Engine control device

Abstract

To alleviate a torque step by suppressing a sudden rise of engine torque in fuel cut return after performing EGR learning / diagnosis in fuel cut.SOLUTION: The calculation unit includes a required torque setting unit that sets a required torque that is an engine torque required by a driver at the time of return from fuel cut, a surplus torque setting unit that sets a surplus torque at the time of combustion based on an air flow rate passing through the EGR valve at the time of return from fuel cut, a comparison unit that compares the required torque set by the required torque setting unit with the surplus torque set by the surplus torque setting unit, and a correction torque setting unit that sets a correction torque for correcting an air amount passing through the throttle valve and an ignition timing to be based on a comparison result of the comparison unit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an engine control device that controls an engine when it returns from a fuel cut. [Background technology]

[0002] One of the systems that control engines installed in vehicles is the Exhaust Gas Recirculation device. This EGR device recirculates part of the exhaust gas into the intake air and re-burns it in the combustion chamber. This improves fuel efficiency and reduces the generation of nitrogen oxides (NOx) by suppressing the combustion temperature.

[0003] The EGR system has an EGR passage that bypasses the engine's exhaust and intake passages, and an EGR valve is installed in this EGR passage. The control unit controls the amount of EGR supplied to the intake passage by controlling the opening of the EGR valve.

[0004] If the EGR valve malfunctions or the EGR passage becomes clogged, the air-fuel ratio will be affected, resulting in unstable combustion and worsening exhaust emissions. Therefore, various technologies have been proposed to check the condition of the EGR device while the vehicle is running, diagnose EGR malfunctions (hereinafter referred to as "EGR malfunction diagnosis"), and learn about variations and aging of the EGR valve.

[0005] This EGR malfunction diagnosis and EGR learning (hereinafter referred to as "EGR learning / diagnosis") are often performed when fuel is cut off while the vehicle is running. EGR learning / diagnosis forcibly opens and closes the EGR valve during fuel cut, and detects changes in the intake air volume at that time using an intake air volume sensor and an intake manifold pressure sensor installed in the intake passage. Then, based on whether an increase or decrease in the intake air volume commensurate with the increase or decrease in the EGR volume caused by opening and closing the EGR valve is detected, it is determined whether the EGR device is functioning normally.

[0006] Fresh air is supplied to the cylinders during fuel cut. If EGR learning / diagnosis is performed in this state, only fresh air will be supplied to the intake system from the EGR passage.

[0007] During EGR learning / diagnosis during fuel cutoff, the filling efficiency increases (excess air) by the amount of EGR gas (fresh air) supplied to the cylinders. Therefore, if fuel cutoff is resumed during EGR learning / diagnosis or immediately after EGR learning / diagnosis, the excess air causes excessive engine torque (excess torque), resulting in a torque step. This torque step causes fluctuations in the longitudinal acceleration acting on the vehicle body, causing the driver to feel a torque shock.

[0008] For example, Patent Document 1 (JP 2015-158198 A) discloses a technique in which ignition timing is retarded to mitigate torque shock caused by restarting combustion when returning from a normal fuel cut. The technique also discloses a technique in which the ignition timing is retarded to be more advanced than normal when the elapsed time from the end of EGR learning / diagnosis to the return of fuel cut is short. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-158198 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the technology disclosed in Patent Document 1 sets the ignition timing by retard control to be more advanced than normal when returning from a fuel cut immediately after the EGR learning / diagnosis is completed. This causes a problem in that the engine torque rises suddenly immediately after returning from a fuel cut. The technology disclosed in Patent Document 1 makes it difficult to fundamentally eliminate the excessive torque caused by excess fresh air.

