JP2013083208A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a reference value with excellent accuracy by a simple constitution of an air-fuel ratio sensor provided on an engine.SOLUTION: An engine control device includes an engine 1 having a motor capable of imparting the driving force for mechanically driving the engine at least without combustion, and air-fuel ratio sensors 25, 26, 27 arranged on an intake/exhaust system of the engine 1. The engine control device further includes a motor control means 35c for controlling a motor 34 for the electric power assist of the engine 1, and a correction control means 35d which allows the motor control means 35c to operate the motor 34 when the engine 1 is stopped, and stops the motor 34 after the elapse of the predetermined time to perform the correction of the reference values of the air-fuel ratio sensors 25, 26, 27.

Description

  The present invention relates to an engine control device that performs reference value correction of an air-fuel ratio sensor provided in an engine equipped with an electric assist system.

  Generally, an engine performs fuel injection control, exhaust purification control, and the like by using an oxygen concentration detected by an oxygen sensor provided in an intake passage and an exhaust passage and an air-fuel ratio detected by an air-fuel ratio sensor. Some engines are provided with an exhaust gas recirculation passage (EGR passage) that guides the exhaust gas to the intake passage again. The exhaust gas is circulated through the EGR passage to control the exhaust gas temperature and to be discharged. Control is performed to reduce the amount of NOx.

  The amount of exhaust gas (EGR gas) flowing through the EGR passage is controlled by the opening degree of a control valve provided in the EGR passage. The opening degree of the control valve is controlled using the output value of an oxygen sensor or an air-fuel ratio sensor provided downstream of the inlet of the EGR gas to the intake passage (that is, the connection portion between the EGR passage and the intake passage). Is done. For example, the combustion state in the cylinder is estimated based on the oxygen concentration of intake air (a mixture of fresh air and exhaust gas) detected by an oxygen sensor and the air-fuel ratio of intake air detected by an air-fuel ratio sensor. The opening degree of the control valve is controlled so that the estimated combustion state becomes an appropriate combustion state required at that time, and the EGR gas amount is adjusted to increase or decrease.

  The exhaust passage of the engine is provided with an exhaust purification device equipped with a catalyst for purifying nitrogen oxides in the exhaust and a filter for collecting particulate matter contained in the exhaust. Yes, the exhaust purification device purifies the exhaust of the engine and exhausts it into the atmosphere. For various controls (for example, NOx purge control, S purge control, etc.) performed in this exhaust purification device, output values of an oxygen sensor and an air-fuel ratio sensor disposed upstream of the exhaust purification device are used. Further, the combustion state in the cylinder may be estimated from the output value of the oxygen sensor or air-fuel ratio sensor disposed in the exhaust passage.

  These oxygen sensors and air-fuel ratio sensors may have errors in their sensor values due to changes over time, and may not be able to output accurate sensor values for oxygen concentrations and air-fuel ratios. Therefore, it is necessary to periodically correct in order to eliminate this sensor value error. This correction corrects a deviation from a reference value of a sensor value to be detected in an outside air environment that does not include exhaust gas (hereinafter referred to as a reference value correction). It corresponds to what is called. By regularly performing the reference value correction, the measurement accuracy of the sensor can be kept high.

  For example, Patent Document 1 describes a technique relating to output correction of an oxygen sensor disposed downstream of a recirculation gas inlet of an intake pipe of an engine. In this technique, first, in order to obtain a state suitable for performing the correction calculation, the oxygen concentration in the intake pipe is set to a known value (oxygen concentration in the atmosphere≈21%) by closing the fuel cut or the EGR valve. . Then, the rate of change in pressure is calculated using the output value of the pressure sensor provided in the intake pipe, and the output of the oxygen sensor is corrected based on this rate of change in pressure. Thus, correction can be made in consideration of the pressure dependency of the oxygen sensor, and it is said that an accurate oxygen concentration can always be detected.

JP-A-10-176777

  The technique of the above-mentioned patent document 1 considers the pressure dependency of the oxygen sensor in the output correction (reference value correction) of the oxygen sensor, but the air-fuel ratio sensor is similarly affected by the surrounding pressure ( That is, the output depends on the pressure of the gas to be detected), and an error occurs in the output value due to the pressure. For this reason, it is required to consider the influence of pressure even when correcting the reference value of the air-fuel ratio sensor.

  However, in the technique of the above-mentioned Patent Document 1, a coefficient called a rate of change in pressure is calculated, and a value (sensor specific value) determined by the thickness of the diffusion-controlling layer of the oxygen sensor, the diameter of the pores, etc. in the operating state at that time Since the correction is performed while updating the value so as to be a value unique to the oxygen sensor, the calculation is complicated. Further, since the accuracy of correction of the oxygen sensor depends on the calculation accuracy of the coefficient of change rate against pressure, that is, the detection accuracy of the pressure sensor, it is difficult to improve the correction accuracy.

The present invention has been devised in view of such problems, and it is an object of the present invention to provide an engine control device capable of accurately correcting a reference value of an air-fuel ratio sensor provided in an engine with a simple configuration. Objective.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

(1) An engine control device disclosed herein is disposed in an engine having an electric motor capable of providing a driving force for mechanically driving the engine at least without combustion, and an intake / exhaust system of the engine. An engine control device comprising an air-fuel ratio sensor, wherein the motor control means for controlling the motor, and the motor control means is operated when the engine is stopped, and the motor is stopped after a predetermined time has elapsed. And a correction control means for correcting the reference value of the air-fuel ratio sensor.
In other words, the correction control means determines whether or not the engine is stopped, and if it is determined that the engine is stopped, air (intake or exhaust) in the passage of the engine is supplied to the motor control means. It is characterized in that the reference value correction of the air-fuel ratio sensor is performed after sweeping out (after scavenging the passage).

(2) It is preferable that the air-fuel ratio sensor is an exhaust system air-fuel ratio sensor disposed in an exhaust passage of the engine.
(3) An exhaust system pressure sensor for detecting the pressure in the exhaust passage is provided, and the correction control means detects that the exhaust system is empty if the pressure in the exhaust passage detected by the exhaust system pressure sensor is equal to the atmospheric pressure. It is preferable to perform reference value correction of the fuel ratio sensor.

