JP6413563B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device that switches between a premixed combustion operation and a diffusion combustion operation in accordance with a traveling state of a vehicle.

  Conventionally, techniques for changing the combustion state in the engine cylinder in accordance with the running state of the vehicle have been proposed. That is, this is a technology that uses both premixed combustion and diffusion combustion in a single engine. The premixed combustion is a combustion mode of a fuel mixture in which fuel and oxygen (oxidant) are mixed in advance, for example, a combustion mode in a spark ignition gasoline engine that injects fuel into an intake port. Diffusion combustion is a combustion mode of a combustion mixture in which the mixed state of fuel and oxygen is slightly non-uniform (fuel and oxygen burn while diffusing each other). For example, the fuel is directly in the cylinder. It is a combustion form in the compression ignition type diesel engine injected.

Diesel engines that realize these two types of combustion states are called PCCI (Premixed Charge Compression Ignition) engines, HCCI (Homogeneous Charge Compression Ignition) engines, CAI (Controlled Auto Ignition) engines, and the like. In recent years, a technique for establishing premixed compression auto-ignition combustion in a spark ignition type gasoline engine has been developed.
Since premixed combustion is combustion of a lean fuel mixture, the combustion temperature is lower than that of diffusion combustion, and the amount of nitrogen oxides and soot produced is small. Therefore, it is possible to improve the exhaust performance of the vehicle by setting the combustion mode in the vehicle engine in which the generation amount of nitrogen oxides and soot is regulated to premixed combustion (see Patent Documents 1 and 2). ).

Japanese Patent No. 5447294 Japanese Patent No. 3931900

  However, in premixed combustion, the combustion reaction proceeds and completes in a shorter time than diffusion combustion, so that there is a problem that noise generated with combustion tends to increase. Therefore, it is difficult to maintain the quietness of the vehicle while improving the exhaust performance, and there is a problem that it is difficult to improve the drive feeling.

  This case has been devised in view of the above problems, and an object of the present invention is to provide an engine control device that improves both exhaust performance and quietness of a vehicle. It should be noted that the present invention is not limited to this purpose, and is an operational effect that is derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

(1) An engine control device disclosed herein is an engine control device that switches between a premixed combustion operation and a diffusion combustion operation in accordance with a running state of the vehicle. a detection unit for detecting the presence or absence of rapid deceleration request to the rapid deceleration, and a determination unit for permitting the diffusion combustion operation prohibits the premixed combustion operation during the rapid deceleration request by the detecting section is detected Prepare. The determination unit prohibits the premixed combustion operation and permits the diffusion combustion operation until a predetermined time elapses after the sudden deceleration request is not detected. The engine control device includes at least one of the following configurations (A) to (C).
(A) The predetermined time is shorter as the vehicle speed of the vehicle is higher.
(B) The predetermined time is a time until the difference between the target value and the actual value becomes equal to or less than a predetermined value for each of the supercharging pressure and the intake oxygen concentration of the engine.
(C) When the required load occurs while the premixed combustion operation is prohibited, the determination unit cancels the prohibition and permits the premixed combustion operation.

  The premix combustion operation means an operation state in which fuel and oxygen are distributed almost uniformly in the cylinder of the engine and the mixture is self-ignited and combusted. Further, the diffusion combustion operation means an operation state in which an air-fuel mixture having a slightly non-uniform mixture state of the fuel and oxygen is generated and the air-fuel mixture is self-ignited and combusted. The intake oxygen concentration in the premixed combustion operation is controlled to be lower than the intake oxygen concentration in the diffusion combustion operation.

(2) It is preferable that the predetermined time is a time until the difference between the target value and the actual value becomes a predetermined value or less for each of the supercharging pressure and the intake oxygen concentration of the engine.

(3) It is preferable that the determination unit cancels the prohibition and permits the premixed combustion operation when a required load occurs while the premixed combustion operation is prohibited.
The “required load” here is a load for accelerating the vehicle, which is grasped based on the driving operation of the driver. The “required load” is set according to, for example, the accelerator opening (the amount by which the accelerator pedal is depressed).
(4) Whether the determination unit cancels the prohibition using a condition including a parameter that correlates with a noise amount of the engine when a required load occurs while the premixed combustion operation is prohibited. It is preferable to determine whether or not.

  According to the engine control device disclosed herein, premixed combustion operation is prohibited when a sudden deceleration request is detected, so that noise generation in a no-load state and a low-load state can be prevented, and the drive feeling Can be improved. In addition, the exhaust performance can be improved because the premixed combustion operation is not prohibited in normal deceleration where a sudden deceleration request is not detected. Therefore, both the exhaust performance and the quietness of the vehicle can be improved.

It is a mimetic diagram showing the whole engine control device composition of an embodiment. (A) is a fuel injection pattern in a diffusion combustion operation, (B) is a fuel injection pattern in a premixed combustion operation, (C) is a heat release rate, and (D) is a graph showing in-cylinder pressure. It is an example of a map for switching between premixed combustion and diffusion combustion. It is a graph showing the relationship between the reduction ratio and the predetermined time T _0. It is a figure for demonstrating the determination content at the time of a rapid acceleration request | requirement, (A) is based on a supercharging pressure, (B) is based on an intake oxygen concentration. It is a graph showing the relationship between the vehicle speed and the predetermined time T _2. It is a figure for demonstrating the determination content at the time of rapid deceleration operation, (A) is based on a supercharging pressure, (B) is based on an intake oxygen concentration. It is a flowchart which shows the control procedure at the time of normal. It is a flowchart which shows the control procedure at the time of sudden acceleration. It is a flowchart which shows the control procedure at the time of sudden deceleration.

  An engine control apparatus as an embodiment will be described with reference to the drawings. The embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment, and can be selected or combined as necessary.

[1. engine]
The engine control apparatus 1 of this embodiment is applied to a vehicle equipped with the engine 10 shown in FIG. FIG. 1 illustrates one of a plurality of cylinders provided in the engine 10. The engine 10 is a diesel engine that uses light oil as fuel, and switches between a diffusion combustion operation and a premixed combustion operation according to the traveling state of the vehicle. The diffusion combustion operation is an operation mode that realizes diffusion combustion (diffusion compression auto-ignition combustion) in the cylinder of the engine 10. On the other hand, the premixed combustion operation is an operation mode for realizing premixed combustion (premixed compression auto-ignition combustion) in the cylinder of the engine 10. In the engine 10 of this embodiment, these two types of combustion states are properly used according to the running state of the vehicle.

  An intake port and an exhaust port are provided on the top surface of the cylinder, and an intake valve and an exhaust valve are provided in each port opening. Further, an in-cylinder injection valve 11 is provided at the upper part in the cylinder in a state where its tip protrudes toward the combustion chamber. The in-cylinder injection valve 11 is a direct injection injector that injects fuel into each cylinder, and is connected to a common rail (pressure accumulation chamber) in which high-pressure fuel is stored.

  The fuel injection amount and injection timing supplied from the in-cylinder injection valve 11 are controlled by the engine control device 1. For example, when a control pulse signal is transmitted from the engine control device 1 to the in-cylinder injection valve 11, the nozzle hole of the in-cylinder injection valve 11 is opened only for a period corresponding to the magnitude of the control pulse signal. Thereby, the fuel injection amount becomes an amount corresponding to the magnitude (drive pulse width) of the control pulse signal, and the fuel injection timing (injection timing) corresponds to the time when the control pulse signal is transmitted.

A fuel injection pattern during the diffusion combustion operation is shown in FIG. Here, a case will be described where multistage injection including four stages of pilot injection, pre-injection, main injection, and post-injection is performed. Pilot injection and pre-injection are performed during the compression stroke, main injection that contributes most to engine output is performed before and after compression top dead center (TDC), and post-injection is performed after the combustion stroke. The heat generation rate in the diffusion combustion operation becomes maximum immediately after the main injection, as indicated by a broken line in FIG. The time from the end time θ _{1 of} main injection to the ignition time θ ₂ (ignition delay time) is relatively short, and ignition may occur during the main injection. Further, the in-cylinder pressure in the diffusion combustion operation fluctuates moderately as shown by a broken line in FIG.

