JP4254651B2 - Diesel engine automatic stop / start control method and diesel engine automatic stop / start control system - Google Patents

Description

  The present invention relates to a technical field of a diesel engine automatic stop / start control method and system for restarting an engine from an idling stop state, for example.

  Recently, in order to reduce fuel consumption and exhaust gas when idling, from the viewpoint of environmental conservation or resource saving energy, when the vehicle stops, the internal combustion engine (hereinafter also referred to as “engine”) is automatically stopped. However, technological development has been actively conducted on an economy running system (hereinafter referred to as “eco-run”) that automatically restarts an engine when a start instruction is issued from a stopped state.

  For example, Patent Document 1 provides an automatic stop control device for an internal combustion engine that can secure an opportunity for automatic stop of the internal combustion engine and improve fuel efficiency. Patent Document 2 provides an engine control apparatus that can quickly perform fuel injection in the order of cylinders of compression cylinders at the time of starting. Patent Document 3 provides a control device for an internal combustion engine in which engine startability is improved by stopping the engine at a desired crank angle. According to Patent Document 4, an accumulator fuel injection device that performs a plurality of fuel injections by a single fuel pump is disclosed. In order to reduce variations in fuel pressure in an accumulator chamber to which fuel is pumped, The pumping timing and fuel injection timing are overlapped.

JP 2003-41967 A JP 2001-173473 A JP 2000-64890 A Japanese Patent No. 3446609

  In the gasoline engine, the eco-run system has been studied as described above, and the stop position is detected and controlled in order to improve the startability when the engine is started again from the idling stop state. The gasoline engine has a lower required fuel pressure than the diesel engine, and in the case of a four-cylinder gasoline engine, the combustion system is not one-pump two-injection, so the crank position of the first compression cylinder is accurately detected. However, the phase of the pump is not detected.

  However, in a common rail type diesel engine with one pressure and two injections, which requires a higher fuel pressure than a gasoline engine, depending on the phase of the fuel pump that pumps fuel to the common rail, fuel is injected from the common rail to the cylinder by pumping fuel. May be done first. When the rail pressure of the common rail is low, fuel injection into the cylinder may not be possible, and the diesel engine may not be started quickly.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a diesel engine automatic stop / start control method and a diesel engine automatic stop / start control system excellent in startability.

  The first automatic stop / start control method for a diesel engine according to the present invention solves the above problems.

An automatic stop / start control method for a diesel engine that controls automatic stop and start of a multi-cylinder diesel engine in which fuel is injected multiple times each time the fuel is pumped once. When a stop condition is satisfied, a determination step for determining a stop phase at which the diesel engine stops or stops before the diesel engine is restarted at the latest, and from the stop phase to an injection phase for injecting fuel A phase determination step for determining whether or not there is a pumping phase for pumping fuel between the pumping phase and the pumping phase between the stop phase and the injection phase when it is determined that the pumping phase does not exist The change step of changing the stop phase so that there is, and when the diesel engine is started again, the pumping phase was pumped And a injection step of injecting the injection phase the charge.

  According to the first automatic stop / start control method for a diesel engine according to the present invention, first, a diesel engine having a plurality of cylinders in which fuel is injected a plurality of times per one fuel pumping is automatically stopped. Here, the “automatic stop” according to the present invention means, for example, that the diesel engine mounted on the vehicle is temporarily stopped when the vehicle is temporarily stopped due to a signal or the like. That is, it means that the vehicle is brought into an idling stop state. The “automatic stop condition” according to the present invention is a condition that becomes a reference when shifting from the normal drive state to the idling stop state. For example, the vehicle is stopped, the brake is applied, and the engine speed is a predetermined value. One condition for shifting to the idling stop state is when the engine speed is lower than the engine speed.

  When the diesel engine is started again from the idling stop state, the stop phase is determined before the diesel engine is restarted at the latest. The “stop phase” according to the present invention is a stop position of a piston that reciprocates in a cylinder of a diesel engine, and more specifically means a crank angle when the piston stops. The stop phase of the diesel engine only needs to be determined before the diesel engine is restarted at the latest. For example, after the automatic stop condition is established, the stop phase may be determined by calculation, estimation, etc. before the diesel engine is automatically stopped, or the stop phase is detected and measured after the diesel engine is automatically stopped. Etc. may be determined.

  According to the first automatic stop / start control method for a diesel engine according to the present invention, it is determined whether there is a pumping phase for pumping the fuel between the stop phase and an injection phase for injecting the fuel. To do. For example, after a fuel is pumped once to a common rail, the diesel engine burns the fuel injected into each cylinder in a plurality of times from the common rail. The “injection phase” according to the present invention means the fuel injection timing on the crank angle, and when there is no pumping phase between the stop phase and the injection phase, the first time when the diesel engine is restarted It becomes difficult to inject fuel in the injection phase. More specifically, the rail pressure in the common rail has dropped, and after restarting the diesel engine, it becomes difficult to inject fuel with sufficient injection pressure in the injection phase that comes first. There may be a problem with startability.