(4) A recirculation passage for exhaust gas recirculation that communicates the exhaust passage and the intake passage of the engine, and a recirculation gas control means that controls the amount of recirculation gas that flows through the recirculation passage. An intake air / fuel ratio sensor disposed in the intake passage downstream of a connection portion between the intake passage and the return passage, and the return gas when the correction control means determines that the engine is stopped It is preferable to reduce the amount of the reflux gas in the control means.
(5) An intake system pressure sensor for detecting the pressure of the intake passage is provided, and the correction control means is configured to detect the intake system empty if the pressure of the intake passage detected by the intake system pressure sensor is equal to the atmospheric pressure. It is preferable to perform reference value correction of the fuel ratio sensor.

(6) It is preferable that the correction control unit performs the reference value correction if the distance traveled after the previous reference value correction of the air-fuel ratio sensor is equal to or greater than a predetermined distance set in advance.
(7) It is preferable that the electric motor is a driving electric motor used as a driving source of the vehicle, and the vehicle is a hybrid vehicle capable of traveling using at least one of the engine and the electric motor as a driving source.

  According to the engine control apparatus of the present invention, the exhaust gas existing in the intake / exhaust system of the engine can be scavenged by operating the electric motor for a predetermined time when the engine is stopped. Can be in an equivalent state. Further, since the engine is stopped, the pressure of the intake and exhaust system of the engine can be made equal to the atmospheric pressure. Since the reference value correction of the air-fuel ratio sensor is performed in this state, the reference value correction can be performed accurately with a simple configuration.

It is a block diagram which illustrates the control apparatus of the engine which concerns on one Embodiment. It is a lineblock diagram of vehicles provided with a control device of an engine concerning one embodiment. It is a graph which shows the relationship of the sensor output with respect to an actual air fuel ratio. It is a flowchart which shows the control content when implementing the reference value correction | amendment of the air fuel ratio sensor by the engine control apparatus which concerns on one Embodiment.

Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.
[1. Device configuration]
The control device of this embodiment is applied to a diesel engine (engine) having a system (electric assist system) capable of applying a driving force for mechanically driving the engine from the outside. Here, the electric motor that applies electric assist to the engine by applying a driving force is an electric motor for driving used as a driving source of the vehicle. That is, the vehicle is a hybrid vehicle that can travel using at least one of the engine and the electric motor as a drive source.

First, the configuration of the hybrid vehicle will be described with reference to FIG. As shown in FIG. 2, a vehicle (hybrid vehicle) 40 includes a rotary shaft 34 a of a motor generator (hereinafter referred to as “motor”) 34 connected to an output shaft (rotary shaft) 1 a of an engine 1 via a clutch 43. This is configured as a parallel hybrid vehicle in which an input shaft 45a of a transmission (T / M) 45 is directly connected to a rotating shaft 34a of 34. The output shaft 45b of the transmission 45 is connected to the left and right drive wheels 47 via a propeller shaft 46, a differential (not shown) and a drive shaft.
Therefore, when the clutch 43 is connected, both the output shaft 1a of the engine 1 and the rotating shaft 34a of the electric motor 34 are mechanically connected to the drive wheels 47, and when the clutch 43 is disconnected, the electric motor 34 rotates. Only the shaft 34 a is mechanically connected to the drive wheel 47.

  The electric motor 34 operates as an electric motor (motor) when the DC power stored in the battery 42 is converted into AC power by the inverter 48 and supplied, and the driving force is converted to an appropriate speed by the transmission 45. It is transmitted to the drive wheel 47 later. Further, when the vehicle is decelerated, the electric motor 34 operates as a generator, and kinetic energy generated by the rotation of the drive wheels 47 is transmitted to the electric motor 34 through the transmission 45 and converted into alternating current power, thereby generating a regenerative braking force. . Then, the AC power is converted into DC power by the inverter 48, and then charged to the battery 42. The kinetic energy generated by the rotation of the drive wheels 47 is recovered as electric energy.

  When the clutch 43 is connected, the driving force of the engine 1 is transmitted to the transmission 45 via the rotating shaft 34a of the electric motor 34, and after being shifted to an appropriate speed, transmitted to the driving wheels 47, To drive. That is, when the driving force of the engine 1 is transmitted to the driving wheel 47 when the electric motor 34 is operating as a motor, the driving force of the engine 1 and the driving force of the electric motor 34 are transmitted to the driving wheel 47, respectively. The vehicle 40 is driven.

  On the other hand, when the amount of electric power stored in the battery 42 (that is, the charging rate of the battery 42) decreases and the battery 42 needs to be charged, the clutch 43 is connected and the electric motor 34 is driven by a part of the driving force of the engine 1. Is driven. At this time, the electric motor 34 operates as a generator. Thus, power generation is performed, and the generated AC power is converted into DC power by the inverter 48 and then charged to the battery 42. That is, when the electric motor 34 is operated as a generator, only the driving force of the engine 1 (only the remaining portion of the driving force of the engine 1) is transmitted to the drive wheels 47 to drive the vehicle 40.

  In addition, a power connection / disconnection mechanism for interrupting transmission of driving force transmitted from the engine 1 and the motor 34 side is provided inside the transmission 45. For example, when the shift speed (shift range) is neutral (N range), the driving force is not transmitted to the drive wheels. When the clutch 43 is connected in this state, the driving force is exchanged between the engine 1 and the electric motor 34, and the traveling state of the vehicle 40 is not affected. That is, the electric motor 34 can function not only as a drive source of the vehicle 40 but also as a starter (starter motor) of the engine 1.

  The vehicle 40 is provided with an electronic control unit (hereinafter referred to as ECU) that controls these devices. That is, the vehicle 40 includes an engine ECU 35 that controls the engine 1, an inverter ECU 49 that controls the inverter 48, a battery 42 management and a drive source switching, and a vehicle ECU 41 that performs integrated control of the vehicle 40 through the engine ECU 35 and the inverter ECU 49. Provided. The engine ECU 35, the inverter ECU 49, and the vehicle ECU 41 are computers each composed of a memory (ROM, RAM), a CPU, and the like. In addition, about each function of vehicle ECU41 and inverter ECU49, since a well-known technique is applicable, it abbreviate | omits for details.

