JP3894153B2 - Diesel hybrid vehicle engine start control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control method for starting an engine of a diesel hybrid vehicle, and more particularly to a control method for starting an engine of a diesel hybrid vehicle that can improve the warm-up performance of the diesel engine and suppress the generation of white smoke.
[0002]
[Prior art]
In recent years, diesel hybrid vehicles have been developed from the viewpoint of conservation of the global environment and resource saving. The diesel hybrid vehicle includes a diesel engine provided with a filter for purifying exhaust gas in an exhaust passage, a stepped transmission capable of automatic transmission, and a clutch for connecting and separating power transmission between the diesel engine and the stepped transmission. And a motor generator for assisting power generation by diesel engine output or diesel engine output by battery power.
[0003]
The motor generator is configured to be capable of taking two operating states: a power running mode that functions as a motor that is a travel drive source, and a regenerative mode that functions as a generator. In the diesel hybrid vehicle configured in this manner, the stepped transmission is automatically shifted during shifting, and the clutch is automatically engaged and disengaged.
[0004]
Then, the driving force by the diesel engine and the driving force by the motor generator are properly used according to the traveling state, and the driving efficiency is controlled to be high. For example, at low speed (low rotation) or low load such as when starting, the engine efficiency is poor, so the diesel engine is stopped and the vehicle runs only with the motor, or during normal driving, both the diesel engine and the motor drive the wheels. To be controlled.
[0005]
By the way, in such a diesel hybrid vehicle, since the warm-up is insufficient when the diesel engine is started, white smoke is likely to be generated due to the injection fuel adhering to the inner wall surface of the cylinder, and exhaust purification. Therefore, the catalyst provided in the exhaust passage is not sufficiently activated, and there is a possibility that generation of white smoke cannot be sufficiently suppressed.
[0006]
In order to solve these problems, various related techniques have been proposed. That is, for example, a technology that improves soot and NOx while improving fuel consumption (see Patent Document 1), and when the catalyst is below the activation temperature, the engine and the motor generator are used in combination, and the special running by the engine alone from the normal running (See Patent Document 2), when the battery charge voltage is higher than the reference value, disengage the clutch, run the motor, generate power by the engine output, and increase the engine load to warm up the engine and catalyst (See Patent Document 3).
[0007]
[Patent Document 1]
JP 2002-234363 A [Patent Document 2]
JP 2001-115869 A [Patent Document 3]
Japanese Patent Laid-Open No. 2001-132491
[Problems to be solved by the invention]
The above prior art activates the catalyst by warming it up, and suppresses the generation of white smoke by removing the generated white smoke. However, due to further demands for the preservation of the global environment and resource saving, we are taking advantage of the fact that it is a diesel hybrid vehicle, and actively using this mechanism to warm up the engine during cold start, Although provision of a means for suppressing the generation of white smoke itself was desired, it was difficult to realize.
[0009]
The present invention has been made in view of the above, and an object of the present invention is to provide a control method for starting an engine of a diesel hybrid vehicle that can improve the warm-up performance of a diesel engine and suppress the generation of white smoke.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, a diesel hybrid vehicle engine start time control method according to the present invention includes a diesel engine and a motor generator as a driving source for traveling, a stepped transmission capable of automatic transmission, and the diesel engine. And a clutch that automatically performs power transmission / reception between the stepped transmission and the engine start control method for a diesel hybrid vehicle, when the diesel hybrid vehicle is started, the vehicle is driven only by the motor generator. In addition, the clutch engine is engaged, the diesel engine is driven by driving the motor generator, and fuel injection is started to start the diesel engine when a predetermined warm-up state is obtained. Is.
[0011]
Therefore, according to the present invention, the diesel engine can be operated in a region where the combustion efficiency is good, and the operation on the high load side can be performed by carrying out the driving operation of the diesel engine by the motor generator (motoring by EV traveling). Therefore, the warm-up period is shortened and the discharge of unburned fuel is suppressed, so that the generation of white smoke can be suppressed.
