JP2015218690A - Internal combustion engine control device, internal combustion engine control method, and combustion pressure sensor signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy for determining parameters such as a pressure increase rate maximum value from the combustion pressure of a diesel engine.SOLUTION: Low-pass filtering with a cutoff frequency between 1.6 KHz and 6.0 KHz is performed on a signal received from a combustion pressure sensor that includes a pressure receiving unit receiving an internal pressure of a combustion chamber of an internal combustion engine and corresponding to a combustion pressure during operation of the internal combustion engine, and a pressure increase rate maximum value of the combustion pressure of the internal combustion engine or a heat generation rate maximum value computed from the combustion pressure is determined using the low-pass processed signal. The pressure increase rate maximum value or heat generation rate maximum value thus determined is used to control the operation of the internal combustion engine, particularly fuel injection timing.

Description

  The present invention relates to an internal combustion engine control device, a control method, and a signal processing device for a combustion pressure sensor.

  Conventionally, various attempts have been made to realize the desired control by detecting the operating state of the internal combustion engine. As one of the operating states, a signal related to the pressure in the combustion chamber of the internal combustion engine (hereinafter referred to as combustion pressure or in-cylinder pressure) may be used. This is because the combustion pressure of the internal combustion engine reflects the behavior of the combustion stroke of the internal combustion engine, and can be an important parameter in reducing, for example, combustion noise and knocking.

  Although the combustion pressure of an internal combustion engine can be handled as a parameter representing the combustion state, when a combustion pressure sensor is actually installed in the cylinder of the internal combustion engine, various vibration components are superimposed on the signal, making it difficult to handle as it is Met. For this reason, conventionally, what is used for control after performing various signal processing on the output of the combustion pressure sensor has been proposed (see Patent Document 1).

JP 2014-1700 A

  However, it is considered that how to handle the signal from the combustion pressure sensor differs depending on what kind of information relating to combustion of the internal combustion engine is extracted from such a combustion pressure signal and used for what kind of control. Conventionally, sufficient study has not been made on the handling of such signals. For example, in Patent Document 1, it is only determined whether the in-cylinder pressure signal is used as it is or an average value is used, and the use range of the obtained signal is limited.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one form of this invention, the control apparatus of an internal combustion engine is provided. The control device for an internal combustion engine includes a combustion pressure sensor having a pressure receiving portion that receives pressure in a combustion chamber of the internal combustion engine, a signal processing circuit that processes a signal from the combustion pressure sensor, and a process from the signal processing circuit A calculation unit that receives a completed signal and obtains the maximum value of the pressure increase rate of the combustion pressure of the internal combustion engine or the maximum value of the heat generation rate calculated from the combustion pressure; An operation control unit that controls the operation of the internal combustion engine using the maximum rate value. In the control device for the internal combustion engine, the signal processing circuit processes the signal from the combustion pressure sensor by a low-pass filter whose cut-off frequency is between 1.6 KHz and 6.0 KHz.

  Such a control device for an internal combustion engine processes a signal from the combustion pressure sensor by a low-pass filter whose cut-off frequency is between 1.6 KHz and 6.0 KHz. By performing such signal processing, the maximum pressure increase rate value or the maximum heat generation rate value can be obtained with high accuracy. When the maximum value of the rate of pressure increase or the maximum value of the heat generation rate is obtained based on the signal from the combustion pressure sensor, sufficient accuracy cannot be obtained only with a signal of less than 1.6 KHz. On the other hand, if a signal exceeding 6.0 KHz is included in the signal from the combustion pressure sensor, the accuracy for obtaining the maximum value of the pressure increase rate or the maximum value of the heat release rate decreases.

(2) In the control device for an internal combustion engine, the operation control unit may control the fuel injection timing of the internal combustion engine using the maximum pressure increase rate value or the maximum heat generation rate value. Since the maximum value of the pressure increase rate or the maximum value of the heat generation rate can be obtained with high accuracy, the fuel injection timing can be controlled appropriately.

(3) In the control device for an internal combustion engine, the internal combustion engine may be a diesel engine. This is because it may be desirable to use the maximum pressure increase rate or the maximum heat release rate in the control of the diesel engine.

(4) In the control device for an internal combustion engine, the operation control unit is configured to change the maximum pressure increase rate or the maximum heat generation rate in a transition state in which the combustion mode of the diesel engine is switched from the diffusion combustion mode to the premixed combustion mode. The fuel injection timing may be feedback controlled using the value. When transitioning from the diffusion combustion mode to the premixed combustion mode, the combustion state including the exhaust gas recirculation rate becomes unstable. By using the maximum pressure rise rate or the maximum heat release rate, the fuel at the transition time The injection timing can be accurately controlled.

(5) In the control device for an internal combustion engine, the combustion pressure sensor may be integrated into a glow plug provided in a cylinder of the diesel engine. If it carries out like this, a combustion pressure sensor and a glow plug can be efficiently arrange | positioned in the cylinder of a diesel engine.

  The present invention can be implemented in forms other than those described above. For example, the present invention can be implemented as a method for controlling the operation of an internal combustion engine or a device for processing a signal of a combustion pressure sensor.

(6) For example, a method for controlling the operation of the internal combustion engine of the present invention is provided. In this method, a signal corresponding to the combustion pressure during operation of the internal combustion engine is received from a combustion pressure sensor having a pressure receiving portion that receives the pressure in the combustion chamber of the internal combustion engine, and the signal received from the combustion pressure sensor is A low-pass filter process in which a cutoff frequency is between 1.6 KHz and 6.0 KHz is performed, and the maximum pressure increase rate of the combustion pressure of the internal combustion engine or the combustion pressure is determined using the low-pass filtered signal. The maximum value of the heat generation rate to be calculated is obtained, and the operation of the internal combustion engine is controlled using the obtained maximum pressure increase rate value or the maximum heat generation rate value.

(7) As another aspect of the present invention, a signal processing device for a combustion pressure sensor is provided. The signal processing device uses a signal from a combustion pressure sensor having a pressure receiving portion that receives a pressure in a combustion chamber of the internal combustion engine, using a maximum pressure increase rate or a maximum heat release rate obtained from the combustion pressure. It is good also as a signal processing device of a combustion pressure sensor output to a control device which controls fuel injection. This signal processing device subjects the signal from the combustion pressure sensor to low-pass filter processing with a cutoff frequency between 1.6 KHz and 6.0 KHz, and outputs it to the control device for the internal combustion engine.

  The present invention can be realized in various forms other than the apparatus. For example, the present invention can be realized in the form of a method for manufacturing a control device for an internal combustion engine, a computer program for realizing the control method for the internal combustion engine, a non-temporary recording medium on which the computer program is recorded, and the like.

The schematic block diagram of the control apparatus of the diesel engine as 1st Embodiment of this invention. The partial cross section figure which shows the structure of the glow plug with the built-in combustion pressure sensor used in 1st Embodiment. The block diagram which shows an example of the circuit structure which processes the signal from a combustion pressure sensor. The flowchart which shows the engine control routine in 1st Embodiment. The flowchart which shows the fuel injection timing control routine in 1st Embodiment. The graph which shows the relationship between the fuel-injection timing in a premixed combustion, and a pressure increase rate maximum value by using an EGR rate as a parameter. The graph which shows the example of control of 1st Embodiment along a combustion cycle. The graph which shows the control example of 1st Embodiment along time. The graph which shows the frequency characteristic of the signal from the combustion pressure sensor obtained through the low-pass filter. The graph which shows the relationship between real dPmax and calculation dPmax using the cut-off frequency of a low-pass filter as a parameter. The graph which shows the relationship between real dPmax and calculation dPmax, using the cut-off frequency of a low-pass filter as a parameter, by changing the operating conditions of the diesel engine. The graph which shows the relationship between the cutoff frequency and the correlation coefficient R of dPmax. The flowchart which shows the fuel injection timing control routine in 2nd Embodiment. The graph which shows the relationship between the fuel-injection time in MFC in premix combustion, and an EGR rate as a parameter. The graph which shows the example of control of 2nd Embodiment along a combustion cycle. The graph which shows the control example of 2nd Embodiment along time. The graph which shows the correlation with pressure rise rate maximum value dPmax and combustion noise.

  A diesel engine control apparatus according to a first embodiment of the present invention will be described below. These embodiments are realized by substantially the same hardware configuration. A diesel engine control device 200 includes a four-cylinder direct injection type diesel engine (hereinafter simply referred to as an engine) 10, an intake / exhaust system 20 that performs intake and exhaust including exhaust gas recirculation on the engine 10, and fuel ( The fuel injection valve 30 for supplying light oil), the ECU 70 for controlling the entire operation of the engine 10, and the like are mainly configured.

