JP4063311B1 - Control device for hybrid vehicle - Google Patents

Abstract

Deterioration of exhaust emission in a hybrid vehicle is avoided.
When the engine is restarted (YES in S1000), the engine ECU detects the air-fuel ratio of the exhaust by an air-fuel ratio sensor when the timer is started (S1100) and when the time is up (YES in S1200). If step (S1300), the air-fuel ratio detected by the air-fuel ratio sensor is in the lean region (YES in S1400), an air-fuel ratio sensor response abnormality detection step (S1500), and the engine intermittent operation permission flag are turned off The program is executed including the step of disabling intermittent operation (S1600) and the step of changing the gain of the air-fuel ratio feedback control to a small value (S1700).
[Selection] Figure 4

Description

  The present invention relates to control of a hybrid vehicle, and more particularly to a technique for controlling an engine mounted on a hybrid vehicle in order to avoid deteriorating exhaust emission.

In general, an exhaust system of an engine is provided with a catalytic converter for purifying exhaust gas. As the catalytic converter, a three-way catalytic converter has been widely used, which reduces nitrogen oxide (NOx) as well as oxidation of carbon monoxide in the exhaust gas (CO) and unburned hydrocarbons (HC) Thus, carbon dioxide (CO ₂ ), water vapor (H ₂ O), and nitrogen (N ₂ ) are converted.

  The purification characteristics of the three-way catalytic converter depend on the air-fuel ratio of the air-fuel mixture formed in the combustion chamber, and the three-way catalytic converter functions most effectively when it is close to the stoichiometric air-fuel ratio. This is because if the air-fuel ratio is lean and the amount of oxygen in the exhaust gas is large, the oxidizing action becomes active but the reducing action becomes inactive, and if the air-fuel ratio is rich and the amount of oxygen in the exhaust gas is small, On the contrary, the reduction action becomes active, but the oxidation action becomes inactive, and all the above three components cannot be purified well. Therefore, an engine having a three-way catalytic converter is provided with, for example, an output linear type oxygen sensor in its exhaust passage, and the oxygen concentration measured thereby is used to calculate the air-fuel ratio of the air-fuel mixture in the combustion chamber. Feedback control is performed so that the fuel ratio becomes a stoichiometric air fuel ratio (hereinafter, sometimes referred to as stoichiometric).

  In addition, an engine that operates with the combustion energy of fuel and a motor that operates with electric energy are provided as a power source when the vehicle travels, and an automatic transmission (power split mechanism is installed between the power source and the drive wheels. Hybrid vehicles equipped with the above are put into practical use. In such a hybrid vehicle, for example, by using the engine and the motor properly according to the driving state, it is possible to reduce the fuel consumption amount and the exhaust gas amount while maintaining a predetermined traveling performance. Specifically, an engine running mode in which only the engine is used as a power source, a motor running mode in which the vehicle is run using only the motor as a power source (with the engine stopped), and an engine + motor that runs using both the engine and the motor as power sources. It has a plurality of operation modes with different operating states of the engine and the motor, such as a driving mode, and a power source map or the like that has a predetermined parameter such as a vehicle speed (or a power source rotation speed) and an operation amount of an accelerator is predetermined. Switching is automatically performed according to mode switching conditions. That is, the engine is intermittently operated even when the vehicle is running.

  In such a hybrid vehicle, it is necessary to detect various sensor signals and switch signals, and control to stop the engine and restart the engine again when a predetermined engine stop condition is satisfied. There is (for example, it can be said that such an operating state of the engine is a state of intermittent operation described above). Even in an engine mounted on a hybrid vehicle that repeatedly stops and restarts the engine, the air-fuel mixture in the combustion chamber becomes the stoichiometric air-fuel ratio (target air-fuel ratio) for purifying exhaust gas as described above. Thus, the intake air amount is detected and the fuel injection amount is feedback controlled.

  Specifically, the air-fuel ratio of the air-fuel mixture is controlled in the vicinity of the stoichiometric state by feedback control based on an output from an oxygen sensor provided in front of the three-way catalytic converter. A general sensor (for example, a zirconia oxygen sensor) as this oxygen sensor generally has a step-like change in output voltage value when the amount of oxygen in the exhaust gas becomes minute. The output voltage value of the oxygen sensor is stoichiometrically empty. The air-fuel ratio becomes minute on the lean side from the stoichiometric side and the air-fuel ratio becomes larger than a predetermined value on the rich side from the stoichiometric side.

  Therefore, in the air-fuel ratio feedback control, when the output voltage value of the oxygen sensor exceeds a predetermined value, the target air-fuel ratio is corrected so that the air-fuel ratio increases as the air-fuel ratio is richer than stoichiometric, and the oxygen sensor When the output voltage value becomes less than a predetermined value, the target air-fuel ratio is corrected so that the air-fuel ratio is decreased with the air-fuel ratio being leaner than the stoichiometry, and the fuel injection amount is controlled.

  The oxygen sensor is a sensor whose output value changes in accordance with the oxygen concentration of the component contained in the exhaust gas. For example, the oxygen sensor may be an air-fuel ratio sensor in which the output value has a substantially linear relationship with the air-fuel ratio. Alternatively, an oxygen sensor whose output value changes greatly with the theoretical air-fuel ratio as a boundary may be used. Such an oxygen sensor is sometimes called an exhaust sensor. In the following, an oxygen sensor, an air-fuel ratio sensor, and an exhaust sensor are used without distinction.

