the open control amount according to the operating state. In the same way that control data corresponding to each operating state is registered in memory for back control, if open control data is separately registered in memory and the control data is switched when a failure occurs,
In addition to the overall amount of data increasing due to precise control of the entire engine, a huge memory capacity is required, which poses a major problem in implementation.

(Object of the Invention) In view of the above circumstances, the present invention provides an engine system that allows exhaust gas recirculation control to be performed appropriately with relatively high accuracy without using memory capacity more than necessary even when the position sensor fails. The purpose of this invention is to provide a control device.

(Structure of the Invention) The exhaust gas recirculation device of the present invention uses a control device having a position feedback means for controlling the EGR valve according to detection by a position sensor.
When the failure detection means detects a failure in the position sensor that detects the lift value of the EGR valve, the target lift value for position feedback calculated according to the engine operating condition is used to detect the previous lift value. A control signal corresponding to the difference from the calculated target lift value is calculated, and the control signal obtained by this calculation is output to the EGR valve to perform open control of exhaust gas recirculation. It is.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention.

A portion of exhaust gas is transferred from an exhaust passage 2 connected to the engine 1 to an intake passage 4 downstream of a throttle valve 3.
A recirculation passage 5 for recirculating exhaust gas is provided, and an EGR valve 6 for controlling the recirculation amount of exhaust gas by movement of a valve body 7 is interposed in this recirculation passage 5. This EGR valve 6
A position sensor 8 is attached to detect the lift value of the valve body 7. And the above EGR valve 6
The amount of movement (lift value) of the valve body 7 is controlled by a control signal from the control device 9. This control device 9
has a target lift calculation means 10 that detects the operating state of the engine 1 and calculates a target lift value of the EGR valve 6 according to the operating state, and the target lift value by the target lift calculation means 10 and the position sensor The position feedback means 11 that receives the actual lift value from EGR valve 8 outputs a control signal to the EGR valve 6 according to the difference between the two lift values so that they match.

In addition, receiving the output of the position sensor 8,
A failure detection means 12 for detecting a failure of the position sensor 8 is provided, and signals from this failure detection means 12 and the target lift calculation means 10 are outputted to the open control means 13. The lift calculation means 10 calculates a control signal according to the difference between the target lift value calculated according to the operating state of the engine and the previously calculated target lift value, and outputs this control signal to the EGR valve 6,
Open control is performed using position feedback calculation data.

(Effects of the Invention) According to the present invention, even if position feedback control of exhaust gas recirculation based on the actually measured lift value of the EGR valve is no longer possible due to a failure of the position sensor, the operating state can be maintained. By accurately performing open control based on the correspondingly calculated target lift value for position feedback,
It is possible to prevent a decrease in drivability due to a large amount of exhaust gas recirculation and a decrease in emission performance due to a small amount of exhaust gas recirculation. In addition, by using the calculation data for position feedback, there is no need for memory for control data for open control that corresponds to the operating state.
It is sufficient to have the calculation data of the control amount from the lift value, and exhaust gas recirculation control can be performed appropriately without requiring more memory capacity than necessary.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 2 is an overall configuration diagram showing a specific structural example.

The intake passage 4 that supplies intake air to the engine 1 includes
Air cleaner 15, fuel injection nozzle 1 from the upstream side
6, a throttle valve 3 is provided. In addition, the intake passage 4 downstream of the throttle valve 3
A negative pressure sensor 17 for detecting intake negative pressure is disposed.

On the other hand, the EGR valve 6, which is interposed in the middle of the recirculation passage 5 whose one end is connected to the exhaust passage 2 and the other end is connected to the intake passage 4, has a valve body 7 supported by a diaphragm actuator 18. Intake negative pressure is introduced into the negative pressure chamber 18 by a negative pressure introduction passage 19 as a source for opening the valve body 7, and the above-mentioned EGR
A three-way solenoid 20 is provided to control the introduction of negative pressure for opening into the valve 6. The control device 9 is connected to the three-way solenoid 20.
A control signal from the control unit (control unit) is output to control the amount of exhaust gas recirculation. Further, a position sensor 8 for detecting the moving position of the valve body 7 is attached to the actuator 18.

Further, a fuel supply passage 22 is connected to the fuel injection nozzle 16 to constitute a fuel supply device, and an ignition coil 24 is connected to a spark plug 23 provided in the engine 1 to constitute an ignition device.

The operation of the fuel supply device and the ignition device are also controlled by control signals from the control device 9. That is, a fuel injection pulse is output to the fuel injection nozzle 16 to inject a predetermined amount of fuel at a predetermined time, and an ignition signal is output to the ignition coil 24 to perform ignition at a predetermined time.

Each control including the exhaust gas recirculation control is performed based on the detection of the operating state of the engine, and the control device 9 includes information from the negative pressure sensor 17 in addition to the actually measured lift value from the position sensor 8. A crank angle signal from a crank angle sensor 25 is inputted to detect the engine rotational speed and reference crank angle (cylinder discrimination).

