JP2020190205A - Control device for engine and engine system - Google Patents

Abstract

To prevent the lowering of fuel consumption performance by suppressing unnecessary fuel pressure rise while removing deposits from an injection hole of a fuel injection valve with fuel pressure rise.SOLUTION: An ECU 20 includes a deposit estimation part 27 for performing processing to estimate a deposit accumulation amount in an injection hole 15B of an injector 15 (step S2), and a fuel pressure control part 26 for allowing the fuel pressure rise of the injector 15 when the deposit accumulation amount is equal to or greater than a predetermined value. When the deposit accumulation amount estimated by the deposit estimation part 27 is equal to or greater than the predetermined value, the fuel pressure control part 26 switches from a basic fuel pressure map to a deposit removing fuel pressure map to control a high pressure fuel pump 153 (step S8). When an engine speed region is divided into a high speed region where the speed is relatively high and a low speed region where the speed is relatively low, if the high speed region is shown in the deposit removing fuel pressure map, however, the fuel pressure rise is restricted.SELECTED DRAWING: Figure 10

Description

The present invention relates to an engine control device including a fuel injection valve that injects fuel directly into a piston cavity, and an engine system to which the fuel injection valve is applied.

In a direct injection engine, for example, a fuel injection valve is arranged so that the injection hole is exposed on the ceiling surface of the combustion chamber. In this case, a deposit (carbon) may adhere to the injection hole, which may deteriorate the fuel discharge performance from the injection hole. One of the causes of the deposit is that the injected fuel adheres to the vicinity of the injection hole and the fuel is burned and hardened by combustion in the combustion chamber. Patent Document 1 discloses a technique for performing cleaning control for increasing the fuel pressure of the fuel injection valve in order to remove the deposit adhering to the vicinity of the injection hole.

Generally, the fuel pressure is adjusted to a desired value by controlling a fuel pressure adjusting valve provided in a high-pressure fuel pump that supplies fuel from a fuel tank to a fuel injection valve. Further, the high-pressure fuel pump is generally driven by a pump drive cam attached to a camshaft (engine cam) to which power is transmitted from a crankshaft.

JP-A-2018-62923

The increase in fuel pressure is effective in removing the deposit. However, an increase in fuel pressure causes an increase in the mechanical load of the high-pressure fuel pump. Normally, when the engine speed is high, the fuel injection amount per unit time increases as compared with the case where the engine speed is low. For this reason, it can be said that the fuel injection amount is originally large during high-speed operation, and the deposit cleaning operation is naturally executed. Nevertheless, increasing the fuel pressure for cleaning control of the deposit leads to unnecessarily increasing the mechanical load of the high-pressure fuel pump, resulting in deterioration of fuel efficiency. That is, when it is predicted that a deposit is accumulated in the injection hole, if a control mode is adopted such that the fuel pressure is uniformly increased, the fuel pressure is increased unnecessarily without much difference in the cleaning effect, and the high-pressure fuel is used. The problem arises of increasing the mechanical load of the pump.

An object of the present invention is an engine control device capable of preventing a decrease in fuel efficiency performance by suppressing an unnecessary increase in fuel pressure while removing a deposit in an injection hole of a fuel injection valve by increasing the fuel pressure. It is to provide an applied engine system.

The combustion chamber structure of the engine according to one aspect of the present invention is arranged in a combustion chamber partially partitioned by a piston having a cavity on the crown surface, and includes a fuel injection valve that injects fuel directly into the cavity. An engine control device based on a fuel pressure adjusting mechanism that adjusts the fuel pressure of fuel supplied to the fuel injection valve, a control unit that controls the fuel injection valve and the fuel pressure adjusting mechanism, and an operating state of the engine. The control unit includes a deposit estimation unit that performs a process of estimating the deposit accumulation amount in the injection hole of the fuel injection valve, and the control unit is described when the deposit accumulation amount estimated by the deposit estimation unit becomes a predetermined value or more. When the fuel pressure adjusting mechanism is controlled so as to increase the fuel pressure, while the rotation region of the engine is divided into at least a high rotation region having a relatively high rotation speed and a low rotation region having a relatively low rotation speed. In the case of the high rotation region, the fuel pressure is limited to increase.

According to this control device, when the deposit deposit amount becomes a predetermined value or more, the control unit raises the fuel pressure and executes a process of removing the deposit. However, even if the deposit deposit amount exceeds a predetermined value, if the engine rotation region is in the high rotation region, the control unit limits the increase in fuel pressure. That is, in the high rotation speed region where the fuel injection amount is originally large, the cleaning effect of the deposit can be expected, so that the increase in the fuel pressure is limited. As a result, substantially unnecessary fuel pressure increase control can be suppressed, an increase in mechanical loss of the engine such as the mechanical load of the high-pressure fuel pump can be suppressed, and eventually a deterioration in fuel efficiency can be prevented.

In the above control device, a storage unit for storing a basic fuel pressure map in which the set fuel pressure is set in advance according to the engine speed is further provided, and in a predetermined range of the basic fuel pressure map, the fuel pressure in the high rotation speed region is The fuel pressure is set higher than the fuel pressure in the low rotation speed region, and the control unit causes the fuel pressure adjusting mechanism to set the fuel pressure based on the basic fuel pressure map, and the deposit deposit amount is set to a predetermined value or more. When the engine speed is in the high speed range, it is desirable to limit the increase in fuel pressure.

According to this control device, the fuel pressure is set based on the basic fuel pressure map, and the control of limiting the increase in the fuel pressure is executed in the high rotation region in the predetermined range of the basic fuel pressure map. Can be simplified.

In the above control device, it is desirable that the control unit prohibits the increase in fuel pressure when the engine speed is in the high speed region. As a result, it is possible to surely suppress an increase in unnecessary mechanical loss of the engine.

Alternatively, it is desirable that the control unit reduces the degree of increase in the fuel pressure when the engine speed is in the high speed region. As a result, it is possible to suppress an increase in unnecessary mechanical loss of the engine.

In the above control device, in addition to the basic fuel pressure map, the storage unit stores a deposit removal fuel pressure map in which the fuel pressure for removing the deposit accumulated in the injection hole is predetermined according to the engine speed. In the deposit-removed fuel pressure map, the fuel pressure is set higher than that of the basic fuel pressure map in the low rotation speed region, and is set to the same fuel pressure as the basic fuel pressure map in the high rotation speed region. Therefore, it is desirable that the control unit applies the deposit removal fuel pressure map to cause the fuel pressure adjusting mechanism to set the fuel pressure when the deposit accumulation amount becomes a predetermined value or more.

According to this control device, it is sufficient to simply switch between the basic fuel pressure map and the deposit-removed fuel pressure map to set the fuel pressure depending on whether or not the deposit deposit amount is equal to or higher than a predetermined value. Therefore, control in the control unit can be performed. It can be simplified.

The engine system according to another aspect of the present invention includes a combustion chamber partially partitioned by a piston having a cavity on the crown surface, and a fuel injection valve arranged in the combustion chamber and injecting fuel directly toward the cavity. The engine main body including the above, the control device, and the head portion of the fuel injection valve provided with the injection hole are such that the combustion chamber faces the cavity in the vicinity of the radial center of the combustion chamber. It is located on the ceiling of the room.

In this engine system, the fuel injection valve is arranged vertically from above the combustion chamber toward the cavity in a so-called center injection type arrangement. Since this arrangement is such that the fuel injected from the cavity is likely to bounce off and deposits are likely to occur, the deposit removing process due to the increase in fuel pressure related to the control of the control device is more effective.

In the above engine system, a fuel supply device including a tank for storing fuel and a pump for delivering fuel from the tank to the fuel injection valve is further provided, the fuel pressure adjusting mechanism is the pump, and the pump is the pump. It operates by being given a mechanical driving force from the engine body, and it is desirable that the control unit adjusts the fuel pressure by controlling the output of the pump.

According to this engine system, the mechanical drive resistance of the pump increases as the fuel pressure increases. However, the control of suppressing the increase in fuel pressure by the above control device can prevent the mechanical drive resistance of the pump from being unnecessarily increased for the purpose of removing the deposit.

