JP4352901B2 - Start-up control device for compression ignition internal combustion engine - Google Patents

Description

  The present invention relates to a start control device for a compression ignition internal combustion engine and a start control method thereof.

  In a compression ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine”), the fuel injection timing is controlled after the warm-up is completed, whereby NOx reduction in exhaust gas or exhaust purification by an exhaust purification catalyst may be performed. .

  However, when an internal combustion engine in a low temperature state is started, the temperature in the cylinder is relatively low, and the viscosity of the lubricating oil in the internal combustion engine is relatively high, so that the friction torque in the internal combustion engine increases. For this reason, even if fuel injection is performed at the same time as when the warm-up is completed, it is difficult to achieve exhaust purification or the like in the same manner. In some situations, the time required for warming up the internal combustion engine may be prolonged.

Therefore, based on the cooling water temperature of the internal combustion engine, the fuel injection timing is divided into a period until the internal combustion engine is started and the warm-up state is reached, and a period after the warm-up state is reached, and the fuel injection timing is switched. A technique for performing control is disclosed (for example, refer to Patent Document 1). Thereby, before and after the completion of warm-up of the internal combustion engine, fuel injection corresponding to each time is possible.
JP 2000-8930 A JP 54-137524 A JP 2002-38995 A JP-A-8-296477 Japanese Patent Laid-Open No. 10-103129

  When the internal combustion engine is started, particularly when the engine is started in an extremely low temperature state where the outside air temperature is below zero, the temperature in the cylinder is relatively low, so the ignitability of the fuel is reduced. As a result, combustion at engine startup becomes unstable, and the time required for engine startup increases, so that there is a possibility that the amount of fuel consumption increases and emission such as generation of white smoke deteriorates.

  Further, since the lubricating oil temperature of the internal combustion engine is also low, the viscosity of the lubricating oil becomes relatively high, and the friction torque in the internal combustion engine increases. Therefore, when the generation efficiency of the output torque due to combustion is low, the increase in fuel consumption at the time of starting the engine becomes significant.

  In the present invention, in view of the above-described problems, when the compression ignition internal combustion engine is started, the fuel consumption required for starting the engine is suppressed and the combustion at the start of the engine is stabilized to suppress the deterioration of the emission.

In the present invention, in order to solve the above-described problem, the combustion in the cylinder is performed during a period in which the temperature in the cylinder after the start of the engine is low after the engine start of the internal combustion engine is started until the engine start is completed. The fuel injection timing is controlled so that the fuel injection is performed relatively stably, and the fuel injection is shifted to the retarded side from the previous injection timing when the temperature in the cylinder has risen relatively after the engine start has started. By doing so, the fuel is injected at a time when the generation efficiency of the output torque by combustion is increased.

  Therefore, the present invention provides an engine start control device for starting an internal combustion engine at a first ignition timing that is near the top dead center of the compression stroke of the compression ignition internal combustion engine and at which the cylinder temperature reaches a stable combustion temperature. A first fuel injection means for injecting fuel at a first fuel injection timing at which fuel ignition is started in the cylinder, and a second ignition timing in the expansion stroke that is retarded from the first ignition timing. Second fuel injection means for injecting fuel at the second fuel injection timing at which fuel ignition starts, and fuel injection by the first fuel injection means for a predetermined period from the start of engine start of the compression ignition internal combustion engine Engine start control means for increasing the engine rotation speed of the compression ignition internal combustion engine to a start completion rotation speed by performing fuel injection by the second fuel injection means after the predetermined period has elapsed.

  Here, the fuel injection by the first fuel injection means is a fuel injection that is performed at an injection timing that places importance on the ignitability of fuel and the stability of combustion in the cylinder. In other words, in order to ignite the injected fuel at the first ignition timing, which is the timing near the top dead center of the compression stroke and the temperature in the cylinder rises due to the compression operation of the piston, the fuel is injected at the timing before the first ignition timing. Injection is performed. Accordingly, the first fuel injection timing is preferably the time when the temperature in the cylinder rises most due to the compression operation of the piston. Thereby, the evaporability of the fuel injected into the cylinder is promoted, and the ignitability of the fuel and the stability of combustion in the cylinder are improved.

  On the other hand, since the piston is close to the top dead center of the compression stroke, the heat energy generated by the combustion in the cylinder is difficult to be transmitted to the output shaft of the internal combustion engine via the piston, so that the internal combustion engine such as a cylinder is warmed up. A lot of thermal energy is used. As a result, when the engine of the internal combustion engine is started only by fuel injection by the first fuel injection means, the engine rotational speed of the internal combustion engine stably increases and reaches the start completion rotational speed, but the time until the arrival Will be prolonged.

