JP5516144B2 - Automotive diesel engine - Google Patents

Description

  The technology disclosed herein relates to an automobile-mounted diesel engine, and particularly to fuel injection control thereof.

  In a diesel engine installed in an automobile, in order to reduce NOx and soot in exhaust gas, reduce noise and vibration, improve fuel consumption and torque, etc., multiple injections of fuel into the cylinder are performed during one engine cycle. There are things to do. For example, in Patent Document 1, in a diesel engine that performs so-called external EGR control in which exhaust gas is recirculated through an exhaust gas recirculation passage, main injection for torque generation is performed prior to main injection for preheating the cylinder. Pilot injection, pre-injection for suppressing fuel ignition delay due to main injection between pilot injection and after injection, after-injection for raising exhaust gas temperature after main injection, and exhaust system after after-injection Describes that fuel injection is performed at five timings of post-injection in which fuel is directly introduced to increase the temperature of the catalyst.

JP 2009-293383 A

  By the way, by dividing the engine operating region related to the engine load and the engine speed into several regions, and appropriately selecting and combining the above-described five timing fuel injections in each region, It is conceivable to set different fuel injection modes. In other words, in each operation region, the fuel injection mode corresponding to the state in the cylinder is switched while increasing / decreasing the total fuel injection amount according to the engine load and the engine speed. Thus, the combustion state in the cylinder can be optimized for each operation region.

  However, the inventors of the present application switched the fuel injection mode at the same time as the transition of the driving region with the acceleration or deceleration of the vehicle, so that the combustion state became unstable or the combustion noise was loud. I found that inconvenience such as becoming may occur.

  The technology disclosed herein has been made in view of the above points, and the object of the technology is to provide instability of the combustion state in the cylinder during a transition in which the fuel injection mode is switched in a diesel engine for an automobile. And to avoid inconveniences including increased combustion noise.

  According to a study by the inventors of the present application, during the transition transition of the operation region, the operation region is shifted according to the engine load and the rotational speed, whereas the state change in the cylinder is delayed while the fuel injection mode is changed. Is switched at the same time as the transition of the operation region, the state in the cylinder does not correspond to the fuel injection form after switching, which leads to instability of combustion state and increase in combustion noise I found out.

  Accordingly, the technology disclosed herein delays the switching of the fuel injection mode with respect to the transition of the operation region at the transition transition of the operation region.

  Specifically, the technology disclosed herein is directed to a diesel engine mounted on an automobile, and the diesel engine is mounted on an automobile and supplied with fuel mainly composed of light oil, and in a cylinder of the engine body. And a fuel injection valve that directly injects the fuel into the cylinder, and an injection control means that controls the fuel injection mode into the cylinder through the fuel injection valve. .

  The injection control means includes a main injection that injects fuel in the vicinity of compression top dead center to perform main combustion mainly consisting of diffusion combustion, and a pre-stage where the heat generation rate reaches a peak at a predetermined time before the compression top dead center. At least one pre-injection in which fuel is injected before the main injection is performed so that combustion occurs, and the number of executions of the pre-injection is less in an operation region where the load of the engine body is higher The number of times, the injection control means, after the engine body shifts to the higher load operation region from the relatively low load operation region to the higher load operation region, after the transition to the high load operation region, During the predetermined period, transient control is performed in which the number of times of the preceding stage injection is maintained at a number greater than the number of times set in the shifted operation region.

  According to this configuration, when the engine main body is in a low load region, the number of the pre-stage injections executed before the main injection is increased, so that the pre-stage combustion in which the heat generation rate reaches a peak at a predetermined time before the compression top dead center is ensured. It is possible to improve the stability of the subsequent main combustion and reduce the combustion noise.

  On the other hand, when the engine body is in the high load region, the total fuel injection amount increases, and the temperature in the cylinder increases as the load increases. Pre-stage combustion in which the heat generation rate reaches a peak at a predetermined time before the point occurs, and the stability of the subsequent main combustion can be improved and combustion noise can be reduced. On the other hand, if the number of times of the pre-stage injection is too large, the heat generation rate of the pre-stage combustion becomes too high, which may increase the combustion noise.

  Thus, at the time of acceleration in which the engine body shifts from a relatively low load operation region to a higher load operation region, after the transition to the high load operation region, the number of times of the pre-stage injection is set for a predetermined period. Then, the transient control is executed to keep the number of times larger than the number of times set in the shifted operation region. This is equivalent to delaying the switching of the fuel injection form for a predetermined period after the transition to the operation region. Thus, until the state in the cylinder is switched to the state corresponding to the transitioned operation region, the fuel injection mode is set so as to correspond to the operation region before the transition than the operation region after the transition, and the state in the cylinder is changed. While waiting for switching, the fuel injection mode is switched to the injection mode corresponding to the operation region after the transition after the state in the cylinder is switched. As a result, it is possible to avoid a state in which the state in the cylinder does not correspond to the fuel injection mode at the transition transition of the operation region, and it is possible to avoid instability of combustion caused by the state. Further, since the number of pre-stage injections is reduced after the state in the cylinder is switched, an increase in combustion noise can be avoided.

  Here, in order to “hold the number of times of the preceding stage injection to a number greater than the number set in the transitioned operation region”, for example, in the operation region before the transition, two previous stage injections are set and the transition is performed. In the case where one pre-injection is set in the subsequent operation region, the predetermined period includes holding the number of pre-injection twice more than once after the operation region is shifted. Similarly, in the case where three pre-stage injections are set in the operation area before the transition and two pre-stage injections are set in the operation area after the transition, the predetermined period is Including maintaining the number of injections at 3 times, more than 2 times.