[0011] The present invention aims to provide an engine control device that can perform EGR learning / diagnosis during fuel cut, and alleviate the torque step caused by the sudden rise in engine torque when the engine returns from the subsequent fuel cut, thereby reducing the torque shock felt by the driver. [Means for solving the problem]

[0012] The present invention relates to an engine control device including an EGR valve interposed in an EGR passage that bypasses an exhaust passage and an intake passage of an engine provided with an EGR device, a fuel injection device that supplies fuel into a cylinder, an ignition device that ignites an ignition plug facing the cylinder at a predetermined ignition timing, a fuel cut recovery detection unit that detects recovery from a fuel cut, and a control unit that forcibly opens and closes the EGR valve during the fuel cut to learn / diagnose the EGR device, and that executes retard control of the ignition timing, control of the amount of air passing through a throttle valve, and control of the opening of the EGR valve when recovering from the fuel cut. The engine has a calculation unit that calculates the torque when the engine returns from the fuel cut during learning / diagnosis or after learning / diagnosis, and the calculation unit includes a required torque setting unit that sets a required torque, which is the engine torque required by the driver, when the engine returns from the fuel cut, a surplus torque setting unit that sets a surplus torque at the time of combustion based on the air flow rate passing through the EGR valve when the engine returns from the fuel cut, a comparison unit that compares the required torque set by the required torque setting unit with the surplus torque set by the surplus torque setting unit, and a correction torque setting unit that sets a correction torque that retards the amount of air passing through the throttle valve and the ignition timing based on the comparison result by the comparison unit. [Effects of the Invention]

[0013] According to the present invention, when the engine is returned from fuel cut during learning / diagnosis of the EGR device or after learning / diagnosis, the torque required by the driver when the engine is returned from fuel cut is set, the surplus torque during combustion is set based on the air flow rate passing through the EGR valve, and the amount of air passing through the throttle valve and the correction torque for retarding the ignition timing are set based on the comparison result between the required torque and the surplus torque. This torque correction allows the actual torque when the engine is returned from fuel cut to be approximately the required torque. As a result, the torque step caused by the sudden rise in engine torque when the engine is returned from fuel cut after EGR learning / diagnosis was performed during fuel cut is alleviated, and the torque shock felt by the driver can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] Schematic diagram showing the overall configuration of the engine [Figure 2] Block diagram showing the schematic configuration of an engine control unit [Figure 3] Functional configuration diagram of corrected torque / EGR secondary valve opening calculation section [Figure 4] Conceptual diagram of surplus torque table [Figure 5] Conceptual diagram of required torque map [Figure 6] Conceptual diagram of EGR secondary valve opening table DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 shows a horizontally opposed four-stroke gasoline engine as an example of an engine 1. Intake ports 2a and exhaust ports 2b are formed in cylinder heads 2 provided on left and right banks of the engine 1. A combustion chamber is formed in the cylinder head 2 by compression of a piston 3 provided in each cylinder. Furthermore, a direct injection injector 4 and an ignition plug 5 are attached to each cylinder in the cylinder head 2. The direct injection injector 4 directly injects fuel into the combustion chamber. The tip of the spark plug 5 faces the combustion chamber.

[0016] The upstream sides of the intake ports 2a formed in the left and right banks are collected via an intake manifold 6. The collected portion of this intake manifold 6 is connected to an air chamber 7a formed downstream of an intake pipe 7, which forms part of the intake passage. Furthermore, an air cleaner 8 is installed on the air intake side on the upstream side of the intake pipe 7. A throttle valve 9 is installed midway through the intake pipe 7. This throttle valve 9 is an electronically controlled throttle valve that is opened and closed by the rotation of a throttle actuator 9a.

[0017] Meanwhile, exhaust ports 2b formed in the cylinder heads 2 of the left and right banks are collected via an exhaust manifold 10. An exhaust pipe 11 serving as an exhaust passage is connected to the collecting section of this exhaust manifold 10. An exhaust purification catalyst 12 is installed downstream of the collecting section of this exhaust pipe 11. Furthermore, a GPF (Gasoline Particulate Filter) 13 is installed downstream of the exhaust purification catalyst 12 in this exhaust pipe 11. The exhaust purification catalyst 12 purifies harmful gas components in the exhaust gas. The GPF 13 collects PM (Particulate Matter) contained in the exhaust gas. Furthermore, a muffler 14 is attached to the downstream end of the exhaust pipe 11.