  The start completion rotation speed is an engine rotation speed at which it is determined that the engine rotation speed is increased and the engine start is completed when the internal combustion engine is started. Therefore, after the engine rotation speed reaches the start completion rotation speed, the internal combustion engine enters a so-called idle operation state.

  The fuel injection by the second fuel injection means is fuel injection performed at an injection timing at which thermal energy generated by combustion in the cylinder contributes to the output torque of the internal combustion engine with a relatively high efficiency. That is, when the fuel burns at the second ignition timing when the piston position is lower than the position of the top dead center of the compression stroke during the expansion stroke on the retarded angle side from the first ignition timing, The piston is pushed out efficiently, leading to the output torque. Then, fuel injection is performed so that the injected fuel is ignited at the second ignition timing. Therefore, the second fuel injection timing is preferably the time when the output torque is maximum. Thereby, the output torque of an internal combustion engine can be exhibited efficiently.

  On the other hand, since the fuel is ignited at the second ignition timing when the piston position is lower than the compression stroke top dead center position, the temperature in the cylinder due to the compression operation of the piston is the first ignition timing at the second ignition timing. Lower than the temperature inside the cylinder. Accordingly, combustion in the cylinder at the second ignition timing becomes more unstable. In particular, when the engine is started at an extremely low temperature, the instability of combustion in the cylinder becomes remarkable. As a result, when the internal combustion engine is started only by fuel injection by the second fuel injection means, the engine rotational speed is increased to the start completion rotational speed in a short time, but the fluctuation of the engine rotational speed at the time of engine startup Even after the start completion rotational speed is reached, the engine rotational speed varies greatly and the engine rotational speed is not stable.

  Therefore, the engine start control means performs fuel injection by the first fuel injection means during the predetermined period, and after the predetermined period has elapsed, performs fuel injection by the second fuel injection means. That is, immediately after the start of the engine of the internal combustion engine and at a time when the temperature of the engine element of the internal combustion engine such as a cylinder is relatively low, fuel injection by the first fuel injection means is performed first. In particular, priority is given to the temperature rise in the cylinder where combustion takes place. After the temperature in the cylinder rises to some extent, even if fuel is ignited at the second ignition timing, the temperature in the cylinder is relatively high, so that there is little risk of unstable combustion.

  Therefore, the predetermined period means that the fuel injection by the first fuel injection means is necessary until the temperature in the cylinder reaches a temperature at which the fuel injected by the second fuel means can be combusted relatively stably in the cylinder. Refers to the period.

  Therefore, when the engine start control device for the internal combustion engine further includes an in-cylinder temperature detection means for detecting or estimating the in-cylinder temperature, the predetermined period is from the start of the engine start of the compression ignition internal combustion engine to the cylinder. It is good also as a period until the cylinder temperature detected or estimated by the internal temperature detection means exceeds a predetermined cylinder temperature. The predetermined in-cylinder temperature mentioned here is synonymous with the above-mentioned “temperature at which the fuel injected by the second fuel means can be combusted relatively stably in the cylinder”. The in-cylinder temperature detecting means may estimate the temperature in the cylinder from the cooling water temperature and exhaust temperature of the internal combustion engine, the time during which fuel injection by the first fuel injection means is performed, and the like.

  In addition, the relationship between the intake air temperature (outside air temperature) and the temperature at which the fuel injected by the second fuel means can be combusted relatively stably in the cylinder is measured in advance through experiments or the like. The predetermined period may be calculated from

  As described above, the engine start control means performs the fuel injection by the first fuel injection means for a predetermined period, and then performs the fuel injection by the second fuel injection means, thereby increasing the in-cylinder temperature more efficiently. Torque can be efficiently exhibited. As a result, it is possible to further shorten the time required for starting the engine, thereby suppressing fuel consumption required for starting the engine and stabilizing combustion at the time of starting the engine, thereby suppressing deterioration of emissions.

  Here, in the internal combustion engine start control device described above, a combustion stable state determination for determining a combustion stable state in the cylinder when the engine start control unit performs fuel injection by the second fuel injection unit. And a temperature correcting means for correcting the in-cylinder temperature detected or estimated by the in-cylinder temperature detecting means or the predetermined in-cylinder temperature based on the combustion stable state determined by the combustion stable state determining means. And may be further provided.

