JP6528591B2 - Engine control device - Google Patents

Description

  The present invention relates to a control device of an engine provided with an exhaust gas recirculation device.

  An engine mounted on a vehicle or the like is often equipped with an exhaust gas recirculation device. The exhaust gas recirculation device recirculates a part of the exhaust gas exhausted from the combustion chamber of the engine to the atmosphere through the exhaust passage to the intake passage through the exhaust gas recirculation passage connecting the exhaust side and the intake side. The combustion temperature is lowered to suppress the emission of nitrogen oxides (NOx) and the like contained in the exhaust gas.

  Exhaust gas introduced from the exhaust side to the intake side (hereinafter referred to as return gas) is sent to the combustion chamber by opening / closing the valve device provided in the exhaust gas recirculation passage or the intake throttle valve provided in the intake passage. The actual oxygen concentration is feedback-controlled to control the introduction amount of the reflux gas so that the actual oxygen concentration of the intake air of the intake manifold section leads to the target value.

  For example, in Patent Document 1, an oxygen sensor is provided in the intake passage on the downstream side of the joining position of the reflux gas and the intake air, and the intake air introduced into the combustion chamber is derived from the oxygen concentration in the intake air mixed with the reflux gas. The ratio of the reflux gas actually contained (the actual reflux gas rate) is calculated. The engine is controlled such that the actual reflux gas rate matches the target reflux gas rate, and the presence or absence of a device failure is also detected based on the deviation thereof.

Japanese Patent Application Laid-Open No. 5-18324

  As described above, the oxygen concentration of the intake air after the introduction of the reflux gas is directly measured, and it is reflected in the reflux gas control based on the measurement result, and the malfunction of the exhaust gas recirculation device based on the measurement result. It is known to detect.

  However, in an engine provided with a plurality of cylinders, the actual recirculation gas rate is not the same for all the cylinders, and the numerical value often differs for each cylinder. For this reason, in the above-described technology, it is not possible to reflect the actual recirculation gas rate, which differs for each cylinder, in fuel control, combustion control of an engine, and detection control of a defect.

  Therefore, an object of the present invention is to make it possible to more accurately reflect the actual reflux gas rate in the control of the engine.

  In order to solve the above problems, the present invention recirculates a part of the exhaust gas through an intake air passage and an exhaust passage connected to the combustion chambers of a plurality of cylinders, and an exhaust gas recirculation passage connecting the exhaust passage and the intake passage. An exhaust gas recirculation system for introducing into the intake air as gas, an intake manifold provided at the downstream end of the intake passage and in which a connecting flow path leading to the combustion chamber of each cylinder branches, an opening in each connecting flow path A bypass passage having an inlet for taking in the intake air, an outlet opening in the intake passage upstream of the connection passage, and an outlet for delivering the taken-in intake, and an intake provided in the bypass passage It is based on an intake oxygen concentration detection means for detecting an actual oxygen concentration, a target oxygen concentration in the intake passage according to the operating condition and the actual oxygen concentration detected by the intake oxygen concentration detection means. Employing a control apparatus for an engine equipped with an intake combustion control means for controlling the combustion in the introduction and the combustion chamber of the intake into the combustion chamber are.

Here, a configuration may be adopted in which a pump device for delivering a gas from the inlet to the outlet is provided in the bypass passage.

  Further, an intake valve provided in the bypass passage for selecting an intake destination of intake air detected by the intake oxygen concentration detection means from among a plurality of the connection flow paths, and an intake valve for controlling the opening and closing of the intake valve. And an inlet valve control unit.

  Furthermore, the actual oxygen concentration of the intake air taken from a single or a plurality of flow paths selected from the plurality of connection flow paths by opening and closing the intake valve is stored together with the information on the selected connection flow path. A configuration including concentration storage means can be employed.

  It is possible to employ a configuration provided with abnormality determination means that determines the presence or absence of a defect in any part of the exhaust passage or the exhaust gas recirculation passage based on the actual oxygen concentration and the target oxygen concentration.

