JP2013024154A - Control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in combustion stability of a diesel engine 1, after a manual transmission 73 is shifted up.SOLUTION: Before the engine 1 is completely warmed up, a fuel injection valve (an injector 18) executes main injection, in which fuel injection is started at a compression top dead center or earlier for main combustion, mainly diffusive combustion, and pre-stage injection, in which at least one fuel injection is executed earlier than the main injection so that pre-stage combustion occurs before the start of main combustion. EGR means (an exhaust gas recirculation passage 50, an exhaust gas recirculation valve 51a, and a cooler bypass valve 53a) recirculates exhaust of an EGR amount corresponding to the operation state of the engine. The EGR means maintain an EGR amount of immediately before the shift-up process, during the shift-up process of the transmission 73 including fully closing an accelerator and releasing a clutch (a clutch mechanism 72).

Description

  The technology disclosed herein relates to a control device for a diesel engine.

  In a diesel engine mounted on an automobile, in order to improve emission performance, reduce noise or vibration, improve fuel consumption and torque, etc., fuel may be injected into a cylinder multiple times during one cycle of the engine. . For example, in Patent Document 1, in a turbocharged diesel engine, main injection for torque generation, pilot injection performed prior to main injection to preheat the cylinder, main injection between pilot injection and main injection Pre-injection to suppress the ignition delay of fuel due to fuel, after-injection to increase the exhaust gas temperature after main injection, and post-injection to directly introduce fuel into the exhaust system after after-injection to increase the temperature of the catalyst It is described that fuel injection is performed at the five timings.

  Further, for example, Patent Document 2 describes a technique for changing the fuel injection amount of pilot injection in accordance with the engine load and the rotational speed in order to increase the in-cylinder temperature by preliminary combustion before main combustion. Accordingly, the in-cylinder temperature at the time of performing the main injection is surely exceeded the temperature at which the fuel can self-ignite, thereby preventing misfire of the fuel injected by the main injection.

JP 2009-293383 A JP 2005-240709 A

  In a diesel engine, it is advantageous to lower the geometric compression ratio from the viewpoint of reducing NOx emissions and improving thermal efficiency. However, an engine with a low compression ratio has a low compression end temperature and compression end pressure, which is disadvantageous for fuel ignitability. In particular, before the engine is completely warmed up, the in-cylinder temperature is low, so that the combustion stability tends to be lowered.

  In this regard, at least one pre-stage injection is performed at a timing prior to the main injection to appropriately cause the pre-stage combustion before the start of the main combustion. The inventors of the present application have obtained the knowledge that optimization is advantageous for stabilization of main combustion. Further, in order to increase the temperature in the cylinder and appropriately maintain the oxygen concentration in the cylinder to achieve stable main combustion, the introduction of EGR gas is combined with the fuel injection control including the above-described pre-injection and main injection. It has also been found that it is preferable to combine them.

  By the way, the amount of EGR introduced into the cylinder is set in feedback control based on the engine load and the engine speed, but when the manual transmission is shifted up, the accelerator opening is fully closed and the clutch is disconnected. As a result, the engine enters a no-load state and temporarily enters a fuel cut state. For this reason, during the shift up, the EGR amount is temporarily set to zero, and only fresh air having a relatively low temperature is introduced into the cylinder. This causes a temperature drop in the cylinder.

  In addition, by temporarily setting the EGR amount to zero during the shift up, the oxygen concentration in the cylinder increases. On the other hand, as the accelerator pedal is depressed after the shift up, the EGR gas is reintroduced into the cylinder. The oxygen concentration in the cylinder decreases. In other words, the oxygen concentration in the cylinder tends to fluctuate greatly as the opening degree of the closed EGR valve is changed to the open side from the middle of the shift up to the completion of the shift. Since a response delay occurs in the introduction of gas, the oxygen concentration in the cylinder becomes unstable.

  As a result, after the shift up, the ignitability of the pre-stage combustion deteriorates due to the decrease in the temperature in the cylinder and the destabilization of the oxygen concentration in the cylinder, which reduces the combustion stability of the main combustion. As a result, exhaust emission performance may be deteriorated.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to avoid a decrease in combustion stability of the diesel engine after the manual transmission is shifted up.

  A control device for a diesel engine disclosed herein is disposed so as to face an engine configured to compress and ignite fuel supplied into a cylinder, and directly inject fuel into the cylinder. And a fuel injection valve configured to recirculate the exhaust gas of the engine to the intake air to the cylinder.

  In the operating state before the engine is completely warmed up, the fuel injection valve is configured to start main fuel injection at or before compression top dead center in order to perform main combustion mainly including diffusion combustion. And pre-stage injection that performs at least one fuel injection at a timing before the main injection so that pre-stage combustion occurs before the start of the main combustion, and the EGR means Exhaust gas recirculation is performed in accordance with the operating state, and the EGR means is also in the middle of a transmission shift-up process involving full closure of the accelerator and release of the clutch, immediately before the start of the shift-up process. The EGR amount is retained.