  As described above, when the fuel injection is performed by the second fuel injection means, the contribution to the rise in the cylinder temperature due to the compression operation of the piston is small, so the combustion is performed when the outside air temperature is extremely low or the cylinder temperature is low. There is a risk that the combustion state of the fuel injected by the second fuel injection means may become unstable for some reason, such as when energy tends to flow out. Here, the stable combustion state is determined in accordance with the operating state of the internal combustion engine that can be permitted when the internal combustion engine is started. For example, if a relatively small fluctuation in engine speed is not allowed when starting the internal combustion engine, combustion is unstable when fluctuations greater than the allowable fluctuation in engine speed appear. judge. In addition, if the engine speed is allowed to be relatively small, but the combustion state is not allowed to become misfired, the engine speed changes corresponding to the misfire condition, resulting in unstable combustion. It is determined that the current condition is

  And it is determined by the combustion stable state determination means whether the combustion state of the fuel injected by the second fuel injection means is unstable. If the combustion state is determined to be unstable, it means that the in-cylinder temperature is relatively low because the increase in the in-cylinder temperature during fuel injection by the first fuel injection means is small. Therefore, the temperature correction by the temperature correction means is such that the in-cylinder temperature detection means corrects or estimates the in-cylinder temperature to a low temperature side or increases the fuel injection time by the first fuel injection means. Correct the temperature to the high temperature side.

  In other words, the predetermined period is changed to a longer period so that the fuel injection time by the first fuel injection means becomes longer. Thereby, when the fuel injection by the first fuel injection means is performed at the time of engine start of the internal combustion engine, the switching to the fuel injection by the second fuel injection means is performed more appropriately, and therefore the fuel by the second fuel injection means It is possible to prevent the combustion state from becoming unstable when injection is being performed and increasing the time required to start the engine.

  Further, the fact that the combustion state is determined to be stable by the combustion stable state determination means means that the increase in the in-cylinder temperature in the fuel injection by the first fuel injection means is sufficient, while the first fuel injection In some cases, the time required for starting the engine is unnecessarily long because the fuel injection time by the means, that is, the predetermined period is long. Therefore, the temperature correction by the temperature correction means corrects the in-cylinder temperature detected by the in-cylinder temperature detection means or corrects the estimated in-cylinder temperature so as to shorten the fuel injection time by the first fuel injection means, Correct the temperature to the low temperature side.

  In other words, the predetermined period is changed to a shorter period in order to shorten the fuel injection time by the first fuel injection means. As a result, when the fuel injection by the first fuel injection means is performed again when the internal combustion engine is started, the switching to the fuel injection by the second fuel injection means is performed more appropriately, and therefore by the first fuel injection means. It is possible to suppress an increase in the time required for starting the engine due to an unnecessarily long time during which fuel injection is performed.

  Here, in the above-described internal combustion engine start control device, the combustion stability determining means includes the pressure in the cylinder, the temperature of the exhaust gas discharged from the compression ignition internal combustion engine, and the engine speed of the compression ignition internal combustion engine. The stable combustion state in the cylinder may be determined based on at least one of them. That is, the stability is determined based on the in-cylinder pressure, the exhaust gas temperature, and the engine speed related to the stability of combustion in the cylinder. For example, when the in-cylinder combustion becomes unstable, the in-cylinder pressure greatly decreases, the exhaust temperature shifts to a lower temperature, and the engine rotation speed decreases than in a stable state. It is possible to determine the stability of combustion based on fluctuations in these values.

  In addition, the present invention for solving the above-described problem is, in other words, the predetermined period from the start of the engine start of the compression ignition internal combustion engine is a time near the top dead center of the compression stroke, and the in-cylinder temperature becomes the stable combustion temperature. The fuel is injected at the first fuel injection timing at which fuel ignition is started in the cylinder at the first ignition timing, and after the predetermined period has elapsed, the fuel is in the expansion stroke on the retard side from the first fuel injection timing. Start of a compression ignition internal combustion engine that performs fuel injection at a second fuel injection timing at which fuel ignition is started in the cylinder at the second ignition timing, and increases the engine rotation speed of the compression ignition internal combustion engine to a start completion rotation speed It is a control method.

  The predetermined period, the first ignition timing, the first fuel injection timing, the second ignition timing, and the second fuel injection timing in the start-up control of the compression ignition internal combustion engine are as described above. As a result, the time required for starting the engine can be further shortened, thereby suppressing the fuel consumption required for starting the engine and stabilizing the combustion at the time of starting the engine, thereby suppressing the deterioration of the emission.

  In the start-up control device and start-up control method for a compression ignition internal combustion engine according to the present invention, at the time of engine start of the compression ignition internal combustion engine, fuel consumption required for engine start is suppressed and combustion at engine start is stabilized. It becomes possible to suppress the deterioration of emissions.

