JP2008274858A - Condensate quantity detection device and sensor heating control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condensate quantity detection device and a sensor heating control device for an internal combustion engine, which more accurately detect the condition around an object sensor, and suitably avoid or suppress a trouble which can occur owing to the drive of a heat generating device installed on the sensor. <P>SOLUTION: An ECU for an engine control is provided with a program for detecting a quantity of condensate formed in an exhaust gas passage by operation thereof when an object engine is started and stopped before reaching sufficient operation duration, and acquiring new condensate quantity Qw1 and remaining condensate quantity Qw2 corresponding to a parameter indicating quantity of the condensate and parameter determined with using the quantity of the condensate. The ECU is also provided with a program variably setting control style relating to drive quantity of a heater heating oxygen concentration sensor provided in the exhaust gas passage of the engine according to the sum of quantity of remaining condensate and quantity of new condensate newly formed during start of this time when the engine is started. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is applied to an internal combustion engine that converts energy generated by fuel combustion in a cylinder into mechanical motion (for example, rotational motion), and is generated mainly in an intake passage or an exhaust passage of the engine when the engine is started. The present invention relates to a condensed water amount detection device for detecting a condensed water amount, and a sensor heating control device suitable for use in activating a sensor (for example, an oxygen concentration sensor) provided in an intake passage or an exhaust passage of the engine.

  As is well known, as an engine control system for controlling an internal combustion engine used for power of an automobile or the like, for example, an exhaust purification device such as a three-way catalyst is properly operated or a combustion state or fuel consumption (fuel consumption rate) is improved. For example, a system for controlling an air-fuel ratio (= weight of air / weight of fuel) is known. In particular, in-vehicle gasoline engines, a system that feedback-controls the air-fuel ratio in the exhaust discharged from the cylinder that performs fuel combustion of the engine to the theoretical air-fuel ratio (≈ “14.8”) has been widely adopted. Yes. Specifically, in such a system, an oxygen concentration sensor that outputs a detection signal corresponding to the oxygen concentration in the exhaust is installed in the exhaust passage of the engine, and the sensor output of this oxygen concentration sensor (a detection signal indicating the oxygen concentration in the exhaust) And the target value (value corresponding to the theoretical air-fuel ratio), for example, the drive amount of each actuator that supplies fuel and air for combustion in the cylinder, that is, the injection time of the fuel injection valve, Variable opening control of intake throttle valve. In this way, the supply amount of fuel and air supplied for combustion in the cylinder is controlled to a desired value, and the air-fuel ratio in the exhaust is brought close to (preferably matched) the stoichiometric air-fuel ratio, So-called air-fuel ratio feedback control is performed.

  As the oxygen concentration sensor used in such a system, a sensor element made of a zirconia element, for example, is well known. This sensor uses a voltage (electromotive force) generated according to the oxygen concentration difference between the atmosphere and the gas to be detected as an output (sensor output). The reliability of the sensor output (generated electromotive force) depends on the temperature of the sensor element. That is, this type of sensor normally exhibits a high detection capability when the sensor element is in a predetermined temperature range (active state) higher than room temperature. For this reason, when using such a sensor, it is important to perform control to maintain the temperature of the sensor element in an active temperature region of, for example, “650 ° C.” or higher in order to ensure high detection accuracy. Specifically, for example, an electric heater (heat generating device) is provided in the sensor element, and the sensor element can be maintained in an active state by adjusting (controlling to a desired amount) the energization amount of the heater. When the air-fuel ratio feedback control is performed using such a sensor, the temperature of the sensor element is controlled to the active temperature region as described above prior to the execution of the control. In general, the air-fuel ratio feedback control described above is executed on condition that the sensor element is in an active state. Note that the temperature of the sensor element can be estimated based on, for example, the resistance value of the sensor element.

  However, zirconia and the like used as a solid electrolyte material for gas sensors including such oxygen concentration sensors are generally easily cracked. In particular, when the internal combustion engine is started, the engine is still cold and the amount of saturated water vapor (the maximum amount of water vapor contained in the air) is small. For this reason, the environment is such that the moisture contained in the exhaust gas becomes droplets and easily adheres to the sensor (an environment in which the sensor is easily wet). If, for example, a heater attached to the sensor is driven to activate the sensor in such a wet state, the sensor element may be cracked due to a change in stress.

Therefore, conventionally, as described in Patent Document 1, for example, it is determined whether or not liquid droplets are present in the exhaust pipe when the engine is started, and the determination indicates that liquid droplets are present. A sensor heating control device that restricts the drive amount (energization amount) of the electric heater attached to the sensor to a small amount for a predetermined time (standby time) when determined. In this apparatus, the amount of heating of the sensor is limited in this way, so that the sensor life is shortened and the sensor is not damaged (or suppressed) due to the above-mentioned crack.
JP 2004-69644 A

  However, in such a device, although it can be determined whether or not the water is wet, how long the standby time is set when the sensor is wet can avoid the above-mentioned crack occurrence. It ’s not clear if we can do it. Therefore, in order to surely avoid the occurrence of the above-mentioned crack, it has been necessary to set a standby time longer than necessary.

  The present invention has been made in view of such circumstances, and more suitably detects inconveniences that may occur in association with the driving of the heat generating device mounted on the sensor by detecting the state around the target sensor with higher accuracy. The main object of the present invention is to provide a condensed water amount detection device and a sensor heating control device for an internal combustion engine that can be avoided or suppressed.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  In the first aspect of the present invention, when the internal combustion engine is stopped before the engine reaches a sufficient operating time (for example, the operating time is compared with a predetermined threshold). The amount of condensed water generated in the intake passage or the exhaust passage of the internal combustion engine by the operation, and a parameter indicating the amount of condensed water, and a parameter obtained using the amount of condensed water, A condensed water amount acquisition means for acquiring a condensed water amount parameter corresponding to one of the above is provided.

  According to the inventors' experiments and the like, the main cause of the sensor (for example, oxygen concentration sensor) provided in the exhaust passage (or intake passage) of the engine (internal combustion engine) getting wet is in the exhaust passage (or intake passage). The condensed water (especially condensed water accumulated on the bottom of the passage). That is, by starting the engine, the condensed water accumulated on the bottom surface of the passage is scattered by the momentum (force of airflow) of exhaust (or intake air), and the sensor gets wet. When the inventor conducted further experiments, paying attention to this condensate, when a short-term operation that stops immediately after the engine is started is performed, the condensate generated by the operation remains at the next start. It was confirmed. The condensate remaining in this way (residual condensate) scatters to allow the sensor to get wet at the next start. Therefore, in order to avoid inconveniences associated with sensor water exposure, it is important to obtain the amount of condensed water remaining (residual condensed water amount) due to short-term operation. In this regard, according to the apparatus of the first aspect, it is possible to acquire a parameter indicating the amount of condensed water (or a parameter obtained using the amount of condensed water) by the condensed water amount acquisition means. Then, the acquired parameters can more suitably avoid or suppress inconveniences that may occur when the heat generating device attached to the sensor is driven.

  In this case, in order to avoid the occurrence of cracks or the like due to the sensor heating in the above-described wet condition, the sensor heating (heater drive) start timing is based on, for example, the condensed water amount parameter acquired by the condensed water amount acquisition means. A configuration in which the heating amount is variably set is effective.

  Further, it is also effective to remove the residual condensed water generated by the previous short-term operation before starting the engine. In this case, for example, by providing an electric heater or the like around the pipe (intake passage or exhaust passage) or around the cylinder, it is possible to remove by heating (evaporate). Alternatively, the cylinder or piping is heated by heat (for example, frictional heat) generated by driving the engine output shaft and forcibly moving (for example, rotating) the output shaft by an engine starter (starter device). The residual condensed water may be removed by heating.

  Also, in the case of performing sensor heating control, that is, preheating control for starting sensor heating, that is, energization (heating of the heater) to a heating device (for example, an electric heater) attached to the sensor, just before engine start. It is also effective to determine the presence or absence (execution / stop) of sensor heating based on the condensed water amount parameter acquired by the condensed water amount acquisition means prior to the execution of sensor heating (preheating).

  According to a second aspect of the present invention, in the apparatus according to the first aspect, the amount of condensed water acquired by the condensed water amount acquiring unit with respect to a predetermined storage device capable of holding data even after the internal combustion engine is stopped. Condensed water storage means for storing parameters is provided.

  In order to detect the amount of condensed water at the time of engine start with high accuracy, it is important to store the condensed water amount parameter in a usable state at the next operation when the engine is stopped. In this regard, according to the configuration of the second aspect, it is possible to store the condensed water amount parameter more easily and in a usable state during the next operation.

  With regard to the device according to claim 2, as in the invention according to claim 3, each time the internal combustion engine is started, the condensation stored in the storage device is based on the operation time until the stop. By providing the condensed water amount updating means for updating the water amount parameter, the condensed water amount parameter can be maintained at a highly accurate value.

  According to a fourth aspect of the present invention, in the apparatus according to the third aspect, when the operation time until the stop of the condensed water amount update means is sufficiently long (for example, judgment is made in comparison with a predetermined threshold), When the condensate amount parameter stored in the storage device is reset and the operation time until the stop is not sufficiently long, the condensate amount acquisition means this time with respect to the condensate amount parameter stored in the storage device The acquired condensed water amount parameter is added.

