JP2001173521A - Flow control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extremely accurately obtain a differential pressure between an exhaust pressure sensor 15 and a boost pressure sensor 27. SOLUTION: During a time between the ON-state of a key switch and the ON-state of a starter switch, a differential pressure between the detecting value Pegr of the exhaust pressure sensor 15 and the detecting value Pb of a boost pressure sensor 27 is calculated as a learning value, and a detecting deviation state inherent to an exhaust pressure sensor 15 and a boost pressure sensor 27 is grasped. The differential value Pb between the detecting value Pegr of an exhaust pressure sensor 15 during operation of an engine 1 and the detecting value Pb of a boost pressure sensor 27 is corrected as a learning value. A differential pressure is detected in a state that a detection deviation state inherent to the pressure sensors is added, and a differential pressure between the detecting values of the exhaust pressure sensor 15 and the boost pressure sensor 27 is obtained and an EGR valve 22 is controlled extremely accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device for an internal combustion engine that controls a flow control valve based on a detection value of a pressure sensor provided upstream and downstream of a flow control valve.

[0002]

2. Description of the Related Art In an internal combustion engine, emission of harmful components of exhaust gas is minimized by appropriately controlling an excess air ratio. Since the excess air ratio is controlled by changing the air-fuel ratio, the intake air amount is changed to optimize the excess air ratio. For example, in a diesel engine, the excess air ratio is controlled by controlling the amount of exhaust gas mixed into an intake passage (EGR amount) by using an EGR valve (and using an intake valve if necessary). Thus, nitrogen oxides (NO _X) and suspended particulate matter (PM) can be suppressed to a minimum.

For example, conventionally, as disclosed in Japanese Patent Application Laid-Open No. H10-115259, EG is detected by detecting intake pressure.
A device that estimates an R flow rate and diagnoses whether the EGR flow rate is optimal is known. By applying the conventional device, the EGR flow rate is optimally controlled and the opening and closing control of the EGR valve is performed, so that the excess air ratio can be optimized and the exhaust gas performance can be improved. However, JP 10-1
The method of estimating the EGR flow rate disclosed in Japanese Patent No. 15259 is based on the detected value of the intake pressure during the EGR operation and the estimated value of the intake pressure corresponding to the time when the EGR is stopped. There is. In contrast, the intake pressure and E
There is also a method of estimating the EGR flow rate based on the pressure difference from the pressure upstream of the GR valve, and there is a possibility that the accuracy can be further improved by using this method.

[0004]

The region where the control of the EGR amount is desired is a low load region, but in the low load region, the differential pressure between the intake pressure and the exhaust gas pressure is extremely small.
On the other hand, in the low load region, the EGR valve is almost fully opened, and in such a state, the pressure change with respect to the flow rate change is very small. For this reason, based on the differential pressure, EG
In order to accurately control the R amount, it is necessary to detect the intake pressure and the exhaust gas pressure extremely accurately.

[0005] However, even if the pressure sensor is expensive, there is some detection tolerance. Therefore, since the opening / closing control of the EGR valve is performed with an error even in the tolerance range, the flow rate of the introduced exhaust gas greatly changes, and it is very difficult to accurately control the EGR amount. there were.

The present invention has been made in view of the above circumstances, and controls the flow control valve based on the detection values of pressure sensors provided upstream and downstream of the flow control valve, that is, controls the flow of the fluid passing through the flow control valve. An object of the present invention is to provide a flow control device for an internal combustion engine that can accurately control a flow rate.

[0007]

In order to achieve the above object, according to the present invention, the detection values of the upstream pressure sensor and the downstream pressure sensor are measured between the time when the key switch is turned on and the time when the starter switch is turned on. The differential pressure is calculated as a reference pressure value to determine the detection deviation state unique to the upstream pressure sensor and the downstream pressure sensor, and the differential pressure between the detection values of the upstream pressure sensor and the downstream pressure sensor during operation of the internal combustion engine is used as the reference pressure value. In this way, the differential pressure is detected in a state in which the detection deviation state unique to the pressure sensor is taken into account, and the differential pressure between the detected values of the upstream pressure sensor and the downstream pressure sensor is obtained very accurately to control the flow control valve.

When calculating the reference pressure value, it is preferable to use the average of a plurality of measured values. If the starter switch is turned on until the reference pressure value can be calculated by averaging the plurality of measured values. , It is preferable to apply the previous reference pressure value. When calculating the reference pressure value, it is preferable to use the average of a plurality of measured values.