  Here, an embodiment of a start control device and a start control method for a compression ignition internal combustion engine according to the present invention will be described based on the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a compression ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 and its control system to which the present invention is applied. The internal combustion engine 1 includes a fuel injection valve 3 capable of directly injecting fuel into the cylinder 2. In the cylinder 2, the piston 4 reciprocates. The internal combustion engine 1 has an intake passage connected to a combustion chamber via an intake port 7. Similarly, an exhaust passage is connected to the combustion chamber through the exhaust port 8 in the internal combustion engine 1. Here, an intake valve 5 is provided between the intake port 7 and the combustion chamber, and an exhaust valve 6 is provided between the exhaust port 8 and the combustion chamber.

  The internal combustion engine 1 is also provided with an electronic control unit (hereinafter referred to as “ECU”) 10 for controlling the internal combustion engine 1. In addition to the CPU, the ECU 10 includes a ROM, a RAM, and the like that store various control routines and maps, which will be described later. The unit to control. Here, the fuel injection valve 3 performs an opening / closing operation according to a control signal from the ECU 10.

  Further, an ignition switch 11 for the internal combustion engine 1, a water temperature sensor 12 for detecting the cooling water temperature Thw of the internal combustion engine 1, and an exhaust temperature sensor 14 for detecting the temperature of the exhaust gas flowing into the exhaust passage through the exhaust port 8 are connected to the ECU 10. Electrically connected. Thus, the ECU 10 receives the engine start command I / G, the coolant temperature Thw, and the exhaust gas temperature Thex to the internal combustion engine 1, respectively. The crank position sensor 13 is electrically connected to the ECU 10. Thereby, the ECU 10 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1 and calculates the engine rotational speed Ne and the like of the internal combustion engine 1.

  Here, the ignition timing of the fuel in the cylinder 2 will be described based on FIG. FIG. 2 is a graph showing the relationship between the fuel ignition timing, the temperature in the cylinder 2 and the output torque of the internal combustion engine 1. The horizontal axis of FIG. 2 represents the crank angle of the internal combustion engine 1, and TDC in the figure means the top dead center of the compression process. The vertical axis is a value corresponding to each of changes in temperature, output torque, and cooling loss in combustion in the cylinder 2 with respect to the crank angle represented by the lines L1, L2, and L3 in FIG. .

  A period ΔT1 in FIG. 2 is a period in the vicinity of the compression stroke top dead center TDC. In the period ΔT1, when the fuel for starting the engine is injected into the cylinder 2 from the fuel injection valve 3, the temperature in the cylinder 2 exceeds the stable combustion temperature as indicated by the line L1. That is, the air-fuel mixture in the cylinder 2 is compressed by the compression operation of the piston 4 and the temperature in the cylinder 2 exceeds the stable combustion temperature, so that the fuel is easily ignited and stably combusted.

  On the other hand, as represented by the line L3, the cooling loss in combustion is relatively high in the period ΔT1. This is because during the period ΔT1, since the piston is relatively close to the top dead center TDC of the compression stroke, the heat energy generated in the cylinder 2 does not become a force for efficiently pushing out the piston, most of which is in the cylinder 2 This is because it is consumed as energy for warming up the engine elements of the internal combustion engine 1.

  In other words, the ignition and combustion of the fuel in the period ΔT1 is the ignition and combustion of the fuel at a more suitable time from the viewpoint of the ignitability of the fuel and the stability of the combustion state. From the viewpoint of the efficiency of increasing the rotational speed, it is relatively low acceleration and low efficiency fuel ignition and combustion. Therefore, hereinafter, the fuel ignition timing in the period ΔT1 is referred to as the first ignition timing, and the fuel injection from the fuel injection valve 3 that enables the fuel ignition at the first ignition timing is referred to as the warm-up mode fuel injection. For example, the timing at which the warm-up mode fuel injection is performed may be any timing in the period ΔT1, and if the injected fuel is ignited at the first ignition timing, it may be at the timing of the intake stroke, the middle of the compression stroke, or the like. There may be a time when a so-called premixed gas can be formed in the cylinder 2.

  Further, a period ΔT2 in FIG. 2 is a period that is retarded from the period ΔT1. In the period ΔT2, when fuel for starting the engine is injected into the cylinder 2 from the fuel injection valve 3, when the fuel is ignited and burned in the cylinder 2 as represented by the line L2, The output torque of the internal combustion engine 1 generally peaks. That is, since the position of the piston 4 is lower than the top dead center TDC of the compression stroke, the heat energy generated in the cylinder 2 becomes a force for efficiently pushing out the piston. Therefore, as represented by the line L3, the cooling loss in combustion is relatively low in the period ΔT2.