  In such a hybrid vehicle, since the engine, the motor, and the drive shaft are mechanically connected without a clutch mechanism, the engine is in a downstream exhaust sensor in a no-load operation state or a low-load operation state. As a result, the sensor output value of the downstream exhaust sensor does not accurately reflect the actual oxygen concentration in the exhaust gas. There were some things that could not be done with accuracy. Japanese Patent Laying-Open No. 2006-63822 (Patent Document 1) discloses an engine control system that can suppress control disturbance caused by a downstream exhaust sensor. This engine control system is an engine control system mounted on a hybrid vehicle that controls input / output of engine power and motor power to a drive shaft, and includes an exhaust purification catalyst for purifying engine exhaust, and an exhaust purification catalyst. A downstream exhaust sensor installed on the downstream side, an operating state determining means for determining whether or not the sensor output value of the downstream exhaust sensor is in a predetermined operating state that does not accurately reflect actual exhaust, and an operating state Control prohibiting means for prohibiting at least a part of the control based on the sensor output value of the downstream side exhaust sensor when the determination means determines that the vehicle is in the predetermined operating state.

According to this engine control system, it is mounted on a hybrid vehicle that controls input / output of engine power and motor power with respect to the drive shaft, and performs control based on the sensor output value of the downstream exhaust sensor. This engine control system performs at least a part of the control based on the sensor output value of the downstream exhaust sensor when the sensor output value of the downstream exhaust sensor does not accurately reflect actual exhaust. Ban. Therefore, disturbances in control (air-fuel ratio learning control, catalyst deterioration control) caused by the downstream exhaust sensor can be suppressed.
JP 2006-63822 A

  During the intermittent operation of the engine in the hybrid vehicle, the exhaust gas becomes lean when the engine is stopped (since fuel injection is stopped), and the atmosphere (air-fuel ratio) in the three-way catalytic converter is always lean. When the engine is restarted, NOx is not reduced and purified in a three-way catalytic converter in a lean atmosphere, so that the exhaust emission is not deteriorated. The air-fuel ratio in the catalytic converter is stoichiometric to rich.

  By the way, when the responsiveness of the air-fuel ratio sensor that detects the air-fuel ratio is not good (when a response delay time occurs), the lean state detected when the engine is temporarily stopped until the rich state after restart is detected. Variations in response delay time may occur. This variation may occur between individual air-fuel ratio sensors, even with the same air-fuel ratio sensor, with aging, or with different detection timings even with the same air-fuel ratio sensor. Such variation is a factor in which the feedback control is not stable because the start timing of the air-fuel ratio feedback control is determined when the rich state is detected from the lean state detected during the temporary stop.

  However, Patent Document 1 described above merely discloses that control (for example, feedback control) using the exhaust sensor is prohibited when the exhaust sensor does not accurately reflect the actual exhaust state. . When such feedback control is prohibited, the air-fuel ratio may be controlled to be close to the stoichiometric range by open loop control.

  In the case of open loop control, control is performed so that the air-fuel ratio is close to the stoichiometric range, but actual control is not performed based on the difference between the actual air-fuel ratio and the target air-fuel ratio as in feedback control. That is, in the open loop control, the correction coefficient for feedback control is held in a state where there is no correction. For this reason, for example, even when the air-fuel ratio is detected to be deviated from the actual lean side (actually, it is detected that the air-fuel ratio is lean due to the response delay of the air-fuel ratio sensor even though it is not lean). If the time is longer), the state where the feedback control is prohibited continues, and there is a possibility that the fuel increase correction is performed excessively. At this time, exhaust emission is deteriorated. In particular, in a hybrid vehicle in which engine stop and restart are repeated, such exhaust emission may be deteriorated every time the engine is restarted.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a control device for a hybrid vehicle that avoids deterioration of exhaust emission.

  The control device according to the first invention controls a hybrid vehicle having an internal combustion engine and a power source other than the internal combustion engine as a travel source of the vehicle. The control device is configured to temporarily stop the internal combustion engine when the vehicle condition satisfies the temporary stop condition, and to control the internal combustion engine so as to restart the internal combustion engine when the restart condition is satisfied; Based on the detection means provided in the exhaust system of the internal combustion engine for detecting the air-fuel ratio of the exhaust, and the catalyst mechanism provided in the exhaust system of the internal combustion engine is optimized based on the detected air-fuel ratio Therefore, the feedback control means for performing feedback control so that the air-fuel ratio becomes the target air-fuel ratio, and the response delay of the detection means when the internal combustion engine is restarted after the internal combustion engine is temporarily stopped. It includes determination means for determining whether or not there is an abnormality, and prohibition means for prohibiting the temporary stop of the internal combustion engine by the control means when it is determined that the response delay is abnormal.