  Therefore, according to the first automatic stop / start control method for a diesel engine according to the present invention, for example, only a crankshaft is provided to a minimum necessary so that the pumping phase exists between the stop phase and the injection phase. The stop phase is changed by rotating. By changing the stop phase, first, after the diesel engine is restarted, the pumping phase arrives and the fuel is pumped. Next, when the injection phase arrives and fuel is injected into the cylinder at a sufficient injection pressure, a sufficient amount of fuel can be burned immediately after the diesel engine is restarted. As a result, the diesel engine can be started quickly, and the startability of the diesel engine can be improved.

  In one aspect of the first automatic stop / start control method for a diesel engine according to the present invention, the changing step includes a constantly meshing gear mechanism that transmits a rotational force to a crankshaft to change the stop phase. A driving time calculating step of calculating a driving time to be driven; and a driving step of further driving the constantly meshing gear mechanism for the driving time.

  According to this aspect, the rotational force is transmitted to the crankshaft so that the pumping phase exists between the stop phase and the injection phase, and the stop phase of the diesel engine is controlled. That is, the stop phase is controlled so that there is a pumping phase between the stop phase and the injection phase that comes first after the diesel engine is restarted. More specifically, in order to keep the cylinder in which the injection phase first arrives after restarting the diesel engine just before the compression stroke, the crankshaft is rotated by a required angle, and the piston stop position of the cylinder is set. change. The constant meshing gear mechanism, for example, transmits the rotational force generated by the starting motor to the crankshaft, and changes the stop position of the piston by rotating the crankshaft shaft by a required angle. The driving time during which the constant meshing gear mechanism is driven corresponds to the angle for driving the crankshaft, and the constant meshing gear mechanism is further driven for the driving time calculated to change the stop position. According to the constant meshing gear mechanism, the gear that transmits the rotational force from the starting motor to the crankshaft is always meshed, and the crank rotates so that the engine stops at the target stop position even when the engine is not stopped. Can transmit power. Therefore, the rotational force can be smoothly transmitted to the crankshaft even in a relatively low rotation region immediately before the engine stops. Therefore, it is possible to smoothly change the stop phase both before and after the automatic stop of the engine.

  The operation for changing the stop phase by rotating the crankshaft may be performed immediately before the engine is stopped, may be performed while the engine is stopped, or the engine is restarted. It may be performed immediately before.

  In order to solve the above problems, a second diesel engine automatic stop / start control method according to the present invention automatically stops and starts a multi-cylinder diesel engine in which fuel is injected a plurality of times each time the fuel is pumped once. A diesel engine automatic stop / start control method for controlling the diesel engine, wherein when the diesel engine automatic stop condition is satisfied for a plurality of cylinders of the diesel engine, the diesel engine is restarted at the latest A determination step of determining a stop phase at which the diesel engine is stopped or stopped, and one cylinder from which the injection phase for injecting fuel first arrives among the plurality of cylinders from the stop phase to the one cylinder A phase determination step for determining whether or not there is a pumping phase for pumping the fuel before the injection phase of When the diesel engine is restarted, the one cylinder determined not to have the pumping phase does not inject into the injection phase, and the other cylinder in which the injection phase comes next to the one cylinder does not perform the pumping. An injection step of injecting the fuel pumped to the phase into the injection phase of the other cylinder.

  According to the second automatic stop / start control method for a diesel engine according to the present invention, first, the diesel engine having a plurality of cylinders in which fuel is injected a plurality of times per one fuel pressure feed is automatically stopped. The stop phase of the diesel engine only needs to be determined before the diesel engine is restarted at the latest. For example, after the automatic stop condition is satisfied, the stop phase may be determined before the diesel engine is automatically stopped, or the stop phase may be determined after the diesel engine is automatically stopped.

  According to the second automatic stop / start control method for a diesel engine according to the present invention, for one cylinder in which the injection phase for injecting fuel first arrives among the plurality of cylinders, the one cylinder from the stop phase It is determined whether or not there is a pumping phase for pumping fuel before the injection phase. Subsequently, when the diesel engine is started again, one cylinder determined to have no pumping phase is not injected into the injection phase, and another injection phase arrives next to the one cylinder. The fuel pumped into the pumping phase for the cylinder is injected into the injection phase of the other cylinder. That is, fuel is not injected into one cylinder that does not have a pumping phase between the stop phase and the injection phase of the diesel engine, and other cylinders that have a pumping phase between the stop phase and the injection phase of the diesel engine. Is injected with fuel.

  Here, a diesel engine having four cylinders (# 1 to # 4), in which fuel injection is performed by a one-pressure-feed-two-injection system in which fuel is injected into the two cylinders once every time the fuel is pumped once. The present invention will be described by taking as an example. In such a diesel engine, fuel is normally injected into four cylinders (# 1 to # 4) in the order of # 1, # 3, # 4, and # 2. For example, the stop phase is before # 1. If there is no pumping phase between the stop phase and the injection phase for injecting fuel into # 1, the next to # 1 is not injected into the # 1 cylinder when the diesel engine is started. Fuel injection is started from # 3 when the injection phase arrives. There is a pumping phase between the injection phase in which fuel is injected into # 1 and the injection phase in which fuel is injected into # 3, and fuel is supplied from the cylinder of # 3 where the injection phase first arrives after the pumping phase. Inject. That is, one cylinder corresponds to the # 1 cylinder and the other cylinder corresponds to the # 3 cylinder. Therefore, by injecting fuel from the # 3 cylinder instead of # 1, it is possible to inject the fuel to the # 3 cylinder at a sufficient injection pressure. Therefore, the diesel engine can be started quickly, and the startability of the diesel engine can be improved.