  The outlet is provided at a position facing the connection passage of the bypass passage or a branch portion to the connection passage, and a plurality of discharge destinations of intake air taken into the bypass passage are provided. It is possible to employ a configuration including a delivery valve for selecting from among the connection flow paths, and delivery valve control means for controlling the opening and closing of the delivery valve.

  When the detected actual oxygen concentration is smaller than the average value of the actual oxygen concentrations of the connection flow paths, the delivery valve sends the taken intake air to the connection flow path where the actual oxygen concentration is higher than the average value. When the detected actual oxygen concentration is higher than the average value of the actual oxygen concentration of each connection channel, the intake air taken in is sent to the connection channel whose actual oxygen concentration is lower than the average value. A controlled configuration can be employed.

  According to the present invention, the connecting flow passage of the intake manifold communicating with each combustion chamber and the intake passage on the upstream side of the connecting flow passage are connected by the bypass passage and detected by the intake oxygen concentration detecting means provided in the bypass passage. Since introduction of intake air into the combustion chamber and control of combustion in the combustion chamber are performed based on the actual oxygen concentration and the target oxygen concentration in the intake passage according to the operating conditions, each combustion chamber of the intake manifold It is possible to measure intake air that is not affected by the cylinder distribution from a plurality of intake ports that are connection flow paths. For this reason, it is possible to more accurately reflect the actual reflux gas rate in the control of the engine.

It is a schematic diagram of the engine which shows one Embodiment of this invention. FIG. 7 is a schematic view of an engine showing another embodiment. It is a graph of the control of the engine of the present invention

  An embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic view of an engine 1 of the present invention.

  The engine 1 of this embodiment is a diesel engine for automobiles. A piston is accommodated in a cylinder of the engine 1, and a combustion chamber 2 is formed by an inner wall surface of the cylinder, an upper surface of the piston, and the like.

  The engine 1 includes an intake passage 4 for feeding intake air into the combustion chamber 2 of each cylinder, an exhaust passage 5 drawn from the combustion chamber 2, a fuel injection device (not shown) for injecting fuel into the combustion chamber 2 and the like. ing.

  In the drawings, members and means directly related to the present invention are mainly shown, and other members and the like are not shown. In addition, the number of cylinders of the engine 1 may be plural, and it may be four cylinders as in this embodiment, or a multi-cylinder engine having two cylinders, three cylinders, or more cylinders than four cylinders. May be

  An intake valve hole, which is an opening to the combustion chamber 2 of the intake passage 4 of each cylinder, is opened and closed by the intake valve. Further, an exhaust valve hole, which is an opening to the combustion chamber 2 of the exhaust passage 5 drawn from the combustion chamber 2, is opened and closed by the exhaust valve.

  In the intake passage 4, a surge tank, an intake cooling device for cooling intake air flowing through the intake passage 4, an intake cooling device, a supercharger, and the intake passage 4 which are upstream from the intake port 4 a which is a connection passage leading to each combustion chamber 2. An intake throttle valve 3 for adjusting the flow passage area, an air cleaner and the like are provided. The intake throttle valve 3 adjusts the introduction amount of air (fresh air) to the intake passage 4 by increasing or decreasing the cross-sectional area of the flow passage of the intake passage 4 by the operation of a butterfly valve type valve body.

  The connection flow passage leading to the combustion chamber 2 is an intake port 4a formed in the intake manifold in the same number as the number of cylinders. Hereinafter, the intake port 4a is referred to as a connection flow path 4a. The intake passage 4 forms one space on the upstream side in the intake manifold, and branches therefrom into the same number of passages as the number of cylinders toward the downstream side to form the connection passage 4a. In this embodiment, four connection flow paths 4a are provided corresponding to the four cylinders.

  The exhaust passage 5 is provided with a turbocharger, an exhaust purification device provided with a catalyst for removing harmful substances in the exhaust, a muffler, and the like from the exhaust port 5a drawn out from the combustion chamber toward the downstream side.

  In addition, the engine 1 is provided with a rotation sensor that detects the number of rotations of the engine by detecting the rotational angular velocity and the rotational angular acceleration of the crankshaft.