  According to the first aspect of the invention, a response delay occurs in sensors called an air-fuel ratio sensor, an oxygen sensor, an exhaust sensor and the like that are detection means for detecting the air-fuel ratio of the exhaust. On the other hand, feedback control is performed on the basis of the air-fuel ratio detected by the detection means so that the target air-fuel ratio (the target air-fuel ratio for optimizing the exhaust gas purification characteristics by the catalyst mechanism is stoichiometric). For this reason, when an abnormal response delay that exceeds the allowable range occurs, the control stability of the feedback control is not compensated, and the air-fuel ratio control may diverge and exhaust emission may deteriorate. Therefore, when it is determined that such a response delay is abnormal, temporary stop (and restart) of the internal combustion engine is prohibited. Thereby, since the internal combustion engine is not temporarily stopped, it is possible to avoid the deterioration of exhaust emission at the time of restart even if the response delay of the detecting means is abnormal. As a result, it is possible to provide a control device for a hybrid vehicle that avoids deterioration of exhaust emission.

  The control device according to the second aspect of the invention controls the internal combustion engine such that the internal combustion engine is temporarily stopped when the vehicle state satisfies the temporary stop condition, and is restarted when the restart condition is satisfied. A control means provided in the exhaust system of the internal combustion engine for detecting the air-fuel ratio of the exhaust, and a catalyst mechanism provided in the exhaust system of the internal combustion engine based on the detected air-fuel ratio. In order to optimize the purification characteristics, feedback control means for performing feedback control so that the air-fuel ratio becomes the target air-fuel ratio, and detection after the internal combustion engine is temporarily stopped and restarted Determining means for determining whether or not the response delay of the means is abnormal, and changing means for changing the gain in the feedback control means when it is determined that the response delay is abnormal.

  According to the second invention, the control stability of the feedback control is not compensated when an abnormal response delay that causes the detection means to exceed the allowable range occurs, and the air-fuel ratio control diverges and the exhaust emission is reduced. It can get worse. Therefore, when it is determined that such a response delay is abnormal, the gain in the feedback control means is changed (for example, small). As a result, since the gain in the air-fuel ratio feedback control is not large, even when the internal combustion engine is restarted, the exhaust air-fuel ratio is actually rich, but it is lean due to a response delay by the detection means. Even if the feedback deviation is large, the control amount is not significantly changed (here, the fuel injection amount is greatly increased), so that the divergence of the air-fuel ratio feedback control can be easily avoided. As a result, it is possible to provide a control device for a hybrid vehicle that avoids deterioration of exhaust emission.

  In the control device according to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, the changing means includes means for changing the gain small.

  According to the third invention, in order to change the gain in the feedback control means to a small value, even if the air-fuel ratio of the exhaust gas is actually rich when the internal combustion engine is restarted, the detection means delays the response. Even if it is lean and the feedback deviation is large, the fuel injection amount is not greatly increased. For this reason, it is possible to easily avoid the divergence of the air-fuel ratio feedback control.

  In the control device according to the fourth aspect of the present invention, in addition to the configuration of any one of the first to third aspects, the determination unit is configured to detect by the detection unit when a predetermined time has elapsed since the restart of the internal combustion engine. If the detected air-fuel ratio is in the lean region, means for determining that the response delay is abnormal is included.

  According to the fourth invention, even if a predetermined time has elapsed since the restart of the internal combustion engine, if the air-fuel ratio detected by the detection means is still in the lean region, the response delay time is too long. Thus, it can be determined that the response delay is abnormal. Note that, at this predetermined time, the air-fuel ratio detected by the detecting means is detected even though the internal combustion engine is restarted and the actual air-fuel ratio is at least stoichiometric and sufficiently in the rich region. Is set to a time during which it is possible to determine that the response delay of the detection means is abnormal based on the fact that is in the lean region.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. In the following, an engine having two three-way catalytic converter catalysts will be described, but any engine having one or more three-way catalytic converters may be used. Further, the hybrid system is not limited as long as the engine intermittently operates while the vehicle is running.

  With reference to FIG. 1, the control block diagram of the whole hybrid vehicle including the control apparatus which concerns on embodiment of this invention is demonstrated. The present invention is not limited to the hybrid vehicle shown in FIG. In the present invention, an internal combustion engine such as a gasoline engine (hereinafter referred to as an engine) as a power source may be a drive source for driving a vehicle and a generator drive source. Furthermore, the drive source is an engine and a motor generator, and the vehicle is capable of traveling by the power of the motor generator, and the hybrid is provided with a battery for traveling that may stop the engine during traveling. It may be a vehicle. This battery is a nickel metal hydride battery or a lithium ion battery, and the type thereof is not particularly limited. A capacitor may be used instead of the battery.

  The hybrid vehicle includes an engine 120 and a motor generator (MG) 140. In the following, for convenience of explanation, the motor generator 140 is expressed as a motor generator 140A (or MG (2) 140A) and a motor generator 140B (or MG (1) 140B). Accordingly, motor generator 140A functions as a generator, or motor generator 140B functions as a motor. Regenerative braking is performed when this motor generator functions as a generator. When the motor generator functions as a generator, the kinetic energy of the vehicle is converted into electric energy, and the vehicle is decelerated.