On the other hand, the fuel injection pattern during the premixed combustion operation is shown in FIG. In the premixed combustion operation, pilot injection, pre-injection, and post-injection are omitted, and main injection is performed during the compression stroke. Further, after the compression top dead center (TDC), after injection is performed in an auxiliary manner. The heat generation rate in the premixed combustion operation becomes the maximum after a predetermined premixing period from the main injection, as indicated by a solid line in FIG. The ignition delay time from the main injection end time θ ₃ to the ignition time θ ₄ is longer than the ignition delay time in the diffusion combustion operation. Further, the in-cylinder pressure in the premixed combustion operation has a characteristic that increases and decreases more rapidly than the in-cylinder pressure in the diffusion combustion operation, and is peaky (pointed) as shown by a solid line in FIG. It becomes a graph shape.

  The intake passage 12 and the exhaust passage 13 of the engine 10 are provided with a turbocharger 14 (supercharger) for supercharging by forcibly sending the air on the intake passage 12 into the cylinder using the exhaust pressure. Is done. In the intake passage 12, an air cleaner 16, a low-pressure throttle valve 17, a turbocharger 14, an intercooler 18, and a high-pressure throttle valve 19 are provided in this order from the upstream side. On the other hand, in the exhaust passage 13, an exhaust purification device 15 is interposed downstream of the turbocharger 14. The exhaust purification device 15 includes a DOC (diesel oxidation catalyst) 15A, a DPF (diesel particulate filter) 15B, and the like.

  Further, the engine 10 is provided with a high pressure EGR passage 20 and a low pressure EGR passage 23 for recirculating a part of the exhaust to the intake side. The high pressure EGR passage 20 is a passage connecting the exhaust passage 13 upstream of the turbocharger 14 and the intake passage 12 downstream of the high pressure throttle valve 19. A high pressure EGR cooler 21 and a high pressure EGR valve 22 are interposed in the high pressure EGR passage 20. The low pressure EGR passage 23 is a passage connecting the exhaust passage 13 downstream of the turbocharger 14 and the intake passage 12 upstream of the intercooler 18. A low pressure EGR filter 24, a low pressure EGR cooler 25, and a low pressure EGR valve 26 are interposed in the low pressure EGR passage 23. The valve openings of the high pressure EGR valve 22 and the low pressure EGR valve 26 are variable.

An engine speed sensor 31 that detects the engine speed Ne is provided in the vicinity of the crankshaft of the engine 10. Further, on the downstream side of the high-pressure throttle valve 19 in the intake passage 12, a pressure sensor 32 for detecting the pressure of the intake air introduced into the cylinder (supercharging pressure P during supercharging), and the oxygen concentration in the intake air ( An oxygen concentration sensor 33 for detecting the intake oxygen concentration D) is provided.
At an arbitrary position of the vehicle, an accelerator opening sensor 34 that detects the amount of depression of the accelerator pedal (accelerator opening), a shift position sensor 35 that detects the operation position of the shift lever, and a vehicle speed sensor 36 that detects the vehicle speed, Is provided. The operation position of the shift lever corresponds to the gear position (for example, 1st speed, 2nd speed,..., 6th speed, etc.) of the transmission mounted on the vehicle, and the larger the number of stages (the more the speed goes from the low speed stage to the high speed stage). It means that the reduction ratio is small. Various information detected by the various sensors 31 to 36 is transmitted to the engine control device 1.

[2. Engine control unit]
A vehicle equipped with the engine 10 is provided with an engine control device 1 (Engine Electronic Control Unit). The engine control device 1 is an electronic control device that comprehensively controls a wide range of systems such as an ignition system, a fuel system, an intake / exhaust system, and a valve system related to the engine 10, and the amount of intake air supplied to each cylinder of the engine 10. The fuel injection amount, the fuel injection timing, the EGR amount, and the like are controlled. The engine control device 1 is connected to other electronic control devices (for example, transmission ECU, air conditioner ECU, brake ECU, vehicle body control ECU, body ECU, etc.) and various sensors 31 to 36 via an in-vehicle network.

  The engine control device 1 is an electronic device in which a microprocessor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, and the like are integrated. . The microprocessor is a processing device (processor) including a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (register group), and the like. The ROM, RAM, and nonvolatile memory are memory devices that store programs and working data. The control contents in the engine control device 1 are recorded in ROM, RAM, nonvolatile memory, and removable media as application programs, for example. When the program is executed, the contents of the program are expanded in the memory space in the RAM and executed by the microprocessor.

  The engine control apparatus 1 according to the present embodiment performs “combustion state switching control” for switching between a premixed combustion operation and a diffusion combustion operation in accordance with the traveling state of the vehicle. The traveling state of the vehicle is determined based on various information detected by various sensors 31 to 36, for example. In addition, as shown in FIGS. 2 (A) and 2 (B), the combustion state in the cylinder (premixed combustion, diffusion combustion) controls the fuel injection amount and the fuel injection timing, and the intake air amount and EGR amount. It can be switched by adjusting. The engine control device 1 is provided with a detection unit 2, a map storage unit 3, a determination unit 4, and a control unit 8 as elements for performing combustion state switching control.

[2-1. Detection unit]
The detection unit 2 detects a driver's driving operation referred to in the combustion state switching control. In this case, information on the gear stage of the transmission, the elapsed time since that gear stage, the sudden acceleration request, the sudden deceleration request, and the required load are acquired. Based on the information on the operation position of the shift lever detected by the shift position sensor 35, the speed of the transmission is determined as to what speed the current speed is. Further, every time the operation position of the shift lever is changed, the elapsed time from the current gear position is measured. The presence / absence of a sudden acceleration request, a sudden deceleration request, and a required load can be detected based on the driving operation of the driver. Information on these shift speeds, elapsed time, sudden acceleration request, sudden deceleration request, and required load is transmitted to the determination unit 4.

In the present embodiment, based on the accelerator opening detected by the accelerator opening sensor 34, it is determined whether there is a sudden acceleration request, a sudden deceleration request, or a required load. For example, when the accelerator opening is positive (when the accelerator is on), the detection unit 2 determines that “there is a required load”. When the time change rate of the accelerator opening is equal to or greater than a positive predetermined value, the detection unit 2 determines that “there is a sudden acceleration request”. The moving direction of the operating point of the engine 10 at the time of the rapid acceleration request is an increasing direction of the engine load Ec and the engine speed Ne. For example, the operating point R ₁ and the operating point R ₂ in FIG. 3 move in the upper right direction after the rapid acceleration request is detected.

When the time change rate of the accelerator opening is equal to or less than the negative predetermined value, the detection unit 2 determines that “there is a sudden deceleration request”. The direction of movement of the operating point at the time of a sudden deceleration request is a decreasing direction of the engine load Ec and the engine speed Ne. For example, the operating point R ₃ and the operating point R ₄ in FIG. 3 move in the lower left direction after the rapid deceleration request is detected. Instead of the accelerator opening, refer to the brake pedal depression amount, brake fluid pressure change rate over time, clutch pedal depression amount, shift lever operation to the neutral position, etc. to determine whether there is a sudden deceleration request. May be.

[2-2. Map storage unit]
The map storage unit 3 stores a control map in which a correspondence relationship between the running state of the vehicle and the combustion state is defined. The traveling state of the vehicle is grasped based on at least one of the engine load Ec and the engine speed Ne, and preferably grasped based on both the engine load Ec and the engine speed Ne. The engine load Ec here is a parameter corresponding to an output request to the engine 10, and is calculated based on, for example, the accelerator opening, the vehicle speed, the intake air amount, the intake pressure, etc. detected by the accelerator opening sensor 34. . It should be noted that it is preferable to consider the outside air temperature, the outside air pressure, the engine coolant temperature, and the like when grasping the traveling state of the vehicle.

  As shown in FIG. 3, in this embodiment, a control map is used in which the correspondence between the operating point determined by the engine load Ec and the engine speed Ne and the combustion state is set for each gear position. A region M1 in FIG. 3 represents a region where the premixed combustion operation is performed when the gear stage is at the first speed, and a region M2 including the region M1 is performed when the gear stage is at the second speed. Represents an area. Similarly, the region M3 including the region M1 and the region M2 is a region where the premixed combustion operation is performed when the shift speed is the third speed, and the region M4 including all of the regions M1 to M3 has the shift speed of 4. This is the region where the premixed combustion operation is performed when the speed is higher than the speed. The region C outside the regions M1 to M4 is a region where the diffusion combustion operation is performed at each shift stage (a region where the premixed combustion operation is not performed).

