JP4900049B2 - In-cylinder pressure sensor output characteristic detection device and output correction device - Google Patents

Description

  The present invention relates to an in-cylinder pressure sensor that detects an in-cylinder pressure (combustion chamber pressure) of a predetermined cylinder of an internal combustion engine, and detects an output characteristic of the in-cylinder sensor. The present invention relates to an output correction device that corrects the sensor output of a target sensor based on output characteristics detected by the detection device.

  In a reciprocating engine (internal combustion engine) in which an air-fuel mixture is burned in a cylinder (particularly in the combustion chamber) and the piston is lowered by the pressure to rotate the output shaft (crankshaft), the combustion pressure in the cylinder is It is a parameter that directly indicates the state of combustion in the cylinder. Usually, if such a combustion state can be grasped, for example, it is possible to estimate the ignition timing and combustion temperature, further detect knocking, detect the peak position of combustion pressure, detect misfire, and the like. For this reason, in recent years, it has been studied to use the combustion pressure detected by various methods for various engine controls including control of fuel injection timing and air-fuel ratio.

  By the way, as a method for detecting the combustion pressure, an in-cylinder pressure sensor is provided for the cylinder (cylinder), and the in-cylinder pressure of the engine based on the output value of the in-cylinder pressure sensor, and thus the in-cylinder pressure during combustion (combustion pressure). ) Is being investigated. However, an appropriate value is not always obtained as the output of the in-cylinder pressure sensor. For example, drift may occur in the output signal due to external factors such as temperature changes, and an unnecessary offset (bias) may be superimposed on the sensor value, or the sensor itself may vary in characteristics (due to manufacturing tolerances) or change over time. An error may occur in the gain (sensing sensitivity coefficient). Therefore, conventionally, as in the technique described in Patent Document 1, for example, a method for compensating for the error by calculating a gain and an offset has been proposed.

Specifically, in the apparatus described in Patent Document 1, the output values (sensor values) Sr1 and Sr2 of the in-cylinder pressure sensor at two crank angle positions (preset positions) in the compression stroke, and the reference pressure ( Reference values for sensor value correction) P1 and P2, and simultaneous equations based on polytropic changes in the compression stroke P1 = A × Sr1 + B, P2 = A × Sr2 + B (Equation 1)
, The gain value A and the offset value B (sensor output characteristics) are calculated, and the sensor value is corrected based on the calculated gain value and offset value. In this apparatus, the reference pressures P1 and P2 are estimated by calculation from the output value of the intake pressure sensor in the intake stroke.
JP 2002-242750 A

  By the way, in recent years, the inventor has researched a cheaper in-cylinder pressure sensor (simple sensor) that has a larger error between the sensor output and the true value than an expensive in-cylinder pressure sensor (general sensor) that is generally considered for practical use. It is carried out. This is because even with such a simple sensor, there is a possibility that the detection accuracy of the sensor can be increased to a practical level by correcting the sensor output. According to the inventor's research, the output characteristics of the simple sensor are more likely to shift (error) in linearity and gain than those of the general sensor. Hereinafter, the output characteristics of the simple sensor will be described with reference to FIGS. 11A and 11B while comparing with the output characteristics of the general sensor. Of the pressure characteristics shown in FIGS. 11A and 11B, those indicated by solid lines L50a and L50b are true pressure characteristics, and those indicated by alternate long and short dash lines L51a and L51b are true values. The pressure characteristics in the case where a deviation (error) occurs in the linearity compared to the one shown by the two-dot chain lines L52a and L52b caused a deviation (error) in the linearity and gain compared to the true value. In the case of pressure. In addition, the reference pressure on the horizontal axis in the graph of FIG. 11B is a reference pressure value used for estimating the sensor output in the same manner as the reference pressures P1 and P2 described above. Here, the reference pressure corresponds to the true value. Is set.

  That is, in general sensors, output characteristics close to true values (solid lines L50a, L50b) can be obtained. On the other hand, in the output characteristics of the simple sensor, a deviation (error) occurs in the linearity (one-dot chain lines L51a and L51b), and a deviation (error) also occurs in the gain (two-dot chain lines L52a and L52b). There are many. If a deviation (error) occurs not only in the linearity but also in the gain as described above, it is very difficult to correct the sensor output. For example, in the inventor's experiment and the like, the detection accuracy could not be increased to the extent that it could be put into practical use even with the apparatus of Patent Document 1.

  The present invention has been made in view of such circumstances, and an output characteristic detection device for an in-cylinder pressure sensor capable of detecting the sensor output characteristic of the target sensor with higher accuracy, and the sensor output of the target sensor with higher accuracy. The main object of the present invention is to provide an output correction device for an in-cylinder pressure sensor capable of correcting the above.

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

In the first invention, the present invention is applied to an engine (internal combustion engine) that converts energy from combustion in a combustion chamber in a cylinder (combustion chamber of each cylinder in the case of multiple cylinders) into mechanical motion (for example, rotational motion), An apparatus for detecting an output characteristic of an in-cylinder pressure sensor that detects an in-cylinder pressure that is a pressure in a combustion chamber for a predetermined cylinder in the engine (an in-cylinder pressure sensor output characteristic detection apparatus), In-cylinder pressure is detected at one or more pressure detection timings, and at least one of a gain and an offset indicating the output characteristics of the target sensor is estimated based on the detected values of the one or more in-cylinder pressures. Output characteristic estimating means; and timing setting means for variably setting the pressure detection timing based on a reference parameter which is a predetermined parameter. That, characterized in that.

  The inventor has a detection timing (pressure detection timing) of the in-cylinder pressure (equivalent to the output values Sr1 and Sr2 in the apparatus of Patent Document 1) used in calculating the sensor output characteristics in the device of Patent Document 1 described above. Because of the inappropriateness, it was considered that sufficient accuracy could not be obtained as the detection accuracy of the sensor output characteristics, and hence the correction accuracy of the sensor output. Through experiments and the like, it was found that the optimum pressure detection timing can vary depending on various parameters, and the above-described apparatus was invented. With such a device, by providing a timing setting means, it becomes possible to variably set the pressure detection timing based on a predetermined parameter (reference parameter), and to detect the output characteristics of the target sensor with higher accuracy. Will be able to.

According to a second aspect , in the first aspect , the reference parameter is a parameter for predicting an ignition timing of fuel combustion.

The inventor has confirmed through experiments and the like that the optimum value of the pressure detection timing is particularly affected by the ignition timing. In this regard, in the second aspect of the invention , the timing setting means can variably set the pressure detection timing based on the ignition timing in the coming (next) combustion. For this reason, according to such an apparatus, the pressure detection timing can be set at a more appropriate timing. It is effective to control the ignition timing based on a variable setting of parameters relating to engine operating conditions (combustion conditions). Here, the parameters relating to the combustion condition include, for example, ignition timing (ignition is quicker toward the advance side) variable (spark ignition type), injection timing (ignition is quicker toward the advance side), variable (compression ignition type direct injection) ), In-cylinder pressure (larger ignition is faster) variable, in-cylinder temperature (higher temperature is faster ignition) variable, gas mixture component (flammable gas is faster ignition) variable, mixture degree of mixture (The closer the mixing degree is to a sufficient value, the faster the ignition is), and further, the auxiliary ignition amount by the ignition auxiliary device (glow plug, etc.), the presence or absence of the pilot injection and the pilot injection amount (larger the faster the ignition), etc. Parameters can be used.