A. Engine controller hardware configuration:
The engine 10 is of a 4-cylinder type, and a piston is provided in each cylinder. The movement of the piston pushed down by the combustion of the fuel is converted into the rotational movement of the crankshaft through the connecting rod. A rotation angle sensor 54 is provided on the outer periphery of the gear wheel 11 coupled to the crankshaft, and accurately detects the rotation angle of the crankshaft (hereinafter referred to as crank angle CA). By devising the shape of the gear wheel, the top dead center TDC and the bottom dead center BDC of the piston in each cylinder are also detected.

  The cylinder head of the engine 10 is provided with the above-described fuel injection valve 30 and a glow plug 100 incorporating a combustion pressure sensor. In addition, the engine 10 is also provided with a water temperature sensor for detecting the cooling water temperature. The fuel injection valve 30 is opened in response to a command from the ECU 70 and injects high-pressure fuel supplied from the fuel supply pump 24 through the common rail 26 into the cylinder of the engine 10. The fuel injection timing represents the timing of this injection as a crank angle from the top dead center TDC. In general, in the diffusion combustion mode, fuel injection is performed near the top dead center TDC, and in the premix combustion mode, fuel injection is performed before the top dead center TDC. Advancing the fuel injection timing at the crank angle CA is referred to as controlling the advance side, and the opposite is referred to as controlling (retarding) the retard side.

  The glow plug 100 provided together with the fuel injection valve 30 incorporates a heater that reaches 900 degrees or more in a short time when energized, and is used for combustion assistance or combustion stabilization at low temperatures. The glow plug 100 incorporates a combustion pressure sensor. The detailed structure of the combustion pressure sensor will be described later with reference to FIG. The glow plug 100 employed in the present embodiment includes a ceramic heater in the heater portion, and in a shorter time than the metal heater (in the present embodiment, between 0.5 and 3.0 seconds), the temperature is 1200 degrees C. Reach. Even if the inside of the cylinder is a cooling environment by intake air, the glow plug 100 can heat the inside of the cylinder to about 1200 ° C. in a short time.

  Next, the intake / exhaust system 20 will be described. Oxygen is required for combustion of the engine 10, and this oxygen is covered by fresh air introduced from the outside. Fresh air is taken in from the intake pipe inlet 12 via an air filter (not shown), and taken into the intake / exhaust system 20 via the intake valve 14. The engine 10 sucks this fresh air and the exhaust gas circulated from the exhaust system by exhaust gas recirculation and uses it for combustion. What the engine 10 inhales is called “intake”. A state in which the intake air sucked into the cylinder is in a state where fuel is injected from the fuel injection valve 30 and mixed with the fuel is referred to as “air mixture”.

  In the intake / exhaust system 20, a turbocharger 15, an intercooler 17, an intercooler passage throttle valve 18, and an intake manifold (hereinafter simply referred to as a manifold) 21 are provided in sequence from the intake pipe inlet 12 to the intake port of the engine 10. It has been. On the other hand, ahead of the exhaust port of the engine 10, a branch pipe 33, an exhaust side turbine of the turbocharger 15, an oxidation catalyst 34, an exhaust filter (DPF) 36, and an exhaust shutter 38 are provided. Although not shown, the exhaust shutter 38 is provided with a known muffler and the like, and the exhaust gas is purified by the oxidation catalyst 34 and the DPF 36 and then released into the atmosphere.

  The passage is branched before the exhaust shutter 38, and a first EGR valve 37 is provided here. Since the branched passage is connected to a flow path for introducing fresh air from the intake pipe inlet 12, a part of the exhaust gas joins the fresh air here. The combined fresh air and exhaust gas are guided to the intake side passage of the turbocharger 15. The turbocharger 15 rotates an exhaust-side turbine disposed in an exhaust passage from the engine 10 by exhaust of the engine 10. Since the exhaust side turbine is directly connected to the intake side turbine disposed on the intake side, the intake side turbine rotates and supercharges the intake air to the engine 10. When supercharging by the turbocharger 15 is received, the temperature of the intake air rises due to adiabatic compression. The intercooler 17 is provided for cooling the intake air. Since the intake air (new air and exhaust gas) cooled by the intercooler 17 is sucked into the engine 10 via the manifold 21, the exhaust gas is recirculated. The amount of exhaust gas recirculated can be controlled by adjusting the opening of the first EGR valve 37. This passage is called a first EGR passage.

  On the other hand, the branch pipe 33 provided immediately after the exhaust port of the engine 10 is connected to the manifold 21 via the EGR cooler 35 and the second EGR valve 22. This pipe line is referred to as a second EGR passage that circulates exhaust gas from the exhaust side of the engine 10 to the intake side. By adjusting the opening degree of the intercooler passage throttle valve 18 provided immediately before the second EGR valve 22 and the manifold 21, the EGR amount can be controlled.

  The intake / exhaust system 20 described above is provided with a number of sensors. The manifold 21 includes an intake air temperature sensor 51 that detects the temperature of the intake air, an intake pressure sensor 52 that detects the intake pressure, and an oxygen concentration sensor 53 that detects the oxygen concentration of the intake air. Further, an exhaust temperature sensor 55 for detecting the exhaust temperature is provided downstream of the branch pipe 33, and an opacity sensor 57 for detecting the opacity of the exhaust (the amount of soot) is provided in front of the DPF 36. Further, a NOx sensor 59 that detects the amount of NOx is provided in front of the exhaust shutter 38. Among these sensors, the oxygen concentration sensor 53, the opacity sensor 57, the NOx sensor 59, and the like are provided for measuring the performance of the engine control device 200 described later, and are actually mounted on the vehicle. It is not always necessary to control the engine 10. Other sensors may be omitted as appropriate if they are not necessary for engine control. When various sensors such as a NOx sensor are not provided, the effect of the control device of the embodiment may be confirmed by measuring various parameters using an exhaust gas analyzer or an opacimeter in a bench test.

  The actuators such as the various sensors and valves are all connected to the ECU 70. The ECU 70 includes a CPU 71 for controlling, a ROM 72, a RAM 73, a CAN 74 for communicating with the in-vehicle LAN 90, an input port 75 for receiving signals from sensors, an output port 76 for outputting drive signals to various valves, each of these elements, A bus 78 for connecting ports is provided. Various sensors for detecting the driving state of the vehicle, such as an accelerator sensor 61 for detecting the amount of depression of the accelerator 62 (hereinafter referred to as an accelerator depression amount α) and a vehicle speed sensor 64 are also connected to the input port 75.

B. Combustion pressure sensor and glow plug structure with this:
A glow plug 100 incorporating a combustion pressure sensor, which is one of the sensors, will be described. FIG. 2 is a cross-sectional view showing the configuration of the glow plug 100 of the first embodiment. FIG. 2 shows the XYZ axes. The XYZ axes in FIG. 2 have an X axis, a Y axis, and a Z axis as three spatial axes orthogonal to each other. In the present embodiment, the X axis is an axis that is orthogonal to the axis SC of the glow plug 100 and that extends along the front and back direction of the paper surface. The + X-axis direction is a direction toward the back side of the paper surface, and the -X-axis direction is a direction toward the front side of the paper surface. The Y axis is an axis that is orthogonal to the axis SC of the glow plug 100 and extends in the left-right direction on the paper surface. The + Y axis direction is a direction toward the left side of the paper surface, and the -Y axis direction is a direction toward the right side of the paper surface. The Z axis is an axis along the axis SC of the glow plug 100. The + Z-axis direction is a direction toward the rear end side of the glow plug 100, and the -Z-axis direction is a direction toward the front end side.

  The glow plug 100 includes a ceramic heater 110 that generates heat. The glow plug 100 further includes a pressure sensor 360 that detects the pressure applied to the ceramic heater 110 and is configured to detect the pressure in the combustion chamber of the diesel engine 10.

  In addition to the ceramic heater 110 and the pressure sensor 360, the glow plug 100 includes an outer cylinder 210, a ring 260, an intermediate shaft 280, an elastic member 310, a sleeve 320, a diaphragm 340, a support member 380, a housing 500, A front cap 600, a protective cylinder 610, a connector member 620, a terminal spring 630, and a terminal member 640 are provided.

  The ceramic heater 110 of the glow plug 100 is a heating element made of a ceramic composition. The ceramic heater 110 includes a base 120 and a resistance heating element 140.