[0012]
In the engine start control method for a diesel hybrid vehicle according to the present invention, the diesel engine includes a variable valve mechanism, and the exhaust valve is kept closed by the variable valve mechanism when the diesel engine is rotated. It is characterized by this.
[0013]
Therefore, according to the present invention, the working fluid in the cylinder of the diesel engine is warmed by the sliding frictional heat of the piston by motoring the diesel engine with the motor generator while the exhaust valve is closed. The working fluid is repeatedly compressed and expanded by the reciprocating motion of the piston, and is also warmed by this action. Thereby, the warm-up property of a diesel engine improves and generation | occurrence | production of white smoke can further be suppressed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
[0015]
FIG. 1 is a schematic diagram showing a schematic configuration of a diesel hybrid vehicle according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a schematic configuration of a diesel engine. First, a schematic configuration of a diesel hybrid vehicle 10 that is a front wheel drive vehicle (FF vehicle) will be described with reference to FIGS. 1 and 2.
[0016]
The diesel hybrid vehicle 10 is provided with a diesel engine 11 as a travel drive source at the front of the vehicle. In the diesel engine 11, the fuel injection amount is controlled by a common rail fuel injection device 22 (see FIG. 2). Further, the diesel engine 11 has a variable valve timing mechanism (VVT) (not shown) that changes the valve lift amount according to the engine speed and continuously varies the cam phase (valve timing) according to the load, for example, an exhaust system. Prepared on the side.
[0017]
As shown in FIG. 2, the diesel engine 11 also includes an exhaust gas recirculation device (EGR device) 25. The EGR passage of the EGR device 25 is provided with an EGR cooler catalyst 26, an EGR cooler 27, and an EGR valve 28 in order from the exhaust side to the intake side.
[0018]
The diesel engine 11 includes a turbocharger 32. In an intake passage between the turbocharger 32 and the intake manifold, an intercooler 33 and a throttle valve 34 are provided for cooling the intake air that has been supercharged and heated. Further, in the exhaust passage 30 of the diesel engine 11, a particulate filter 31 carrying a NOx catalyst is provided to purify diesel particulates and NOx in the exhaust gas.
[0019]
The driving force generated by the diesel engine 11 is transmitted to a front wheel 13 as a main driving wheel via a multimode transmission (MMT) 12 and a drive shaft 14. The multi-mode transmission 12 automatically and electrically controls a gear shift operation with an actuator in accordance with a traveling state. That is, no torque converter is mounted.
[0020]
In addition, the diesel hybrid vehicle 10 is provided with a clutch 12a that performs contact / separation of power transmission between the diesel engine 11 and the stepped transmission of the multi-mode transmission 12, and the contact / separation operation is performed by an actuator according to the traveling state. It is designed to be automatically controlled electrically.
[0021]
Also, a propeller shaft 16 is connected to the transfer 15 that transmits the driving force separately, and a motor generator (MG) 17 integrated with a driving gear device (gear train) is connected to the end of the transfer shaft 15. In addition, the rear wheel 18 is configured to be rotated only by the front wheel 13 that is a driving wheel.
[0022]
The motor generator 17 is connected via an inverter 19 to a battery 20 that is a chargeable / dischargeable secondary battery. Further, the motor generator 17 is configured to be able to take two operation states, a power running operation mode that functions as a motor that is a travel drive source, and a regenerative operation mode that functions as a generator.
[0023]
For example, the motor generator 17 receives power supplied from the battery 20 in the power running operation mode and generates power for driving the drive shaft 14 via the propeller shaft 16. In the regenerative operation mode, the motor generator 17 converts the driving force transmitted from the diesel engine 11 or the drive shaft 14 via the propeller shaft 16 into electric power, and charges the battery 20. Whether the motor generator 17 is operated in the power running mode or the regenerative operation mode is determined in consideration of the state of charge (SOC) of the battery 20.
[0024]
The diesel hybrid vehicle 10 configured as described above is basically controlled as follows together with each component by an electronic control unit (ECU) (not shown), and can travel in various states. For example, in a relatively low speed state in which the diesel hybrid vehicle 10 starts traveling, it is normal to travel (EV traveling) by powering the motor generator 17 while the diesel engine 11 is stopped. As will be described later, at the time of cold start, the clutch is engaged during EV traveling, and the diesel engine 11 is rotated to improve the warm-up performance.