[0018] Also, reference numeral 21 denotes an EGR (Exhaust Gas Recirculation) device. This EGR device 21 is equipped with an EGR primary passage 22 and an EGR secondary passage 23. The EGR primary passage 22 connects the exhaust pipe 11 and the air chamber 7a. One end of the EGR secondary passage 23 is connected to the immediate upstream side of the exhaust purification catalyst 12 provided in the exhaust pipe 11. The other end of the EGR secondary passage 23 is connected to the downstream side of the EGR primary passage 22 (the air chamber 7a side).

[0019] The EGR primary passage 22 recirculates a portion of the exhaust gas that has flowed into the exhaust pipe 11 to the air chamber 7a by utilizing a pressure difference. The EGR secondary passage 23 returns a portion of the EGR gas (air) that is recirculated from the EGR primary passage 22 to the air chamber 7a immediately after recovery from a fuel cut to the exhaust pipe 11.

[0020] An EGR primary valve 22a is provided in the EGR primary passage 22 upstream of the portion where the EGR secondary passage 23 is connected. An EGR secondary valve 23a is provided in the EGR secondary passage 23. A check valve 23b is provided in the EGR secondary passage 23 upstream of the EGR secondary valve 23a. The check valve 23b prevents exhaust gas from flowing from the EGR secondary valve 23a toward the EGR primary passage 22.

[0021] Furthermore, an electric pump 23c is interposed in the EGR secondary passage 23 downstream of the EGR secondary valve 23a. The opening degree of each EGR valve 22a, 23a can be freely set by, for example, a stepping motor. The opening degree of each EGR valve 22a, 23a and the ON / OFF of the electric pump 23c are controlled by an engine control unit (E / G_ECU) 31 serving as a control section, which will be described later. The electric pump 23c guides EGR gas downstream of the EGR primary passage 22 to the EGR secondary passage 23 and discharges it directly upstream of the exhaust purification catalyst 12 in the exhaust pipe 11.

[0022] Next, the arrangement of sensors for detecting various parameters required for EGR control will be described. A throttle opening sensor 25 for detecting the throttle opening is connected to the throttle valve 9. An intake pipe pressure sensor 26 for detecting the intake pipe pressure in the air chamber 7a as an absolute pressure is connected to the air chamber 7a.

[0023] Furthermore, an air-fuel ratio sensor 27 is provided upstream of the exhaust purification catalyst 12 installed in the exhaust pipe 11. An oxygen (O2) sensor 28 is provided downstream of the exhaust purification catalyst 12. The air-fuel ratio (A / F) sensor 27 detects the air-fuel ratio (A / F) in the exhaust gas. The oxygen sensor 28 detects the oxygen concentration in the exhaust gas that has passed through the exhaust purification catalyst 12. Although not shown in FIG. 1, other sensors include an accelerator opening sensor 29 that detects the amount of depression of the accelerator pedal operated by the driver, and an engine rotation speed sensor 30 that detects the engine rotation speed.

[0024] The E / G_ECU 31 shown in FIG. 2 is composed of a CPU, RAM, ROM, rewritable non-volatile memory (flash memory or EEPROM), a microcontroller equipped with peripheral devices, etc. The RAM is provided as a work area for the CPU and temporarily stores various data for the CPU. The ROM stores programs and fixed data required for the CPU to execute various processes. The CPU is also called an MPU (microprocessor) or processor. A GPU (graphics processing unit) or a GSP (graph streaming processor) may be used instead of the CPU. Alternatively, a CPU, GPU, and GSP may be selectively combined.

[0025] The above-mentioned sensors 25 to 30 are connected to the input side of the E / G_ECU 31. Furthermore, a throttle actuator 9a and an electric pump 23c are connected to the output side of the E / G_ECU 31. Furthermore, to the output side of the E / G_ECU 31 are connected an EGR primary valve actuator 41 that drives the EGR primary valve 22a, an EGR secondary valve actuator 42 that drives the EGR secondary valve 23a, a fuel injection device 43 that drives the direct injection injector 4 at a predetermined injection timing to inject a predetermined amount of fuel into the cylinder, and an ignition device 44 that drives the ignition plug 5 at a predetermined timing to ignite. In this embodiment, stepping motors are used as the valve actuators 41 and 42.