The base 120 of the ceramic heater 110 is an insulating ceramic made of an insulating ceramic material having electrical insulation. In the present embodiment, the main component of the base 120 is silicon nitride (Si ₃ N ₄ ). The base 120 has a rod shape extending from the front end side to the rear end side in the axial center SC direction. The base 120 contains a resistance heating element 140. The base 120 electrically insulates the resistance heating element 140 from the outside of the glow plug 100 and transmits heat of the resistance heating element 140 to the outside of the glow plug 100.

The resistance heating element 140 of the ceramic heater 110 is made of a conductive material. In the present embodiment, the resistance heating element 140 is mainly composed of a mixture of tungsten carbide (WC) and silicon nitride (Si ₃ N ₄ ). The resistance heating element 140 is embedded in the base body 120. The resistance heating element 140 generates heat when energized. The resistance heating element 140 has a linear shape folded at the tip side. The resistance heating element 140 includes a folded portion 141, a first linear portion 142, a second linear portion 144, a first terminal portion 146, and a second terminal portion 148.

  The folded portion 141 of the resistance heating element 140 is located on the distal end side of the resistance heating element 140 and forms a linear shape that is folded in an arc shape. The folded portion 141 connects the first linear portion 142 and the second linear portion 144.

  The first linear portion 142 of the resistance heating element 140 has a linear shape extending from the + Y-axis direction side to the rear end side of the folded portion 141. The second linear portion 144 of the resistance heating element 140 has a linear shape extending from the −Y axis direction side to the rear end side of the folded portion 141.

  The first terminal portion 146 of the resistance heating element 140 protrudes from the first linear portion 142 and is exposed on the surface of the base 120. The second terminal portion 148 of the resistance heating element 140 protrudes from the second linear portion 144 and is exposed on the surface of the base 120. In the present embodiment, the first terminal portion 146 is located on the distal end side with respect to the second terminal portion 148.

  The outer cylinder 210 of the glow plug 100 is a conductive metal body. In the present embodiment, the material of the outer cylinder 210 is stainless steel (for example, SUS410, SUS630, etc.). The outer cylinder 210 has a cylindrical shape extending about the axis SC. The ceramic heater 110 is fitted into the outer cylinder 210 by press-fitting with the ceramic heater 110 protruding from the front end side and the rear end side. In the present embodiment, the outer cylinder 210 is arranged over a range from the position on the tip side of the first terminal portion 146 in the ceramic heater 110 to between the first terminal portion 146 and the second terminal portion 148. ing. In the present embodiment, the outer cylinder 210 is electrically connected to the first terminal portion 146 by direct contact with the first terminal portion 146 of the ceramic heater 110. As a result, a conduction path to the first terminal portion 146 is configured via the outer cylinder 210.

  The ring 260 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the ring 260 is stainless steel (for example, SUS410, SUS630, etc.). The ring 260 has a cylindrical shape extending about the axis SC. The rear end side of the ceramic heater 110 is fitted into the front end side of the ring 260 by press-fitting. The front end side of the middle shaft 280 is fitted into the rear end side of the ring 260 by press-fitting. The ring 260 is electrically connected to the second terminal portion 148 of the ceramic heater 110 by direct contact. The ring 260 mechanically connects between the ceramic heater 110 and the center shaft 280 and electrically connects the second terminal portion 148 of the ceramic heater 110 and the center shaft 280.

  The middle shaft 280 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the middle shaft 280 is stainless steel (for example, SUS430). The middle shaft 280 has a cylindrical shape extending about the axis SC. The middle shaft 280 relays power supplied from the outside of the glow plug 100 to the second terminal portion 148 of the ceramic heater 110.

  The elastic member 310 of the glow plug 100 is a cylindrical metal body formed by molding a thin metal plate. In the present embodiment, the material of the elastic member 310 is stainless steel (for example, SUS316). In another embodiment, the material of the elastic member 310 may be a nickel alloy (eg, Inconel 718 (“INCONEL” is a registered trademark)). The elastic member 310 is joined to the outer cylinder 210 at the distal end side from the sleeve 320 and connects the outer cylinder 210 and the housing 500. In the present embodiment, the elastic member 310 is joined to the housing 500 via the support member 380. The elastic member 310 is elastically deformed so that the ceramic heater 110 can be displaced in the axial direction along the axis SC.

  The sleeve 320 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the sleeve 320 is stainless steel (for example, SUS410, SUS630, etc.). The sleeve 320 has a cylindrical shape extending about the axis SC. The sleeve 320 is joined to the outer cylinder 210 and extends to the rear end side from the ceramic heater 110. The sleeve 320 is joined to the outer cylinder 210 by welding at a joint portion (not shown). This joint is located on the tip side of the first terminal portion 146 of the ceramic heater 110. The joining may be realized by press fitting.

  The inside of the sleeve 320 is cylindrical and accommodates the outer cylinder 210. In the present embodiment, this cylindrical portion of the sleep 320 forms a slight gap with the outer cylinder 210 over the entire area facing the outer cylinder 210. The rear end side of the sleeve 320 is joined to the diaphragm 340. The sleeve 320 transmits the displacement of the ceramic heater 110 to the diaphragm 340.

  The diaphragm 340 of the glow plug 100 is a metal body having conductivity. In this embodiment, the material of the diaphragm 340 is stainless steel (for example, SUS410, SUS630, etc.). Diaphragm 340 has an annular shape centered on axis SC. A sleeve 320 is joined to the inner peripheral side of the diaphragm 340. A support member 380 is joined to the outer peripheral side of the diaphragm 340. The diaphragm 340 is elastically deformed according to the displacement of the ceramic heater 110 transmitted through the sleeve 320.

  The pressure sensor 360 of the glow plug 100 is joined to the diaphragm 340 and converts the displacement of the ceramic heater 110 transmitted to the diaphragm 340 by the sleeve 320 into an electric signal. The electric signal from the pressure sensor 360 indicates the pressure applied to the ceramic heater 110, that is, the pressure in the combustion chamber in the diesel engine 10. In the present embodiment, the pressure sensor 360 is configured using a piezoresistive element.

  The support member 380 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the support member 380 is stainless steel (for example, SUS410, SUS630, etc.). The support member 380 has a cylindrical shape extending about the axis SC. The rear end side of the support member 380 is joined to the diaphragm 340. The tip of the support member 380 is joined to the housing 500 by welding. In the present embodiment, the distal end side of the support member 380 is joined to the housing 500 and also joined to the elastic member 310 and the front cap 600.

  The housing 500 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the housing 500 is carbon steel. The material of the housing 500 may be stainless steel (for example, SUS303). The housing 500 accommodates a part of the ceramic heater 110, at least a part of the outer cylinder 210, and at least a part of the sleeve 320 in a state where the ceramic heater 110 protrudes from the tip side.

  The housing 500 includes a shaft hole 510, a tool engaging portion 520, and a screw portion 540. The shaft hole 510 is a through hole extending around the axis SC. An inner shaft 280 is positioned on the shaft center SC inside the shaft hole 510. The tool engaging portion 520 is configured to be engageable with a tool (not shown) used for attaching and detaching the glow plug 100 to the diesel engine 10. The glow plug 100 can be fixed to the diesel engine 10 by screwing the screw portion 540 with a female screw formed in the cylinder head of the diesel engine 10.

  The front cap 600 of the glow plug 100 is a cylindrical metal body having conductivity. In the present embodiment, the material of the front cap 600 is stainless steel (for example, SUS303). The front cap 600 is joined to the distal end portion of the housing 500 via the distal end of the support member 380. The front cap 600 accommodates the elastic member 310 therein.

  The protective cylinder 610 of the glow plug 100 is a metal body having conductivity. In this embodiment, the material of the protection cylinder 610 is stainless steel (for example, SUS410, SUS630, etc.). The protective cylinder 610 has a cylindrical shape extending about the axis SC. The protective cylinder 610 is joined to the rear end portion of the housing 500. A terminal member 640 is held inside the protective cylinder 610 via a connector member 620.

  The connector member 620 of the glow plug 100 is a member having electrical insulation. In the present embodiment, the material of the connector member 620 is an insulating resin. The connector member 620 has a cylindrical shape. A terminal member 640 is fixed inside the connector member 620.

  The terminal spring 630 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the terminal spring 630 is stainless steel (for example, SUS304). The terminal spring 630 mechanically and electrically connects the middle shaft 280 and the terminal member 640 and absorbs the displacement of the middle shaft 280 accompanying the displacement of the ceramic heater 110. In the present embodiment, the terminal spring 630 is a curved leaf spring.