  Next, each structure of the engine 1 and engine ECU35 is demonstrated using FIG. FIG. 1 shows one of a plurality of cylinders 2 provided in the engine 1, but the other cylinders 2 have the same configuration. A piston 3 that reciprocates vertically is provided in the cylinder 2 of the engine 1. The piston 3 is connected to the crankshaft via a connecting rod. The piston 3 is formed with a cavity 3a serving as a combustion chamber on the top surface.

  An injector 4 for fuel injection is provided on the cylinder head above the cylinder 2. The injector 4 has a tip projecting from the in-cylinder space of the cylinder 2 and directly injects fuel into the cylinder 2. The injection direction of the fuel injected from the injector 4 is set to a direction toward the cavity 3 a of the piston 3. A fuel pipe is connected to the base end of the injector 4, and pressurized fuel is supplied to the injector 4 from the fuel pipe.

  The cylinder head is provided with an intake port 5 and an exhaust port 6 communicating with the in-cylinder space of the cylinder 2, and an intake valve 7 and an exhaust valve 8 for opening and closing each of these ports 5 and 6 are provided. An intake manifold (hereinafter referred to as intake manifold) 9 is provided on the upstream side of the intake port 5. The intake manifold 9 is provided with a surge tank 10 for temporarily storing air flowing to the intake port 5 side. The intake manifold 9 on the downstream side of the surge tank 10 is formed to branch toward the plurality of cylinders 2, and the surge tank 10 is located at the branch point. The surge tank 10 functions to mitigate intake pulsation and intake interference generated in each cylinder 2.

  A throttle body (not shown) is connected to the upstream end of the intake manifold 9, and an electronically controlled throttle valve 11 is built inside the throttle body, and the amount of air flowing to the intake manifold 9 side opens the throttle valve 11. It is adjusted according to the degree (throttle opening). This throttle opening is electronically controlled by an engine ECU 35 described later. An intake passage 12 is connected further upstream of the throttle body. An air filter 13 is interposed at the most upstream side of the intake passage 12, and fresh air filtered by the air filter 13 is introduced into the intake passage 12.

  On the other hand, an exhaust manifold (hereinafter referred to as an exhaust manifold) 15, an exhaust passage 16, and an exhaust purification device 17 are provided downstream of the exhaust port 6 in the exhaust flow. The exhaust manifold 15 is formed so as to merge from the plurality of cylinders 2 and is connected to the exhaust passage 16 on the downstream side thereof. Further, the exhaust purification device 17 interposed in the exhaust passage 16 includes a catalyst 17a and a filter 17b. The catalyst 17a has a function of purifying hydrocarbon (HC) components, carbon monoxide (CO), nitrogen oxides (NOx) and the like contained in the exhaust, and is, for example, an oxidation catalyst or a three-way catalyst.

  The filter 17b is a porous filter (for example, a ceramic filter) that collects particulate matter (Particulate Matter, hereinafter abbreviated as PM) contained in the exhaust gas. In addition, PM is a particulate material in which fuel, lubricant components, sulfur compounds, and the like that remain unburned around carbon black smoke (soot) are attached. In the filter 17b, after the collected PM is continuously oxidized, regeneration control is performed in which the engine ECU 35 forcibly burns the PM to regenerate the filter 17b.

  The intake / exhaust system of the engine 1 is provided with a turbocharger (supercharger) 18 that supercharges intake air into the cylinder 2 using exhaust pressure. The turbocharger 18 is a supercharger interposed between both the intake passage 12 and the exhaust passage 16. The turbocharger 18 rotates the turbine with the exhaust pressure in the exhaust passage 16 and uses the rotational force to drive the compressor, thereby compressing the intake air on the intake passage 12 side and supercharging the engine 1. . An intercooler 14 is provided downstream of the compressor in the intake passage 12 in the intake air flow to cool the compressed air.

  The engine 1 according to the present embodiment is provided with two recirculation passages (also referred to as exhaust recirculation passages and EGR passages) that recirculate exhaust gas flowing through the exhaust passage 16 to the intake passage 12. A first recirculation passage (hereinafter referred to as a first recirculation passage) 19 includes an exhaust passage 16 downstream of the exhaust purification device 17 and an intake passage 12 upstream of the compressor of the turbocharger 18 (here, the air filter 13). A so-called low pressure EGR (Exhaust Gas Recirculation) passage.

  A connection portion between the first recirculation passage 19 and the intake passage 12 incorporates a first control valve (reflux gas control means) 20, and the amount of recirculation gas flowing through the first recirculation passage 19 (that is, led to the intake passage 12). The amount of exhausted gas) is adjusted according to the opening of the first control valve 20. The recirculation gas amount increases as the opening degree of the first control valve 20 increases, and becomes zero when the opening degree is zero (valve closing). The opening degree of the first control valve 20 is controlled by an open / close control unit 35 b provided in the engine ECU 35.

  A second recirculation passage (hereinafter referred to as a second recirculation passage) 22 communicates the exhaust passage 16 upstream of the turbine of the turbocharger 18 and the intake passage 12 downstream of the compressor, thereby providing a so-called high pressure EGR passage. Configure. A second control valve (reflux gas control means) 23 is built in the connecting portion between the second reflux passage 22 and the intake passage 12, and the amount of the reflux gas flowing through the second reflux passage 22 is reduced. Adjusted according to the degree. The amount of recirculation gas from the second recirculation passage 22 increases as the opening degree of the second control valve 23 increases, and becomes zero when the opening degree is zero (valve closing). The opening degree of the second control valve 23 is also controlled by an opening / closing control unit 35b provided in the engine ECU 35.

  Therefore, the intake port 5 of the engine 1 is introduced with intake air (air mixture) in which fresh air and exhaust gas (reflux gas) flowing from the first recirculation passage 19 and the second recirculation passage 22 are mixed. Thus, by mixing the recirculation gas into the intake air, excessive exhaust temperature rise and NOx emission are suppressed. The first reflux passage 19 and the second reflux passage 22 are provided with reflux gas coolers 21 and 24 for cooling the reflux gas, respectively.

