JP3463739B2 - Engine control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the engine output with good responsiveness while reducing vibration by decompression-operating a decompressor at the time of cranking, and releasing the decompression-operation when the release timing comes. SOLUTION: An engine 20 is provided with a variable valve timing device (VVT) 24 interposed between a crankshaft 21 and a camshaft. The VVT 24 functions as a decompressor producing a cylinder internal pressure reducing effect or decompression effect. A hybrid car is provided with an electronic control unit 80 for controlling the respective actuations of a motor 10, the electronic throttle device 23 of the engine 20, the VVT 24, a fuel injection valve 25, a transmission 40 and a clutch 70. At the time of cranking, the decompression operation is performed, and when the release timing variably set according to a required engine output comes, the decompression operation is released. According to this, the vibration in cranking can be reduced, and the engine output can be quickly increased.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an engine control method, and more particularly to a method for starting an engine in a vehicle such as a hybrid vehicle that starts an engine separately from a start operation by a driver. The present invention relates to an engine control method capable of improving responsiveness to an output increase request while suppressing vibration. 2. Related Background Art A decompression device is sometimes attached to an engine from the viewpoint of facilitating starting of the engine. In other words, if the in-cylinder pressure is reduced by operating the decompression device at the time of starting the engine, the starting of the engine is facilitated and the vibration is reduced. Such a decompression device is configured as, for example, a variable valve timing device capable of changing the opening / closing timing of the intake valve, and by delaying the opening / closing timing of the intake valve by the variable valve timing device,
An in-cylinder pressure reduction effect, that is, a decompression effect is obtained. [0003] This type of decompression device is not limited to a normal vehicle using an engine as a driving source, but also a parallel hybrid vehicle using an engine and an electric motor as a driving source, and a power generator driving a generator for charging a battery. May be installed on a series hybrid vehicle equipped with an engine.
Hybrid vehicles aim to improve driving performance and extend cruising range while enjoying the advantages of electric vehicles.To reduce emissions and improve fuel efficiency, stop the engine while the vehicle is stopped or running with a motor. There are many. For the same reason, some ordinary vehicles stop the engine operation every time the vehicle stops. In this type of vehicle, starting and stopping of the engine are frequently performed, and vibrations caused by starting the engine become a problem. In particular, when the engine is started during running by the motor, the vehicle body often vibrates, giving the driver and the occupant a sense of incompatibility. Therefore, as described above, the vibration is reduced by operating the decompression device when the engine is started. [0004] An engine start request in a hybrid vehicle is generated, for example, when a driver depresses an accelerator pedal and requests acceleration of the vehicle.
As described above, when the decompression device is operated at the time of starting the engine, the vibration accompanying the engine startup can be reduced, but the engine output is reduced due to the decompression operation. conventionally,
Even when the engine is started in response to an acceleration operation request, the decompression device is continuously operated until the engine exits a low engine rotation range (resonance region of a torsional vibration system including the engine as an inertial mass). Was a factor in the decline. An object of the present invention is to provide an engine control method capable of increasing engine output with good responsiveness while reducing vibrations caused by starting the engine. An engine control method according to the present invention has a decompression device which performs a decompression operation at the time of engine cranking, and performs a decompression operation when a release time variably set according to a required engine output comes. The operation is canceled. The in-cylinder pressure is reduced by the decompression operation at the time of cranking, and the engine vibration accompanying the cranking and the vehicle body vibration are reduced. Then, the decompression operation is released at a time suitable for the required engine output, and the decrease in engine output due to the decompression operation is reduced. For example, if there is a request for acceleration operation by the driver, the required engine output increases. In this case, the decompression operation is canceled early, and after the start of the engine, the engine output increases early so that the acceleration operation request is increased. The engine output is generated according to. On the other hand, if the required engine output is small, the decompression operation is continued for a long period after the start of engine startup, and vibration is reduced. [0007] The engine control method of the present invention is preferably applied to a hybrid vehicle in which the load is shared between the engine and the electric motor. In such a hybrid vehicle, when the load increases during traveling by the motor, an engine start request may be issued. In this case, the vibration caused by the start of the engine is a particular problem. However, the vibration is reduced by the decompression operation, and the discomfort felt by the driver and the occupant is reduced. [0008] The engine control method of the present invention is applicable to an engine equipped with a decompression device including a variable valve timing device capable of changing the opening / closing timing of an intake valve. In this case, the engine is started in a state where the opening and closing timing of the intake valve is set to, for example, a predetermined timing on the most retarded side by the variable valve timing device, that is, in a decompression operation state. Next, the opening / closing timing of the intake valve changes to the advanced side at the decompression operation release timing that matches the required engine output. As a result, the vibration at the time of starting the engine is reduced, and the engine output increases with good responsiveness. Further, even after the engine start is completed, the opening / closing timing of the intake valve, and furthermore, the overlap period between the intake valve and the exhaust valve is adapted to the engine operating state, and the engine output is improved. In the present invention, preferably, the release time of the decompression operation is set in the form of a threshold value of the engine speed, and it is determined that the release time has come when the engine speed exceeds this threshold value. According to this preferred aspect, it is possible to appropriately set the release time of the decompression operation and determine the arrival of the release time. However, the release time can be set in the form of an elapsed time from the start of cranking. In the present invention, preferably, the required engine output is determined based on an accelerator opening when an engine start request is made. According to this preferred aspect, the required engine output, particularly the acceleration operation request, can be properly determined, and the engine output can be rapidly increased in accordance with the acceleration operation request. A parallel hybrid vehicle to which an engine control method according to one embodiment of the present invention is applied will be described below. As shown in FIG. 1, the parallel hybrid vehicle includes an electric motor 10 and an engine 20, and each of the motor 10 and the engine 20 constitutes a driving source for driving the vehicle. In the present embodiment, the motor 10 not only functions as a traveling drive source, but also has a function as an engine start motor. The engine 20 has a valve drive system 22 including a hydraulic lash adjuster 22a and a roller rocker arm 22b, and an electronic throttle device 23 for adjusting the engine output by changing the throttle opening. One end of the rocker arm 22b is It is arranged so as to be able to abut on the valve stem distal end surface of the intake valve 22c. The engine 20 is connected to a generator (not shown) via a power distribution device (not shown), and the power generated by the generator driven by the engine is used to charge the battery 30. The rotating shaft 11 of the motor 10 is connected to an input shaft 41 of a transmission 40 arranged downstream of the motor 10.