  According to this configuration, in the operating state before the engine is completely warmed up, the pre-stage injection including at least one fuel injection is performed, and the pre-stage combustion is caused before the start of the main combustion. This increases the temperature and pressure in the cylinder at the start of main injection. Thereby, the ignitability of the fuel injected by the main injection is enhanced, and the main combustion mainly including diffusion combustion is stably performed. In addition, the EGR means performs exhaust gas recirculation of an EGR amount corresponding to the operating state of the engine, in other words, by performing feedback control, so that a relatively high temperature exhaust gas is introduced into the cylinder to increase the temperature in the cylinder. In addition to being advantageous, the oxygen concentration in the cylinder is appropriately adjusted according to the operating state of the engine. This contributes to stabilization of pre-stage combustion and diffusion combustion.

  As a result, it is advantageous for improving exhaust emission performance and fuel consumption in an operating state before the engine is completely warmed up.

  Further, in the above-described configuration, when the transmission shift-up process involving the full closure of the accelerator and the release of the clutch is executed, the EGR amount immediately before the start of the process is maintained during the shift-up process. The That is, even when the engine becomes unloaded and temporarily enters a fuel cut state, the EGR amount does not become zero, and exhaust gas is introduced into the cylinder together with fresh air. This suppresses the temperature drop in the cylinder during the upshift process, and the cylinder temperature is maintained at a relatively high level.

  Further, since the EGR amount is kept unchanged, an increase in oxygen concentration in the cylinder during the upshift process is suppressed. Further, for example, the opening / closing control of the exhaust gas recirculation valve for adjusting the EGR amount arranged on the EGR passage is omitted, and the opening degree of the exhaust gas recirculation valve is maintained as it is before and after the upshift process. For this reason, when the accelerator pedal is depressed after the completion of the shift-up process, the variation difference in the oxygen concentration in the cylinder is small, and the introduction delay of EGR gas is also suppressed.

  In this way, suppression of temperature drop in the cylinder and stabilization of the oxygen concentration in the cylinder after the shift-up process are realized, and deterioration of the ignitability of the pre-stage combustion in particular is avoided. As a result, the combustion stability of the main combustion is ensured, which is advantageous for improving the exhaust emission performance.

  The control device for the diesel engine further includes an intake air amount adjusting means including a throttle valve disposed on an intake passage of the engine, and the intake air amount adjusting means performs the upshifting process during the upshifting process. The opening degree of the throttle valve immediately before the start of the process may be maintained.

  By doing so, both the fresh air and EGR amount introduced into the cylinder are maintained before and after the upshift process, which is more advantageous for stabilizing the oxygen concentration in the cylinder after the upshift process. Become.

  As described above, according to the diesel engine control device, the combustion stability of the pre-stage combustion and the main combustion after the shift-up process of the manual transmission can be ensured in the operating state before complete warm-up. It is advantageous for improving the emission performance.

It is the schematic which shows the structure of a diesel engine. It is a block diagram concerning control of a diesel engine. It is a figure which shows an example of the fuel-injection form in the operation area | region before complete warming-up of a diesel engine, and an example of the log | history of the heat release rate accompanying it. It is a main flowchart concerning the clip control before and after the shift-up process. 5 is a flowchart according to a shift-up determination step process in the main flow shown in FIG. (A) accelerator opening signal, (b) accelerator opening change rate, (c) engine speed, (d) fuel injection amount, (e) clutch operation signal, (f) ) Gear position signal, (g) neutral signal, (h) shift determination flag, (i) shift up determination step signal, (j) target cylinder oxygen concentration and actual cylinder oxygen concentration, (k) throttle valve opening, It is a timing chart of (l) exhaust gas recirculation valve opening, and (m) cooler bypass valve opening.

  Hereinafter, the diesel engine which concerns on embodiment is demonstrated based on drawing. The following description of the preferred embodiment is merely exemplary in nature. 1 and 2 show a schematic configuration of an engine (engine body) 1 according to the embodiment. The engine 1 is a diesel engine that is mounted on a vehicle and is supplied with fuel mainly composed of light oil. The vehicle on which the engine 1 is mounted is an MT vehicle having a manual transmission 73, and the output torque accompanying the driving of the engine 1 is a manual transmission that is connected to the crankshaft 15 via the clutch mechanism 72. 73 to the drive wheel 74.

  The engine 1 includes a cylinder block 11 provided with a plurality of cylinders 11a (only one is shown), a cylinder head 12 provided on the cylinder block 11, and a lower side of the cylinder block 11, and is lubricated. And an oil pan 13 in which oil is stored. In each cylinder 11a of the engine 1, a piston 14 is fitted and removably fitted. A top surface of the piston 14 is formed with a cavity defining a reentrant combustion chamber 14a. The piston 14 is connected to the crankshaft 15 via a connecting rod 14b.