The relationship between the engine load Ec and the engine speed Ne and the respective regions M1 to M4 is illustrated in the following table. Incidentally, the magnitude relationship of _{Ne 1 ~Ne 5, Ec 1 ~Ec} 4 shown in Table 1, in _{Ne 1 <Ne 2 <Ne 3} <Ne 4 <Ne 5, Ec 1 <Ec 2 <Ec 3 <Ec 4 is there. These values may be fixed values set in advance, for example, or may be variable values calculated based on vehicle running conditions (for example, outside air temperature, outside air pressure, engine coolant temperature, etc.). .

The area where the premixed combustion operation is performed on the map is expanded as the number of shift speeds increases. For example, in the state where the gear stage is in the second speed, the execution region of the premixed combustion operation is expanded in the increasing direction (right direction) of the engine speed Ne as compared with the state in which the gear stage is the first speed. In other words, the lower the gear ratio, the larger the upper limit value of the engine speed Ne among the conditions for performing the premixed combustion operation.
Further, in the state where the gear stage is in the third speed, the premixed combustion operation is performed not only in the increasing direction of the engine speed Ne (right direction) but also in the engine load Ec as compared with the state in which the gear stage is the second speed. It is also enlarged in the increasing direction (upward). In other words, the lower the gear ratio, the higher the upper limit value of the engine load Ec in the premix combustion operation conditions.

Here, the speed reduction ratio when the shift speed is 1st speed is referred to as a first speed reduction ratio, and the speed reduction ratio when the speed speed is 2nd speed is referred to as a second speed reduction ratio. The second reduction ratio has a smaller value than the first reduction ratio.
When the speed reduction ratio is less than the first speed reduction ratio (for example, when the gear position is 2nd speed), the engine speed is higher than when the speed reduction ratio is equal to or higher than the first speed reduction ratio (for example, when the speed ratio is 1st speed). The execution region of the premixed combustion operation is set so that the upper limit value of Ne becomes large (Ne ₄ > Ne ₃ ).
Further, when the speed reduction ratio is less than the second speed reduction ratio (for example, when the gear stage is 3rd speed), the engine is more effective than when the speed reduction ratio is greater than or equal to the second speed reduction ratio (for example, when the speed ratio is 2nd speed). The execution range of the premixed combustion operation is set so that the upper limit value of the load Ec is increased (Ec ₃ > Ec ₂ ).

  As described above, the directions in which the premixed combustion operation execution area expands are two directions on the map, that is, an increase direction of the engine speed Ne (right direction) and an increase direction of the engine load Ec (upward direction). Also, the increase in the engine speed Ne is given priority over the increase in the engine load Ec rather than expanding in the two directions evenly with respect to the increase in the number of shift stages. Implemented. In other words, the minimum shift stage in which the premixed combustion operation execution range is expanded in the direction of increasing engine load Ec is the third speed, whereas the minimum shift stage in which the engine speed Ne is increased is increased. The second speed has a larger reduction ratio than the third speed. By setting such a map, the execution area of the premixed combustion operation is expanded in a direction in which noise of the engine 10 is less likely to occur.

[2-3. Judgment unit]
The determination unit 4 determines whether or not the traveling state of the vehicle satisfies an execution condition for the premixed combustion operation. The determination unit 4 includes a first determination unit 5, a second determination unit 6, and a third determination unit 7. The first determination unit 5 performs a basic determination based on the operating point. On the other hand, the 2nd determination part 6 makes the exceptional determination with respect to a principle, and bears determination when a sudden acceleration operation is made. Similarly, the 3rd determination part 7 bears determination when sudden deceleration operation is made. Therefore, the determination content in the first determination unit 5 is adopted in the case of a normal operation that is not a sudden acceleration operation or a sudden deceleration operation. As described above, the reason why the determination that is different from the normal determination is performed only when the sudden acceleration operation or the sudden deceleration operation is performed is that the noise generated in the engine 10 due to the change in the driving state resulting from these operations, This is because the noise masking effect (the ease of noise transmission to the passenger) also changes.

[A. First determination unit]
The first determination unit 5 determines the execution condition of the premixed combustion operation based on the control map stored in the map storage unit 3. Here, when the operating point determined by the engine load Ec and the engine speed Ne of the vehicle is within the execution range set based on the gear position at that time, the execution condition for the premixed combustion operation is satisfied. Judged to be.
For example, when the shift speed is the first speed, the condition for performing the premixed combustion operation is satisfied when the operating point is included in the region M1 (Ne ₁ ≦ Ne ≦ Ne ₃ and Ec ₁ ≦ Ec ≦ Ec ₂ ). It is determined. Further, when the shift speed is the third speed, the operating point is in the region M3 (Ne ₁ ≦ Ne ≦ Ne ₂ and Ec ₁ ≦ Ec ≦ Ec ₂ , or Ne ₂ ≦ Ne ≦ Ne ₅ and Ec ₁ ≦ Ec ≦ Ec _3. ) Is determined.

However, immediately after the shift stage of the transmission is changed, the intake air amount, the EGR amount, the operating point of the engine 10 and the like may change transiently and the combustion state may become unstable. For this reason, it is determined that the conditions for performing the diffusion combustion operation are satisfied regardless of whether or not the conditions for performing the premixed combustion operation are satisfied until the predetermined time T ₀ elapses after the shift speed is changed. The determination result here is transmitted to the control unit 8.

As a method for setting the predetermined time T ₀ , for example, the following method can be considered.
Method 1: A preset fixed value (for example, several seconds) Method 2: A variable value set according to the gear position (reduction ratio) Method 3: Until the boost pressure P and intake oxygen concentration D are stabilized Time

Method 2 described above is to set the predetermined time T ₀ according to the gear position or reduction ratio of the transmission. In this case, it is preferable to set the correspondence between the shift speed (the speed reduction ratio) and the predetermined time T ₀ as a control map. Further, the above method 3 is a method for suppressing a decrease in combustion stability due to an intake delay or a supercharging delay. For example, for each of the supercharging pressure P and the intake oxygen concentration D, a target value and an actual value are set. The time until the difference ΔP, ΔD becomes equal to or less than a predetermined value is defined as a predetermined time T ₀ .

  As actual values of the supercharging pressure P and the intake oxygen concentration D, values detected by the pressure sensor 32 and the oxygen concentration sensor 33 can be used. Further, the target values of the supercharging pressure P and the intake oxygen concentration D can be calculated based on, for example, the accelerator opening, the vehicle speed, the intake air amount, the intake pressure, and the like. Note that the above-described methods 2 and 3 may be used in combination, and the value of the predetermined value, which is a threshold value for the differences ΔP and ΔD between the target value and the actual value, may be set smaller as the number of gears is larger. .

In the present embodiment, it is assumed that the predetermined time T ₀ is set shorter as the speed reduction ratio is smaller, based on the above-described method 2. The relationship between the reduction ratio and the predetermined time T ₀ is illustrated in FIG. As shown in FIG. 4, the time until the start condition of the premixed combustion operation is determined is extended as the number of gears is smaller. Moreover, the time is shortened, so that the gear stage number is large. This is because the combustion state is likely to be unstable when the reduction ratio is large compared to the state where the reduction ratio is small.

[B. Second determination unit]
The second determination unit 6 performs a determination when a rapid acceleration request is detected by the detection unit 2 during the premixed combustion operation. In this determination, a condition including a parameter correlated with the noise amount of the engine 10 is used. Period of the determination is detected in at least rapid acceleration request, preferably in addition to this, rapid acceleration request is the period from no longer being detected until the predetermined time T ₁ is passed. The predetermined time T ₁ here may be a preset fixed value (for example, several seconds), or may be a variable value (for example, the engine load Ec and the engine speed Ne) set according to the operating state of the engine 10. It may be a value set accordingly.

Specific examples of the parameters correlated with the noise amount of the engine 10 include physical quantities that reflect the component ratio of the fuel mixture introduced into the cylinder, such as the supercharging pressure P and the intake oxygen concentration D of the engine 10. it can. These parameters are physical quantities that affect the combustion rate of the fuel mixture. In addition to these parameters, intake air temperature, humidity, intake air density, etc. may be used in combination.
The conditions under which the premixed combustion operation is performed (that is, the conditions under which the premixed combustion operation is continued when the detection unit 2 detects a rapid acceleration request during the premixed combustion operation) are “condition 1 or condition 2 is satisfied, or condition 3 or condition 4 is satisfied ”. However, in consideration of the noise suppression effect in the premixed combustion operation, the condition for performing the premixed combustion operation may be “condition 1 or condition 2 is satisfied and condition 3 or condition 4 is satisfied”. Good.