  Further, for example, in the case where three pre-stage injections are set in the operation area before the transition and one pre-injection is set in the operation area after the transition, the predetermined period after the transition of the operation area is This includes holding the number of injections at three times, more than once, and holding it twice. Furthermore, in the case where three pre-stage injections are set in the operation region before the transition and one pre-injection is set in the operation region after the transition, the predetermined period of the pre-injection is changed after the transition of the operation region. The number of times is held at three times, and the number of times of preceding stage injection is held at two times for a predetermined period thereafter, and then the number of times of preceding stage injection is switched to once set in the operation region after the transition. As described above, the number of times may be decreased step by step.

  In particular, this transient control is such that when the fuel injection mode set in the operation region before the transition is compared with the fuel injection mode set in the operation region after the transition, only the number of the previous stage injections is different. It is effective in the case. That is, for example, when the timing of main injection is significantly different before and after the transition of the operation region, or when increasing the number of subsequent injections while reducing the number of front-stage injections, for example, before and after the transition of the operation region, etc. In addition, it is not preferable to apply the above transient control. This is the case when the timing of main injection is significantly different before and after the transition of the operation region, or when the number of subsequent injections is increased while reducing the number of front-stage injections before and after the transition of the operation region. In some cases, the combustion concept in the previous operation region and the combustion concept in the operation region after the transition may be different from each other, and even after the operation region has transitioned, transient control that delays the switching of the fuel injection mode is performed. The reason for this is that there may be inconveniences in terms of combustion stability, combustion noise, exhaust emission, etc. while the switching is delayed.

  Note that the increase / decrease in the number of pre-injections here is particularly the same type of pre-injection, specifically, the increase / decrease in the number of pilot injections, or the increase / decrease in the number of pre-injections. Related to.

The diesel engine further includes an EGR amount control means for adjusting the amount of EGR gas introduced into the cylinder, and the transient control is performed by the EGR amount control means in the EGR amount control means in both the operation region before and after the transition. to run when it is operating region without introducing gas.

  In the transition including the operation region in which the EGR gas is introduced, there are many cases where the change of the fuel injection mode is not only the increase / decrease of the number of times of the pre-stage injection. On the other hand, when the operation region before and after the transition is an operation region where the EGR gas is not introduced, the fuel injection mode may be switched only by increasing or decreasing the number of times of the previous stage injection. It is preferable to apply the transient control described above.

  After the transition to the high load region, the injection control means may hold the number of times of the pre-stage injection at a number greater than a set value for a predetermined cycle period in the same cylinder.

  In other words, the predetermined period in which the number of times of the pre-stage injection is kept higher than the setting may be set to a period that can switch the state in the cylinder to a state corresponding to the operation region after the transition, for example, the temperature of the engine body What is necessary is just to set a predetermined period suitably in the range of several cycles-several hundred cycles according to a state (states, such as whether it is warm or cold).

  The diesel engine different from the above disclosed in the present invention has its injection control means in which the engine body is low during deceleration when the engine body shifts from a relatively high load operation region to a lower load operation region. After shifting to the operating region of the load, transient control is executed for maintaining the number of times of the pre-stage injection at a number smaller than the number of times set in the shifted operating region for a predetermined period.

  At the time of deceleration opposite to the above, after transitioning to the operation region of low load load, the transition for maintaining the number of previous injections at a number smaller than the number of times set in the transitioned operation region for a predetermined period. Execute control. Thus, as in the case of the transient control during acceleration, until the state in the cylinder is switched to a state corresponding to the transitioned operation region, the operation region before the transition can correspond to the operation region before the transition. In order to switch the fuel injection mode to the injection mode corresponding to the operating region after the transition, after waiting for the state in the cylinder to switch, and after the state in the cylinder switches, At the transition transition of the operation region, it is avoided that the state in the cylinder does not correspond to the fuel injection mode, and an increase in combustion noise due to that can be avoided. Further, since the number of pre-injections is increased after the state in the cylinder is switched, the combustion state is stabilized and an increase in combustion noise can be avoided.

  Here, in order to “hold the number of previous stage injections to a number smaller than the number set in the transitioned operation region”, for example, one front stage injection is set in the operation region before transition, and the transition In the case where two previous-stage injections are set in the subsequent operation region, the predetermined period after the transition to the operation region includes holding the number of previous-stage injections to one less than two times, and Similarly, in the case where two pre-stage injections are set in the operation region before the transition and three pre-stage injections are set in the operation region after the transition, the predetermined period is set after the transition of the operation region. , Including maintaining the number of times of the pre-stage injection at two times less than three times.

  Further, for example, in the case where one pre-injection is set in the operation region before the transition and three pre-injections are set in the operation region after the transition, the predetermined period after the transition of the operation region is This includes holding the number of injections at one less than three times, and holding at two times. Furthermore, in the case where one pre-injection is set in the operation region before the transition and three pre-injections are set in the operation region after the transition, the predetermined period of The number of times is held once, and the number of times of preceding stage injection is held twice during a predetermined period thereafter, and then the number of times of preceding stage injection is switched to 3 times set in the operation region after the transition. As described above, the number of times may be increased step by step.

Said transient control is to run when the operating region of the longitudinal migration both of which are operating region not to introduce EGR gas into the cylinder by the EGR quantity control means.