  In an aspect of the second diesel engine automatic stop / start control method according to the present invention, prior to the phase determination step, the injection pressure for injecting the fuel is equal to or higher than a predetermined pressure. A pressure determination step for determining whether the injection pressure is not equal to or higher than the predetermined pressure, the phase determination step is executed, and it is determined that the injection pressure is equal to or higher than the predetermined pressure. In this case, the phase determination step is not executed, and the fuel is injected into all the injection phases of the plurality of cylinders in the injection step.

  According to this aspect, first, in the pressure determination step, it is determined whether or not the injection pressure is equal to or higher than the predetermined pressure in the injection phase in which the fuel is injected into one cylinder. When the injection pressure is not equal to or higher than the predetermined pressure, the diesel engine is started by injecting fuel into another cylinder without injecting fuel into one cylinder. When the injection pressure is equal to or higher than the predetermined pressure, after the stop phase, fuel is injected from one cylinder where the injection phase first arrives. That is, in this embodiment, when the injection pressure is equal to or higher than the predetermined pressure, the diesel engine is started by directly injecting fuel into one cylinder, and the injection pressure is not higher than the predetermined pressure. In addition, starting of the diesel engine is started by injecting fuel to the other cylinders in respective injection phases. According to this aspect, it is possible to start a diesel engine by injecting fuel into one cylinder by determining whether or not the injection pressure is equal to or higher than a predetermined pressure, and to another cylinder. Compared to the case where the diesel engine is started from this fuel injection, the startability of the diesel engine can be improved while saving the trouble of controlling the stop phase. In addition, after injecting fuel into one cylinder, the fuel can be injected into the respective injection phases of all the other cylinders and the fuel can be burned, so that the diesel engine can be shifted to the driving state after starting. it can.

  In another aspect of the second diesel engine automatic stop / start control method according to the present invention, the method further includes a depressurization step of depressurizing an in-cylinder pressure of the one cylinder when the diesel engine is started again.

  According to this aspect, by reducing the in-cylinder pressure of one cylinder to which fuel is not injected when starting the diesel engine, the piston of one cylinder that is driven in conjunction with the pistons of the other cylinders when starting the diesel engine On the other hand, the compression reaction force can be reduced. More specifically, for example, when one cylinder is in the compression stroke in the stop phase before being changed, a piston that reciprocates in one cylinder where fuel is not injected is caused by a compression reaction force or the like. It is desirable to reduce the generated wasted torque in order to speed up the engine rotation. Therefore, for example, by reducing the in-cylinder pressure of one cylinder by decompression or the like, it is possible to reduce the torque consumed in a plurality of cylinders included in the diesel engine, and to start the diesel engine quickly and efficiently. It becomes possible.

  In order to solve the above-described problem, a first diesel engine automatic stop / start control system according to the present invention automatically stops a multi-cylinder diesel engine in which the fuel is injected a plurality of times each time the fuel is pumped once. An automatic stop / start control system for a diesel engine for controlling start, wherein when the automatic stop condition for the diesel engine is satisfied, the diesel engine is stopped before the diesel engine is started again at the latest or Determining means for determining a stopped stop phase; phase determining means for determining whether or not there is a pumping phase for pumping the fuel between the stop phase and an injection phase for injecting the fuel; and the pumping phase If it is determined that the pumping phase is present between the stop phase and the injection phase, Comprising changing means for changing the stop phase, when starting the diesel engine again, and injection means for injecting the fuel pumped into the pumping phase to the ejection phase.

  According to the first automatic stop / start control system for a diesel engine according to the present invention, immediately after the restart of the diesel engine, as in the first automatic stop / start control method for a diesel engine of the present invention described above. A sufficient amount of fuel can be burned and the diesel engine can be started quickly. Therefore, the startability of the diesel engine can be improved.

  In order to solve the above problems, a second diesel engine automatic stop / start control system according to the present invention automatically stops and starts a multi-cylinder diesel engine in which fuel is injected a plurality of times each time the fuel is pumped once. A diesel engine automatic stop / start control system for controlling a diesel engine, and when a diesel engine automatic stop condition is satisfied for a plurality of cylinders included in the diesel engine, the diesel engine is restarted at the latest Determining means for determining a stop phase at which the diesel engine is stopped or stopped, and one cylinder from which the injection phase for injecting fuel first arrives among the plurality of cylinders from the stop phase to the one cylinder A phase determination unit for determining whether or not there is a pumping phase for pumping the fuel before the injection phase of When the diesel engine is restarted, the one cylinder determined that the pumping phase does not exist is not injected into the injection phase, and another injection phase comes after the one cylinder. Injection means for injecting the fuel pumped into the pumping phase into the injection phase of the other cylinder.

  According to the second automatic stop / start control system for a diesel engine according to the present invention, as in the above-described automatic stop / start control method for a diesel engine according to the second present invention, the control is performed according to the value of the injection pressure. It is possible to inject fuel into one cylinder or another cylinder. Therefore, a sufficient amount of fuel can be burned immediately after restarting the diesel engine without changing the stop position according to the injection pressure value, and the diesel engine can be started quickly. is there.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, a diesel engine automatic stop / start control method and system according to the present embodiment will be described in detail with reference to the drawings.