  The intake passage 12 is provided with two intake system air-fuel ratio sensors for detecting the air-fuel ratio of the intake air. The first air-fuel ratio sensor 25 is downstream of a compressor provided downstream of a connection portion (portion in which the first control valve 20 is built) between the intake passage 12 and the first recirculation passage 19, and It is disposed upstream of the connection portion between the intake passage 12 and the second return passage 22. The second air-fuel ratio sensor 26 is disposed on the downstream side of the connection portion (portion in which the second control valve 23 is built) between the intake passage 12 and the second recirculation passage 22.

  The first air-fuel ratio sensor 25 and the second air-fuel ratio sensor 26 (hereinafter simply referred to as the intake air-fuel ratio sensors 25 and 26 unless otherwise distinguished) detect the oxygen concentration of the intake air flowing through the intake passage 12. This is a so-called linear air-fuel ratio sensor that outputs a sensor value substantially proportional to the oxygen concentration. The intake system air-fuel ratio sensors 25 and 26 have a characteristic that, as the air-fuel ratio (oxygen concentration) increases, for example, as shown by a solid line in FIG. An output signal corresponding to the oxygen concentration detected by the intake system air-fuel ratio sensors 25 and 26 is transmitted to the engine ECU 35. In addition, an intake system pressure sensor 28 that detects intake pressure (intake pressure) is disposed in the intake passage 12 between the second control valve 23 and the throttle valve 11.

  An air-fuel ratio sensor (hereinafter referred to as an exhaust system air-fuel ratio sensor) 27 for detecting the air-fuel ratio of the exhaust is disposed in the exhaust passage 16. Here, the exhaust system air-fuel ratio sensor 27 is arranged on the upstream side of the catalyst 17a of the exhaust purification device 17 and in a casing that houses the catalyst 17a and the filter 17b. The exhaust system air-fuel ratio sensor 27 is a so-called linear air-fuel ratio sensor that detects the oxygen concentration of the exhaust gas flowing through the exhaust passage 16 and outputs a sensor value that is substantially proportional to the oxygen concentration. It has the same characteristics as the sensors 25 and 26.

  Further, in the exhaust passage 16, an exhaust system pressure sensor 29 for detecting the exhaust pressure (exhaust pressure) is disposed on the upstream side of the catalyst 17a of the exhaust purification device 17 and in a casing that houses the catalyst 17a and the filter 17b. Established. Further, a pressure sensor (atmospheric pressure sensor) 30 for detecting atmospheric pressure is provided at an arbitrary position of the vehicle, and the atmospheric pressure sensor 30 detects the pressure (atmospheric pressure) where the vehicle is traveling. .

  The crankshaft is provided with a crank angle sensor 31 that detects its rotation angle. The amount of change in the rotation angle per unit time is proportional to the actual rotation speed of the engine 1. Therefore, it can be said that the crank angle sensor 31 has a function of detecting the actual rotational speed of the engine 1. Information on the actual rotational speed detected (or calculated) here is transmitted to the engine ECU 35. The engine ECU 35 may calculate the actual rotational speed based on the rotation angle detected by the crank angle sensor 31. Hereinafter, the actual rotational speed of the engine 1 is simply referred to as engine rotational speed.

  The engine ECU 35 provided in the vehicle is configured as, for example, an LSI device or an embedded electronic device in which a microprocessor, a ROM, a RAM, and the like are integrated, and the vehicle ECU 41 and the above-described vehicle are connected via a communication line of an in-vehicle network provided in the vehicle. The first control valve 20, the second control valve 23, and various sensors are connected.

  The engine ECU 35 is an electronic control unit that controls a wide range of systems such as an ignition system, a fuel system, and an intake / exhaust system related to the engine 1. Specific control objects of the engine ECU 35 include the amount of fuel injected from the injector 4 during normal operation or idling, the injection timing, the opening degrees of the first control valve 20 and the second control valve 23 that control the amount of recirculated gas, The opening degree of the throttle valve 11, the regeneration control of the filter 17b, etc. are mentioned. In the present embodiment, correction of the reference value of the oxygen concentration of the intake air / fuel ratio sensors 25 and 26 disposed in the intake passage 12 and the exhaust air / fuel ratio sensor 27 disposed in the exhaust passage 16 will be described in detail.

  The reference value correction is equivalent to, for example, a balance that weighs and is adjusted so that the balance indicates zero, which is the reference value, with nothing on it (generally called zero point correction). If the measuring device itself can be adjusted, it means adjusting the device itself. Also, if the device itself cannot be adjusted, the indication value (that is, deviation from the reference value, error) when it should be zero, which is originally the reference value, is stored. This means that the corrected value for subtracting the indicated value is the original value. The reference value correction here means the latter.

  That is, since the intake air / fuel ratio sensors 25 and 26 disposed in the intake passage 12 and the exhaust air / fuel ratio sensor 27 itself disposed in the exhaust passage 16 cannot be adjusted, the intake passage 12 and the exhaust passage 16 are connected to the atmosphere. The sensor values (output signals corresponding to the oxygen concentration; for example, voltage signals, current signals, etc.) detected by the intake system air-fuel ratio sensors 25 and 26 and the exhaust system air-fuel ratio sensor 27 when the state is made equivalent to the state are the atmospheric conditions. Compare with (oxygen concentration ≈ 21%). At this time, if there is a deviation (error) from the atmospheric oxygen concentration (reference value), the error is stored. From the next time onward, the actual oxygen in the intake passage 12 and the exhaust passage 16 is obtained by adding or subtracting this error from the sensor values detected by the intake system air-fuel ratio sensors 25 and 26 and the exhaust system air-fuel ratio sensor 27. It is determined that the output signal corresponds to the density. Such correction calculation is referred to as reference value correction of the oxygen concentration of the intake air / fuel ratio sensors 25 and 26 and the exhaust air / fuel ratio sensor 27.

[2. Control configuration]
The engine ECU 35 is provided with an idle stop control unit 35a, an opening / closing control unit 35b, a motor control unit 35c, and a correction control unit 35d as functional elements for performing the above-described reference value correction.