In addition, in order to perform various precise controls,
In addition to the above sensors, the throttle sensor signal detects the throttle opening, the water temperature sensor signal detects the water temperature, the _O2 sensor signal detects the supply air-fuel ratio from the exhaust component concentration, and the intake air temperature sensor signal detects the intake air temperature. A signal from an air temperature sensor, a signal from an atmospheric pressure sensor that detects atmospheric pressure, a signal from a starter switch that detects when starting, a signal from a cooler switch that detects when the cooler is in use, etc. are input as necessary.

The control device 9 has the function of the failure detection means 12 which receives a signal from the position sensor 8 and compares the signal value with a set value to detect whether or not the position sensor 8 is in a failure state. However, in the event of a failure, countermeasures are taken against the failure of the exhaust gas recirculation control, and a failure indicator lamp 26 is turned on to indicate the failure.

The internal configuration of the control device 9 is as shown in FIG.
0, the signal of the crank angle sensor 25 is inputted via the waveform shaping circuit 34, and each signal of the position sensor 8 and negative pressure sensor 17 is inputted via the A/D conversion circuit 35. be.

The main processing section 31 detects the operating state based on the intake pressure by the negative pressure sensor 17 and the engine rotation speed by the crank angle sensor 25.
The target lift value of the valve body 7 of the EGR valve 6 is compared with the actual lift value measured by the position sensor 8 to calculate the exhaust gas recirculation control amount and various control amounts for fuel injection and ignition timing. Drive circuit 3
6 to 38, control signals are output to the fuel injection nozzle 6, ignition coil 24, and three-way solenoid 20, respectively, and the position feedback is controlled.
It performs EGR control, predetermined fuel control, and ignition control.

On the other hand, the failure determination unit 32 receives the measured lift signal from the position sensor 8, determines whether or not this signal is within the range of the preset upper limit value Pmax and lower limit value Pmin, and When a failure occurs such as a short circuit or disconnection, the failure countermeasure unit 33 calculates an EGR control amount corresponding to the difference between the current and previous target lift values produced by the main processing unit 31. At that time, in areas where the amount of deviation is small,
This is a dead zone in which no control is executed. This calculated data of the EGR control amount at the time of failure is output to the main processing section 31, and the main processing section 31 performs position feedback control in place of the failure countermeasure section 3.
Based on the calculation data from No. 3, open control of exhaust gas recirculation is performed, and various controls of fuel and ignition are performed. Furthermore, when a failure occurs, an activation signal is output from the failure countermeasure unit 33 to the failure indicator lamp 26 via the EGR drive circuit 38 to indicate the failure.

Next, the operation of the control device 9 will be explained using the flowchart shown in FIG. Start with power on, initialize at step S1 (flag F,
G=0, ramp off), step S2
Various input information from the position sensor 8, negative pressure sensor 17, crank angle sensor 25, etc. is read in.

Based on this read detection data, interrupt signals 1, 2, and 3 are input at predetermined crank angles, and in response, fuel control (S3 to S5), ignition control (S6 to S8), and EGR control (S9 ~S36).

That is, it is determined in step S3 whether or not interrupt signal 1 has been output, and if it is YES, the step
In step S4, the program proceeds to a fuel control routine, where control data is calculated from a map of intake negative pressure and engine speed, and this data is output to the fuel drive circuit 36 to perform predetermined fuel injection (step S5). Also, it is determined in step S6 whether or not interrupt signal 2 has been output, and if YES, the process proceeds to the ignition control routine in step S7, calculates control data from a map of intake negative pressure and engine speed, and uses this data. The signal is output to the ignition drive circuit 37 and ignition is performed at a predetermined timing based on the signal from the crank angle sensor 25 (step
S8).

Next, in step S9, it is determined whether or not interrupt signal 3 has been output, and if YES, step S10 is performed.
Proceed to the EGR control routine that follows. First, in step S10, a target lift value for the EGR valve 6 is calculated by map interpolation between the engine speed and the intake negative pressure.
Steps S11 to S22 are a routine for detecting a failure in the position sensor 8.
Proceeding to S23, the target lift value is compared with the actually measured lift value from the position sensor 8, a signal corresponding to the difference is output to the EGR drive circuit 38, and a predetermined amount of exhaust gas recirculation is performed by position feedback. (Step S36).

In step S11, it is determined whether the failure flag F is set. When this failure flag F is set to 1, it means that a failure has occurred in the position sensor 8, and when it is reset to 0, it means that it is operating normally. When this failure flag F is 0, a negative determination is made in step S11, and the process proceeds to step S12, where a failure determination is made. That is, in step S12, it is determined whether the input signal from the position sensor 8 is greater than or equal to the upper limit value Pmax, and in step S5, it is determined whether or not it is less than or equal to the lower limit value Pmin. When the output is normal and within the standard range, a failure occurs when the output becomes YES.