  Control means provided in the electronic control unit (Electronic Control Unit) 30 through cables for the intake valve and exhaust valve, the fuel injection device, the intake throttle valve 3, the exhaust gas purification device, and other devices necessary for the operation of the engine Controlled by Further, the electronic control unit 30 acquires necessary information from the engine and sensors provided around the engine. The electronic control unit 30 can obtain various information necessary for control of the engine, such as the number of revolutions of the engine 1 and the engine load, from the information from these sensors.

  Further, the exhaust passage 5 and the intake passage 4 communicate with each other through an exhaust gas recirculation passage 11 which constitutes the exhaust gas recirculation device 10. The exhaust gas recirculation device 10 has a function of recirculating a part of the exhaust gas exhausted from the engine to the intake passage 4 as a reflux gas. In the exhaust gas recirculation device 10 of this embodiment, the exhaust gas recirculation passage 11 is drawn out from the exhaust passage 5 on the upstream side of the turbocharger and is connected to the intake passage 4 on the downstream side of the turbocharger. Although a gas recirculation device is used, as the exhaust gas recirculation device 10, an exhaust gas recirculation passage 11 is drawn from the exhaust passage 5 downstream of the turbocharger and connected to the intake passage 4 upstream of the turbocharger. A low pressure exhaust gas recirculation system may be employed.

  Further, the exhaust gas recirculation device 10 is provided with a reflux gas control valve 12 for adjusting the flow rate of the reflux gas passing through the exhaust gas recirculation passage 11.

  The flow rate adjustment control means 36 included in the electronic control unit 30 controls the operation of the reflux gas adjustment valve 12 and the throttle valve 3. When the reflux gas adjustment valve 12 is closed, the introduction of the reflux gas from the exhaust side to the intake side is stopped. When the reflux gas adjusting valve 12 is opened, the introduction of the reflux gas from the exhaust side to the intake side is started according to the pressure state in the intake passage 4 based on the operation of the throttle valve 3.

  The intake passage 4 includes an inlet 21b opened to each connection flow passage 4a for taking in the intake air, and an outlet 21a opened to the intake passage 4 on the upstream side of the connection flow passage 4a to deliver the intakeed air. A bypass passage 21 is provided.

  As shown in FIG. 1, the end on the inlet 21 b side of the bypass passage 21 is branched into four inflow pipes opened to each connection flow path 4 a, and each tip of the four inflow pipes is a connection flow path It is an inlet 21b facing in 4a.

  Each of the four inflow pipes is provided with intake valves 25a, 25b, 25c, 25d for selecting an intake destination of intake air into the bypass passage 21 from among the plurality of connection channels 4a. . The intake valve control means 32 provided in the electronic control unit 30 controls the opening and closing of the intake valves 25a, 25b, 25c, 25d.

  The end on the outlet 21a side of the bypass passage 21 branches into four outlet pipes that open at the position facing the connection flow path 4a or the branch (inlet) to the connection flow path 4a, The tip of each of the four outlet pipes is an outlet 21a. The intake air sent out from the outlet 21 a flows into the connection channel 4 a facing the outlet 21 a.

  Each of the four outlet pipes is provided with a delivery valve 24a, 24b, 24c, 24d for selecting the delivery destination of the intake air taken into the bypass passage 21 from among the plurality of connection channels 4a. There is. The delivery valve control means 33 provided in the electronic control unit 30 controls the delivery valves 24a, 24b, 24c and 24d.

  Further, the bypass passage 21 is provided with a pump device 22 for delivering gas from the inlet 21 b to the outlet 21 a. The installation of the pump device 22 can be omitted as long as intake of air into the bypass passage 21 is smoothly performed.

  Furthermore, the bypass passage 21 is provided with intake oxygen concentration detection means 23 for detecting the actual oxygen concentration of the intake air taken into the bypass passage 21.