More specifically, the upstream pressure sensor is an exhaust pressure sensor provided in an EGR passage that joins the intake passage, and the downstream pressure sensor is a boost pressure sensor provided downstream of the junction of the EGR passage. The control valve is EG
This is an EGR valve provided at the junction of the R passage. Then, as an example, it is preferable to apply the present invention to a device that controls an EGR valve by controlling the EGR valve based on a differential pressure between detection values of a boost pressure sensor and an exhaust pressure sensor to improve exhaust gas performance.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration of an internal combustion engine (diesel engine) provided with a flow control device according to an embodiment of the present invention. FIG. 3 shows a control flowchart of the flow control means.

As shown in FIG. 1, a combustion chamber 2 is formed in each cylinder of a diesel engine (engine) 1, and an intake port 3 opened and closed by an intake valve 11 is provided for each combustion chamber 2. An intake passage 4 is connected to the intake port 3, and outside air is sucked into the intake passage 4 via an air cleaner 5, a supercharger 6 and an intercooler 7 (white arrows in the figure),
Outside air is introduced from the intake passage 4 into the combustion chamber 2. Also, an exhaust port 9 opened and closed via an exhaust valve 12 for each combustion chamber 2
The exhaust port 9 is connected to the exhaust passage 8. The exhaust passage 8 is connected to the supercharger 6, and the exhaust gas is discharged to the outside via the catalyst 10 after the supercharger 6 rotates to supercharge the intake air (black arrows in the figure).

The intake passage 4 and the exhaust passage 9 are connected to the EGR passage 2
The EGR passage 21 is opened and closed by an EGR valve 22 as a flow control valve, and an appropriate amount of exhaust gas is mixed into the intake passage 4. By mixing exhaust gas into the intake passage 4, the excess air ratio is appropriately controlled, and the nitrogen oxides (NO
_X ) and suspended particulate matter (PM) are minimized.

The intake passage 4 downstream of the EGR valve 22
Is provided with an intake air temperature sensor 25 for detecting an intake air temperature and a boost pressure sensor 27 as a downstream pressure sensor for detecting an intake pressure Pb via a boost pressure hose 26. Further, a crank angle sensor 28 that detects the crank angle of the engine 1 and detects the engine speed Ne is provided.
Information detected by the intake air temperature sensor 25, the boost pressure sensor 27, and the crank angle sensor 28 is input to the ECU 29. Accelerator opening (APS) information is input to the ECU 29. Based on the information, a control signal is sent from the ECU 29 to the electronic governor 31 and the timer control valve 32 of the fuel injection pump 30 to control the fuel injection amount. It has become so.

Further, the pressure of the exhaust gas is
An exhaust pressure sensor 15 is provided as an upstream pressure sensor for detecting Pegr.
It is input to U29. The intake pressure Pb detected by the boost pressure sensor 27 and the pressure Pe detected by the exhaust pressure sensor 15
The EGR valve 22 is controlled to open and close based on the differential pressure of the gr.
The flow rate of exhaust gas introduced from the R passage 21 into the intake passage 4 is optimally controlled (flow control means). That is, the exhaust gas flow rate (EGR flow rate) can be accurately obtained from the differential pressure and the opening degree of the EGR valve 22 by calculation or referring to a map, and the obtained exhaust gas flow rate is used to realize the target excess air ratio. The opening degree of the EGR valve 22 is feedback-controlled so as to reach the target exhaust gas flow rate.

[0015] Pressure sensors have their own detection tolerances,
The detection tolerance exists even for an expensive sensor. As shown in FIG. 2, the reference sensor output
When the relationship between (V) and the pressure (mmHg) is in a state indicated by a solid line, for example, the boost pressure sensor 27 has a detection characteristic in a dashed line state, and for example, the exhaust pressure sensor 15 has a detection characteristic in a state indicated by a dotted line. Suppose that we have Then, the variation width S of the two sensors exists in a mesh-like range. At the position of the reference pressure value A, the output value of the boost pressure sensor 27 is Pb (0), and the output value of the exhaust pressure sensor 15 is
Pegr (0). For this reason, when calculating not the absolute pressure value but the differential pressure value of the two pressure sensors, Pb (0) and Pegr
If the differential pressure value (learning value) of (0) is known, the differential pressure between the actual output value Pb of the boost pressure sensor 27 and the output value Pegr of the exhaust pressure sensor 15 is corrected by the learning value, An accurate differential pressure can be obtained irrespective of the detection tolerance.

Therefore, the ECU 29 detects the pressure Pegr detected by the exhaust pressure sensor 15 and the pressure detected by the boost pressure sensor 27 between the time when the key switch of the engine 1 is turned on and the time when the starter switch is turned on. And has a function of calculating a differential pressure from the intake pressure Pb as a reference pressure value (learning value). Further, the ECU 29 has a correction function for correcting the differential pressure between the pressure Pegr detected by the exhaust pressure sensor 15 and the intake pressure Pb detected by the boost pressure sensor 27 by a learning value when the engine 1 is operating. I have.

