JP2009209722A - Start control device and start control method for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly improve pressure reduction effect and engine startability without deteriorating exhaust emission and operability when it is judged that engine start is required in an early stage in a hybrid vehicle or the like. <P>SOLUTION: It is judged based on cooling water temperature or the like during cranking whether combustion can be done or not (S104) when a diesel engine provided with a compression pressure reduction means is started in the hybrid vehicle or the like. If it is judged that combustion can be done, and if accelerator opening is not less than prescribed value or accelerator opening change quantity is not less than prescribed value (S105, S108), operation of the compression pressure reduction means is stopped and fuel injection is permitted (S106). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine start control device and a start control method, and more particularly to an engine start control device provided with a compression pressure reducing means for reducing compression pressure in a cylinder and suppressing engine vibration when the engine is started. And a start control method.

Patent document 1 includes means for retarding engine vibration by retarding the valve opening / closing timing to lower the effective compression ratio in the cylinder and reducing the cylinder compression reaction force when the engine is started. When the engine is started with the driver's positive intention or when the startability of the engine is low, such as at low temperatures, etc. There is described a technique for speeding up the start-up by not setting the retarded state.
JP 2002-256910 A

  However, even if the engine tries to start combustion immediately after cranking starts, stable combustion may not be obtained depending on the combustion chamber temperature, fuel injection pressure, and the like. If fuel is injected and burned in such a state, exhaust may deteriorate due to poor combustion or torque variation may occur, resulting in poor operability. Considering this point, when continuing cranking without injecting fuel until stable combustion is possible, the compression pressure is required when the engine needs to be started early as in Patent Document 1. In the configuration in which the reduction is not performed, there is a problem that the vibration reduction effect cannot be obtained while the cranking is continued.

  The present invention has been made paying attention to the above-mentioned problems, and when an early start of the engine is required, an engine start control device capable of achieving both engine vibration suppression and early start without deteriorating exhaust and operability. It is another object of the present invention to provide a start control method.

  For this reason, the engine start control device of the present invention is a combustion propriety judging means for judging whether or not combustion in the cylinder is possible in an engine provided with a compression pressure reducing means that operates at the time of starting to reduce the compression pressure in the cylinder. Torque request status determination means for determining a torque request status for the prime mover including the engine, wherein the combustion availability determination means determines that combustion is possible, and the torque request status determination means determines the torque request status for the prime mover. When it is determined that the predetermined condition is satisfied, the operation of the compression pressure reducing means is stopped and fuel injection is started even if the engine rotational speed is in the operating region of the compression pressure reducing means. And

  The engine start control method of the present invention determines whether combustion in the cylinder is possible or not when starting an engine provided with a compression pressure reducing means that operates at the time of startup to reduce the compression pressure in the cylinder. When the torque request status for the prime mover including the engine is determined, combustion is possible, and the torque request status for the prime mover satisfies a predetermined condition, even if the engine rotational speed is in the operating region of the compression pressure reducing means, The operation of the compression pressure reducing means is stopped and fuel injection is started.

  According to the present invention, when it is determined that the engine needs to be started early based on a torque request to the prime mover, the compression pressure reducing means can be used even if the engine speed is within the operating range of the compression pressure reducing means if combustion is possible. If the combustion is not possible and the combustion is not possible, the vibration is suppressed by the operation of the compression pressure reducing means, so that the engine can be operated without impairing the vibration suppressing effect during cranking, and without deteriorating the exhaust and operability. It is possible to start early.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a power train of a one-motor type hybrid vehicle to which the present invention is applied.

  In FIG. 1, the output shaft of the engine 1 is connected to a motor / generator 3 via a clutch 2, and the motor / generator 3 is connected to a transmission 5 via a clutch 4. Here, the engine 1 and the motor / generator 3 constitute a prime mover.

  The inverter 6 converts the DC power from the battery 7 into AC power and outputs it to the motor / generator 3 to drive the motor / generator 3 as a motor. Further, when the motor / generator 3 functions as a generator, the inverter 6 converts the generated power from the motor / generator 3 into DC power and charges the battery 7.

  The engine 1 is controlled by an engine controller (hereinafter referred to as ECM) 8, the motor / generator 3 is controlled by a motor controller (hereinafter referred to as MC) 9, and these ECM 8 and MC 9 are hybrid controllers (hereinafter referred to as HCM). Are collectively controlled by a control signal from 10. The HCM 10 also outputs control signals to the clutches 2 and 4 and the inverter 6.

FIG. 2 is a system block diagram of the hybrid vehicle described above.
The HCM 10 outputs predetermined control signals to the ECM 8 and MC 9 based on signals input from various sensors.