Condition 1: Condition supercharging pressure P is first less than a lower limit value P ₁ 2: boost pressure P is first lower limit value P ₁ or more, a second less than a upper limit value P _2, and
The difference ΔP between the target value and the actual value of the supercharging pressure P is greater than or equal to the first predetermined value ΔP _TH Condition 3: The intake oxygen concentration D is less than the second lower limit value D ₁ Condition 4: The intake oxygen concentration D is the first Two lower limit values D ₁ or more, less than the second upper limit value D ₂ , and
The difference ΔD between the target value and the actual value of the inspiratory oxygen concentration D is equal to or greater than the second predetermined value ΔD _TH2 The first upper limit value P ₂ in the conditions 1 to 4 is larger than the first lower limit value P ₁ Yes, the second upper limit value D ₂ is larger than the second lower limit value D ₁ (P ₁ <P ₂ , D ₁ <D ₂ ). The “lower limit value” here means the lower limit value at which appropriate diffusion combustion can be performed, and the “upper limit value” means the upper limit value at which appropriate premixed combustion can be performed. To do.

FIG. 5A is a diagram for explaining the contents of condition 1 and condition 2. When the determination based on the supercharging pressure P is performed, if a rapid acceleration request is detected during the premixed combustion operation, the second determination unit 6 determines the supercharging pressure P, the first lower limit value P ₁ , and the first upper limit value. the magnitude relation between P ₂ is determined. For example, the supercharging pressure P is for condition 1, if the less than a lower limit value P ₁ is satisfied, premix combustion operation is carried out. The condition 1 if the boost pressure P is the first upper limit value P ₂ or more, the condition 2 are both becomes unsatisfied, the diffusion combustion operation is performed.

If the supercharging pressure P is located between the first lower limit value P ₁ and the first upper limit value P ₂ , a determination is made based on the difference ΔP between the target value and the actual value of the supercharging pressure P. As shown in FIG. 5A, the target value of the supercharging pressure P gradually increases in response to the rapid acceleration request. Further, the actual value of the supercharging pressure P changes so as to gradually approach the target value with a supercharging delay. Even state where the boost pressure P is changed transiently, a difference [Delta] P is less than the first predetermined value [Delta] P _TH, premix combustion operation is carried out continuously. Further, the actual value of the supercharging pressure P may overshoot when the change with time (gradient) of the target value becomes small. On the other hand, when the difference [Delta] P equal to or greater than a first predetermined value [Delta] P _TH, since it is switched to the diffusion combustion operation from the premix combustion operation, no noise is excessively increased.

Each of the first lower limit value P ₁ , the first upper limit value P ₂ , and the first predetermined value ΔP _TH may be a preset fixed value, or a variable value set according to the operating state of the engine 10. It may be. In the present embodiment, each of the above values is set according to the engine load Ec and the engine speed Ne. For example, for each of the first lower limit value P ₁ , the first upper limit value P ₂ , and the first predetermined value ΔP _TH , the correspondence between the operating point determined by the engine load Ec and the engine speed Ne and each value is set. Assume that the map storage unit 3 stores the control map.

FIG. 5B is a diagram for explaining the contents of condition 3 and condition 4. When the determination based on the intake oxygen concentration D is performed, if a rapid acceleration request is detected during the premixed combustion operation, the second determination unit 6 causes the intake oxygen concentration D, the second lower limit value D ₁ , and the second upper limit value. the magnitude relation between D ₂ is determined. For example, the intake oxygen concentration D is for condition 3 if the second lower limit value D less than ₁ is satisfied, premix combustion operation is carried out. The intake oxygen concentration D is second upper limit D ₂ or value, if condition 3, the condition 4 are both becomes unsatisfied, the diffusion combustion operation is performed. If the intake oxygen concentration D is between the second lower limit value D ₁ and the second upper limit value D ₂ , a determination is made based on the difference ΔD between the target value and the actual value of the intake oxygen concentration D. Since the specific determination method based on the difference ΔD is the same as the determination method based on the difference ΔP, description thereof will be omitted. The predetermined value to be compared with the difference ΔD is referred to as a second predetermined value ΔD _TH2 .

Each of the second lower limit value D ₁ , the second upper limit value D ₂ , and the second predetermined value ΔD _TH2 may be a preset fixed value, or a variable value set according to the operating state of the engine 10. It may be. In the present embodiment, each of the above values is set according to the engine load Ec and the engine speed Ne. For example, for each of the second lower limit value D ₁ , the second upper limit value D ₂ , and the second predetermined value ΔD _TH2 , the correspondence between the operating point determined by the engine load Ec and the engine speed Ne and each value is set. Assume that the map storage unit 3 stores the control map.

The determination result of the second determination unit 6 has priority over the determination result of the first determination unit 5. Therefore, even if it is determined by the first determination unit 5 that the premixed combustion operation condition is satisfied, if the conditions 1 to 4 are not satisfied during the detection of the rapid acceleration request, the premixed combustion operation is performed. The diffusion combustion operation is carried out without being carried out. Further, when the predetermined time T ₁ has elapsed since the determination of the second determination unit 6 is started, the determination result of the first determination unit 5 is adopted. Since the determination by the second determination unit 6 corresponds to the rapid acceleration request during the premixed combustion operation, the determination ends when the operating point of the engine 10 enters the diffusion combustion operation region. The determination result of one determination unit 5 is adopted.

As described above, when the engine load Ec is transiently increasing due to the accelerator operation for rapid acceleration, the premixed combustion operation and the diffusion combustion operation are switched based on the condition including the parameter correlated with the noise amount of the engine 10. . As a result, the premixed combustion operation is continued in an operation state in which a noise level that is not noticeable to the driver can be generated, and thus the exhaust performance is improved. In addition, in an operation state in which the supercharging pressure P is equal to or higher than the first upper limit value P ₂ or an operation state in which the intake oxygen concentration D is equal to or higher than the second upper limit value D ₂ , the premixed combustion operation is the diffusion combustion operation. Therefore, excessive increase in noise is suppressed.

When the boost pressure P is between the two threshold values P ₁ and P ₂ or when the intake oxygen concentration D is between the two threshold values D ₁ and D ₂ , the boost pressure P and the intake oxygen concentration D Differences ΔP and ΔD between the target value and the actual value are referred to. As a result, as shown in FIGS. 5 (A) and 5 (B), the premixed combustion operation is switched to the diffusion combustion operation before the overshoot resulting from the supercharging delay or the intake air delay occurs. Excessive increase is further suppressed.

[C. Third determination unit]
The third determination unit 7 performs determination when the detection unit 2 detects a sudden deceleration request. Here, the premixed combustion operation is prohibited at least while the rapid deceleration request is detected, and the diffusion combustion operation is permitted instead. In the present embodiment, the premixed combustion operation is prohibited not only during the detection of the rapid deceleration request but also during the period from when the rapid deceleration request is not detected until the predetermined time T ₂ elapses.

The method of setting the predetermined time T _2, considered is a method such as follows.
Method 4: A preset fixed value (for example, several seconds) Method 5: A variable value set according to the vehicle speed Method 6: Time until the boost pressure P and the intake oxygen concentration D become stable

In the above method 5, as the vehicle speed is higher the predetermined time T ₂ is set to be shorter. In this case, for example, as shown in FIG. 6, it is preferable to set the relationship between the vehicle speed and the predetermined time T ₂ as a control map. Thereby, the prohibition time of the premixed combustion operation at the time of high speed traveling is shortened, and the exhaust performance is improved. Moreover, since the prohibition time of the premixed combustion operation becomes longer as the vehicle speed is lower, the combustion stability of the engine 10 is improved. The value of the vehicle speed can be detected by the vehicle speed sensor 36, and can be calculated based on the engine load Ec and the engine speed Ne.

The above method 6 is a method for suppressing a decrease in combustion stability due to an intake delay or a supercharging delay, similar to the method 3. For example, for each of the supercharging pressure P and the intake oxygen concentration D, the target value and the actual value are determined. the difference ΔP between the value, [Delta] D is one that the that the predetermined time T ₂ time until a predetermined value or less. As actual values of the supercharging pressure P and the intake oxygen concentration D, values detected by the pressure sensor 32 and the oxygen concentration sensor 33 can be used. The target values of the supercharging pressure P and the intake oxygen concentration D are, for example, accelerators. It can be calculated based on the opening degree, the vehicle speed, the intake air amount, the intake pressure, and the like.