(First embodiment)
First, a diesel engine automatic stop / start control method and system according to a first embodiment will be described in detail with reference to FIGS. In this embodiment, the automatic stop / start control system for a diesel engine according to the present invention is applied to a common rail type diesel engine capable of eco-running and of one-pressure two-injection.

  First, the configuration of a diesel engine automatic stop / start control system according to this embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram illustrating an overall configuration of a diesel engine 1 including a diesel engine automatic stop / start control system according to the present embodiment, and FIG. 2 is a diagram for illustrating a configuration of a crank angle sensor. FIG. 3 is a diagram for explaining a crank angle calculation method. The functions of each part of the diesel engine automatic stop / start control system will be described in detail when the diesel engine automatic stop / start control method according to this embodiment is described.

  In FIG. 1, a diesel engine 1 includes an engine main body 10 having a plurality of cylinders, and a diesel engine automatic stop / start control system (hereinafter referred to as a control system) 100 that controls automatic stop and start of the diesel engine 1. It is configured with. The diesel engine 1 is a multi-cylinder in-line diesel engine in which a plurality (four in the figure) of cylinders (cylinders) 11 are arranged in one direction, and a piston is driven to reciprocate in the cylinder 11.

  The engine body 10 includes a plurality of cylinders 11 arranged in a cylinder block (not shown), pistons that can slide in the cylinders 11, a turbocharger 14, an intercooler 15, an intake manifold 16, a common rail 17, a fuel injection valve 18, an exhaust gas A manifold 19, an EGR (EGR: Exhaust Gas Recirculation) cooler catalyst unit 20, an EGR cooler 21, an EGR valve 22, a catalyst unit 23, and a fuel pump 24 are provided. In the diesel engine 1 according to the present embodiment, the cooler catalyst unit 20 is not essential, and a diesel engine that does not include the cooler catalyst unit 20 is also included in the category of the diesel engine 1.

  The common rail 17 temporarily stores the fuel pumped from the fuel pump 24 and supplies the fuel to the cylinder 11 via the fuel injection valve 18. The fuel pump 24 pumps fuel to the common rail 17 at a predetermined pumping phase. The fuel injection valve 18, which is an example of the “injection means” according to the present invention, is provided in each cylinder 11 and injects fuel in the injection phase under the control of the ECU 130.

  The intercooler 15 cools the intake air taken in via the turbocharger 14 and supplies the cooled intake air to the intake manifold 16. An air throttle valve 25 is disposed on the intake intake side of the intake manifold 16, and the flow rate of intake air taken into the intake manifold 16 is adjusted by adjusting the opening and closing of the air throttle valve 25. The intake manifold 16 supplies intake air to each cylinder 11 evenly.

  An EGR cooler 21, an EGR valve 22, an EGR cooler catalyst unit 20 for removing or purifying harmful substances contained in the exhaust, and a pipe connecting them are an EGR system for recirculating the exhaust as intake air of the engine body 10. Configure. According to the EGR system, the combustion temperature in the combustion chamber of the cylinder 11 can be lowered, and the generation of nitrogen oxides and the generation of exhaust particulates due to the increase in the intake air amount can be suppressed.

  The turbocharger 14 includes, for example, a turbine and a compressor (both not shown), and the turbine is rotated by the energy of the exhaust flowing in the exhaust manifold 19. The compressor is operated by power generated by the rotation of the turbine, and can compress the air in the intake pipe 26 and supply it to the combustion chamber side. That is, the turbocharger 14 has a function of controlling the intake air amount with respect to the combustion chamber.

  The catalyst unit 23 is disposed on the exhaust side of the engine body 10 and removes or purifies harmful substances contained in the exhaust. The catalyst unit 23 is equipped with, for example, a particulate filter system carrying an NOx storage reduction catalyst for removing or purifying harmful substances contained in exhaust gas.

  Each part of the engine body 10 is controlled by the control system 100. The control system 100 includes a sensor unit 110, a switch unit 120, an electronic control unit (ECU: Engine Control Unit) 130, a constant meshing gear mechanism 140, and a variable valve mechanism 150.

  The ECU 130 includes a digital computer and includes a ROM 132, a RAM 133, a CPU 134, a backup RAM 135, an input port 136, and an output port 137 connected to each other via a bidirectional bus 131. The ECU 130 controls operations of the engine main body 10, the constant mesh gear mechanism 140, and the variable valve mechanism 150 based on various information sent from the sensor unit 110 and the switch unit 120. The ECU 130 also serves as an example of “determination means”, “phase determination means”, and “drive time calculation means” according to the present invention.

  The sensor unit 110 includes an accelerator depression amount sensor 111, a crank angle sensor 112, a rail pressure sensor 113 which is an example of the “rail pressure detecting means” according to the present invention, a pump phase sensor 114, and an engine speed sensor 115. The crank angle sensor 112 detects a crank angle when the crankshaft rotates. The pump phase sensor 114 detects a pumping phase in which fuel is pumped from the fuel pump 24 to the common rail 17.