  In the cylinder head 12, an intake port 16 and an exhaust port 17 are formed for each cylinder 11a, and an intake valve 21 and an exhaust valve that open and close the opening of the intake port 16 and the exhaust port 17 on the combustion chamber 14a side. 22 are arranged respectively.

  In the valve systems that drive these intake and exhaust valves 21 and 22, respectively, a hydraulically operated variable mechanism that switches the operation mode of the exhaust valve 22 between a normal mode and a special mode on the exhaust valve side (see FIG. 2 below). VVM (Variable Valve Motion). Although detailed illustration of the configuration of the VVM 71 is omitted, two types of cams having different cam profiles, a first cam having one cam peak and a second cam having two cam peaks, and the first cam When a lost motion mechanism that selectively transmits the operating state of one of the first and second cams to the exhaust valve is included, and the operating state of the first cam is transmitted to the exhaust valve 22 The exhaust valve 22 operates in a normal mode in which the valve is opened only once during the exhaust stroke, whereas when the operating state of the second cam is transmitted to the exhaust valve 22, the exhaust valve 22 is in the exhaust stroke. In addition, the valve operates in a special mode in which the exhaust is opened twice so that the valve is opened during the intake stroke.

  Switching between the normal mode and the special mode of the VVM 71 is performed by hydraulic pressure supplied from an engine-driven hydraulic pump (not shown), and the special mode is used in the control related to the internal EGR. In order to enable switching between the normal mode and the special mode, an electromagnetically driven valve system that drives the exhaust valve 22 by an electromagnetic actuator may be employed. The execution of the internal EGR is not limited to the double opening of the exhaust. For example, the internal EGR control may be performed by opening the intake valve 21 twice, or by opening the intake twice. An internal EGR control may be performed in which the burned gas remains by providing a negative overlap period in which both the intake valve 21 and the exhaust valve 22 are closed in the intake stroke. The internal EGR control by the VVM 71 is performed mainly when the engine 1 with low fuel ignitability is cold.

  The cylinder head 12 is provided with an injector 18 for injecting fuel, and a glow plug 19 for warming the intake air in each cylinder 11a to improve the ignitability of the fuel when the engine 1 is cold. The injector 18 is arranged so that its fuel injection port faces the combustion chamber 14a from the ceiling surface of the combustion chamber 14a. Basically, fuel is directly supplied to the combustion chamber 14a near the top dead center of the compression stroke. The injection is supplied.

  An intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 16 of each cylinder 11a. On the other hand, an exhaust passage 40 for discharging burned gas (that is, exhaust gas) from the combustion chamber 14a of each cylinder 11a is connected to the other side of the engine 1. In the intake passage 30 and the exhaust passage 40, as will be described in detail later, a large turbocharger 61 and a small turbocharger 62 for supercharging intake air are disposed.

  An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30. On the other hand, a surge tank 33 is disposed near the downstream end of the intake passage 30. The intake passage 30 downstream of the surge tank 33 is an independent passage branched for each cylinder 11a, and the downstream end of each independent passage is connected to the intake port 16 of each cylinder 11a.

  Between the air cleaner 31 and the surge tank 33 in the intake passage 30, compressors 61a and 62a of large and small turbochargers 61 and 62, and an intercooler 35 that cools the air compressed by the compressors 61a and 62a, A throttle valve 36 is provided for adjusting the amount of intake air into the combustion chamber 14a of each cylinder 11a. The throttle valve 36 is basically fully opened, but is fully closed when the engine 1 is stopped so that no shock is generated.

  The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 11a and connected to the outer end of the exhaust port 17 and a collecting portion where the independent passages gather. Yes.

  On the downstream side of the exhaust manifold in the exhaust passage 40, the turbine 62b of the small turbocharger 62, the turbine 61b of the large turbocharger 61, and exhaust for purifying harmful components in the exhaust gas in order from the upstream side. A purification device 41 and a silencer 42 are provided.

The exhaust purification device 41 includes an oxidation catalyst 41a and a diesel particulate filter (hereinafter referred to as a filter) 41b, which are arranged in this order from the upstream side. The oxidation catalyst 41a and the filter 41b are accommodated in one case. The oxidation catalyst 41a has an oxidation catalyst carrying platinum or platinum added with palladium or the like, and promotes a reaction in which CO and HC in the exhaust gas are oxidized to produce CO ₂ and H ₂ O. Is. The filter 41b collects particulates such as soot contained in the exhaust gas of the engine 1. The filter 41b may be coated with an oxidation catalyst.