  The above-mentioned residual condensed water accumulates as a short-term operation continues. On the other hand, once it has been operated for a long time, it is usually removed (evaporated). The invention according to claim 4 is based on such an event, and according to such an apparatus, the condensed water amount parameter can be obtained with high accuracy.

  The condensed water amount parameter may be reset when the engine is stopped, or when the operation time is found to be sufficiently long (for example, when a predetermined time has elapsed after the engine is started).

  In addition, the inventor is highly reproducible about the relationship between the condition defined by the current engine operation time and the temperature of the engine body at that time (the condition related to the generation of condensed water) and the amount of condensed water generated by the current operation. The inventors have found that the following relationship can be obtained (for example, see FIG. 12), and invented the following apparatus. That is, according to a fifth aspect of the present invention, in the apparatus according to any one of the first to fourth aspects, the condensate amount acquisition means is stopped from the start of the engine with a parameter indicating the body temperature of the internal combustion engine. The estimated value is acquired as the condensed water amount parameter by estimating the amount of condensed water generated by the operation based on the operation time until. With such a configuration, the condensed water amount parameter can be obtained (estimated) with high accuracy.

  The parameters indicating the main body temperature of the internal combustion engine include a plurality of types of predetermined parameters (for example, the cooling water temperature of the engine, the lubricating oil temperature of the engine, the intake air temperature, the outside air temperature, the intake and exhaust system piping temperature, etc.) It is effective to use the lowest detection value. With such a configuration, it is possible to more reliably prevent (or suppress) the occurrence of cracks or the like due to the above-described sensor heating in the wet state in response to a detection error in the body temperature of the internal combustion engine. Is possible.

  Moreover, the inventor invented the device according to claims 6 to 14 as a device for using the amount of condensed water remaining in the short-term operation described above (residual condensed water amount) for sensor heating control. Hereinafter, each of these devices will be described.

  First, in the invention according to the sixth aspect, the heat generating device is installed in the intake passage or the exhaust passage of the internal combustion engine in a predetermined temperature range in a state where the heat generating device that generates heat in the driving state and increases the driving amount as the driving amount increases. A device (sensor heating control device) that is applied to a predetermined target sensor that is activated at a high temperature (for example, “100 ° C. or higher”) and exhibits a high detection capability (sensor heating control device), the internal combustion engine When starting the heating control, the control mode relating to the drive amount of the heat generating device is variably set according to the sum of the amount of residual condensed water remaining and the amount of new condensed water newly generated by the current start Means are provided.

  With such a device, the amount of residual condensate remaining at the start of the engine (internal combustion engine), which has not been considered in the past, will be taken into account. The driving amount of the heat generating device (corresponding to the sensor heating device) is set based on As a result, it is possible to more suitably perform the heating control of the target sensor while avoiding or suppressing inconvenience that may occur due to the driving of the heat generating device (sensor heating device).

  In this case, the heating control means is also used as a period prior to normal driving of the heat generating device based on the sum of the residual condensed water amount and the new condensed water amount, as in the invention described in claim 7. It is effective to variably set the length of the delay period (delay time), which is a period during which driving is prohibited or limited (for example, the driving amount of the heat generating device is made smaller than in the case of normal control). By doing so, it is possible to more suitably prevent (or suppress) the occurrence of cracks and the like due to the sensor heating in the above-described wet condition. In this case, the heating control means sets the length of the delay period (delay time) to a longer time as the sum of the residual condensed water amount and the new condensed water amount is larger. Is more effective.

  The apparatus according to claim 6 or 7 can be suitably realized by using the apparatus according to any one of claims 1 to 5 described above. That is, in the invention according to claim 8, in the apparatus according to claim 6 or 7, the heating control means uses the internal combustion engine according to any one of claims 1 to 5 as the residual condensed water amount. The condensed water amount parameter acquired by the condensed water amount acquisition means in the condensed water amount detection apparatus is used. By doing so, the amount of residual condensed water can be acquired (detected) more easily and accurately.

  By the way, each said sensor heating control apparatus is invention made | formed by the inventors paying attention to the new parameter which is residual condensed water. Therefore, the present invention is particularly effective when applied to the case where the sensor gets wet due to the scattering of residual condensed water as described above. As a particularly useful configuration, for example, the configurations described in claims 9 to 13 are conceivable. Hereinafter, each of these devices will be described.

  According to a ninth aspect of the present invention, in the apparatus according to any one of the sixth to eighth aspects, the target sensor is an exhaust gas provided in an exhaust passage through which exhaust gas is discharged after the combustion stroke of the internal combustion engine. It is a system sensor, and the amount of residual condensed water and the amount of new condensed water are the amount of condensed water accumulated in a depression (concave portion) of an exhaust passage formed near the exhaust upstream side of the target sensor.

  When a depression (recess) is formed near the exhaust upstream side of the exhaust system sensor in the exhaust passage, the exhaust condensed water tends to accumulate therein. And the sensor water | moisture content mentioned above will be caused by the condensed water in the hollow fundamentally. For this reason, it becomes possible to perform sensor heating control more suitably by acquiring (detecting) the condensed water in the hollow as the residual condensed water amount and the new condensed water amount.

  According to a tenth aspect of the present invention, in the apparatus according to the ninth aspect, the depression (recess) is in a vertical direction of an exhaust passage of the internal combustion engine in a use state (for example, mounted in a vehicle). It is formed on the lower side.

  If it is such a structure, it will become easy to accumulate condensed water in a hollow according to gravity. And it becomes easy for a sensor to get wet with the condensed water in this hollow. For this reason, each said sensor heating control apparatus is especially useful when applied to such a structure.

  According to an eleventh aspect of the present invention, in the apparatus according to the ninth or tenth aspect, the recess (concave portion) is formed in a flange for connecting an exhaust pipe forming an exhaust passage of the internal combustion engine. It is characterized by being.

  According to a twelfth aspect of the present invention, in the apparatus according to the eleventh aspect, the target sensor is mounted on the upper side in the vertical direction of the exhaust pipe, and in the vicinity of a flange for connecting the exhaust pipe. Is characterized in that an exhaust pipe bulge or a member separate from the exhaust pipe (for example, a fastener) is provided to direct the exhaust flow upward in the vertical direction.

  At present, such flanges (particularly those having protuberances) are often used in exhaust pipe connection portions. According to each of the sensor heating control devices, even when such a flange is used, sensor heating control can be more suitably performed.

  According to a thirteenth aspect of the present invention, in the apparatus according to any one of the ninth to twelfth aspects, the exhaust system sensor purifies the exhaust gas discharged from the engine in the exhaust passage of the internal combustion engine. The exhaust gas purifying device is provided on the upstream side of the exhaust gas.

  If the exhaust system sensor is on the downstream side of the exhaust gas purification device, moisture or the like in the exhaust gas is removed through the device, so that the sensor is difficult to get wet. However, in general, a sensor or the like for feedback control of the air-fuel ratio is often provided on the upstream side of the exhaust purification device for the convenience of the control (for example, due to consideration of detection accuracy, responsiveness, etc.). According to the device of the thirteenth aspect, even when the exhaust system sensor is in such an installation environment, the occurrence of cracks and the like due to the sensor heating in the above-described wet state is more preferably prevented (or Suppression).

  By the way, a sensor that is activated in a temperature region higher than normal temperature and exhibits high detection capability is often used as a sensor that detects a gas component (particularly gas concentration) in exhaust gas. In particular, the demand for the above-described oxygen concentration sensor is large in an automobile engine (on-vehicle internal combustion engine). Therefore, as in the invention described in claim 14, in the device according to any one of claims 6 to 13, the target sensor detects an oxygen concentration and outputs the detection result. The practicality of this configuration is particularly high.

  The inventor invented the device according to claim 15 as a device useful for realizing the device according to claim 9 and the like. That is, in the invention according to claim 15, the condensate detection device for an internal combustion engine is applied to an internal combustion engine having a sensor in the exhaust passage, and the depression (recessed portion) of the exhaust passage formed near the exhaust upstream side of the sensor. ) Is provided with means for detecting the amount of condensed water accumulated in the inside. According to such an apparatus, it becomes possible to easily and accurately detect the amount of condensed water (particularly, the amount of condensed exhaust water) accumulated in the depression (concave portion).

  Hereinafter, with reference to FIGS. 1 to 14, an embodiment embodying a condensed water amount detection device and a sensor heating control device for an internal combustion engine according to the present invention will be described. It is assumed that the engine control system in which each device of the present embodiment is mounted is one that executes the above-described air-fuel ratio feedback control based on the output of an oxygen concentration sensor provided in the exhaust passage of the engine. .