For example, a linear air fuel sensor (Linear Air-Fuel ratio sensor) or the like can be adopted as the intake oxygen concentration detection means 23, and the actual oxygen concentration of intake air can be obtained at a position just before being introduced into the combustion chamber 2. It can be detected. The intake oxygen concentration detection means 23 has a function capable of numerically detecting a continuous change in air-fuel ratio (oxygen concentration) instead of a sensor that detects only lean or rich, such as an O ₂ sensor, for example. Is preferred.

  A concentration detection bypass device 20 is constituted by the bypass passage 21, intake valves 25a, 25b, 25c, 25d, delivery valves 24a, 24b, 24c, 24d, the pump device 22, intake oxygen concentration detection means 23, etc. .

  The electronic control unit 30 introduces the intake air into the combustion chamber 2 or the combustion chamber based on the actual oxygen concentration detected by the intake oxygen concentration detecting means 23 and the target oxygen concentration in the intake passage 4 according to the operation situation. An intake combustion control unit 31 is provided to control the combustion in the unit 2. The intake combustion control means 31 performs various controls necessary for the operation of the engine, such as intake control, fuel control, and combustion control, based on the information of the actual oxygen concentration and the target oxygen concentration.

  In addition, the electronic control unit 30 detects a defect in any part of the exhaust passage 5 or the exhaust gas recirculation passage 10 based on the concentration difference between the actual oxygen concentration and the target oxygen concentration in the intake passage 4 according to the operating conditions. An abnormality determination means 35 for determining the presence or absence is provided.

  Furthermore, the electronic control unit 30 is configured so that the intake valve 25a, 25b, 25c, 25d is opened or closed to select an actual intake air taken from one or more connection channels 4a selected from among the plurality of connection channels 4a. A concentration storage means 34 is provided for storing the oxygen concentration together with the information of the selected connection channel 4a. The concentration storage means 34 stores the intake amount in intake air introduced into the combustion chamber 2 of each cylinder, the introduction amount of return gas, the actual return gas rate, etc. together with the number of the cylinder. The information to be stored may be information on one selected cylinder or information on a plurality of cylinders selected simultaneously.

  Hereinafter, the control method of the engine and the flow thereof will be described based on the graph of FIG.

  First, it is assumed that the exhaust gas recirculation device 10 performs close loop control (feedback control). The feedback control reflects the signal of the output to the input to the next input, and while controlling the input and output repeatedly, controls the output to be an appropriate target value or reference value. Here, the opening degree of the reflux gas control valve 12 and the intake throttle valve 3 is feedback controlled so that the actual oxygen concentration of the intake air becomes a target value.

  The exhaust gas recirculation device 10 starts the introduction of the reflux gas from the exhaust side to the intake side. Information on the actual oxygen concentration of the intake air introduced into the combustion chamber 2 is acquired from the intake oxygen concentration detection means 23. Acquisition of this information is performed for each cylinder for each cylinder, and the information of each cylinder is stored.

  Here, assuming that the actual oxygen concentration measured is X, the amount of reflux gas is [(0.2−X) ÷ X] times the amount of intake air from the outside air, and the actual reflux gas ratio is [(1-5 X) ) X 100]%. 0.2 is the content ratio of oxygen in the air when the air is 1.0.

  Then, it is determined whether the absolute value of the concentration difference of the target oxygen concentration of the intake air in the intake passage 4 according to the operating condition with respect to the actual oxygen concentration of the intake detected by the intake oxygen concentration detection means 23 is larger than a predetermined value. Be done. This determination is performed by the intake combustion control means 31, and the intake combustion control means 31 performs control according to the determination result.

  For example, in the cylinder of code # 1 shown in FIG. 3, the actual oxygen concentration and the target oxygen concentration substantially match, and the intake air has the correct actual reflux gas rate.

  In the cylinders denoted by # 2, # 3, and # 4 shown in FIG. 3, the actual oxygen concentration and the target oxygen concentration do not match, respectively.