  A portion of the intake passage 30 between the surge tank 33 and the throttle valve 36 (that is, a portion on the downstream side of the small compressor 62a of the small turbocharger 62), the exhaust manifold and the small turbocharger in the exhaust passage 40. The portion between the turbocharger 62 and the small turbine 62 b (that is, the upstream portion of the small turbocharger 62 from the small turbine 62 b) is an exhaust gas recirculation for recirculating a part of the exhaust gas to the intake passage 30. They are connected by a passage 50. The exhaust gas recirculation passage 50 is provided with an exhaust gas recirculation valve 51a for adjusting the recirculation amount of the exhaust gas to the intake passage 30 and an EGR cooler 52 for cooling the exhaust gas with engine cooling water. It includes a passage 51 and a cooler bypass passage 53 for bypassing the EGR cooler 52. The cooler bypass passage 53 is provided with a cooler bypass valve 53 a for adjusting the flow rate of the exhaust gas flowing through the cooler bypass passage 53.

  The large turbocharger 61 has a large compressor 61 a disposed in the intake passage 30 and a large turbine 61 b disposed in the exhaust passage 40. The large compressor 61 a is disposed between the air cleaner 31 and the intercooler 35 in the intake passage 30. On the other hand, the large turbine 61b is disposed between the exhaust manifold and the oxidation catalyst 41a in the exhaust passage 40.

  The small turbocharger 62 has a small compressor 62 a disposed in the intake passage 30 and a small turbine 62 b disposed in the exhaust passage 40. The small compressor 62 a is disposed on the downstream side of the large compressor 61 a in the intake passage 30. On the other hand, the small turbine 62 b is disposed on the upstream side of the large turbine 61 b in the exhaust passage 40.

  That is, in the intake passage 30, a large compressor 61a and a small compressor 62a are arranged in series from the upstream side, and in the exhaust passage 40, a small turbine 62b and a large turbine 61b are arranged in series from the upstream side. Has been. The large and small turbines 61b and 62b are rotated by the exhaust gas flow, and the large and small turbines 61a and 62a connected to the large and small turbines 61b and 62b are rotated by the rotation of the large and small turbines 61b and 62b, respectively. Each operates.

  The small turbocharger 62 is relatively small, and the large turbocharger 61 is relatively large. That is, the large turbine 61 b of the large turbocharger 61 has a larger inertia than the small turbine 62 b of the small turbocharger 62.

  A small intake bypass passage 63 that bypasses the small compressor 62 a is connected to the intake passage 30. The small intake bypass passage 63 is provided with a small intake bypass valve 63 a for adjusting the amount of air flowing to the small intake bypass passage 63. The small intake bypass valve 63a is configured to be in a fully closed state (that is, normally closed) when no power is supplied.

  On the other hand, the exhaust passage 40 is connected to a small exhaust bypass passage 64 that bypasses the small turbine 62b and a large exhaust bypass passage 65 that bypasses the large turbine 61b. The small exhaust bypass passage 64 is provided with a regulating valve 64a for adjusting the exhaust amount flowing to the small exhaust bypass passage 64, and the large exhaust bypass passage 65 has an exhaust amount flowing to the large exhaust bypass passage 65. A wastegate valve 65a for adjusting the pressure is provided. Both the regulating valve 64a and the waste gate valve 65a are configured to be in a fully open state (that is, normally open) when no power is supplied.

  The large turbocharger 61 and the small turbocharger 62 are integrated into a single unit including the intake passage 30 and the exhaust passage 40 in which the large turbocharger 61 and the small turbocharger 62 are arranged, thereby forming a supercharger unit 60. doing. The supercharger unit 60 is attached to the engine 1.

The diesel engine 1 configured as described above is controlled by a powertrain control module (hereinafter referred to as PCM) 10. The PCM 10 includes a microprocessor having a CPU, a memory, a counter timer group, an interface, and a path connecting these units. The PCM 10 constitutes a control device. As shown in FIG. 2, the PCM 10 includes a water temperature sensor SW1 that detects the temperature of the engine cooling water, a supercharging pressure sensor SW2 that is attached to the surge tank 33 and detects the pressure of the air supplied to the combustion chamber 14a, An intake air temperature sensor SW3 that detects the temperature of the intake air, a crank angle sensor SW4 that detects the rotation angle of the crankshaft 15, and an accelerator opening sensor that detects an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown) of the vehicle. SW5, O ₂ sensor SW6 for detecting an oxygen concentration in the exhaust gas and, the detection signal of the vehicle speed sensor SW7 for detecting a vehicle speed is input, the engine 1 and the vehicle by performing various calculations based on these detection signals The state is determined, and according to this, the injector 18, the glow plug 19, the valve-operated VVM 71, various valves 36, 51a, 5 A control signal is output to the actuator 3a.

  The PCM 10 controls the operation of the large and small turbochargers 61 and 62 when the engine is operating. Specifically, the PCM 10 controls the openings of the small intake bypass valve 63a, the regulator valve 64a, and the wastegate valve 65a to the openings set according to the operating state of the engine 1, respectively. Specifically, when the engine 1 is warm, the PCM 10 sets the small intake bypass valve 63a and the regulating valve 64a to an opening other than a fully open position and a fully closed waste gate valve 65a in a predetermined region on the low load and low rotation side. Thus, both the large and small turbochargers 61 and 62 are operated. On the other hand, in a predetermined region on the high load and high rotation side, the small turbocharger 62 becomes exhaust resistance, so that the small intake bypass valve 63a and the regulating valve 64a are fully opened, and the waste gate valve 65a is fully closed. By making the opening close, the small turbocharger 62 is bypassed and only the large turbocharger 61 is operated. The waste gate valve 65a is set slightly open to prevent the large turbocharger 61 from over-rotating.