  First, the schematic configuration and operation of the engine control system of the present embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram showing an outline of the system, and signal lines in the figure correspond to a wiring layout. As an engine to be controlled by this system (engine 10 in the figure), a multi-cylinder (for example, in-line 4-cylinder) engine for a four-wheeled vehicle is assumed. However, in FIG. 1, only one cylinder (cylinder 20 in the figure) is shown for convenience of explanation. As shown in FIG. 1, the engine 10 is a 4-stroke reciprocating intake port injection engine (internal combustion engine). That is, in this engine 10, a cylinder discrimination sensor (electromagnetic pickup) provided on the camshafts (not shown) of the intake and exhaust valves 21 and 22 is sequentially discriminated, and for example, the cylinder 20 in the figure is replaced with a cylinder #. For each of the four cylinders # 1 to # 4, one combustion cycle by four strokes of intake, compression, combustion, and exhaust is a “720 ° CA” period, specifically, for example, “180 ° CA” is shifted between the cylinders. The cylinders # 1, # 3, # 4, and # 2 are sequentially executed. Since the configuration of these four cylinders # 1 to # 4 is basically the same, here, the system will be described with a focus on one cylinder 20.

  As shown in FIG. 1, this engine control system is an engine that rotates a crankshaft 10d (the illustrated portion is a pulsar gear attached to the crankshaft) that is an output shaft by torque generated through combustion in a cylinder 20. 10 (internal combustion engine) is set as a control object, and various sensors for controlling the engine 10 and an ECU (electronic control unit) 50 are constructed.

  The engine 10 to be controlled here is a spark ignition type reciprocating engine, and basically includes a cylinder 20 formed by a cylinder block 10a. The cylinder block 10a is provided with a cooling water passage (water jacket) 10b for circulating the cooling water through the engine 10, and a water temperature sensor 10c for detecting the temperature of the cooling water (cooling water temperature) in the water passage 10b. The engine 10 is cooled by the cooling water. In addition, a piston 20a is accommodated in the cylinder 20, and a crankshaft 10d that is an output shaft of the engine 10 (an output shaft common to the four cylinders) is rotated in conjunction with the reciprocating motion of the piston 20a. It has become. A crank angle sensor 10e (for example, an electromagnetic pickup) that outputs a crank angle signal at every predetermined crank angle (for example, at a cycle of 30 ° CA) is disposed on the outer peripheral side of the crankshaft 10d. The rotational angle position of the output shaft) and the rotational speed (engine rotational speed) can be detected.

  A cylinder head is fixed to the upper end surface of the cylinder block 10a, and a combustion chamber 20b is formed between the cylinder head and the crown surface of the piston 20a. The cylinder head is formed with an intake port (intake port) and an exhaust port (exhaust port) that open to the combustion chamber 20b. The intake port and the exhaust port each have a cam (not shown) (specifically, a crankshaft). The intake valve 21 and the exhaust valve 22 are driven to open and close by a cam attached to a cam shaft interlocked with 10d. Further, an intake pipe 30 (including an intake manifold) for sucking outside air (fresh air) into each cylinder of the engine 10 is connected to the intake port, and combustion gas from each cylinder of the engine 10 is connected to the exhaust port. An exhaust pipe 40 (including an exhaust manifold) for discharging (exhaust) is connected.

  In the intake pipe 30 (intake passage) constituting the intake system of the engine 10, in order to detect the amount of fresh air drawn through the air cleaner 31 at the most upstream part of the intake pipe 30, a hot wire (hot wire) type air flow meter 32 is used. (Air flow measurement sensor) is provided. Further, on the downstream side of the air flow meter 32, an electronically controlled throttle valve 33 (intake throttle valve) whose opening degree is electronically adjusted by an actuator such as a DC motor, and an opening degree of the throttle valve 33 (throttle valve). And a throttle opening sensor 33a for detecting movement (opening fluctuation) and movement (opening fluctuation). Further, on the downstream side of the throttle valve 33, there is provided a surge tank 30a in which the passage area of the intake pipe 30 is expanded (expanded diameter) for the purpose of preventing intake pulsation and intake interference, and the surge tank 30a has intake air. An intake pipe pressure sensor 30b for detecting the pipe pressure is provided.

  The intake pipe 30 is branched so as to introduce air into each cylinder of the engine 10 on the downstream side of the surge tank 30a. An electromagnetically driven (or piezoelectrically driven) injector 35 (fuel injection valve) that injects fuel near the intake port of each cylinder is attached to the branch passage of the intake pipe 30 for each cylinder. ing. In the engine 10, fuel (gasoline) is injected and supplied (port injection) to the intake passage, particularly to the intake port of each cylinder, by the injectors provided for each cylinder. Then, by igniting the fuel injected by the injector 35 (strictly, the mixture with intake air), the fuel is combusted in the combustion chamber 20b. For this purpose, a spark plug 15 having an ignition device 15a made of an ignition coil or the like is attached to the cylinder head of each cylinder of the engine 10. That is, when the engine 10 is ignited, the ECU 50 applies a high voltage to the spark plug 15 at a desired ignition timing. Then, by applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 15, and this generated spark discharge ignites the air-fuel mixture introduced into the combustion chamber 20 b, thereby The fuel burns based on the reaction.

  On the other hand, an exhaust pipe 40 (exhaust passage) that constitutes an exhaust system of the engine 10 is configured by connecting pipes 40a to 40c via flanges. An exhaust temperature sensor 41a for detecting and an exhaust pipe inner wall temperature sensor 41b for detecting the inner wall temperature of the exhaust pipe 40 are sequentially provided. Further, a predetermined exhaust purification device is provided as an exhaust aftertreatment system for exhaust purification on the exhaust downstream side. For example, a catalyst 41 made of a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust is provided between the pipe 40b and the pipe 40c, and the exhaust is sent to the upstream side and the downstream side of the catalyst 41, respectively. As targets, oxygen concentration sensors 42a and 42b for detecting the air-fuel ratio of the air-fuel mixture are provided. In the present embodiment, as the oxygen concentration sensor 42a, an oxygen concentration sensor that outputs a linear electrical signal corresponding to the oxygen concentration (and hence the air-fuel ratio) in exhaust gas, a so-called linear detection type A / F sensor is used. And On the other hand, as the oxygen concentration sensor 42b, an oxygen concentration sensor that changes the output value in a binary manner depending on whether the oxygen concentration in the exhaust gas is on a predetermined reference value (for example, the theoretical air-fuel ratio) or not. A so-called binary detection type O2 sensor is used. FIG. 2 shows (a) an overview structure and (b) an internal structure of a so-called laminated type A / F sensor with a heater as an example of the oxygen concentration sensor 42a. 2A is a side view showing the general shape of the sensor, and FIG. 2B is a sectional view showing the internal structure of the sensor.

  As shown in FIG. 2, this sensor is roughly composed of a laminate of a sensor element 421 made of a solid electrolyte such as zirconia (ZrO 2) and a heater 422 (heat generating device) for heating the sensor element 421. The tip portion corresponding to the sensing portion (gas detection portion) is configured to be covered twice by the outer cover 427 and the inner cover 428. Here, the sensor element 421 is formed on a substrate made of alumina (Al 2 O 3), for example, together with a gas shielding layer, a diffusion resistance layer, and the like, and a predetermined voltage is applied to a sensing unit sandwiched between a pair of electrodes. Further, the heater 422 is driven (energized) to be in a drive state (energized state), and generates heat as the drive amount (energization amount) increases by generating heat in the drive state. In order to directly and uniformly heat the sensing portion of the sensor element 421, the sensor element 421 is formed so as to be embedded in a predetermined portion (if necessary, divided into a plurality of portions). The outer cover 427 and the inner cover 428 covering these laminates are provided with ventilation holes on the side surfaces (holes 427a and 428a) and bottom surfaces (holes 427b and 428b) for taking in exhaust air to be sensed. The oxygen concentration in the exhaust gas taken into the inner cover 428 (sensing unit) through these ventilation holes is detected by the sensor element 421. In this sensor, the outer cover 427 and the inner cover 428 form a maze structure of a vent hole, and the water resistance of the sensor (oxygen concentration sensor 42a) is enhanced by the maze structure of the vent hole.

  This sensor having the above-described structure is used in a state in which at least the sensing portion of the sensor element 421 is heated (temperature controlled) to a predetermined operating temperature range (for example, near “700 ° C.”) higher than normal temperature by the heater 422. . At this time, what controls the drive amount of the heater 422 (specifically, controls the energization amount corresponding to the drive energy) is the sensor heating control device of the present embodiment mounted on the ECU 50. The operating temperature range of the oxygen concentration sensor 42a is set, for example, as a temperature range that is equal to or higher than the temperature at which the sensor element 421 is activated and does not damage the sensor element 421.

  In the system of this embodiment, the oxygen concentration in the exhaust gas is detected by the oxygen concentration sensors 42a and 42b. During steady operation of the engine 10, the air-fuel ratio in the exhaust (= weight of air / weight of fuel) is detected based on the sensor outputs of the oxygen concentration sensors 42a and 42b, and the air-fuel ratio (particularly the catalyst) is detected. The air-fuel ratio upstream of the exhaust gas 41 is feedback-controlled to the stoichiometric air-fuel ratio (≈ “14.8”) in which the catalyst 41 composed of the above three-way catalyst exhibits high purification performance.

  In addition to the sensors described above, a vehicle (not shown) is provided with a number of sensors for use in various controls performed on the vehicle. For example, an accelerator sensor 50a that outputs an electric signal corresponding to the state (displacement amount) of the pedal is provided in the accelerator pedal (driving operation portion) to detect the amount of operation (depression amount) of the accelerator pedal by the driver. It has been.