As shown in FIG. 7A, the target value of the supercharging pressure P gradually decreases in response to the rapid deceleration request. Further, the actual value of the supercharging pressure P changes so as to gradually approach the target value with a supercharging delay. When the determination based on the supercharging pressure P is performed, the premixed combustion operation is prohibited in a state where the supercharging pressure P changes transiently, and the diffusion combustion operation is permitted instead. Thereafter, when the difference ΔP becomes equal to or _smaller than the third predetermined value ΔP _TH3 , the prohibition is canceled. The same applies to the case where the determination based on the intake oxygen concentration D is performed. As shown in FIG. 7B, the premixed combustion operation is prohibited in a state where the intake oxygen concentration D changes transiently. Diffusion combustion operation is permitted. Thereafter, when the difference ΔD becomes equal to or _smaller than the fourth predetermined value ΔD _TH4 , this prohibition is canceled.

  However, if a load required by the driver occurs while the premixed combustion operation is prohibited, the prohibition is canceled and the premixed combustion operation is permitted. The presence or absence of the required load is determined by the detection unit 2. The timing for canceling the prohibition may be a point in time when the required load occurs, or includes parameters (supercharging pressure P, intake oxygen concentration D, intake air temperature, humidity, intake air density, etc.) that correlate with the noise level of the engine 10. Whether or not to cancel the prohibition may be determined using a condition.

For example, when the determination based on the supercharging pressure P is performed, the prohibition may be canceled when the difference ΔP _becomes equal to or smaller than a fifth predetermined value ΔP _TH5 that is smaller than the third predetermined value ΔP _TH3. . Further, when the determination based on the intake oxygen concentration D is performed, the prohibition is canceled when the difference ΔD becomes equal to or smaller than the sixth predetermined value ΔD _TH6 which is smaller than the fourth predetermined value ΔD _TH4 . With these controls, the premixed combustion operation is started at the timing when the required load increases, assuming that the parameter correlated with the noise amount of the engine 10 has converged, and the drive feeling is improved.

When the above methods 5 and 6 are used in combination, the larger the number of gears, the greater the predetermined value (third predetermined value ΔP _TH3 , threshold) for the differences ΔP, ΔD between the target value and the actual value. The fourth predetermined value ΔD _TH4 , the fifth predetermined value ΔP _TH5 , and the sixth predetermined value ΔD _TH6 ) may be set small. Accordingly, the supercharging pressure P, taking into account the convergence of the intake oxygen concentration D, it is possible to shorten the predetermined time T ₂ as the vehicle speed increases.

  Further, when the rapid deceleration request is detected by the detection unit 2, the control configuration may be such that the premixed combustion operation is not immediately prohibited, but a condition for prohibiting the premixed combustion operation is determined. That is, as shown in FIGS. 7A and 7B, the premixed combustion operation is prohibited by referring to the values of the supercharging pressure P and the intake oxygen concentration D as well as the above differences ΔP and ΔD. The condition may be determined. Here, a specific example of the release condition for releasing the prohibition of the premixed combustion operation is shown below.

Condition 5: Condition supercharging pressure P is less than the third lower limit value P ₃ 6: supercharging pressure P is the third lower limit value P ₃ or more and less than the third upper limit value P _4, and
Conditions difference [Delta] P between the target value and the actual value of the supercharging pressure P is equal to or less than the third predetermined value [Delta] P _TH3 7: Conditions intake oxygen concentration D is less than the fourth limit value D ₃ 8: intake oxygen concentration D is the 4 lower limit value D ₃ or more, less than 4th upper limit value D ₄ , and
Intake oxygen concentration third upper limit value P ₄ of the difference [Delta] D between the target value and the actual value is in the condition 5 condition 8 is below a fourth predetermined value [Delta] D _TH4 of D is a value larger than the third lower limit value P ₃ The fourth upper limit value D ₄ is larger than the fourth lower limit value D ₃ (P ₃ <P ₄ , D ₃ <D ₄ ).

When the determination based on the supercharging pressure P is performed, when a sudden deceleration request is detected, the third determination unit 7 determines the magnitude relationship between the supercharging pressure P and the third lower limit value P ₃ and the third upper limit value P _4. Determined. For example, the supercharging pressure P is for Condition 1 is less than the third lower limit value P ₃ is satisfied, prohibit the premix combustion operation is canceled. If the supercharging pressure P is equal to or greater than the third upper limit value P ₄ , both conditions 1 and 2 are not satisfied, and the premixed combustion operation is prohibited (diffusion combustion operation is performed). Further, if the supercharging pressure P is located between the third lower limit value P ₃ and the third upper limit value P ₄ , a determination is made based on the difference ΔP between the target value and the actual value of the supercharging pressure P. . Each of the third lower limit value P ₃ , the third upper limit value P ₄ , and the third predetermined value ΔP _TH3 may be a preset fixed value, or a variable value set according to the operating state of the engine 10. It may be. The same applies to the determination based on the intake oxygen concentration D.

[2-4. Control unit]
The control unit 8 performs combustion state switching control based on the detection result of the detection unit 2 and the determination result of the determination unit 4. First, when the rapid acceleration request is detected by the detection unit 2, the premixed combustion operation and the diffusion combustion operation are controlled based on the determination result by the second determination unit 6. Further, when the rapid deceleration request is detected by the detection unit 2, the premixed combustion operation and the diffusion combustion operation are controlled based on the determination result of the third determination unit 7. When the sudden acceleration request and the sudden deceleration request are not detected, the premixed combustion operation and the diffusion combustion operation are controlled based on the determination result in the first determination unit 5.

  In the premix combustion operation, for example, a control signal is output from the control unit 8 to the in-cylinder injection valve 11 so as to have a fuel injection pattern as shown in FIG. Further, each of the low pressure throttle valve 17, the high pressure throttle valve 19, the high pressure EGR valve 22, and the low pressure EGR valve 26 is controlled so that the ratio of the EGR amount to the entire intake air amount is increased as compared with that during the diffusion combustion operation. Is done. On the other hand, in the diffusion combustion operation, a control signal is output from the control unit 8 to the in-cylinder injection valve 11 so that a fuel injection pattern as shown in FIG.

[3. flowchart]
8 to 10 are flowcharts illustrating the procedure of the above-described combustion state switching control. The flow in FIG. 8 (normal flow) is repeatedly performed in the engine control device 1 at a predetermined calculation cycle. Further, the flow of FIG. 9 (flow at the time of rapid acceleration) and the flow of FIG. 10 (flow at the time of sudden deceleration) are performed when a sudden acceleration request and a sudden deceleration request are detected in steps A11 and A12 in FIG. The

[3-1. Normal flow]
In step A1, the detection unit 2 acquires information on the accelerator opening detected by the accelerator opening sensor 34 and information on the gear position detected by the shift position sensor 35. In the subsequent step A2, it is determined whether or not the shift lever has been operated by comparing the shift stage before one cycle with the shift stage of the current cycle. When this condition is satisfied, the routine proceeds to step A3, and after the passage of time by the timer T indicating the elapsed time since the current gear position is reached, the routine proceeds to step A4. On the other hand, if the shift lever is not operated, step A3 is skipped and the process proceeds to step A4. Steps A4 to A8 correspond to the determination contents in the first determination unit 5.

In step A4, the predetermined time T ₀ is set in accordance with the current gear. The predetermined time T ₀ is shortened as the number of gears increases. In step A5, the value of the timer T and the predetermined time T ₀ is compared, whether or not a predetermined time T ₀ from the shift lever is operated has elapsed. Here, when T <T ₀ (when the predetermined time T ₀ has not elapsed), the process proceeds to step A10, where the first determination unit 5 performs diffusion combustion regardless of whether or not the execution condition of the premix combustion operation is satisfied. It is determined that the operating conditions are satisfied. On the other hand, if T ≧ T ₀ , the process proceeds to step A6.

In step A6, since the predetermined time T ₀ has already elapsed, the timer T stops counting. Further, in the subsequent step A7, an execution region for the premixed combustion operation is set according to the current gear position. For example, when the gear stage is 2nd speed, a region M2 in FIG. 3 is a region where the premixed combustion operation is performed. Further, when the gear stage is the third speed, a region M3 in FIG. 3 is a region where the premixed combustion operation is performed. As described above, the execution region of the premixed combustion operation is changed based on the shift speed of the transmission.

  In Step A8, the first determination unit 5 determines whether or not the operating point of the engine 10 exists within the execution region of the premixed combustion operation. When this condition is satisfied, the routine proceeds to step A9, where it is determined that the premixed combustion operation execution condition is satisfied. On the other hand, when the operating point is outside the premixed combustion region, the routine proceeds to step A10, where it is determined that the conditions for performing the diffusion combustion operation are satisfied. Thus, in the 1st determination part 5, the determination based on the operating point of the engine 10 and a control map as shown in FIG. 3 is implemented.