  Thus, the engine 1 is configured to have a relatively low compression ratio with a geometric compression ratio of 12 or more and 15 or less (for example, 14), thereby improving exhaust emission performance and thermal efficiency. It is trying to improve.

(Outline of engine combustion control)
The basic control of the engine 1 by the PCM 10 mainly determines a target torque (in other words, a target load) based on the accelerator opening, and the fuel injection amount and injection timing corresponding to the target torque are determined by the injector 18. This is realized by operation control. The target torque is set so as to increase as the accelerator opening increases and the engine speed increases, and the fuel injection amount is set based on the target torque and the engine speed. The injection amount is set to increase as the target torque increases and as the engine speed increases. Further, the exhaust gas recirculation into the cylinder 11a is controlled by controlling the opening degree of the throttle valve 36, the exhaust gas recirculation valve 51a, and the cooler bypass valve 53a (that is, external EGR control) or by controlling the VVM 71 (that is, internal EGR control). Control the rate.

FIG. 3 shows an example of the fuel injection mode (upper diagram) and the history of the heat generation rate in the cylinder 11a (lower diagram) when the engine 1 is not warmed up (in other words, before complete warm-up). The PCM 10 determines whether the engine 1 is warmed up or not warmed based on the detection result of the water temperature sensor SW1. Specifically, the PCM 10 determines a warm-up state when the water temperature is equal to or higher than a predetermined temperature (for example, 80 ° C.), and determines an unwarmed state when the water temperature is lower than the predetermined temperature. When the engine 1 is not warmed up, as shown in FIG. 3, the PCM 10 performs three pre-injections (previous stage) with a relatively short time interval at a timing relatively close to the compression top dead center during the compression stroke. Injection) and the main injection is executed once near the compression top dead center. That is, a total of four fuel injections are executed. The three pre-injections cause pre-combustion (corresponding to pre-stage combustion) having a sufficient heat generation rate so that the peak of the heat generation rate occurs at a predetermined time before compression top dead center. In other words, pre-combustion occurs before the start of main combustion, thereby increasing the temperature and pressure in the cylinder 11a at the time of starting main injection. This shortens the ignition delay τ _main of the fuel injected by the main injection. The main injection starts injection at a predetermined timing before the compression top dead center or at the compression top dead center as shown in the figure, but because the ignition delay τ _main is short, the main combustion accompanying the main injection is Starts near compression top dead center. This is advantageous for improving the thermal efficiency, and hence for improving the fuel consumption. Here, in the example of FIG. 3B, the ignition delay τ _main of the main combustion is defined as from the start of the main injection until the heat generation rate of the main combustion starts increasing. In this control, the heat generation rate by the pre-combustion reaches its peak, and after the heat generation rate starts to decrease, the pre-injection injection mode and the main injection of the main injection start so that the heat generation rate by the main combustion starts to increase. The injection mode is set, and a minimum value exists between the peak of the heat generation rate of the pre-combustion and the peak of the heat generation rate of the main combustion. The ignition delay τ _main of the main combustion can be defined as the minimum value from the start of the main injection.

  Moreover, the said combustion makes the raise of the heat release rate of subsequent main combustion slow. This is advantageous in reducing combustion noise and improving NVH (Noise Vibration Harshness) performance. That is, the pre-injection and the accompanying pre-combustion increase the controllability of the main combustion and generate the main combustion at a desired timing, which is advantageous for improving fuel efficiency and NVH performance.

  Furthermore, since the peak of the heat generation rate due to pre-combustion shifts before the start of the increase in heat generation rate due to main combustion, the energy obtained by pre-combustion is avoided while avoiding increasing the combustion noise of main combustion. Thus, at the start of main combustion, the temperature and pressure in the cylinder can be increased to a state necessary and sufficient for shortening the ignition delay. This not only shortens the ignition delay, but also minimizes the injection amount of the pre-stage injection, which is advantageous for improving fuel consumption.

  Along with such injection control, external EGR control is executed when the engine 1 is not warmed up. This control is feedback control by setting the exhaust gas recirculation valve 51a and the cooler bypass valve 53a to openings corresponding to the engine load and the rotational speed, respectively. As a result, a relatively high-temperature exhaust gas that bypasses the EGR cooler 52 is introduced into the cylinder 11a, so that the temperature rise in the cylinder 11a of the engine 1 and the oxygen concentration in the cylinder 11a in an unwarmed state are optimized. Thus, the above-described pre-stage combustion and main combustion are stabilized.