  Further, after the transition to the low load region, the injection control means may hold the number of times of the pre-stage injection at a number smaller than a set number during a predetermined cycle in the same cylinder.

  As described above, according to the above-described diesel engine for mounting on an automobile, at the time of transition of the operation region due to acceleration or deceleration, after shifting the operation region, by delaying the switching of the fuel injection form for a predetermined period, It is possible to avoid a state in which the state in the cylinder does not correspond to the fuel injection form, and avoid instability of the combustion state and increase in combustion noise due to the state.

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 an example of the map of the fuel injection mode of an injector according to the state of a diesel engine. It is a figure which shows an example of the fuel injection form in the area | region A, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region B, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region C, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region D, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region E, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region F, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region G, and an example of the log | history of the heat release rate accompanying it. It is a figure which shows an example of the fuel injection form in the area | region H, and an example of the log | history of the heat release rate accompanying it. It is a flowchart which concerns on the fuel-injection control at the time of the transition transition of an operation area | region. It is a figure explaining the reference | standard range regarding the generation | occurrence | production time of pre combustion.

  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 supplied with fuel mainly composed of light oil, and includes a plurality of cylinders 11a (only one is shown. Here, an in-line four-cylinder engine is used. ), A cylinder head 12 disposed on the cylinder block 11, and an oil pan 13 disposed below the cylinder block 11 and storing lubricating oil. Yes. 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 can be 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 (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 the large and small turbochargers 61 and 62, and an intercooler 35 for cooling 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 51. The exhaust gas recirculation passage 51 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. Yes.

  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.

  The intake passage 30 is connected to a small intake bypass passage 63 that bypasses the small compressor 62a. 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 (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 (normally open) when no power is supplied.

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, and the detection signal of the O ₂ sensor SW6 for detecting an oxygen concentration in the exhaust is input, determines the state of the engine 1 and the vehicle by performing various calculations based on these detection signals, according to this Actuator 18, glow plug 19, valve-operated VVM 71, various valves 36, 51 a, 63 a, 64 a, 65 a The control signal is output to the data.

  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, thereby improving exhaust emission performance and thermal efficiency. I am doing so. On the other hand, in the engine 1, torque is increased by the large and small turbochargers 61 and 62 described above to compensate for a low compression ratio of the geometric compression ratio.

(Outline of engine combustion control)
The basic control of the engine 1 by the PCM 10 mainly determines the target torque (target load) based on the accelerator opening, and controls the operation of the injector 18 based on the fuel injection amount and the injection timing corresponding thereto. It is realized by. Further, the recirculation ratio of the exhaust gas into the cylinder 11a is controlled by controlling the opening degree of the throttle valve 36 and the exhaust gas recirculation valve 51a (external EGR control) and by controlling the VVM 71 (internal EGR control).

  FIG. 3 is a map showing the fuel injection mode of the injector 18 according to the state of the engine when the engine 1 is warm. As shown in FIG. 3, when the engine 1 is warm, the engine 1 has nine A to H (of which the operating range of B is 2) according to the engine speed and the engine load (actual total fuel injection amount). Are present), and a combustion mode is set for each operation region.

  Here, in the regions A, D, and E in FIG. 3 where the load is relatively low and the rotational speed is low, the inside of the cylinder 11a is controlled by controlling the openings of the exhaust gas recirculation valve 51a and the throttle valve 36. A relatively large amount of external EGR gas is introduced to improve exhaust emission (NOx). In combination with the introduction of a large amount of external EGR gas and the low compression ratio of the engine 1 as described above, the ignitability of the fuel is reduced particularly in the cylinder 11a in these operating regions. obtain.

  Hereinafter, the fuel injection mode in each operation region will be described with reference to FIGS. The fuel injection amount and the heat generation rate shown in FIGS. 4 to 11 do not necessarily indicate the relative fuel injection amount or the heat generation rate when these figures are compared with each other. .

  First, FIG. 4 shows an example (lower diagram) of the history of fuel injection in the operating region A (upper diagram) and the associated heat release rate in the cylinder 11a. The operation region A is an operation region that includes an idle region and has a relatively low rotation and a low load. In the fuel injection mode in this region A, during the compression stroke before the compression top dead center, fuel injection (pre-injection) with a relatively large injection amount is executed twice with a predetermined time interval, and compression top dead After the point, main injection with a relatively short pulse width is executed, and thereafter, one fuel injection is executed. Therefore, in this operation region A, a total of four fuel injections are executed.

  FIG. 5 shows an example (lower diagram) of the history of fuel injection in the operating region B (upper diagram) and the associated heat release rate in the cylinder 11a. The operation area B is an operation area on the higher rotation side than the operation area A or an operation area on the higher load side than the operation area A. In this operation region B, two fuel injections (pre-injections) are performed at a relatively short time interval at a timing relatively close to the compression top dead center during the compression stroke, and in the vicinity of the compression top dead center thereafter. The main injection is executed once. That is, in the operation region B, a total of three fuel injections are executed. Execution of pre-injection twice causes pre-combustion (pre-stage combustion) having a sufficient heat generation rate to occur at a predetermined time before compression top dead center, which improves the stability of the subsequent main combustion. At the same time, the increase in the heat generation rate is slowed down. Thus, avoiding the rapid increase in the heat generation rate can be advantageous in reducing combustion noise and improving NVH performance.