  Signals input to the HCM 10 include an engine speed signal NE from the speed sensor 11, an accelerator position signal APS from the accelerator position sensor 12, a cooling water temperature signal TW from the water temperature sensor 13, and an intake temperature from the intake air temperature sensor 14. These are the air temperature signal TA, the intake pressure signal PA from the intake pressure sensor 15, the fuel pressure signal PF from the fuel pressure sensor 16, and the like.

  Control signals output from the HCM 10 include a target engine torque signal and compression pressure reduction permission / stop signal for the ECM 8, a control switching signal (torque control / rotational speed control) for the MC 9, a target torque signal, a target rotational speed signal, and the like. . Based on the compression pressure reduction permission / stop signal of the HCM 10, the compression pressure reduction means control signal is output from the ECM 8 to the compression pressure reduction means 17.

  The HCM 10 outputs a predetermined control signal to the ECM 8 and MC 9 when the engine is started, cranks the engine 1 by the motor / generator 3 and generates a compression pressure reducing means control signal from the ECM 8 to reduce the compression pressure. The vibration of the engine 1 is suppressed by operating the means 17. Further, as described later, during cranking, whether or not combustion in the cylinder is possible is determined based on at least one of the coolant temperature TW, the intake air temperature TA, the intake air pressure PA, and the fuel pressure PF, and the prime mover is determined from the accelerator opening signal APS. When it is determined that the torque request status for the engine satisfies the predetermined condition by the engine start request by the driver's positive intention, the operation / stop of the compression pressure reducing means 17 is controlled according to the determination result of whether combustion is possible. Here, the HCM 10 has functions of a combustion allowance determination unit and a torque request status determination unit.

FIG. 3 shows an example of the engine 1.
The engine 1 is a diesel engine, and intake air is drawn into a cylinder 27 from an air cleaner 21 via an intake valve 26 that is opened and closed by an intake passage 22, a collector 23, an intake manifold 24, and an intake cam 25.

  A piston 28 is inserted into the cylinder 27, and fuel is injected and supplied by a fuel injection valve 29. The combustion exhaust is discharged to an exhaust passage 32 through an exhaust valve 31 that is opened and closed by an exhaust cam 30.

A part of the exhaust gas is introduced into the EGR passage 33 as EGR gas, and is returned to the intake manifold 24 while the EGR amount is controlled by the EGR valve 34.
And as said compression pressure reduction means 17, at least 1 is provided among the following each means.

  The throttle valve 34 is constituted by a butterfly valve, for example, and reduces the cross-sectional area of the intake passage 22 for a predetermined period at the time of starting to lower the pressure (intake pressure) downstream of the valve, thereby reducing the compression pressure (FIG. 4A )reference).

  The intake shut-off valve 35 is composed of a butterfly valve, a flap valve, a poppet valve, etc., and shuts off the intake passage continuously or in a predetermined section (intake stroke) in one cycle, lowers the pressure downstream of the valve, and reduces the compression pressure. To reduce. Preferably, the “closed” timing is adjusted so that the fluctuation in the cylinder pressure does not occur in one cycle (see FIG. 4B).

  The intake valve characteristic variable means (intake valve opening / closing timing variable means or intake valve operating angle variable means) 36 changes the valve center angle by changing the phase of the intake cam or uses a plurality of cams having different profiles. Using other known variable valve mechanisms such as switching, the compression pressure is reduced by changing (limiting) the amount of air flowing into the cylinder during the intake stroke. (See FIG. 4C). The continuously variable type has no step when changing the cylinder internal pressure, and the switching type has the advantage that the compression pressure can be changed quickly.

  When the decompression device 37 shown in FIG. 5 is operated (ON), a valve provided separately from the intake / exhaust valves 26 and 31 or the intake valve 26 is opened to release the air in the cylinder 27 to the intake passage and compress the pressure. By opening the other valve or the intake valve 26 by a minute amount in the compression stroke, the air in the cylinder 27 is released to the intake passage also in the compression stroke.

Next, the control operation of the HCM 10 when the engine is started will be described with reference to the flowchart of FIG. In the following description, an example of determining whether combustion is possible based on the coolant temperature TW will be described.
When a start request for the engine 1 is generated and cranking of the engine 1 is started, in step S101, the engine speed NE, the coolant temperature TW, and the accelerator opening APS are read. When the start request is generated, the ignition key is switched from “OFF” to “ON”, or the target engine torque calculated by the HCM 10 is changed from “0” to “greater than 0”. To do. The cranking is performed by outputting a torque control signal and a target torque from the HCM 10 to the MC 9, and driving and controlling the motor / generator 3 by the MC 9 so that the target torque is realized.