  The idle stop control unit 35a determines whether or not a predetermined automatic stop condition (idle stop condition) is satisfied, and automatically stops the engine 1 when it is determined that the automatic stop condition is satisfied. Stopping the engine 1 here means stopping combustion injection from the injector 4. That is, even if the crankshaft is slightly rotating due to inertia, the engine 1 is stopped if the fuel injection is stopped. In addition, the automatic stop condition is, for example, that the vehicle speed is zero and the brake operation is performed, the vehicle speed is zero and the accelerator operation is not performed, or the like. As the control configuration of the idle stop control unit 35a, various known techniques can be applied, and details thereof are omitted.

  The open / close control unit (reflux gas control means) 35b controls the opening degree (open / close) of the first control valve 20 and the second control valve 23 that control the recirculation gas flowing through the recirculation passages 19 and 22. The opening / closing control unit 35b controls the amount of the recirculated gas by adjusting the opening degrees of the first control valve 20 and the second control valve 23 from the relationship with the output request to the engine 1, the exhaust temperature, and the like. Further, the opening / closing control unit 35b reduces the opening of the first control valve 20 and the second control valve 23 in order to reduce the reflux gas when receiving a reflux gas cutoff command described later from the correction control unit 35d. Suppresses the flow of reflux gas. Here, when the open / close control unit 35b receives the recirculation gas cutoff command, the first control valve 20 and the second control valve 35b are set in order to bring the recirculation gas amount to zero, which is the most suitable state for the reference value correction. The valve 23 is completely closed and the reflux gas is shut off.

  The motor control unit (electric motor control means) 35c controls the electric motor 34 that assists the engine 1 with electric power (that is, cranks without fuel injection). Here, the electric motor 34 is a drive source of the vehicle 40 together with the engine 1, and the motor control unit 35 c operates the electric motor 34 as a motor or a generator based on a command from the vehicle ECU 41. In addition, when the motor control unit 35c receives a command to electrically assist the engine 1 from the correction control unit 35d, the motor control unit 35c performs control to electrically assist the engine 1 (hereinafter, this control is referred to as motoring). That is, when receiving the above command from the correction control unit 35d, the motor control unit 35c operates the electric motor 34 to rotate the crankshaft of the engine 1 to perform electric assist. Thereby, even when fuel injection is stopped in the engine 1, the piston 3 is slid back and forth in the vertical direction.

  The correction control unit (correction control means) 35d determines whether or not the reference value correction of the oxygen concentration of the air-fuel ratio sensors 25, 26 and 27 is necessary, and when it is determined that it is necessary, the open / close control unit 35b and A command is issued to the motor control unit 35c to cause the control units 35b and 35c to perform control for correcting the reference value. Here, in order to perform the reference value correction of the intake system air-fuel ratio sensors 25 and 26 and the exhaust system air-fuel ratio sensor 27, the oxygen concentrations in the intake passage 12 and the exhaust passage 16 are set to be equal to the atmospheric state, respectively. It is necessary to do. Further, here, the pressures in the intake passage 12 and the exhaust passage 16 are also made equal to the atmospheric pressure, the influence of the pressure is eliminated, and the reference value correction of the intake system air-fuel ratio sensors 25 and 26 and the exhaust system air-fuel ratio sensor 27 is performed more accurately. To implement. Hereinafter, the determination content and control content (command content) performed by the correction control unit 35d will be described.

  First, the correction control unit 35d determines whether or not the travel distance of the vehicle 40 is equal to or greater than a predetermined distance set in advance. The correction control unit 35d determines that the reference value correction of the air-fuel ratio sensors 25, 26 and 27 is necessary when it is determined that the travel distance is equal to or greater than the predetermined distance, and the reference value when it is determined that the travel distance is less than the predetermined distance. It is determined that no correction is necessary. That is, this determination is a determination as to whether or not the reference value correction for the air-fuel ratio sensors 25, 26 and 27 is necessary. Hereinafter, the condition that “the travel distance is equal to or greater than the predetermined distance” for determining that the reference value needs to be corrected is referred to as a correction condition.

  The travel distance here is the distance traveled after the previous correction of the reference values of the air-fuel ratio sensors 25, 26 and 27. That is, the travel distance is accumulated after the reference value correction is completed, and when the reference value correction is performed, the travel distance accumulated so far is reset to zero and the accumulation is started again. The predetermined distance, which is the determination threshold, is a distance until the air-fuel ratio sensors 25, 26, and 27 start to cause an error in the sensor value due to a change over time, and is obtained in advance through experiments or the like.

  If the correction control unit 35d determines that the above correction condition is satisfied, the correction control unit 35d next determines whether or not the engine 1 is stopped. The engine 1 is stopped when, for example, the idle stop control unit 35a determines that the automatic stop condition is satisfied and the engine 1 is stopped in response to a command to stop the engine 1, or the engine 1 is stopped. This is a case where the vehicle is running only with the electric motor 34. Since the intake is stopped by stopping the engine 1, the pressure in the intake passage 12 and the exhaust passage 16 becomes equal to the atmospheric pressure. In the present embodiment, the turbocharger 18 is provided. However, since this operation is also stopped when the engine 1 is stopped, there is no pressure change due to supercharging.

  If the correction control unit 35d determines that the engine 1 is stopped, the correction control unit 35d issues a command to the motor control unit 35c to electrically assist the engine 1, operates the motor 34, and starts motoring. Simultaneously with this command, the correction control unit 35d issues a command to the opening / closing control unit 35b to close both the first control valve 20 and the second control valve 23, and sets the amount of the recirculation gas to zero. That is, when the engine 1 is stopped, the exhaust gas in the intake passage 12 and the exhaust passage 16 is cleaned by cutting the recirculated gas and operating the motor 34 for motoring. In other words, only fresh air flows through the intake passage 12 and the exhaust passage 16, and the oxygen concentration in the intake passage 12 and the exhaust passage 16 is made equal to the oxygen concentration in the atmosphere.