  The terminal member 640 of the glow plug 100 is a metal body having conductivity. In the present embodiment, the material of the terminal member 640 is stainless steel (for example, SUS410, SUS630, etc.). The terminal member 640 receives power supplied from the outside of the glow plug 100. The electric power supplied to the terminal member 640 is supplied to the second terminal portion 148 of the ceramic heater 110 via the center shaft 280 and the ring 260. A signal line (not shown) for outputting a signal from the pressure sensor 360 to the outside is drawn to the outside via a signal terminal (not shown) and connected to the ECU 70 shown in FIG. The glow plug 100 incorporates an integrated circuit 166 (see FIG. 3), and a signal from the pressure sensor 360 is converted into a voltage signal corresponding to the pressure in the integrated circuit 166, as will be described later. Is output to the outside.

  In the glow plug 100 having such a structure, the ceramic heater 110 generates heat by energization through the terminal member 640, and the surface temperature reaches 1000 ° C. or more within a short period of time. As a result, the air-fuel mixture in the cylinder of the diesel engine to which the glow plug 100 is attached is heated. When the air-fuel mixture in the cylinder self-ignites and expands, the ceramic heater 110 is pressed by the pressure. When the ceramic heater 110 is pressed, the force is transmitted to the pressure sensor 360 via the sleeve 320 and detected as a combustion pressure. The resistance value of the pressure sensor 360 changes according to the combustion pressure, and the change in the resistance value is converted into an electrical signal corresponding to the combustion pressure by the integrated circuit 166. In general, a bridge circuit is used to extract a minute change in electric resistance as a large electric signal. A change in current flowing in the bridge caused by a change in the resistance value of the pressure sensor 360 is obtained via an amplifier circuit such as an operational amplifier. Extracted as a voltage signal. The voltage signal is taken out through a signal terminal. When the combustion stroke is completed and the intake stroke is reached, the pressure in the cylinder decreases, and the ceramic heater 110 no longer presses the pressure sensor 360, and the resistance value of the pressure sensor 360 changes in a direction to return to the original value. To do. A signal based on the resistance value of the pressure sensor 360 in such an intake stroke, or a noise component superimposed on the output of the pressure sensor 360 as a result of pressure fluctuation generated in the engine due to knocking or the like is also output to the outside as an electric signal from the pressure sensor 360. It is taken out. Therefore, the electric signal from the pressure sensor 360 includes a signal (noise) component other than the combustion pressure, but the pressure sensor 360 may be regarded as acting as a sensor for detecting the combustion pressure. Hereinafter, the pressure sensor 360 is also referred to as a combustion pressure sensor 360 as necessary.

C. Low-pass filter configuration and functions:
The change in resistance value of the pressure sensor 360 is converted into an electrical signal by the integrated circuit 166 connected to the pressure sensor 360 and input to the ECU 70 as shown in FIG. A low pass filter (LPF) 80 is provided in front of the input port 75 of the ECU 70, and the electric signal from the integrated circuit 166 is input to the input port 75 after high frequency components are removed here.

  The LPF 80 shown in FIG. 3 has a cutoff frequency of 3 KHz. The reason why the cut-off frequency is 3 kHz and the effect thereof will be described in detail later. The CPU 71 of the ECU 70 reads a signal from which a high frequency component of 3 kHz or higher is removed at high speed and processes it as a combustion pressure. The CPU 71 reads the electrical signal from the glow plug 100 in a predetermined repetition cycle, and handles the read value as the combustion pressure P [n]. [N] is a suffix indicating that the data is at the nth timing after the start of data reading (the initial value of n is 0). Therefore, [n-1] is the previous data, and [n-2] is the previous data (the previous data when viewed from the data of interest). Is shown. For the convenience of calculation, the calculation is started when the number of data is 3 or more (n ≧ 2). When n is less than 2, dP [n] is replaced by dP [2]. At the end of the cycle, data that does not exist as a data string is replaced with the value of the last data.

The CPU 71 obtains the pressure increase rate dP from the combustion pressure P based on the following equation (1).
dP [n] = {P [n-2] -8 ・ P [n-1] + 8P [n + 1] -P [n + 2]} / (12 ・ Ddeg) ・ ・ (1)
Here, Ddeg indicates the angular resolution of the crank angle that can be calculated based on the signal from the rotation angle sensor 54. The unit of the pressure increase rate obtained by the equation (1) is Pa / crank angle. Among the pressure increase rates dP [n] thus determined, the largest value is referred to as a pressure increase rate maximum value dPmax. The CPU 71 obtains the pressure increase rate maximum value dPmax for each combustion cycle for each cylinder.

D. First embodiment:
D-1) Engine control:
On the premise of the hardware configuration described above, the control device 200 of the first embodiment performs the processing shown in FIG. FIG. 4 is a flowchart showing an engine control routine. The ECU 70 repeatedly executes the process shown in FIG. 4 when the operation of the engine 10 is started. When processing of this routine is started, the ECU 70 first inputs signals from sensors such as the accelerator sensor 61 and the vehicle speed sensor 64, and reads the accelerator depression amount α, the vehicle speed V, and the like (step S100). Subsequently, it is determined whether or not the vehicle is in the premixed combustion mode based on the accelerator depression amount α and the vehicle speed V (step S110). Generally, the premixed combustion mode is employed in a low speed / low load region, and the diffusion combustion mode is selected in a region where the engine load is high. In which operating region the operation in the premixed combustion mode should be determined in advance and stored in the ROM 72 or the like in the form of a map.

  If it is determined that the region is to be operated in the premixed combustion mode (step S110: “YES”), it is next determined whether or not the region has been shifted from the region operated in the motoring or diffusion combustion mode (step S120). ). When a transition is made from a region that operates in motoring or diffusion combustion mode, the engine has been in motoring state until then, or has been operated in diffusion combustion mode, and the vehicle operation state has changed and the engine load has been premixed. It means that it has changed to the region that operates in the combustion mode. If it is determined that the engine is in such a transition state (step S120: “YES”), the fuel injection control using the pressure increase rate maximum value dPmax described above is performed (step S200). This control will be described in detail later.

  On the other hand, when the engine is not in a region where it operates in the premixed combustion mode as viewed from the vehicle operating state (step S110: “NO”), or even in a region where it operates in the premixed combustion mode, it is not in the transition state ( In step S120: “NO”), the process proceeds to step S300 and the control up to that point is continued. The previous control means that if the engine is operating in the diffusion combustion mode, the fuel injection control in the diffusion combustion mode is continued, and if it is operating in the premixed combustion mode, the premixed combustion mode is continued. This means that the fuel injection control is continued. The combustion in the diffusion combustion mode and the premixed combustion mode is conventionally known and will not be described in detail. Of course, there are various variations in the same diffusion combustion mode and premixed combustion mode, but any control can be applied except for the processing in step S200.

D-2) Fuel injection timing feedback control:
Next, the fuel injection control shown as step S200 will be described. FIG. 5 is a flowchart showing a fuel injection control routine executed as step S200. When this routine is started, data sampling from the combustion pressure sensor 360 built in the glow plug 100 is first performed (step S202). Actually, since the glow plug 100 and thus the combustion pressure sensor 360 are provided for each cylinder, the signal from the combustion pressure sensor 360 obtained for each cylinder is obtained after the high-frequency component is cut by the LPF 80. The input port 75 reads the combustion pressure P [n] at a predetermined interval. In step S202, a data string of in-cylinder pressure sampled at a predetermined interval is read for the cylinder in the combustion stroke.

  Next, a conversion process is performed on the read data string (step S204). Since the sampled data is data taken at a predetermined interval, it is read on the time axis. Therefore, the crank angle CA acquired from the rotation angle sensor 54 is used to convert this data into data on the crank angle. As will be described later, since the fuel injection timing is controlled based on the crank angle CA, the subsequent processing is performed based on the crank angle CA.

  Next, using the in-cylinder pressure data obtained based on the signal from the combustion pressure sensor 360 incorporated in the glow plug 100, zero pressure correction is performed (step S205). The signal from the combustion pressure sensor 360 includes an error such as a so-called zero point drift. Therefore, correction is performed from the crank angle CA so that when the piston is at the bottom dead center (BDC), the pressure in the cylinder is set to the reference value (0 point). By this processing, errors such as zero point drift and noise included in the signal can be removed.

  Subsequently, a combustion analysis process is performed (step S210). In this process, at least the combustion state necessary for obtaining the maximum pressure rise rate value dPmax of the in-cylinder pressure is analyzed. In the combustion analysis (step S210), various parameters relating to combustion, for example, may be obtained in addition to the analysis for obtaining the pressure increase rate maximum value dPmax of the in-cylinder pressure described later. For example, a maximum heat generation rate dQmax equivalent to the maximum pressure increase rate dPmax, a combustion mass ratio (MFB) described later, or a parameter for determining this may be obtained.

