JP2004324442A - Control method in starting engine of diesel hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method in starting an engine of a diesel hybrid vehicle capable of improving the warming-up performance of a diesel engine and suppressing the generation of white smoke. <P>SOLUTION: When starting the diesel hybrid vehicle 10, EV travel by a motor generator 17 is performed, and a clutch 12a is engaged to corotate the diesel engine 11. When acquiring a prescribed warming-up state, fuel injection is started to start the diesel engine 11. When corotating the diesel engine 11, an exhaust valve (not shown in the figure) is kept closed by a variable valve timing mechanism (not shown in the figure). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an engine start control method for a diesel hybrid vehicle, and more particularly, to a diesel hybrid vehicle engine start control method capable of improving warm-up properties of a diesel engine and suppressing generation of white smoke.
[0002]
[Prior art]
2. Description of the Related Art In recent years, diesel hybrid vehicles have been developed from the viewpoint of global environment conservation and resource saving. This 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 engaging and disengaging power transmission between the diesel engine and the stepped transmission. And a motor generator for assisting power generation by the diesel engine output or assisting the diesel engine output by the battery power.
[0003]
The motor generator is configured to be able to take two operation states, a powering operation mode functioning as a motor serving as a traveling drive source, and a regenerative operation mode functioning as a generator. In the diesel hybrid vehicle configured as described above, the stepped transmission is automatically shifted when shifting, and the clutch is automatically engaged and disengaged.
[0004]
Then, the driving force of the diesel engine and the driving force of the motor generator are selectively used according to the traveling state, and the driving efficiency is controlled so as to increase. For example, at low speed (low rotation) or low load, such as when starting, the engine efficiency is poor. Therefore, the diesel engine is stopped and the vehicle runs only with the motor. During normal driving, both the diesel engine and the motor drive the wheels. Is controlled to
[0005]
By the way, in such a diesel hybrid vehicle, since the warm-up is insufficient at the start of the diesel engine, white fuel is likely to be generated due to the adhesion of the injected fuel to the inner wall of the cylinder, and the exhaust purification. Therefore, the catalyst provided in the exhaust passage is not sufficiently activated, and the generation of white smoke may not be sufficiently suppressed.
[0006]
In order to solve these problems, various related technologies have been proposed. That is, for example, a technique for satisfactorily treating soot and NOx while improving fuel efficiency (see Patent Literature 1). When the catalyst is at or below the activation temperature, the engine and the motor generator are used in combination, and the special traveling using only the engine from normal traveling (See Patent Document 2), when the battery charging voltage is equal to or higher than the reference value, the clutch is disengaged, the motor is driven, the power is generated by the engine output, the engine load is increased, and the engine and the catalyst are warmed up. (See Patent Document 3).
[0007]
[Patent Document 1]
JP 2002-234363 A [Patent Document 2]
JP 2001-115869 A [Patent Document 3]
JP 2001-132491 A
[Problems to be solved by the invention]
In the above-mentioned conventional technology, the catalyst is activated by warming it up, and the generation of white smoke is suppressed by removing the generated white smoke. However, from the further demand for global environmental conservation and resource saving, taking advantage of the diesel hybrid vehicle, by actively utilizing this mechanism, the engine is warmed up at cold start, and the It has been desired to provide a means for suppressing the generation of white smoke itself, but it has been difficult to achieve this.
[0009]
The present invention has been made in view of the above, and an object of the present invention is to provide an engine start control method for a diesel hybrid vehicle that can improve warm-up properties of a diesel engine and suppress generation of white smoke.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a method for controlling the start of an engine of a diesel hybrid vehicle according to the present invention includes a diesel engine and a motor generator as a drive source for traveling, a stepped transmission capable of automatic transmission, and the diesel engine. And a clutch for automatically engaging and disengaging power transmission between the stepped transmission and an engine start control method for a diesel hybrid vehicle, wherein when the diesel hybrid vehicle is started, travel is performed only by the motor generator. At the same time, the diesel engine is entrained by driving the motor generator by engaging the clutch, and when a predetermined warm-up state is obtained, fuel injection is started to start the diesel engine. Things.
[0011]
Therefore, according to the present invention, by carrying out the entrained driving of the diesel engine by the motor generator (motoring by EV running), the diesel engine can be operated in a region with good combustion efficiency, and the operation on the high load side can be achieved. Accordingly, the warm-up period is shortened, and the emission of unburned fuel is suppressed, so that the generation of white smoke can be suppressed.