  Further, the correction control unit 35d starts a timer at the same time as issuing the electric assist command, and measures the motoring time. Then, when the motoring time becomes equal to or longer than the predetermined time, a command is issued to the motor control unit 35c to stop the electric motor 34, the electric motor 34 is stopped, and the motoring is finished. That is, the correction control unit 35d operates the electric motor 34 for a predetermined time after determining that the engine 1 is stopped, and scavenges exhaust gas in the intake passage 12 and the exhaust passage 16.

  The predetermined time referred to here is the time taken to scavenge all exhaust gas, and the engine speed by the motor 34 and the total extension of the intake passage 12 and the exhaust passage 16 (the total volume of the intake passage 12 and the exhaust passage 16). ) And set. That is, the predetermined time is set shorter as the engine speed detected by the crank angle sensor 31 is faster, and longer as the engine speed is slower, according to the preset total extension of the intake passage 12 and the exhaust passage 16. Is done. In addition to this, the predetermined time may be set according to the shape of the intake passage 12 and the exhaust passage 16, the flow path resistance, and the like.

  When the engine 1 is automatically stopped, the correction control unit 35d determines that the pressure in the intake passage 12 detected by the intake system pressure sensor 28 and the pressure in the exhaust passage 16 detected by the exhaust system pressure sensor 29 are both atmospheric pressures. It is determined whether or not the atmospheric pressure detected by the sensor 30 is equivalent. When the engine 1 is automatically stopped, the pressure in the intake passage 12 and the exhaust passage 16 should be equal to the atmospheric pressure. However, in order to further improve the accuracy of correction, the pressure is actually detected to detect the atmospheric pressure. It is determined whether or not they are equivalent. When the correction control unit 35d determines that the pressure in the intake passage 12 is equal to the atmospheric pressure, the correction control unit 35d determines that the reference value correction of the intake air-fuel ratio sensors 25 and 26 can be performed, and the pressure in the exhaust passage 16 Is determined to be equivalent to the atmospheric pressure, it is determined that the reference value correction of the exhaust system air-fuel ratio sensor 27 can be performed. In addition, the oxygen concentration and pressure in the intake passage 12 and the exhaust passage 16 are “equivalent” to the state of the atmosphere, which means that the oxygen concentration and the pressure need not substantially coincide with each other. That is, an error of several percent is allowed.

  When the correction control unit 35d determines that the reference value correction of the air-fuel ratio sensors 25, 26, and 27 can be performed, the correction control unit 35d performs the reference value correction of the oxygen concentration of the air-fuel ratio sensors 25, 26, and 27. In the engine ECU 35, the relationship (map as shown in FIG. 3) of outputs from the air-fuel ratio sensors 25, 26 and 27 with respect to the oxygen concentration (air-fuel ratio) is stored in advance for each sensor. When the correction control unit 35d determines that the reference value correction can be performed, the correction control unit 35d performs correction of the map.

Reference value correction of the air-fuel ratio sensors 25, 26 and 27 performed by the correction control unit 35d will be described with reference to FIG. Although the air-fuel ratio sensor 25 will be described here as an example, the same applies to the air-fuel ratio sensors 26 and 27. FIG. 3 is a graph showing the relationship between the sensor value (output) and the actual air-fuel ratio (oxygen concentration). When the air-fuel ratio sensor 25 is new, it has a relationship between the output and the air-fuel ratio such as a graph a shown by the solid line in FIG. 3, the sensor value at the point P _A on the graph a when the air-fuel ratio is A X _a is detected.

However, when the air-fuel ratio sensor 25 changes with time, an error occurs in the output. For example, as shown in FIG. 3, even if the actual air-fuel ratio is A, the output from the air-fuel ratio sensor 25 becomes X _B , and an error ΔX (= X _A −X _B ) occurs in the sensor value. In other words, when the output from the air-fuel ratio sensor 25 is X _B , the point P _A ′ is shown on the graph a, so that the air-fuel ratio at this time is determined to be A ′, but the actual air-fuel ratio is A. As a result, a deviation occurs in the air-fuel ratio. Therefore, in order to know how much this error exists, the actual air-fuel ratio is set to a known value, and the sensor value output from the air-fuel ratio sensor 25 at this time is an output signal (sensor) corresponding to this known air-fuel ratio. If not (value), the sensor value error corresponding to that is stored. Then, at the time of detection by the air-fuel ratio sensor 25 after the next time, the stored air-fuel ratio is added or subtracted to determine the actual air-fuel ratio.

For example, when the actual air-fuel ratio (here, oxygen concentration) is a known value of atmospheric oxygen concentration A (about 21%), the sensor value to be output by the air-fuel ratio sensor 25 must be X _A. It is assumed that the sensor value X _B is output though it is necessary. Since the sensor value error at this time is ΔX (= X _A −X _B ), this ΔX is stored in the engine ECU 35. From this time on, the actual oxygen concentration can be detected by always adding this error ΔX to the sensor value output by the air-fuel ratio sensor 25.

That is, the correction control unit 35d performs correction to shift the graph a shown in FIG. 3 to the right so that the sensor value X _B is output when the oxygen concentration is A (that is, the point P _B ). A new graph b showing the relationship of the output to the air-fuel ratio in the changed air-fuel ratio sensor 25 is created. In the subsequent detection by the air-fuel ratio sensor 25, it is possible to detect an accurate air-fuel ratio in consideration of the time-dependent change of the air-fuel ratio sensor 25 by using this graph b.

[3. flowchart]
Next, an example of a procedure for correcting the reference values of the air-fuel ratio sensors 25, 26 and 27 performed by the correction control unit 35d of the engine ECU 35 will be described with reference to FIG. This flowchart operates at a predetermined cycle. Each of the following steps is performed by each function (means) assigned to the hardware of the computer being operated by software (computer program).
When the driver turns on the ignition switch (IG_SW) of the vehicle, the control flow shown in FIG. 4 starts.

  As shown in FIG. 4, first, in step S10, it is determined whether or not the flag F = 0. Here, the flag F is a variable for checking whether or not the correction condition is satisfied in the correction control unit 35d described above, and the flag F = 0 is set at the start of the control. Therefore, at the start of control, the YES route is obtained in step S10, and the process proceeds to step S20. In step S20, it is determined whether or not the travel distance is greater than or equal to a predetermined distance. If the travel distance is equal to or greater than the predetermined distance, the process proceeds from the YES route to step S30, the flag F is set to F = 1, and the process proceeds to step S40. On the other hand, if the travel distance is less than the predetermined distance, the control flow is returned to the NO route. Therefore, after the travel distance becomes equal to or greater than the predetermined distance, the flow after step S40 is repeated unless the state of the flag F changes.