In step S102, it is determined whether or not cranking is being performed. If cranking is being performed, the process proceeds to step S103.
In step S103, it is determined whether or not the read engine rotational speed NE is lower than a predetermined value NE-L. The predetermined value NE-L is set higher than the resonance range based on the resonance range of the engine mount or drive system in which the engine 1 resonates, and is an engine rotation speed that defines the operation end point of the compression pressure reducing means 17. . If it is determined that the engine speed NE <predetermined value NE-L, the process proceeds to step S104.

  In step S104, whether or not combustion in the cylinder 27 is possible is determined based on the read engine rotation speed NE and the coolant temperature TW based on the characteristic map of FIG. While it is determined that combustion is impossible, the process proceeds to step S109, where the compression pressure reducing means 17 is operated and fuel injection is prohibited. On the other hand, if it is determined that combustion is possible, the process proceeds to step S105. Here, it is determined whether combustion is possible from the cooling water temperature TW, but fuel availability may be determined from the intake air temperature TA, the intake pressure PA, or the fuel pressure PF. The cooling water temperature TW, the intake air temperature TA, Whether or not fuel is available can be determined from at least one of the intake pressure PA and the fuel pressure PF. 7B to 7D show characteristic maps for determining fuel availability based on the intake air temperature TA, the intake pressure PA, and the fuel pressure PF. Each characteristic of FIG. 7 is in a state where the compression pressure reducing means 17 is not operated. When the fuel pressure PF is used, the fuel pump is driven by the engine.

  In step S105, it is determined whether or not the read accelerator opening APS is equal to or greater than a predetermined opening APS-L. If the accelerator opening APS is less than the predetermined opening APS-L, the process proceeds to step S108. It is determined whether or not the opening change amount (= APS (current value) −bAPS (previous value)) is equal to or greater than a predetermined change amount dAPS-L. In step S105, it is determined that accelerator opening APS ≧ predetermined opening APS-L, or in S108, accelerator opening change amount (= APS (current value) −bAPS (previous value)) ≧ predetermined change amount dAPS-L. If YES, the process proceeds to step S106, the operation of the compression pressure reducing means 17 is stopped, fuel injection is permitted, fuel injection by the fuel injection valve 29 is started, and combustion is started. On the other hand, if the determinations in steps S105 and S108 are both NO, the process proceeds to step S109, where the compression pressure reducing means 17 is activated and fuel injection is prohibited.

In step S107, the accelerator opening APS read this time is replaced with the previous value bAPS. Then return.
If it is determined in step S103 that the engine rotational speed NE is equal to or greater than the predetermined value NE-L, the process proceeds to step S110, where the operation of the compression pressure reducing means 17 is stopped, fuel injection is permitted, and the fuel injection valve 29 Starts fuel injection and starts combustion.

  For example, when the driver depresses the accelerator pedal while the motor is running, when the accelerator opening APS is large, the driver is requesting a large driving force. The driver's required driving force is not only the driving force of the motor / generator 3, and when a request for starting the engine 1 is generated, the torque request to the engine 1 after starting is expected to be large. In this case, if it takes a long time to start, the driving force may be insufficient. Further, when the accelerator opening change amount is large, the driver wants to immediately obtain the driving force. At this time, if it takes a long time to start the engine, there is a possibility that an acceleration failure may occur.

  On the other hand, in general, it takes time for an engine to become combustible even after cranking is started. For this reason, even if fuel is injected simultaneously with the start of cranking, there is a possibility that exhaust deterioration or torque variation may occur due to fuel failure.

  According to this embodiment, whether or not combustion is possible during cranking is determined, and the compression pressure reduction means 17 is operated until fuel is available even when the accelerator opening and the accelerator opening change amount are equal to or greater than a predetermined value. Therefore, the vibration of the engine is suppressed and the fuel injection is prohibited, so that it is possible to avoid the deterioration of exhaust and the variation of torque due to the fuel failure. In addition, since the operation of the compression pressure reducing means 17 is immediately stopped and the fuel injection is started after the combustion becomes possible, insufficient driving force and poor acceleration can be avoided, and the driver's uncomfortable feeling can be eliminated.

  In the above embodiment, the example of determining whether combustion is possible using the cooling water temperature TW has been described. However, whether fuel is possible is determined using at least one of the cooling water temperature TW, the intake air temperature TA, the intake pressure PA, and the fuel pressure PF. can do. FIGS. 7B to 7D are characteristic maps for determining fuel availability based on the intake air temperature TA, the intake pressure PA, and the fuel pressure PF when the compression pressure reducing unit 17 is not operating. The fuel pressure PF is for an engine-driven fuel pump.