  In FIG. 2, each cylinder 11 is provided with a piston 33 connected to the connecting rod 32 and driven to reciprocate within the cylinder 11, and the crank angle sensor 112 rotates the crankshaft 34 that drives the piston 33. An angle (hereinafter referred to as “crank angle”) is detected.

  The crank angle sensor 112 includes two sensors, crank angle sensors 112a and 122b, which are disposed in the vicinity of the crankshaft 34 so as to be out of phase with each other. As the crank angle sensors 112a and 112b, for example, an object to be detected ( For example, a magnetic sensor capable of detecting a metal or the like can be used, and more specifically, a magnetoresistive element (MRE) sensor can be used. On the outer peripheral surface of the crankshaft 34, there are provided gears (hereinafter referred to as “signal rotor”) having irregularities, and the crank angle sensor 112 detects the number of teeth of the signal rotor. The crank angle sensor 112 can detect the crank angle of the crankshaft 34 with a resolution of about 10 ° CA (crank angle), for example. When the crankshaft 34 rotates, the signal rotor also rotates in conjunction with it. At this time, the crank angle sensor 112 detects the number of teeth of the signal rotor and outputs it to the ECU 130 as a pulse signal. ECU 130 counts the pulse signal output from crank angle sensor 112 and converts it to a crank angle. Since the crank angle sensor 112 is provided directly in the diesel engine 1, the crank angle can be detected as an absolute angle.

  3 is a chart showing the outputs of the crank angle sensors 112a and 112b. FIG. 3 (a) shows the output when the crankshaft 34 is normally rotated, and FIG. 3 (b) is the reverse of the crankshaft 34. Shows the output when MRE1 indicates the output of the crank angle sensor 112a, and MRE2 indicates the output of the crank angle sensor 112b.

  2, 3 (a) and 3 (b), the crank angle sensors 112 a and 112 b are arranged out of phase along the circumferential direction of the crankshaft 34, so that the crank angle when the signal rotor is detected is detected. There is a phase difference between the outputs of the sensors 112a and 112b. The ECU 130 compares the phase difference between the outputs of the two crank angle sensors 112a and 112b to determine whether the engine is normal or reverse. The ECU 130 can detect the crank angle with an accuracy of 10 ° CA by adding or subtracting the detected crank angle depending on whether the rotation direction of the crankshaft 34 is normal or reverse.

  In FIG. 1 again, the rail pressure sensor 113 detects the rail pressure of the common rail 17 and outputs information on the rail pressure to the ECU 130. The rail pressure tends to be lowered by the pressure reducing valve when the engine stops after the fuel is pumped once, and detecting the rail pressure is important for improving the startability of the diesel engine. .

  The constantly meshing gear mechanism 140 constituting an example of the “changing means” according to the present invention includes a gear train 141 and a starting motor 142. The starter motor 142 generates a rotational force according to a command from the ECU 130, and the gear train 141 transmits the rotational force transmitted from the starter motor 142 to the crankshaft of the engine body 10. More specifically, the gear train 141 includes a constantly meshing gear that always meshes with the pinion gear of the starter motor 141, and the rotational force generated by the starter motor 141 is a gear train 142, a ring gear that meshes with the gear train 142, and a ring gear. Is transmitted to the crankshaft via a flywheel rotated by the motor. The starter motor 142 also serves as an example of the “drive unit” according to the present invention under the control of the ECU 130 that controls the drive of the starter motor 142.

  A variable valve timing mechanism (VVT: Variable Valve Timing) 150 constitutes an example of the “pressure reducing means” according to the present invention, an intake valve for sending intake air into the combustion chamber of the cylinder 11, and after the fuel has burned An exhaust valve for exhausting the exhaust is provided. The intake valve is opened and closed by a control command from the ECU 130. For example, in a cylinder in the compression stroke, the cylinder pressure is prevented from increasing by retarding the timing for closing the intake valve. More specifically, the in-cylinder pressure of the cylinder in the compression stroke can be substantially reduced by performing decompression by retarding the closing timing of the intake valve. Thus, the variable valve mechanism 150 is characterized in that the valve opening and closing can be controlled independently for each cylinder.

  The switch unit 120 includes an ignition (IG) switch 121 and a starter motor (SM) switch 122. ECU 130 detects the on / off state of IG switch 121 based on the output signal of IG switch 121. When the IG switch 121 is changed from the on state to the off state, fuel injection by the fuel injection valve 18 is stopped, and the operation of the diesel engine 1 is stopped. The SM switch 122 is mainly used when the diesel engine 1 is started.

  Next, the diesel engine automatic stop / start control method according to the present embodiment will be described in detail with reference to FIGS. 4 and 5 in addition to FIG. 1. A vehicle equipped with the diesel engine 1 shifts to an idling stop state when traveling is stopped, and the diesel engine 1 is automatically stopped. Thereafter, when the driver removes his / her foot from the brake pedal and further depresses the accelerator pedal, the diesel engine 1 is automatically restarted. In order to start the diesel engine 1 smoothly, it is important to control the engine stop phase to an optimum state between the time of automatic stop and the time of restart. The stop phase means a crank angle when the diesel engine 1 is stopped. FIG. 4 is a flowchart showing an example of an automatic stop and start processing routine of the diesel engine automatic stop / start control method according to the present embodiment. FIG. 5 is a fuel injection phase with respect to the crank angle, and the fuel. It is a figure which shows the relationship of the pumping phase which pumps fuel from a pump. Note that the diesel engine automatic stop / start control method of this example is characterized by a process for automatically stopping the diesel engine, and a calculation process performed by the ECU 130 is executed by the CPU 134 included in the ECU 130.