In this case, as in the third aspect of the invention, the ignition timing corresponding to the combustion start timing in the combustion chamber is controlled to the target ignition timing, and the parameter for predicting the fuel combustion ignition timing is the target ignition timing. It is effective to have a composition that is time.

  With such a configuration, the timing setting means can variably set the pressure detection timing based on the target ignition timing which is a target value of the ignition timing to be controlled from now on. It becomes possible to set at an appropriate timing. In order to control the ignition timing with high accuracy, it is effective to variably set the target ignition timing based on parameters (for example, engine speed and fuel injection amount) that are referred to when determining engine operating conditions. is there.

On the other hand, in a fourth invention according to the second invention , the apparatus further comprises ignition timing prediction means for predicting an ignition timing based on a combustion state in the combustion chamber, and the parameter for predicting the ignition timing of the fuel combustion comprises: It is an ignition timing (predicted value of ignition timing) predicted by the ignition timing prediction means.

Rather than inferring from the control target value (target ignition timing) described above, that is, a command value for the actuator, it is more accurate to detect the combustion state at that time (for example, detected as in-cylinder pressure) by a sensor or the like. You may be able to get Therefore, the fourth invention may be more beneficial than the third invention depending on the application and the like. In particular, it is expected that the current processing speed will be significantly improved in the future, and the prediction accuracy is expected to increase accordingly. For this reason, the fourth invention may become more and more important in the future.

According to a fifth invention, in any one of the second to fourth inventions , the engine rotates the output shaft based on the energy from the combustion, and the volume of the combustion chamber is increased according to the rotation of the output shaft. The mixture of the fuel and air is compressed in the combustion chamber by changing, and the fuel is combusted using the compression, and the pressure detection timing is determined by the rotation angle position of the output shaft. In addition, the pressure detection timing is advanced from a reference angle (TDC (top dead center) in a reciprocating engine), which is an output shaft angle in the compression stroke of the air-fuel mixture, which minimizes the volume of the combustion chamber. A first timing corresponding to the angle (early) side and a second timing corresponding to the advance side of the first timing in the same compression stroke are included.

As described above, based on the sensor output of the in-cylinder pressure sensor at the output shaft rotation angle positions at two points (at least two points) in the compression stroke indicating the polytropic change (for example, according to (Expression 1) above), the sensor output characteristics are It is possible to estimate with high accuracy. Therefore, any one of the second to fourth inventions is particularly useful when applied to such a configuration. Note that the sensor output characteristics can be estimated using another formula (or map) without being limited to the above (formula 1).

According to a sixth invention, in the fifth invention , there is further provided a judging means for judging whether or not the ignition timing for the earliest injection in one combustion cycle is later than the reference angle, The timing setting unit changes the setting position of the first timing in accordance with a determination result of the determination unit.

According to the inventors' experiments and the like, the fifth aspect of the invention is the earliest injection in one combustion cycle (for example, if it is a single-stage injection with only a main injection, it may be a main injection or a pilot injection / main injection two-stage injection). It was confirmed that the sensor output characteristic can be estimated more accurately by setting the first timing with respect to the (suitable) position (timing) corresponding to the ignition timing for pilot injection. Therefore, the fifth invention is a more useful device by adopting the configuration of the sixth invention .

  Specifically, in order to estimate the sensor output characteristic more accurately, it is preferable that the first timing is set as late as possible within a range showing a polytropic change in the in-cylinder pressure.

Therefore, for example, as in the seventh invention, in the sixth invention , the timing setting means is set so that the judgment means sets the ignition timing for the earliest injection in the one combustion cycle from the reference angle. It is effective to set the first timing in the vicinity of the advance side of the reference angle when it is determined that the time is late.

When the ignition timing is later than the reference angle, the polytropic change is obtained throughout the compression stroke of the air-fuel mixture, but after the reference angle is out of the compression stroke, the polytropic change is disturbed. In this regard, in the seventh aspect, when the ignition timing is later than the reference angle, the first timing is in the vicinity of the advance angle side of the reference angle, that is, the in-cylinder pressure is in a range showing a polytropic change. It is set in the vicinity of the retard angle side boundary, and the sensor output characteristic can be estimated more accurately.

Further, for example, as in the eighth invention, in the sixth or seventh invention , the timing setting means is used, and the judgment means uses the ignition timing for the earliest injection in the one combustion cycle as the reference. When it is determined that the angle is earlier than the angle, it is effective to set the first timing near the advance side of the ignition timing.

When the ignition timing is earlier than the reference angle, even in the compression stroke of the air-fuel mixture, after the ignition, the polytropic change is disturbed due to the pressure change accompanying the ignition. In this regard, in the eighth aspect of the invention , when the ignition timing is earlier than the reference angle, the first timing is in the vicinity of the advance side of the ignition timing, that is, the in-cylinder pressure is within a range showing a polytropic change. It is set near the retard side boundary, and the sensor output characteristic can be estimated more accurately.

By the way, regarding any one of the fifth to eighth inventions , even if the offset is estimated based on the detected values of the in-cylinder pressure at the first and second timings, the estimation accuracy is improved. Is possible. However, the degree of improvement in the estimation accuracy is greater when it is adopted when increasing the accuracy of gain estimation. Accordingly, as in the ninth aspect , the output characteristic estimating means estimates the gain of the target sensor based on the in-cylinder pressure at the first timing and the in-cylinder pressure at the second timing. It is more beneficial to have a configuration of

According to the output characteristic sensing device above SL-cylinder pressure sensor, the output characteristics of the object sensor, it is possible to obtain an output error thus the sensor. Then, according to the output error obtained in this way, it becomes possible to correct (calibrate) the output characteristics of the target sensor with higher accuracy. Therefore, by using such a device, for example, as in the tenth invention,
Based on the output characteristics of the object sensor estimated by the output characteristic estimating means in the output characteristic sensing device "up Symbol cylinder pressure sensor, cylinder pressure sensor comprising a correction means for performing correction to the sensor output of the target sensor Output correction device "
Etc. can be realized.

  Hereinafter, with reference to FIGS. 1 to 10, an embodiment embodying an output characteristic detecting device and an output correcting device for an in-cylinder pressure sensor according to the present invention will be described. The system of the present embodiment is an engine control system that controls a diesel engine equipped with a common rail fuel injection device. Both the detection device and the correction device of the present embodiment are mounted in this system, and in this system, the pressure of the combustion chamber (cylinder pressure) is provided in each cylinder of the engine to be controlled by these devices. For each of the in-cylinder pressure sensors that detect the above, the output characteristics of each sensor are detected. Then, the output of each sensor is corrected based on the detected output characteristics.

  First, a schematic configuration of an engine control system according to the present embodiment will be described with reference to FIG. The signal lines in the figure correspond to the wiring layout. As an engine to be controlled by this system (engine 10 in the figure), a multi-cylinder (for example, in-line four-cylinder) engine mounted on a four-wheeled vehicle (for example, an AT vehicle) is assumed. However, in FIG. 1, only one cylinder (cylinder 20 in the figure) is shown for convenience of explanation. The engine 10 is a 4-stroke (4 × piston stroke) reciprocating diesel 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 system includes an engine 10 that rotates a crankshaft 10a (a portion shown in the figure is a pulsar gear mounted on a crankshaft) that is an output shaft by torque generated through combustion in a cylinder 20. As a control object, it has various sensors for controlling the engine 10, an ECU (electronic control unit) 70, and the like. Hereinafter, each element constituting this system including the engine 10 to be controlled will be described in detail.