  In addition to this, the hybrid vehicle transmits a power generated by the engine 120 and the motor generator 140 to the drive wheels 160, and transmits a drive of the drive wheels 160 to the engine 120 and the motor generator 140, and an engine. Power split mechanism (for example, a planetary gear mechanism described later) 200 that distributes the power generated by 120 to two paths of drive wheel 160 and motor generator 140B (MG (1) 140B), and motor generator 140 for driving Traveling battery 220 for charging electric power, and inverter that performs current control while converting the direct current of traveling battery 220 and the alternating current of motor generator 140A (MG (2) 140A) and motor generator 140B (MG (1) 140B) 240 and charging / discharging of traveling battery 220 A battery control unit (hereinafter referred to as a battery ECU (Electronic Control Unit)) 260 that manages and controls a state (for example, SOC (State Of Charge)), an engine ECU 280 that controls the operating state of the engine 120, and a hybrid vehicle state. Accordingly, MG_ECU 300 that controls motor generator 140, battery ECU 260, inverter 240, and the like, and battery ECU 260, engine ECU 280, MG_ECU 300, etc. are mutually managed and controlled so that the hybrid vehicle can operate most efficiently. HV_ECU 320 and the like are included.

  In the present embodiment, boost converter 242 is provided between battery for traveling 220 and inverter 240. This is because the rated voltage of battery for traveling 220 is lower than the rated voltage of motor 140A (MG (2) 140A) or motor generator 140B (MG (1) 140B), so that motor generator 140A (MG (2) When power is supplied to 140A) or motor generator 140B (MG (1) 140B), the boost converter 242 boosts the power.

  In FIG. 1, each ECU is configured separately, but may be configured as an ECU in which two or more ECUs are integrated (for example, MG_ECU 300 and HV_ECU 320 are integrated as shown by a dotted line in FIG. 1). An example of this is the ECU.

  In power split mechanism 200, a planetary gear mechanism (planetary gear) is used to distribute the power of engine 120 to both drive wheel 160 and motor generator 140B (MG (1) 140B). By controlling the rotation speed of motor generator 140B (MG (1) 140B), power split device 200 also functions as a continuously variable transmission. The rotational force of the engine 120 is input to the carrier (C), which is output to the motor generator 140B (MG (1) 140B) by the sun gear (S), and the motor generator 140A (MG (2) 140A) and output by the ring gear (R). It is transmitted to the shaft (drive wheel 160 side). When the rotating engine 120 is stopped, since the engine 120 is rotating, the kinetic energy of this rotation is converted into electric energy by the motor generator 140B (MG (1) 140B), and the rotational speed of the engine 120 is reduced. Let

  In a hybrid vehicle equipped with a hybrid system as shown in FIG. 1, if a predetermined condition is satisfied for the state of the vehicle, HV_ECU 320 uses only motor generator 140A (MG (2) 140A) of motor generator 140 to hybrid vehicle. The engine 120 is controlled via motor generator 140A (MG (2) 140A) and engine ECU 280 so that the vehicle travels as follows. For example, the predetermined condition is a condition that the SOC of traveling battery 220 is equal to or greater than a predetermined value. In this way, the hybrid vehicle can be driven only by the motor generator 140A (MG (2) 140A) when the engine 120 is inefficient at the time of starting or running at a low speed. As a result, the SOC of the traveling battery 220 can be reduced (the traveling battery 220 can be charged when the vehicle is subsequently stopped).

  Further, during normal travel, for example, the power split mechanism 200 divides the power of the engine 120 into two paths, and on the other hand, the drive wheels 160 are directly driven, and on the other hand, the motor generator 140B (MG (1) 140B) is driven to generate power. To do. At this time, motor generator 140A (MG (2) 140A) is driven by the generated electric power to assist driving of driving wheels 160. Further, at the time of high speed traveling, the electric power from the traveling battery 220 is further supplied to the motor generator 140A (MG (2) 140A) to increase the output of the motor generator 140A (MG (2) 140A) to the driving wheel 160. To add driving force. On the other hand, at the time of deceleration, motor generator 140 </ b> A (MG (2) 140 </ b> A) driven by drive wheel 160 functions as a generator to perform regenerative power generation, and the collected power is stored in traveling battery 220. When the amount of charge of traveling battery 220 is reduced and charging is particularly necessary, the output of engine 120 is increased to increase the amount of power generated by motor generator 140B (MG (1) 140B), and traveling battery 220 is increased. Increase the amount of charge for.

  In addition, the target SOC of traveling battery 220 is normally set to about 60% so that energy can be recovered no matter when regeneration is performed. Further, the upper limit value and the lower limit value of the SOC are set, for example, with the upper limit value set to 80% and the lower limit value set to 30% in order to suppress the deterioration of the battery of the traveling battery 220. The HV_ECU 320 is set via the MG_ECU 300. Thus, power generation and regeneration by the motor generator 140 and motor output are controlled so that the SOC does not exceed the upper limit value and the lower limit value. In addition, the value quoted here is an example and is not a particularly limited value.

  The power split mechanism 200 will be further described with reference to FIG. The power split mechanism 200 includes a sun gear (S) 202 (hereinafter simply referred to as the sun gear 202), a pinion gear 204, a carrier (C) 206 (hereinafter simply referred to as the carrier 206), and a ring gear (R) 208 ( Hereinafter, it is composed of a planetary gear including a ring gear 208).