  On the other hand, since the position of the piston 4 is lower than the compression stroke top dead center TDC, as indicated by the line L1, the temperature in the cylinder 2 due to the compression operation becomes lower than that in the period ΔT1. As a result, the ignitability of the fuel in the cylinder 2 may be reduced and combustion may become unstable. In particular, when the temperature of the air-fuel mixture formed in the cylinder 2 is low or the temperature of the air-fuel mixture formed in the cylinder 2 is low, or when the engine is started at an extremely low temperature when the temperature of the cylinder 2 is low and combustion energy tends to flow out, Qualification may interfere with engine startup. As a result, there is a possibility that the engine rotational speed at the time of starting the engine is not stable.

  In other words, the ignition and combustion of the fuel in the period ΔT2 is relatively high acceleration and high efficiency fuel ignition and combustion from the viewpoint of acceleration of the internal combustion engine, that is, efficiency of increase in engine rotation speed. However, from the viewpoint of the ignitability of the fuel and the stability of the combustion state, this is the ignition and combustion of the fuel at a time when the combustion tends to become unstable. Therefore, hereinafter, the fuel ignition timing in the period ΔT2 is referred to as second ignition timing, and the fuel injection from the fuel injection valve 3 that enables fuel ignition at the second ignition timing is referred to as acceleration mode fuel injection. For example, the time at which the acceleration mode fuel injection is performed may be any time in the period ΔT2, and if the injected fuel is ignited at the second ignition time, the period ΔT2 is reached after the time ΔT1 has elapsed. It may be time until. In addition, when performing acceleration mode fuel injection, it is preferable not to perform warm-up mode fuel injection. This is because the fuel by the warm-up mode fuel injection may ignite and burn at a time earlier than the period ΔT2 due to the combustion of the fuel by the warm-up mode fuel injection.

  As described above, at the time of starting the internal combustion engine, that is, during the period from the start of cranking in the internal combustion engine 1 until the engine speed increases to the start completion rotational speed, either warm-up mode fuel injection or acceleration mode fuel injection is performed. If only this is performed, problems such as prolonged engine start-up time due to low acceleration, difficulty in ignition of fuel, instability of engine speed due to instability of combustion, and the like arise. Therefore, when the internal combustion engine 1 is started, fuel injection control (hereinafter referred to as “engine start control”) shown in FIG. 3 is performed. 3 is a routine that is executed when the internal combustion engine 1 is started. Also, FIG. 4 shows the transition of the engine speed when the engine start control shown in FIG. 3 is performed (represented by the line L4 in FIG. 4) and the transition of the temperature in the cylinder 2 (the line L5 in FIG. 4). Represented). The horizontal axis in FIG. 4 represents time, and the vertical axis represents the engine rotational speed fuel injection amount.

In S101, it is determined whether or not an engine start command I / G is issued from the ignition switch 11. If it is determined that the engine start command I / G is issued from the ignition switch 11, the process proceeds to S102. If it is determined that the engine start command I / G is not issued from the ignition switch 11, the process of S101 is performed again.

  In S102, it is determined whether or not the coolant temperature Thw detected by the coolant temperature sensor 12 is lower than the reference coolant temperature Thw0. That is, when the cooling water temperature Thw detected by the water temperature sensor 12 is equal to or higher than the reference cooling water temperature Thw0, the internal combustion engine 1 has already been started, and the previously issued engine start command I / G has been issued. It means that it was an erroneous command. If it is determined that the coolant temperature Thw detected by the coolant temperature sensor 12 is lower than the reference coolant temperature Thw0, cranking is started in the internal combustion engine 1 and the process proceeds to S103. The time when cranking is started corresponds to time T1 in FIG. When it is determined that the cooling water temperature Thw detected by the water temperature sensor 12 is equal to or higher than the reference cooling water temperature Thw0, this control is terminated.

  As described above, the cylinder 2 internal temperature Thcyl is a factor that greatly affects the ignitability and combustion stability of the fuel injected into the cylinder 2. Therefore, in S103, the cylinder 2 internal temperature Thcyl is estimated. Specifically, at the start of engine start, the coolant temperature Thw detected by the water temperature sensor 12 is set to the cylinder 2 internal temperature Thcyl, and then the cylinder 2 internal temperature Thcyl is increased according to the time during which the engine is started. Go. Here, since the degree of contribution of the thermal energy generated in the cylinder 2 to the in-cylinder temperature Thcyl differs between the case where the warm-up mode fuel injection described later is performed and the case where the acceleration mode fuel injection is performed, Considering this fuel injection, the cylinder 2 internal temperature Thcyl is estimated.

  In S104, it is determined whether or not the cylinder 2 internal temperature Thcyl estimated in S103 is higher than the reference cylinder internal temperature Thcyl0. Here, the reference cylinder temperature Thcyl0 is a case where the ignitability of the fuel injected by acceleration mode fuel injection and the stability of combustion of the fuel are relatively good, and the engine is started by acceleration mode fuel injection. Even if it exists, the temperature in the cylinder 2 which can be suppressed to such an extent that the fluctuation | variation of the engine rotational speed resulting from instability of combustion does not affect engine starting is said.