That is, during the period from the time when the key switch of the engine 1 is turned on to the time when the starter switch is turned on, the differential pressure of the inherent misalignment between the boost pressure sensor 27 and the exhaust pressure sensor 15 is determined by the reference pressure value. (Learning value), and the differential pressure between the boost pressure sensor 27 and the exhaust pressure sensor 15 when the engine 1 is operating is detected with the learning value taken into account. This makes it possible to extremely accurately obtain the differential pressure between the detection values of the boost pressure sensor 27 and the exhaust pressure sensor 15 without being affected by the variation in the detection tolerance inherent to the sensor. The gas flow can be obtained.

The flow control means will be described in detail with reference to FIG.

As shown in the figure, it is determined in step S1 whether or not the IG switch (key switch) is on. If it is determined in step S1 that the IG switch is on, the starter switch is turned on in step S2. It is determined whether the switch is on. If it is determined in step S1 that the IG switch is not on, the determination in step S1 is repeated until the IG switch is turned on.

If it is determined in step S2 that the starter switch is not on, that is, if it is determined that the time period is from when the key switch of the engine 1 is on to when the starter switch is on, The pressure Pegr detected by the pressure sensor 15 and the intake pressure Pb detected by the boost pressure sensor 27 are sampled in step S3,
In step S4, the number of sampling points is N (for example, 5 points).
Is determined. If it is determined in step S4 that the number of sampling points is less than N, the processing of steps S3 and S4 is repeated until the number of sampling points becomes N.

If it is determined in step S4 that sampling at N points has been completed, the pressure Pegr at N points is determined in step S5.
And an intake pressure Pb are averaged to obtain an average pressure aPegr and an average intake pressure aPb. In step S6, average pressure aP
The difference between the egr and the average intake pressure aPb (aPegr-aPb) is set as a learning value, and a process using the learning value obtained this time is performed in step S7. Then, a process of turning on the starter when the starter switch is turned on is performed. On the other hand, if it is determined in step S2 that the starter switch is on, a process of using the previous learning value is performed in step S8, and a process of turning on the starter is performed.

In this embodiment, since it is assumed that the starter switch is turned on after the IG switch is turned on, even if a predetermined time has elapsed after the IG switch is turned on. If the starter switch is not turned on, the process of calculating the learning value is cancelled. If the starter switch is turned on during the processing from step S3 to step S7, step S is forcibly performed.
8 is performed.

That is, when calculating the learning value, the average value of the N measurement values is used, and when the starter switch is turned on until the learning value can be calculated based on the average value of the N measurement values. , The previous learning value is applied.

After the learning value is calculated by the above-described processing and the starter is turned on, the ECU 29 determines the pressure Pegr detected by the exhaust pressure sensor 15 and the intake air detected by the boost pressure sensor 27 when the engine 1 is operating. The differential pressure from the pressure Pb is corrected by the learning value and calculated. That is, engine 1
The differential pressure DEP between the pressure detected by the exhaust pressure sensor 15 and the pressure detected by the boost pressure sensor 27 during the operation of is calculated by DEP = Pegr−Pb− (learning value).

That is, the differential pressure DEP between the boost pressure sensor 27 and the exhaust pressure sensor 15 during the operation of the engine 1 is detected in a state in which the learning value is added, and is extremely accurate without being affected by the variation in the detection tolerance inherent in the sensor. The differential pressure between the values detected by the boost pressure sensor 27 and the exhaust pressure sensor 15 can be obtained. Then, by controlling the EGR valve 22 based on the differential pressure between the detection values of the boost pressure sensor 27 and the exhaust pressure sensor 15, it becomes possible to obtain an appropriate exhaust gas flow rate with excellent exhaust gas performance. Therefore, a very accurate differential pressure can be obtained without increasing the cost, and the optimal control of the EGR valve 22 can be performed.

In the above embodiment, the boost pressure sensor 2
The case where the EGR valve 22 is controlled by the differential pressure between the exhaust gas pressure sensor 7 and the exhaust pressure sensor 15 has been described. For example, the flow rate control valve is controlled by the differential pressure between the boost pressure sensor 27 and the atmospheric pressure sensor to control the fluid flow rate. In some cases, for example, the present invention can be applied to control of other flow control valves.

Another embodiment of the flow control means will be described in detail with reference to FIG. FIG. 4 shows a control flow chart of the flow control means according to another embodiment.

In the example shown in FIG. 4, when the learning value is calculated, the starter is turned on under the condition that the learning value can be calculated by averaging the plurality of measurement values and using the average of the plurality of measurement values. It is becoming. That is, even if the starter switch is turned on, the starter does not turn on unless the process for turning on the starter is executed. In the present embodiment, since the processing from step S1 to step S6 is the same as the processing shown in FIG. 3, the same processing is denoted by the same step number and redundant description is omitted.