  The engine 10 (diesel engine) to be controlled here basically includes a cylinder 20 formed by a cylinder block 20a and a cylinder head 20b. The cylinder block 20a is provided with a cooling water passage (water jacket) 21a for circulating the cooling water through the engine 10, and a water temperature sensor 21b for detecting the temperature of the cooling water (cooling water temperature) in the water passage 21a. The engine 10 is cooled by the cooling water. Also, a piston 20c is accommodated in the cylinder 20, and a crankshaft 10a that is an output shaft of the engine 10 is rotated by the reciprocating motion of the piston 20c. A crank angle sensor 10b (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 10a. The rotational angle position of the output shaft) and the rotational speed (engine rotational speed) can be detected.

  A combustion chamber 20d is formed between the cylinder head 20b fixed to the upper end surface of the cylinder block 20a and the crown surface of the piston 20c in the cylinder 20. In the cylinder head 20b, for example, two intake ports (intake ports) 11 and exhaust ports (exhaust ports) 12 that open to the combustion chamber 20d are formed, for example, two for each cylinder (a total of four ports). The intake port 11 and the exhaust port 12 are respectively driven by an intake valve (intake valve) 21 and an exhaust valve (exhaust valve) which are driven by cams (not shown) (specifically, cams attached to the camshaft interlocked with the crankshaft 10a). And 22). Further, in order to enable communication between the combustion chamber 20d in the cylinder 20 and the outside of the vehicle (outside air) through these ports, an intake pipe 30 (intake air) for sucking outside air (fresh air) into the cylinder 20 is connected to the intake port 11. The exhaust port 12 is connected to an exhaust pipe 40 (exhaust passage) for discharging combustion gas (exhaust gas) from each cylinder.

  Fresh air is sucked into the intake pipe 30 constituting the intake system of the engine 10 while removing foreign substances in the air through an air cleaner (not shown) at the most upstream portion, and the flow rate of the fresh air is downstream of the air cleaner. An air flow meter 31 (for example, a hot wire type air flow meter) that detects (new air amount) as an electrical signal is provided. An intake pressure sensor 32 that detects the pressure of intake air is provided in the vicinity of the air flow meter 31. Further, on the downstream side of the air flow meter 31 and the intake pressure sensor 32, an electronic control type whose opening degree is electronically adjusted by an intake air compressor 50a (described later in detail) and an actuator such as a DC motor. A throttle valve 33 (intake throttle valve) and a throttle opening sensor 33a for detecting the opening (throttle valve opening) and movement (opening fluctuation) of the throttle valve 33 are provided.

  On the other hand, the exhaust pipe 40 constituting the exhaust system of the engine 10 is provided with a supercharging exhaust turbine 50b (described in detail later), an oxidation catalyst 44 and a DPF (Diesel Particulate Filter) 45 as an exhaust purification device. Has been. Further, exhaust temperature sensors 43a and 43b are provided in the vicinity of the upstream and downstream sides of the DPF 45, respectively. These sensors 43a and 43b are used, for example, for determining the center temperature of the DPF 45 during the regeneration process.

  Here, the DPF 45 is a continuously regenerating PM removal filter that collects PM (Particulate Matter) in the exhaust gas. For example, the DPF 45 is a main injection that is a fuel injection mainly for generating output torque. It can be used continuously by repeatedly burning and removing the collected PM by post-injection or the like (corresponding to a regeneration process). The DPF 45 carries a platinum-based oxidation catalyst (not shown) with a heat-resistant ceramic such as cordierite, and removes HC and CO together with a soluble organic component (SOF) which is one of the PM components. Can be done.

  The exhaust pipe 40 provided with the DPF 45 is further provided with a differential pressure sensor 46 for detecting a differential pressure between the pressure near the DPF 45 inlet and the pressure near the DPF 45 outlet. The differential pressure detected by the differential pressure sensor 46 corresponds to the pressure loss caused by the DPF 45 and indicates the degree of clogging of the DPF 45 due to the PM collection. For this reason, by referring to this differential pressure, it becomes possible to detect the amount of PM collected by the DPF 45 (PM collection amount).

  Further, an A / F sensor 42 that is a linear detection type oxygen concentration sensor is provided in the vicinity of the upstream side of the oxidation catalyst 44. The output of the sensor 42 is used for, for example, EGR control.

  On the other hand, in the fuel supply system of this system, the in-cylinder injection method is adopted as the fuel supply method. That is, high-pressure fuel (for example, light oil having an injection pressure of “1000 atm” or higher) supplied from a common rail (pressure accumulation pipe) (not shown) is directly supplied to the combustion chamber 20d in the cylinder 20 by injection. An injector 15 as an electromagnetically driven fuel injection valve is further provided. In the engine 10, the required amount of fuel is injected and supplied to each cylinder at any time by such valve opening drive of the injector. That is, when the engine 10 is in operation, intake air is introduced from the intake pipe 30 into the combustion chamber 20d of the cylinder 20 by the opening operation of the intake valve 21, and this is mixed with the fuel injected and supplied from the injector 15 in the state of the air-fuel mixture. Compressed by the piston 20c in the cylinder 20 and ignited (self-ignited) and combusted, and the exhaust valve 22 is opened to discharge the exhausted gas to the exhaust pipe 40.

  Further, in the combustion chamber 20d, the pressure in the cylinder 20 (in-cylinder pressure) is measured by a detection unit (the tip of the probe inserted into the combustion chamber 20d) located in the combustion chamber 20d. An in-cylinder pressure sensor 18 that outputs a detection signal (electrical signal) corresponding to is provided integrally with, for example, a glow plug as an ignition assist device (specifically, fixed to the cylinder head 20b). As a result, the combustion state in the cylinder 20 can be grasped, that is, the ignition timing and combustion temperature can be estimated, knocking detection, combustion pressure peak position detection, misfire detection, and the like can be performed. The in-cylinder pressure sensor 18 corresponds to the simple sensor described above. As with the injector 15, the in-cylinder pressure sensor 18 is also provided for each combustion chamber of each cylinder (all four) of the engine 10.

  Further, in this system, a turbocharger is disposed between the intake pipe 30 and the exhaust pipe 40. This turbocharger is a so-called variable nozzle type turbocharger, and includes an intake compressor 50a provided in the middle of the intake pipe 30 and an exhaust turbine 50b provided in the middle of the exhaust pipe 40. The turbine 50b is connected by a shaft (not shown). That is, the exhaust turbine 50b is rotated by the exhaust gas flowing through the exhaust pipe 40, and the rotational force is transmitted to the intake compressor 50a via the shaft. The air flowing through the intake pipe 30 is compressed by the intake compressor 50a and supercharged. Is done. Here, the exhaust turbine 50b includes a variable nozzle mechanism 50c formed of a well-known valve mechanism, and the exhaust gas that collides with the turbine 50b is changed by changing the area of the exhaust passage according to the opening / closing operation of the variable nozzle mechanism 50c. The flow speed of the turbine 50 and the rotation speed of the turbine 50b are also changed. In this turbocharger, the rotational speed of the exhaust turbine 50b is controlled based on the command value for the variable nozzle mechanism 50c, and the supercharging amount due to the rotation of the intake compressor 50a according to the rotation of the turbine 50b is variably controlled (nozzle). The amount of supercharging increases as the value is reduced. This supercharging increases the charging efficiency of the intake air into each cylinder. Note that an intercooler or the like for cooling the intake air is also provided for the intake pipe 30 as necessary.