[0026] The E / G_ECU 31 executes ignition timing control, fuel injection control, EGR control, and fuel cut control during driving. When the EGR control condition is met, the EGR control adjusts the flow rate (volume flow rate) [m 3 / sec]. Then, the E / G_ECU 31 drives the EGR primary valve actuator 41 to control the opening (number of steps) of the EGR primary valve 22a, and supplies the set flow rate of EGR gas to the air chamber 7a. The EGR secondary valve 23a opens when returning from a fuel cut, and is normally kept fully closed.

[0027] Furthermore, fuel cut control temporarily stops fuel injection when a fuel cut condition (such as releasing the accelerator pedal or deceleration due to forced braking) is met. When fuel cut is executed, the E / G_ECU 31 fully closes the EGR primary valve 22a to cut off the supply of EGR gas to the cylinders. As a result, only fresh air (throttle-passed air) that has passed through the throttle valve 9 is supplied to each cylinder.

[0028] Furthermore, the E / G_ECU 31 executes EGR learning / diagnosis to check the state of the EGR device 21 when fuel is cut off while the vehicle is running. When the EGR learning / diagnosis starts, the EGR primary valve 22a, which is in a fully closed state, is first gradually opened to its full open state. During this time, the E / G_ECU 31 reads the intake pipe pressure detected by the intake pipe pressure sensor 26. Then, the E / G_ECU 31 checks whether the EGR primary valve 22a is operating normally from fluctuations in the intake pipe pressure detected by the intake pipe pressure sensor 26 that accompany the opening operation of the EGR primary valve 22a.

[0029] Incidentally, in EGR learning / diagnosis during fuel cut while driving, the EGR primary valve 22a is once fully closed and then fully opened. When the EGR primary valve 22a is opened, EGR gas from the EGR primary passage 22 is also supplied to each cylinder in addition to the air passing through the throttle. Since only air is filled in the cylinder during fuel cut, the EGR gas supplied to the cylinder is also only air. Therefore, the intake air flow rate [m3 / s] is the total air flow rate Qtotal [m 3 / s]. Therefore, the cylinder becomes an excess air state in which the filling efficiency of the air in the cylinder is higher by the EGR flow rate Qegr than the state before the EGR learning / diagnosis started.

[0030] Thereafter, when the E / G_ECU 31 detects recovery from fuel cut, it resumes ignition timing control, fuel injection control, and EGR control. The E / G_ECU 31 determines whether recovery from fuel cut has occurred based on, for example, the accelerator opening θacc detected by the accelerator opening sensor 29. That is, the E / G_ECU 31 determines that recovery from fuel cut has occurred when depression of the accelerator pedal from a released state is detected based on the accelerator opening θacc. Therefore, the E / G_ECU 31 functions as a fuel cut recovery detection unit of the present invention.

[0031] Then, when EGR control is resumed upon recovery from fuel cut, the E / G_ECU 31 opens the EGR primary valve 22a to a predetermined position by driving the EGR primary valve actuator 41. When the EGR primary valve 22a opens, the EGR gas in the EGR primary passage 22 is supplied to each cylinder via the air chamber 7a. Immediately after recovery from fuel cut, the EGR primary passage 22 is filled with fresh air, so the EGR gas supplied to each cylinder is only air.

[0032] The E / G_ECU 31 is equipped with a corrected torque / EGR secondary valve opening calculation unit 31a. This calculation unit 31a calculates a torque correction value and the opening of the EGR secondary valve 23a when fuel cut is resumed during EGR learning / diagnosis or after EGR learning / diagnosis. This reduces a torque step caused by excess air supplied from the EGR primary passage 22 when fuel cut is resumed.