  In such a system, the ECU 50 is a part that functions as a condensed water amount detection device and a sensor heating control device of the present embodiment, and performs engine control mainly as an electronic control unit. The ECU 50 (engine control ECU) includes a well-known microcomputer (not shown), grasps the operating state of the engine 10 and user requests based on the detection signals of the various sensors, and according to the above, By operating various actuators such as the throttle valve 33 and the injector 35, various controls related to the engine 10 are performed in an optimum manner according to the situation at that time. For example, during steady operation of the engine 10, various combustion conditions (for example, ignition timing, fuel injection amount, intake air amount, and air-fuel ratio, etc.) are calculated based on the detection signals of the sensors, and various actuators are operated. As a result, the indicated torque (generated torque) generated through fuel combustion in each cylinder (combustion chamber), and thus the shaft torque (output torque) actually output to the output shaft (crankshaft 10d) is controlled. . Further, while comparing the sensor outputs of the oxygen concentration sensors 42a and 42b with their target values, for example, the injection time of the injector 35 for supplying fuel and air for combustion in each cylinder and the opening of the throttle valve 33. By variably controlling the degree or the like, so-called air-fuel ratio feedback control is performed in which the air-fuel ratio in the exhaust gas around the catalyst 41 is brought close to (preferably matched) the stoichiometric air-fuel ratio. Basically, when the air / fuel ratio is lean (> theoretical air / fuel ratio), the fuel injection amount is controlled to increase, while when the air / fuel ratio is rich (<theoretical air / fuel ratio), the fuel injection amount is controlled to decrease, The air-fuel ratio is maintained within a predetermined range near the stoichiometric air-fuel ratio.

  The microcomputer mounted on the ECU 50 basically includes a CPU (basic processing device) for performing various calculations, and a RAM (main memory for temporarily storing data and calculation results during the calculation) ( Random Access Memory (ROM), ROM as a program memory (read-only storage device), EEPROM (electrically rewritable non-volatile memory) as data storage memory, and backup RAM (on-vehicle battery etc. even after main power supply of ECU is stopped) Memory that is constantly powered by a backup power supply), signal processing devices such as A / D converters and clock generation circuits, various arithmetic devices such as input / output ports for inputting / outputting signals to / from the outside, A storage device, a signal processing device, a communication device, a power supply circuit, and the like are included. The ROM stores various programs related to engine control including a program related to the sensor heating control (drive amount control of the heater 422), a control map, and the like, and a data storage memory (for example, EEPROM) stores an engine. Various control data including 10 design data are stored in advance.

  The configuration of the engine control system according to the present embodiment has been described in detail above. That is, in a vehicle (for example, a passenger car or a truck) on which the above system is mounted, the driving environment is optimized through various controls by such a system. As described above, the sensor heating control device of the present embodiment mounted on the ECU 50 controls the drive amount of the heater 422 (FIG. 2) of the oxygen concentration sensor 42a in the system. FIG. 3 shows a part (circuit) relating to the sensor heating control of the ECU 50 as a function-specific circuit diagram.

  As shown in FIG. 3, one terminal of the sensor element 421 is connected to a constant voltage source 423. The other terminal is connected in parallel to the sensor control circuit 501 and the resistor 424 in the ECU 50, and among the resistor 424, the resistor 424 is connected by a wiring (shield wire) having the resistor 424. Is grounded. With this circuit configuration, the sensor element 421 is controlled to the above-described operating temperature range (active state) in a state where a constant voltage is applied by the constant voltage source 423. In the active state, the amount of current generated by the application of the constant voltage is changed according to the surrounding oxygen concentration (that is, the oxygen concentration in the exhaust gas) (for example, the current amount is linearly changed with respect to the oxygen concentration). The current value is output as sensor output to the ECU 50 (specifically, the sensor control circuit 501). Specifically, when a voltage is applied from the ECU 50 (sensor control circuit 501) to the sensor element 421 (solid electrolyte) heated by the heater 422, in the case of an air-fuel ratio lean, an ion current corresponding to the oxygen concentration in the exhaust gas is When the air-fuel ratio is rich, ion currents corresponding to the unburned gas concentration in the exhaust gas are generated. For this reason, a diffusion resistance layer (not shown) provided on the exhaust side of the sensor element 421 provides a current value corresponding to the oxygen concentration or unburned gas concentration in the exhaust as a sensor output.

  On the other hand, the sensor control circuit 501 operates in response to a command from the microcomputer in the ECU 50, applies an alternating voltage of a predetermined frequency to the sensor element 421, and outputs the sensor output (element current signal) and the sensor element. An electric signal (element voltage signal) or the like corresponding to the magnitude of the alternating voltage flowing through 421 is passed to the microcomputer. The microcomputer calculates the air-fuel ratio in the exhaust based on the element current signal, and calculates the impedance (element impedance) of the sensor element 421 based on the element voltage signal. Incidentally, the calculated value of the air-fuel ratio obtained here is used, for example, in the above-described air-fuel ratio feedback control. That is, the air-fuel ratio feedback control described above is performed so that the calculated value of the air-fuel ratio becomes the stoichiometric air-fuel ratio. On the other hand, the calculated value of the element impedance is used to detect the temperature (element temperature) of the sensor element 421. Specifically, the sensor element 421 has a characteristic that the element impedance decreases as the element temperature increases. The microcomputer uses such characteristics to detect the element temperature based on the calculated value of the element impedance.

  The heater 422 for heating the sensor element 421 has one terminal grounded and the other terminal connected to an energization control circuit 503 in the ECU 50. The energization control circuit 503 operates in response to an instruction from the microcomputer in the ECU 50, and controls the energization amount of the heater 422 by PWM (Pulse Width Modulation) control using the in-vehicle battery 504 as a power source. Thus, the heater 422 is supplied with a drive current having a duty ratio corresponding to the target value each time. In the ECU 50, a heater current detection circuit 502 is provided in a current supply path (wiring) from the energization control circuit 503 to the heater 422, so that the energization amount of the heater 422 can be detected. Then, the energization amount of the heater 422 detected by the circuit 502 is sequentially set to a target value corresponding to the target element temperature so that the temperature of the sensor element 421 sometimes becomes a desired value (a target value for each time). Control (PID control). Thus, the temperature of the sensor element 421 is controlled within a predetermined operating temperature range.

  By the way, also in the apparatus of the present embodiment, when the sensor is activated, the driving amount of the heater 422 attached to the oxygen concentration sensor 42a is activated according to the state around the sensor, as in the apparatus described in Patent Document 1. The control mode related to is variably set. However, in the apparatus of the present embodiment, when the engine 10 is stopped before the engine 10 is started and a sufficient operation time is reached, the amount of condensed water generated in the exhaust pipe 40 by the operation is detected. ing. Specifically, the amount of condensed water accumulated in a depression (concave portion) of the exhaust pipe 40 formed near the exhaust upstream side of the oxygen concentration sensor 42a is detected. Here, this point will be described in more detail with reference to FIGS. FIG. 4 is an enlarged schematic view showing the inside of the exhaust pipe 40 in the vicinity of the upstream side of the exhaust gas of the oxygen concentration sensor 42a. The arrow in the figure indicates the direction of gravity, that is, the lower side in the vertical direction. On the other hand, FIG. 5 is a schematic view when the inside of the pipe 40b is viewed from the exhaust upstream side.

  As shown in FIG. 4, the oxygen concentration sensor 42a to be heated is attached to the upper side in the vertical direction of the exhaust pipe 40 (pipe ceiling surface). In the vicinity of the exhaust gas upstream side of the oxygen concentration sensor 42a, a flange portion 400 corresponding to the connecting portion of both pipes is formed by the flange 400a of the pipe 40a and the flange 400b of the pipe 40b. The exhaust pipe inner wall temperature sensor 41b (FIG. 1) is provided near the exhaust upstream side (specifically, the bottom surface of the pipe) of the flange portion 400. Here, a depression (concave portion) 401 (a groove extending in the circumferential direction of the pipe) of the exhaust pipe 40 is formed on the lower side in the vertical direction in the vicinity of the flange portion 400. More specifically, as shown in FIG. 5, in the vicinity of the exhaust downstream side of the recess 401, that is, in the vicinity of the exhaust upstream side of the oxygen concentration sensor 42 a, a bulge protruding from the inside, that is, a protrusion (protrusion of the pipe 40 b). (Convex portion extending in the circumferential direction) 402 is formed.

  In the vicinity of the exhaust gas upstream side of the oxygen concentration sensor 42a, the structure inside the exhaust pipe 40 is such a structure. Therefore, the condensed water generated by starting the engine 10 tends to accumulate in the recess 401 of the flange portion 400 according to gravity. Moreover, the protrusion 402 is located in the vicinity of the upstream side of the oxygen concentration sensor 42a, and functions to direct the exhaust flow upward in the vertical direction, that is, toward the sensor 42a. For this reason, in the system according to the present embodiment, when the engine 10 is started, the condensed water accumulated in the depression 401 is scattered on the exhaust flow in the form of droplets and adheres to the oxygen concentration sensor 42a. As a result, the sensor 42a is easily wetted.