According to the present invention, an engine control device capable of preventing a decrease in fuel efficiency performance by suppressing an unnecessary increase in fuel pressure while removing a deposit in an injection hole of a fuel injection valve by increasing the fuel pressure, and a control device thereof. An applied engine system can be provided.

FIG. 1 is a diagram showing an overall configuration of an engine system to which an engine control device according to the present invention is applied. FIG. 2 is a view showing a cross-sectional view of the engine body and a plan view of the piston together. FIG. 3 is a schematic perspective view of one cylinder included in the engine. FIG. 4 is a block diagram showing an engine control system. 5 (A) to 5 (C) are operation maps in which the operating areas of the engine are divided according to the difference in combustion form. FIG. 6 is an example of a basic fuel pressure map used when setting the fuel pressure of the injector in SI combustion and SPCCI_λ = 1 combustion. FIG. 7 is an example of a basic fuel pressure map used when setting the fuel pressure of the injector in SPCCI_λ> 1 combustion. FIG. 8 is an example of a deposit removal map used when the injector cleaning mode is executed in SI combustion and SPCCI_λ = 1 combustion. 9 (A) and 9 (B) are time charts showing an example of the pulse width of the injector control pulse, and (C) is a graph showing the relationship between the pulse width and the fuel injection amount. FIG. 10 is a flowchart showing an example of fuel pressure switching control of the injector.

[Overall engine configuration]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the overall configuration of the engine system to which the engine control device according to the present invention is applied will be described with reference to the system diagram shown in FIG. The engine shown in FIG. 1 is a 4-cycle gasoline direct injection engine mounted on a vehicle as a power source for traveling, and includes an engine body 1, an intake passage 30 through which intake air introduced into the engine body 1 flows, and an intake passage 30. The exhaust passage 40 through which the exhaust gas discharged from the engine body 1 flows, the external EGR device 45 that returns a part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30, and the engine body 1 containing gasoline as a main component. It is equipped with a fuel supply system 150 for supplying fuel to the engine.

The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 attached to the upper surface of the cylinder block 3 so as to block the cylinder 2 from above, and a piston 5 housed in the cylinder 2. And have. The engine body 1 is typically a multi-cylinder type having a plurality of (for example, four) cylinders, but FIG. 1 shows only one cylinder 2 for simplification. FIG. 2 shows a cross-sectional view of the engine body 1 and a plan view of the piston 5. Further, in FIG. 3, one cylinder 2 is shown in a schematic perspective view. The piston 5 has an outer diameter corresponding to the bore diameter of the cylinder 2, and is housed in the cylinder 2 so as to be reciprocally slidable with a predetermined stroke. Below the piston 5, a crankshaft 7, which is an output shaft of the engine body 1, is provided. The crankshaft 7 is connected to the piston 5 via a connecting rod 8 and is rotationally driven around the central axis according to the reciprocating motion of the piston 5.

A combustion chamber 6 is partitioned above the piston 5. The fuel is supplied to the combustion chamber 6 by injection from an injector 15 described later. The supplied fuel burns while being mixed with air in the combustion chamber 6, and the piston 5 pushed down by the expansion force due to the combustion reciprocates in the vertical direction. The combustion chamber wall surface that partitions the combustion chamber 6 is the inner wall surface of the cylinder 2, the crown surface 50 that is the upper surface of the piston 5, and the combustion chamber ceiling surface 6U (intake valve 11 and exhaust valve 12) that is the bottom surface of the cylinder head 4. Includes each valve surface). The combustion chamber ceiling surface 6U has a pent roof type shape that is convex upward.

The geometric compression ratio of the cylinder 2, that is, the ratio of the volume of the combustion chamber 6 when the piston 5 is at the top dead center and the volume of the combustion chamber 6 when the piston 5 is at the bottom dead center is determined by SPCCI combustion described later. As a value suitable for (partial compression ignition combustion), a high compression ratio of 15 or more and 30 or less, preferably 15 or more and 18 or less is set. By setting the geometric compression ratio to a high compression ratio of 15 or more, it is possible to create an environment in which compression ignition is likely to occur in the air-fuel mixture in the combustion chamber 6.

A crank angle sensor SN1 and a water temperature sensor SN2 are assembled to the cylinder block 3. The crank angle sensor SN1 detects the rotation angle (crank angle) of the crankshaft 7 and the rotation speed (engine rotation speed) of the crankshaft 7. The water temperature sensor SN2 detects the temperature (engine water temperature) of the cooling water flowing inside the cylinder block 3 and the cylinder head 4.

On the combustion chamber ceiling surface 6U of the cylinder head 4, there are an intake port 9 and an exhaust port 10 that open toward the combustion chamber 6, an intake valve 11 that opens and closes the intake port 9, and an exhaust valve 12 that opens and closes the exhaust port 10. Is provided. As shown in FIGS. 2 and 3, the valve type of the engine of the present embodiment is a 4-valve type of 2 intake valves x 2 exhaust valves. The intake port 9 has a first intake port 9A and a second intake port 9B, and the exhaust port 10 has a first exhaust port 10A and a second exhaust port 10B. One intake valve 11 is provided for each of the first intake port 9A and one for the second intake port 9B, and one exhaust valve 12 is provided for each of the first exhaust port 10A and the second exhaust port 10B. There is. Of the first and second intake ports 9A and 9B, the second intake port 9B is provided with a swirl valve 17 capable of opening and closing the second intake port 9B (FIG. 1).

The intake valve 11 and the exhaust valve 12 are opened and closed and driven in conjunction with the rotation of the crankshaft 7 by the valve operating mechanisms 13 and 14 including a pair of camshafts and the like arranged on the cylinder head 4. The valve mechanism 13 for the intake valve 11 has an intake VVT 13a that can change the opening / closing timing of the intake valve 11, and the valve mechanism 14 for the exhaust valve 12 has an exhaust VVT 14a that can change the opening / closing timing of the exhaust valve 12. However, each is built-in. The intake and exhaust VVTs 13a and 14a are so-called phase-type variable mechanisms that change the opening and closing times of the intake valve 11 and the exhaust valve 12 at the same time and by the same amount.

An injector 15 (fuel injection valve) and a spark plug 16 are assembled to the cylinder head 4. The injector 15 injects the fuel supplied from the fuel supply system 150 directly into the combustion chamber 6. The spark plug 16 ignites a mixture of fuel injected from the injector 15 into the combustion chamber 6 and air introduced into the combustion chamber 6 through the intake ports 9 (9A, 9B). The cylinder head 4 is further provided with an in-cylinder pressure sensor SN3 that detects the pressure (in-cylinder pressure) of the combustion chamber 6. As shown in FIG. 2, the injector 15 is arranged near the radial center of the combustion chamber ceiling surface 6U, and the head portion 15A at the tip is exposed near the top of the pent roof. Further, the spark plug 16 is a slope portion of the pent roof on the ceiling surface 6U of the combustion chamber, and is arranged so that the tip portion (electrode portion) is exposed between the pair of intake ports 9A and 9B.

The injector 15 is a multi-injector type injector provided with a plurality of injection holes 15B in the head portion 15A, and can inject fuel radially from the plurality of injection holes 15B. The region of reference numeral F in FIG. 2 represents the spray of fuel injected from each injection hole 15B. A cavity 51 is formed in the crown surface 50 of the piston 5 so that the radial central region thereof is recessed on the opposite side (lower side) of the cylinder head 4. The head portion 15A of the injector 15 is arranged on the ceiling surface 6U of the combustion chamber so as to face the cavity 51 near the radial center of the combustion chamber 6, and fuel is directly injected from the injection hole 15B toward the cavity 51.

Deposits may accumulate in the nozzle 15B. The deposit is generated when the injected fuel adheres to the vicinity of the injection hole 15B and the adhered fuel is burned and hardened by combustion in the combustion chamber 6. If the injection hole 15B is clogged or the opening of the injection hole 15B is narrowed due to the accumulation of deposits, the required fuel is not supplied to the combustion chamber 6, and the combustion state deteriorates. In the present embodiment, the deposit deposit amount in the injection hole 15B is estimated based on the operating state of the engine, and when the deposit accumulation amount becomes a predetermined value or more, the fuel pressure of the fuel injected from the injection hole 15B is increased to make the deposit. The cleaning mode is executed to remove. This point will be described in detail later.