  In step S40, it is determined whether or not the engine 1 is stopped. When the engine 1 is stopped, the process proceeds from the YES route to step S50, the opening / closing control unit 35b is made to close both the first control valve 20 and the second control valve 23, and the motor control unit 35c is driven to the electric motor. 34 is activated (motoring start). Thereby, scavenging of the exhaust gas remaining in the intake passage 12 and the exhaust passage 16 is performed. Also, a timer is started simultaneously with the start of motoring, and the motoring time is measured.

  Next, in step S60, it is determined whether the motoring time is a predetermined time or more. When the motoring time is less than the predetermined time, the process proceeds to the NO route, the control flow is returned, and the process proceeds to step S10. At this time, if the flag F is set to F = 1 in the previous step S30, the process proceeds from the NO route to step S40 in the determination of step S10. In step S40, it is determined again whether the engine 1 is stopped. When the engine 1 is stopped, the process proceeds to step S60 through step S50, and is repeated until the motoring time reaches a predetermined time or more.

  On the other hand, if the engine 1 is not stopped in step S40, the process proceeds from the NO route to step S45. In step S45, whether motoring is in progress (that is, whether the first control valve 20 and the second control valve 23 are both closed by the opening / closing control unit 35b and the motor 34 is operated by the motor control unit 35c). It is determined whether or not. If motoring is in progress, the process proceeds from the YES route to step S55, and the operation of the motor 34 and the control of the first control valve 20 and the second control valve 23 (control of the reflux gas) are performed in the normal operation mode (that is, the engine 1). The motor control unit 35c and the open / close control unit 35b are instructed to return to the opening degree according to the output request or the exhaust temperature, etc. (motoring is stopped), the measured motoring time is reset, and the control flow is Returned. If it is determined in step S45 that the motoring is not in progress, the process proceeds to the NO route and the control flow is returned as it is.

  That is, even when it is determined that the reference value correction of the air-fuel ratio sensors 25, 26 and 27 is necessary and the flag F is set to F = 1, when the engine 1 is not stopped, the control flow Is returned and the reference value correction is not performed. In this case, since the flag F is set to F = 1 in Step S30, the control flow is repeated until it is determined in Step S10 that the engine 1 is always stopped in Step S40. It is.

  If it is determined in step S60 that the motoring time is equal to or longer than the predetermined time, the process proceeds from the YES route to step S70, and motoring is stopped. In step S80, it is determined whether or not the intake pressure is equal to atmospheric pressure. If the intake pressure is equal to atmospheric pressure, the process proceeds from the YES route to step S90, and whether or not the exhaust pressure is equal to atmospheric pressure. Is determined. When the exhaust pressure is equal to the atmospheric pressure, the process proceeds from the YES route to step S100, and the reference value correction of the air-fuel ratio sensors 25, 26, and 27 is performed. Next, in step S110, the flag F is reset to F = 0, and the control flow is returned.

  On the other hand, if it is determined in step S80 or step S90 that the intake pressure or the exhaust pressure is not equal to the atmospheric pressure, the process proceeds from the NO route to step S120, and the intake pressure or the exhaust pressure is equal to the atmospheric pressure for some reason. Therefore, the process proceeds to step S110, where the flag F is returned to F = 0 and the control flow is returned. That is, originally, if the engine 1 is stopped, the intake pressure and the exhaust pressure should be equal to the atmospheric pressure. However, since this is not established in this control cycle, the reference value correction is performed in this control cycle. The reference value correction is performed when the condition is satisfied in the next and subsequent control cycles.

[4. effect]
Therefore, according to the present control device, the exhaust of the intake / exhaust system of the engine 1 can be scavenged by operating the electric motor 34 for a predetermined time when the engine 1 is stopped. Equivalent state can be achieved. Further, since the engine 1 is stopped, the pressure of the intake / exhaust system is equal to the atmospheric pressure. Since the reference value correction of the air-fuel ratio sensors 25, 26 and 27 is performed in this state, the correction can be performed accurately with a simple configuration.

  Further, since the exhaust system has less chance of the oxygen concentration being equal to that of the atmosphere due to the influence of the combustion gas, and the learning frequency is low, an error in the sensor value with respect to the actual air-fuel ratio increases due to the time-dependent change of the exhaust system air-fuel ratio sensor 27 easy. On the other hand, in the present control device, the exhaust in the exhaust passage 16 is scavenged by the electric motor 34, so that the oxygen concentration in the exhaust passage 16 can be made equal to the atmosphere. Further, the pressure in the exhaust passage 16 can be made equal to the atmospheric pressure by stopping the engine 1. In this state, since the reference value correction of the exhaust system air-fuel ratio sensor 27 disposed in the exhaust passage 16 is performed, the correction can be performed with high accuracy.

  Further, at this time, the exhaust system pressure sensor 29 actually detects the pressure of the exhaust passage 16 to check whether it is equal to the atmospheric pressure detected by the atmospheric pressure sensor 30. Since the reference value correction of the sensor 27 is performed, the exhaust system air-fuel ratio sensor 27 can be corrected more accurately.

Further, when the engine 1 is stopped, the recirculation gas amount is decreased by the opening / closing control unit 35b, and the electric motor 34 is operated for a predetermined time to scavenge the exhaust gas introduced into the intake passage 12, so that the intake air-fuel ratio The reference values can be corrected with high accuracy for the sensors 25 and 26 as well.
Further, at this time, the pressure in the intake passage 12 is actually detected by the intake system pressure sensor 28 to check whether or not it is equal to the atmospheric pressure detected by the atmospheric pressure sensor 30. Since the reference values of the sensors 25 and 26 are corrected, the intake air-fuel ratio sensors 25 and 26 can be corrected with higher accuracy.