  Pinion gear 204 is engaged with sun gear 202 and ring gear 208. The carrier 206 supports the pinion gear 204 so that it can rotate. Sun gear 202 is coupled to the rotation shaft of MG (1) 140B. Carrier 206 is connected to the crankshaft of engine 120. Ring gear 208 is connected to the rotation shaft of MG (2) 140A and reduction gear 180.

  Engine 120, MG (1) 140B and MG (2) 140A are connected via power split mechanism 200 formed of a planetary gear, so that the rotational speeds of engine 120, MG (1) 140B and MG (2) 140A Are connected by a straight line in the nomograph.

  With reference to FIG. 3, engine 120 mounted on the hybrid vehicle will be described. As shown in FIG. 3, to engine 120, an intake system 1152 and an exhaust system 1154 including a first three-way catalytic converter 1200 and a second three-way catalytic converter 1300 are connected. Note that the number of three-way catalytic converters is not limited to two and may be one or more.

  Intake system 1152 includes an intake passage 1110, an air cleaner 1118, an air flow meter 1104, a throttle motor 1114A, a throttle valve 1112, and a throttle position sensor 1114B.

  Air taken in from air cleaner 1118 passes through intake passage 1110 and circulates to engine 120. A throttle valve 1112 is provided in the middle of the intake passage 1110. Throttle valve 1112 is opened and closed by throttle motor 1114 </ b> A that operates based on a control signal from engine ECU 280 so that a desired amount of air is supplied to engine 120. At this time, the opening degree of the throttle valve 1112 can be detected by the throttle position sensor 1114B. An air flow meter 1104 is provided in the intake passage between the air cleaner 1118 and the throttle valve 1112 to detect the amount of intake air. The air flow meter 1104 transmits the intake air intake amount signal to the engine ECU 280.

  Engine 120 includes a cooling water passage 1122, a cylinder block 1124, an injector 1126, a piston 1128, a crankshaft 1130, a water temperature sensor 1106, and a crank position sensor 1132.

  Pistons 1128 are respectively provided in the number of cylinders corresponding to the number of cylinders of the cylinder block 1124. The mixture of the fuel injected from the injector 1126 and the intake air is introduced into the combustion chamber above the piston 1128 through the intake passage 1110, and burns by ignition of the ignition plug whose ignition timing is controlled. When combustion occurs, the piston 1128 is pushed down. At this time, the vertical motion of the piston 1128 is converted into a rotational motion of the crankshaft 1130 via the crank mechanism. The engine speed NE of the engine 120 is detected by the engine ECU 280 based on a signal detected by the crank position sensor 1132.

  A cooling water passage 1122 is provided in the cylinder block 1124, and the cooling water circulates by the operation of a water pump (not shown). The cooling water in the cooling water passage 1122 flows to a radiator (not shown) connected to the cooling water passage 1122 and is radiated by a cooling fan (not shown). A water temperature sensor 1106 is provided on the cooling water passage 1122 and detects the temperature of the cooling water in the cooling water passage 1122. The water temperature sensor 1106 transmits the detected water temperature to the engine ECU 280 as an engine cooling water temperature detection signal.

  Exhaust system 1154 is provided in exhaust passage 1108, first three-way catalytic converter 1200 that is integrated with, for example, the exhaust manifold of engine 120, for example, on the under floor, in order to increase the temperature of engine 120 due to heat. Second three-way catalytic converter 1300. An air-fuel ratio sensor is provided on the upstream side of the first three-way catalytic converter 1200 and on the upstream side of the second three-way catalytic converter 1300 (downstream side of the first three-way catalytic converter 1200). Furthermore, a temperature sensor that detects the temperatures of the first three-way catalytic converter 1200 and the second three-way catalytic converter 1300 may be provided.

  As described above, the exhaust passage 1108 connected to the exhaust side of the engine 120 is connected to the first three-way catalytic converter 1200 and the second three-way catalytic converter 1300. That is, the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber in the engine 120 first flows into the first three-way catalytic converter 1200. HC and CO contained in the exhaust gas flowing into the first three-way catalytic converter 1200 are oxidized in the first three-way catalytic converter 1200. Further, NOx contained in the exhaust gas flowing into the first three-way catalytic converter 1200 is reduced in the first three-way catalytic converter 1200. The first three-way catalytic converter 1200 is installed near the engine 120 (may be integrated with the exhaust manifold as described above), and the temperature is quickly raised even when the engine 120 is cold started. To express the catalytic function.

  Further, the exhaust gas is sent from the first three-way catalytic converter 1200 to the second three-way catalytic converter 1300 for the purpose of purification. The first three-way catalytic converter 1200 and the second three-way catalytic converter 1300 basically have the same structure and function.

  First air-fuel ratio sensor 1210 provided upstream of first three-way catalytic converter 1200, provided downstream of first three-way catalytic converter 1200 and upstream of second three-way catalytic converter 1300 The second air-fuel ratio sensor 1310 thus detected detects the concentration of oxygen contained in the exhaust gas passing through the first three-way catalytic converter 1200 or the second three-way catalytic converter 1300. By detecting the oxygen concentration, it is possible to detect the so-called air-fuel ratio of the fuel and air contained in the exhaust gas.