  Subsequently, a process for determining the fuel injection amount q and the EGR rate is performed (step S221). The fuel injection amount q is determined based on the required output to the engine, and is determined based on the intake pipe negative pressure, the accelerator depression amount α, and the vehicle speed V. Since the method for obtaining the fuel injection amount q is a well-known method, the description thereof is omitted here.

  The EGR rate is a ratio of exhaust gas recirculation performed in premixed combustion, and a ratio of exhaust gas to fresh air. In general, if the amount of oxygen in the intake air can be secured by supercharging using the turbocharger 15, NOx can be reduced as the EGR rate is higher. When the diffusion combustion mode is switched to the premixed combustion mode, the EGR rate is increased from the EGR rate (for example, about 25%) in the diffusion combustion mode to a maximum of, for example, about 80% within a relatively short time. Here, the amount of oxygen required for one cycle of the engine is calculated from the required torque in the premixed combustion mode, the fuel injection amount, etc., and this amount of oxygen can be sufficiently secured, so that the generation of soot can be suppressed. The maximum value of the rate is obtained from a map or the like.

  After obtaining the fuel injection amount q and the EGR rate in this way, a process of calculating the maximum value dPmax of the pressure increase rate of the in-cylinder pressure in one combustion cycle of one cylinder is performed based on the in-cylinder pressure data (step S222). . Since it is the pressure increase rate, it is not the absolute value of the pressure but the rate of increase per crank angle CA. Normally, the pressure increase rate becomes the largest value at the beginning of the combustion stroke, that is, the maximum value dPmax.

  Next, feedback control of the fuel injection timing based on the pressure increase rate maximum value dPmax is performed (step S223). Although it is feedback control, combustion in the engine 10 is not a continuous phenomenon but a discrete phenomenon consisting of four strokes of intake, compression, combustion, and exhaust for one cylinder. For this reason, the feedback control is performed in the form of determining the fuel injection timing in the next combustion cycle. The feedback control of the fuel injection timing is performed as follows.

  FIG. 6 is a graph in which the relationship between the fuel injection timing and the pressure increase rate maximum value dPmax is obtained using the EGR rate as a parameter. In the figure, for example, a graph described as “E50” indicates a relationship when the EGR rate is 50%. This graph shows the pressure rise rate maximum value dPmax obtained by changing the fuel injection timing little by little under the condition that the EGR rate is constant. In this example, when the EGR rate is low (55% or less), there is a relationship that the pressure increase rate maximum value dPmax decreases as the fuel injection timing is retarded (closer to the top dead center TDC). Recognize.

  Therefore, in step S223, the current EGR rate is estimated according to FIG. 6 from the fuel injection timing and the pressure increase rate maximum value dPmax for the cylinder that has just completed the combustion cycle, and the pressure increase in the next combustion cycle The fuel injection timing at which the rate maximum value dPmax is less than the predetermined value is obtained. For example, if the fuel injection timing in the premixed combustion mode in the cylinder that has just completed the combustion cycle is −14 [deg] and the maximum pressure increase rate dPmax is 1000 [kPa / deg] ( In FIG. 6, the combustion point A1), the EGR rate can be assumed to be about 50%. Therefore, in the next combustion cycle, it is understood that if the maximum pressure rise rate dPmax is controlled to about 500 [kPa / deg], the fuel injection timing should be about −6 [deg] (combustion point). A2). The feedback control of the fuel injection timing in step S223 is aimed at controlling the fuel injection timing so that the maximum pressure increase rate value dPmax is approximately between 300 and 500 [kPa / deg].

  Assuming that the maximum pressure increase rate dPmax is higher than the target range at the initial stage when transitioning to the premixed combustion mode, if the fuel injection timing is controlled to the retard side and the combustion cycle is repeated, the EGR rate will gradually increase. Therefore, the pressure increase rate maximum value dPmax gradually decreases. When the fuel injection timing is set to −6 [deg], as shown in FIG. 6, when the EGR rate increases to about 70%, the pressure increase rate maximum value dPmax becomes 200 [kPa / deg] or less ( Combustion point A2 → A3 → A4). In this case, since the pressure increase rate maximum value dPmax deviates from the lower limit of the target range, the fuel injection timing is advanced, and the pressure increase rate maximum value dPmax is increased (combustion point A4 → A5). This is the feedback control of the fuel injection timing by the pressure increase rate maximum value dPmax shown as step S223. In FIG. 6, since the data is measured by changing the EGR rate by 5%, the combustion points are also shown in a jumping manner. In actual combustion, the EGR rate, the pressure increase rate maximum value dPmax, the fuel injection timing, and the like take continuous values, and the combustion point is not limited to the control line with a different EGR rate shown in FIG.

D-3) Effects of the first embodiment:
A state of combustion when the fuel injection timing described above is controlled will be described with reference to FIGS. FIG. 7 is a graph showing the relationship between the pressure rise rate maximum value dPmax, the fuel injection timing, and the combustion noise with the horizontal axis as the combustion cycle. FIG. 8 is a graph showing the relationship between the amount of nitrided oxide (NOx) generated, the opacity OPACITY indicating the amount of soot generated, and the exhaust gas recirculation rate (EGR rate) with the horizontal axis as time. FIG. 7 illustrates the case where the diffusion combustion mode is switched to the premixed combustion mode around 50 cycles. Of the data shown in FIGS. 7 and 8, combustion noise was measured with a noise meter installed outside. Further, NOx was measured by a NOx sensor 59, and opacity (OPACITY) was measured by an opacity sensor 57. The EGR rate was calculated using the oxygen concentration measured by the oxygen concentration sensor 53. Since these sensors are arranged at various locations in the intake / exhaust system 20, there is a difference in the number of cycles and the time from when switching to the premixed combustion mode until the effect appears. 7 and 8, the deviation is corrected and shown.

  FIG. 7A shows a case where the fuel injection timing is feedback-controlled so that the pressure increase rate maximum value dPmax is within the target range according to the present embodiment, as a solid line JPI. A case where the feedback control of the fuel injection timing based on the maximum pressure increase rate dPmax is not performed is shown as a solid line JPP. When the feedback control of the fuel injection timing is not performed, the fuel injection timing is fixed to −14 [deg] as viewed from the top dead center TDC, as indicated by a solid line JFP in FIG. On the other hand, when the feedback control of the fuel injection timing based on the pressure increase rate maximum value dPmax is performed, the fuel injection timing is immediately reduced to a value with a small advance amount as shown by the solid line JFI. Be controlled.

  Thus, when switched to the premixed combustion mode, the EGR rate changes from about 25% to about 70% within a short period of time. This state is shown by solid lines JEI and JEP in FIG. Note that the increase in the EGR rate immediately after switching to the premixed combustion mode is caused by changing the opening degrees of the first EGR valve 37, the second EGR valve 22, and the intercooler passage throttle valve 18, as described above. The EGR rate gradually increases by switching each valve. It takes a predetermined time (at least several seconds) for the EGR rate to change to 70%. Furthermore, since the amount of oxygen remaining in the exhaust gas is reduced by performing the exhaust gas recirculation, the EGR rate gradually increases. The final EGR rate in the premixed combustion mode is, for example, about 80%.

  As described above, when the diffusion combustion mode (or motoring) is switched to the premixed combustion mode and the EGR rate is increased and the feedback control of the fuel injection timing based on the pressure increase rate maximum value dPmax is performed, FIG. As shown by the solid line JCI in FIG. In FIG. 7C, a solid line JCP represents combustion noise when the fuel injection timing feedback control is not performed. As shown in the figure, the combustion noise is reduced by about 10 [dB] by performing the feedback control of the fuel injection timing, compared with the case where the feedback control of the fuel injection timing is not performed.

  Further, by performing the feedback control of the fuel injection timing, it is possible to reduce the generation of NOx and soot as shown in FIGS. In FIG. 8A, the solid line JNI indicates the amount of NOx generated when the feedback control is performed, and the solid line JNP indicates the amount of NOx generated when the feedback control is not performed. It can be seen that the increase in NOx generation is suppressed for about 10 seconds after switching to the premixed combustion mode.

  In FIG. 8B, a solid line JOI indicates opacity when feedback control is performed (OPACITY), and a solid line JOP indicates opacity when feedback control is not performed. It can be seen that the opacity when switching to the premixed combustion mode is improved. Even when the fuel injection timing feedback control based on the pressure increase rate maximum value dPmax was performed, no torque reduction was observed.