  Here, it is assumed that the absolute value of the density difference is larger than a predetermined value determined in advance. In this case, the abnormality determining means 35, for example, can not close the reflux gas control valve 12 when the actual oxygen concentration is extremely lower than the target oxygen concentration although the reflux gas is not introduced. It is determined that there is an abnormal condition. Conversely, for example, if the actual oxygen concentration is extremely higher than the target oxygen concentration despite the introduction of the reflux gas, the passage by the deposit in any part of the exhaust passage 5 or the exhaust reflux passage 11 It is determined that there is an abnormal condition in which there is a blockage of When it is determined that an abnormal state is present, the driver is prompted by a warning or the like to immediately shift to an operation mode in which the reflux gas is not introduced.

  Further, it is assumed that the absolute value of the density difference is equal to or less than a predetermined value. If the concentration difference between the actual oxygen concentration and the target oxygen concentration is equal to or less than a predetermined value, for example, in the cylinder of code # 2, the actual oxygen concentration is higher than the target oxygen concentration. Advanced angle control is performed. On the other hand, since the actual oxygen concentration is lower than the target oxygen concentration in the cylinders # 3 and # 4, the fuel injection retardation control is performed to correct the actual oxygen concentration. This makes it possible to control the engine that reflects the deviation of the cylinder distribution of the reflux gas. Such control of the advance angle and the retardation angle is effective mainly in the middle and high load region, and may not be performed in the low load region such as idle time.

  Further, the intake combustion control means 31 controls the delivery valves 24a, 24b, 24c, 24d, and selects the connection flow path 4a of the delivery destination of the intake taken in the bypass passage 21 to detect the actual oxygen concentration. Take control.

  For example, when the actual oxygen concentration detected from the intake air of the connection flow passage 4a of one cylinder is smaller than the average value of the actual oxygen concentrations of all the connection flow passages 4a, the actual oxygen concentration averages the intake air taken in The delivery valves 24a, 24b, 24c and 24d are controlled so as to feed the connection flow passage 4a of the cylinder higher than the value. Such delivery control may be selected only when the difference between the actual oxygen concentration of the selected cylinder and the average value of all the cylinders is equal to or greater than a predetermined threshold value. Further, as the delivery destination, it is possible to select the connection flow path 4a of the cylinder having the highest actual oxygen concentration or the connection flow path 4a of a plurality of cylinders selected in the order of the high actual oxygen concentration.

  Also, for example, when the actual oxygen concentration detected from the intake air of the connection flow passage 4a of one cylinder is larger than the average value of the actual oxygen concentrations of all the connection flow passages 4a, the intake air taken in is the actual oxygen concentration The delivery valves 24a, 24b, 24c and 24d are controlled so as to deliver them to the connection flow passage 4a of the cylinder whose value is lower than the average value. Such delivery control may be selected only when the difference between the actual oxygen concentration of the selected cylinder and the average value of all the cylinders is equal to or greater than a predetermined threshold value. Further, as the delivery destination, it is possible to select the connection flow path 4a of the cylinder having the lowest actual oxygen concentration or the connection flow path 4a of a plurality of cylinders selected in the order of the lowest actual oxygen concentration.

  In the above control, a predetermined value used when evaluating the concentration difference between the actual oxygen concentration of the intake air detected by the intake oxygen concentration detection means 23 and the target oxygen concentration of the intake air in the intake passage 4 according to the operating condition. Alternatively, with regard to the threshold used in the selection control of the intake destination of the intake, the setting of the predetermined value and the threshold is determined using a map or the like based on two factors of the engine speed and the engine load, for example. be able to. The predetermined value tends to increase as the engine speed increases, and tends to increase as the engine load increases. The same applies to the threshold.

  Further, with regard to the target oxygen concentration of the intake air in the intake passage 4 according to the operating situation, the setting of the target oxygen concentration is determined using a map or the like based on two factors, for example, the engine speed and the engine load. can do. The target oxygen concentration tends to increase as the engine speed increases, and tends to increase as the engine load increases.

  In the above embodiment, the outlet 21a of the bypass passage 21 is made to face each of the connection channels 4a corresponding to a plurality of cylinders. For example, as shown in FIG. The single outlet 21 a may be configured to face the uppermost stream of the intake manifold or the uppermost stream of the surge tank. As a result, the intake air in the bypass passage 21 is likely to be evenly distributed to the respective cylinders.