Further, the travel distance is accumulated by the correction control unit 35d, and when the accumulated travel distance is equal to or greater than a predetermined distance, the reference value is corrected to thereby obtain the reference points of the air-fuel ratio sensors 25, 26, and 27 at an appropriate timing. Correction can be performed.
In addition, since the electric motor 34 is a driving electric motor and is applied to the hybrid vehicle 40 that can run only by the electric motor 34, the air-fuel ratio sensor 25, if the engine 1 is stopped even when the vehicle 40 is running. Reference value corrections 26 and 27 can be implemented. That is, the frequency at which the reference value correction of the air-fuel ratio sensors 25, 26, and 27 can be performed increases, and the measurement accuracy of the air-fuel ratio sensors 25, 26, and 27 can be maintained high.

[5. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above embodiment, when determining whether or not to perform the reference value correction, the determination is first made based on the travel distance. However, the correction is always performed when a condition for performing the correction is satisfied regardless of the travel distance. You may comprise as follows. In this case, the measurement accuracy of the air-fuel ratio sensors 25, 26 and 27 can be maintained in a high state.

Instead of determining whether or not the engine 1 is stopped, it is determined whether or not the automatic stop condition is satisfied, and the correction control unit 35d stops the engine 1 when the automatic stop condition is satisfied. You may comprise. That is, the correction control unit 35d may actively stop the engine 1 instead of waiting for the engine 1 to stop.
The predetermined time for operating the electric motor 34 after determining that the engine 1 is stopped may be a fixed value set in advance.

Further, the present invention is not limited to the case where the recirculation gas is completely shut off, and the recirculation gas is slightly introduced into the intake passage 12 as long as the oxygen concentration in the intake passage 12 can be made equal to the oxygen concentration in the atmosphere. May be.
Further, the air-fuel ratio sensor for which the reference value is corrected by the present control device may not be a linear air-fuel ratio sensor that detects an output substantially proportional to the oxygen concentration as described above. Further, the air-fuel ratio sensor does not have to detect the oxygen concentration. Any sensor that can measure at least the amount of a gaseous substance related to the combustion reaction may be used. For example, a sensor that detects the air-fuel ratio by detecting the carbon dioxide concentration may be used. That is, the air-fuel ratio sensor is not limited to the one that detects the oxygen concentration, and the reference value correction is not limited to the oxygen concentration reference value correction.

  Further, the configuration of the engine 1 is not limited to that shown in FIG. The positions of the exhaust system air-fuel ratio sensor 27 and the exhaust system pressure sensor 29 are not limited to those described above. For example, it may be disposed on the upstream side of the turbine, and in the case where an exhaust purification device is further provided on the downstream side of the exhaust purification device 17, it is disposed on the downstream side of the exhaust purification device 17. It may be. For example, the reflux path may be one of the first reflux path 19 and the second reflux path 22. In this case, only one air-fuel ratio sensor needs to be provided. Moreover, the structure which is not provided with the recirculation | reflux passage may be sufficient, and an intake system air fuel ratio sensor is unnecessary in this case. Further, the turbocharger 18 may not be provided.

  Further, the present control device is not limited to a vehicle equipped with a diesel engine, but can be applied to a vehicle equipped with a gasoline engine. The present control device is not limited to a hybrid vehicle, and can be applied to any vehicle that can electrically assist the engine, such as a cell motor.

1 Diesel engine (engine)
12 Intake passage 16 Exhaust passage 19 First return passage (return passage)
20 First control valve (reflux gas control means)
22 Second reflux passage (reflux passage)
23 Second control valve (reflux gas control means)
25, 26 Intake air-fuel ratio sensor (air-fuel ratio sensor)
27 Exhaust air / fuel ratio sensor (air / fuel ratio sensor)
28 Intake system pressure sensor 29 Exhaust system pressure sensor 30 Atmospheric pressure sensor 34 Motor generator (motor)
35 Engine ECU
35a Idle stop control unit (idle stop control means)
35b Open / close control unit (reflux gas control means)
35c Motor control unit (motor control means)
35d Correction control unit (correction control means)
40 vehicles (hybrid vehicles)

Claims (7)

An engine control device comprising: an engine having an electric motor capable of applying a driving force for mechanically driving the engine at least without combustion; and an air-fuel ratio sensor disposed in an intake / exhaust system of the engine There,
Motor control means for controlling the motor;
Correction control means for causing the electric motor control means to operate the electric motor when the engine is stopped, and to stop the electric motor after a lapse of a predetermined time and to perform a reference value correction of the air-fuel ratio sensor. Control device. 2. The engine control apparatus according to claim 1, wherein the air-fuel ratio sensor is an exhaust air-fuel ratio sensor disposed in an exhaust passage of the engine. An exhaust system pressure sensor for detecting the pressure of the exhaust passage;
3. The correction control means performs reference value correction of the exhaust system air-fuel ratio sensor if the pressure of the exhaust passage detected by the exhaust system pressure sensor is equal to atmospheric pressure. The engine control device described. A recirculation passage for exhaust gas recirculation communicating the exhaust passage and the intake passage of the engine, and a recirculation gas control means for controlling a recirculation gas amount flowing through the recirculation passage;
The air-fuel ratio sensor is an intake air-fuel ratio sensor disposed in the intake passage downstream of a connection portion between the intake passage and the return passage;
The engine according to any one of claims 1 to 3, wherein when the correction control means determines that the engine is stopped, the recirculation gas control means decreases the recirculation gas amount. Control device. An intake system pressure sensor for detecting the pressure of the intake passage;
5. The correction control means performs a reference value correction of the intake system air-fuel ratio sensor if the pressure of the intake passage detected by the intake system pressure sensor is equal to atmospheric pressure. The engine control device described. The said correction control means implements the said reference value correction | amendment, if the distance which drive | worked after completion | finish of the reference value correction | amendment of the said air-fuel ratio sensor of the last time is more than the predetermined distance set beforehand, The engine control device according to any one of claims 5 to 6. The electric motor is a driving electric motor used as a driving source of a vehicle;
The engine control apparatus according to any one of claims 1 to 6, wherein the vehicle is a hybrid vehicle capable of traveling using at least one of the engine and the electric motor as a drive source.

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