  Therefore, when it is determined that the cylinder 2 internal temperature Thcyl is equal to or lower than the reference cylinder internal temperature Thcyl0, the cylinder 2 internal temperature Thcyl is relatively low, and therefore, when the engine is started by acceleration mode fuel injection, Since the ignitability is low and the stability of combustion of the fuel is low, fluctuations in the engine rotation speed become large. Therefore, in this case, the process proceeds to S105, and warm-up mode fuel injection is performed in which the ignitability of the fuel is relatively good and the combustion is stable. Thereby, although the rate of increase in engine speed is low, the stability of combustion is ensured and the temperature in the cylinder 2 is efficiently increased.

  On the other hand, when it is determined that the cylinder 2 internal temperature Thcyl is higher than the reference cylinder internal temperature Thcyl0, the injected fuel is injected even when the engine is started by acceleration mode fuel injection because the cylinder 2 internal temperature Thcyl is relatively high. The ignitability of the fuel and the stability of combustion of the fuel are ensured. Therefore, in this case, the process proceeds to S106, and acceleration mode fuel injection with a high rate of increase in engine speed is performed. As a result, it is possible to efficiently increase the engine rotation speed in a state where the ignitability of fuel and the stability of combustion are ensured. Note that the time point when switching from the warm-up mode fuel injection to the acceleration mode fuel injection is time T2 in FIG. By switching to the acceleration mode fuel injection, the rate of increase of the engine speed is greatly increased, while the rate of increase of the temperature in the cylinder 2 is decreased.

When the process of S105 or S106 ends, the process proceeds to S107. In S107, it is determined whether or not the engine speed has exceeded the start completion speed Nc. That is, it is determined whether the engine start of the internal combustion engine 1 is completed. When it is determined that the engine rotational speed has exceeded the start completion rotational speed Nc, this control is terminated. The time point when the engine rotational speed exceeds the start completion rotational speed Nc is time T3 in FIG. If it is determined that the engine rotation speed does not exceed the start completion rotation speed Nc, the processing after S103 is performed again.

  According to this control, warm-up mode fuel injection is performed when the cylinder 2 internal temperature is lower than the reference cylinder temperature Thcyl0, and acceleration mode fuel injection is performed when the cylinder 2 internal temperature is equal to or higher than the reference cylinder temperature Thcyl0. The engine speed is increased. As a result, the stability of combustion at the time of starting the engine is ensured and the time required for starting the engine can be shortened as much as possible. As a result, it is possible to suppress the fuel consumption required for starting the engine and stabilize the combustion at the start of the engine to suppress the deterioration of the emission.

  Next, a second embodiment of engine start control in the internal combustion engine 1 shown in FIG. 1 will be described based on the control flow of FIG. In addition, when the process during the engine start control shown in FIG. 5 has the same contents as the process during the engine start control shown in FIG. 3, the same reference numerals are given and the description thereof is omitted.

  The difference between the engine start control shown in FIG. 5 and the engine start control shown in FIG. 3 is that correction based on the stable combustion state when acceleration mode fuel injection is performed is performed (processes S201 to S206 in FIG. 5). ). Hereinafter, correction based mainly on the stable combustion state will be described.

  In the engine start control, when the process of S106 is completed, the process proceeds to S201. In S201, it is determined whether the combustion stable state is a misfire state in the cylinder 2 when the acceleration mode fuel injection is performed. Here, the combustion stable state is a state representing the stability of combustion in the cylinder 2. The fact that the stable combustion state becomes a misfire state means that the engine rotational speed at the time of starting the engine is greatly reduced because the fuel injected by the acceleration mode fuel injection is not burned well. Therefore, the determination of whether or not the stable combustion state is a misfire state is made based on fluctuations in the engine speed. In addition to this, it is determined that the stable combustion state is a misfire state when the pressure fluctuation in the cylinder 2 greatly decreases or when the exhaust temperature Thex detected by the exhaust temperature sensor 14 decreases significantly. Also good.

  Here, when it is determined in S104 that the cylinder 2 internal temperature Thcyl is higher than the reference cylinder temperature Thcyl0 and the stable combustion state becomes a misfire state, the value of the reference cylinder temperature Thcyl0 that is a reference for determination in S104 is There may be cases where it is not appropriate. Therefore, if it is determined in S201 that the stable combustion state is a misfire state, the process proceeds to S202, and correction is performed to increase the value of the reference cylinder temperature Thcyl0 by 10 ° C. As a result, the region where the warm-up mode fuel injection should be performed at the cylinder 2 internal temperature Thcyl is expanded, and this is applied when the determination of S104 is performed again. As a result, the acceleration mode fuel injection is performed after the cylinder 2 internal temperature Thcyl is further increased. When the acceleration mode fuel injection is being performed, the combustion stable state becomes the misfire state, so that the engine speed is increased. Large fluctuations can be suppressed. When the process of S202 ends, the process proceeds to S107.