  Furthermore, an EGR device for returning a part of the exhaust gas to the intake system as EGR (Exhaust Gas Recirculation) gas is also disposed between the intake pipe 30 and the exhaust pipe 40. This EGR device basically includes an EGR pipe 60a provided so as to communicate the intake pipe 30 and the exhaust pipe 40, an electromagnetic valve provided on the exhaust downstream side of the throttle valve 33 of the intake pipe 30, and the like. And an EGR valve 60b. The passage area of the EGR pipe 60a, and hence the EGR rate (the ratio of the EGR gas returned to the cylinder with respect to the entire exhaust gas) can be adjusted by the valve opening of the EGR valve 60b. Incidentally, this adjustment is performed based on the output of the A / F sensor 42. For example, when the EGR valve 60b is fully closed, the EGR pipe 60a is shut off and the EGR amount becomes “0”. If necessary, an EGR cooler for cooling the EGR gas is also provided for the EGR pipe 60a. In this EGR device, based on such a configuration, a part of the exhaust gas is recirculated to the intake system through the EGR pipe 60a, thereby lowering the combustion temperature and reducing the generation of NOx.

  Further, a vehicle (not shown) (for example, a four-wheel passenger car or a truck) that travels using the engine 10 as power is provided with various sensors for vehicle control in addition to the above-described sensors. For example, an accelerator sensor 71 that outputs an electric signal corresponding to the state (displacement amount) of the pedal is provided in an accelerator pedal corresponding to a driving operation unit for notifying the vehicle side of the torque required by the driver. It is provided to detect the operation amount (depression amount).

  In such a system, the ECU 70 functions as the detection device and the correction device of the present embodiment and performs engine control mainly as an electronic control unit. The ECU 70 (engine control ECU) includes a 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 responds accordingly to the above. By operating various actuators such as the throttle valve 33 and the injector 15, 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, injection timing, fuel injection amount, etc.) are calculated based on detection signals of the respective sensors, and by operating various actuators, The illustrated torque (generated torque) generated through fuel combustion in the combustion chamber), and consequently the shaft torque (output torque) actually output to the output shaft (crankshaft 10a) is controlled. In the control system of this embodiment as well as the known diesel engine system, during steady operation, the control system is provided in the intake passage (intake pipe 30) of the engine 10 for the purpose of increasing the amount of fresh air and reducing pumping loss. The intake throttle valve (throttle valve 33) is held in a substantially fully opened state. Therefore, control of the fuel injection amount is mainly used as combustion control during steady operation (particularly combustion control related to torque adjustment).

  Here, the microcomputer mounted on the ECU 70 basically includes a CPU (basic processing device) that performs various calculations, and a RAM as a main memory that temporarily stores data and calculation results during the calculation. (Random Access Memory), ROM (read only storage device) as program memory, EEPROM (electrically rewritable non-volatile memory) as data storage memory, backup RAM (vehicle battery etc. even after main power supply of ECU is stopped) Memory, which is constantly powered by a backup power source), signal processing devices such as A / D converters and clock generation circuits, and various arithmetic units 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. The ROM stores various programs and control maps related to engine control including programs related to detection and correction of output characteristics of the sensor, and the data storage memory (for example, EEPROM) designs the engine 10. Various control data including data are stored in advance.

  By the way, the apparatus of this embodiment also detects the in-cylinder pressure (corresponding to the output values Sr1 and Sr2 in the case of the apparatus of Patent Document 1) at a predetermined pressure detection timing, similarly to the apparatus described in Patent Document 1 described above. At the same time, the gain and offset indicating the output characteristics of the in-cylinder pressure sensor 18 (target sensor) are estimated based on the detected value of the in-cylinder pressure. Based on the detected output characteristics, output correction of the in-cylinder pressure sensor 18 is performed. However, in the present embodiment, one of the pressure detection timings is variably set based on a predetermined parameter (reference parameter), specifically, a parameter for predicting the ignition timing of fuel combustion.

  Next, an aspect of output correction of the in-cylinder pressure sensor 18 according to the present embodiment will be described with reference to FIGS. Here, as an example, the case where the output of the sensor 18 is applied to the correction of the fuel injection timing will be described.

  FIG. 2 is a flowchart showing a procedure for correcting the fuel injection timing. Note that this series of processing is basically executed in order at a frequency of once per combustion cycle for each cylinder of the engine 10 by executing a program stored in the ROM by the ECU 70. Also, 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 70, and updated as necessary.

  As shown in FIG. 2, in this control, first, in step S1, crank angles θ1, θ2 (pressure detection timing) used for calculating the output characteristics of the in-cylinder pressure sensor 18 are set. In this setting, the angle θ1 is set as a fixed value (for example, set at the initial stage of the compression stroke), and the angle θ2 is set as a variable value. FIG. 3 is a flowchart showing the procedure for setting the angle θ2. Hereinafter, a series of processes relating to the setting of the angle θ2 will be described with reference to FIG.

  As shown in FIG. 3, when setting this angle θ2, first, in step S101, predetermined parameters, for example, the engine speed at that time (actually measured value by the crank angle sensor 10b) and the fuel injection amount (in a separate routine). The set energization time of the injector 15 is taken in. Next, in step S102, the target ignition timing θign related to the earliest injection in one combustion cycle is set based on the engine speed and the fuel injection amount taken in in step S101. The target ignition timing θign corresponds to a target value of the ignition timing to be controlled from now on, that is, a parameter for predicting the ignition timing of fuel combustion. For example, by referring to a predetermined map, the target ignition timing θign corresponds to each parameter described above. The optimal time is set. Further, the unit of this time θign is ATDC (after top dead center), and the advance side of TDC (top dead center) has a “negative” sign and the retard side has a “positive” sign.

  Next, in step S103, the regeneration condition (for example, the center temperature of the DPF 45 by the exhaust temperature sensors 43a and 43b and the differential pressure by the differential pressure sensor 46 are larger than a predetermined value) are established requirements. It is determined whether or not (condition to perform) is satisfied. If it is determined in step S103 that the regeneration condition for the DPF 45 is satisfied, in the subsequent step S103a, the target ignition timing θign set in the previous step S102 is specified in advance for the DPF regeneration. The value is changed to Y (θign = Y). On the other hand, when it is determined in step S103 that the regeneration condition of the DPF 45 is not satisfied, such a change is not performed and the target ignition timing θign set in the previous step S102 is maintained.

  In the present embodiment, the ignition timing corresponding to the combustion start timing in the combustion chamber 20d is controlled with respect to the target ignition timing θign set as described above. That is, at the timing uniquely determined by the target ignition timing θign, the earliest injection in one combustion cycle (for example, if the main injection is a single-stage injection only of the main injection, the main injection is the two-stage injection of the pilot injection and the main injection). If so, pilot injection is performed).