[0033] When the E / G_ECU 31 determines that the engine has resumed fuel cut, the fuel injection control determines the amount of fuel to be injected from the direct injector 4 into each cylinder immediately after the engine resumes fuel cut. The fuel injection amount is determined based on the air pipe pressure detected by the intake pipe pressure sensor 26, the engine speed Neg detected by the engine speed sensor 30, etc. Then, the E / G_ECU 31 transmits a fuel injection amount signal to the fuel injection device 43. In response, the fuel injection device 43 drives the direct injector 4 of each cylinder at a predetermined timing to inject fuel.

[0034] Furthermore, when the ignition timing control is resumed, the E / G_ECU 31 performs ignition timing retard control. In this ignition timing retard control, the E / G_ECU 31 transmits an ignition retard signal to the ignition device 44. In response, the ignition device 44 retards the ignition timing to a predetermined value and outputs an ignition signal at a predetermined ignition timing to the spark plug 5 facing the cylinder to be ignited.

[0035] Furthermore, when executing fuel injection control and ignition timing control at the time of fuel cut recovery, the E / G_ECU 31 uses a corrected torque / EGR secondary valve opening calculation unit 31a to calculate a correction torque for correcting the fuel injection amount and ignition timing at the time of recovery, and the opening of the EGR secondary valve 23a. When the EGR secondary valve 23a opens, part of the EGR gas is released to the exhaust pipe 11 side through the EGR secondary passage 23.

[0036] The E / G_ECU 31 causes the calculation unit 31a to execute the calculation for a preset number of cycles (where 1 cycle = 720 degrees) from the time when it is determined that the engine has returned from fuel cut. The number of cycles until the combustion gas generated by the first explosion after the return from fuel cut (the first combustion in the cylinder after the return from fuel cut) flows into the combustion chamber as EGR gas is known in advance. The opening of the EGR secondary valve 23a and the torque after ignition timing correction are calculated for this number of cycles. Alternatively, the E / G_ECU 31 may monitor the change in the air-fuel ratio detected by the air-fuel ratio sensor 27 after the return from fuel cut, and execute the calculation until the air-fuel ratio changes due to the first explosion.

[0037] 3 shows the functional configuration of the corrected torque / EGR secondary valve opening calculation unit 31a. This calculation unit 31a includes a first table lookup unit Tb1 as a surplus torque setting unit, a second table lookup unit Tb2 as an EGR secondary valve opening setting unit, a map lookup unit Mp1 as a required torque setting unit, a first comparator 51, a first subtractor 52, a first switch 53, a second subtractor 54, and a second switch 55 as comparison units, a first adder 56 as a correction torque setting unit, a second adder 57 and a second comparator 58 as a corrected torque calculation unit, and a third switch 59 as a drive signal output unit.

[0038] The first table search unit Tb1 sets the surplus torque Tegr [N·m]. This surplus torque is calculated based on the volumetric flow rate (air flow rate) Qegr [m 3 / sec], the surplus torque Tegr is set by referring to an excess torque table. This excess torque Tegr is the excess engine torque generated by supplying air to the combustion chamber from the EGR primary passage 22. Therefore, the first table lookup section Tb1 has the function of the surplus torque setting section of the present invention.

[0039] The concept of the surplus torque table is shown in Figure 4. The EGR flow rate Qegr is set based on the opening (number of steps) of the EGR primary valve 22a. The EGR flow rate Qegr and the opening of the EGR primary valve 22a are proportional to each other with a predetermined gradient. Therefore, the EGR flow rate Qegr can be calculated from the opening of the EGR primary passage 22 using a linear equation.

[0040] As shown in Figure 4, the surplus torque Tegr increases as the EGR flow rate Qegr increases. The characteristics of this surplus torque table are determined and set in advance for each vehicle model through experiments or the like.

[0041] The map search unit Mp1 sets the engine torque (required torque) Tdrv [N·m] required by the driver by referring to the required torque map based on the accelerator opening θacc and the engine speed Neg. Fig. 5 shows the concept of the required torque map. As shown in the figure, in a situation where the engine speed Neg is high with a low accelerator opening θacc, the required torque Tdrv is small. On the contrary, in a situation where the engine speed Neg does not increase even when the accelerator opening θacc is depressed, the required torque Tdrv becomes large.