As shown in FIG. 2, the cavity 51 of the piston 5 includes a bottom portion 511 formed of a substantially flat surface, and a side wall 512 that curves upward from the side peripheral edge of the bottom portion 511 and rises. A ridgeline portion 513 protruding upward corresponding to the pent roof shape of the combustion chamber ceiling surface 6U and a squish portion 514 composed of a semicircular flat surface are formed on the outer side of the crown surface 50 in the radial direction from the cavity 51. (Fig. 3).

The fuel supply system 150 that supplies fuel to the injector 15 includes a fuel tank 151, a low pressure fuel pump 152, a high pressure fuel pump 153 (fuel pressure adjusting mechanism), a fuel rail 154, and a purge passage 155. The fuel tank 151 is a tank for storing fuel. The low-pressure fuel pump 152 is an in-tank type pump, which pumps fuel from the fuel tank 151 and sends it to the high-pressure fuel pump 153. The high-pressure fuel pump 153 is a reciprocating pump that boosts the fuel sent from the low-pressure fuel pump 152 and supplies it to the fuel rail 154. The fuel rail 154 distributes fuel to the injectors 15 provided in each cylinder 2. The purge passage 155 is a passage for recovering the vaporized fuel in the fuel tank 151, introducing the fuel into the intake passage 30, and burning the fuel.

The high-pressure fuel pump 153 functions as a mechanism for adjusting the fuel pressure of the fuel supplied to the injector 15. The high pressure fuel pump 153 includes a plunger and a solenoid valve for adjusting the fuel pressure. The plunger abuts on a pump cam attached to a camshaft that drives the exhaust valve 12 and is driven to increase the fuel pressure. The solenoid valve is a valve that adjusts the fuel pressure of the fuel supplied to the injector 15 to a set value.

The intake passage 30 is connected to one side surface of the cylinder head 4 so as to communicate with the intake port 9. The air (fresh air) taken in from the upstream end of the intake passage 30 is introduced into the combustion chamber 6 through the intake passage 30 and the intake port 9. In the intake passage 30, in order from the upstream side, an air cleaner 31 that removes foreign matter in the intake air, an openable / closable throttle valve 32 that adjusts the flow rate of the intake air, and a supercharger 33 that sends out the intake air while compressing the intake air are excessive. An intercooler 35 for cooling the intake air compressed by the turbocharger 33 is provided.

At appropriate locations in the intake passage 30, there are air flow sensors SN4 that detect the flow rate of intake air, first and second intake air temperature sensors SN5 and SN7 that detect the temperature of intake air, and first and second suction that detect the pressure of intake air. Atmospheric pressure sensors SN6 and SN8 are provided. The air flow sensor SN4 and the first intake air temperature sensor SN5 are provided at a portion between the air cleaner 31 and the throttle valve 32 in the intake passage 30, and detect the flow rate and temperature of the intake air passing through the portion. The first intake pressure sensor SN6 is provided between the throttle valve 32 and the supercharger 33 in the intake passage 30 and is provided at a portion downstream of the connection port of the EGR passage 451 described later, and passes through the portion. Detects intake pressure. The second intake air temperature sensor SN7 is provided at a portion between the supercharger 33 and the intercooler 35 in the intake passage 30, and detects the temperature of the intake air passing through the portion. The second intake pressure sensor SN8 detects the pressure of intake air between the intercooler 35 and the intake port 9 in the intake passage 30.

The supercharger 33 is a mechanical supercharger (supercharger) that is mechanically linked to the engine body 1. The supercharger 33 is provided with an electromagnetic clutch 34 capable of electrically switching between engagement and release. When the electromagnetic clutch 34 is engaged, the driving force is transmitted from the engine body 1 to the supercharger 33, and the intake air is supercharged by the supercharger 33. On the other hand, when the electromagnetic clutch 34 is released, the transmission of the driving force is cut off, and the supercharging by the supercharger 33 is stopped.

The intake passage 30 is provided with a bypass passage 36 for passing the intake air by bypassing the supercharger 33. The bypass passage 36 is provided with a bypass valve 37 capable of opening and closing the bypass passage 36. The bypass passage 36 branches from the intake passage 30 on the upstream side of the supercharger 33, and forms a merging portion 38 that joins the intake passage 30 on the downstream side of the intercooler 35. The merging portion 38 is arranged in the vicinity of the surge tank (not shown). The bypass passage 36 is also a passage connecting the EGR passage 451 described later and the surge tank.

The exhaust passage 40 communicates with the exhaust port 10 of each cylinder 2 via the exhaust manifold 41. The burnt gas generated in each combustion chamber 6 is discharged to the outside through the exhaust port 10, the exhaust manifold 41, and the exhaust passage 40. The exhaust passage 40 is provided with an upstream catalytic converter 42 and a downstream catalytic converter 43, respectively, on the upstream side and the downstream side in the exhaust gas flow direction. The upstream catalyst converter 42 includes a three-way catalyst 421 and a GPF (gasoline particulate filter) 422. The three-way catalyst 421 collects harmful components (HC, CO, NOx) contained in the exhaust gas flowing through the exhaust passage 40. GPF422 collects particulate matter typified by soot contained in the exhaust gas. The downstream catalyst converter 43 is a catalyst converter containing an appropriate catalyst such as a three-way catalyst or a NOx catalyst.

A linear O ₂ sensor SN9 for detecting the concentration of oxygen contained in the exhaust gas is arranged in a portion of the exhaust passage 40 on the upstream side of the upstream catalytic converter 42. The linear O ₂ sensor SN9 is a sensor whose output value changes linearly according to the density of oxygen concentration, and it is possible to estimate the air-fuel ratio of the air-fuel mixture based on the output value. Further, a NOx sensor SN10 for measuring the NOx concentration in the exhaust gas is arranged between the three-way catalyst 421 and the GPF 422.

The external EGR device 45 has an EGR passage 451 that connects the exhaust passage 40 and the intake passage 30, and an EGR cooler 452 and an EGR valve 453 provided in the EGR passage 451. The EGR passage 451 connects a portion of the exhaust passage 40 downstream of the upstream catalytic converter 42 and a portion of the intake passage 30 between the throttle valve 32 and the supercharger 33 to each other. The EGR cooler 452 cools the exhaust gas (external EGR gas) that is returned from the exhaust passage 40 to the intake passage 30 through the EGR passage 451 by heat exchange. The EGR valve 453 is arranged in the EGR passage 451 on the downstream side of the EGR cooler 452, and adjusts the flow rate of the exhaust gas flowing through the EGR passage 451.

[Control system]
Subsequently, the above-mentioned engine control system will be described. FIG. 4 is a block diagram showing an engine control system. The control system includes an ECU 20 (control unit). The ECU 20 is a microprocessor for comprehensively controlling the engine, and is composed of a well-known CPU, ROM, RAM, and the like.

Detection signals from various sensors are input to the ECU 20. ECU20 is a crank angle sensor SN1 described above, the water temperature sensor SN2, cylinder pressure sensor SN3, an air flow sensor SN4, first and second intake air temperature sensor SN5, SN7, first and second intake pressure sensor SN6, SN8, linear _{O 2} It is electrically connected to the sensor SN9 and the NOx sensor SN10. Information detected by these sensors (that is, crank angle, engine rotation speed, engine water temperature, in-cylinder pressure, intake flow rate, intake temperature, intake pressure, exhaust gas oxygen concentration, NOx concentration, etc.) is sequentially input to the ECU 20. To. Further, the vehicle is provided with an accelerator sensor SN11 that detects the opening degree of the accelerator pedal (not shown). The detection signal by the accelerator sensor SN11 is also input to the ECU 20.

The ECU 20 controls each part of the engine while executing various determinations, calculations, and the like based on the input information from the above sensors. That is, the ECU 20 is electrically connected to the intake VVT 13a, the exhaust VVT 14a, the injector 15, the spark plug 16, the swirl valve 17, the throttle valve 32, the electromagnetic clutch 34, the bypass valve 37, the EGR valve 453, the high pressure fuel pump 153, and the like. Therefore, a control signal is output to each of these devices based on the result of the above calculation and the like.