  In FIG. 1 and FIG. 4, first, when a stop operation is performed to stop a vehicle equipped with the diesel engine 1 while waiting for a signal, a rate at which the engine speed Ne decreases during the stop operation and the engine speed Ne are calculated. The pump phase at which the fuel pump 24 pumps fuel is detected (S101). The engine speed Ne and the rate at which the engine speed Ne decreases are detected by the engine speed sensor 115. The pump phase is detected by the pump phase detection sensor 114, and the pressure feeding phase after the diesel engine 1 is automatically stopped is calculated by the ECU 130.

  Subsequently, the ECU 130 performs a stop determination of the diesel engine 1 (S102). When the determination immediately before the stop of the diesel engine 1 is performed, for example, the determination is made based on whether or not the engine rotational speed Ne has become a predetermined rotational speed Ne0 or less. When the rotational speed Ne of the diesel engine 1 is larger than the predetermined rotational speed Ne0, the process returns to step S101 again, and the process of step S101 is performed.

  When it is determined that the engine speed Ne is equal to or lower than the predetermined speed, the ECU 130 calculates an engine stop phase (S103). The stop phase is a crank angle when the engine is automatically stopped, and is calculated based on the detected engine speed Ne. When idling a vehicle equipped with the diesel engine 1, the inertial energy of the diesel engine 1 varies depending on the engine speed at the time of the stop operation, and the stop phase is linked to the inertial energy for each idling stop. Different. For this reason, ECU130 calculates a stop phase based on the engine speed Ne immediately before idling stop, for example. Note that the timing for calculating the engine stop phase is not limited to just before the diesel engine 1 is idling stopped, that is, automatically stopped. For example, the crank angle sensor directly detects the stop phase after the diesel engine stops. May be. That is, the stop phase only needs to be determined before the diesel engine 1 is started again at the latest.

  Subsequently, the ECU 130 determines whether or not the stop phase is included in the pumping period (S104). More specifically, it is determined whether or not there is a pumping phase between the stop phase and the injection phase for injecting fuel.

  Here, the relationship among the stop phase, the pumping phase, and the injection phase will be described in detail with reference to FIG. FIG. 5 shows the injection phase, the pumping phase, and the lift amount of the piston in order from the upper side.

  In FIG. 5, the four cylinders 11 provided in the engine body 10 are referred to as # 1, # 2, # 3, and # 4 in order. Each of the four cylinders 11 has an injection phase for injecting fuel in the order of # 1, # 3, # 4, and # 2. The injection phase is determined by an injection command output from the ECU 130 to the fuel injection valve 18. The diesel engine 1 according to the present embodiment employs a one-pressure-feed-two-injection fuel supply system in which fuel is injected into two cylinders once for each fuel pressure-feed from the fuel pump 24 to the common rail 17. . Therefore, when the diesel engine 1 is normally driven, a double injection phase exists between successive pumping phases. For example, after the pumping phase B, the injection phases # 3 and # 4 sequentially arrive, and after the pumping phase A, the injection phases # 2 and # 1 sequentially arrive.

  Here, since the pumping phase A exists in the period between the injection phase # 4 and the injection phase # 2, the period between the injection phase # 4 and the injection phase # 2 is set for convenience. This is called a pumping period TA. Similarly, there is no pumping phase between the injection phase of # 3 and the injection phase of # 4, and the period between the injection phase of # 3 and the injection phase of # 4 is a non-pumping period TB. Call it.

  Consider the startability of the diesel engine 1 when the diesel engine 1 stops in each of the stop phase a included in the pumping period TA and the stop phase b included in the non-pumping period TB.

  Fuel is pumped to the common rail 17 at the pumping phase B, fuel is injected at the injection phase # 3, and the rail pressure is reduced at the stop phase b located after the injection phase # 3. Accordingly, when the diesel engine 1 is started again after the diesel engine 1 is automatically stopped at the stop phase b, it is difficult to inject fuel with sufficient injection pressure at the injection phase # 4 that comes first after the start. It is. Further, since the compression stroke comes first to the # 4 cylinder after starting, a sufficient amount of fuel cannot be burned in the # 4 compression stroke, and it is difficult to start the diesel engine 1 quickly. .

  On the other hand, the stop phase a exists between the injection phase # 4 and the pumping phase A. When there is a start request for starting the diesel engine 1 after the diesel engine 1 stops at the stop phase a, first, fuel is pumped to the common rail 17 in the pumping phase A. Subsequently, the injection phase # 2 arrives, and fuel is injected at a sufficient injection pressure into the cylinder 11 corresponding to the injection phase # 2 from the common rail 17 in which the rail pressure is maintained at a high pressure. Therefore, when the diesel engine 1 stops at the stop phase a, when the diesel engine 1 is started again, the compression stroke first arrives at the # 2 cylinder, and fuel is injected at the injection phase # 2. As a result, sufficient fuel can be burned, and the diesel engine 1 can be started quickly.