  FIG. 6 shows an example (lower diagram) of the history of fuel injection in the operating region C (upper diagram) and the associated heat release rate in the cylinder 11a. The operation area C is an operation area relatively higher than the operation area B and on the relatively high load side. In this operation region C, during the compression stroke, one fuel injection (pre-injection) is executed, and the main injection is executed in the vicinity of the compression top dead center, whereby a total of two fuel injections are executed. The operation region C has a higher rotation speed and a higher load than the operation region B, and a sufficient supercharging amount is obtained and the fuel injection amount is also increased. For this reason, in the operation region C, the in-cylinder temperature is higher and the ignitability of the fuel is improved than in the operation region B. Even if the number of pre-injections is reduced, sufficient heat is obtained as in the operation region B. Pre-combustion having an occurrence rate can occur at a predetermined time before compression top dead center. That is, the pre-injection in each of the regions B and C is set so that the pre-combustion height (heat generation rate) and the peak position thereof are substantially the same in the operation region B and the operation region C. The number of pre-injections is increased or decreased. As a result, also in the operation region C, the stability of the main combustion is increased, and it is possible to avoid the rapid increase in the heat generation rate, which is advantageous in improving the NVH performance.

  As described above, the number of fuel injections increases as the rotation speed of the engine 1 increases and the load of the engine 1 increases as in the operation region B rather than the operation region A and the operation region C than the operation region B. Is set to be less. This is because the higher the engine speed and the higher the load, the more the fuel injection amount increases, which is advantageous for fuel ignition. Therefore, even if the number of fuel injections is reduced, the desired combustion mode is achieved. On the other hand, reducing the number of times of fuel injection improves the fuel injection accuracy and contributes to the improvement of robustness.

  FIG. 7 shows an example (lower diagram) of the history of fuel injection in the operating region D (upper diagram) and the associated heat release rate in the cylinder 11a. The operation region D is a region of relatively high rotation in the region on the low rotation side when the engine speed is divided into the low rotation side and the high rotation side. The operation area D is an example, but is not limited to this, but corresponds to a rotation speed area of about 1600 to 2200 rpm. The operation region D is also a partial load (medium load) region as a load. In this operation region D, two fuel injections are executed during the compression stroke. Among these, the first fuel injection is a pilot injection that is performed relatively far from the compression top dead center, in other words, at a relatively early timing, while the second injection is performed at the compression top dead center. The pre-injection is executed at a close timing. Execution of pilot injection can be advantageous in improving fuel premixing and suppressing soot generation. That is, as described above, the operation region D is introduced with a large amount of external EGR gas and is a low-load region as compared with the operation region E described later, so that the amount of supercharging is also small. It is a disadvantageous state. For this reason, generation | occurrence | production of soot can be suppressed effectively by execution of pilot injection.

  In addition, since the operation region D is introduced with a large amount of external EGR gas as described above, the geometric compression ratio of the engine 1 is reduced in the first place, and the supercharging amount is small. This is a region where the ignitability of the fuel in the cylinder 11a is lowered. Therefore, the combination of pilot injection and pre-injection as pre-injection generates sufficient pre-combustion before main combustion, shortens the ignition delay of fuel injected by main injection in the vicinity of compression top dead center, and The sudden increase in the incidence can be suppressed. This can contribute to the improvement of NVH performance.

  In the operation region D, the post injection (after injection) is executed once after the main injection. This after-injection is fuel injection that is executed during main combustion, in other words, during heat generation by main combustion, and at least part of the fuel spray injected by after-injection is compression top dead center It reaches into the cavity of the piston 14 descending later. Preferably, most of the fuel spray injected by after injection reaches the cavity. This after injection accelerates the main combustion and shortens the afterburn period. That is, the waveform indicated by the solid line in the lower diagram of FIG. 7 is an example of a waveform when executing the after injection, and the waveform indicated by the alternate long and short dash line is an example of a waveform when not performing the after injection, It makes it possible to shorten the combustion period without affecting the rise of the main combustion. This is advantageous for improving the torque and can contribute to improving the fuel efficiency.

  FIG. 8 shows an example (lower diagram) of the history of fuel injection in the operating region E (upper diagram) and the associated heat release rate in the cylinder 11a. The operation region E is a region on the relatively high load side adjacent to the operation region D. Accordingly, the operation region E is a region of relatively high rotation in the region of the low rotation side when the engine 1 is divided into the low rotation side and the high rotation side. This corresponds to the medium load area. In the operation region E, pre-injection is executed once during the compression stroke. Therefore, compared with the operation region D, pilot injection is omitted, and the number of pre-stage injections is reduced. In the operation region E, the supercharging amount is increased due to a relatively high load, the fuel injection amount is relatively large, and the ignitability is improved as compared with the operation region D. Reducing the number of pre-stage injections is advantageous in avoiding a decrease in NVH performance by avoiding an excessive increase in the heat generation rate of pre-combustion due to excessive pre-stage injection. That is, the excessive pre-stage injection generates pre-combustion having a peak of high heat generation rate before main combustion, and two peaks, a high peak of pre-combustion and a peak of main combustion, are generated. This is particularly disadvantageous in terms of low-frequency combustion noise. As described above, omission of pilot injection in the operation region E can improve the NVH performance by suppressing the pre-combustion peak.