  Step A11 and subsequent steps are steps for determining whether or not the determination by the second determination unit 6 and the third determination unit 7 is in effect. Step A11 is a step performed after step A9, and step A12 is a step performed after steps A10 and A11. That is, step A11 is performed only after step A9 is performed (when the execution condition for the premixed combustion operation is satisfied).

  In step A11, it is determined whether or not a rapid acceleration request for rapidly accelerating the vehicle has been detected. For example, when the time change rate of the accelerator opening is equal to or greater than a positive predetermined value, it is determined that there is a rapid acceleration request, and the flow proceeds to the rapid acceleration flow of FIG. If the time change rate of the accelerator opening is less than a positive predetermined value, the process proceeds to step A12.

  In step A12, it is determined whether or not a rapid deceleration request for rapidly decelerating the vehicle has been detected. For example, when the time change rate of the accelerator opening is equal to or less than a negative predetermined value, it is determined that there is a rapid deceleration request, and the flow proceeds to the rapid deceleration flow in FIG. When the time change rate of the accelerator opening exceeds a negative predetermined value, the process proceeds to step A13, and either the premixed combustion operation or the diffusion combustion operation is performed according to the determination result in the first determination unit 5. The That is, the engine 10 is controlled so that it will be in the driving | running state corresponding to the step implemented just before reaching step A13 among step A9, A10.

[3-2. Sudden acceleration flow]
The rapid acceleration flow in FIG. 9 is performed when a rapid acceleration request is detected during the premixed combustion operation, and corresponds to the determination content in the second determination unit 6.
In Step B1, various information such as a supercharging pressure P, an intake oxygen concentration D, an engine load Ec, an engine speed Ne, and a rapid acceleration request are acquired. In step B2, the first lower limit value P ₁ , the first upper limit value P ₂ , the first predetermined value ΔP _TH , the second lower limit value D ₁ , and the second upper limit value D are based on the engine load Ec and the engine speed Ne. _2. Each value of the second predetermined value ΔD _TH2 is set.

In step B3, whether the boost pressure P is first less than a lower limit value P ₁ is determined. Here the flow proceeds to step B6 in the case of P <P _1, the flow proceeds to step B4 in the case of P ≧ P _1. When the supercharging pressure P is first less than a lower limit value P _1, the supercharging pressure P is in a state suitable for premix combustion operation, it said to be unsuitable state diffusion combustion operation.
In step B4, whether the boost pressure P is first upper limit value P ₂ or more greater than the first lower limit value P ₁ is determined. Here proceeds to step B10 in the case of P ≧ P _2, the flow proceeds to step B5 in the case of P <P _2. When the supercharging pressure P is first upper limit value P ₂ or more, the boost pressure P is in a state suitable for the diffusion combustion operation, it said to be unsuitable state to premix combustion operation.

In step B5, the difference [Delta] P between the target value and the actual value of the supercharging pressure P is equal to or less than a first predetermined value [Delta] P _TH is determined. Here the flow proceeds to step B6 in the case of [Delta] P <[Delta] P _TH, the process proceeds to step B10 in the case of ΔP ≧ ΔP _TH. Boost pressure P is first lower limit value P ₁ or more, when it is first less than a upper limit value P _2, the boost pressure P is in a state suitable to the diffusion combustion operation in premix combustion operation, carried out either You can also Therefore, in step B5, it is determined which one should be implemented in consideration of the convergence of the actual value that follows the target value of the supercharging pressure P.

As described above, in steps B3 to B5, the condition determination regarding the supercharging pressure P is performed. On the other hand, in the following steps B6 to B8, condition determination regarding the intake oxygen concentration D is performed. In step B6, whether intake oxygen concentration D is a second lower limit value D less than ₁ is determined. Here it proceeds to step B9 in the case of D <D _1, in the case of D ≧ D ₁ advances to step B7. When the intake oxygen concentration D is a second lower limit value D less than _1, the intake oxygen concentration D is a state suitable for premix combustion operation, it said to be unsuitable state diffusion combustion operation.

In step B7, whether intake oxygen concentration D is a second lower limit second upper limit D ₂ or greater than D ₁ is determined. Here the flow proceeds to step B10 when a D ≧ D _2, the flow proceeds to step B8 in the case of D <D _2. When the intake oxygen concentration D is second upper limit D ₂ or more, the intake oxygen concentration D is a condition suitable for the diffusion combustion operation, it said to be unsuitable state to premix combustion operation.

In Step B8, it is determined whether or not the difference ΔD between the target value and the actual value of the intake oxygen concentration D is less than a second predetermined value ΔD _TH2 . If ΔD <ΔD _TH2 , the process proceeds to step B9, and if ΔD ≧ ΔD _TH2 , the process proceeds to step B10. Intake oxygen concentration D is a second lower limit value D ₁ or more, when it is less than the second upper limit D _2, the intake oxygen concentration D is a state suitable to the diffusion combustion operation in premix combustion operation, carried out either You can also Therefore, in this step B8, it is determined which one should be implemented in consideration of the convergence of the actual value following the target value of the intake oxygen concentration D.

  When the process proceeds to step B9 according to the condition determination in steps B3 to B8, the premixed combustion operation is performed, and when the process proceeds to step B10, the diffusion combustion operation is performed. Note that the determination result in the second determination unit 6 has priority over the determination result in the first determination unit 5. Therefore, even if it is determined in step A10 of the normal flow that the conditions for performing the diffusion combustion operation are satisfied, if the process proceeds to step B9 of the rapid acceleration flow, the premixed combustion operation is performed. . The reverse is also true.

  In step B11, it is determined whether or not the rapid acceleration request is no longer detected. When this condition is satisfied, the process proceeds to step B12, and after the elapse of time by the timer U indicating the elapsed time since the sudden acceleration request is not detected, the process proceeds to step B13. On the other hand, if a sudden acceleration request has been detected, or if a sudden acceleration request has not been detected in the past calculation cycle, step B12 is skipped and the process proceeds to step B13.

In step B13, the value of the timer U and the predetermined time T ₁ is compared, whether a predetermined time from the abrupt acceleration demand is no longer detected T ₁ is has elapsed. Here, when U <T ₁ (when the predetermined time T ₁ has not elapsed), this flow ends, and the rapid acceleration flow is repeated in the next calculation cycle. On the other hand, in the case of U ≧ T _1, the process proceeds to step B14. In step B14, since the predetermined time T ₁ is already passed, the count of the timer U is stopped. In addition, the normal flow is performed in the next calculation cycle. Thereafter, control based on the determination result in the first determination unit 5 is performed.

[3-3. Sudden deceleration flow]
The rapid deceleration flow in FIG. 10 is performed when a rapid deceleration request is detected, and corresponds to the determination content in the third determination unit 7.
In Step C1, various information such as a supercharging pressure P, an intake oxygen concentration D, an engine load Ec, an engine speed Ne, a rapid deceleration request, a required load, and a vehicle speed are acquired. In Step C2, the third lower limit value P ₃ , the third upper limit value P ₄ , the third predetermined value ΔP _TH3 , the fourth lower limit value D ₃ , and the fourth upper limit value D are determined based on the engine load Ec and the engine speed Ne. _4. Each value of the fourth predetermined value ΔD _TH4 is set.

  In step C3, it is determined whether a required load is detected (whether the accelerator is on). Here, when the required load is not detected, the process proceeds to step C11, and the diffusion combustion operation is performed. That is, when a sudden deceleration request is detected, the premixed combustion operation is prohibited until the accelerator-on operation is performed, and instead, the diffusion combustion operation is performed. On the other hand, if the required load is detected, the process proceeds to step C4.

Steps C4 to C9 are steps in which the condition determination regarding the supercharging pressure P and the intake oxygen concentration D, which are parameters correlated with the noise amount of the engine 10, is performed as in the steps B3 to B8 of the rapid acceleration flow. . Here, the magnitude relationship between the boost pressure P and the third lower limit value P ₃ and the third upper limit value P ₄ is compared, and the difference ΔP between the target value and the actual value of the boost pressure P is a third predetermined value. It is determined whether it is less than ΔP _TH3 . Further, the magnitude relation between the intake oxygen concentration D and the fourth lower limit value D ₃ and the fourth upper limit value D ₄ is compared, and the difference ΔD between the target value and the actual value of the intake oxygen concentration D is less than the fourth predetermined value ΔD _TH4. It is determined whether or not.