  In consideration of the relationship between the stop phases a and b described above, in FIGS. 4 and 5 again, when it is determined that the pumping phase does not exist between the engine stop phase and the injection phase, that is, the engine stop phase. Is included in the non-pumping period, the engine stop phase is changed so that the pumping phase exists between the engine stop phase and the injection phase. In order to change the engine stop phase, the piston stop position is changed by rotating the crankshaft. Therefore, in order to change the stop position of the piston, the driving time of the starting motor is calculated (S105). More specifically, ECU 130 calculates a drive time for driving the crankshaft based on the pressure feed phase, the injection phase, and the stop phase calculated in step S103, and sends a drive command to start motor 142. The starter motor 142 generates a rotational force for a required time based on the drive command sent from the ECU 130, and rotates the crankshaft via the gear train 141 included in the constantly meshing gear mechanism 140. Thereby, for example, even when the diesel engine 1 is stopped at the stop phase b, the crack shaft is set so as to exceed the compression top dead center of the piston reciprocating in the # 4 cylinder by the rotational force generated by the starter motor 142. And the stop phase of the diesel engine 1 can be changed from the stop phase b to the stop phase a. That is, the stop position of the piston driven by the crankshaft is changed. After returning to step S101 and executing steps S102 and S103 again, if it is determined in step S104 that the pumping phase is between the engine stop phase and the injection phase, the engine stop operation is performed as it is. The process is terminated and the diesel engine 1 is set to an idling stop state. Then, when there is a start request, after the fuel is pumped to the first pumping phase, the diesel engine 1 is started by injecting the fuel at a sufficient injection pressure.

  According to the control method of such automatic stop / start of the diesel engine, when the diesel engine 1 is started again from the idling stop state, sufficient injection is performed from the common rail 17 to which fuel is pumped via the fuel injection valve 18. It is possible to inject fuel with pressure. Therefore, when the diesel engine 1 is started, the fuel required for combustion can be immediately injected into the combustion chamber, and the diesel engine can be started smoothly.

(Second Embodiment)
With reference to FIG.6 and FIG.7, the automatic stop and start control method and system of the diesel engine which concern on 2nd Embodiment are demonstrated in detail. FIG. 6 is a flowchart showing a processing routine of the diesel engine automatic stop / start control method according to the present embodiment, and FIG. 7 is a diagram schematically showing how the rail pressure decreases. . In this embodiment, as in the case of the first embodiment, the automatic stop / start control system for a diesel engine according to the present invention is applied to a common rail type diesel engine capable of eco-running and of 1 pumping and 2 injections. is there. In the second embodiment, the hardware configuration is almost the same as that in the first embodiment, and the control method is different from that in the first embodiment. That is, unlike the first embodiment, the second embodiment is characterized in that the engine can be started smoothly without changing the stop phase. Hereinafter, differences from the first embodiment according to the second embodiment will be described.

  In FIG. 6, in the present embodiment, first, when a stop operation of the diesel engine 1 is performed, the ECU 130 performs engine stop control and detects the crank position by the crank angle sensor 112. (S201). In step S201, the engine speed Ne is also detected by the engine speed sensor 115.

  Subsequently, the ECU 130 determines whether or not the engine speed Ne is equal to or lower than a predetermined engine speed Ne0 (S202). If it is determined that the engine speed Ne is greater than the predetermined engine speed Ne0, the process returns to step S201 again. When the engine speed Ne is equal to or lower than the engine speed Ne0, it is determined that the automatic stop condition is satisfied, and the process of the next step is performed. The engine speed Ne0 is set to 50 rpm, for example.

  Subsequently, the engine stop phase is calculated, and the cylinder in which fuel injection is scheduled to be performed first when the diesel engine 1 is started again is calculated (S203). Such a cylinder is a cylinder immediately before the compression stroke in the engine stop phase. Further, the pumping phase of the fuel pump 24 is detected by the pump phase sensor 114. The diesel engine 1 is automatically stopped by the processing so far.

  Next, processing at the time of starting performed following the above-described automatic stop processing will be described. First, a start request is made (S204). The start request is determined based on, for example, the depression amount detected by the accelerator depression amount sensor 111 or the depression amount of the brake pedal.

  Subsequently, it is determined whether or not the rail pressure detected immediately before starting the diesel engine 1 again is equal to or higher than a predetermined pressure (S205).

  In FIG. 7, after the engine is stopped, the rail pressure is rapidly reduced by the pressure reducing valve. For example, the horizontal axis in the figure is the elapsed time that has elapsed since the fuel was pumped, and the width of the entire horizontal axis in the figure corresponds to the time interval between the injection phases. In such a short time, the rail pressure falls below the pressure at which fuel can be injected.

  In FIG. 6 again, when the rail pressure is equal to or higher than the predetermined pressure, the start control is ended as it is, and the diesel engine 1 is made to be injected by injecting fuel into the cylinder in which the injection phase first arrives after the start. Start. On the other hand, when the rail pressure is lower than the predetermined pressure, the pumping phase is calculated based on the pump phase detected in step S203.