  The first air-fuel ratio sensor 1210 and the second air-fuel ratio sensor 1310 generate a current corresponding to the oxygen concentration in the exhaust gas. This current is converted into a voltage, for example, and input to engine ECU 280. Accordingly, the air-fuel ratio of the exhaust gas upstream of the first three-way catalytic converter 1200 can be detected from the output signal of the first air-fuel ratio sensor 1210, and the second output signal from the second air-fuel ratio sensor 1310 can be detected. The air-fuel ratio of the exhaust gas upstream of the three-way catalytic converter 1300 can be detected. The first air-fuel ratio sensor 1210 and the second air-fuel ratio sensor 1310 generate, for example, a voltage of about 0.1 V when the air-fuel ratio is lean, and a voltage of about 0.9 V when the air-fuel ratio is rich. It is what happens. The value converted into the air-fuel ratio based on these values is compared with the air-fuel ratio threshold value, and air-fuel ratio control is performed by engine ECU 280.

  The first three-way catalytic converter 1200 and the second three-way catalytic converter 1300 function to reduce NOx while oxidizing HC and CO when the air-fuel ratio is substantially the stoichiometric air-fuel ratio, that is, simultaneously perform HC, CO, and NOx. Has the function of purifying.

  Engine ECU 280, which is a control device according to the present embodiment, determines whether or not the responsiveness of the air-fuel ratio sensor is abnormal (determines that the responsiveness is abnormal when the response delay time is large). When the responsiveness of the fuel ratio sensor is abnormal, intermittent operation of the engine 120 is prohibited and the magnitude of the air-fuel ratio feedback control is changed. These will be described in detail below.

  The engine 120 is stopped by a command from the HV_ECU 320, the exhaust gas becomes lean, and the air-fuel ratio in the first three-way catalytic converter 1200 and the second three-way catalytic converter 1300 is always lean. In such a case, when the engine 120 restart command is received from the HV_ECU 320, the engine 120 is restarted. However, in a lean atmosphere, NOx is not reduced and purified, and exhaust emission deteriorates. For this reason, when the engine 120 is restarted, start-up fuel increase control is executed to make the air-fuel ratio in the first three-way catalytic converter 1200 and the second three-way catalytic converter 1300 stoichiometric to rich.

  However, if such start-up fuel increase control is executed when the response delay of the air-fuel ratio sensor is large, the air-fuel ratio control is not stabilized and exhaust emission deteriorates. Therefore, engine ECU 280, which is a control device according to the present embodiment, prohibits intermittent operation of engine 120 and determines air-fuel ratio feedback control when it is determined that the responsiveness is abnormal when the response delay time is large. The magnitude of the gain is changed small. In the following description, it is determined whether or not the responsiveness of the first air-fuel ratio sensor 1210 is abnormal, and abnormal processing is performed. In addition to the first air-fuel ratio sensor 1210, Instead, the abnormality process may be performed based on the responsiveness of the second air-fuel ratio sensor 1310.

  Such a control device according to the present embodiment is read out from a CPU (Central Processing Unit) and a memory included in the ECU and executed by the CPU even in hardware mainly composed of a digital circuit or an analog circuit. It can also be realized by software mainly composed of programs to be executed. In general, it is said that it is advantageous in terms of operation speed when realized by hardware, and advantageous in terms of design change when realized by software. Below, the case where a control apparatus is implement | achieved as software is demonstrated. Note that a recording medium on which such a program is recorded is also an embodiment of the present invention.

  With reference to FIG. 4, a control structure of a program executed by engine ECU 280 in order to realize the control device according to the present embodiment will be described. This program is a subroutine and is repeatedly executed at a predetermined cycle time.

  In step (hereinafter, step is referred to as S) 1000, engine ECU 280 determines whether or not engine 120 has started restarting. In general, based on an operation command for the engine 120 from the HV_ECU 320, the engine ECU 280 cranks the engine 120 that has temporarily stopped operation by a starter motor, and air is sucked and fuel is injected and mixed. It is determined that the engine 120 has restarted when the fire is continuously ignited. If it is determined that engine 120 has restarted (YES in S1000), the process proceeds to S1100. If not (NO in S1000), the process returns to S1000 and waits until engine 120 is restarted. If NO in S1000, this process (subroutine) may be terminated.

  In S1100, engine ECU 280 starts a timer. Note that this timer expires when the set time ΔT elapses. The set time ΔT corresponds to the air-fuel ratio detected by the first air-fuel ratio sensor 1210 even though the engine 120 is restarted and the actual air-fuel ratio is at least stoichiometric and is sufficiently rich. Is set to a time during which the first air-fuel ratio sensor 1210 can determine that the response delay is abnormal based on the fact that is in the lean region. Therefore, the set time ΔT is a value that is appropriately changed based on the characteristics of the first air-fuel ratio sensor 1210 and the position where the first air-fuel ratio sensor 1210 is installed.

  In S1200, engine ECU 280 determines whether or not the timer for which ΔT is set has expired. When the timer expires (YES in S1200), the process proceeds to S1300. If not (NO in S1200), the process returns to S1200 and waits for time-up.

  In S1300, engine ECU 280 detects the air-fuel ratio of the exhaust gas. At this time, engine ECU 280 detects the air-fuel ratio of the exhaust gas based on the signal input from first air-fuel ratio sensor 1210.

