JPH04252849A - Exhaust gas recirculation valve controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To restrain the worsening of emission caused by a variation in exhaust gas recirculation rate due to back pressure fluctuations and so on. CONSTITUTION:This controller is provided with a back-pressure sensor 17 installed at the upstream of an EGR valve 5, two means 18, 19 detecting engine speed and load either, a means 11 controlling the EGR valve 5 for its on-off operation into the desired determined by the engine speed and load, a means 11b storing a reference back-pressure valve conformed to the engine load and speed, and another means 11b compensating the desired opening of the EGR valve in conformity with a deviation between this reference back-pressure valve and a back-pressure value out of the back-pressure sensor, respectively.

Description

[0001] The present invention relates to an EGR valve control device for an internal combustion engine, and in particular, to an EGR valve control device that is characterized by a method of correcting the EGR opening degree.
This invention relates to a GR valve control device. [Prior Art] EG is used to recirculate exhaust gas to the intake pipe.
Various EGR valve control devices have been proposed in the past to control the opening degree of the EGR valve disposed in the R pipe. A system has been disclosed that detects this negative pressure and the pressure upstream of the EGR pipe, and determines a failure of the EGR or the like based on the pressure signals of both. Problem to be Solved by the Invention In the above device, for example, back pressure changes in the EGR pipe due to collection and regeneration of diesel particulate filters (D, P, F,) installed in the exhaust pipe. It was also possible to detect abnormalities in the EGR rate due to an increase in back pressure due to carbon accumulation in the exhaust pipe, a decrease in EGR gas passage area due to carbon accumulation in the EGR valve, etc. However, it is not possible to correct the EGR valve opening degree to suppress fluctuations in the EGR rate due to changes in back pressure or decreases in the EGR rate due to carbon deposition on the EGR valve.
There was a problem in that the R rate was not properly controlled and emissions deteriorated. An object of the present invention is to improve emissions by suppressing fluctuations in EGR rate due to changes in back pressure and the like. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an E for connecting an intake pipe and an exhaust pipe as shown in FIG.
In an internal combustion engine equipped with a GR pipe, a load detection means for detecting the load of the internal combustion engine, a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and a rotation speed detection means disposed in the EGR pipe for detecting EGR gas. an EGR valve for adjusting the amount;
EGR valve control means for opening and closing the EGR valve to a target opening determined by the load and the rotational speed; a back pressure detection means for detecting pressure on the upstream side of the EGR valve; a first storage means for storing a reference back pressure value corresponding to the rotation speed; and a first memory means for correcting the target opening according to a deviation between the back pressure value from the back pressure detection means and the reference back pressure value. The present invention proposes an EGR valve control device for an internal combustion engine, characterized in that it is equipped with a correction means. Furthermore, a reference deviation between the back pressure at a first opening of the EGR valve and the back pressure at a second opening different from the first opening is determined based on the load and the rotation speed. a second storage means for storing data in correspondence with each other; a first control means for forcibly controlling the EGR valve to the first opening degree; and a first control means for controlling the EGR valve to the first opening degree. a second control means for controlling the EGR valve to the second opening degree after the EGR valve is controlled to the second opening degree; and when the EGR valve is controlled to the first opening degree by the first control means. calculating means for calculating a deviation between the back pressure of the EGR valve and the back pressure when the EGR valve is controlled to the second opening degree by the second control means, and comparing this deviation with the reference deviation. The present invention also proposes an EGR valve control device for an internal combustion engine, characterized by comprising a comparison means and a second correction means for correcting the target opening degree so as to increase it in accordance with the comparison result of the comparison means. [Operation] As a result, when carbon etc. accumulate in the exhaust pipe and the back pressure increases, the deviation between this back pressure and the reference back pressure stored in the first storage means increases, and this deviation increases. The target opening degree of the EGR valve is corrected according to the
Fluctuations in R rate are prevented. Furthermore, the EGR valve is forcibly controlled from the first opening degree to the second opening degree, and the amount of fluctuation in back pressure at this time and the second opening degree are controlled.
The target opening degree of the EGR valve is corrected to increase the target opening degree of the EGR valve according to the comparison result, and the EGR rate is increased due to the reduction in the EGR gas passage area due to carbon deposition on the EGR valve. fluctuations are prevented. [Embodiments] Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 2 is a block diagram showing the overall configuration of an embodiment of the present invention, in which an exhaust manifold 2 for discharging exhaust gas and an intake manifold 3 for taking in intake gas are attached to the engine 1. This intake manifold 3
A throttle valve 15 that is connected to an accelerator pedal (not shown) for adjusting the amount of intake air is provided at the collecting portion. Reference numeral 4 denotes a recirculation passage (hereinafter E) for recirculating exhaust gas from the exhaust manifold 2 to the intake manifold 3.
This EGR pipe 4 is provided with an EGR valve 5 for adjusting the amount of EGR gas. 6
is an exhaust pipe for discharging exhaust gas discharged from the exhaust manifold 2 to the outside. In the middle of this exhaust pipe 6 is a diesel particulate filter 7 (for collecting particulates in the exhaust gas).