Subsequently, it is determined whether or not the engine stop phase is included in the pumping period (S206).
When the engine stop phase is included in the pumping period, the fuel is injected into the first compression cylinder in which the injection phase first arrives after the engine is started, and the diesel engine 1 is started (S207). When the engine stop phase is not included in the pumping period, after the engine stop phase, fuel is not injected into the first compression cylinder where the injection phase first arrives, and the injection phase follows the first compression cylinder. The incoming second compression cylinder is selected as a new first compression cylinder that first injects fuel when starting the diesel engine 1 (S208).

  Here, step S208 will be described in more detail with reference to FIGS. In step S208, the case where the engine stop position is not included in the pumping period means that the engine stop is in the stop phase b. At this time, the first compression cylinder, that is, the # 4 cylinder corresponds to an example of “one cylinder” according to the present invention, and the second compression cylinder, that is, the # 2 cylinder, corresponds to the “other cylinder” according to the present invention. This is an example. Therefore, the # 2 cylinder whose injection phase comes after the pumping phase A is selected as a new first compression cylinder when the engine is started.

  In FIG. 6 again, the in-cylinder pressure of the old first compression cylinder in which fuel is not injected is reduced (S209). In step S209, for example, the in-cylinder pressure can be reduced by operating the variable valve mechanism 150 under the control of the ECU 130. More specifically, by delaying the closing timing for closing the intake valve of the old first compression cylinder, decompression can be performed so that the in-cylinder pressure does not increase even when the old first compression cylinder is in the compression stroke. . Thereby, the starting torque at the time of starting the diesel engine 1 can be reduced, and the starting property of the diesel engine can be further improved. After step S209, the diesel engine 1 is shifted to normal operation, and the start control is terminated.

  As explained above, according to the diesel engine automatic stop / start control method according to the second embodiment, when the diesel engine 1 is started again, fuel can be injected from the common rail 17 having sufficient rail pressure. Yes, the diesel engine can be started quickly. Furthermore, the starting torque can be reduced by decompression, and the starting performance can be further improved.

  It should be noted that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. An engine automatic stop / start control method and a diesel engine automatic stop / start control system are also included in the technical scope of the present invention.

It is a figure which shows the structure of the diesel engine which concerns on this embodiment. It is a figure for demonstrating the crank angle detection method of detecting the crank angle of this embodiment. It is a figure which shows the output of the crank angle sensor of this embodiment. It is a flowchart which shows an example of the process routine of the automatic stop and start control method of the diesel engine which concerns on this embodiment. It is a figure for demonstrating the relationship of the injection phase of this embodiment, a pumping phase, and an engine stop phase. It is a flowchart which shows an example of the process routine of the automatic stop and start control method of the diesel engine which concerns on this embodiment. It is the figure which showed typically a mode that the rail pressure of this embodiment fell.

Explanation of symbols

  Diesel engine 1, fuel injection valve 18, control system 100, rail pressure sensor 113, constant mesh gear mechanism 140, starter motor 142, variable valve mechanism 150

Claims (3)

  A diesel engine automatic stop / start control method for controlling automatic stop and start of a multi-cylinder diesel engine in which fuel is injected multiple times each time fuel is pumped once,
  When the diesel engine automatic stop condition is satisfied for the plurality of cylinders included in the diesel engine, the stop phase of the diesel engine is stopped or stopped before the diesel engine is restarted at the latest. A decision process;
  Whether or not there is a pumping phase for pumping fuel between the stop phase and the injection phase of the one cylinder for one of the plurality of cylinders in which the injection phase for injecting fuel first arrives. A phase determination step for determining;
  When the diesel engine is restarted, the one cylinder determined not to have the pumping phase does not inject into the injection phase, and the other cylinder in which the injection phase comes next to the one cylinder An injection step of injecting the fuel pumped into the pumping phase into the injection phase of the other cylinder;
  Prior to the phase determination step, including a pressure determination step of determining whether or not an injection pressure for injecting the fuel is equal to or higher than a predetermined pressure,
  When it is determined that the injection pressure is not equal to or higher than the predetermined pressure, the phase determination step is executed,
  When it is determined that the injection pressure is equal to or higher than the predetermined pressure, the phase determination step is not executed and the injection step injects the fuel into all the injection phases of the plurality of cylinders.
  An automatic stop / start control method for a diesel engine.   When the diesel engine is started again, a pressure reducing step for reducing the in-cylinder pressure of the one cylinder is further provided.
  The diesel engine automatic stop / start control method according to claim 1.   A diesel engine automatic stop / start control method for controlling automatic stop and start of a multi-cylinder diesel engine in which fuel is injected multiple times each time fuel is pumped once,
  When the diesel engine automatic stop condition is satisfied for the plurality of cylinders included in the diesel engine, the stop phase of the diesel engine is stopped or stopped before the diesel engine is restarted at the latest. A decision process;
  Whether or not there is a pumping phase for pumping fuel between the stop phase and the injection phase of the one cylinder for one of the plurality of cylinders in which the injection phase for injecting fuel first arrives. A phase determination step for determining;
  When the diesel engine is restarted, the one cylinder determined not to have the pumping phase does not inject into the injection phase, and the other cylinder in which the injection phase comes next to the one cylinder An injection step of injecting the fuel pumped into the pumping phase into the injection phase of the other cylinder;
A depressurizing step for reducing the in-cylinder pressure of the one cylinder when starting the diesel engine again.
  An automatic stop / start control method for a diesel engine.

Images