When a predetermined program is executed, the ECU 20 has an overall control unit 21, an injection control unit 22 (a control unit that controls the fuel injection valve), an ignition control unit 23, an intake control unit 24, an EGR control unit 25, and a fuel pressure control. The unit 26 (control unit that controls the fuel pressure adjusting mechanism), the deposit estimation unit 27 (deposit estimation unit), the fuel temperature derivation unit 28, and the storage unit 29 are functionally provided.

The overall control unit 21 comprehensively controls each of the control units 22 to 26, the deposit estimation unit 27, and the fuel temperature derivation unit 28 of the ECU 20 according to the operation scene of the engine and the like, and executes necessary calculations and controls.

The injection control unit 22 is a control module that controls the fuel injection operation by the injector 15. The ignition control unit 23 is a control module that controls the ignition operation by the spark plug 16. The intake control unit 24 is a control module that adjusts the flow rate and pressure of the intake air introduced into the combustion chamber 6, and controls the opening degrees of the throttle valve 32 and the bypass valve 37 and the ON / OFF of the electromagnetic clutch 34. The EGR control unit 25 is a control module that adjusts the amount of EGR gas introduced into the combustion chamber 6, and controls each operation of the intake VVT 13a and the exhaust VVT 14a and the opening degree of the EGR valve 453.

The fuel pressure control unit 26 adjusts the fuel pressure of the fuel supplied to the injector 15 by controlling the output of the high-pressure fuel pump 153. The fuel pressure control unit 26 sets the fuel pressure with reference to a basic fuel pressure map (FIGS. 6 and 7) predetermined according to the operating state (engine load and engine speed) of the engine and the combustion mode. Further, when the deposit deposit amount of the injector 15 in the injection hole 15B becomes equal to or more than a predetermined value, the fuel pressure control unit 26 refers to the deposit removal map (FIG. 8) to execute the cleaning mode for removing the deposit. To set. In the cleaning mode, the high pressure fuel pump 153 is controlled to increase the fuel pressure in a specific operating region. Due to the increase in fuel pressure, the deposit accumulated on the inner surface or the vicinity of the injection hole 15B is peeled off or scraped by the injection fuel.

The deposit estimation unit 27 performs a process of estimating the amount of deposit accumulated in the injection hole 15B based on the operating state of the engine. The deposit estimation unit 27 obtains the unit deposit amount, which is the deposit deposit amount per unit time (for example, 100 ms), according to the operating state, and integrates the unit deposit amount to obtain the deposit deposit amount. The fuel pressure control unit 26 executes the cleaning mode when the deposit accumulation amount estimated by the deposit estimation unit 27 becomes a predetermined value or more.

The amount of deposit deposited is basically determined by the operating time of the engine. However, the unit deposition amount varies depending on the fuel injection timing, fuel pressure, injection amount, and the like of the injector 15. For example, when the fuel injection timing is set at a position near the top dead center of the piston 5, the injected fuel rebounds from the cavity 51. The fuel spray due to this bounce adheres to the vicinity of the injection hole 15B, which causes deposit accumulation. On the contrary, when the fuel injection timing is set at a position near the bottom dead center of the piston 5, the rebound of the fuel does not substantially occur. Therefore, the unit accumulation amount is corrected so as to remove the rebound adhesion. It is appropriate to derive it.

Further, in the operating region where the fuel pressure is set high in the engine body 1, the fuel is injected from the injection hole 15B at a high pressure, so that deposit accumulation is less likely to occur. On the other hand, when the high fuel pressure is set, the deposit deposited in the injection hole 15B is naturally removed, and rather the unit deposit amount can be corrected so as to deduct the amount of restoration to the original state (the amount of deposit removed). It is reasonable. Further, in the operating region where a large amount of fuel injection is set in the engine body 1, a large amount of fuel is injected from the injection hole 15B, so that deposit accumulation is less likely to occur. On the contrary, the deposit tends to be easily accumulated during the operation period in which the fuel injection amount is set to be small. Therefore, it is appropriate to offset-correct the unit deposit amount so as to adjust the deposit deposit amount according to the fuel injection amount. In consideration of the above, it is desirable that the deposit estimation unit 27 corrects each of the unit deposit amounts according to the fuel injection timing, fuel pressure, injection amount, and the like of the injector 15 and then integrates them.

The fuel temperature derivation unit 28 performs a process of obtaining the temperature of the fuel supplied to the combustion chamber 6. Specifically, the fuel temperature derivation unit 28 performs a process of estimating the fuel temperature from the intake air temperature detected by the second intake air temperature sensor SN7 and the engine water temperature detected by the water temperature sensor SN2. In addition, for example, a thermometer may be installed on the fuel rail 154 to measure the fuel temperature, and the measured value may be input to the fuel temperature derivation unit 28. When the fuel temperature is higher than the predetermined value, the increase in fuel pressure due to the cleaning mode is avoided. This is to prevent the fuel from becoming hotter and causing problems such as bubbles being generated in the fuel when the fuel pressure is raised while the fuel is hot.

The storage unit 29 stores various programs, set values, parameters, and the like for controlling the engine. In addition, the storage unit 29 stores the operation map shown in FIG. 5, the basic fuel pressure map shown in FIGS. 6 and 7, the deposit removal map shown in FIG. 8, and the like.

[Driving map]
5 (A) to 5 (C) are operation maps in which the operating areas of the engine are divided according to the difference in combustion form. FIGS. 5A to 5C show differences in combustion control according to the degree of progress of engine warm-up and the engine speed / load. In the present embodiment, the first operation map Q1 (FIG. 5 (A)) used when the engine warm-up is completed and the second operation map used when the engine warm-up has progressed halfway. Q2 (FIG. 5 (B)) and a third operation map Q3 (FIG. 5 (C)) used when the engine is not warmed up are prepared. The first operation map Q1 during warm time includes the first, second, third, fourth, and fifth regions A1, A2, A3, A4, and A5 having different combustion forms, and during semi-warm-up. The second operation map Q2 of the above includes the sixth, seventh, eighth, and ninth regions B1, B2, B3, and B4 having different combustion forms. The third operation map Q3 in the cold state is composed of one of the tenth regions C1.

<At the time of warmth>
In the first operation map Q1, the first region A1 is a low / medium speed / low load region excluding a part of the high speed side from the low load region where the engine load is low (including no load). The second region A2 is a low / medium speed / medium load region having a higher load than the first region A1. The fourth region A4 is a low-speed / high-load region having a higher load and a lower rotation speed than the second region A2. The third region A3 is a medium speed / high load region having a higher rotation speed than the fourth region A4. The fifth region A5 is a high-speed region having a higher rotation speed than any of the first to fourth regions A1 to A4.

In the first region A1, partial compression ignition combustion (hereinafter, this is referred to as SPCCI combustion), which is a combination of SI combustion and CI combustion, is executed. SI combustion is a combustion mode in which the air-fuel mixture is ignited by sparks generated from the spark plug 16 and the air-fuel mixture is forcibly burned by flame propagation that expands the combustion region from the ignition point to the surroundings. .. CI combustion is a combustion form in which the air-fuel mixture is burned by self-ignition in an environment where the temperature and pressure are increased by the compression of the piston 5. SPCCI combustion, which is a combination of these SI combustion and CI combustion, involves SI combustion of a part of the air-fuel mixture in the combustion chamber 6 by spark ignition performed in an environment just before the air-fuel mixture self-ignites, and the SI combustion is performed. It is a combustion mode in which the other air-fuel mixture in the combustion chamber 6 is CI-combusted by self-ignition later (due to further increase in temperature and pressure accompanying SI combustion). "SPCCI" is an abbreviation for "Spark Controlled Compression Ignition".

SPCCI combustion has the property that the heat generation during CI combustion is steeper than the heat generation during SI combustion. In the waveform of the heat generation rate due to SPCCI combustion, the slope of the rise at the initial stage of combustion corresponding to SI combustion becomes smaller than the slope of the rise that occurs corresponding to the subsequent CI combustion. When the temperature and pressure in the combustion chamber 6 increase due to SI combustion, the unburned air-fuel mixture self-ignites and CI combustion is started. After the start of CI combustion, SI combustion and CI combustion are performed in parallel. Since the combustion rate of the air-fuel mixture is faster in CI combustion than in SI combustion, the heat generation rate is relatively large. However, since CI combustion is performed after the compression top dead center, the slope of the heat generation rate waveform does not become excessive. That is, when the compression top dead center is passed, the motoring pressure decreases due to the lowering of the piston 5, and as a result of suppressing the increase in the heat generation rate, it is possible to prevent the heat generation rate during CI combustion from becoming excessive. To. In this way, in SPCCI combustion, CI combustion is performed after SI combustion, so that the heat generation rate, which is an index of combustion noise, is unlikely to become excessive, and simple CI combustion (when all fuels are CI burned). ), Combustion noise can be suppressed.