  Furthermore, in particular, when it is not necessary to select the delivery destination of the intake, the installation of the delivery valves 24a, 24b, 24c, 24d can be omitted. In addition, when it is not necessary to select the intake destination of the intake air taken into the bypass passage 21, the installation of the intake valves 25a, 25b, 25c, 25d can be omitted. In this configuration, since intake to all cylinders is simultaneously targeted for actual oxygen concentration detection, measurement of intake that is not affected by cylinder distribution is possible. For this reason, it is possible to more accurately reflect the actual reflux gas rate in the control of the engine.

  In the above embodiment, the configuration of the present invention has been described taking a diesel engine for a car as an example, but the present invention can be applied to a gasoline engine for a car and various other engines.

1 engine 2 combustion chamber 3 intake throttle valve 4 intake passage 4a intake port (connection flow passage)
5 exhaust passage 5a exhaust port 10 exhaust gas recirculation device 11 exhaust gas recirculation passage 12 recirculation gas control valve 20 concentration detection bypass device 21 bypass passage 22 pump device 23 intake oxygen concentration detection means 30 electronic control unit (Electronic Control Unit)
31: Intake combustion control means 32: Intake valve control means 33: Delivery valve control means 34: Concentration storage means 35: Abnormality determination means 36: Flow rate adjustment control means

Claims (7)

An intake passage and an exhaust passage connected to the combustion chambers of the plurality of cylinders;
An exhaust gas recirculation device for introducing a part of the exhaust gas into the intake air as a reflux gas through an exhaust gas recirculation passage connecting the exhaust passage and the intake passage;
An intake manifold which is provided at the downstream end of the intake passage and in which connection flow paths respectively communicating with the combustion chambers of the respective cylinders are branched;
A bypass passage having an inlet for opening intake air and an outlet for opening intake air upstream of the connection passage and delivering the taken-in intake;
Intake oxygen concentration detection means provided in the bypass passage for detecting the actual oxygen concentration of intake air taken in;
The intake that controls the introduction of intake air into the combustion chamber and the combustion in the combustion chamber based on the actual oxygen concentration detected by the intake oxygen concentration detection means and the target oxygen concentration in the intake passage according to the operating condition Combustion control means,
A control device of an engine comprising: The control device for an engine according to claim 1, further comprising: a pump device for delivering gas from the inlet to the outlet in the bypass passage. An intake valve provided in the bypass passage to select an intake destination of intake air detected by the intake oxygen concentration detection means from among a plurality of the connection channels;
Intake valve control means for controlling the opening and closing of the intake valve;
The control device of the engine according to claim 1 or 2 comprising Concentration storage that stores the actual oxygen concentration of intake air taken from a single or a plurality of flow paths selected from the plurality of connection flow paths by opening and closing the intake valve together with the information of the selected connection flow path The control device of an engine according to claim 3, comprising: The abnormality determination means according to any one of claims 1 to 4, further comprising abnormality determination means for determining the presence or absence of a defect in any part of the exhaust passage or the exhaust gas recirculation passage based on the actual oxygen concentration and the target oxygen concentration. Engine control device. The outlet is provided at a position facing the connection flow path of the bypass passage or a branch to the connection flow path.
A delivery valve for selecting a delivery destination of the intake air taken into the bypass passage from among the plurality of connection channels;
Delivery valve control means for controlling the opening and closing of the delivery valve;
The engine control device according to any one of claims 1 to 5, comprising: When the detected actual oxygen concentration is smaller than the average value of the actual oxygen concentrations of the connection flow paths, the delivery valve sends the taken intake air to the connection flow path where the actual oxygen concentration is higher than the average value. When the detected actual oxygen concentration is higher than the average value of the actual oxygen concentration of each connection channel, the intake air taken in is sent to the connection channel whose actual oxygen concentration is lower than the average value. The engine control device according to claim 6, which is controlled.

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