  In S1400, engine ECU 280 determines whether or not the detected air-fuel ratio is within a lean region. If the detected air-fuel ratio is within the lean region (YES in S1400), the process proceeds to S1500. Otherwise (NO in S1400), this process ends. That is, it is determined that there is no response delay of the first air-fuel ratio sensor 1210, and the abnormal process (S1500 to S1700) when there is a response delay of the first air-fuel ratio sensor 1210 is not executed.

  In S1500, engine ECU 280 detects an abnormality in responsiveness of first air-fuel ratio sensor 1210. In S1600, engine ECU 280 turns off the intermittent operation permission flag of engine 120. That is, the intermittent operation of the engine 120 is prohibited without permitting it. In S1700, engine ECU 280 changes the gain of air-fuel ratio feedback control. At this time, in a state where the feedback gain is large, the control amount is greatly manipulated with respect to the deviation (difference between the target air-fuel ratio and the detected air-fuel ratio detected on the lean side) (the fuel injection amount is increased further). ) When the responsiveness abnormality of the first air-fuel ratio sensor 1210 is detected, since this deviation itself is not accurate, the gain is changed small to prevent divergence in the feedback control system. Note that the processing in S1600 and the processing in S1700 may be selectively executed.

  The operation of engine 120 controlled by engine ECU 280, which is the control device according to the present embodiment, based on the above-described structure and flowchart will be described with reference to FIG.

[Normal response of first air-fuel ratio sensor]
At time T (1) in FIG. 5, engine 120 is restarted (YES in S1000), and a timer set with ΔT is started (S1100). At time T (2) when set time ΔT has elapsed since engine 120 was restarted (YES in S1200), air-fuel ratio is detected by first air-fuel ratio sensor 1210.

  If the detected air-fuel ratio is not within the lean region (NO in S1400), this process ends and it is determined that there is no response delay of first air-fuel ratio sensor 1210. Therefore, the abnormality process (S1500 to S1700) when there is a response delay of the first air-fuel ratio sensor 1210 is not executed.

  The state at this time is the change in the air-fuel ratio indicated by the solid line in FIG. The first air-fuel ratio sensor 1210 detects a sufficiently rich region value at time T (2) when the set time ΔT has elapsed from time T (1) when the engine 120 is restarted. For this reason, the engine intermittent operation permission flag remains set (on).

[The response of the first air-fuel ratio sensor is abnormal]
Similar to the above-described operation, at time T (1) in FIG. 5, engine 120 is restarted (YES in S1000), and a timer set with ΔT is started (S1100). At time T (2) when set time ΔT has elapsed since engine 120 was restarted (YES in S1200), air-fuel ratio is detected by first air-fuel ratio sensor 1210.

  If the detected air-fuel ratio is within the lean region (YES in S1400), the response abnormality of first air-fuel ratio sensor 1210 (abnormality in which an unacceptable response delay has occurred) is detected (S1500). .

The state at this time is a change in the air-fuel ratio indicated by the dotted line in FIG. The first air-fuel ratio sensor 1210 is still detecting the value in the lean region at time T (2) when the set time ΔT has elapsed from time T (1) when the engine 120 was restarted. Note that the air-fuel ratio value detected by the first air-fuel ratio sensor 1210 is in the stoichiometric region at time t (4) in FIG. 5, and is in the rich region after time t (4). In other words, the first air-fuel ratio sensor 1210 is abnormal in response, and the first air-fuel ratio sensor 1210 itself is not abnormal. In order to distinguish between abnormality in the responsiveness of the first air-fuel ratio sensor 1210 and abnormality in the first air-fuel ratio sensor 1210 itself, for example, the following processing may be performed.
(1) The engine ECU 280 monitors (monitors) the air-fuel ratio detected by the first air-fuel ratio sensor 1210 even after time T (3) after the time is up, and the detected air-fuel ratio enters the rich region. By confirming this (for example, time T (4) in FIG. 5), it can be determined that the air-fuel ratio sensor 1210 itself is not abnormal.
(2) Regardless of the timer, the engine ECU 280 monitors (monitors) the air-fuel ratio detected by the first air-fuel ratio sensor 1210 after the engine 120 is restarted, and the detected air-fuel ratio is in the lean region. However, it can be determined that the air-fuel ratio sensor 1210 itself is not abnormal by confirming that it changes to the rich region side with the passage of time (for example, in the vicinity of time T (2) in FIG. 5).

  As an abnormal process when there is a response delay of the first air-fuel ratio sensor 1210, the engine intermittent operation permission flag is changed from the set state to the reset state (switched from on to off) (S1600). This is indicated by a dotted line of the intermittent engine operation permission flag in FIG.

  Further, when the air-fuel ratio feedback gain is changed to a small value and the responsiveness abnormality occurs in the first air-fuel ratio sensor 1210, even if the feedback deviation is large, the control amount is largely manipulated to avoid the feedback control being diverged. it can.

  As described above, according to the engine ECU that is the control device according to the present embodiment, the abnormality in the responsiveness of the air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas of the engine that is intermittently operated in the hybrid vehicle is accurately detected. can do. When an abnormality in the response of the air-fuel ratio sensor is detected, intermittent engine operation is prohibited. Thereby, it is possible to avoid deterioration of the exhaust emission of the engine. Further, when an abnormality in the responsiveness of the air-fuel ratio sensor is detected, the control gain of the air-fuel ratio feedback control is changed. Thereby, it is possible to avoid the divergence of the air-fuel ratio feedback control of the engine.