[0042] The first comparator 51 compares the required torque Tdrv and the surplus torque Tegr. When the required torque Tdrv is less than the surplus torque Tegr (Tdrv < Tegr), it outputs "0". Also, when the required torque Tdrv is greater than or equal to the surplus torque Tegr (Tdrv ≧ Tegr), it outputs "1". Tdrv < Tegr indicates that the opening of the accelerator pedal at the time of fuel cut return is in a low to medium opening state. Also, Tdrv ≧ Tegr indicates that the opening of the accelerator pedal at the time of fuel cut return is in a high opening state.

[0043] The first subtracter 52 subtracts the surplus torque Tegr from the required torque Tdrv to calculate the torque difference (Tdrv - Tegr). Then, it outputs the torque difference (Tdrv - Tegr) to the first switch 53. When "1" is input from the first comparator 51 (Tdrv ≧ Tegr), the first switch 53 outputs the torque difference (Tdrv - Tegr) obtained by the first subtracter 52 as the air correction torque Tair [N·m] to the first adder 56. This air correction torque Tair corrects the amount of air passing through the throttle valve 9 (throttle passing air amount).

[0044] Also, when "0" is input to the first switch 53 from the first comparator 51 (Tdrv < Tegr), it outputs "0" to the first adder 56. In this case, even if the driver depresses the accelerator pedal at the time of fuel cut return, the E / G_ECU 31 does not operate to open the throttle valve 9 of the electronic control throttle valve.

[0045] On the other hand, the second subtractor 54 subtracts the surplus torque Tegr from the required torque Tdrv to calculate the torque difference (Tdrv - Tegr). Then, this torque difference (Tdrv - Tegr) is output to the second switch 55. When "0" is input from the first comparator 51 (Tdrv < Tegr), the second switch 55 outputs the torque difference (Tdrv - Tegr) obtained by the second subtractor 54 as the negative ignition correction torque Tsp [N·m] to the first adder 56. Note that a limiter considering the misfire limit is set for this ignition correction torque Tsp.

[0046] On the other hand, when "1" is input from the first comparator 51 (Tdrv ≥ Tegr), the second switch 55 outputs the ignition correction torque Tsp [N·m] as 0 to the first adder 56. Therefore, in this case, torque adjustment by the ignition correction torque is not performed.

[0047] The first adder 56 adds the air correction torque Tair and the ignition correction torque Tsp to calculate the total correction torque Ttot as the correction torque (Ttot ← Tair + Tsp). From the first switch 53, the air correction torque Tair, which is the torque difference (Tdrv - Tegr), is output only when the first comparator 51 outputs "1" (Tdrv ≥ Tegr). On the other hand, from the second switch 55, the negative ignition correction torque Tsp, which is the torque difference (Tdrv - Tegr), is output only when the first comparator 51 outputs "0" (Tdrv < Tegr).

[0048] Therefore, the total correction torque Ttot output from the first adder 56 becomes the value of the air correction torque Tair when the required torque Tdrv is greater than or equal to the surplus torque Tegr (Tdrv ≥ Tegr). Also, this total correction torque Ttot becomes the value of the ignition correction torque Tsp when the required torque Tdrv is less than the surplus torque Tegr (Tdrv < Tegr).

[0049] Therefore, when the required torque Tdrv is greater than or equal to the surplus torque Tegr (Tdrv ≧ Tegr), the opening degree of the throttle valve 9 is corrected (air correction) to mitigate the torque shock during fuel cut return. Also, when the required torque Tdrv is less than the surplus torque Tegr (Tdrv < Tegr), the ignition timing is retarded (ignition correction) by the ignition correction torque Tsp to mitigate the torque shock during fuel cut return.

[0050] The second adder 57 adds the total correction torque Ttot to the required torque Tdrv to calculate the corrected torque Tcor [N·m], and outputs that value.

[0051] The E / G_ECU 31 corrects the intake air amount and ignition timing based on the corrected torque Tcor [N·m] from the second adder 57. Then, the E / G_ECU 31 outputs a throttle opening signal corresponding to the corrected intake air amount to the throttle actuator 9a. At the same time, the E / G_ECU 31 outputs the corrected ignition timing signal to the ignition device 44.