[0025]
When the diesel hybrid vehicle 10 reaches a predetermined speed or load after the start of traveling, fuel is injected to start the diesel engine 11 and the operation is shifted to the operation using the diesel engine 11. During steady operation, the diesel engine 11 is normally operated so as to generate an output substantially equal to the required power of the drive shaft 14. At this time, almost all of the output of the diesel engine 11 is transmitted to the drive shaft 14.
[0026]
On the other hand, when the state of charge SOC of the battery 20 has dropped below a predetermined reference value, the diesel engine 11 is operated with an output that exceeds the required power of the drive shaft 14, and a part of the surplus power is a motor. It is regenerated as electric power by the generator 17 and used for charging the battery 20. Further, when the torque of the diesel engine 11 is insufficient, the insufficient torque is assisted by driving the motor generator 17, and the necessary torque can be ensured.
[0027]
The diesel hybrid vehicle 10 is also subjected to so-called eco-run (economy & ecology running) control in order to save fuel and reduce exhaust emissions. That is, for example, when the diesel hybrid vehicle 10 stops due to a signal waiting at an intersection or the like, the diesel engine 11 is automatically stopped under a predetermined stop condition, and then the predetermined restart condition (for example, the accelerator pedal is depressed). At a time), the diesel engine 11 is also restarted.
[0028]
The above is the basic configuration and basic control operation of the diesel hybrid vehicle 10 according to the present invention.
[0029]
Next, an engine start time control method of the diesel hybrid vehicle 10 which is a main part of the present invention will be described with reference to FIGS. Here, FIG. 3 is a flowchart showing a control method for starting the engine of the diesel hybrid vehicle 10.
[0030]
As shown in FIG. 3, when the diesel hybrid vehicle 10 is started, first, EV running is performed by the motor generator 17 (step S10). At this time, a clutch (not shown) is engaged with the diesel engine 11, and the motor generator 17 is in a state of rotating the diesel engine 11. That is, the diesel engine 11 is in a so-called motoring state (step S11).
[0031]
Further, the diesel engine 11 keeps an exhaust valve (not shown) closed by a variable valve timing mechanism (not shown). Thus, by motoring with the exhaust valve closed, the working fluid in the cylinder of the diesel engine 11 is warmed by the sliding frictional heat of the piston and is repeatedly compressed and expanded by the reciprocating motion of the piston. It will also be warmed by the action. That is, the warm-up property is improved.
[0032]
Next, whether or not the diesel engine 11 has been warmed up is determined by monitoring the temperature of the engine coolant (step S12). That is, for example, it is determined whether the temperature of the cooling water has reached a predetermined temperature (for example, 40 ° C.) set in advance.
[0033]
If the diesel engine 11 is warmed up (Yes at Step S12), motoring by EV traveling is finished, fuel is injected by the common rail fuel injection device 22, and the diesel engine 11 is started (Step S13). At this time, since the gas temperature in the cylinder is increased due to warm-up, the combustion efficiency is increased and the generation of white smoke can be suppressed. When the motoring is finished, the closed exhaust valve (not shown) is appropriately opened by a variable valve timing mechanism (not shown).
[0034]
On the other hand, if the diesel engine 11 is not warmed up (No at Step S12), fuel injection is not performed, and motoring by EV traveling is continued until the engine is warmed up (Step S10, Step S11). This is because, for example, when the fuel injection amount is small at low load, the excess air ratio increases and misfires occur, unburned fuel is discharged and white smoke is generated.
[0035]
When the diesel engine 11 is started by the start of fuel injection (step S13), since the battery 20 has been discharged because EV traveling has been performed so far, the state of charge SOC of the battery 20 should have decreased. Therefore, in order to charge the battery 20, the diesel engine 11 is operated at a higher load side than normal (step S14).