With the end of CI combustion, SPCCI combustion also ends. Since CI combustion has a faster combustion rate than SI combustion, the combustion end time can be earlier than that of simple SI combustion (when all fuels are SI-combusted). Therefore, in SPCCI combustion, the combustion end time can be brought closer to the compression top dead center within the expansion stroke. As a result, in SPCCI combustion, fuel efficiency can be improved as compared with simple SI combustion.

In the first region A1, the above SPCCI combustion is performed in a lean environment (SPCCI_λ> 1). That is, the opening degree of the throttle valve 32 is set to the opening degree at which more air than the amount of air equivalent to the stoichiometric air-fuel ratio is introduced into the combustion chamber 6 through the intake passage 30. Specifically, the ECU 20 has an air-fuel ratio (A / F), which is a weight ratio of air (fresh air) introduced into the combustion chamber 6 through the intake passage 30 and fuel injected into the combustion chamber 6 by the injector 15. However, in a state where the air-fuel ratio is set to be larger than the stoichiometric air-fuel ratio (14.7), control is performed to burn the air-fuel mixture in the combustion chamber 6 with SPCCI.

In many regions of the first region A1, an internal EGR that leaves the burned gas in the combustion chamber 6 is performed. The ECU 20 controls the intake VVT 13a and the exhaust VVT 14a to drive the intake / exhaust valves 11 and 12 so as to form a valve overlap in which both the intake / exhaust valves 11 and 12 are opened with the exhaust top dead center in between. Then, the exhaust valve 12 is opened until the exhaust top dead center is passed (until the initial stage of the intake stroke). As a result, the burnt gas is pulled back from the exhaust port 10 to the combustion chamber 6, and the internal EGR is realized. The period of valve overlap is set to achieve an in-cylinder temperature suitable for obtaining the desired SPCCI combustion waveform.

In the second region A2, control for SPCCI combustion of the air-fuel mixture is executed in an environment where the air-fuel ratio in the combustion chamber 6 substantially matches the stoichiometric air-fuel ratio (SPCCI_λ = 1). The opening degree of the throttle valve 32 is set so that an amount of air corresponding to the stoichiometric air-fuel ratio is introduced into the combustion chamber 6 through the intake passage 30. In the second region A2, the EGR valve 453 is opened and the external EGR gas is introduced into the combustion chamber 6. Therefore, in the second region A2, the gas air-fuel ratio (G / F), which is the weight ratio of the total gas in the combustion chamber 6 to the fuel, is larger than the theoretical air-fuel ratio (14.7). Therefore, during operation in the second region A2, control is performed to burn the air-fuel mixture with SPCCI while forming a G / F lean environment in which the G / F is larger than the stoichiometric air-fuel ratio and the A / F substantially matches the stoichiometric air-fuel ratio. Is executed. The opening degree of the EGR valve 453 is set to an opening degree at which the stoichiometric air-fuel ratio is realized on an A / F basis.

In the third region A3, control for SPCCI combustion of the air-fuel mixture is executed in an environment where the A / F in the combustion chamber 6 is slightly richer than the stoichiometric air-fuel ratio (SPCCI_λ ≦ 1). A rich environment is set because a suitable amount of fuel injection is required to handle medium speed and high load. On the other hand, in the fourth region A4, which is a high-load but low-speed operation region, control is executed in which the air-fuel mixture is SPCCI-combusted in an environment where the A / F substantially matches the stoichiometric air-fuel ratio (SPCCI_λ = 1). In the fifth region A5, relatively orthodox SI combustion is performed. A / F is set to the stoichiometric air-fuel ratio or a value slightly richer than this (SI_λ ≦ 1). In these regions A3 to A5, the A / F can also be adjusted by the opening degree of the EGR valve 453.

<Semi-warm up>
In the second operation map Q2 at the time of semi-warm-up, the sixth region B1 corresponds to the region in which the first and second regions A1 and A2 in the first operation map Q1 are merged. The seventh region B2, the eighth region B3, and the ninth region B4 correspond to the third region A3, the fourth region A4, and the fifth region A5 of the first operation map Q1, respectively.

In the sixth region B1, as in the second region A2 of the first operation map Q1, control is executed in which the air-fuel mixture is SPCCI burned in an environment where the A / F in the combustion chamber 6 substantially matches the stoichiometric air-fuel ratio. (SPCCI_λ = 1). In at least a part of the sixth region B1, an internal EGR is performed in which a valve overlap period is set to leave the burned gas in the combustion chamber 6. The supercharger 33 is turned on in the relatively high load region of the sixth region B1 and the region on the relatively high speed side, and is turned off in the other regions.

The seventh region B2, the eighth region B3, and the ninth region B4 are controlled in the same manner as the third region A3, the fourth region A4, and the fifth region A5 of the first operation map Q1, respectively. That is, in the seventh region B2, the air-fuel mixture is SPCCI-combusted in an environment where the A / F in the combustion chamber 6 is slightly richer than the stoichiometric air-fuel ratio (SPCCI_λ ≦ 1). In the eighth region B3, the air-fuel mixture is SPCCI-combusted in an environment where the A / F substantially matches the stoichiometric air-fuel ratio (SPCCI_λ = 1). In the ninth region B4, orthodox SI combustion is executed, and the A / F is set to the stoichiometric air-fuel ratio or a value slightly richer than this (SI_λ ≦ 1).

<Cold>
The cold third operation map Q3 comprises only the tenth region C1. In the tenth region C1, the control of SI combustion while mainly mixing the fuel injected during the intake stroke with air is executed. The control in the tenth region C1 is the same as the combustion control of a general gasoline engine.

In addition, in FIGS. 5A and 5B, specific areas A11 and B11, which are areas where the deposit estimation unit 27 corrects the unit deposit amount according to the fuel injection timing (position of the piston 5), are shown. It is shown. In the first region A1 where SPCCI_λ> 1 combustion is performed, intake three-part injection is adopted in which the required fuel is divided into three times in the intake stroke and injected. However, when the required torque is less than a predetermined threshold value, the third injection is a compression stroke and the piston is executed at a timing close to top dead center. That is, the deposit is relatively easy to accumulate. Such a pattern change is executed in the specific area A11 which is a low load / low rotation area in the first area A1. Further, in the sixth region B1 where SPCCI_λ = 1 combustion is performed, a pattern in which the required fuel is collectively injected in the intake stroke is a basic pattern, while in a predetermined low load region, a part of the fuel is in the compression stroke. The piston is executed at a timing close to top dead center. That is, the deposit is relatively easy to accumulate. Such a pattern change is executed in the specific area B11 which is a low load / low rotation area in the sixth area B1. Therefore, the deposit estimation unit 27 corrects the specific regions A11 and B11 so that the unit deposit amount of the deposit is relatively large as compared with the other operating regions.

[Specific example of fuel pressure map]
As described above, the fuel pressure control unit 26 sets the fuel pressure of the fuel supplied to the injector 15 according to the operating state. When setting the fuel pressure, the fuel pressure control unit 26 accesses the storage unit 29 and refers to a fuel pressure map in which the fuel pressure set values are predetermined in association with the engine load (fuel injection amount) and the engine speed. Then, the fuel pressure control unit 26 reads out the fuel pressure value corresponding to the current engine load and the engine speed from the fuel pressure map, controls the high pressure fuel pump 153, and sets a predetermined fuel pressure.