It is connected to. The transmission 40 includes, for example, a planetary gear transmission, a belt-type continuously variable transmission, or a combination thereof. An output shaft 42 of the transmission is connected to a driving wheel 60 of the vehicle via a speed reducer and a differential gear 50. Also, the motor rotating shaft 11
Can be connected to a crankshaft (output shaft) 21 of the engine 20 via a clutch, for example, an electromagnetic clutch 70. The engine 20 has a variable valve timing device (V) interposed between its crankshaft 21 and camshaft.
VT) 24 is provided, and the rotation phase (cam phase) of the camshaft with respect to the crankshaft can be variably adjusted by the VVT. For example, the VVT 24 includes a vane housing that rotates synchronously with the crankshaft 21 via a toothed belt, and a vane rotor that is fixed to a tip end surface of a camshaft. For example, two vanes are integrally formed on the vane rotor. . In this case, the vane housing has two vane storage chambers. Each vane accommodation chamber is divided into a retard oil chamber and an advance oil chamber by vanes accommodated therein, and each oil chamber can be connected to an oil pump via an oil control valve (OCV) 24a. I have. And OC
By controlling the power supply period to the electromagnetic solenoid of V24a, the supply and discharge of pressure oil to and from each oil chamber is controlled to change the cam phase. As shown in FIG. 4, the engine rotation fluctuation decreases as the cam phase becomes more retarded, and the rotation fluctuation decreases as the cranking speed increases. Here, the reason why the engine rotation fluctuation decreases as the cam phase is retarded is that the in-cylinder pressure decreases due to the retardation of the cam phase. In other words, the VVT 24 functions as a decompression device that has an in-cylinder pressure reducing action, that is, a decompression action. The hybrid vehicle has an electronic control unit 80 for controlling the operation of the motor 10, the electronic throttle device 23 of the engine 20, the VVT 24 and the fuel injection valve 25, the transmission 40, and the clutch 70.
have. A hybrid vehicle is equipped with accessories such as an air conditioner. Electronic control unit 8
On the input side of 0, an accelerator pedal sensor 91 for detecting an accelerator pedal position, a vehicle speed sensor 92 for detecting a vehicle speed,
Battery capacity detection unit 3 for detecting remaining capacity of battery 30
1. Various sensors such as an air conditioner switch 93 for detecting the operating state of the air conditioner and an engine speed sensor 94 for detecting the engine speed are connected. The output side of the electronic control unit 80 is connected to the electronic throttle device 23, the OCV 24a of the VVT 24 and the fuel injection valve 25, and is also connected to the motor control unit 13, the shift control unit 43, and the clutch control unit 73. . While the main switch of the hybrid vehicle is in the ON position, the electronic control unit 80 executes a “VVT control routine at the time of engine start” shown in FIG. 2 at a predetermined cycle. In this control routine, it is first determined whether an engine start request has been issued (step S).
21). Specifically, the output of the accelerator pedal sensor 91 is read, and the previous accelerator pedal sensor output read in step S21 of the previous cycle and stored in the memory of the electronic control unit 80 is read from the memory. Then, it is determined whether or not the accelerator pedal is depressed, that is, whether or not the vehicle is required to accelerate. Based on the previous and current accelerator pedal sensor outputs. In addition, the output of the battery capacity detection unit 31 is read, and it is determined based on the output of the battery capacity detection unit whether the remaining capacity of the battery 30 has fallen below a minimum allowable value, that is, whether or not battery charging has been requested. Further, the switching position of the air conditioner switch 93 is detected, and it is determined based on the air conditioner switch position whether driving of the air conditioner (more generally, accessories) has been requested. If none of the accelerating operation request, the battery charging request or the auxiliary device driving request has been issued,
It is determined that "there is no engine start request", and step S21 is performed.