  In a succeeding step S104, it is determined whether or not the target ignition timing θign is larger than a value “0” corresponding to TDC. If it is determined that the target ignition timing θign is greater than “0”, it is determined that the ignition timing is later than TDC, and in step S104a, the angle θ2 is set to TDC (“0”) in the compression stroke. Near the advance side, that is, a predetermined angle (in this case, a fixed value, but may be a variable value) before TDC (negative side). On the other hand, if it is determined that the target ignition timing θign is not greater than “0”, it is determined that the ignition timing is not later than TDC, and in step S104b, the angle θ2 is set to the target ignition timing in the compression stroke. It is set near the advance side of θign (corresponding to the ignition timing), that is, a predetermined angle (a fixed value here, but can be a variable value) (negative side) before the target ignition timing θign.

  In the present embodiment, the angle θ2 is sequentially set for each cylinder of the engine 10 for each combustion cycle. Hereinafter, with reference to FIG. 4 and FIG. 5, the setting mode of the angle θ2, particularly the setting position of the angle θ2, will be further described.

  FIG. 4A is a graph showing pressure characteristics when the ignition timing is earlier than TDC. In this graph, a solid line L11a indicates a pressure characteristic when the ignition is performed, and a broken line L11b indicates a pressure characteristic when the ignition is not performed.

  As shown in FIG. 4 (a), when the ignition timing is earlier than TDC, even in the compression stroke, after ignition, the change in polytropy is disturbed by the pressure change associated with the ignition. In this regard, in step S104b of FIG. 3, in the case shown in FIG. 4A, as shown in FIG. 4, the angle θ2 is in the compression stroke and is a predetermined angle before the ignition timing (ignition timing). In other words, it is in the polytropic change region and is set near the retard side boundary.

  On the other hand, FIG. 4B is a graph showing pressure characteristics when the ignition timing is later than TDC. In this graph, a solid line L12a indicates a pressure characteristic when ignition is performed, and a broken line L12b indicates a pressure characteristic when ignition is not performed.

  As shown in FIG. 4B, when the ignition timing is later than the TDC, a polytropic change can be obtained in the entire compression stroke, but after a TDC that deviates from the compression stroke, the polytropic change becomes disturbed. . In this regard, in step S104a in FIG. 3, in the case shown in FIG. 4B, as shown in FIG. 4, the angle θ2 is in the compression stroke and is a predetermined angle before TDC (advance of TDC). In the vicinity of the corner side), in other words, in the polytropic change region, it is set near the retard side boundary.

  Next, FIGS. 5A and 5B show how the angle θ2 is set for each of the single-stage injection using only the main injection Mn and the two-stage injection using the pilot injection Pt and the main injection Mn. It is a graph to show.

  First, for example, in the single-stage injection using only the main injection Mn, when the ignition timing related to the main injection Mn is later than the TDC, as shown in FIG. The angle θ2 is set with respect to the previous angle (FIG. 4B). On the other hand, in the two-stage injection by the pilot injection Pt and the main injection Mn, when the ignition timing related to the pilot injection Pt corresponding to “the first injection in one combustion cycle” is earlier than the TDC, the main injection Even if the ignition timing related to Mn is later than TDC, as shown in FIG. 5 (b), the angle θ2 is in the compression stroke with respect to a predetermined angle before the ignition timing related to the pilot injection Pt. It is set (FIG. 4 (a)).

  Thus, if there is an injection that ignites at a time earlier than TDC, the angle θ2 is set based on the ignition timing of the earliest injection (the earliest injection in one combustion cycle) of the injections. Will be done.

  In step S1 of FIG. 2, the crank angles θ1 and θ2 used for calculation of the output characteristics of the in-cylinder pressure sensor 18 are set through the processing as described above. In subsequent steps S2 and S3, output characteristics (offset and gain) of the in-cylinder pressure sensor 18 are calculated based on the set angles θ1 and θ2. Hereinafter, the processes in steps S2 and S3 will be described in more detail with reference to FIGS. Here, the processing related to the offset in step S2 will be described with reference to FIGS. 6 and 7, and then the processing related to the gain in step S3 will be described with reference to FIGS.

  FIG. 6 is a flowchart showing a processing procedure of processing relating to offset calculation and abnormality determination, and FIG. 7 is a graph showing the processing mode. FIG. 7A is a graph showing the relationship between the true pressure (actual in-cylinder pressure) and the output of the in-cylinder pressure sensor 18. In FIG. 7A, the output characteristic (reference characteristic) in a state where no offset is superimposed is indicated by a solid line, and the output characteristic (two types) in a state where a predetermined offset is superimposed is indicated by a broken line. Respectively. FIG. 7B is a graph showing the relationship between the crank angle and the in-cylinder pressure. In FIG. 7B, the output characteristic of the in-cylinder pressure sensor 18 is indicated by a solid line, and the true pressure characteristic is indicated by a broken line. In FIG. 7 (b), the period of the crank angles θ1 to θ2 corresponds to a compression stroke that shows a change in the polytropy during the operation period of the engine 10, and during this period, the pressure and temperature in the combustion chamber 20d Is an intermediate change between the isothermal change and the adiabatic change, and the physical characteristics are stabilized.

  As shown in FIG. 6, in this series of processes, first, in step S11, the sensor value Ps1 of the in-cylinder pressure sensor 18 at the crank angle θ1 (FIG. 7B) is captured. Next, in step S12, the cylinder volume (volume of the combustion chamber 20d) V1 corresponding to the crank angle position of the crank angle θ1 is read from the data storage memory (mounted on the ECU 70). In the subsequent steps S13 and S14, as in the case of the crank angle θ1, this time, the sensor value Ps2 of the in-cylinder pressure sensor 18 is fetched for the crank angle θ2 (FIG. 7B), and the data storage memory is used. The cylinder volume V2 corresponding to the crank angle position of the same angle θ2 is read out.

  In subsequent step S15, the polytropic index n corresponding to the period of the crank angles θ1 to θ2 is read from the data storage memory (mounted on the ECU 70). The polytropic index is obtained based on, for example, the in-cylinder pressure (or intake pressure) and the engine rotation speed, and is mapped and stored using the in-cylinder pressure and the engine rotation speed as coordinate axes, for example.

In the subsequent step S16, the pressure ratio κ between the two crank angle positions (crank angles θ1, θ2) is calculated based on the parameters acquired in the above steps.
κ = (V1 / V2) ^ n (Expression 2)
It is calculated from the relational expression. By the way, this (Equation 2) is obtained from the fact that “P1 · V1 ^ n = P2 · V2 ^ n” (where P1 and P2 are the pressures at V1 and V2 respectively) holds during the polytropy change. .

In the subsequent step S17, the parameters obtained in the above steps, more specifically, the sensor values Ps1 and Ps2 of the in-cylinder pressure sensor 18 at the crank angles θ1 and θ2 (steps S11 and S13), and the pressure ratio κ (step S16). Based on the offset value Offset0,
Offset0 = (κ · Ps1−Ps2) / (κ−1) (Expression 3)
It is calculated from the relational expression. That is, with this process, the offset value (bias amount) related to the output of the in-cylinder pressure sensor 18 is calculated. In addition, as indicated by a broken line in FIG. 7A, when an offset is included, the output characteristic shifts to the positive side or the negative side with respect to the original sensor output (solid line) as the reference value. Become.