(Intake control during the shift-up process)
As described above, in the operation state before the engine 1 is completely warmed up, the intake control including the external EGR control is executed together with the fuel injection control including the pre-injection and the main injection. Here, when the manual transmission 73 is shifted up, the engine 1 is brought into a no-load state due to the fully closed accelerator and the clutch mechanism 72 being opened, and temporarily into a fuel cut state. As a result, the exhaust gas recirculation valve 51a and the cooler bypass valve 53a set according to the load and the rotational speed of the engine 1 are fully closed, respectively, and the EGR amount is temporarily set to zero. In the manual transmission 73, if the upshifting operation is performed through the neutral position and the clutch mechanism 72 is engaged and the accelerator pedal is depressed to complete the upshifting process, the exhaust gas recirculation valve 51a and the cooler Each of the bypass valves 53a is changed to a predetermined opening according to the rotational speed and load of the engine 1.

  Therefore, during the shift-up process including the accelerator fully closed, the clutch mechanism 72 opened, the shift operation, the clutch mechanism 72 engaged, and the accelerator pedal depressed, the EGR amount becomes zero and a relatively low temperature new Only ki is introduced into the cylinder 11a. This lowers the temperature in the cylinder 11a and increases the oxygen concentration in the cylinder 11a. Further, after the completion of the shift-up process and after the completion thereof, the closed exhaust gas recirculation valve 51a and the cooler bypass valve 53a are opened so that the oxygen concentration in the cylinder 11a decreases. Since there is a response delay in the recirculation of the EGR gas, the oxygen concentration in the cylinder 11a becomes unstable when the accelerator pedal is depressed after the shift-up process. Combining this temperature decrease in the cylinder 11a and the instability of oxygen concentration, after the shift-up process, the ignitability of the pre-stage combustion is deteriorated, the combustion stability of the pre-stage combustion is lowered, and consequently the combustion stability of the main combustion is reduced. The nature will decline.

  Therefore, in this engine system, the PCM 10 is configured so that the exhaust gas recirculation valve 51a, the cooler bypass valve 53a, and the throttle valve 36 are in the middle of the shift-up process in order to avoid deterioration in combustion stability after the shift-up process. Clip control is performed to keep the opening constant at the opening just before the start of the upshift process.

  FIG. 4 shows a main flow related to clip control during the upshifting process executed by the PCM 10. In step S41 after the start, various signals necessary for the subsequent control are read. In step S42, a processing operation for upshift determination is performed based on the read signals. In step S43, it is determined whether or not the shift-up determination is within a permitted range. That is, in step S43, when the engine speed is within a predetermined upper and lower speed limit, the vehicle speed is equal to or higher than the predetermined speed, the gear position is equal to or lower than the predetermined gear stage, and the brake signal is OFF, the upshift determination is performed. When it is determined that it is within the permitted range, and any one of the conditions is not satisfied, it is determined that it is not within the permitted range. If it is not within the permitted range (NO), the process proceeds to step S46, where it is determined that there is an error, and the upshift determination is terminated (step S46). On the other hand, when it is within the permitted range for the upshift determination in step S43 (YES), after setting the upshift determination permission flag (see FIG. 6 (h)), the process proceeds to step S44. In step S44, the flow of the upshift determination step process shown in FIG. 5 is executed. This shift-up determination step processing is performed by sequentially determining the execution of the accelerator fully closed, the clutch mechanism 72 opened, the shift operation, the clutch mechanism 72 engaged, and the accelerator pedal depression included in the shift up process. This is a logic for determining whether or not the upshift process is being executed, and this process makes it possible to start the clip control early when the upshift process is being executed. In addition, when it is determined that the process is not an upshift process, the clip process can be immediately stopped. Here, the shift-up determination step process will be described with reference to the flow of FIG. 5 and the timing chart of FIG. The timing chart of FIG. 6 is an example of a timing chart of each parameter during the upshift process from the second speed to the third speed as shown in FIG.

  First, in step S51, it is determined whether or not it is shift-up determination step 1. The shift-up determination step 1 is detection of a change in the accelerator opening (see FIG. 6B) or detection of release of the clutch mechanism 72 (see FIG. 6E). That is, when the occupant returns the accelerator pedal and the amount of deviation of the accelerator opening exceeds a predetermined amount and the accelerator opening is equal to or less than the predetermined opening, or when the clutch mechanism 72 is released by depressing the clutch pedal, If Step 1 of the upshift process is determined (see FIG. 6 (i)), the process proceeds to Step S52. On the other hand, when those signals are not detected for a predetermined time or longer, the process proceeds to step S516, that is, a normal intake control, which will be described later, as a timeout.

  In step S52, it is determined whether there is a shift determination error. This determination is to determine whether or not an operation different from the shift-up process is being performed. For example, when the clutch mechanism 72 is continuously released for a predetermined time or more, an error determination is made that it is not a shift-up process (for example, the vehicle is decelerating), and the process proceeds to step S516. On the other hand, when it is not an error determination (NO), the process proceeds to step S53.