  In the operation area E, after the main injection, two after injections of the first after injection and the second after injection are executed. Among these, the first after injection is an injection that is executed at a relatively early timing after the main injection, and, like the after injection in the operation region D, the fuel spray injected by the first after injection. At least a portion reaches the cavity of the piston 14 descending after compression top dead center. The first after-injection is preferably timed so that most of the fuel spray reaches the cavity. As a result, as described above, the main combustion can be promoted, and the combustion period can be shortened (see the one-dot chain line in the lower diagram of FIG. 8).

  On the other hand, the second after injection is an injection executed at a relatively late timing after the first after injection. The second after injection is an injection that is performed at a timing (retarding limit) at which main combustion is continued and at a timing (advance limit) at which fuel spray reaches the outside of the cavity of the descending piston 14. It is. The second after-injection has a function of continuing main combustion, suppressing a decrease in temperature in the cylinder 11a, and maintaining the temperature in the cylinder 11a during the expansion stroke at a high temperature. This promotes soot oxidation in the later stage of combustion.

  That is, in the operation region E, the load is higher than that in the operation region D and the fuel injection amount is increased. On the other hand, the pilot injection is omitted as described above, so that soot is easily generated. 7 and 8, the main injection timing is set to be earlier in the operation region E than in the operation region D from the viewpoint of torque improvement. It is disadvantageous in terms of the occurrence of wrinkles. Furthermore, since the execution of the first after injection is to additionally inject fuel during the main combustion period, this is also disadvantageous in terms of soot generation.

  In contrast, in the second after-injection, as described above, the main combustion is continued to suppress the temperature drop in the cylinder, and the temperature in the cylinder during the expansion stroke is kept at a high temperature. . In other words, in the late combustion stage when the temperature in the cylinder gradually decreases, the time for staying in the OH band in the φ-T map (not shown) is lengthened. Further, since the second after injection is executed at the timing when the fuel spray reaches the outside of the cavity, the utilization rate of the air outside the cavity is increased. Therefore, the combination of maintaining the inside of the cylinder 11a at a high temperature and increasing the utilization rate of the air outside the cavity promotes the oxidation of soot at the later stage of combustion. This can reduce soot discharge as much as possible in the operating region E, which is disadvantageous with respect to soot generation.

  FIG. 9 shows an example (lower diagram) of the history of fuel injection in the operating region F (upper diagram) and the associated heat release rate in the cylinder 11a. The operation region F is a region on the relatively low rotation side in the high load (full load) region. In this operation region F, during the compression stroke, one fuel injection (pre-injection) is executed, and the main injection is divided into two and executed. That is, a total of three fuel injections are performed in this operation region F by performing two main injections of the first main injection near the compression top dead center and the subsequent second main injection. .

  In the operation region F, the fuel injection amount increases because the load is high. However, if a large amount of fuel is supplied into the cylinder by one main injection, the heat generation rate becomes steep and the combustion pressure becomes too high. It can be disadvantageous in terms of combustion noise and thus NVH performance (particularly vibration). In particular, since the engine 1 is equipped with a turbocharger and increases the torque in a high load region, the NVH performance is likely to deteriorate, and the operation region F is a region where the engine speed is relatively low. This is also a disadvantageous situation with respect to NVH performance. Therefore, in the operation region F, the fuel injection amount per time is reduced by dividing the main injection into a plurality of times, here, twice. By this and pre-injection to generate pre-combustion, a rapid increase in the heat generation rate is avoided and an increase in the combustion pressure is suppressed. As a result, it can be advantageous to improve NVH performance. On the other hand, dividing the main injection can be advantageous in terms of improving torque because the main combustion period is lengthened accordingly. As shown in the lower diagram of FIG. 9, the heat generation rate by the first main injection and the heat generation rate by the second main injection become continuous, and their peaks are aligned, so that the main combustion The period is substantially longer. Therefore, both high torque and improved NVH performance can be achieved in the operation region F with high load and relatively low rotation.

  FIG. 10 shows an example (lower diagram) of the history of fuel injection in the operating region G (upper diagram) and the associated heat release rate in the cylinder 11a. The operation region G is a region on the higher rotation side than the operation region F in the high load (full load) region. In this operation region G, a single fuel injection (pilot injection) is performed during the compression stroke, and a main injection is performed once in the vicinity of the compression top dead center. The fuel injection is executed.

  The operation region F is a disadvantageous region for the generation of soot due to an increase in fuel injection amount because the load is high and the rotational speed is high. In addition, it is a region where a supercharging delay can occur during acceleration or the like, and the occurrence of soot can be further disadvantageous. Therefore, by performing the pilot injection as the pre-stage injection, the fuel pre-mixability is improved and advantageous in terms of soot generation, while the number of fuel injection is only two times of the pilot injection and the main injection, A high torque can be secured by sufficiently securing the fuel injection amount during the main injection.

  FIG. 11 shows an example (lower diagram) of the history of fuel injection in the operating region H (upper diagram) and the associated heat generation rate history in the cylinder 11a. The operation region H is a region on the higher rotation side than the operation region G in the high load (full load) region. In this operation region H, the main injection is executed only once near the compression top dead center. That is, in this operating region H, the output is increased and the maximum torque is ensured while improving the robustness.

  In addition, the fuel injection form in each operation area | region mentioned above is an example, and is not limited to this. For example, it is possible to increase / decrease the number of pre-injections, the number of post-injections, and the number of main injections within an appropriate range.

  As described above, the diesel engine 1 is divided into nine operation regions, and different fuel injection modes are set in each operation region.