[0012]
Further, in the method for controlling the start of an engine of a diesel hybrid vehicle according to the present invention, the diesel engine includes a variable valve mechanism, and when the diesel engine is driven, the exhaust valve is kept closed by the variable valve mechanism. It is characterized by the following.
[0013]
Therefore, according to the present invention, the working fluid in the cylinder of the diesel engine is heated by the sliding friction heat of the piston by motoring the diesel engine by 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 heated by this action. As a result, the warm-up property of the diesel engine is improved, and the generation of white smoke can be further suppressed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited by the embodiment.
[0015]
FIG. 1 is a schematic diagram illustrating a schematic configuration of a diesel hybrid vehicle according to an embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating a schematic configuration of a diesel engine. First, a schematic configuration of a diesel hybrid vehicle 10, which is a front-wheel drive vehicle (FF vehicle), will be described with reference to FIGS.
[0016]
The diesel hybrid vehicle 10 is provided with a diesel engine 11 as a traveling drive source at the front of the vehicle. The fuel injection amount of the diesel engine 11 is controlled by a common rail fuel injection device 22 (see FIG. 2). Further, the diesel engine 11 includes a variable valve timing mechanism (VVT) (not shown) for continuously switching a valve lift amount according to the engine speed and continuously varying a cam phase (valve timing) according to a 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 for cooling intake air that has been supercharged and heated are provided. Further, a particulate filter 31 carrying a NOx catalyst is provided in the exhaust passage 30 of the diesel engine 11 in order 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 multi-mode transmission (MMT) 12 and a drive shaft 14. The multi-mode transmission 12 electrically controls automatically the gear shifting operation in accordance with the traveling state with an actuator. That is, no torque converter is mounted.
[0020]
Further, the diesel hybrid vehicle 10 is provided with a clutch 12a for engaging and disengaging the power transmission between the diesel engine 11 and the stepped transmission of the multi-mode transmission 12, and the engaging and disengaging operation is performed by an actuator in accordance with the traveling state. It is electrically controlled automatically.
[0021]
Further, a propeller shaft 16 is connected to the transfer 15 for transmitting the driving force separately, and a motor generator (MG) 17 having a drive system gear unit (gear train) integrated therewith is connected to an end thereof. Further, the rear wheel 18 is configured to be merely rotated by the front wheel 13 which is a driving wheel.
[0022]
The motor generator 17 is connected via an inverter 19 to a battery 20 which is a chargeable / dischargeable secondary battery. The motor generator 17 is configured to be able to take two operation states, a powering operation mode functioning as a motor that is a driving source for driving, and a regenerative operation mode functioning as a generator.
[0023]
For example, motor generator 17 receives power supply from battery 20 in the powering operation mode and generates power for driving drive shaft 14 via 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 operation 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 by an electronic control unit (ECU) (not shown) together with each component as follows, and can travel in various states. For example, in a relatively low-speed state in which the diesel hybrid vehicle 10 starts running, it is normal to run (EV running) by powering the motor generator 17 with the diesel engine 11 stopped, but in the present invention. As will be described later, during cold start, the clutch is engaged during EV running, and control is performed to improve the warm-up property by rotating the diesel engine 11 together.
[0025]
When the diesel hybrid vehicle 10 reaches a predetermined speed or load after the start of traveling, the diesel engine 11 is started by injecting fuel, and the operation shifts to operation using the diesel engine 11. During a steady operation, normally, the diesel engine 11 is 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 is lower than the predetermined reference value, the diesel engine 11 is operated at an output higher than the required power of the drive shaft 14, and a part of the surplus power is The power is regenerated by the generator 17 and used for charging the battery 20. When the torque of the diesel engine 11 is insufficient, the insufficient torque is assisted by driving the motor generator 17, and the required torque can be secured.
[0027]
The diesel hybrid vehicle 10 is also subjected to so-called eco-run (economy & ecological running) control in order to save fuel and reduce exhaust emissions. That is, for example, when the diesel hybrid vehicle 10 stops at a traffic light at an intersection or the like, the diesel engine 11 is automatically stopped under a predetermined stop condition, and then, under a predetermined restart condition (for example, when an accelerator pedal is depressed). At time), control to restart the diesel engine 11 is also performed.
[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 control method for 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 illustrating a control method at the time of engine start of the diesel hybrid vehicle 10.