  Therefore, in the present embodiment, when the engine 10 is stopped, the amount of condensed water accumulated in the recess 401 of the flange portion 400 is detected and stored in a nonvolatile manner, and the engine 10 is started next time. Indicates the amount of condensed water based on the detected value (corresponding to the amount of residual condensed water already remaining at that time) and the amount of new condensed water newly generated by this start-up, the driving amount of the heater 422 (energization) The control mode related to (amount) is variably set. Hereinafter, the sensor heating control will be described with reference to FIGS.

  First, a process related to the sensor heating control will be described with reference to FIG. FIG. 6 is a flowchart showing the processing procedure of the sensor heating control. The series of processing shown in FIG. 6 is basically performed by executing a program stored in the ROM by the ECU 50. Sequentially executed at processing intervals (for example, at predetermined crank angles or at predetermined time intervals). The values of various parameters used in this process are stored as needed in a storage device such as a RAM, EEPROM, or backup RAM mounted on the ECU 50, and updated as necessary.

  As shown in FIG. 6, in this series of processes, first, in step S11, the temperature (element temperature T) of the sensor element 421 at that time is detected (calculated) from the element impedance described above. Next, in step S12, it is determined whether or not “1 (permitted)” is set in the heater energization permission flag F1 that indicates whether or not the heater 422 is permitted to be driven.

  When it is determined in this step S12 that the heater energization permission flag F1 is set to “1”, as the normal control, in the subsequent step S13, the cooling water temperature THW at that time (for example, an actual value measured by the water temperature sensor 10c). ) Is acquired, and in step S14, the temperature Td is set with respect to the target element temperature Tt. Note that the temperature Td is acquired by using a predetermined table (for example, stored in a ROM or the like, which may be a mathematical expression) in which an appropriate value (optimum value) of the temperature Td is written for each cooling water temperature THW in advance by experiments or the like.

  In the following step S15, the energization amount of the heater 422 is set as the duty ratio HD in the PWM control based on the element temperature T detected in the step S11 and the target element temperature Tt set in the step S14. Specifically, according to a well-known control expression related to the PID operation, the control amount P term (proportional term) is “HDp = Kp × (Tt−T)”, and the control amount I term (integral term) is “HDi = Ki ×. ∫ (Tt−T) ”, the control amount D term (differential term) is calculated as“ HDd = Kd × (T (current value) −T (previous value)) ”, and the duty ratio HD is“ HD = HDp + HDi + HDd ”. Is calculated as follows.

  Thus, when it is determined in step S12 that the heater energization permission flag F1 is set to “1”, normal control is executed. That is, the duty ratio HD corresponding to the energization amount of the heater 422 is set to a value that activates the oxygen concentration sensor 42a quickly and accurately (for example, without overshoot).

  On the other hand, if it is determined in step S12 that the heater energization permission flag F1 is not set to “1” (“0” is set), the heater energization amount is de-energized (step S16). Duty ratio HD = “0%”). As a result, the driving of the heater 422 is prohibited.

  In the present embodiment, by repeating the series of processes shown in FIG. 6, the heating of the oxygen concentration sensor 42a is controlled until the predetermined condition is satisfied (as a result, the heating of the sensor 42a). ) Is inhibited, so that deterioration or breakage of the sensor 42a due to water is suppressed. That is, the heater energization permission flag F1 used in step S12 of FIG. 6 is set to “0” as an initial value when the engine 10 is started. After that, until the heater energization permission flag F1 is set to “1”, the driving of the sensor heating heater 422 is prohibited.

  Next, the heater energization permission determination, that is, the heater energization permission flag F1 setting process will be described with reference to FIG. FIG. 7 is a flowchart showing the procedure of the determination process, and the process of FIG. 7 is started when the engine 10 is started. Specifically, the engine 10 is started based on an on / off operation of an ignition switch. The ignition switch serves as an ignition switch and a start switch, and is turned on / off by a driver's key operation. In other words, when the driver inserts the ignition key into the key cylinder and turns it, the steering lock is released at the first stage, accessories such as radios at the second stage, current flows to the ignition device at the third stage, and the other stage When turned, the starter motor (not shown) rotates (cranks) the crankshaft 10d (the output shaft of the engine 10) and starts the engine 10. The process of FIG. 7 is started with the cranking by the starter motor as a trigger, and thereafter, the program stored in the ROM is executed by the ECU 50, whereby a predetermined processing interval (for example, every predetermined crank angle or for a predetermined time). (Sequentially etc.) The values of various parameters used in this processing are also stored as needed in a storage device such as a RAM, EEPROM, or backup RAM mounted on the ECU 50, and updated as necessary.

  As shown in FIG. 7, in this determination process, first, in step S21, it is determined whether or not “0” is set in the heater energization permission flag F1, and in this step S21, “0” is set in the flag F1. Only when it is determined that the setting has been made, the processing from step S22 is executed. As described above, when the engine 10 is started, the heater energization permission flag F1 is set to “0” as an initial value. Therefore, at least at the beginning of the process of FIG. 7, the processes after step S22 are executed.

  In step S22, it is determined whether or not the setting of the total delay time DTc, which is a period during which the heater 422 is normally driven (steps S13 to S15 in FIG. 6), is prohibited. Initially, since the total delay time DTc is not set, it is determined in step S22 that the setting of the total delay time DTc is not completed, and the processing of the subsequent step S23 is executed. On the other hand, after the total delay time DTc is set by the process of step S23, the process proceeds to the subsequent step S24 without performing the process of step S23 (skipping). FIG. 8 is a flowchart showing details of the total delay time DTc setting process performed as the process of step S23.

  As shown in FIG. 8, when setting the delay time, first, in step S31, based on the output of the water temperature sensor 10c, for example, the coolant temperature (starting coolant temperature) THW0 at that time is detected (actually measured). Next, in step S32, a delay time DTa is calculated based on the starting coolant temperature THW0 detected in step S31. Specifically, it is acquired using, for example, a predetermined map (which may be a mathematical expression) stored in a ROM or the like in the ECU 50. In this map, an appropriate value (optimum value) is written in advance by experiments or the like, and as indicated by the solid line L11 in the graph of FIG. 9, the lower the starting coolant temperature THW0, the more the delay time DTa. On the other hand, a larger value is set.

  In the subsequent step S33, the residual condensed water amount Qw2 is read from the backup RAM in the ECU 50. The residual condensed water amount Qw2 is detected when the engine 10 is stopped and stored in the backup RAM (or an EEPROM or the like) (details will be described later). The value corresponds to the amount of condensed water accumulated in the aforementioned depression 401 (FIG. 4) at this time.

  In the subsequent step S34, the delay time DTb is calculated based on the starting cooling water temperature THW0 acquired in step S31 and the residual condensed water amount Qw2 read in step S33. Specifically, this value is also acquired by using a predetermined map (which may be a mathematical expression) stored in a ROM or the like in the ECU 50, for example. This map is also obtained by preliminarily writing an appropriate value (optimum value) by experiments or the like, as indicated by a solid line L12a (Qw2: large) and a one-dot chain line L12b (Qw2: small) in the graph of FIG. A larger value is set for the delay time DTb as the starting coolant temperature THW0 is lower and the residual condensed water amount Qw2 is larger.

  Based on the delay time DTa calculated in step S32 and the delay time DTb calculated in step S34, the total delay time DTc is set in the subsequent step S35. Specifically, the total delay time DTc is set as the sum of the delay time DTa and the delay time DTb (DTc = DTa + DTb).

  In step S23 of FIG. 7, the total delay time DTc is set through such processing. In the subsequent step S24, the elapsed time after engine start (elapsed time after start) is equal to or greater than the total delay time DTc compared to the total delay time DTc set in step S23 (elapsed time after start ≧ DTc). If it is determined in this step S24 that the elapsed time after the start (for example, the time counting by sequentially counting from the engine start) is not equal to or greater than the total delay time DTc (less than the total delay time DTc). The heater energization permission flag F1 remains “0”, the series of processes in FIG. 7 is terminated, and the determination process in step S24 is repeated. On the other hand, if it is determined in step S24 that the elapsed time after start has become equal to or greater than the total delay time DTc, the heater energization permission flag F1 is set to “1” in subsequent step S25. After “1” is set in the flag F1 in step S25, it is determined that “1” is set in the flag F1 in the previous step S21, and the processing after step S22 is performed. Disappear.

  FIG. 11 is a flowchart showing a processing procedure of processing related to detection and update of the residual condensed water amount Qw2 used in step S33 of FIG. The process of FIG. 11 is started when the engine 10 is stopped. Specifically, when the driver turns the ignition key to the off position and waits for a while, the engine 10 stops. The process of FIG. 11 is executed whenever the engine is stopped. The engine stop can be detected based on, for example, the position of the ignition key or the engine speed. That is, for example, a predetermined time (for example, “3 seconds”) has passed since the ignition key is turned to the off position, and the engine speed is “0” (for example, based on the output of the crank angle sensor 10e). When both conditions (detection) are satisfied at the same time, it is determined that the engine 10 has stopped.