D-4) Effects of the low-pass filter (LPF) 80:
The feedback control of the fuel injection timing based on the pressure increase rate maximum value dPmax described above is obtained by appropriately selecting the cutoff frequency of the LPF 80. This point will be described below.

In the present embodiment, the cutoff frequency of the LPF 80 is 3 KHz. This means that the pressure rise rate maximum value dPmax is obtained from a signal obtained by removing a high frequency component of 3 KHz or more from the electric signal obtained from the combustion pressure sensor 360 via the integrated circuit 166. . An example of an electrical signal actually obtained from the combustion pressure sensor 360 is shown in FIG. In the figure, graphs A1 to A6 show power spectra obtained under different conditions of the load of the diesel engine. Conditions A1 to A6 were as follows.
Condition A1: Engine speed 1000 rpm, output torque 24 N · m
Condition A2: engine speed 1000 rpm, output torque 47 N · m
Condition A3: engine speed 1000 rpm, output torque 94 N · m
Condition A4: engine speed 1000 rpm, output torque 76 N · m
Condition A5: engine speed 1000 rpm, output torque 153 N · m
Condition A6: engine speed 1000 rpm, output torque 156 N · m

  According to FIG. 9, it can be seen that the electrical signal from the combustion pressure sensor 360 includes a wide range of frequency components. Of these, most signals in the high-frequency region are considered to be noise caused by engine vibration or knocking. In order to obtain the maximum pressure rise rate value dPmax of the diesel engine 10, a signal having a frequency component up to 1 KHz has been processed so far. This is because if the high-frequency component is captured and processed, the calculation accuracy of the pressure increase rate maximum value dPmax is considered to be reduced due to noise included in the electrical signal from the combustion pressure sensor 360.

  However, the inventors have found that when the cutoff frequency of the LPF 80 is set to a predetermined frequency, the calculation accuracy of the pressure increase rate maximum value dPmax is significantly increased. Actually, the pressure rise rate maximum value dPmax shown in FIG. 6 is obtained using an LPF 80 having a cutoff frequency of 3 KHz, and FIGS. 7 and 8 control the diesel engine 10 using the LPF 80. Each characteristic is shown. When the cut-off frequency of the LPF 80 is set to 1 KHz, the error of the pressure increase rate maximum value dPmax becomes large, and an error also occurs in the control of the fuel injection timing.

  FIG. 10 is a graph showing the relationship between the cutoff frequency of the LPF 80 and the calculation accuracy of the pressure increase rate maximum value dPmax. This graph was obtained as follows. A combustion pressure sensor for measurement (manufactured by Kistler, in-cylinder pressure sensor using a polystable quartz element) was attached to the diesel engine 10 shown in FIG. 1, and its output was connected to a combustion pressure measuring device. This combination of the combustion pressure sensor and the combustion pressure measuring device constitutes a dedicated device for accurately measuring the combustion pressure, and the actual pressure increase rate maximum value dPmax of the diesel engine 10 (actually indicated on the horizontal axis of FIG. 10). dPmax) has an accuracy that can be regarded as being measured.

  At the same time, the pressure increase rate maximum value dPmax was calculated in the ECU 70 from the combustion pressure read through the LPF 80 using the combustion pressure sensor 360 incorporated in the glow plug 100. The calculated value dPmax is plotted on the vertical axis of FIG. 10, and the value of the calculated dPmax at that time is plotted in FIG. 10 with respect to the actual dPmax obtained by a dedicated combustion pressure measuring device. In FIG. 10, “Δ” indicates data when the cutoff frequency of the LPF 80 is 3 KHz (condition B1), and “◇” indicates data when the cutoff frequency is 1 KHz (condition B2). FIG. 10 also shows regression lines RV1 and RV2 obtained by using the method of least squares based on the data of each condition.

The square of the correlation coefficient (R ² : contribution rate) of the data in the case of the regression line RV1 shown in FIG. 10 was 0.9933 in the condition B1, whereas it was 0.7725 in the condition B2. It was. In other words, the actual dPmax and the calculated dPmax showed a very high correlation under the condition B1 (cutoff frequency 3 KHz), whereas the correlation decreased considerably under the condition B2 (cutoff frequency 1 KHz). In addition, the slope of the regression line has a coefficient of 0.96 under the condition B1, and the actual dPmax and the calculated dPmax have a substantially one-to-one relationship, whereas under the condition B2, the coefficient is 0. Therefore, it cannot be said that there is a sufficient correspondence between the actual dPmax and the calculation dPmax.

The inventors made similar measurements by changing the operating conditions of the diesel engine 10 in order to examine what frequency components are dominant from the graph shown in FIG. The results are shown in FIG. FIG. 11 is a plot of the relationship between the actual dPmax and the calculated dPmax under the condition C1 and the conditions D1 to D6. The operating conditions of the engine are as follows. Note that the cut-off frequency of the LPF 80 was 3 KHz in the condition C1, and 1 KHz in the conditions D1 to D6.
Engine operating conditions:
Condition C1: engine output torque 24 Nm, symbol Δ in the figure
Condition D1: Engine output torque 24 Nm, symbol in the figure ◇
Condition D2: Engine output torque 47 Nm, symbol □ in the figure
Condition D3: engine output torque 94 Nm, symbol x in the figure
Condition D4: engine output torque 76 Nm, symbol in the figure *
Condition D5: engine output torque 153 Nm, symbol in the figure ○
Condition D6: engine output torque 156 Nm, sign + in the figure

In FIG. 11, a straight line RV3 is a regression line obtained in the same manner as in FIG. 10 based on the data under the condition C1. The straight line RV4 is a regression line obtained in the same manner based on the data of the conditions D1, D3, and D4 (in the figure, ◇, x, *). The data in the range indicated by the area ad56 in FIG. 11 (symbols ◯, +) is the data under the conditions D5 and D6. At first glance, the actual dPmax and the calculation dPmax are the same as when the cutoff frequency is 3 kHz Although it seems to show a correlation, in reality, not only the square of the correlation coefficient (R ² : contribution rate) is small, but also the slope of the regression line becomes a small value, and a one-to-one relationship is established between the two. I understand that there is no. Further, the data under the condition D2 is distributed in a region that does not overlap with other data, as shown as a region ad2 in FIG. That is, when the cut-off frequency of the LPF 80 is 1 KHz, the correlation between the actual dPmax and the calculated dPmax changes depending on the operating conditions of the diesel engine 10. For this reason, it was found that in order to appropriately obtain the actual pressure increase rate maximum value dPmax, data in a band exceeding at least 1 KHz is required. Therefore, the inventors further changed the cut-off frequency of the LPF 80 to obtain the actual dPmax and the calculated dPmax, and examined what value the correlation coefficient of the two takes. The result is shown in FIG.

  In FIG. 12, the horizontal axis represents the cut-off frequency of the LPF 80, and the vertical axis represents the correlation coefficient R between the actual dPmax and the calculated dPmax. As can be seen from the figure, the correlation coefficient R shows a high value when the cut-off frequency is 1.6 KHz or higher, whereas it rapidly deteriorates when the cut-off frequency falls below 1.6 KHz. In particular, in the range GL where the cut-off frequency is 1.6 KHz to 6.0 KHz, the correlation coefficient R showed a high value exceeding 0.95. When the cut-off frequency exceeds 6 KHz, the correlation coefficient R gradually decreases. This is considered to be due to noise components such as knocking generated in the diesel engine 10 and harmonics generated from engine vibration. Since such noise cannot be completely removed by actual engine control, setting the cut-off frequency to 1.6 to 6.0 KHz is effective in actual diesel engine control. As can be seen from FIG. 12, the correlation coefficient when the cut-off frequency of the low-pass filter 80 is between 2.8 and 5.0 KHz is extremely high, and the cut-off frequency is particularly preferably set to a value therebetween. preferable.

  According to the diesel engine control apparatus 200 of the present embodiment, in addition to the above effects or separately from the above effects, the configuration for accurately detecting the pressure increase rate maximum value dPmax can be simplified. This can contribute to cost reduction and resource saving, and can facilitate the manufacture of the control device. Further, since the maximum value of the pressure increase rate or the maximum value of the heat generation rate can be obtained with high accuracy, it is easy to facilitate control design using these parameters and improve the degree of freedom in control.

E. Second embodiment:
E-1) Feedback control of fuel injection timing:
In the second embodiment, the same hardware configuration as that of the first embodiment is used, and only the feedback control of the fuel injection timing is different. Details of the feedback control of the fuel injection timing in the second embodiment are shown in FIG. Since the control routine shown in FIG. 13 is the same as that of the first embodiment up to step S222 of the control routine shown in FIG. 5, the first half of the control routine is not shown.