  Next, it is determined whether or not there is an abnormality in the calculated offset value Offset0. That is, first, in step S18, prescribed values m1 and m2 are set as a lower limit value and an upper limit value that define an allowable range, respectively. In the subsequent step S19, based on the prescribed values m1 and m2, that is, whether or not the relational expression “m1 <Offset0 <m2” is satisfied, the presence / absence of an abnormality in the offset value Offset0 is determined. The prescribed values m1 and m2 are determined based on engine design data such as the volume of the combustion chamber 20d or experimental values, for example.

  In the abnormality determination in step S19, for example, as shown by a broken line in FIG. 7A, even when there is an offset, it is larger than the allowable range (specified value m1) indicated by a one-dot chain line in FIG. If it falls within the specified value m 2), it is determined that it is normal. If it is determined in step S19 that the offset value Offset0 is normal, the series of processes in FIG. 6 is terminated, and the process proceeds to step S3 in FIG.

  On the other hand, if the offset value Offset0 does not fall within the allowable range, it is determined in step S19 that the offset value Offset0 is abnormal. In step S191, after a fail-safe process set in advance for an offset abnormality is executed, the series of processes in FIG. 6 ends. Thereafter, the process proceeds to step S3 in FIG. 2 as in the normal state only when the interruption of control is not instructed in the fail-safe process in step S191. In the present embodiment, as a fail-safe process in step S191, for example, a warning light (not shown) is lit to correct the offset signal drift amount and notify the driver that there is an abnormality in the in-cylinder pressure sensor. To. That is, even after the fail safe process is executed, the control according to the flowchart of FIG. 6 is continued, and after the series of processes of FIG. 6 ends, the process proceeds to step S3 of FIG.

  Next, processing related to gain will be described. FIG. 8 is a flowchart showing a processing procedure of processing relating to gain calculation and abnormality determination, and FIG. 9 is a graph showing the processing mode. FIG. 9A is a graph showing the relationship between the true pressure (actual in-cylinder pressure) and the output of the in-cylinder pressure sensor 18. In FIG. 9A, the output characteristic (reference characteristic) when the gain does not include an error is indicated by a solid line, and the output characteristic (two types) when the gain includes an error is indicated by a broken line. FIG. 9B is a graph showing the relationship between the crank angle and the in-cylinder pressure. In FIG. 9B, the output characteristic of the in-cylinder pressure sensor 18 is indicated by a solid line, and the characteristic of the reference pressure (reference value for sensor value correction) is indicated by a broken line. In FIG. 9B as well, as in FIG. 7B, the period of the crank angles θ1 to θ2 corresponds to a compression stroke indicating a polytropic change.

  As shown in FIG. 8, in this series of processing, first, the valve opening timing of the intake valve 21 is input in step S21, and in the subsequent step S22, the sensor value of the intake pressure sensor 32 is based on this input value. Is determined (for example, 5 ° CA before valve closing). In the subsequent step S23, the sensor value of the intake pressure sensor 32 is acquired for the crank angles θ1, θ2 (FIG. 9B) based on the acquisition timing, and in the next step S24, the reference corresponding to the acquired sensor value is acquired. The pressure difference “Pk2−Pk1” (FIG. 9B) between the pressures Pk1 and Pk2 is read from the data storage memory (installed in the ECU 70). Next, in steps S25 and S26, the sensor values Ps1 and Ps2 of the in-cylinder pressure sensor 18 at the crank angles θ1 and θ2 are taken in, respectively.

In the following step S27, the parameters acquired in the above steps, specifically, the reference pressure difference “Pk2−Pk1” (step S24), and the sensor values Ps1 and Ps2 of the in-cylinder pressure sensor 18 at the crank angles θ1 and θ2 (steps). Based on S25, S26), the gain value Gain0 is
Gain0 = (Ps2-Ps1) / (Pk2-Pk1) (Formula 4)
It is calculated from the relational expression. That is, with this processing, the gain value (sensing sensitivity coefficient) related to the output of the in-cylinder pressure sensor 18 is calculated. In addition, as shown by a broken line in FIG. 9A, when an error is included in the gain, the positive side (large inclination) or the negative side (inclination) with respect to the original sensor output (solid line) as a reference value The output characteristics will shift to (small).

  Next, it is determined whether or not there is an abnormality in the calculated gain value Gain0. That is, first, in step S28, prescribed values n1 and n2 are set as a lower limit value and an upper limit value that define an allowable range, respectively. Then, in the following step S29, whether or not there is an abnormality in the gain value Gain0 is determined based on the prescribed values n1 and n2, that is, based on whether or not the relational expression “n1 <Gain0 <n2” is satisfied. The prescribed values n1 and n2 are determined based on engine design data such as the volume of the combustion chamber 20d or experimental values, for example.

  In the abnormality determination in step S29, for example, as shown by a broken line in FIG. 9A, even if an error is included in the gain, this is indicated by an allowable range indicated by a one-dot chain line in FIG. If it is larger and less than the specified value n2), it is determined that it is normal. If it is determined in step S29 that the gain value Gain0 is normal, the series of processes in FIG. 8 is terminated, and the process proceeds to step S4 in FIG.

  On the other hand, if the gain value Gain0 does not fall within the allowable range, it is determined in step S29 that the gain value Gain0 is abnormal. In step S291, after a fail-safe process set in advance for gain abnormality is executed, the series of processes in FIG. 8 ends. After that, only when the interruption of control is not instructed in the fail-safe process in step S291, the process proceeds to step S4 in FIG. In the present embodiment, as the fail safe process in step S291, the feedback control related to the fuel injection timing control using the output of the in-cylinder pressure sensor 18 is switched to the open loop control, and a predetermined value is used as an alternative value of the sensor value of the sensor 28. The evacuation travel is performed by setting a specified value. In other words, the control according to the flowchart of FIG. 8 is temporarily interrupted by this fail-safe process, and the control proceeds to retreat travel. Here, it is desirable that the specified value used as the substitute value is set by selecting a value that can be used in general in various situations.

  As described above, the output characteristics (gain and offset) of the in-cylinder pressure sensor 18 are calculated by the processes shown in FIGS. At this time, the output characteristics of the sensor 18 are all calculated based on the angle θ2 set at an appropriate timing by the processing of FIG. Thereby, in this embodiment, the output characteristic of the in-cylinder pressure sensor 18 is estimated with high accuracy. FIG. 10 is a graph showing gain calculation modes when different angles (angles θ2a to θ2c) are set as the angle θ2 with respect to the fixed angle θ1. The reference pressure on the horizontal axis in the graph of FIG. 10 corresponds to the reference pressures Pk1 and Pk2 used for estimating the sensor output, and is set in a manner corresponding to the true value. In FIG. 10, the solid lines L0 and L2 indicate the true pressure characteristic (solid line L0) and the output characteristic (solid line L2) of the in-cylinder pressure sensor 18, respectively. Incidentally, in the example of FIG. 10, it is assumed that the ignition timing is later than TDC. That is, the polytropic change can be obtained throughout the compression stroke.