(hereinafter referred to as D, P, F) are arranged. This D,P
, F, and 7 are embedded with heating wires, and as the collection of particulates progresses and the back pressure increases, the heating wires burn the particulates (regeneration). 8 is a vacuum pump for generating negative pressure, and the negative pressure from the vacuum pump 8 is passed through a negative pressure passage 9 to an electronic negative pressure regulating valve 10 (hereinafter referred to as E-VR).
(written as V). 11 is a well-known RAM 11a,
Electronic control unit (hereinafter referred to as EC) consisting of ROM11b etc.
It outputs a duty signal (500Hz) to the E-VRV 10 in order to control the opening degree of the EGR valve 5 (negative pressure in the diaphragm chamber 12a) according to the operating state (details will be described later). . The E-VRV 10 adjusts the negative pressure from the vacuum pump 8 according to the duty ratio of this duty signal, and supplies the adjusted negative pressure to the diaphragm 12 via the diaphragm passage 13. The diaphragm 12 then adjusts the opening degree of the EGR valve 5 according to the supplied negative pressure. The diaphragm 12 also has a diaphragm chamber 1.
Negative pressure sensor 14 that detects the negative pressure of 2a (EGR valve negative pressure)
An EGR valve negative pressure signal from this negative pressure sensor 14 is input to the ECU 11. Reference numeral 16 indicates an intake pressure sensor for detecting the pressure within the intake manifold 13, that is, intake pressure. Reference numeral 17 indicates a back pressure sensor disposed in the middle of the EGR pipe 4. This back pressure sensor 17 is for measuring back pressure changes due to collection and regeneration of particulates D, P, F, and 7. ECU
In addition to the negative pressure signal, intake pressure signal, and back pressure signal from these sensors, signals from an engine rotation speed sensor 18 and an accelerator opening sensor 19 are also input to 11. [0014] Furthermore, in the ROM 11b of the ECU 11, the EGR data before particulate collection (when new), which has been obtained through experiments in advance, is stored in a two-dimensional map of engine speed and accelerator opening.
Valve negative pressure (reference EGR negative pressure), back pressure (reference back pressure), and intake pressure (reference intake pressure) are stored. And the E.C.U.
11 calculates a target EGR valve negative pressure based on the signals from the intake pressure sensor 16 and the back pressure sensor 17 and the reference pressure, and further calculates the EGR valve negative pressure from the negative pressure sensor 14 and the target EGR valve negative pressure.
The EGR valve negative pressure is compared with the R valve negative pressure, and feedback control is performed so that the EGR valve negative pressure becomes the target EGR valve negative pressure. The method of calculating the target EGR valve negative pressure (PMF), which is the gist of the present invention, will be explained below with reference to FIG. This calculation routine is executed at predetermined intervals, for example, every 60 ms. First, in step S10, the engine rotation speed sensor 1
8 and the signals from the accelerator opening sensor 19, the engine rotation speed Ne and the accelerator opening THA are calculated. Next, in step S20, the reference EGR valve negative pressure PSF, reference back pressure PSB, and reference intake pressure PSQ corresponding to the engine speed Ne and accelerator opening THA calculated in step S10 are stored in a two-dimensional map stored in the ROM 11b. Calculate from Then, in step S30, the intake pressure PQ is calculated based on the signal from the intake pressure sensor 16,
Furthermore, the back pressure PB is calculated based on the signal from the back pressure sensor 17. Since the back pressure PB pulsates greatly as shown in FIG. 4, for example, 37 samples are sampled during one rotation of the engine, and the average value for each rotation is taken as the back pressure PB. Returning to FIG. 3, once the intake pressure PQ and back pressure PB are calculated as described above, the process proceeds to step S40. In step S40, the target EGR valve negative pressure PMF is calculated using the following arithmetic expression. [Equation 1] PMF=(PSF-PF1) {(PSB-P
SQ)/(PB-PQ)}K +PF1-
{(PB-PQ)-(PSB-PSQ
)}/N...(1) To explain the above calculation formula in detail, the constant PF in the first term of formula (1)
1 is set to the EGR valve negative pressure value when the EGR valve 5 starts to open. In this embodiment, as shown in FIG. 5, the EGR valve negative pressure at which the EGR valve 5 starts to open is 24 (KPa), so the constant P
F1 is set to 24. Further, the EGR gas flow rate Q is proportional to the product of the flow path area S of the EGR pipe 4 and the square root of the deviation between the back pressure PB and the intake pressure PQ, and is expressed by the following equation. [Equation 2]Q∝S・(PB −PQ )1/2 Therefore, theoretically, the multiplier K in equation (1) is 1/2, but the back pressure P
In reality, it is not necessarily 1/2 due to the influence of the pulsation of B, the mounting position of the back pressure sensor 17, etc., and the multiplier K is determined through experiments. [0022] The third term of equation (1), ie, [Equation 3] {(PB - PQ ) - (PSB - PSQ)}
/N is D, P, F, 7. When the back pressure PB increases due to an increase in exhaust resistance due to collection of particulates, the EGR valve 5 is pushed up by the increase in back pressure PB as shown in Fig. 6, and the EGR gas is released. EGR due to larger passage area
This is a correction term to prevent the rate from increasing. By the way, the denominator N is the diaphragm chamber 12a.
The area ratio between the cross-sectional area S1 of the EGR valve 5 and the area S2 of the EGR valve 5, S1 and S2, is determined as follows. [Formula 4] S1 = π×(72/2)2 [Formula 5] S2 =π×(18/2)2 Therefore, the area ratio S
Since 2 /S1 is 16, the denominator N is set to 16. In this way, the value (