  In the second embodiment, after calculating the pressure increase rate maximum value dPmax in step S222, it is determined whether or not the control range based on the pressure increase rate maximum value dPmax is exceeded (step S230). The pressure increase rate maximum value dPmax is calculated based on data read through the LPF 80 having a cutoff frequency of 3 KHz, as in the first embodiment. The fuel injection timing controlled to the top dead center TDC side by feedback control of the fuel injection timing based on the calculated pressure increase rate maximum value dPmax is controlled to the advance side as the pressure increase rate maximum value dPmax decreases, If the angle is advanced by more than −14 [deg], it is determined that the control range has been exceeded.

If the determination in step S230 is “NO”, it is determined that the pressure is within the control range based on the maximum pressure increase rate value dPmax, and the fuel injection timing feedback control based on the maximum pressure increase rate value dPmax is performed as in the first embodiment. (Step S223). On the other hand, if the determination in step S230 is “YES”, that is, if it is determined that the control range at the pressure increase rate maximum value dPmax has been exceeded, processing for calculating the combustion mass ratio (MFB) is performed (step S231). The combustion mass ratio (MFB) indicates the ratio of the heat generation Qca up to a certain crank angle ca to the maximum heat generation Qmax in one combustion cycle. That means
MFBca = 100 · Qca / Qmax
It is. In 2nd Embodiment, MFB30 which is a ratio to a crank angle of 30 degree | times was used as a combustion mass ratio (MFB). The combustion mass ratio (MFB) is also calculated using a signal from the combustion pressure sensor 360, and the value can also be obtained with high accuracy by setting the cutoff frequency of the LPF 80 to 3 KHz.

  FIG. 14 shows the relationship between the fuel injection timing and the MFB 30 using the EGR rate as a parameter. As shown in the figure, the MFB 30 has a monotonically increasing relationship with the fuel injection timing over a wide range where the crank angle ca is −22 degrees or more. Moreover, this trend is even clearer at high EGR rates. Therefore, when MFB30 is calculated, feedback control of fuel injection timing is performed using this MFB30 (step S232). Thereafter, the process goes to “NEXT” and the present control routine is terminated.

  According to the engine control apparatus of the second embodiment described above, when switching to the combustion in the premixed combustion mode with the control for increasing the EGR rate, the pressure rise rate maximum value dPmax is accurately obtained, and the fuel obtained thereby Shifts to injection timing feedback control. Thereafter, after the EGR rate is increased and the fuel injection timing is advanced to about −14 [deg], the control is switched to the feedback control of the fuel injection timing by the MFB 30. When the EGR rate increases, the fuel injection timing is controlled to advance by controlling the fuel injection timing so as to keep the pressure increase rate maximum value dPmax constant. Thereafter, when the EGR rate (intake oxygen concentration) converges to a constant value, the change in the maximum pressure increase rate dPmax when the fuel injection timing is controlled becomes relatively small. On the other hand, in this region, the MFB 30 has sufficient sensitivity to changes in the fuel injection timing. Therefore, in this region, by performing feedback control of the fuel injection timing using the MFB 30, premixed combustion with better thermal efficiency can be performed.

E-2) Effects of the second embodiment:
Examples of control in the second embodiment are shown in FIGS. As in the first embodiment, each figure shows changes in the pressure rise rate maximum value dPmax, fuel injection timing, combustion noise, NOx generation amount, opacity, and EGR rate when switched to the premixed combustion mode. . FIG. 16B shows THC, which is the total amount of unburned hydrocarbons. Also, among the solid lines in each figure, those with the suffix I indicate the characteristics in the second embodiment, and those with the suffix P indicate the characteristics in the first embodiment.

  As shown in FIG. 15B, in the vicinity of 220 cycles, the control is switched from the control based on the maximum pressure increase rate dPmax to the control based on the MFB 30. As a result, it can be seen that the fuel injection timing can be controlled to the advance side as compared with the case where the control with the maximum pressure increase rate dPmax is continued (solid line KFP). It can also be seen that THC is improved. Note that no significant differences were observed in combustion noise, NOx, opacity, and the like as compared to the first embodiment.

  Therefore, according to the engine control apparatus of the second embodiment, the maximum pressure increase rate dPmax can be accurately obtained, and the fuel injection timing can be effectively controlled during the transition to the premixed combustion mode. In addition to the same effects as in the first embodiment, there is an excellent effect that THC can be further improved. Further, the fuel injection timing can be further controlled to the advance side as compared with the first embodiment.

F. Variation:
F-1) Modification 1:
In each of the above embodiments, the cutoff frequency of the LPF 80 is 3 KHz. However, as shown in FIG. 12, the cutoff frequency of the LPF 80 can be appropriately selected as long as it is between 1.6 KHz and 6.0 KHz. . If vibration noise such as knocking can be reduced, the cut-off frequency can be set to a higher value. Further, the low pass filter (LPF) 80 may be provided in the integrated circuit 166 instead of being provided in the ECU 70. Moreover, it is good also as what is provided in the input port 75 in ECU70. Furthermore, instead of the configuration of the low-pass filter having a discrete circuit configuration, a similar low-pass filter may be configured by a method in which the CPU 71 takes a moving average of data by software. It is also possible to provide a lower limit and an upper limit for the cutoff frequency, and to configure the low-pass filter as a band-pass filter. As described above, the upper limit of the cut-off frequency is between 1.6 KHz and 6.0 KHz, the lower limit is set to 0.1 KHz, etc., and the frequency components in the region unnecessary for calculation such as the maximum pressure increase rate dPmax are excluded. It is good as a thing.

F-2) Modification 2:
In each of the above embodiments, the glow plug 100 may be energized when transitioning to the premixed combustion mode. When switching to the premixed combustion mode, energizing the glow plug 100 to heat the glow plug 100 to about 1000 ° C. or more (preferably 1300 ° C.) confirms that the cycle fluctuation of the diesel engine 10 is reduced. It was. Compared with the case where the glow plug 100 is not energized, the torque increases when the glow plug 100 is energized, and the cycle fluctuation of the torque is suppressed. For this reason, in order to realize the same torque and cycle fluctuation of the same torque, the control range of the fuel injection timing can be expanded somewhat (for example, about 1 CA [deg]) to the retard side. In the premixed combustion mode, if the fuel injection timing can be controlled to the retard side by 1 CA [deg], combustion noise, NOx, THC, and opacity can be reduced.

F-3) Modification 3:
In each of the above embodiments, the pressure increase rate maximum value dPmax is used as a parameter related to the in-cylinder pressure, but other parameters may be used. For example, the maximum heat generation rate dQmax may be used. The heat generation rate dQ corresponds to the amount of heat generated for each predetermined crank angle CA, and can be obtained by calculating from the measured in-cylinder pressure P for each predetermined crank angle CA. Among the heat generation rates dQ, the largest value in the combustion cycle is called the heat generation rate maximum value dQmax. The maximum heat release rate value dQmax is a parameter that has a strong correlation with the maximum pressure increase rate value dPmax. Therefore, even if the heat release rate maximum value dQmax is used, the same fuel injection timing control as in the first and second embodiments is performed. can do.

  In addition, a heat generation amount Q or the like can also be used. By calculating these values and performing feedback control of the fuel injection timing so that the value falls within a predetermined target range, at least one of combustion noise, NOx, and opacity can be improved.

F-4) Modification 4:
In the above embodiment, the in-cylinder pressure is measured by the glow plug 100 including the combustion pressure sensor 360. However, the combustion pressure sensor 360 may be provided independently of the glow plug 100. In this case, the arrangement of the combustion pressure sensor 360 can be freely set.

F-5) Modification 5:
In the above embodiment, the feedback control of the fuel injection timing is based on the control characteristics shown in FIGS. 6 and 14, and the pressure rise rate maximum value dPmax is set within a predetermined range (for example, a range of 400 to 800 kPa / deg). I did it. On the other hand, an upper limit value (for example, 800 kPa / deg) of the maximum pressure increase rate value dPmax is determined, and when the maximum pressure increase rate value dPmax exceeds the upper limit value, the fuel injection timing is set to a predetermined crank angle CA (for example, The fuel injection timing may be feedback-controlled by a method of controlling to the retard side by 2 CAdeg) and controlling to the advance side by a predetermined crank angle CA (for example, 1 CAdeg) if it is below the upper limit. . According to this method, the fuel injection timing can be controlled by a simple determination that merely compares the pressure increase rate maximum value dPmax with the upper limit value. The upper limit value may be provided with a hysteresis having a predetermined width.