  As shown in FIG. 10, as the angle θ2 is closer to TDC (in the compression stroke), the gain (broken lines L2a to L2c) obtained by the processing of FIG. 8 is more accurately output from the in-cylinder pressure sensor 18. The characteristic (solid line L2) is shown. That is, for each gain (broken lines L2a to L2c) shown in FIG. 10, the gain (broken line L2b) calculated by angle θ2b (> angle θ2a) is greater than the gain (broken line L2a) calculated by angle θ2a. However, the gain (broken line L2c) calculated by the angle θ2c (> angle θ2b) near the TDC is more accurately output characteristics (solid line L2) than the gain (broken line L2b). ). In this regard, as described above, in the present embodiment, the angle θ2 is set in the vicinity of the advance side of the TDC (for example, the angle θ2c) by the processing in step S104a of FIG. For this reason, the gain of the in-cylinder pressure sensor 18 can be estimated with high accuracy.

  When the ignition timing is earlier than TDC, the angle θ2 is set in the vicinity of the advance side of the ignition timing by the processing in step S104b of FIG. That is, also in this case, the angle θ2 is set in the polytropic change region and in the vicinity of the retard side boundary, and the gain of the in-cylinder pressure sensor 18 can be estimated with high accuracy as described above. Further, when the offset is calculated (estimated), the estimation accuracy can be increased in the same manner as this gain.

  In steps S2 and S3 of FIG. 2, the gain and offset values of the in-cylinder pressure sensor 18 are calculated through the above processing. In the subsequent step S4, the in-cylinder pressure is corrected based on the gain value and the offset value calculated in steps S2 and S3 (corresponding to compensation for linearity deviation, gain deviation, etc.). Further, in the subsequent step S5, the ignition timing is calculated based on the in-cylinder pressure corrected in step S4 (arithmetic processing). In the subsequent step S6, the fuel injection timing in each cylinder of the engine 10 is corrected based on the calculation result in step S5. Specifically, an error in the ignition timing is obtained based on the ignition timing in the current combustion (current combustion cycle) calculated in step S5, and the next combustion (next combustion cycle) is performed to compensate for the error. The correction coefficient related to the fuel injection timing is updated. Then, the series of processes in FIG. 2 ends with the process in step S6.

  As described above, in the present embodiment, by repeating the series of processes in FIG. 2 described above, while correcting the sensor output of the in-cylinder pressure sensor 18, based on the sensor output after the correction, As a result, the ignition timing is controlled to a desired target value. At this time, by setting the angle θ2 at an appropriate timing by the processing of FIG. 3, the output characteristics (gain and offset) of the sensor 18 are calculated with higher accuracy as described above. (See FIG. 10). In addition, since the output characteristics of the sensor 18 are calculated with high accuracy in this way, the output correction based on the output characteristics is also performed with high accuracy.

  As described above, according to the output characteristic detection device and the output correction device for the in-cylinder pressure sensor according to the present embodiment, the following excellent effects can be obtained.

  (1) Applied to an engine 10 (internal combustion engine) that converts energy generated by combustion in a combustion chamber in each cylinder into mechanical motion (rotational motion), and combustion is performed for predetermined cylinders (all four) in the engine 10 The output characteristic of the in-cylinder pressure sensor 18 that detects the in-cylinder pressure that is the pressure of the chamber is detected. As such an in-cylinder pressure sensor output characteristic detection device, in-cylinder pressure is detected at two pressure detection timings (corresponding to angles θ1 and θ2), and the detected values of the two in-cylinder pressures (sensor values Ps1, Ps2) are detected. ) To estimate the gain and offset indicating the output characteristics of the in-cylinder pressure sensor 18 (output characteristics estimation means, steps S2 and S3 in FIG. 2), and the target ignition timing θign (which predicts the ignition timing of fuel combustion) And a program (timing setting means, step S1 in FIG. 2) for variably setting the angle θ2 (pressure detection timing) based on the reference parameter. In this way, the angle θ2 can be variably set based on the target ignition timing θign, and the output characteristics of the in-cylinder pressure sensor 18 can be detected with higher accuracy.

  (2) Since the angle θ2 is variably set based on the target ignition timing θign for predicting the ignition timing of fuel combustion, the angle θ2 can be set to an appropriate timing according to the ignition timing.

  (3) The ignition timing is controlled based on parameters relating to engine operating conditions (combustion conditions), more specifically, variable setting of the injection timing. By doing so, it becomes possible to easily and accurately control the ignition timing with respect to a desired target value.

  (4) The engine 10 is rotated by rotating the output shaft (crankshaft 10a) based on the energy of fuel combustion in the combustion chamber 20d, and changing the volume of the combustion chamber 20d according to the rotation of the output shaft. The mixture of fuel and air is compressed in the combustion chamber 20d, and the fuel is combusted using the compression. Further, the detection timing of the sensor values Ps1 and Ps2 is determined by the rotational angle position of the output shaft. As the detection timing (pressure detection timing), the volume of the combustion chamber 20d is the largest in the compression stroke. An angle θ1 (second timing) corresponding to the advance angle (faster) side than the reference angle (TDC), which is a smaller output shaft angle, and an angle corresponding to the advance angle side than the angle θ1 in the compression stroke. θ2 (first timing) was adopted. Then, by using (Equation 3) and (Equation 4), sensor output characteristics (gain and offset) are estimated based on the angles θ1 and θ2. This makes it possible to estimate the sensor output characteristics with high accuracy.

  (5) The program further includes a program (determination means, step S104 in FIG. 3) for determining whether or not the ignition timing for the earliest injection in one combustion cycle is later than TDC (reference angle). . In steps S104a and S104b in FIG. 3, the setting position of the angle θ2 is changed according to the determination result in step S104. More specifically, in step S104a, when it is determined in step S104 that the ignition timing is later than TDC, the angle θ2 is set near the advance side of TDC. In step S104b, when it is determined in step S104 that the ignition timing is not later (earlier) than TDC, the angle θ2 is set in the vicinity of the advance side of the ignition timing. In this way, when the ignition timing is later than TDC, the angle θ2 is set in the vicinity of the advance side of TDC, in other words, in the range where the in-cylinder pressure shows a polytropic change, and in the vicinity of the retard side boundary, The sensor output characteristic can be estimated more accurately. Further, even when the ignition timing is earlier than TDC, the angle θ2 is set in the vicinity of the advance side of the ignition timing, that is, in the range where the in-cylinder pressure exhibits a polytropic change, and is set in the vicinity of the retard side boundary. The output characteristic can be estimated more accurately.

  (6) In steps S2 and S3 in FIG. 2, the gain of the in-cylinder pressure sensor 18 and the in-cylinder pressure at the angle θ1 (sensor value Ps1) and the in-cylinder pressure at the angle θ2 (sensor value Ps2) The offset was estimated. Thereby, the estimation precision can be improved about both of these output characteristics. At this time, the degree of improvement in the estimation accuracy is particularly great when the gain estimation accuracy is increased.

  (7) The target sensor (cylinder pressure sensor 18) was a simple sensor. This makes it possible to reduce costs.

  (8) A program for detecting the degree of performance deterioration of the sensor 18 (for example, performance deterioration due to secular change) based on the output characteristics of the in-cylinder pressure sensor 18 estimated in steps S2 and S3 of FIG. 2 (step of FIG. 6) Step S18 and subsequent steps, step S28 and subsequent steps in FIG. 8) are provided. By doing so, it is possible to accurately detect whether or not the in-cylinder pressure sensor 18 is abnormal.