  Here, as described above, the operation region B in which EGR is not performed and the operation region C have substantially the same heat release rate waveform as can be seen by comparing the lower diagrams of FIGS. 5 and 6. In other words, the operation regions B and C are in accordance with the load so that the heat generation rate waveforms are approximately the same (more precisely, the pre-combustion generation time and the heat generation rate are the same). The number of pre-injections is increased or decreased. Therefore, the number of pre-injections is reduced from two to one when shifting from the low load operation region B to the high load operation region C as the vehicle accelerates. The same is true when the operation region B is shifted from the operation region B having a relatively low rotation speed.

  Conversely, when the vehicle is decelerated, the fuel injection mode is also switched when the operation region C, which has a relatively high load, is shifted to the operation region B, which has a relatively low load. The number of times increases from once to twice. The same applies when the operation region C is shifted to the operation region B having a relatively low rotational speed.

  Here, at the transition transition of the operation region, the state in the cylinder is less responsive than the transition of the operation region determined by the rotation speed and the load. The state inside may correspond to the state of operation before the transition. In this case, if the fuel injection mode is switched simultaneously with the shift of the operation region, the state in the cylinder and the fuel injection mode do not correspond to each other. As a result, for example, when the operation region B is shifted from the relatively low load operation region B to the relatively high load operation region C, the state in the cylinder is relatively low as in the operation region B. Despite this, pre-injection with a sufficient heat generation rate can be generated at a predetermined timing by reducing the number of pre-injections to one as set for the operation region C. In the case where the main combustion becomes unstable, or conversely, the operation region C shifts from the relatively high load operation region C to the relatively low load operation region B, the state in the cylinder is changed to the operation region C. In spite of the relatively high ignitability as described above, by increasing the number of pre-injections to 2 as set for the operation region B, excessive pre-combustion occurs, Combustion noise will worsen.

  Therefore, in order to solve such a problem, the diesel engine 1 (PCM 10) performs predetermined transient control related to fuel injection at the transition transition of the operation region between the operation region B and the operation region C. Next, the transient control executed by the PCM 10 will be described with reference to the flowchart shown in FIG. This flow is related to when the engine 1 is in the operation region B or the operation region C and when the engine 1 is moving between the operation region B and the operation region C, and when the engine 1 is in an operation region other than the operation regions B and C. This is not executed when the operation region B or C is shifted to an operation region other than the operation regions B and C.

  In the flowchart of FIG. 12, in step S1 after the start, the engine torque four cycles before and the current engine speed are read, and a pre-injection pattern A is set based on the read engine torque. Here, since the engine 1 is a four-cylinder engine, four cycles before, that is, the cylinder is based on the torque at the previous time. The pre-injection pattern A corresponds to the number of pre-injections. In step S1, the pre-injection pattern A (pre-injection is one time) corresponding to the fuel injection mode in the operation region B shown in the upper diagram of FIG. And any one of the pre-injection patterns A (pre-injection is 2 times) corresponding to the fuel injection mode in the operation region C shown in the upper diagram of FIG. 6 is selectively set.

  In the subsequent step S2, it is determined whether or not the pre-injection pattern A (the number of pre-injections) set in step S1 is the same as the previous pre-injection pattern B (the number of pre-injections). On the other hand, the process proceeds to S3, and if different, the process proceeds to Step S5.

  In step S3, the current pre-injection pattern A is input to the pre-injection pattern B (pre-injection pattern B = pre-injection pattern A), and in the subsequent step S4, the torque four cycles before and the current engine speed are The total fuel injection amount and the injection timing in the set pre-injection pattern (fuel injection form) are respectively calculated. Then, fuel injection is executed according to the set fuel injection mode, injection timing, and injection amount. When the flow reaches from step S2 and step S3 to step S4, the pre-injection pattern does not change, and thus the vehicle and the engine are in steady operation in the operation region B or the operation region C.

  On the other hand, in step S5, which has been shifted in step S2 because the pre-injection pattern B and the pre-injection pattern A are different, the number of pre-injections of the pre-injection pattern A set this time and the pre-injection of the previous pre-injection pattern B The number of times of the pre-injection pattern A is compared with the number of times, and it is determined whether or not the number of times of the pre-injection pattern B is smaller than the number of times of the pre-injection pattern B. When the number of pre-injection patterns A is smaller than the number of pre-injection patterns B (YES), the process proceeds to step S6. This is because the fuel injection mode is changed from the two-injection pre-injection mode (pre-injection pattern B) shown in FIG. 5 to the one-injection mode (pre-injection pattern A) shown in FIG. This corresponds to the acceleration when the operation region of the engine 1 shifts from the operation region B to the operation region C.

  On the other hand, when the number of pre-injection patterns A is greater than or equal to the number of pre-injection patterns B in step S5 (NO), the process proceeds to step S9. This is because the fuel injection mode is changed from a single injection mode (pre-injection pattern B) shown in FIG. 6 to a two-time injection mode (pre-injection pattern A) shown in FIG. This corresponds to the time of deceleration when the operation region of the engine 1 shifts from the operation region C to the operation region B.

In step S6 during acceleration, the timing at which pre-combustion occurs when pre-injection pattern B-1 is performed, in this case, one pre-injection is performed by subtracting 1 from two pre-injections in operation region B. Is estimated using a preset model. The model used for estimation here is, for example, all or all of in-cylinder temperature, fuel cetane number, in-cylinder pressure, fuel injection pressure, in-cylinder O ₂ concentration, engine speed, engine water temperature, and engine oil temperature. A model that estimates the ignition delay of the fuel based on a part may be used.