  On the other hand, if it determines with the combustion stable state not being a misfire state in S201, it will progress to S203. In S203, the value of the ignition counter is incremented by one. Here, the ignition counter is a counter that is counted every time it is determined in S201 that the combustion state is not a misfire state. When the process of S203 ends, the process proceeds to S204.

  In S204, it is determined whether or not the value of the ignition counter exceeds 4. When the value of the ignition counter exceeds 4, the process proceeds to S205, and when it does not exceed, the process proceeds to S107.

  In S205, correction is performed to lower the value of the reference cylinder temperature Thcyl0 by 2 ° C. Therefore, the correction to decrease the value of the reference cylinder temperature Thcyl0 is performed only after it is determined four times that the stable combustion state is not the misfire state. As a result, the region where the warm-up mode fuel injection should be performed at the cylinder 2 internal temperature Thcyl is reduced, and this is applied when the determination of S104 is performed again. As a result, switching from the warm-up mode fuel injection to the acceleration mode fuel injection is performed more quickly, and the time required for starting the engine can be shortened. When the process of S205 is completed, the process proceeds to S206, and the value of the ignition counter is reset to zero. When the process of S206 ends, the process proceeds to S107.

  According to this control, warm-up mode fuel injection is performed when the cylinder 2 internal temperature is lower than the reference cylinder temperature Thcyl0, and acceleration mode fuel injection is performed when the cylinder 2 internal temperature is equal to or higher than the reference cylinder temperature Thcyl0. The engine speed is increased. As a result, the stability of combustion at the time of starting the engine is ensured and the time required for starting the engine can be shortened as much as possible. As a result, it is possible to suppress the fuel consumption required for starting the engine and stabilize the combustion at the start of the engine to suppress the deterioration of the emission. During this control, the correction value of the value of the reference cylinder temperature Thcyl0 is increased by 10 ° C. and decreased by 2 ° C., but this may be changed as appropriate according to the engine start state in the internal combustion engine 1.

  Further, by correcting a reference value for switching determination between warm-up mode fuel injection and acceleration mode fuel injection based on the stable combustion state when acceleration mode fuel injection is performed, the stability of combustion and engine At a more appropriate time when the rotational speed acceleration is balanced, switching between the warm-up mode fuel injection and the acceleration mode fuel injection becomes possible, and a quicker engine start is achieved.

  Next, a third embodiment of engine start control in the internal combustion engine 1 shown in FIG. 1 will be described based on the control flow of FIG. If the processing during engine start control shown in FIG. 6 has the same contents as the processing during engine start control shown in FIG. 3 and FIG. 5, the same reference numerals will be assigned and description thereof will be omitted. To do.

  The difference between the engine start control shown in FIG. 6 and the engine start control shown in FIG. 5 is the correction target based on the stable combustion state when the acceleration mode fuel injection is performed (the processes in steps S301 and S302 in FIG. 5). is there. Hereinafter, correction based mainly on the stable combustion state will be described.

  In this engine start control, when it is determined in S201 that the stable combustion state is a misfire state, the process proceeds to S301, and the value of the in-cylinder temperature Thcyl estimated in S103 is corrected by 10 ° C. As a result, the region where the warm-up mode fuel injection should be performed at the cylinder 2 internal temperature Thcyl is expanded as a result, and the corrected cylinder 2 internal temperature Thcyl is applied in the following processing. As a result, the acceleration mode fuel injection is performed after the cylinder 2 internal temperature Thcyl is further increased. When the acceleration mode fuel injection is being performed, the combustion stable state becomes the misfire state, so that the engine speed is increased. Large fluctuations can be suppressed. When the process of S301 ends, the process proceeds to S107.

On the other hand, when it is determined in S201 that the stable combustion state is not the misfire state and it is determined that the value of the ignition counter exceeds 4, the process proceeds to S302, and the value of the cylinder 2 internal temperature Thcyl estimated in S103 is set to 2. Perform correction to increase ℃. As a result, the region where the warm-up mode fuel injection should be performed at the cylinder 2 internal temperature Thcyl is reduced, and the corrected cylinder 2 internal temperature Thcyl is applied in the following processing. As a result, switching from the warm-up mode fuel injection to the acceleration mode fuel injection is performed more quickly, and the time required for starting the engine can be shortened. When the process of S302 ends, the process proceeds to S206, and the value of the ignition counter is reset to zero.