In step S53, the EGR opening just before the upshift determination step 1, in other words, just before the start of the upshifting process, and the opening of the throttle valve 36 are stored.
The EGR opening in this example includes the opening of both the exhaust gas recirculation valve 51a and the cooler bypass valve 53a. For example, in a system in which the EGR cooler 52 is omitted, only the exhaust gas recirculation valve 51a is included. Control may be used.

  In a succeeding step S54, it is determined whether or not it is a shift-up determination step 2. The shift-up determination step 2 is to detect the release of the clutch mechanism 72 when a change in the accelerator opening is detected in the shift-up determination step 1 described above, and to detect the release of the clutch mechanism 72 in the shift-up determination step 1. When this is done, a change in the accelerator opening is detected. That is, in the two steps of the shift-up determination step 1 and the shift-up determination step 2, the two operations of fully closing the accelerator and opening the clutch mechanism 72 are detected regardless of the order. If YES in step S54, it is determined that step 2 of the upshift process is determined (see FIG. 6 (i)), and the process proceeds to step S55. On the other hand, after the accelerator is fully closed or the clutch mechanism 72 is released, if the next operation is not performed and a time-out occurs, the process proceeds from step S54 to step S516, assuming that it is not a shift-up process. Here, the timeout related to the shift-up determination step 1 and step 2 is set to be relatively short. This is because the full closure of the accelerator and the release of the clutch mechanism 72 are not limited to the upshifting operation but are also performed when the vehicle is decelerating. In order to return to control early, the timeout is set to a relatively short time.

  In step S55, it is determined whether there is a shift determination error. If there is no error (NO), the process proceeds to step S56, and the opening of the exhaust gas recirculation valve 51a and the cooler bypass valve 53a and the opening of the throttle valve 36 are stored in step S53. Or at the throttle opening (see the solid lines in FIGS. 6 (k), (l), and (m)). On the other hand, if an error determination is made in step S55, the process proceeds to step S516. An example of the error determination at this step can be a case where the fuel injection amount becomes a predetermined amount or more.

  In step S57, it is determined whether or not it is shift-up determination step 3. The shift-up determination step 3 is that the gear position of the manual transmission 73 is neutral (see (g) in FIG. 6). That is, in the shift-up operation of the manual transmission 73, when shifting from the shift stage before the shift-up (second speed in the figure) to the shift stage after the shift-up (third speed in the figure), This is to be neutral. When a neutral signal is detected, it is determined that step 3 of the upshift process is determined (see FIG. 6 (i)), and the process proceeds to step S58. On the other hand, when a timeout occurs without detecting a neutral signal, the process proceeds to step S516.

  In step S58, it is determined whether there is a shift determination error. For example, when the manual transmission 73 remains neutral and a predetermined time has elapsed, it is determined that it is preferable to return to the normal intake control rather than continuing the clip control as it is, and an error determination is made, and the process proceeds to step S516. To do. On the other hand, when NO is determined in step S58, the process proceeds to step S59, and the clip control is continued as it is for the exhaust gas recirculation valve 51a, the cooler bypass valve 53a, and the throttle valve 36.

  In step S510, it is determined whether it is shift-up determination step 4. The upshift determination step 4 is that the manual transmission 73 is detected to be other than neutral (see (g) of FIG. 6). That is, when the upshifting operation of the manual transmission 73 is completed via neutral, the process proceeds to step S511. On the other hand, when a timeout occurs without detecting a neutral OFF signal for a predetermined time or longer, the process proceeds from step S510 to step S516.

  In step S511, it is determined whether there is a shift determination error. For example, when the shift-up operation of the manual transmission 73 is completed but the release of the clutch mechanism 72 continues for a predetermined time or more, an error determination is made, and the process proceeds from step S511 to step S516. Here, the predetermined time (timeout time) related to the shift-up determination step 4 and the determination step 5 described later is set longer than the timeout time related to the shift-up determination step 4 and step 5 described above. This is because when the manual transmission 73 becomes neutral once and shifts to another shift stage as in the shift-up determination step 4, the operation is a shift-up process. This is because the demand to stop the control and return to the normal intake control early is low. When the determination in step S511 is NO, the process proceeds to step S512, and the openings of the exhaust gas recirculation valve 51a and the cooler bypass valve 53a and the opening of the throttle valve 36 are maintained as they are. That is, the clip control is continued.

  In step S513, it is determined whether it is shift-up determination step 5. In the upshift determination step 5, it is detected that the fuel injection amount has become a predetermined amount or more. This determines that the upshift operation has been completed and the occupant has depressed the accelerator pedal. If YES is determined, the process proceeds to step S514. On the other hand, for example, when the fuel injection amount times out without exceeding the predetermined amount, the process proceeds from step S513 to step S516. In step S514, it is determined whether or not there is a shift determination error. If YES, the process proceeds to step S516, and if NO, the process proceeds to step S515.