Furthermore, even if the position sensor 8 output is within the reference range in steps from step S14,
This is to determine whether or not lift fluctuation of the EGR valve 6 is detected. In step S14, it is determined whether the target lift value has changed, and if it has changed (YES)
Set change flag G to 1 (step
S15), in step S16, it is determined whether this change flag G is set to 1, and when the flag is set (YES), it is determined whether the count of the subtraction timer t, which is set to the initial value in advance, has reached 0. (Step S17) If NO, the timer t is subtracted in step S22. When timer t=0 and YES, change flag G
is reset to 0 (step S18), and
After setting the timer t to the initial value (step S19), the current and previous lift values actually measured by the position sensor 8 are compared and calculated in step S20, and it is determined in step S21 whether or not the value has changed. .
The determination in step S21 is made when a predetermined time by timer t has elapsed after the target lift value has changed.
This is to determine whether there is a change in the measured lift value, and when there is a change (YES), it is normal, and when there is no change (NO), it is when a failure has occurred.

Whether the step S12 or S13 is YES or
Alternatively, when a failure occurs with step S21 being NO, the process advances to step S24 and first the failure flag F
After setting 1 to 1, the process advances to step S25. In step S25, it is determined whether or not the target lift value calculated in step S10 is 0. If 0 (YES), the control amount is set to 0 in step S26. When the target lift value is NO other than 0, the difference between the current target lift value and the previous target lift value is calculated in step S27, and it is determined whether or not this difference is within the dead zone (step S28). If (YES), the previous control amount is held in step S29. On the other hand, if the determination in step S28 is NO and it is outside the dead zone, a control amount corresponding to the above difference is determined (step S30). Boost correction of this control amount is performed (step S31). This boost correction is based on EGR
Since the source for opening the valve body 7 in the valve 6 is the intake negative pressure, the lift amount of the valve body 7 changes depending on the magnitude of the negative pressure. , the control amount is corrected to a smaller value.

Next, in step S32, it is determined whether or not the above difference is in the positive direction, that is, whether the exhaust gas recirculation amount (lift amount) is to be increased or decreased.If it is in the positive direction, the difference is added to the previous control amount in step S33. The determined control amount is added and set, while in the negative direction, the control amount determined by the difference is subtracted from the previous control amount in step S34 and set. After outputting a signal to turn on the failure indicator lamp 26 (step S35), the process advances to step S36.
EGR open control output is performed based on the control amount set in steps S26, S29, S33, or S34.

When this failure occurs, the failure flag F is set to 1, so the determination in step S11 becomes YES, and the open control in steps S25 to S35 is continued until the power is turned off, and then again at the next power on. Performs failure determination.

Therefore, the calculated data of the target lift value in step S10 can be used as is in both normal conditions and when a failure occurs, and measures against failure of the position sensor 8 can be realized without increasing the control amount map in EGR control. be.

The above EGR control and other controls are as follows:
Only basic matters are explained, and detailed corrections are further executed based on various detection data for this control.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing the configuration of the present invention, FIG. 2 is an overall configuration diagram showing a specific configuration example of the invention, FIG. 3 is a block diagram showing the internal configuration of the control device, and FIG. The figure is a flow chart explaining the operation of the control device. 1...Engine, 2...Exhaust passage, 4...Intake passage, 5...Recirculation passage, 6...EGR valve, 7...
Valve body, 8...Position sensor, 9...Control device, 10...Target lift calculation means, 11...Position feedback means, 12...Failure detection means, 13...Open control means, 18... ...actuator, 20...three-way solenoid.

Claims (1)

[Claims] 1. An EGR valve that is installed in a recirculation passage that takes out a portion of exhaust gas from the exhaust system and recirculates it to the intake system, and controls the amount of recirculation of exhaust gas by moving a valve body, and the above-mentioned
A position sensor that detects the lift value of the valve body of the EGR valve, a target lift calculation means that detects the operating state of the engine and calculates a target lift value of the EGR valve according to the operating state, and a target by the target lift calculation means. EGR sends a control signal according to the difference between the lift value and the actual lift value measured by the above position sensor.
An exhaust gas recirculation device for an engine, comprising a control device having a position feedback means for outputting an output to a valve and controlling the two so that the two coincide, the control device receiving an output from the position sensor. failure detection means for detecting a failure of the position sensor; receiving outputs from the failure detection means and the target lift calculation means; and when the position sensor fails, the target lift calculation means calculates a value corresponding to the operating state of the engine; The control signal corresponding to the difference between the target lift value and the previously calculated target lift value is transmitted to the EGR.
An exhaust gas recirculation device for an engine, comprising: an open control means for outputting output to a valve.