In step S6, the differential pressure (aPegr-aPb) between the average pressure aPegr and the average intake pressure aPb is set as a learning value, and in step S11, a learning end flag is turned on. Then, in step S12, it is determined whether or not the learning end flag is turned on. If it is determined in step S12 that the learning end flag is turned on, a process of using the learning value obtained this time in step S13. Perform Then, when the starter switch is turned on, a process of turning on the starter is performed in step S14.

At this time, since it is assumed that the starter switch is turned on after the IG switch is turned on, the starter switch is turned on even if a predetermined time has elapsed after the IG switch is turned on. If not, the process of calculating the learning value is cancelled.

If it is determined in step S12 that the learning end flag has not been turned on, the process proceeds to step S3 and the process is repeated until the learning end flag is turned on. On the other hand, when it is determined in step S2 that the starter switch is on, the process proceeds to step S12, and it is determined whether the learning end flag is on. Then, when the learning end flag is turned on, the processing shifts to steps S13 and S14 to turn on the starter.

That is, when calculating the learning value, the average value of the N measurement values is used, and the starter is turned on under the condition that the learning value has been calculated based on the average value of the N measurement values. Has become.

After calculating the learning value by the above processing,
In the ECU 29, as described above, when the engine 1 is operating, the differential pressure DEP between the pressure Pegr detected by the exhaust pressure sensor 15 and the intake pressure Pb detected by the boost pressure sensor 27 is DEP.
= Pegr-Pb-(learning value), and the state is corrected by the latest learning value. Therefore, it is possible to obtain an extremely accurate differential pressure without increasing the cost while always taking the latest learning value into account, and the optimal control of the EGR valve 22 becomes possible.

[0034]

According to the flow control device for an internal combustion engine of the present invention, the differential pressure between the detection values of the upstream pressure sensor and the downstream pressure sensor is determined between the time when the key switch is turned on and the time when the starter switch is turned on. Calculate as a reference pressure value to grasp the detection deviation state unique to the upstream pressure sensor and the downstream pressure sensor, and correct the differential pressure between the detection values of the upstream pressure sensor and the downstream pressure sensor during operation of the internal combustion engine with the reference pressure value. With this configuration, the differential pressure can be detected in a state in which a detection deviation state unique to the pressure sensor is added. As a result, it is possible to control the flow control valve by obtaining the pressure difference between the detection values of the upstream pressure sensor and the downstream pressure sensor extremely accurately without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an internal combustion engine (diesel engine) provided with a flow control device according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between sensor output and pressure.

FIG. 3 is a control flowchart of a flow control unit.

FIG. 4 is a control flowchart of a flow rate control unit according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine (engine) 3 Intake port 4 Intake passage 5 Air cleaner 6 Supercharger 15 Exhaust pressure sensor 22 EGR valve 26 Boost pressure hose 27 Boost pressure sensor 29 ECU

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/06 355 F02D 41/06 355 (72) Inventor Setsuo Nishihara 33-3, Shiba 5-chome, Minato-ku, Tokyo No. Mitsubishi Motors Industry Co., Ltd. (72) Inventor Megumi Shinegahara 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd. (72) Michihiro Hata 5-33-8 Shiba, Minato-ku, Tokyo No. Mitsubishi Motors Corporation F-term (reference) 3G062 AA01 AA05 BA04 GA04 GA06 GA14 GA16 GA22 3G092 AA02 AA17 AA18 BA04 DC09 EB04 EC01 EC05 EC09 FA06 FA50 HA01X HA04Z HA05Z HA16Z HD07X HD08Z HE01Z HE03Z11G01HA02 HA19Z19 MA01 NA01 NC02 ND22 ND29 NE23 PA01A PA07Z PA09Z PA10Z PA16Z PD14Z PD15A PE01Z PE03Z PF16Z

Claims (1)

[Claims] A flow control valve provided in an intake system or an exhaust system of an internal combustion engine; an upstream pressure sensor disposed upstream of the flow control valve for detecting a fluid pressure on an upstream side of the flow control valve; A downstream pressure sensor disposed downstream of the flow control valve to detect a fluid pressure on the downstream side of the flow control valve; and the flow control valve based on a pressure difference between the upstream pressure sensor and the pressure detected by the downstream pressure sensor. Flow rate control means for controlling the differential pressure between the detected values of the upstream pressure sensor and the downstream pressure sensor during a period from when the key switch is turned on to when the starter switch is turned on. As a reference pressure value, and a correction function for correcting the differential pressure between the detection values of the upstream pressure sensor and the downstream pressure sensor with the reference pressure value when the internal combustion engine is operating. Especially An internal combustion engine flow control device.