By reducing the target EGR valve negative pressure by the correction term), an increase in passage area due to an increase in back pressure PB is suppressed. FIG. 7 shows the emission output state when the EGR valve negative pressure PF is controlled so as to reach the target EGR valve negative pressure PMF calculated as described above. In FIG. 7, the prior art is a case where the target EGR valve negative pressure is determined only by the engine speed and engine load. As is clear from the figure, in the past, the EGR rate increased as the back pressure increased, resulting in an increase in hydrocarbon emissions and worsening emissions, but in this example, the back pressure increases due to particulate collection. As the pressure increases, the target EGR valve negative pressure is reduced and the opening degree of the EGR valve 5 is reduced, so the EGR rate is kept constant and the amount of hydrocarbon emissions is kept low. Next, a method for correcting the decrease in the EGR rate due to the decrease in the EGR gas passage area due to the accumulation of carbon or the like in the EGR valve 5 will be explained. When carbon etc. accumulate on the EGR valve 5, the passage area of the EGR gas decreases. Therefore, when the opening degree of the EGR valve 5 is changed by a certain amount, the amount of change in back pressure when carbon is accumulated compared to when there is no accumulation is becomes smaller. [0029] This amount of change becomes smaller as more carbon is deposited and the passage area decreases. Also EG
The degree of change in back pressure when the opening degree of the R valve is changed by a certain amount is large immediately before the regeneration of D, P, F, and 7, as shown in Fig. 8. It is preferable to detect the degree of carbon accumulation in the EGR valve 5 from the amount of change in back pressure at this time. The specific operation will be explained below based on FIG. 9. This routine is executed immediately before the playback of D, P, F, 7 (for example, E
Playback signal is output from CU11 to D, P, F, 71
0 seconds ago). First, in step S100, the engine rotation speed sensor 18, the throttle opening sensor 19
The engine speed Ne and throttle opening THA are calculated based on the signals from the engine. In step S110, the engine speed Ne
Based on the two-dimensional map of and throttle opening THA, the back pressure PSBC when the EGR valve 5 is fully closed and the back pressure PS when the EGR valve 5 is half open when no carbon is deposited on the EGR valve 5 (when new)
The deviation from BO (PSBC - PSBO) is calculated. This deviation (PSBC - PSBO) is determined in advance by experiment for each engine speed and throttle opening, and is stored in ROM1.
It is stored in 1b. Next, in step S120, the EGR valve 5 is fully closed, and in step S130, it is determined whether a predetermined time (for example, 0.5 seconds) has elapsed. If YES, that is, the EGR valve 5 is closed.
When sufficient time has elapsed for the valve 5 to be fully closed, the process advances to step S140. If NO, the process waits in S130 until a predetermined period of time has elapsed. In step S140, the EGR valve 5
Calculate the back pressure PBC when fully closed. Next step S150
Then, the EGR valve 5 is half-opened, and in step S160 it is determined whether a predetermined time (for example, 0.5 seconds) has elapsed since the EGR valve 5 was half-opened. If YES, the process advances to step S170, and
If the answer is O, the process waits in step S160 until a predetermined period of time has elapsed. In step S170, the back pressure PBO when the EGR valve 5 is half open is detected, and in step S180, the deviation (change amount of back pressure) between the back pressure PBC when fully closed and the back pressure PBO when half open is detected.
Calculate. Then, in step S190, in order to detect how much the EGR valve 5 is clogged with carbon, the amount of change in back pressure (PSBC - PS
The ratio of (PBC-PBO)/(PSBC-PSBO) to the current amount of change in back pressure (PBC-PBO)
Calculate. In step S200, the above ratio (PBC-PBO)/(PSBC
-PSBO) is calculated. Figure 10
is a map showing the relationship between the above ratio and the correction amount ΔP when Ne is 1000 rpm and THA is 20%, and as the ratio becomes smaller, the current amount of change in back pressure (PBC-PBO)
The correction amount ΔP is set to be larger as becomes smaller than the amount of back pressure change (PSBC - PSBO) when new. [0035] As mentioned above, as more carbon accumulates, the back pressure change decreases, so if the current back pressure change is smaller, the passage area will be smaller than when it was new, and the EGR rate will decrease. In order to correct this, the correction amount ΔP is set larger as the amount of change in back pressure becomes smaller, thereby preventing a drop in the EGR rate. This correction amount Δ
In step S210, P is added to the target EGR valve negative pressure PMF determined in step S40 of FIG. 3, and this routine ends. By increasing the target EGR valve negative pressure PMF by the correction amount ΔP, the opening degree of the EGR valve 5 increases by an amount corresponding to the correction amount ΔP, thereby preventing a decrease in the EGR rate due to carbon deposition. Although the embodiment described above is an EGR valve control device equipped with a throttle valve 15 to adjust the amount of intake air, the present invention can also be applied to an internal combustion engine without a throttle valve. In this case, the target EGR valve negative pressure PMF calculated in step S40 of FIG. 3 is expressed by the following equation. [Formula 6] PMF=(PSF-PF1)・(PSB/PB)
K +PF1-(PB-PSB)/NAlso, in the above-mentioned embodiment, a method of controlling the EGR valve negative pressure in response to a change in back pressure due to collection of particulates D, P, F, and 7 was described, but the present invention Other than D, P, and F, it can also be applied to prevent fluctuations in the EGR rate due to changes in back pressure due to changes over time in catalysts and the like. Furthermore, the present invention can be applied to EGR valves other than EGR valves that operate under negative pressure (for example, those that control the passage area of EGR gas using a step motor), and in this case, the target EGR valve negative pressure PMF can be adjusted by adjusting the passage area. You can replace it with Effects of the Invention: The present invention eliminates back pressure fluctuations due to the collection and regeneration of D, P, and F, and fluctuations in the EGR rate due to back pressure increases due to carbon deposition in the exhaust pipe. prevention, and deterioration of emissions is suppressed. Furthermore, fluctuations in the EGR rate due to a decrease in the EGR gas passage area due to carbon deposition on the EGR valve are also prevented.