[0052] The throttle actuator 9a opens the throttle valve 9 to a predetermined opening degree according to the drive signal input from the E / G_ECU 31. Also, the ignition device 44 retards the ignition timing of the spark plug 5 of the ignition target cylinder according to the ignition timing signal input from the E / G_ECU 31.

[0053] Also, the second comparator 58 checks whether the total correction torque Ttot is greater than or equal to "0". And when the total correction torque Ttot is on the negative side less than or equal to "0" (Ttot ≦ 0), it outputs "0" to the third switch 59. Also, when the total correction torque Ttot exceeds "0" and is on the positive side (Ttot > 0), the second comparator 58 outputs "1" to the third switch 59. The state of Ttot > 0 means that in the E / G_ECU 31, even if the air amount passing through the throttle valve is set to idle (fully closed) and the ignition timing is retarded to the misfire limit based on the corrected torque Tcor, the actual torque may exceed the required torque Tegr.

[0054] In the second table search section Tb2, the total correction torque Ttot is set as the corrected surplus torque Tegr'. Then, the secondary valve opening is set by referring to the EGR secondary valve opening table based on this corrected surplus torque Tegr'. Figure 6 shows the concept of the EGR secondary valve opening table. This EGR secondary valve opening table calculates the surplus torque in relation to the air flow rate [m 3 / sec], and the valve opening (number of steps) corresponding to this air flow rate is determined in advance for each vehicle model through experiments, etc. As shown in the figure, the opening of the EGR secondary valve 23a (EGR secondary valve opening) Segr increases as the corrected surplus torque Tegr' increases.

[0055] When "0" is input from the second comparator 58, the third switch 59 keeps the EGR secondary valve opening at "0", that is, maintains the closed valve state. When "0" is input from the second comparator 58 and Ttot≦0 is met, the throttle passing air amount corrected based on the corrected torque Tcor and the ignition timing are retarded, so that the actual torque can be made approximately equal to the required torque Tegr.

[0056] Furthermore, when "1" is input from the second comparator 58 (Ttot>0), the third switch 59 reads the EGR secondary valve opening Segr set in the second table search unit Tb2 and outputs a corresponding drive signal to the EGR secondary valve actuator 42. At the same time, the third switch 59 outputs a pump drive signal to the electric pump 23c provided in the EGR secondary passage 23.

[0057] The EGR secondary valve actuator 42 opens the EGR secondary valve 23a to a predetermined position based on a drive signal from the E / G_ECU 31. The EGR secondary valve 23a then opens to an opening corresponding to the air flow rate [m3 / sec] set by converting the corrected surplus torque Tegr'. As a result, the surplus air in the EGR primary passage 22 passes through the EGR secondary passage 23 by the drive of the electric pump 23c and is discharged to the exhaust pipe 11 directly upstream of the exhaust purification catalyst 12.

[0058] This prevents excessive air from being supplied from the EGR primary passage 22 to the air chamber 7a when the fuel cut is resumed after EGR learning / diagnosis was performed during a fuel cut. As a result, the actual torque can be made to be approximately the required torque Tdrv without retarding the ignition timing to the misfire limit. This reduces the torque step caused by the sudden rise in engine torque immediately after the fuel cut is resumed.

[0059] Moreover, the excess air is discharged immediately upstream of the exhaust purification catalyst 12, and this excess air is supplied to the exhaust purification catalyst 12 and the GPF 13. This allows the excess air to be used as an oxidizing agent that promotes the oxidation of CO (carbon monoxide), HC (hydrocarbon), and PM (particulate matter).