  According to this control, similarly to the engine start control shown in FIG. 5, it is possible to suppress the fuel consumption required for starting the engine and stabilize the combustion at the start of the engine to suppress the deterioration of the emission. Furthermore, at a more suitable time when the stability of combustion and the acceleration of the engine rotational speed are balanced, switching between warm-up mode fuel injection and acceleration mode fuel injection becomes possible, and a quicker engine start is achieved. .

  Since the estimated temperature in the cylinder 2 is corrected to a more appropriate temperature based on the combustion stable state at the time of acceleration mode fuel injection, other control using the cylinder internal temperature Thcyl, for example, after the engine start is completed It can be suitably applied to fuel injection control for exhaust gas purification.

1 is a first diagram illustrating a schematic configuration of a compression ignition internal combustion engine to which a start control device and a start control method for a compression ignition internal combustion engine according to an embodiment of the present invention are applied. It is a figure showing the relationship between the ignition timing of a fuel, the temperature in a cylinder, and an output torque in the starting control apparatus of the compression ignition internal combustion engine which concerns on embodiment of this invention. 4 is a flowchart relating to engine start control that is executed when the engine is started in the start-up control device for a compression ignition internal combustion engine according to the first embodiment of the present invention. FIG. 4 is a diagram showing changes in engine speed and in-cylinder temperature when the engine start control shown in FIG. 3 is performed in the start ignition control apparatus for a compression ignition internal combustion engine according to the first embodiment of the present invention. FIG. 6 is a flowchart relating to engine start control that is executed when the engine is started in the start-up control apparatus for a compression ignition internal combustion engine according to a second embodiment of the present invention. FIG. 7 is a flowchart relating to engine start control that is executed at the time of engine start in a start-up control device for a compression ignition internal combustion engine according to a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Piston 5 ... Intake valve 6 ... Exhaust valve 7 ... Intake port 8. ... Exhaust port 10 ... ECU
11 .... Ignition switch 12 .... Water temperature sensor 13 .... Crank position sensor 14 .... Exhaust opening sensor

Claims (4)

Combustion of the fuel in the first fuel injection timing fuel ignition is started in the first ignition timing cylinder temperature a period of the compression stroke near the top dead center of a compression ignition internal combustion engine reaches a stable combustion temperature in the gas cylinder First fuel injection means for injecting fuel to increase the temperature in the cylinder by
Second fuel injection means for performing fuel injection at a second fuel injection timing at which fuel ignition is started in the cylinder at a second ignition timing in the expansion stroke that is retarded from the first ignition timing;
When the fuel injection is performed by the first fuel injection means, the degree of contribution of the thermal energy generated in the cylinder by the fuel injection by the first fuel injection means to the in-cylinder temperature is considered, Considering the degree of contribution of the thermal energy generated in the cylinder by the second fuel injection means to the in-cylinder temperature when the fuel injection is performed by the second fuel injection means, the cylinder An in-cylinder temperature detecting means for estimating the internal temperature;
At the start of engine start of the compression ignition internal combustion engine, fuel injection is first performed by the first fuel injection unit, and then the cylinder temperature estimated by the cylinder temperature detection unit is injected by the second fuel injection unit. The engine start is performed to increase the engine rotation speed of the compression ignition internal combustion engine to the start completion rotation speed by performing fuel injection by the second fuel injection means after reaching a predetermined cylinder temperature at which the fuel can be stably burned. A start-up control device for a compression ignition internal combustion engine. Combustion stable state determining means for determining a combustion stable state in the cylinder when the fuel injection by the second fuel injection means is performed by the engine start control means;
Based on the combustion stability state is determined by the combustion stable state determining means, said cylinder cylinder temperatures estimated by the temperature detection means, or a temperature correction means for correcting the predetermined cylinder temperature, a further The start-up control device for a compression ignition internal combustion engine according to claim 1 , further comprising: A combustion stable state determining means for determining a combustion stable state in the cylinder when fuel injection by the second fuel injection means is performed by the engine start control means;
The start control of the compression ignition internal combustion engine according to claim 1, wherein a period for performing fuel injection by the first fuel injection unit is changed based on a combustion stable state determined by the combustion stable state determination unit. apparatus. The combustion stable state determining means is configured to perform combustion in the cylinder based on at least one of the pressure in the cylinder, the temperature of exhaust gas discharged from the compression ignition internal combustion engine, and the engine rotation speed of the compression ignition internal combustion engine. The start control device for a compression ignition internal combustion engine according to claim 2 or 3 , wherein a stable state is determined.

Images