  As shown in FIG. 11, when the residual condensed water amount Qw2 is updated, it is first determined in step S41 whether the heater energization permission flag F1 is set to “0”. If it is determined in this step S41 that the flag F1 is set to “0”, the engine 10 is stopped before the engine 10 is started and a sufficient operation time is reached (see the previous figure). In step S24 in FIG. 7, it is not determined that the elapsed time after start has become equal to or greater than the total delay time DTc). In subsequent step S42, the start-time coolant temperature THW0 acquired in step S31 in FIG. A new condensed water amount Qw1 is calculated (estimated) based on the engine operation time from the engine start to the stop for. Specifically, this value is also acquired by using a predetermined map (which may be a mathematical expression) stored in a ROM or the like in the ECU 50, for example. This map is also obtained by preliminarily writing an appropriate value (estimated value) by an experiment or the like, as indicated by a solid line L13a (THW0: low temperature) and an alternate long and short dash line L13b (THW0: high temperature) in the graph of FIG. Until the engine operation time from the engine start to the stop reaches a certain time, it is estimated that a larger amount of new condensed water Qw1 is generated as the operation time becomes longer. On the other hand, since the degree of vaporization increases when the engine operation time exceeds a certain time, it is estimated that a smaller amount of new condensed water Qw1 is generated as the operation time becomes longer. In any case, it is estimated that the new condensate amount Qw1 is generated as the starting coolant temperature THW0 is lower. As described above, the value of this new condensed water amount Qw1 corresponds to the amount of condensed water accumulated in the aforementioned depression 401 (FIG. 4).

  Then, in the subsequent step S43, the residual condensed water amount in the backup RAM is added by adding the new condensed water amount Qw1 calculated in step S42 to the residual condensed water amount Qw2 stored in the backup RAM in the ECU 50 at that time. Qw2 is updated (Qw2 = Qw1 + Qw2).

  On the other hand, when it is determined in step S41 that the flag F1 is set to “0”, the engine 10 is started and the engine 10 is stopped after a sufficient operation time has been reached (see the previous figure). 7, it is determined that the elapsed time after start has become equal to or greater than the total delay time DTc), and in subsequent step S44, the residual condensed water amount Qw2 stored in the backup RAM in the ECU 50 is reset (Qw2 = 0).

  In the present embodiment, the value of the heater energization permission flag F1 is set through the processes of FIGS. 7, 8, and 11. That is, as described above, the total delay time DTc, and hence the heater drive prohibition time (the time until the heater energization permission flag F1 is set to “1”) is variably set according to the residual condensed water amount Qw2. It is. By doing so, the above-described deterioration or breakage of the sensor 42a due to water is accurately avoided (or suppressed) in a shorter heater drive inhibition time.

  Next, referring to FIG. 13 and FIG. 14, one aspect of sensor heating control by the ECU 50 (sensor heating control device of the present embodiment) will be briefly described. Here, FIG. 13 shows an operation mode when the engine 10 is operated for a sufficiently long period with the residual condensed water amount Qw2 reset (Qw2 = 0), and the engine 10 is stopped immediately after starting. FIG. 14 shows an operation mode in a case where a sufficiently long period of operation is performed after such a short-term operation is performed, and a description will be given while comparing the two. In FIGS. 13 and 14, (a) to (g) are (a) elapsed time after start, (b) engine rotation speed, (c) intake air amount (actually measured value by air flow meter 32), (D) Exhaust temperature (measured value by exhaust temperature sensor 41a), (e) exhaust pipe flange inner wall temperature (for example, measured value by exhaust pipe inner wall temperature sensor 41b), (f) the amount of condensed water at that time (of flange 400) (G) Condensed water amount accumulated in the depression 401), (g) Transition of each parameter related to the sensor heating control, such as the heater energization permission flag F1 (set through the processing of FIG. 7, the initial value at engine start is “0”) It is a timing chart which shows.

  First, in the example shown in FIG. 13, when the engine 10 is started at the timing t11, the exhaust pipe flange inner wall temperature (which can be estimated as the starting coolant temperature THW0) is not sufficiently high in the initial stage (FIG. 13 (e)). Therefore, condensed water is generated by the operation, and the amount of condensed water in the flange portion 400 increases (FIG. 13 (f)). And then, for example, at timing t12, when the exhaust pipe flange inner wall temperature becomes sufficiently high, vaporization of condensed water in the flange portion 400 is promoted more than the generation of condensed water, and the amount of condensed water in the depression 401 decreases. Begin to. In the present embodiment, the time required for the amount of condensed water in the depression 401 generated by the start operation to be sufficiently small (for example, less than a predetermined amount) based on the start-time coolant temperature THW0 in step S32 of FIG. (Heater drive inhibition time) is calculated and set as the total delay time DTc (= DTa). That is, until this time (corresponding to periods t11 to t13 in FIG. 13) elapses, the driving of the heater 422 is prohibited (heater energization permission flag F1 = 0). In other words, the driving of the heater 422 is permitted at the timing t13 (heater energization permission flag F1 = 1). Thus, in a state where the amount of condensed water is large, that is, in a situation where the oxygen concentration sensor 42a is assumed to be wet, the heater 422 is not driven, and the state where the amount of condensed water is small, that is, the sensor 42a is not wet. Only in an assumed situation, the heater 422 can be driven, and as a result, the sensor 42a can be activated while suppressing the above-described deterioration and breakage due to moisture.

  On the other hand, in the example shown in FIG. 14, the engine 10 is started at the timing t21 and immediately stopped at the timing t22. For this reason, the condensed water produced | generated by the starting operation remains in the hollow 401 of the flange part 400 as residual condensed water, without being vaporized. The residual condensed water basically remains until the next start. Accordingly, at the subsequent timing t23, the engine 10 is started with the residual condensed water remaining. In this case as well, thereafter, similarly to the example of FIG. 13, the amount of condensed water in the depression 401 starts to decrease at timing t24, and the driving of the heater 422 is permitted at timing t25 (heater energization permission flag F1 = 1). ). However, in this case, not only the new condensed water amount generated by the start-up operation but also the residual condensed water amount already remaining when the engine 10 is started, the heater drive inhibition time (period t23 in FIG. (corresponding to t25) is set. In other words, in this case, the heater drive inhibition time becomes longer by the amount of residual condensed water than in the case of FIG.

  Specifically, in this example, the process of FIG. 11 is executed at timing t22 when the engine 10 is stopped. In step S43 of FIG. 11, the residual condensed water amount Qw2 is updated in such a manner that the condensed water generated by the start operation is added to the value of the residual condensed water amount Qw2 at that time. This residual condensed water amount Qw2 is a parameter indicating how much residual condensed water remains in the depression 401 at the next start-up, that is, at the timing t23, and is mainly a calculation of the delay time DTb in the processing of FIG. Used for. This delay time DTb corresponds to the time until the amount of residual condensed water evaporates and disappears. Therefore, in the example of FIG. 14, the heater drive inhibition time (total delay time DTc) is longer by the delay time DTb than in the case of FIG. Specifically, at the next start (timing t23), total condensation which is the sum of the new condensed water amount (estimated from the starting cooling water temperature THW0) and the residual condensed water amount Qw2 by the processing of FIG. The time required for the amount of water to become sufficiently small (for example, less than a predetermined amount) (time until the residual condensed water in the depression 401 is removed by heating due to the operation of the engine 10 or the like) is calculated, and this is the total delay time DTc. (= DTa + DTb). The heater energization permission flag F1 is changed from “0 (prohibited)” to “1 (permitted)” at timing t25 based on the total delay time DTc. Thus, also in this example, the driving of the heater 422 is permitted when the amount of condensed water in the recess 401 (total amount of condensed water) is sufficiently small.

  Note that the heater energization permission flag F1 is basically set in the same manner as described above even when a short-term operation has already been performed before the timing t21. That is, in this case, the residual condensed water amount generated by the first short-term operation is stored in the residual condensed water amount Qw2 when the engine is stopped. Therefore, in this case, residual condensed water already exists in the depression 401 at the timing t21, and the value of the residual condensed water amount Qw2 at that time corresponds to that amount. Then, when the second short-term operation is performed at the subsequent timing t21, when the engine is stopped (timing t22), the amount of new condensed water generated by the second short-term operation is further increased with respect to the residual condensed water amount Qw2 at that time. Will be added. That is, when the residual condensed water amount Qw2 is updated in step S43 in FIG. 11, the residual condensed water amount by the second short-term operation is added to the residual condensed water amount by the first short-term operation. As a result, the residual condensed water amount Qw2 indicates the residual condensed water amount remaining at the timing t23. Accordingly, in this case as well, by setting the total delay time DTc in the same manner as described above, the driving of the heater 422 is permitted when the amount of condensed water in the recess 401 (total amount of condensed water) becomes sufficiently small.

  As described above, whenever the short-term operation is performed, the amount of condensed water generated by the operation is added (integrated) in step S43 of FIG. 11 and each time the engine 10 is operated for a long time, the above-described FIG. In step S44, the residual condensed water amount Qw2 is reset, so that the residual condensed water amount Qw2 indicates the residual condensed water amount at that time. In the present embodiment, the heater drive prohibition time (total delay time DTc) is variably set based on such residual condensed water amount Qw2, thereby suitably avoiding or suppressing inconveniences that may occur when the heater 422 is driven. Like to do.

  As described above, according to the condensed water amount detection device and sensor heating control device for an internal combustion engine according to this embodiment, the following excellent effects can be obtained.