  (9) Further, as the output correction device for the in-cylinder pressure sensor, a program for correcting the sensor output of the in-cylinder pressure sensor 18 based on the output characteristics of the in-cylinder pressure sensor 18 estimated in steps S2 and S3 in FIG. (Correction means, step S4 in FIG. 2). By doing so, it becomes possible to correct (calibrate) the output characteristics of the in-cylinder pressure sensor 18 with higher accuracy.

  The above embodiment may be modified as follows.

  In the above embodiment, the angle θ2 is variably set based on the target ignition timing θign (reference parameter). However, the present invention is not limited to this, and a program for predicting the ignition timing based on the combustion state in the combustion chamber 20d (for example, the in-cylinder pressure waveform immediately before ignition) (prediction is sequentially executed by an ignition timing prediction means, for example, another routine not shown). The angle θ2 may be variably set based on the ignition timing (predicted value of the ignition timing) predicted by this program. Even in such a case, an effect equivalent to the effect of the above (2) can be obtained.

  In the above embodiment, the angle θ1 is a fixed value. However, this angle θ1 may be variably set together with the angle θ2. The angle θ1 is preferably set in the vicinity of the advance side boundary (in the initial stage of the compression stroke), for example, in a range where the in-cylinder pressure shows a polytropic change. Therefore, in this case, it is preferable to use not only a parameter for predicting the ignition timing of fuel combustion but also an arbitrary one (for example, engine state, operating condition, etc.) as a reference parameter.

  -It is also effective to include a program that stores the output characteristics and output errors (correction coefficients) measured at steps S1 to S4 in FIG. 2 in a predetermined storage device in association with engine operating conditions. It is. With such a configuration, the in-cylinder pressure stored in the storage device can be used without calculating the output characteristic of the in-cylinder pressure each time. As a storage device used here, a storage device that can be stored in a nonvolatile manner such as an EEPROM or a backup RAM is effective. With such a configuration, for example, even after the engine 10 is stopped (for example, the ignition switch is turned off) and the power supply to the device (ECU 70) is cut off, the data (in-cylinder pressure at each timing, etc.) is held in a nonvolatile manner. Thus, even when the engine is started next time, the above correction and the like can be performed based on the data at the previous engine start.

  The output characteristics and output errors (correction coefficients) from time to time measured in steps S1 to S4 in FIG. 2 are not used for fuel injection control, but are used only for data analysis by data accumulation, fault diagnosis, etc. You may do it.

  In the above embodiment, the intake port pressure during intake is used as the reference pressure (reference value for sensor value correction). However, the present invention is not limited to this. For example, engine design data such as the volume of the combustion chamber, The reference pressure may be calculated based on engine control conditions such as air-fuel ratio and engine coolant temperature.

  In the above embodiment, the fuel injection timing control is mentioned as an example, but the usage of the in-cylinder pressure sensor 18 is not limited to this. The in-cylinder pressure sensor 18 is also useful when used for controlling the air-fuel ratio, for example. In this case as well, the present invention can be applied basically in the same manner as the above embodiment.

  The target cylinder pressure sensor 18 is not limited to an inexpensive cylinder pressure sensor (simple sensor), but may be an expensive cylinder pressure sensor (general sensor).

  In addition, the type and system configuration of the engine to be controlled can be changed as appropriate according to the application. For example, the present invention can be applied not only to a compression ignition type diesel engine but also to a spark ignition type gasoline engine and the like, and is not limited to a reciprocating engine and can be applied to a rotary engine and the like. 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.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the outline of the engine control system to which each apparatus was applied about one Embodiment of the output characteristic detection apparatus and output correction apparatus of the in-cylinder pressure sensor which concern on this invention. The flowchart which shows the process sequence of fuel injection timing correction | amendment by said each apparatus. The flowchart which shows the process sequence about the setting process of the pressure detection timing used for calculation of the output characteristic of an object sensor. (A) is a graph showing the pressure characteristics when the ignition timing is earlier than TDC, and (b) is a graph showing the pressure characteristics when the ignition timing is later than TDC. (A) And (b) is a graph which shows the setting aspect of the said pressure detection timing about each of the case of single stage injection, and the case of two stage injection. The flowchart which shows the process sequence of the process which concerns on calculation of offset among the output characteristics of an object sensor. (A) And (b) is a graph which shows the calculation aspect of the offset. The flowchart which shows the process sequence of the process which concerns on calculation of a gain among the output characteristics of an object sensor. (A) And (b) is a graph which shows the calculation aspect of the same gain. The graph which shows the calculation aspect of the gain contrasted with a comparative example. (A) And (b) is a graph which shows the output characteristic of a simple sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 15 ... Injector, 18 ... In-cylinder pressure sensor, 20 ... Cylinder (cylinder), 20d ... Combustion chamber, 32 ... Intake pressure sensor, 45 ... DPF (Diesel Particulate Filter), 46 ... Differential pressure sensor, 70 ... ECU (Electronic control unit).

Claims (5)

A fuel injection means for injecting fuel into a combustion chamber in a cylinder; and applied to an engine that converts energy from combustion of the fuel in the combustion chamber into mechanical motion,
An apparatus for detecting an output characteristic of a target cylinder sensor for a cylinder pressure sensor that detects a cylinder pressure that is a pressure in a combustion chamber for a predetermined cylinder in the engine,
A plurality of pressure detection timings including a first timing on the advance side with respect to the compression top dead center at which the volume of the combustion chamber becomes the smallest in the compression stroke of the engine and a second timing on the advance side with respect to the first timing. Output characteristic estimation means for detecting the in-cylinder pressure and estimating at least one of a gain and an offset indicating the output characteristic of the target sensor based on the detected values of the plurality of in-cylinder pressures detected,
Timing setting means for variably setting the pressure detection timing based on a predetermined parameter for predicting the ignition timing of the fuel in the combustion chamber;
With
The fuel injection means performs the first fuel injection in which the ignition timing of the earliest injection in one combustion cycle is fuel injection slower than the compression top dead center, while the earliest injection in one combustion cycle The second fuel injection, which is a fuel injection whose ignition timing is earlier than the compression top dead center,
The timing setting means sets the timing immediately before the compression top dead center as the first timing when the first fuel injection is performed, and the first timing when the second fuel injection is performed. An output characteristic detection device for an in-cylinder pressure sensor, wherein the timing immediately before the ignition timing for the injection is set as the first timing. The ignition timing corresponding to the start timing of combustion in the combustion chamber is controlled to the target ignition timing,
The in-cylinder pressure sensor output characteristic detection device according to claim 1, wherein the predetermined parameter is a target ignition timing. Further comprising ignition timing prediction means for predicting the ignition timing based on the combustion state in the combustion chamber,
The in-cylinder pressure sensor output characteristic detection device according to claim 1, wherein the predetermined parameter is an ignition timing predicted by the ignition timing prediction means.   The output characteristic estimation means estimates the gain of the target sensor based on the in-cylinder pressure at the first timing and the in-cylinder pressure at the second timing. The output characteristic detection apparatus of the in-cylinder pressure sensor according to one item.   5. The sensor output of the target sensor is corrected based on the output characteristic of the target sensor estimated by the output characteristic estimation means in the output characteristic detection device of the in-cylinder pressure sensor according to any one of claims 1 to 4. An in-cylinder pressure sensor output correction apparatus comprising a correction means for applying

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