F-6) Modification 6:
In the above embodiment, the combustion pressure sensor 360 is provided in the glow plug 100 provided for each cylinder. However, in the case of a multi-cylinder engine, it is not always necessary to provide the combustion pressure sensor in all cylinders. Alternatively, a combustion pressure sensor may be provided for only one cylinder or only two cylinders. The in-cylinder pressure or the pressure increase rate maximum value dPmax of the cylinder not provided with the combustion pressure sensor may be estimated using the values obtained for the other cylinders. Alternatively, the fuel injection timing of the cylinder not provided with the combustion pressure sensor may be controlled following the fuel injection timing of the cylinder provided with the combustion pressure sensor.

F-7) Modification 7:
In the above embodiment, the fuel injection timing feedback control is to control the fuel injection timing of the next combustion cycle of the cylinder using the pressure rise rate maximum value dPmax and the heat generation rate maximum value dQmax of the focused cylinder. However, it may be used not for the next combustion cycle of the same cylinder but for feedback control of the fuel injection timing of another cylinder, for example, the cylinder that performs the next fuel injection. If the calculation of the fuel injection timing is not in time, it may be applied to the next combustion cycle. Note that the control of the fuel injection timing using the pressure rise rate maximum value dPmax or the like is not necessarily limited to the feedback control, and general PID control can be applied, and the reproducibility of the change of the parameter with respect to the change of the fuel injection timing can be sufficiently obtained. In some cases, open control may be used.

F-8) Modification 8:
In the above embodiment, the fuel injection timing is controlled by the maximum pressure increase rate or the maximum heat generation rate. However, the maximum pressure increase rate or the maximum heat generation rate obtained using the low-pass filter of the present invention is used. Other operating states of the internal combustion engine such as a diesel engine, for example, combustion noise, may be controlled. FIG. 17 is a graph showing the relationship between the calculation dPmax obtained by the ECU 70 and the combustion noise in the above embodiment. The calculation dPmax in the figure is the maximum pressure increase rate obtained from the signal of the pressure sensor 360 obtained through a low-pass filter with a cutoff frequency of 3 KHz. As shown in the figure, the calculation dPmax and the combustion noise showed a strong correlation. Therefore, the actual combustion noise of the diesel engine 10 can be known by obtaining the calculation dPmax. For this reason, if the calculation dPmax is controlled while satisfying the required output for the diesel engine 10, combustion noise can be reduced. Such control can be performed not only when operating in the premixed combustion mode but also when operating in the diffusion combustion mode. Of course, it can also be carried out during the transition between both combustion modes.

  The cut-off frequency of the low-pass filter 80 when performing such combustion noise control may be in the range of 1.6 KHz to 6.0 KHz, more preferably 2.8 KHz to 5.0 KHz, as in the above-described embodiment. . When a low-pass filter having a cutoff frequency of 1 KHz was used, a sufficient correlation could not be obtained between the calculation dPmax and the combustion noise, and the combustion noise could not be controlled by the calculation dPmax.

F-9) Other variations:
In the above embodiment, the glow plug 100 uses a ceramic heater, but a metal heater may be used.
In addition to the diesel engine control device 200 and the control method as in the above embodiment, the present invention can be implemented as an independent processing device that processes signals from the combustion pressure sensor 360.
The diesel engine is not limited to four cylinders and may have any number of cylinders. For example, it may be a single cylinder or a multi-cylinder configuration such as 6 cylinders.
In the above embodiment, the target range for feedback control of the pressure rise rate maximum value dPmax is determined so that at least one of combustion noise, NOx, and opacity is improved. However, other parameters such as carbon monoxide CO are used. The target range may be determined so as to reduce the parameter.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Diesel engine 11 ... Gear wheel 12 ... Intake pipe 14 ... Intake pulp 15 ... Turbocharger 17 ... Intercooler 18 ... Intercooler passage throttle valve 20 ... Intake / exhaust system 21 ... Manifold 22 ... Second EGR valve 24 ... Fuel supply pump 26 ... Common rail 30 ... Fuel injection valve 33 ... Branch pipe 34 ... Oxidation catalyst 36 ... DPF
37 ... 1st EGR valve 38 ... Exhaust shutter 51 ... Intake temperature sensor 52 ... Intake pressure sensor 53 ... Oxygen concentration sensor 55 ... Exhaust temperature sensor 57 ... Opacity sensor 59 ... NOx sensor 61 ... Anxel sensor 62 ... Accelerator 64 ... Vehicle speed sensor 70 ... ECU
71 ... CPU
72 ... ROM
73 ... RAM
74 ... CAN
75 ... Input port 76 ... Output port 80 ... Low pass filter 90 ... In-vehicle LAN
DESCRIPTION OF SYMBOLS 100 ... Glow plug 110 ... Ceramic heater 120 ... Base | substrate 140 ... Resistance heating element 141 ... Folding part 142 ... 1st linear part 144 ... 2nd linear part 146 ... 1st terminal part 148 ... 2nd terminal part DESCRIPTION OF SYMBOLS 166 ... Integrated circuit 200 ... Control apparatus of diesel engine 210 ... Outer cylinder 260 ... Ring 280 ... Middle shaft 310 ... Elastic member 320 ... Sleeve 340 ... Diaphragm 360 ... Pressure sensor (combustion pressure sensor)
380: Support member 500 ... Housing 510 ... Shaft hole 520 ... Tool engaging portion 540 ... Screw portion 600 ... Front cap 610 ... Protection cylinder 620 ... Connector member 630 ... Terminal spring 640 ... Terminal member

Claims (8)

A combustion pressure sensor having a pressure receiving portion for receiving the pressure in the combustion chamber of the internal combustion engine;
A signal processing circuit for processing a signal from the combustion pressure sensor;
A calculation unit that receives the processed signal from the signal processing circuit and obtains the maximum pressure increase rate of the combustion pressure of the internal combustion engine or the maximum heat release rate calculated from the combustion pressure;
An internal combustion engine control device comprising: an operation control unit that controls the operation of the internal combustion engine using the maximum pressure increase rate value or the maximum heat generation rate value obtained;
The control apparatus for an internal combustion engine, wherein the signal processing circuit processes a signal from the combustion pressure sensor by a low-pass filter whose cutoff frequency is between 1.6 KHz and 6.0 KHz.   The control device for an internal combustion engine according to claim 1, wherein the operation control unit controls fuel injection timing of the internal combustion engine using the maximum value of the pressure increase rate or the maximum value of the heat generation rate.   3. The control device for an internal combustion engine according to claim 1, wherein the internal combustion engine is a diesel engine.   The operation control unit performs feedback control of fuel injection timing using the maximum pressure increase rate or the maximum heat generation rate in a transition state in which the combustion mode of the diesel engine is switched from the diffusion combustion mode to the premixed combustion mode. The control apparatus for an internal combustion engine according to claim 3.   The control apparatus for an internal combustion engine according to claim 3 or 4, wherein the combustion pressure sensor is integrally incorporated in a glow plug provided in a cylinder of the diesel engine.   The control device for an internal combustion engine according to any one of claims 1 to 5, wherein a cutoff frequency of the low-pass filter is 2.8 KHz to 5.0 KHz. A method for controlling the operation of an internal combustion engine comprising:
A signal corresponding to the combustion pressure during operation of the internal combustion engine is received from a combustion pressure sensor having a pressure receiving portion that receives the pressure in the combustion chamber of the internal combustion engine,
The signal received from the combustion pressure sensor is subjected to low-pass filter processing with a cutoff frequency between 1.6 KHz and 6.0 KHz,
Using the low-pass filtered signal, obtain the maximum pressure increase rate of the combustion pressure of the internal combustion engine or the maximum heat generation rate calculated from the combustion pressure,
An operation control method for an internal combustion engine, wherein operation of the internal combustion engine is controlled using the maximum value of the pressure increase rate or the maximum heat generation rate that is obtained. Fuel injection of the internal combustion engine is controlled by using a signal from a combustion pressure sensor having a pressure receiving portion for receiving the pressure in the combustion chamber of the internal combustion engine, using a maximum pressure increase rate or a maximum heat release rate obtained from the combustion pressure A signal processing device for a combustion pressure sensor that outputs to a control device,
A signal processing device for a combustion pressure sensor, which outputs a signal from the combustion pressure sensor to a control device of the internal combustion engine by subjecting the signal from the combustion pressure sensor to low-pass filtering with a cutoff frequency between 1.6 KHz and 6.0 KHz.

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