  When the compression pressure reducing means 17 is a means capable of continuously changing the compression pressure, such as the continuously variable type in the intake valve characteristic varying means 36, the characteristic maps shown in FIGS. 8A to 8D are used. Further, whether or not combustion is possible may be determined from the relationship between the operation amount of the compression pressure reducing means 17 and the cooling water temperature TW, the intake air temperature TA, the intake air pressure PA, or the fuel pressure PF, respectively.

  Further, some continuously variable compression pressure reducing means 17 takes time to operate due to an operating mechanism or the like, and the compression pressure cannot be immediately returned to the normal state even after the operation is finished. is there. In this case, when determining whether combustion is possible using the characteristic maps shown in FIGS. 7A to 7D, the accuracy of determining whether combustion is possible is improved by considering the operation amount of the compression pressure reducing means 17. That is, the larger the operation amount of the compression pressure reducing means 17 (the lower the effective compression ratio), the more the boundary position of the characteristic maps in FIGS. 7A to 7D is corrected upward.

  In the above description, an example in which the present invention is applied to a one-motor hybrid vehicle is shown, but the present invention is not limited to this. The present invention is also applicable to a two-motor hybrid vehicle shown in FIG. 9 and an engine vehicle equipped with an engine equipped with a starter motor 51 shown in FIG. In the two-motor hybrid vehicle shown in FIG. 9, for example, the first motor / generator 3a is used for driving the vehicle, the second motor / generator 3b is used for starting the engine, and the second motor / generator 3b and the engine 1 are connected. The engine 1 is cranked in conjunction with the belt 41. In FIG. 9, 6b and 9b are an inverter and a motor controller for the second motor / generator 3b.

The block diagram which shows an example of the power train of the hybrid vehicle of 1 motor system to which this invention is applied. The system block diagram of a hybrid vehicle same as the above. The schematic block diagram which shows an example of the engine of a hybrid vehicle same as the above. The figure which shows the effect | action for every different compression pressure reduction means in an engine same as the above. The schematic block diagram which shows an example of the engine provided with the decompression apparatus as a compression pressure reduction means. The flowchart explaining the control action at the time of engine starting which concerns on one Embodiment of this invention. The figure which shows each characteristic map in the case of judging combustion possibility from cooling water temperature, intake air temperature, intake pressure, and fuel pressure. The figure which shows each characteristic map in the case of judging combustion possibility from the relationship between the operation amount of a compression pressure reduction means, cooling water temperature, intake air temperature, intake air pressure, and fuel pressure. 1 is a block diagram showing an example of a power train of a two-motor hybrid vehicle to which the present invention can be applied. The block diagram which shows an example of the power train of the engine vehicle which can apply this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 3 Motor generator 8 Engine controller 9 Motor controller 10 Hybrid controller 11 Rotational speed sensor 12 Acceleration opening degree sensor 13 Water temperature sensor 14 Intake temperature sensor 15 Intake pressure sensor 16 Fuel pressure sensor 17 Compression pressure reduction means 34 Throttle valve 35 Intake shut-off valve 36 Intake valve characteristic variable means 37 Decompression device

Claims (6)

In an engine provided with a compression pressure reducing means that operates at the start and reduces the compression pressure in the cylinder,
Combustion possibility determination means for determining whether combustion in the cylinder is possible;
Torque request status determination means for determining the torque request status for the prime mover including the engine;
With
When the combustion possibility determination means determines that combustion is possible and the torque request status determination means determines that a predetermined condition is satisfied with respect to the torque request status to the prime mover, the engine speed is within the operating range of the compression pressure reduction means. Even so, the engine start control device is characterized in that the operation of the compression pressure reducing means is stopped and fuel injection is started.   2. The engine start control device according to claim 1, wherein the predetermined condition is that a torque request value to the prime mover is a predetermined value or more, or a change amount of the torque request value to the prime mover is a predetermined value or more. .   The engine start control device according to claim 2, wherein the torque request value for the prime mover is estimated based on an accelerator opening.   The engine start control device according to claim 2, wherein the change amount of the torque request value to the prime mover is estimated based on the change amount of the accelerator opening.   The engine according to any one of claims 1 to 4, wherein the combustion possibility determining means determines whether combustion is possible based on at least one of fuel pressure, cooling water temperature, intake air temperature, and intake air pressure. Start control device. When starting an engine provided with a compression pressure reducing means that operates at the start to reduce the compression pressure in the cylinder,
It is determined whether combustion in the cylinder is possible or not, and a torque request status for a prime mover including an engine is determined. When combustion is possible and the torque requirement status for the prime mover satisfies a predetermined condition, the engine rotational speed is An engine start control method characterized in that the operation of the compression pressure reduction means is stopped and fuel injection is started even in the operation region of the pressure reduction means.

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