  (1) As a device for detecting the amount of condensed water generated in the internal combustion engine (engine 10) (engine control ECU 50), when the engine 10 is stopped before the engine 10 is started and a sufficient operation time is reached (see FIG. 7 (determined by steps S24 and S25 of FIG. 7 and step S41 of FIG. 11), the amount of condensed water generated in the exhaust passage (exhaust pipe 40) of the engine 10 by the operation is detected, and a parameter indicating the amount of condensed water, and It was set as the structure provided with the program (Condensed water amount acquisition means, FIG. 11) which acquires the new condensed water amount Qw1 and the residual condensed water amount Qw2 (all are condensed water amount parameters) respectively equivalent to the parameter calculated | required using the same amount of condensed water. In such a configuration, the inconvenience (cracking of the sensor element 421) that may occur when the heating device (heater 422) attached to the oxygen concentration sensor 42a is driven by the condensed water amount parameter (new condensed water amount Qw1 and residual condensed water amount Qw2). Occurrence etc.) can be avoided or suppressed more suitably.

  (2) Condensed water amount parameters (new condensed water amount Qw1 and residual condensed water amount Qw2) are stored in a predetermined storage device (backup RAM in ECU 50) that can retain data even after engine 10 is stopped (new condensed water amount Qw1). Is configured to include a program (condensed water storage means, step S43 in FIG. 11) for converting to and storing the residual condensed water amount Qw2. This makes it possible to store the condensed water amount parameter more easily and in a usable state during the next operation.

  (3) A program for updating the condensate amount parameter (residual condensate amount Qw2) stored in the backup RAM in the ECU 50 based on the operation time until the engine 10 is stopped each time the engine 10 is started (update the condensate amount) Means, FIG. 11). By doing so, it is possible to maintain the condensed water amount parameter at a highly accurate value.

  (4) In the series of processes of FIG. 11, when the operation time until the engine 10 is stopped is sufficiently long (determined in step S41), the condensed water amount parameter (residual condensed water amount) stored in the backup RAM in the ECU 50. Qw2) is reset (step S44), and if the operation time until the engine 10 is stopped is not sufficiently long (determined in step S41), the condensed water amount parameter (residual condensed water amount Qw2) stored in the backup RAM. ) Is added with the condensate amount parameter acquired in step S42 this time (step S43). By doing so, the condensed water amount parameter (residual condensed water amount Qw2) can be obtained with high accuracy.

  (5) In step S42 of FIG. 11, based on the main body temperature of the engine 10 (detected as the engine coolant temperature THW0) and the operation time from start to stop of the engine 10, the amount of condensed water generated by the operation ( The amount of new condensed water Qw1) was estimated. This makes it possible to acquire (estimate) the condensed water amount parameter with high accuracy.

  (6) It is provided in the exhaust passage (exhaust pipe 40) of the engine 10 (internal combustion engine) in a state in which a heat generating device (heater 422) that increases the heat generation amount as the drive amount increases and the drive amount increases is provided. This is applied to a predetermined target sensor (oxygen concentration sensor 42a) that is activated in a temperature range (for example, near “700 ° C.”) and exhibits high detection capability, and controls the driving amount of the heater 422. As such a sensor heating control device (ECU 50 for engine control), when the engine 10 is started, according to the sum of the amount of residual condensed water already remaining and the amount of new condensed water newly generated by this start, It is configured to include a program (heating control means, steps S24 and S25 in FIG. 7, steps S34 and S35 in FIG. 8, and steps S12 to S16 in FIG. 2) for variably setting the control mode relating to the driving amount of the heater 422. By doing so, it becomes possible to more suitably perform the heating control of the target sensor (oxygen concentration sensor 42a).

  (7) At this time, based on the sum of the amount of residual condensed water and the amount of new condensed water, the length (total delay time DTc) of a period during which the driving is prohibited as a period preceding the normal driving of the heater 422 (delay period) Was variably set. Specifically, the total delay time DTc is set to a longer time as the sum of the residual condensed water amount and the new condensed water amount is larger. By doing so, it is possible to more suitably prevent (or suppress) the occurrence of cracks and the like due to the sensor heating in the above-described wet condition.

  (8) The amount of condensed water remaining in the depression (concave) formed in the vicinity of the exhaust gas upstream side of the oxygen concentration sensor 42a, the amount of residual condensed water used for calculation and setting of the total delay time DTc, and the details Is the amount of condensed water accumulated in the depression 401 (FIG. 4) formed in the vertical direction lower side of the exhaust passage (exhaust pipe 40) of the engine 10 when the engine 10 is in use (for example, mounted in a vehicle). . By doing so, sensor heating control can be performed more suitably.

  (9) A recess 401 is formed in the flanges 400a and 400b for connecting the exhaust pipe 40, and an oxygen concentration sensor 42a is attached to the upper side in the vertical direction of the exhaust pipe 40, and in the vicinity of the flanges 400a and 400b. The system (FIG. 4) provided with a ridge (projection 402) for directing the exhaust flow upward in the vertical direction was applied. According to the sensor heating control device (ECU 50) of the present embodiment, sensor heating control can be suitably performed even when such a flange is used.

  (10) A system in which the oxygen concentration sensor 42a is provided in the exhaust upstream side of the catalyst 41 (exhaust gas purification device) in the exhaust passage (exhaust pipe 40) of the engine 10 for purifying exhaust gas exhausted from the engine 10. (Fig. 1) was applied. According to the sensor heating control apparatus (ECU 50) of the present embodiment, even when the target sensor is in such an arrangement environment, the occurrence of cracks and the like due to the above-described sensor heating in the wet state is more suitably prevented ( Or suppression).

  (11) A sensor to be heated (activated) is an exhaust system sensor provided in an exhaust passage (exhaust pipe 40) through which exhaust is discharged after the combustion stroke of the engine 10, more specifically, from the engine 10 which is an internal combustion engine. The oxygen concentration sensor 42a detects the oxygen concentration in the exhaust gas discharged. According to the above configuration, whether the target sensor is an exhaust system sensor that is susceptible to water exposure, or particularly an oxygen concentration sensor that is sensitive to water exposure, preferably avoids damage or the like due to water exposure that may occur for the sensor. It becomes possible to suppress.

  The above embodiment may be modified as follows.

  In the above embodiment, the present invention can be basically applied in the same manner as described above even when the protrusion 402 is formed of a member (for example, a fastener) separate from the pipe and the flange. it can.

  In the above embodiment, the delay time DTa is calculated based on the starting coolant temperature THW0 in step S32 of FIG. Further, in step S42 of FIG. 11, a new condensed water amount Qw1 is calculated (estimated) based on the starting cooling water temperature THW0 and the engine operating time. However, the present invention is not limited to this, and a plurality of predetermined parameters indicating the engine body temperature at the time of starting the engine, such as the cooling water temperature of the engine 10, the lubricating oil temperature of the engine 10, the intake air temperature, the outside air temperature, and the exhaust pipe temperature (for example, the exhaust pipe inner wall) The delay time DTa and the new condensed water amount Qw1 may be calculated based on the lowest detection value among the actual measurement values by the temperature sensor 41b. With such a configuration, it is possible to more reliably prevent (or suppress) the occurrence of cracks and the like due to the sensor heating in the above-described wet condition.

  In the above embodiment, the driving of the heater 422 is prohibited in step S16 of FIG. However, the present invention is not limited to this. For example, without prohibition, in step S16, the driving amount of the heater 422 may be limited to a smaller amount than in the normal control (step S15). For example, the control target value of the heater drive amount is set to a smaller value than in the normal control, or the upper limit (upper limit guard value) of the heater drive amount settable range is set to a smaller value than in the normal control. Thus, the heater driving amount can be limited to a smaller amount than in the case of normal control.

  In the embodiment, the residual condensed water amount Qw2 is reset (step S44 in FIG. 11) when the engine is stopped. However, the present invention is not limited to this, and the reset process may be performed when it is found that the operation time is sufficiently long (for example, when a predetermined time has elapsed after the engine is started).

  -You may make it detect the amount of condensed water collected in the hollow 401 (FIG. 4) based on the output of the exhaust pipe inner wall temperature sensor 41b. Specifically, according to the experiment of the inventor and the like, the temperature of the exhaust pipe flange (for example, an actual measurement value by the exhaust pipe inner wall temperature sensor 41b) and the amount of condensed water generated per unit intake air amount are as shown in FIG. It becomes a relationship. Therefore, based on such a relationship (for example, using a predetermined map), the amount of condensed water is derived (detected) from the output of the exhaust pipe inner wall temperature sensor 41b, the output of the air flow meter 32, and the elapsed time after engine start. be able to. Expressing this in the formula, “Condensate generation amount (g) = Condensate generation amount per unit intake air amount (g / air 1 g) × Intake amount (g / sec) × Elapsed time after engine start (sec)” Become. In addition, such sensor output enables detection with higher accuracy.

  In the above embodiment, as the condensed water amount parameter, two types of parameters are obtained: a parameter indicating the condensed water amount (new condensed water amount Qw1) and a parameter obtained using the condensed water amount (residual condensed water amount Qw2). I did it. However, the present invention is not limited to this, and only one of them may be acquired. Further, these condensed water amount parameters (new condensed water amount Qw1 and residual condensed water amount Qw2) may be used only for data analysis by data accumulation, for example, without being used for sensor heating control.