FIG. 6 is an example of a basic fuel pressure map used when setting the fuel pressure of the injector 15 in SI combustion and SPCCI_λ = 1 combustion. The vertical axis of FIG. 6 is the engine load, the horizontal axis is the engine speed (rpm), and the unit of fuel pressure is MPa. Roughly speaking, in the low to medium load region, the fuel pressure is set low (40 MPa) in the low engine speed region and high (60 MPa) in the high engine speed region. On the other hand, in the medium load to high load region, the fuel pressure is relatively suppressed (30 MPa in the low rpm range and 40 MPa in the high rpm range). This is to avoid deterioration of fuel efficiency due to an increase in the mechanical load of the high-pressure fuel pump 153. As described above, the high-pressure fuel pump 153 is driven by the camshaft that drives the exhaust valve 12, which causes an auxiliary machine loss of the engine body 1. Therefore, in the medium load to high load region, the fuel pressure is set low to suppress the loss of auxiliary equipment.

FIG. 7 is an example of a basic fuel pressure map used when setting the fuel pressure of the injector 15 in SPCCI_λ> 1 combustion. The vertical axis of FIG. 7 is the fuel injection amount (mg) corresponding to the engine load, the horizontal axis is the engine speed (rpm), and the unit of fuel pressure is MPa. In this SPCCI_λ> 1 combustion, the fuel pressure is set to 40 MPa regardless of the engine load and the engine speed. This is because in lean combustion, the fuel injection amount is small, and as described above, the required fuel is injected in three parts, so that it is not necessary to bother to increase the fuel pressure by increasing the auxiliary equipment loss.

FIG. 8 is an example of a fuel pressure map for removing deposits used when the cleaning mode of the injector 15 is executed in SI combustion and SPCCI_λ = 1 combustion. As described above, when the deposit accumulation amount of the injector 15 in the injection hole 15B becomes equal to or more than a predetermined value, the fuel pressure control unit 26 executes a cleaning mode for removing the deposit. In the cleaning mode, the fuel pressure is increased and the deposit accumulated in the vicinity of the injection hole 15B is peeled off by the discharge pressure from the fuel injection hole 15B. When executing this cleaning mode, the fuel pressure control unit 26 switches from the basic fuel pressure map shown in FIG. 6 to the deposit removing fuel pressure map shown in FIG. 8 to set the fuel pressure of the injector 15.

In the deposit removing fuel pressure map of FIG. 8, in the low load to medium load region (0.125 to 0.35 / 0.45) and the operating region where the engine speed is low (500 to 3000 rpm), The fuel pressure, which was 40 MPa in the basic fuel pressure map, is set to 60 MPa. That is, in the operating region, the fuel pressure is increased when the cleaning mode is executed. The increase in fuel pressure removes the deposit near the injection hole 15B.

[Case where the increase in fuel pressure is restricted]
As described above, when the deposit deposit amount in the injection hole 15B becomes a predetermined value or more, the fuel pressure control unit 26 applies the deposit removal fuel pressure map to increase the fuel pressure and executes the cleaning mode. However, under certain conditions, the increase in fuel pressure is limited. The mode of limiting the increase in fuel pressure is roughly divided into
(A) Limit the cleaning mode itself to which the deposit removal fuel pressure map is applied,
(B) Apply the fuel pressure map for removing deposits, but set the area on the map to limit the increase in fuel pressure.
There are two cases. In the present embodiment, as a specific example of the above case (A),
(A1) When lean combustion is performed
(A2) When the fuel temperature is high
Is illustrated. Further, as a specific example of the above case (B),
(B1) When the engine load is in the high load region
(B2) When the engine speed is in the high speed range
Is illustrated.

The above-mentioned "limitation" of the fuel pressure increase includes "prohibition" of the fuel pressure increase completely and "suppression" of reducing the fuel pressure increase degree with respect to the normal fuel pressure increase degree in the cleaning mode. In cases (A1) and (A2), in the case of "prohibited", even if the deposit deposit amount is equal to or more than a predetermined value, the transition to the cleaning mode, that is, the application of the deposit removal fuel pressure map itself is prohibited. As an example of "suppression", apply a "suppression" deposit removal fuel pressure map in which the degree of increase in fuel pressure is set lower than that of the normal deposit removal fuel pressure map. The mode to be used can be mentioned. In the cases (B1) and (B2), as an example of "prohibition", an embodiment in which the fuel pressure is set to be exactly the same as the basic fuel pressure map for a predetermined operating area of the fuel pressure map for removing deposits can be mentioned. Further, as an example of "suppression", an embodiment in which the degree of increase in fuel pressure for the predetermined operating region is set to be smaller than the value of the normal fuel pressure map for removing deposits can be mentioned.

<A1; Restrictions on lean combustion>
The fuel pressure control unit 26 limits the increase in the fuel pressure when the air-fuel ratio of the air-fuel mixture generated in the combustion chamber is set to be leaner than the stoichiometric air-fuel ratio. In the present embodiment, in the first region A1 of FIG. 5A, SPCCI_λ> 1 combustion in which the air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio is executed. When this SPCCI_λ> 1 combustion is executed, the fuel pressure control unit 26 prohibits or suppresses the increase in fuel pressure due to the cleaning mode. This is because in a situation where a lean air-fuel mixture is generated and combustion is performed such as SPCCI_λ> 1 combustion, if the fuel pressure of the injector 15 is increased, the linearity of the fuel injection amount from the injector 15 tends to be unable to be secured. Because. This point will be described with reference to FIG.

The fuel pressure control unit 26 gives the injector 15 a control pulse having a pulse width corresponding to the valve opening period of the injection hole 15B to execute the injection operation. The injector 15 is driven by applying a pulse-controlled current to the internal coil that operates the valve body that opens and closes the injection hole 15B. The fuel injection amount from the injection hole 15B is adjusted by the pulse width of the control pulse (the period during which the injection hole 15B is opened).

9 (A) and 9 (B) are time charts showing examples of pulse widths W1 and W2 of the control pulse of the injector 15. FIG. 9A shows a control pulse having a small duty ratio, that is, a control pulse having a pulse width W1 relatively short corresponding to the high period “H” of the pulse with respect to the pulse period T. When a control pulse having such a small pulse width W1 is given to the injector 15, the valve opening period of the injection hole 15B is shortened, so that the fuel injection amount is reduced. On the other hand, FIG. 9B shows a control pulse having a large duty ratio, that is, a control pulse having a pulse width W2 relatively long with respect to the pulse period T. In the case of such a control pulse having a large pulse width W2, the valve opening period of the injection hole 15B becomes long, so that the fuel injection amount also increases.

FIG. 9C is a graph showing an example of the relationship between the pulse width of the control pulse of the injector 15 and the fuel injection amount. As a characteristic of the general-purpose injector 15, the linearity of the fuel injection amount decreases in the region where the pulse width of the control pulse becomes too small. That is, the valve opening period of the injection hole 15B and the injection amount tend not to be proportional. In the graph of FIG. 9C, in the region where the pulse width is 700 μs or more, the fuel injection amount increases linearly with the increase in the pulse width, and the linearity between the two is high. However, in the region where the pulse width is less than 700 μs, the fuel injection amount does not increase linearly with the increase in the pulse width, and the graph has fluctuations. Roughly speaking, it can be said that a region having a pulse width of less than 700 μs is a region having a small pulse width W1 shown in FIG. 9 (A), and a region having a pulse width of 700 μs or more is a region having a large pulse width W2 shown in FIG. 9 (B).

In the case of lean combustion, the fuel injection amount from the injector 15 is relatively small, so the pulse width is set to a relatively small value. If the fuel pressure is increased in this situation, the injection amount per unit time increases. Therefore, it is necessary to make the originally small pulse width smaller and shorten the valve opening period of the injection hole 15B. .. As shown in FIG. 9C, in the region where the pulse width is too small, the linearity of the fuel injection amount is lowered, and the valve opening period of the injection hole 15B and the injection amount tend to be out of proportion. When the linearity is lowered, the intended air-fuel mixture distribution cannot be formed in the combustion chamber 6, resulting in a problem that the combustion stability is deteriorated.