[0060] The present invention is not limited to the above-described embodiment. For example, the engine to be used is not limited to a direct injection engine, but may be a port injection engine or a diesel engine. [Explanation of symbols]

[0061] 1...Engine, 2...cylinder head, 2a…intake port, 2b...Exhaust port, 3...piston, 4...Direct injection injector, 5...spark plug, 6...intake manifold, 7...intake pipe, 7a...Air chamber, 8...Air cleaner, 9...Throttle valve, 9a...Throttle actuator, 10...Exhaust manifold, 11...exhaust pipe, 12...Exhaust gas purification catalyst, 14...Muffler, 21...EGR device, 22...EGR primary passage, 22a...EGR primary valve, 23...EGR secondary passage, 23a...EGR secondary valve, 23b...check valve, 23c...electric pump, 25...Throttle opening sensor, 26... Intake pipe pressure sensor, 27...Air-fuel ratio sensor, 28...oxygen sensor, 29...Accelerator opening sensor, 30...Engine speed sensor, 31...Engine control unit, 31a... Corrected torque / EGR secondary valve opening calculation unit, 41...EGR primary valve actuator, 42...EGR secondary valve actuator, 43...Fuel injection device, 44...Ignition device, Mp1...Map search section, Neg...engine RPM, Qegr…EGR flow rate, Segr...EGR secondary valve opening, Tair...air correction torque, Tcor: corrected torque, Tdrv: required torque, Tegr...excess torque, Tegr': corrected surplus torque, Tsp: Ignition correction torque, Ttot: total correction torque, θacc...Accelerator opening

Claims

1. an EGR valve disposed in an EGR passage that bypasses an exhaust passage and an intake passage of an engine provided in the EGR device; a fuel injection device that supplies fuel into the cylinder; an ignition device that ignites a spark plug disposed in the cylinder at a predetermined ignition timing; a fuel cut recovery detection unit that detects recovery from fuel cut; a control unit that forcibly opens and closes the EGR valve during the fuel cut to learn / diagnose the EGR device, and that executes retard control of the ignition timing, control of the amount of air passing through a throttle valve, and control of the opening of the EGR valve when returning from the fuel cut; In an engine control device comprising: the control unit has a calculation unit that calculates torque when the engine returns from the fuel cut during or after learning / diagnosis of the EGR device, The calculation unit a required torque setting unit that sets a required torque, which is an engine torque required by a driver, when the engine is restored from the fuel cut; an excess torque setting unit that sets excess torque during combustion based on an air flow rate passing through the EGR valve when returning from the fuel cut; a comparison unit that compares the required torque set by the required torque setting unit with the surplus torque set by the surplus torque setting unit; a correction torque setting unit that sets a correction torque for retarding the amount of air passing through the throttle valve and the ignition timing based on the comparison result of the comparison unit; An engine control device comprising:

2. When the comparison unit determines that the required torque is greater than the surplus torque, the correction torque setting unit subtracts the surplus torque from the required torque, sets the result as the correction torque, and corrects the amount of air passing through the throttle valve with the correction torque. When the comparison unit determines that the required torque is smaller than the surplus torque, the correction torque setting unit retards the ignition timing with the correction torque.

2. The engine control device according to claim 1.

3. a corrected torque calculation unit that calculates a corrected torque by adding the correction torque set by the correction torque setting unit to the required torque set by the required torque setting unit; and The control unit sets the ignition timing and the opening of the throttle valve when returning from a fuel cut based on the corrected torque calculated by the corrected torque calculation unit.

3. The engine control device according to claim 2.

4. The EGR device further includes an EGR secondary passage, one end of the EGR secondary passage is connected to a portion immediately upstream of an exhaust purification catalyst interposed in the exhaust passage, and the other end is connected to a portion downstream of the EGR secondary passage, an EGR secondary valve is interposed in the EGR secondary passage, The calculation unit an EGR secondary valve opening setting unit that sets an opening of the EGR secondary valve corresponding to the air flow rate set based on the correction torque; a drive signal output unit that outputs a drive signal to open the EGR secondary valve at the opening degree set by the EGR secondary valve opening degree setting unit; 2. The engine control device according to claim 1, further comprising:

5. a pump is provided in the EGR secondary passage to discharge air from the EGR secondary passage to the exhaust passage, The drive signal output unit opens the EGR secondary valve and outputs a pump drive signal to the pump.

5. The engine control device according to claim 4.

Images