[Brief explanation of the drawing]

FIG. 1 is a complaint correspondence diagram.

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 3 is a flowchart used to explain the operation of the ECU 11.

FIG. 4 is an experimental result showing the change in back pressure during one rotation of the engine.

FIG. 5 is a characteristic diagram showing the relationship between EGR valve negative pressure and passage area.

FIG. 6 is an enlarged view showing the structure of the EGR valve section.

FIG. 7 is a characteristic diagram showing the relationship between back pressure and emissions.

FIG. 8 is a characteristic diagram showing the relationship between back pressure and passage area.

FIG. 9 is a flowchart used to explain the operation of the ECU 11.

FIG. 10 is a map stored in the ROM 11b.

[Explanation of symbols]

4 EGR tube 5　EGR valve 11 ECU 17 Back pressure sensor 18 Rotation speed sensor 19 Accelerator opening sensor

Claims (2)

[Claims] 1. An internal combustion engine equipped with an EGR pipe connecting an intake pipe and an exhaust pipe, comprising: load detection means for detecting a load on the internal combustion engine; and a rotation speed detection means for detecting the rotation speed of the internal combustion engine. means, an EGR valve disposed within the EGR pipe for regulating the amount of EGR gas;
EGR valve control means for controlling the opening and closing of the GR valve to a target opening determined by the load and the rotation speed;
a back pressure detection means for detecting the pressure on the upstream side of the valve; a first storage means for storing a reference back pressure value corresponding to the load and the rotation speed; and a back pressure value from the back pressure detection means. EGR for an internal combustion engine, comprising a first correction means for correcting the target opening according to a deviation from the reference back pressure value.
Valve control device. 2. A reference deviation between the back pressure at a first opening of the EGR valve and the back pressure at a second opening different from the first opening is determined based on the load and the rotation speed. a second storage means for storing data in correspondence with each other; a first control means for forcibly controlling the EGR valve to the first opening degree; and a first control means for controlling the EGR valve to the first opening degree. a second control means for controlling the EGR valve to the second opening degree after the EGR valve is controlled to the second opening degree; and a second control means for controlling the EGR valve to the first opening degree.
a calculation means for calculating a deviation between a back pressure when the EGR valve is controlled to the opening degree and a back pressure when the EGR valve is controlled to the second opening degree by the second control means; and the reference deviation, and a second correction means for correcting the target opening to increase in accordance with the comparison result of the comparison means. EGR valve control device for internal combustion engine.