[0036]
In other words, the diesel engine 11 is loaded with an extra load required for the motor generator 17 in addition to the load (normal load) required from the drive shaft 14 for traveling. Operate on the high-load side by the amount of regeneration compared to normal times. Thereby, the battery 20 is charged. Thus, since the diesel engine 11 is required to operate in addition to the load required from the drive shaft 14, the operation that can bear the regenerative load of the motor generator 17, the high load side operation of the diesel engine 11 is This means that the vehicle is operated with a load that is higher by a predetermined amount than the normal time according to the load of the regeneration.
[0037]
Next, in order to determine the state of charge of the battery 20, it is determined whether or not the state of charge SOC is greater than a preset threshold value (step S15). If the state of charge SOC of the battery 20 is larger than the threshold value (Yes at Step S15), the diesel engine 11 is operated in a normal load state because it is charged.
[0038]
On the other hand, if the state of charge SOC of the battery 20 is smaller than the threshold value (No in step S15), the high load side operation is continued until the battery 20 is sufficiently charged because the charge is insufficient (step S13, step S14).
[0039]
As described above, according to the engine start time control method of the diesel hybrid vehicle 10 according to this embodiment, the diesel engine 11 can be operated in a region where the combustion efficiency is good by performing motoring by EV traveling, and Since this is a high-load operation, the warm-up period is shortened, and the generation of white smoke can be further suppressed.
[0040]
【The invention's effect】
As described above, according to the engine start control method for a diesel hybrid vehicle according to the present invention, a diesel engine and a motor generator as a driving source for traveling, a stepped transmission capable of automatic transmission, and the diesel engine In a control method at the time of engine start of a diesel hybrid vehicle provided with a clutch that automatically performs power transmission / reception between the stepped transmissions, when the diesel hybrid vehicle is started, only the motor generator travels. The clutch engine is engaged, the motor generator is driven to rotate the diesel engine, and when a predetermined warm-up state is obtained, fuel injection is started and the diesel engine is started. , Diesel engine by motor generator By carrying out revolving operation (motoring by EV traveling), the diesel engine can be operated in a region where the combustion efficiency is good and the operation is performed on the high load side. Since the discharge | emission of is suppressed, generation | occurrence | production of white smoke can be suppressed.
[0041]
According to the engine start control method for a diesel hybrid vehicle according to the present invention, the diesel engine includes a variable valve mechanism, and the exhaust valve is closed by the variable valve mechanism when the diesel engine is rotated. Therefore, the working fluid in the cylinder of the diesel engine is warmed by the sliding frictional heat of the piston. The working fluid is repeatedly compressed and expanded by the reciprocating motion of the piston, and is also warmed by this action. Therefore, the warm-up property of the diesel engine is improved, and the generation of white smoke can be further suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a diesel hybrid vehicle according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a schematic configuration of a diesel engine.
FIG. 3 is a flowchart showing a control method for starting an engine of a diesel hybrid vehicle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Diesel hybrid vehicle 11 Diesel engine 12 Multimode transmission 12a Clutch 13 Front wheel 14 Drive shaft 15 Transfer 16 Propeller shaft 17 Motor generator 18 Rear wheel 19 Inverter 20 Battery

Claims (2)

A diesel engine and a motor generator as a driving source for traveling, a stepped transmission capable of automatic transmission, a clutch for automatically connecting and disconnecting power transmission between the diesel engine and the stepped transmission, and the motor generator In a control method at the time of engine start of a diesel hybrid vehicle having a chargeable / dischargeable battery connected to
Wherein when the starting control of the diesel engine of a diesel hybrid vehicle, the only performs running by the motor generator, wherein the Succoth Kai take the diesel engine engages the clutch by driving the motor generator The battery charge state is lowered, and when a predetermined warm-up state is obtained, fuel injection is started and the diesel engine is started to perform high load side operation for charging the battery to the diesel engine. A control method for starting an engine of a diesel hybrid vehicle.   2. The engine of a diesel hybrid vehicle according to claim 1, wherein the diesel engine includes a variable valve mechanism, and the exhaust valve is kept closed by the variable valve mechanism when the diesel engine is rotated. Control method.

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