In particular, in the present embodiment, the intake three-split injection is adopted in the first region A1 to which SPCCI_λ> 1 combustion is applied. That is, since the amount of fuel required to achieve the target torque is injected in three times, the pulse width for each time is originally small. Therefore, if the fuel pressure is increased in SPCCI_λ> 1 combustion, the combustion stability tends to deteriorate. In view of this point, it is desirable to set the cleaning mode to be prohibited when SPCCI_λ> 1 combustion is executed, or at least to suppress the increase in fuel pressure. In view of the above, in the present embodiment, a fuel pressure map for removing deposits for SPCCI_λ> 1 combustion is not prepared. By prohibiting the cleaning mode when SPCCI_λ> 1 combustion is executed, disturbance of the air-fuel mixture distribution in the cylinder can be suppressed, and combustion stability can be ensured.

<A2; Limitation when fuel temperature is high>
The fuel pressure control unit 26 limits the increase in fuel pressure when the fuel temperature derived by the fuel temperature extraction unit 28 is higher than a preset reference temperature. If the temperature of the fuel supplied from the fuel supply system 150 rises too much due to the temperature of the engine body 1 becoming too high, bubbles may be generated from the fuel. When the air bubbles enter the injector 15, it may not be possible to inject the amount of fuel corresponding to the fuel pressure and the valve opening period of the injection hole 15B (hereinafter, this is referred to as "fuel failure"). As a matter of course, when a fuel failure occurs, combustion stability cannot be ensured.

As the fuel pressure is increased by the high-pressure fuel pump 153, the fuel temperature tends to increase. If the fuel pressure is increased to execute the cleaning mode while the fuel temperature has already risen, the fuel temperature will be further increased, which may accelerate the occurrence of fuel failure. Therefore, when the fuel temperature is higher than a predetermined threshold value and the possibility of fuel failure is increased when the fuel pressure is further increased, the fuel pressure control unit 26 increases the deposit deposit amount to a predetermined value or more. Prohibits or suppresses the execution of cleaning mode even if it is deposited on the floor. As a result, fuel failure can be suppressed and combustion stability can be ensured.

<B1; Limitation in high load area>
When the fuel pressure control unit 26 divides the load region of the engine into a high load region having a relatively high load and a low load region having a relatively low load, the fuel pressure rises in the high load region. To limit. Since the high-pressure fuel pump 153 operates by applying a mechanical driving force from the engine body 1, an increase in fuel pressure increases the mechanical load (auxiliary machine loss) of the engine body 1. Generally, when the engine load is high, the fuel pressure of the injector 15 is set high in order to increase the fuel injection amount per unit time. In such a high load, if the fuel pressure is further increased to execute the cleaning mode, the mechanical load of the high-pressure fuel pump 153 is further increased, and as a result, the fuel efficiency performance is deteriorated.

Further, in a high load region where the fuel pressure is originally set high and / or the fuel injection amount is set large, a cleaning effect of the deposit adhering to the injection hole 15B can be expected. That is, it can be said that the fuel pressure is high in the high load region, the fuel injection amount per unit time is large, and the cleaning operation for removing the deposit is naturally executed. Therefore, the fuel pressure control unit 26 limits the fuel pressure increase for cleaning the deposit in at least a part of the high load region (a predetermined range of the basic fuel pressure map). This makes it possible to prevent the mechanical drive resistance of the high-pressure fuel pump 153 from being unnecessarily increased.

In the deposit removing fuel pressure map shown in FIG. 8, the fuel pressure for removing the deposit is predetermined according to the engine load. In this deposit removing fuel pressure map, the fuel pressure is set higher than the basic fuel pressure map for SI combustion and SPCCI_λ = 1 combustion shown in FIG. 6 for the low load region, and the same as the basic fuel pressure map for the high load region. Set to fuel pressure. That is, in the region where the engine load is high (0.4 / 0.8 to 1.4) in the fuel pressure map for removing deposits, the fuel pressure is set to the same fuel pressure as the basic fuel pressure map. Specifically, in the operating region where the engine speed is low (500 to 2750 rpm) in the high load region, the fuel pressure is maintained at 30 MPa as in the basic fuel pressure map, and the engine speed is high (3000 to 6500 rpm). ), The fuel pressure is maintained at 40 MPa. As described above, the fuel pressure is increased with respect to the basic fuel pressure map in a part of the low load to medium load region (0.125 to 0.35 / 0.45).

Further, in the basic fuel pressure map of FIG. 6, the fuel pressure to be set is predetermined according to the engine load. Focus on a predetermined range of this basic fuel pressure map, specifically, a region where the engine load is 0.125 to 0.55 / 0.7 and the engine speed is 1000 to 3000 rpm. In the predetermined region, the fuel pressure (60 MPa) in the relatively high load region is set higher than the fuel pressure (40 MPa) in the relatively low load region. Then, in the deposit removing fuel pressure map of FIG. 8, the fuel pressure is maintained at 60 MPa in the relatively high load region. This is because, in the first place, in the operating region, a high fuel pressure of 60 MPa, which can remove the deposit, is already set in the basic fuel pressure map, and it is not necessary to increase the fuel pressure to increase the auxiliary equipment loss any more. .. Therefore, the fuel pressure control unit 26 prohibits the increase in fuel pressure when the engine load when the deposit deposit amount exceeds a predetermined value is in the high load region.

<B2; Limitation in high rpm region>
When the fuel pressure control unit 26 divides the load region of the engine into a high rotation speed region having a relatively high rotation speed and a low rotation speed region having a relatively low rotation speed, if it is the high rotation speed region, the fuel pressure Limit the rise of. Generally, when the engine speed is high, the total time during which the injection hole 15B is open becomes long, and the fuel injection amount per unit time increases as compared with the case where the engine speed is low. Therefore, it can be said that the deposit of the injection hole 15B can be removed by discharging a large amount of fuel without increasing the fuel pressure, and the cleaning operation is naturally executed. Nevertheless, increasing the fuel pressure to execute the cleaning mode at such a high speed leads to unnecessarily increasing the mechanical load of the high pressure fuel pump 153, resulting in deterioration of fuel efficiency. .. Therefore, the fuel pressure control unit 26 limits the increase in fuel pressure for cleaning the deposit in the high load region.

In the deposit removing fuel pressure map shown in FIG. 8, it can be said that the fuel pressure for removing the deposit is predetermined according to the engine speed. In this deposit removing fuel pressure map, the fuel pressure is set higher than the basic fuel pressure map for SI combustion and SPCCI_λ = 1 combustion shown in FIG. 6 for a part of the low rotation region (low load region), and the high load The area is set to the same fuel pressure as the basic fuel pressure map. That is, in the high rotation region (3250 to 6500 rpm) in the fuel pressure map for removing deposits, the fuel pressure is set to the same fuel pressure as the basic fuel pressure map. Specifically, in the operating region (0.125 to 0.7) in which the engine load is relatively low in the high rotation region, the fuel pressure is maintained at 60 MPa as in the basic fuel pressure map, and the engine load is relatively low. Even in the high operating range (0.8 to 1.4), the fuel pressure is maintained at 40 MPa. As described above, the fuel pressure is increased with respect to the basic fuel pressure map in a part of the low rotation region (500 to 3000).

Further, in the basic fuel pressure map of FIG. 6, it can be said that the set fuel pressure is predetermined according to the engine speed. Focus on a predetermined range of this basic fuel pressure map, specifically, a region where the engine load is 0.125 to 0.35 and the engine speed is 500 to 6500 rpm. In the predetermined region, the fuel pressure (60 MPa) in the high rotation region is set higher than the fuel pressure (40 MPa) in the low rotation region. Then, in the deposit removing fuel pressure map of FIG. 8, the fuel pressure is maintained at 60 MPa in the high rotation speed region. This is because, as described above, the deposit can be removed if the fuel pressure is as high as 60 MPa. Therefore, the fuel pressure control unit 26 prohibits the increase in fuel pressure when the engine speed is in the high speed region when the deposit deposit amount exceeds a predetermined value.

[Fuel pressure switching control flow]
FIG. 10 is a flowchart showing an example of fuel pressure switching control of the injector 15 by the ECU 20 (FIG. 4). The ECU 20 reads various signals from the sensors SN1 to SN11 shown in FIG. 4 and other sensors, and acquires information on the operating state of the engine body 1 (step S1). Based on the acquired information, it is specified which region of the operation maps Q1 to Q3 shown in FIGS. 5 (A) to 5 (C) the current operation point corresponds to.