When the supercharging pressure P is less than the third lower limit value P ₃ , the supercharging pressure P is in a state suitable for premixed combustion operation, and when the supercharging pressure P is equal to or greater than the third upper limit value P ₄ , The supercharging pressure P is in a state suitable for diffusion combustion operation. On the other hand, when the supercharging pressure P is not less than the third lower limit value P _{3 and} less than the third upper limit value P ₄ , the supercharging pressure P is suitable for both the premixed combustion operation and the diffusion combustion operation. Here, in consideration of the convergence of the actual value that follows the target value of the supercharging pressure P, it is determined which one should be implemented. The same applies to the intake oxygen concentration D.

  In Step C12 following Steps C10 and C11, it is determined whether or not the rapid deceleration request is no longer detected. When this condition is satisfied, the process proceeds to step C13, and after the elapse of time by the timer V indicating the elapsed time since the sudden deceleration request is not detected, the process proceeds to step C14. On the other hand, if a sudden deceleration request is detected or if a sudden deceleration request is no longer detected in the past calculation cycle, step C13 is skipped and the process proceeds to step C14.

In step C14, the predetermined time T ₂ is set based on the vehicle speed at that time. The predetermined time T ₂ are, as shown in FIG. 6, is set as the vehicle speed is higher short. In step C15, the value of the timer V and the predetermined time T ₂ are compared, whether or not a predetermined time after the rapid deceleration request is not detected T ₂ has elapsed. Here, when V <T ₂ (when the predetermined time T ₂ has not elapsed), this flow ends, and the rapid deceleration flow is repeated in the next calculation cycle. On the other hand, in the case of V ≧ T _2, the process proceeds to step C16. In step C16, since the predetermined time T ₂ has already passed, the count of the timer V is stopped. In addition, the normal flow is performed in the next calculation cycle. Thereafter, control based on the determination result in the first determination unit 5 is performed.

[4. Action, effect]
[4-1. Normal time]
(1) In the engine control apparatus 1 described above, the first determination unit 5 changes the execution condition of the premixed combustion operation based on the gear position of the transmission. Thereby, it is possible to switch between the premixed combustion operation and the diffusion combustion operation in consideration of the difference between the traveling sound and the operating sound depending on the shift speed. That is, it is possible to accurately grasp the running state in which the sound emitted from the engine 10 is likely to be masked by sounds other than the engine 10, for example, to accurately grasp the operating state in which noise that may occur in the premixed combustion operation is likely to be blocked. Can do. Therefore, the drive feeling can be improved while improving the exhaust performance, and both the exhaust performance and the quietness of the vehicle can be improved.

  (2) In the engine control apparatus 1, as shown in FIG. 3, the smaller the speed reduction ratio of the transmission, the larger the execution region of the premixed combustion operation is in the increasing direction (right direction) of the engine speed Ne. Yes. Thus, by increasing the upper limit value of the engine speed Ne for performing the premixed combustion operation, the premixed combustion operation can be performed in a state where the engine 10 is at a higher speed, and the exhaust performance is improved. Can be made. Further, when the engine 10 is in a high rotation state, the noise that can be generated in the premixed combustion operation is easily shielded by the traveling noise, so that the drive feeling can be improved.

  (3) In the engine control apparatus 1 described above, as shown in FIG. 3, the smaller the reduction ratio of the transmission, the larger the execution region of the premixed combustion operation is in the increasing direction (upward direction) of the engine load Ec. . Thus, by increasing the upper limit value of the engine load Ec for performing the premixed combustion operation, the premixed combustion operation can be performed with the engine 10 at a higher load, and the exhaust performance is improved. be able to. Further, when the engine 10 is in a high load state, the noise that can be generated in the premixed combustion operation is shielded by the traveling noise, so that the drive feeling can be improved.

  (4) As shown in FIG. 3, the minimum speed stage in which the premixed combustion operation execution region is expanded in the increasing direction (right direction) of the engine speed Ne is the second speed. On the other hand, the minimum gear position in which the premixed combustion operation execution region is expanded in the increasing direction (upward direction) of the engine load Ec is the third speed. In this way, by preferentially increasing the engine speed Ne over the engine load Ec and increasing the upper limit value, the premixed combustion operation can be performed in an operation state with a high noise shielding effect, and the drive feeling is improved. Further improvement can be achieved.

(5) In the engine control apparatus 1 described above, the premixed combustion operation is performed at least after a predetermined time T ₀ has elapsed since the shift speed has changed. Thereby, for example, even if the intake air amount and the EGR amount change transiently immediately after the shift change, the combustion stability can be ensured by performing the normal diffusion combustion operation. That is, the premixed combustion operation can be started avoiding the unstable combustion state immediately after the shift change, and the combustion stability of the engine 10 can be improved.

(6) The predetermined time T ₀ is set to be shorter as the speed reduction ratio of the gear is smaller. Thereby, the premixed combustion operation can be started promptly while improving the combustion stability of the engine 10.
(7) When the above method 3 is adopted as the method for setting the predetermined time T ₀ , it is possible to suppress a decrease in combustion stability due to an intake air delay or a supercharging delay, and an engine in a premixed combustion operation. The combustion stability of 10 can be improved.

[4-2. During sudden acceleration]
(1) In the engine control apparatus 1 described above, when a rapid acceleration request is detected during the premixed combustion operation, the premixed combustion operation is continued using a condition including a parameter that correlates with the noise amount of the engine 10. Whether to switch the premixed combustion operation to the diffusion combustion operation is determined. As described above, by using the condition including the parameter correlated with the noise amount, the premixed combustion operation can be continued in a range in which the noise does not give the driver a sense of incongruity, and the exhaust performance can be improved. Further, since the premixed combustion operation is switched to the diffusion combustion operation in an operation state in which noise can increase, the noise does not increase excessively, and the drive feeling can be improved while improving the exhaust performance.

  (2) In the engine control device 1 described above, as a parameter correlated with the amount of noise, a physical quantity that reflects the component ratio of the fuel mixture such as the supercharging pressure P and the intake oxygen concentration D of the engine 10 (which affects the combustion speed). Physical quantity). As a result, it is possible to accurately grasp the timing at which the fuel mixture easily burns rapidly, and to improve quietness and drive feeling.

  In addition, when the supercharging pressure P is used as the above parameter, the amount of air introduced into the cylinder can be estimated with high accuracy, and the operating state of the engine 10 where noise is likely to increase is accurately grasped. can do. In addition, when the intake oxygen concentration D is used, the amount of oxygen burned in the cylinder can be estimated with high accuracy, and the behavior of the combustion speed can be accurately grasped. Therefore, drive feeling can be further improved.

(3) When a rapid acceleration request is detected during the premixed combustion operation, the engine control device 1 compares the boost pressure P and the intake oxygen concentration D with two threshold values (upper limit value and lower limit value). Is done. For example, as shown in FIG. 5 (A), (B) , and if the boost pressure P is first less than a lower limit value P _1, when the intake oxygen concentration D is a second lower limit value D less than ₁ The premixed combustion operation is continued. On the other hand, if the boost pressure P is first upper limit value P ₂ or more and, when the intake oxygen concentration D is second upper limit D ₂ or more, premix combustion operation is switched to the diffusion combustion operation.
Thus, the determination using the two types of thresholds having different sizes can give flexibility to the control content in the intermediate region, and the combustion mode suitable for the operating state of the engine 10 can be selected.

  Further, when rapid acceleration is requested during the premixed combustion operation, the engine load Ec increases in response to the rapid acceleration request, and the parameter correlated with the noise amount of the engine 10 gradually increases. Since the premixed combustion operation is continued when these parameters are still small, the exhaust performance can be improved within a range in which the noise does not increase excessively. Thereafter, even if the parameter increases, the premixed combustion operation is switched to the diffusion combustion operation, so that the generation of noise can be suppressed.

  (4) If the threshold value is set based on the engine load Ec and the engine speed Ne, it is possible to provide a judgment criterion suitable for every operating state of the engine 10, and an operation in which the noise of the engine 10 is likely to increase. While being able to grasp a state accurately, the noise suppression effect can be enhanced.