[0030]
As shown in FIG. 3, when starting the diesel hybrid vehicle 10, first, the EV running is performed by the motor generator 17 (step S10). At this time, the clutch (not shown) is engaged with the diesel engine 11 and the motor generator 17 is 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). As described above, by performing motoring with the exhaust valve closed, the working fluid in the cylinder of the diesel engine 11 is heated by the sliding friction heat of the piston, and repeatedly compresses and expands due to the reciprocating motion of the piston. It will also be warmed by the action. That is, the warm-up property is improved.
[0032]
Next, it is determined whether the diesel engine 11 has been warmed up by monitoring the temperature of the engine cooling water (step S12). That is, for example, it is determined whether or not the temperature of the cooling water has reached a preset predetermined temperature (for example, 40 ° C.).
[0033]
If the diesel engine 11 has been warmed up (Yes at step S12), the motoring by EV running 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 by the warm-up, the combustion efficiency is increased and the generation of white smoke can be suppressed. At the end of motoring, 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 diesel engine 11 is warmed up (Steps S10 and S11). This is because, for example, when the fuel injection amount is small at the time of low load, the excess air ratio increases, causing misfire, discharging unburned fuel, and generating white smoke.
[0035]
When the diesel engine 11 is started by the start of fuel injection (step S13), since the battery 20 has been discharged since the EV traveling has been performed, 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 on a higher load side than usual (step S14).
[0036]
That is, in addition to the load (normal load) required from the drive shaft 14 for traveling, the diesel engine 11 has an additional load corresponding to the regeneration of the motor generator 17. The motor is operated on the higher load side for the amount of regeneration than usual. As a result, the battery 20 is charged. As described above, since the diesel engine 11 is required to operate not only with the load required from the drive shaft 14 but also with the regenerative load of the motor generator 17, the high-load operation of the diesel engine 11 is as follows. This means that the vehicle is operated with a load higher by a predetermined amount than the normal time in accordance with the load of the regenerated power.
[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 (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 under the normal load state because the battery is charged.
[0038]
On the other hand, if the state of charge SOC of the battery 20 is smaller than the threshold value (No at Step S15), the charging is insufficient, and the high-load side operation is continued until the battery is sufficiently charged (Steps S13 and S14).
[0039]
As described above, according to the control method at the time of engine start of the diesel hybrid vehicle 10 according to the present embodiment, by performing the motoring by the EV traveling, the diesel engine 11 can be operated in a region with good combustion efficiency, and Since this is an operation on the high load side, 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 An engine start control method for a diesel hybrid vehicle including a clutch that automatically engages and disengages power transmission between the stepped transmissions, wherein at the time of starting the diesel hybrid vehicle, only the motor generator travels. The diesel engine is entrained by driving the motor generator by engaging the clutch, and when a predetermined warm-up state is obtained, fuel injection is started to start the diesel engine. , Diesel engine by motor generator By performing the entrained operation (motoring by EV running), the diesel engine can be operated in a region with good combustion efficiency and is operated on the high load side, so that the warm-up period is shortened and the unburned fuel is reduced. The emission of white smoke can be suppressed because the emission of white smoke is suppressed.
[0041]
Further, according to the control method at the time of engine start of a diesel hybrid vehicle according to the present invention, the diesel engine includes a variable valve mechanism, and when the diesel engine is rotated, the exhaust valve is kept closed by the variable valve mechanism. Therefore, the working fluid in the cylinder of the diesel engine is heated by the sliding friction heat of the piston. This 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 illustrating a control method at the time of engine start of a diesel hybrid vehicle.
[Explanation of symbols]
Reference Signs List 10 diesel hybrid vehicle 11 diesel engine 12 multi-mode 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 comprising: a diesel engine and a motor generator as a drive source for traveling; a stepped transmission capable of automatic transmission; and a clutch for automatically engaging and disengaging power transmission between the diesel engine and the stepped transmission. In the control method at the time of starting the engine of the hybrid vehicle,
When the diesel hybrid vehicle is started, the vehicle is driven only by the motor generator, the clutch is engaged, the diesel engine is driven by the drive of the motor generator, and the fuel is released when a predetermined warm-up state is obtained. An engine start control method for a diesel hybrid vehicle, characterized by starting injection and starting the diesel engine. The engine start of the diesel hybrid vehicle according to claim 1, wherein the diesel engine has a variable valve mechanism, and the exhaust valve is kept closed by the variable valve mechanism when the diesel engine is rotated. Time control method.

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