Next, the deposit estimation unit 27 obtains the unit deposit amount in the current processing cycle according to the operating state, and performs the process of integrating the unit deposit amount to obtain the deposit deposit amount (step S2). The deposit estimation unit 27 corrects the unit accumulation amount of the deposit determined by the operating time and the operating state by using the coefficients determined by the fuel injection timing (the degree of rebound of the spray from the piston 5), the fuel pressure, and the injection amount. The unit deposit amount in the treatment cycle is obtained.

After that, the fuel pressure control unit 26 determines the current operating area (step S3). Here, for simplification, the operating region is the SI combustion region (10th region C1 in FIG. 5C), the SPCCI_λ = 1 combustion region (6th region B1 in FIG. 5B), or , SPCCI_λ> 1 combustion region (first region A1 in FIG. 5A) is determined. When the operating region is not the operating region where SI combustion or SPCCI_λ = 1 combustion is executed (NO in step S3), that is, when the operating region is the operating region where SPCCI_λ> 1 combustion is executed, the fuel pressure control unit 26 is shown in FIG. The fuel pressure of the injector 15 is set with reference to the basic fuel pressure map of SPCCI_λ> 1 combustion shown in (Step S4). That is, when executing SPCCI_λ> 1 combustion, as described above, the cleaning mode in which the fuel pressure is increased is prohibited in consideration of the problem that the linearity of the fuel injection amount decreases.

On the other hand, when the operating region is the operating region where SI combustion or SPCCI_λ = 1 combustion is executed (YES in step S3), the fuel pressure control unit 26 has a predetermined deposit accumulation amount obtained by the deposit estimation unit 27 in step S2. It is determined whether or not the threshold value Th1 is exceeded (step S5). The threshold value Th1 is set to an appropriate value before reaching the deposit deposit amount that deteriorates the fuel injection characteristics from the injection hole 15B. When the deposit deposit amount does not exceed the threshold Th1 (NO in step S5), the fuel pressure control unit 26 does not execute the cleaning mode and refers to the basic fuel pressure map of SI combustion and SPCCI_λ = 1 combustion shown in FIG. Then, the fuel pressure of the injector 15 is set (step S7).

When the deposit deposit amount exceeds the threshold Th1 (YES in step S5), the fuel pressure control unit 26 receives the detection value of the second intake air temperature sensor SN7 and the water temperature sensor SN2 by the fuel temperature derivation unit 28 in the current processing cycle. Refer to the fuel temperature obtained from the detected value of (step S6). When the fuel temperature is equal to or higher than the predetermined threshold Th2 (NO in step S6), that is, when the fuel temperature is considerably high, the fuel pressure control unit 26 does not execute the cleaning mode, and SI combustion and SPCCI_λ = 1 combustion. The fuel pressure of the injector 15 is set with reference to the basic fuel pressure map (step S7). This is because even if the deposit deposit amount exceeds the threshold value Th1, if the fuel pressure is increased while the fuel is hot, the fuel becomes even hotter and the fuel failure occurs. Because it can be done.

On the other hand, when the fuel temperature is less than the threshold value Th2 (YES in step S6), the fuel pressure control unit 26 executes the cleaning mode. That is, the fuel pressure map to be referred to is switched from the basic fuel pressure map to the deposit removing fuel pressure map shown in FIG. 8 (step S8). As a result, when the fuel pressure belongs to a predetermined operating region (low load to medium load region), the fuel pressure is higher than the basic fuel pressure map, and the deposit near the injection hole 15B is removed.

[Modification example]
Although the embodiments of the present invention have been described above, the present invention is not limited to this, and various modified embodiments can be taken.

(1) In the above embodiment, in the deposit removing fuel pressure map of FIG. 8, an embodiment in which the fuel pressure is not increased in a high load operating region is illustrated. This is an example, and if it is a relatively low rotation speed region, the fuel pressure may be increased when the cleaning mode is executed even in a high load operation region.

(2) In the above embodiment, an example is shown in which the cleaning mode is not executed when SPCCI_λ> 1 combustion is executed. Instead of this, the lean combustion is corrected to the fuel rich side, for example, the combustion mode is temporarily changed from SPCCI_λ> 1 combustion to SPCCI_λ = 1 combustion, and then the cleaning mode for increasing the fuel pressure is executed. Is also good.

(3) In the above embodiment, an example in which the cleaning mode is not executed when the fuel temperature is equal to or higher than the threshold value Th2 is shown (step S6 in FIG. 10). If the vehicle is equipped with means (cooling device, etc.) to eliminate the increase in fuel temperature, that is, if the vehicle is equipped with measures to prevent the fuel temperature from increasing, omit the process of determining the fuel temperature. You can do it.

1 Engine body 5 Piston 50 Crown surface 51 Cavity 6 Combustion chamber 6U Combustion chamber ceiling surface 15 Injector (fuel injection valve)
15A Head part 15B Injection hole 153 High-pressure fuel pump (fuel pressure adjustment mechanism)
20 ECU (engine control device)
22 Injection control unit (control unit that controls the fuel injection valve)
26 Fuel pressure control unit (control unit that controls the fuel pressure adjustment mechanism)
27 Deposit estimation unit (deposit estimation unit)

Claims (7)

An engine control device provided with a fuel injection valve that is arranged in a combustion chamber partially partitioned by a piston having a cavity on the crown surface and injects fuel directly into the cavity.
A fuel pressure adjusting mechanism that adjusts the fuel pressure of the fuel supplied to the fuel injection valve,
A control unit that controls the fuel injection valve and the fuel pressure adjusting mechanism,
A deposit estimation unit that performs a process of estimating the amount of deposit accumulated in the injection hole of the fuel injection valve based on the operating state of the engine is provided.
The control unit
When the deposit deposit amount estimated by the deposit estimation unit becomes a predetermined value or more, the fuel pressure adjusting mechanism is controlled so as to increase the fuel pressure, while the deposit pressure adjusting mechanism is controlled.
When the rotation region of the engine is divided into at least a high rotation region having a relatively high rotation speed and a low rotation region having a relatively low rotation speed, in the case of the high rotation region, the increase in fuel pressure is increased. An engine controller characterized by limiting. In the engine control device according to claim 1,
It also has a storage unit that stores a basic fuel pressure map in which the set fuel pressure is set in advance according to the engine speed.
In the predetermined range of the basic fuel pressure map, the fuel pressure in the high rotation region is set higher than the fuel pressure in the low rotation region.
The control unit causes the fuel pressure adjusting mechanism to set the fuel pressure based on the basic fuel pressure map, and when the engine speed when the deposit deposit amount becomes a predetermined value or more is in the high rotation speed region. , An engine control device that limits the rise in fuel pressure. In the engine control device according to claim 1 or 2.
The control unit is an engine control device that prohibits an increase in fuel pressure when the engine speed is in the high speed region. In the engine control device according to claim 1 or 2.
The control unit is an engine control device that reduces the degree of increase in fuel pressure when the engine speed is in the high speed region. In the engine control device according to claim 2.
In addition to the basic fuel pressure map, the storage unit stores a deposit removal fuel pressure map in which the fuel pressure for removing the deposit accumulated in the injection hole is predetermined according to the engine speed.
In the deposit-removed fuel pressure map, the fuel pressure is set higher than that of the basic fuel pressure map in the low rotation region, and the fuel pressure is set to the same as that of the basic fuel pressure map in the high rotation region.
The control unit is an engine control device that applies the deposit removal fuel pressure map to cause the fuel pressure adjusting mechanism to set the fuel pressure when the deposit accumulation amount becomes a predetermined value or more. An engine body including a combustion chamber partially partitioned by a piston having a cavity on the crown surface, a fuel injection valve arranged in the combustion chamber and directly injecting fuel into the cavity, and the like.
The control device according to any one of claims 1 to 5 is provided.
An engine system in which a head portion of the fuel injection valve provided with the injection hole is arranged on the ceiling surface of the combustion chamber so as to face the cavity in the vicinity of the radial center of the combustion chamber. In the engine system according to claim 6,
It further comprises a fuel supply device including a tank for storing fuel and a pump for delivering fuel from the tank to the fuel injection valve.
The fuel pressure adjusting mechanism is the pump, and the pump operates by applying a mechanical driving force from the engine body.
The control unit is an engine system that adjusts the fuel pressure by controlling the output of the pump.

Images