(5) In the engine control apparatus 1 described above, when the parameter value is located between two threshold values (upper limit value and lower limit value), the determination based on the difference between the target value and the actual value is performed. For example, as shown in FIG. 5A, if the difference ΔP is less than the first predetermined value ΔP _TH , the premixed combustion operation is continued, and when the difference ΔP becomes equal to or greater than the first predetermined value ΔP _TH , The premixed combustion operation is switched to the diffusion combustion operation. In this way, by selecting the combustion type in consideration of the convergence of the parameter that correlates with the noise level, it is possible to accurately grasp the overshoot from the target value of that parameter, and to generate noise more accurately. Can be suppressed.

(6) A predetermined value (for example, a first predetermined value ΔP _TH and a second predetermined value ΔD _TH2 ) to be compared with respect to the difference between the target value and the actual value is based on the engine load Ec and the engine speed Ne. If set, determination criteria suitable for all operating states of the engine 10 can be given, the operating state in which the noise of the engine 10 is likely to increase can be accurately grasped, and the noise suppression effect can be enhanced.

[4-3. During sudden deceleration]
(1) In the premixed combustion operation, as shown in FIG. 2D, the in-cylinder pressure fluctuates more steeply than in the diffusion combustion operation, and noise due to combustion tends to increase. Therefore, if the premixed combustion operation is performed in an operation state where a large load is not applied to the engine 10, the noise increases even though the engine 10 is not working, and the driver feels uncomfortable.
On the other hand, in the engine control apparatus 1 described above, the premixed combustion operation is prohibited while the rapid deceleration request is detected, and the diffusion combustion operation is performed instead. For example, even when it is determined by the first determination unit 5 that the conditions for performing the premixed combustion operation are satisfied, if the driver's accelerator-off operation is detected, the premixed combustion operation is prohibited. .

  In this way, by performing the diffusion combustion operation while prohibiting the premixed combustion operation during the detection of the rapid deceleration request, it is possible to prevent the generation of noise in the no-load state (low load state) immediately after the accelerator-off operation. And drive feeling can be improved. In addition, during a normal deceleration operation that is not a sudden deceleration operation (for example, during an accelerator loosening operation in which the time change rate of the accelerator opening is a negative negative value or more), the premixed combustion operation is not prohibited. Exhaust performance can be improved. Therefore, both the exhaust performance and the quietness of the vehicle can be improved.

(2) In the above-described engine control device 1, during the period from the rapid deceleration request is not detected until the predetermined time T ₂ has elapsed, the diffusion combustion operation is carried out premix combustion operation is prohibited. Thus, since the premixed combustion operation is prohibited until the fluctuation of the combustion state accompanying the rapid deceleration of the vehicle is stabilized, quietness and drive feeling can be improved.

(3) In the engine control apparatus 1, as shown in FIG. 6, the predetermined time T ₂ is set shorter as the vehicle speed increases, and the predetermined time T ₂ is set longer as the vehicle speed decreases. With such a setting, the prohibition period of the premixed combustion operation in a traveling state where the traveling noise of the vehicle is relatively low can be lengthened, and quietness can be improved. On the other hand, in a traveling state where the traveling noise of the vehicle is relatively loud, the prohibition period of the premixed combustion operation can be shortened, and the exhaust performance can be improved.

(4) In addition, as shown in FIGS. 7A and 7B, for each of the supercharging pressure P and the intake oxygen concentration D, the time until the difference between the target value and the actual value becomes a predetermined value or less is set. The predetermined time T ₂ can also be used. In this case, since the premixed combustion operation is prohibited until the supercharging pressure P and the intake oxygen concentration D sufficiently converge, and the premixed combustion operation is performed after the convergence, the combustion stability and quietness of the engine 10 are suppressed. Can be further improved.

  (5) In the engine control apparatus 1 described above, when a required load occurs while the premixed combustion operation is prohibited, the prohibition is canceled and the premixed combustion operation is permitted. For example, when the accelerator pedal is depressed during the prohibition of the premixed combustion operation, the premixed combustion operation is performed if the operating point is located within the execution region of the premixed combustion operation. Thus, the exhaust performance can be improved by canceling the prohibition of the premixed combustion operation in accordance with the acceleration start timing. Since the work of the engine 10 increases during acceleration, even if noise is generated by starting the premixed combustion operation, it is difficult for the driver to feel uncomfortable and the drive feeling can be prevented from being lowered. .

  (6) As a condition for canceling the prohibition of the premixed combustion operation, “parameters correlated with the amount of noise of the engine 10 (for example, supercharging pressure P, intake oxygen concentration D, intake air temperature, humidity, intake air density, etc.) It is also possible to use "conditions including") together. In this case, the premixed combustion operation can be started in a state where the parameter correlated with the noise amount of the engine 10 has converged, and the combustion stability and quietness of the engine 10 can be further improved.

[5. Modified example]
Regardless of the embodiment described above, various modifications can be made without departing from the spirit of the invention. Each structure of this embodiment can be selected as needed, or may be combined appropriately.

In the above-described embodiment, the correspondence relationship between the operating point and the combustion state is exemplified by the map shown in FIG. 3, but the shape and the number of regions of each of the regions M1 to M4 shown on the map are shown here. It is not limited. In particular, it is desirable that the specific shapes of the regions M1 to M4 are set in consideration of vehicle running characteristics and drive feeling.
Further, the map shown in FIG. 3 shows the relationship between the operating points corresponding to the engine speed Ne and the engine load Ec and the respective regions M1 to M4. The vehicle traveling state is at least the engine load Ec. It is possible to grasp based on either one of the engine speed Ne. The association between the operating point and the combustion state can be determined using inequalities or mathematical expressions as shown in Table 1, for example.

  In the above-described embodiment, control with a diesel engine has been described, but this control can also be applied to a gasoline engine. If the engine performs at least the premixed combustion operation and the diffusion combustion operation in accordance with the traveling state of the vehicle, the same effects as those of the above-described embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Engine control apparatus 2 Detection part 3 Map memory | storage part 4 Determination part 5 1st determination part 6 2nd determination part 7 3rd determination part 8 Control part 10 Engine

Claims (6)

In an engine control device that switches between premixed combustion operation and diffusion combustion operation according to the running state of the vehicle,
Based on the driving operation of the driver, a detection unit for detecting the presence or absence of a sudden deceleration request for suddenly decelerating the vehicle;
A determination unit that prohibits the premixed combustion operation and permits the diffusion combustion operation while the rapid deceleration request is detected by the detection unit ;
The determination unit prohibits the premixed combustion operation and permits the diffusion combustion operation until a predetermined time elapses after the sudden deceleration request is not detected, and
The engine control apparatus according to claim 1, wherein the predetermined time is shorter as the vehicle speed of the vehicle is higher.   In an engine control device that switches between premixed combustion operation and diffusion combustion operation according to the running state of the vehicle,
  Based on the driving operation of the driver, a detection unit for detecting the presence or absence of a sudden deceleration request for suddenly decelerating the vehicle;
  A determination unit that prohibits the premixed combustion operation and permits the diffusion combustion operation while the rapid deceleration request is detected by the detection unit;
  The determination unit prohibits the premixed combustion operation and permits the diffusion combustion operation until a predetermined time elapses after the sudden deceleration request is not detected, and
  The predetermined time is a time until the difference between the target value and the actual value becomes a predetermined value or less for each of the supercharging pressure and the intake oxygen concentration of the engine.
An engine control device.   In an engine control device that switches between premixed combustion operation and diffusion combustion operation according to the running state of the vehicle,
  Based on the driving operation of the driver, a detection unit for detecting the presence or absence of a sudden deceleration request for suddenly decelerating the vehicle;
  A determination unit that prohibits the premixed combustion operation and permits the diffusion combustion operation while the rapid deceleration request is detected by the detection unit;
  The determination unit prohibits the premixed combustion operation and permits the diffusion combustion operation until a predetermined time elapses after the sudden deceleration request is not detected, and
  The determination unit cancels the prohibition and permits the premixed combustion operation when a required load occurs while the premixed combustion operation is prohibited.
An engine control device. The predetermined time is, for each of the boost pressure and the intake oxygen concentration of the engine, wherein the difference between the target value and the actual value is the time until a predetermined value or less, according to claim 1 or 3, wherein Engine control device. The determination unit, when the required load occurs while the premix combustion operation is prohibited, and permits the premix combustion operation to release the prohibition, according to claim 1 or 2 Or the engine control apparatus of 4 . The determination unit determines whether or not to cancel the prohibition using a condition including a parameter that correlates with a noise amount of the engine when a required load occurs while the premixed combustion operation is prohibited. 6. The engine control device according to claim 3 or 5 , wherein the determination is performed.

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