  An apparatus for detecting the amount of condensed water in an internal combustion engine having a program for detecting the amount of condensed water accumulated in a depression 401 (FIG. 4) formed in the vicinity of the exhaust upstream side of the exhaust system sensor (oxygen concentration sensor 42a) is also effective. Further, the amount of condensed water detected by this apparatus may be used not only for sensor heating control but only for data analysis by data accumulation, for example.

  In the above embodiment, the remaining condensed water in the depression 401 is heated and removed by the operation of the engine 10 while the heater 422 is prohibited from driving (step S16 in FIG. 6). However, prior to starting the engine, for example, the cylinder 20 and intake / exhaust piping (intake pipe 30) are generated by heat (friction heat) generated by forcibly moving (rotating) the crankshaft 10d by an engine starter (starter device). Or the exhaust pipe 40) may be heated to remove (evaporate) the residual condensed water. Further, for example, by providing an electric heater or the like around the piping (intake pipe 30 or exhaust pipe 40) or the cylinder 20, the residual condensed water can be removed by heating.

  ・ Sensor heating control for starting heating of the sensor, that is, energization (heating of the heater) to the heating device (for example, electric heater) attached to the sensor, that is, so-called preheat control, is performed slightly before the engine is started. You can also. Here, the sensor heating (preheat) start timing corresponding to a short time before the engine start is, for example, a change in the open / close state of the vehicle door, a change in the on / off state of the vehicle door lock mechanism, a load change in the driver's seat, In the case of a keyless system, it can be detected based on a signal transmitted in response to an operator's remote operation. In this case, for example, prior to execution of sensor heating (preheating), it is effective to determine whether or not sensor heating is performed (execution or cancellation) based on the residual condensed water amount Qw2.

  The type of target sensor is not limited to a linear detection type oxygen concentration sensor (so-called A / F sensor), and may be, for example, a binary detection type oxygen concentration sensor (so-called O2 sensor). Other gas sensors (sensors that detect gas components), for example, NOx sensors, NH3 sensors, and the like may be used as the target sensors. Furthermore, even if it is a sensor other than the gas sensor, any sensor (for example, a pressure sensor) can be used as the target sensor as long as it is activated in a predetermined temperature range.

  The location of the target sensor is not limited to the engine exhaust passage, and may be the engine intake passage. However, as described above, the above-described sensor water exposure is particularly likely to occur in the exhaust passage.

  The type of engine to be controlled (including an in-cylinder injection gasoline engine, a compression ignition type diesel engine, etc.) and the system configuration can be changed as appropriate according to the application. For example, the exhaust pipe inner wall temperature sensor 41b can be omitted. When such a configuration change is made for the above-described embodiment, the details of the various processes (programs) described above may be changed (design change) as appropriate in accordance with the actual configuration. preferable.

  In the embodiment and the modification, it is assumed that various kinds of software (programs) are used. However, similar functions may be realized by hardware such as a dedicated circuit.

The block diagram which shows the outline of the engine control system by which these each apparatus is mounted about one Embodiment of the condensed water amount detection apparatus and sensor heating control apparatus of an internal combustion engine which concern on this invention. (A) is a side view showing an overview structure of an oxygen concentration sensor used in the system, and (b) is a cross-sectional view showing an internal structure of the sensor. The circuit diagram according to function which shows the part (circuit) which concerns on the sensor heating control of the sensor heating control apparatus mounted in the system. The schematic diagram which expands and shows the mode in the exhaust pipe in the exhaust gas upstream vicinity of an oxygen concentration sensor. The schematic diagram when looking inside the exhaust pipe from the exhaust upstream side. The flowchart which shows the process sequence of the heater control which concerns on this embodiment. The flowchart which shows the process sequence of heater energization permission judgment which concerns on the same embodiment. 4 is a flowchart showing a processing procedure when setting a delay time in the embodiment. The graph which shows the setting aspect about the setting process of the delay time. The graph which shows the setting aspect about the setting process of the delay time. The flowchart which shows the process sequence of the condensed water amount detection which concerns on this embodiment. The graph which shows the detection aspect about the detection process of the same condensed water amount. About sensor heating control concerning this embodiment, (a)-(g) is a timing chart which shows transition of each parameter in connection with the sensor heating control, respectively. About sensor heating control concerning the embodiment, (a)-(g) is a timing chart which shows transition of each parameter in connection with the sensor heating control, respectively. The graph which shows the modification of the detection aspect about the detection process of the amount of condensed water.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 20 ... Cylinder (cylinder), 40 ... Exhaust pipe, 40a-40c ... Piping, 41 ... Catalyst, 41a ... Exhaust temperature sensor, 41b ... Exhaust pipe inner wall temperature sensor, 42a, 42b ... Oxygen concentration sensor, 50 ... ECU (electronic control unit), 400... Flange portion, 400 a, 400 b .. flange, 402... Projection, 421.

Claims (15)

  When the internal combustion engine is started and stopped before reaching a sufficient operating time, the amount of condensed water generated in the intake passage or exhaust passage of the internal combustion engine by the operation is detected, and the amount of condensed water is calculated. A condensed water amount detection device for an internal combustion engine, comprising: a condensed water amount acquisition means for acquiring a condensed water amount parameter corresponding to one of a parameter shown and a parameter obtained by using the condensed water amount.   2. The internal combustion engine according to claim 1, further comprising a condensate amount storage unit that stores a condensate amount parameter acquired by the condensate amount acquisition unit with respect to a predetermined storage device that can retain data even after the internal combustion engine is stopped. Condensate detection device.   The condensed water amount detection device for an internal combustion engine according to claim 2, further comprising a condensed water amount update means for updating a condensed water amount parameter stored in the storage device based on an operation time until the stop every time the internal combustion engine is started. .   The condensed water amount updating means resets the condensed water amount parameter stored in the storage device when the operation time until the stop is sufficiently long, and when the operation time until the stop is not sufficiently long, The condensed water amount detection device for an internal combustion engine according to claim 3, wherein the condensed water amount parameter acquired by the condensed water amount acquisition means at this time is added to the condensed water amount parameter stored in the storage device.   The condensed water amount obtaining means estimates the amount of condensed water generated by the operation based on the parameter indicating the body temperature of the internal combustion engine and the operation time from the start to the stop of the engine, thereby obtaining the estimated value. The condensed water amount detection device for an internal combustion engine according to any one of claims 1 to 4, which is acquired as the condensed water amount parameter. Provided in the intake passage or exhaust passage of the internal combustion engine with a heat generating device that generates heat as the drive amount increases and the drive amount increases, and is activated in a predetermined temperature range and exhibits high detection capability A device that is applied to a predetermined target sensor and controls a driving amount of the heat generating device,
When starting the internal combustion engine, the control mode related to the drive amount of the heat generating device is variably set according to the sum of the amount of residual condensed water remaining and the amount of new condensed water newly generated by the current start. A sensor heating control device comprising heating control means for performing the above.   The heating control means is based on the sum of the amount of residual condensed water and the amount of new condensed water, and the length of a delay period (delay time) that is a period during which the drive is prohibited or limited as a period preceding the normal drive of the heat generating device The sensor heating control device according to claim 6, wherein the sensor is variably set.   The said heating control means uses the condensed water amount parameter acquired by the said condensed water amount acquisition means in the condensed water amount detection apparatus of the internal combustion engine as described in any one of Claims 1-5 as said residual condensed water amount. The sensor heating control apparatus according to claim 6 or 7. The target sensor is an exhaust system sensor provided in an exhaust passage through which exhaust is discharged after a combustion stroke of the internal combustion engine,
The sensor according to any one of claims 6 to 8, wherein the residual condensed water amount and the new condensed water amount are the amount of condensed water accumulated in a recess in an exhaust passage formed in the vicinity of the exhaust upstream side of the target sensor. Heating control device.   The sensor heating control device according to claim 9, wherein the recess is formed on a lower side in a vertical direction of an exhaust passage of the internal combustion engine when in use.   The sensor heating control device according to claim 9 or 10, wherein the recess is formed in a flange for connecting an exhaust pipe forming an exhaust passage of the internal combustion engine. The target sensor is attached to the upper side in the vertical direction of the exhaust pipe,
The sensor according to claim 11, wherein a protuberance of the exhaust pipe or a member separate from the exhaust pipe is provided in the vicinity of the flange for connecting the exhaust pipe so as to direct the exhaust flow upward in the vertical direction. Heating control device.   The exhaust system sensor according to any one of claims 9 to 12, wherein the exhaust system sensor is provided on an exhaust upstream side of an exhaust purification device that purifies exhaust discharged from the engine in an exhaust passage of the internal combustion engine. Sensor heating control device.   The sensor heating control device according to any one of claims 6 to 13, wherein the target sensor is an oxygen concentration sensor that detects an oxygen concentration and outputs the detection result.   Condensation of an internal combustion engine, which is applied to an internal combustion engine having a sensor in an exhaust passage, and has means for detecting the amount of condensed water accumulated in a recess in the exhaust passage formed near the exhaust upstream side of the sensor Water volume detection device.

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