  In step S515, the shift-up process is completed, and gradual change control for smoothly connecting from the clip control to the normal intake control is performed. For example, the opening degree of the exhaust gas recirculation valve 51a, the cooler bypass valve 53a, and the throttle valve 36 is gradually changed based on the accelerator opening degree and the fuel injection amount ((k) (l) (m) in FIG. ). In step S516, the normal intake control is restored, and the process returns to step 45 in the flow of FIG. 4 to complete the upshift determination.

  Thus, as shown in FIGS. 6 (a), 6 (b), and 6 (e), when the accelerator is fully closed and the clutch mechanism 72 is opened, the engine 1 is in a no-load state, and as shown in FIG. The number gradually decreases, and the fuel injection amount is set to substantially zero as shown in FIG. Thereby, in the normal intake control, the EGR amount is also set to zero (see “EGRCUT condition” in FIG. 4D). That is, in normal intake control, the target oxygen concentration in the cylinder 11a increases as shown by the dotted line in FIG. 6 (j), and the exhaust gas recirculation valve as shown by the dotted line in FIGS. 51a and the cooler bypass valve 53a are closed, and the throttle valve 36 is opened as indicated by a dotted line in FIG. As a result, in normal intake control, the actual oxygen concentration in the cylinder 11a becomes significantly high during the shift-up process as indicated by the broken line in FIG. It becomes unstable because it is suddenly changed to a relatively low concentration according to the engine load and the engine speed.

  On the other hand, in the clip control, as shown by the solid line in FIG. 6 (j), during the upshift process, the target oxygen concentration in the cylinder 11a is held at a value just before the start of the upshift process. As indicated by solid lines in FIGS. (K), (l), and (m), the throttle valve 36, the exhaust gas recirculation valve 51a, and the cooler bypass valve 53a are held at the opening just before the start of the upshift process. . That is, in the illustrated example, the throttle valve 36 is made constant at a predetermined opening on the closing side, and the exhaust gas recirculation valve 51a and the cooler bypass valve 53a are made constant at a predetermined opening on the opening side. In the clip control, the actual oxygen concentration in the cylinder 11a is suppressed from becoming high during the shift-up process and unstable after the shift-up process, as indicated by a dashed line in FIG. Is avoided. Further, during the shift-up process, not only fresh air but also EGR gas is introduced into the cylinder 11a, so that a temperature drop in the cylinder 11a is also suppressed.

  As a result, when the accelerator pedal is depressed after the upshifting process, the ignitability of the pre-stage combustion becomes good, and the combustion stability of the main combustion is improved. As a result, it becomes advantageous for improvement of exhaust emission performance.

  In addition, the determination of the shift-up process is performed by a plurality of steps corresponding to a plurality of operations included in the shift-up process, so that an existing sensor can be used without using only a sensor or the like for detecting the shift-up process. Can be used to detect the shift-up process at an early stage and to quickly start clip control. This is advantageous in improving the stability of the pre-stage combustion and the main combustion after the shift-up process described above. On the other hand, the determination of the shift-up process by a plurality of steps can also be detected at an early stage that it is not a shift-up process, and even if the clip control has been started, the clip control is immediately terminated and the normal intake control (that is, It is possible to return to feedback control at an early stage. This is also advantageous for improving the combustion stability, and hence for improving the exhaust emission.

1 Diesel engine (engine)
10 PCM (EGR means, intake air amount control means)
11a Cylinder 18 injector (fuel injection valve)
30 Intake passage 36 Throttle valve 40 Exhaust passage 50 Exhaust gas recirculation passage (EGR means)
51a Exhaust gas recirculation valve (EGR means)
53a Cooler bypass valve (EGR means)
72 Clutch mechanism 73 Manual transmission

Claims (2)

An engine configured to compress and ignite the fuel supplied into the cylinder;
A fuel injection valve disposed facing the cylinder and configured to directly inject fuel into the cylinder;
EGR means configured to recirculate exhaust gas of the engine to intake air to the cylinder,
In the operating state before the engine is completely warmed up,
The fuel injection valve has a main injection that starts fuel injection at or before compression top dead center in order to perform main combustion mainly consisting of diffusion combustion, and pre-stage combustion occurs before the start of the main combustion. And a pre-stage injection that performs at least one fuel injection at a timing prior to the main injection,
The EGR means performs an exhaust gas recirculation of an EGR amount corresponding to an operating state of the engine,
The EGR means is a control device for a diesel engine that holds an EGR amount immediately before the start of the shift-up process during a shift-up process of the transmission that involves fully closing the accelerator and releasing the clutch. In the control apparatus of the diesel engine of Claim 1,
An intake air amount adjusting means including a throttle valve disposed on the intake passage of the engine;
The intake air amount adjusting means is a control device for a diesel engine that maintains the opening degree of the throttle valve immediately before the start of the upshift process during the upshift process.

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