  In subsequent step S7, it is determined whether or not the pre-combustion occurrence timing estimated in step S6 is within the reference range in advance. As shown in FIG. 13, the reference range here may be set as a predetermined period centered on the target timing of pre-combustion before compression top dead center. The target timing of pre-combustion is, for example, BTDC 5 ° CA. The reference range may be set to ± 5 ° CA. The determination in step S7 corresponds to the time of acceleration, and the state in the cylinder is a transition from a relatively low ignitability state to a high ignitability state, so the number of pre-injections is reduced to one. However, it is determined whether or not the pre-combustion can be generated without delay. That is, in this flow, whether or not the state in the cylinder 11a has changed to a state corresponding to the operation region after the transition (here, the operation region C and the operation region B in step S10 described later). Estimated using a model.

  In step S7, when the pre-combustion cannot be generated within the reference range, that is, when the pre-combustion is delayed from the reference range (in the case of NO), the state in the cylinder 11a is Assuming that the state corresponding to the operation region C after the transition has not been changed yet, the process proceeds to step S4 as it is, and the pre-injection pattern is not changed as it was last time (here, remains twice), and the engine torque is changed. And the total injection amount and the injection timing are set from the rotation speed. This means that the number of pre-injections can be set in the operation region C even after the operation region B is shifted to the operation region C (NO in step S2) with changes in the engine torque (load) and / or engine speed. In this case, the number of times is held more than the number of times set in (1).

  On the other hand, when pre-combustion can be generated within the reference range in step S7 (in the case of YES), it is assumed that the state in the cylinder 11a has changed to a state corresponding to the operation region C after the transition. , The pre-injection pattern B is changed to pre-injection pattern B-1 times (here, it is changed from 2 times to 1 time). Therefore, the number of pre-injections is switched to the number (one time) set in the operation region B after the transition. Thereafter, the flow proceeds to step S4, and the total injection amount and the injection timing are set from the engine torque and the rotational speed.

  In step S9 during deceleration, the pre-injection pattern B + 1 times, here, the timing at which pre-combustion occurs when two pre-injections are performed by adding 1 to the number of pre-injections in the operation region C, Estimation is performed using the above model.

  In subsequent step S10, it is determined whether or not the pre-combustion occurrence timing estimated in step S9 is within the reference range in advance. Here, it corresponds to the time of deceleration, and the state in the cylinder is a transition from a relatively high ignitability state to a low ignitability state, so even if the number of pre-injections is increased to 2, It is determined whether or not the pre-combustion can be generated without being too early.

  In step S10, when the pre-combustion cannot be generated within the reference range, that is, when the pre-combustion occurs earlier than the reference range (in the case of NO), the state in the cylinder 11a is Assuming that the state corresponding to the operation region B after the transition has not been changed yet, the process proceeds to step S4 as it is, and the pre-injection pattern is not changed as it was last time (here, once), The total injection amount and injection timing are set from the engine torque and the rotational speed. This means that the number of pre-injections can be set in the operation region B even after the operation region C is shifted from the operation region C to the operation region B (NO in step S2) with changes in engine torque (load) and / or engine speed. The number of times is less than the number of times set in (2).

  On the other hand, when pre-combustion can be generated within the reference range in step S10 (in the case of YES), it is determined that the state in the cylinder 11a has changed to a state corresponding to the operation region B after the transition to step S11. Then, the pre-injection pattern B is changed to the pre-injection pattern B + 1 times (here, changed from once to twice). Therefore, the number of pre-injections is switched to the number (two times) set in the operation region B after the transition. Thereafter, the flow proceeds to step S4, and the total injection amount and the injection timing are set from the engine torque and the rotational speed.

  As described above, at the time of acceleration when the diesel engine 1 shifts from the operation region B to the operation region C, the number of pre-combustions is set once in the operation region C for a predetermined period after the shift to the operation region C. Hold twice more than. In other words, the number of times set in the operation region B before the transition is held. This waits for the state in the cylinder 11a to switch to a state corresponding to the operation region C after the transition to the operation region C, and fuel injection after the state in the cylinder 11a is switched. The form will be switched. As a result, it is possible to avoid a state in which the state in the cylinder 11a does not correspond to the fuel injection mode at the time of acceleration, and instability of combustion resulting from that can be avoided. Further, after the state in the cylinder 11a is switched to the state corresponding to the operation region C, the number of pre-injections is reduced, so that an increase in combustion noise can be avoided.

  On the contrary, at the time of deceleration from the operation region C to the operation region B of the diesel engine 1, the number of pre-combustions is set in the operation region B for a predetermined period after the transition to the operation region B. Hold once less than twice. In other words, the number of times set in the operation region C before the transition is held. This waits for the state in the cylinder 11a to switch to the state corresponding to the operation region B after the transition to the operation region B, and fuel injection after the state in the cylinder 11a is switched. The form will be switched. As a result, it is avoided that the state in the cylinder 11a does not correspond to the fuel injection mode at the time of deceleration, and it is possible to avoid unstable combustion and increase in combustion noise due to that.

  Here, as described above, the operation region B and the operation region C are regions where EGR is not performed, only the number of pre-injections is different, and the combustion concepts are the same. For this reason, even if the pre-combustion is performed once in the operation region B as in the operation region C, or the pre-combustion is performed twice in the operation region C as in the operation region B, combustion stability, combustion sound, Inconvenience hardly occurs from the viewpoint of exhaust emission. That is, the transient control is particularly effective at the time of transition between the operation region B and the operation region C.