  In the flowchart shown in FIG. 4, the abnormality of the air-fuel ratio sensor response is determined based on the fact that the air-fuel ratio is lean when ΔT has elapsed since the engine 120 was restarted. The process for determining the responsiveness abnormality is not limited to this process.

  Further, the value detected by the air-fuel ratio sensor is monitored until the timer expires, and if a change to lean is detected, it is determined that the responsiveness of the air-fuel ratio sensor is not abnormal. It doesn't matter.

  Furthermore, the history of determining that the response of the air-fuel ratio sensor is abnormal may be stored as a diagnosis, and a specific lamp on the instrument panel is turned on or blinked to notify the driver. It does not matter if you make it.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a control block diagram of an entire hybrid vehicle including a control device according to an embodiment of the present invention. It is a figure which shows a power split mechanism. It is a control block diagram of an engine which is a control target of an engine ECU which is a control device according to an embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by engine ECU which is a control apparatus which concerns on embodiment of this invention. 5 is a timing chart showing temporal changes in the state of the engine when the flowchart shown in FIG. 4 is executed.

Explanation of symbols

  120 Engine, 140 Motor Generator, 160 Drive Wheel, 180 Reducer, 200 Power Dividing Mechanism, 220 Travel Battery, 240 Inverter, 242 Boost Converter, 260 Battery ECU, 280 Engine ECU, 300 MG_ECU, 320 HV_ECU, 1104 Air Flow Meter 1106 Water temperature sensor 1108 Exhaust passage 1110 Intake passage 1112 Throttle valve 1114A Throttle motor 1114B Throttle position sensor 1118 Air cleaner 1122 Cooling water passage 1124 Cylinder block 1126 Injector 1128 Piston 1130 Crankshaft 1132 Crank Position sensor, 1152 Intake system, 1154 Exhaust system, 1200 First three One-way catalytic converter, 1300 Second three-way catalytic converter.

Claims (7)

A control device for a hybrid vehicle having an internal combustion engine and a power source other than the internal combustion engine as a travel source of the vehicle,
Control means for controlling the internal combustion engine to temporarily stop the internal combustion engine when the vehicle condition satisfies a temporary stop condition and restart the internal combustion engine when the restart condition is satisfied;
A detecting means provided in an exhaust system of the internal combustion engine for detecting an air-fuel ratio of the exhaust;
Feedback for performing feedback control so that the air-fuel ratio becomes the target air-fuel ratio in order to optimize the exhaust gas purification characteristics by the catalyst mechanism provided in the exhaust system of the internal combustion engine based on the detected air-fuel ratio. Control means;
Determination means for determining whether or not the response delay of the detection means is abnormal after the internal combustion engine is temporarily stopped and when the internal combustion engine is restarted;
And a prohibiting means for prohibiting temporary stop of the internal combustion engine by the control means when it is determined that the response delay is abnormal. A control device for a hybrid vehicle having an internal combustion engine and a power source other than the internal combustion engine as a travel source of the vehicle,
Control means for controlling the internal combustion engine to temporarily stop the internal combustion engine when the vehicle condition satisfies a temporary stop condition and restart the internal combustion engine when the restart condition is satisfied;
A detecting means provided in an exhaust system of the internal combustion engine for detecting an air-fuel ratio of the exhaust;
Feedback for performing feedback control so that the air-fuel ratio becomes the target air-fuel ratio in order to optimize the exhaust gas purification characteristics by the catalyst mechanism provided in the exhaust system of the internal combustion engine based on the detected air-fuel ratio. Control means;
Determination means for determining whether or not the response delay of the detection means is abnormal after the internal combustion engine is temporarily stopped and when the internal combustion engine is restarted;
And a changing unit for changing a gain in the feedback control unit when it is determined that the response delay is abnormal.   The control device according to claim 2, wherein the changing unit includes a unit for changing the gain to a small value.   The determination means determines that the response delay is abnormal if a predetermined time has elapsed since the restart of the internal combustion engine and the air-fuel ratio detected by the detection means is within a lean region. The control apparatus in any one of Claims 1-3 containing the means for. The determination means determines whether or not the response delay is abnormal in a state where the detection means is in a normal state after the internal combustion engine is temporarily stopped and when the internal combustion engine is restarted. The control apparatus in any one of Claims 1-4 containing the means for. The determination means is such that the air-fuel ratio detected by the detection means is within a lean region when a predetermined time has elapsed since the restart of the internal combustion engine, and the time further than the predetermined time is reached. 6. A means for determining that the response delay is abnormal when the air-fuel ratio detected by the detection means is within a rich region when the elapsed time is within a normal state. The control device described in 1. The determination means is such that the air-fuel ratio detected by the detection means is within a lean region when a predetermined time has elapsed since the restart of the internal combustion engine, and the air-fuel ratio detected by the detection means is rich. The control device according to claim 5, further comprising means for determining that the response delay is abnormal in a state where the detection means is in a normal state when the state is shifted to the side.

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