  In the flow shown in FIG. 12, the fuel injection mode switching timing is set based on whether or not the pre-combustion generation timing estimated using the model falls within the reference range. Specifically, according to the temperature state of the engine 1, the predetermined period after the shift of the operation region is a period of about several cycles in the same cylinder if it is warm, and hundreds if it is cold. The period is about several hundred cycles. Therefore, instead of steps S6 and S7 in the above flow, the fuel injection mode may be switched after waiting for a predetermined period based on the number of cycles set in advance according to the temperature state of the engine 1.

  In the above configuration, the number of pre-injections is changed from 2 to 1 or the number of pre-injections is changed from 1 to 2, but for example, the number of pre-injections is set to 3 times. When such an operation region is included, when the operation region is shifted, the number of pre-injections may be changed from 3 times to 2 times or may be changed from 2 times to 3 times. In this case, the same transient control as described above can be performed.

  In addition, when the operation area is set such that the number of pre-injections is set to 3 times, the pre-injection number is changed from 3 times to 1 time or changed from 1 time to 3 times with the shift of the operation area. Or you can happen. For example, when the number of pre-injections is changed from three to one, after the transition of the operation region, the number of pre-injections is held twice more than once after the transition for a predetermined period. It may be performed once corresponding to the operation region. Conversely, even when the pre-injection count is changed from 1 to 3 with the shift of the operation region, the pre-injection count is set to 2 times less than the post-transfer 3 times after the shift of the operation region. It may be held three times and then three times corresponding to the operation region after the transition.

  In addition, when changing the number of pre-injections from 3 times to 1 time, after the transition to the operation region, the number of pre-injections is kept at 3 times for a predetermined period, and then the number of pre-injections is set to 2 times. Alternatively, the number of pre-injections may be reduced stepwise so that the number of pre-injections is held once only after a predetermined period. Conversely, when changing the number of pre-injections from 1 to 3 with the transition of the operation region, after the transition of the operation region, the number of pre-injections is held once for a predetermined period, and then the pre-injection It is also possible to increase the number of times step by step so that the number of times is set to 2 and held for a predetermined period, and then the number of pre-injections is set to 3. Such control for increasing or decreasing the number of pre-injections stepwise can apply the flow shown in FIG. 12 as it is.

1 Diesel engine (engine body)
10 PCM (injection control means, EGR amount control means)
11a Cylinder 18 injector (fuel injection valve)
51a Exhaust gas recirculation valve (EGR amount control means)

Claims (4)

An engine body mounted on a vehicle and supplied with fuel mainly composed of light oil;
A fuel injection valve that faces the cylinder of the engine body and directly injects the fuel into the cylinder;
Injection control means for controlling the injection mode of the fuel into the cylinder through the fuel injection valve;
EGR amount control means for adjusting the amount of EGR gas introduced into the cylinder ,
The injection control means includes a main injection that injects fuel in the vicinity of compression top dead center to perform main combustion mainly consisting of diffusion combustion, and a pre-stage where the heat generation rate reaches a peak at a predetermined time before the compression top dead center. At least one pre-injection in which fuel is injected before the main injection is performed so that combustion occurs, and the number of executions of the pre-injection is less in an operation region where the load of the engine body is higher Set the number of times,
The injection control means also has a predetermined period after the transition to the high load operation region during acceleration when the engine body shifts from a relatively low load operation region to a higher load operation region. The transient control is performed to maintain the number of times of the pre-stage injection at a number greater than the number set in the transitioned operation region ,
The transient control at the time of acceleration is an on-vehicle diesel engine that is executed when both the operation region before and after the transition is an operation region in which EGR gas is not introduced into the cylinder by the EGR amount control means . The on-board diesel engine according to claim 1 ,
After the transition to the high load region, the injection control means is an on-vehicle diesel engine that maintains the number of times of the pre-stage injection at a number greater than the set number only during a predetermined cycle in the same cylinder. An engine body mounted on a vehicle and supplied with fuel mainly composed of light oil;
A fuel injection valve that faces the cylinder of the engine body and directly injects the fuel into the cylinder;
Injection control means for controlling the injection mode of the fuel into the cylinder through the fuel injection valve;
EGR amount control means for adjusting the amount of EGR gas introduced into the cylinder ,
The injection control means includes a main injection that injects fuel in the vicinity of compression top dead center to perform main combustion mainly consisting of diffusion combustion, and a pre-stage where the heat generation rate reaches a peak at a predetermined time before the compression top dead center. At least one pre-injection in which fuel is injected before the main injection is performed so that combustion occurs, and the number of executions of the pre-injection is less in an operation region where the load of the engine body is higher Set the number of times,
The injection control means also has a predetermined period after the engine main body shifts to the low load operation region during deceleration when the engine body shifts from a relatively high load operation region to a lower load operation region. Performing the transient control to keep the number of times of the preceding stage injection at a number smaller than the number of times set in the shifted operation region ,
The transient control at the time of deceleration is an on-vehicle diesel engine that is executed when both the operation region before and after the transition is an operation region in which EGR gas is not introduced into the cylinder by the EGR amount control means . The on-board diesel engine according to claim 3 ,
After the transition to the low load region, the injection control means is an on-vehicle diesel engine that keeps the number of times of the preceding stage injection less than the set number only for a predetermined cycle in the same cylinder.

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