Is negative (No). In this case, the execution of the present control routine in the current cycle ends without performing the substantial VVT control. In the present embodiment, immediately before the engine operation is stopped, a “VVT control routine at the time of engine stop” (not shown) is performed, and the opening / closing timing (cam phase) of the intake valve of the engine 20 becomes the most retarded. Thus, the VVT 24 operates under the control of the electronic control unit 80. Preferably, VVT24
Has a lock mechanism (not shown) that locks the vane rotor at the most retarded position with respect to the vane housing to maintain the cam phase on the most retarded side. For example, the lock mechanism includes a lock pin arranged in a lock pin hole of the vane rotor body, and a hydraulic mechanism or a spring that fits the lock pin into the lock hole of the vane housing with hydraulic or spring force when the vane rotor rotates to the most retarded position. Mechanism. Under such an operation of the VVT 24, the opening / closing timing of the intake valve is set to the most retarded side until an engine start request is issued. When any of an acceleration operation request, a battery charging request, and an accessory driving request is issued, it is determined in step S21 that "an engine start request is present". In this case, cranking of the engine is started in an engine start control routine (not shown). In the present embodiment in which the traveling motor 10 is used as an engine starting motor, an increase in motor output required for cranking is calculated in the electronic control unit 80, and the motor control unit 13 operates under the control of the electronic control unit 80. hand,
The motor drive current is increased according to the increase in the motor output. At the same time, the clutch control unit 73 operates to supply a drive current to the electromagnet of the electromagnetic clutch 70, and the clutch 7
0 is brought into contact with the motor rotating shaft 11 and the crankshaft 21.
Are linked. The motor 10 generates an output corresponding to the sum of the vehicle running load and the cranking load,
0 cranking is started. As described above, before the start of cranking, the opening / closing timing of the intake valve is set to the most retarded side. Therefore, the cranking is performed with the opening / closing timing of the intake valve set to the most retarded side. Will be performed. That is, the VVT 24 as the decompression device is in an operation state in which the opening and closing timing of the intake valve is set to the most retarded side to reduce the in-cylinder pressure at the time of starting cranking, that is, a decompression operation state. As described above, the cranking is performed in a state where the in-cylinder pressure is reduced. Therefore, the engine vibration caused by the cranking is reduced, and the vehicle vibration generated by transmitting the engine vibration to the vehicle body via the mount is also reduced. Reduce. At the start of cranking, the hybrid vehicle is in a running state by the motor 10 (except when the vehicle is stopped), and when the engine vibration or the vehicle body vibration occurs, it gives a sense of incongruity to a driver or the like. As a result, such a level of vibration that causes a feeling of strangeness does not occur. In the VVT control routine at the time of engine start shown in FIG. 2, when it is determined in step S21 that "engine start request is present", the current accelerator pedal sensor output (accelerator opening) is read (step S21). S2
2) It is determined whether or not the current accelerator opening exceeds the determination value, that is, whether or not the accelerator pedal is depressed significantly (step S23). If the result of the determination in step S23 is negative, that is, if the accelerator depression is not large, the threshold NeS representing the engine speed at which the advance operation of the VVT 24 (more generally, the release of the decompression operation) should be started is increased. It is set to the value NeH (step S24). On the other hand, when it is determined in step S23 that the accelerator pedal is large, the threshold value NeS is set to a lower value NeL (step S2).
5). Then, the output of the engine speed sensor 94 is read, and it is determined whether or not the current engine speed Ne exceeds the threshold value NeS set in step S24 or S25 (step S26). If the engine speed Ne does not exceed the threshold value NeS, the determination process of step S26 is performed again. Thereafter, when the engine speed Ne exceeds the threshold value NeS, under the control of the electronic control unit 80, pressure oil from a hydraulic pump (not shown) is supplied to the advance oil chamber (not shown) of the VVT 24 via the OCV 24a. , VVT2
4 performs the advancing operation (step S27). That is, VV
The T24 vane rotor (not shown) rotates in the cam phase advance direction with respect to the vane housing (not shown). As described above, if the accelerator pedal depression (required engine output) is large, the engine speed NeS which defines the start timing of the VVT advance operation (more generally, the decompression operation cancellation) is set to a small value NeL. Therefore, the VVT advance operation is started at an early stage, and the decrease in engine output due to the VVT retard operation is eliminated at an early stage. Therefore, after the cranking starts, the engine output increases from an early stage, and an engine output that meets the acceleration operation request is generated. On the other hand, if the accelerator depression is not large, the above-mentioned engine speed NeS is set to a large value NeH, so that the VVT advance operation is started at a late time, and the VVT advance operation is started for a long time after the cranking is started. The retard operation (in-cylinder pressure lowering state) continues, and vibration is reduced. In addition,
In the present embodiment, when there is an engine start request, only the magnitude of depression of the accelerator is determined. Therefore, when the engine is started to drive the battery charging generator or accessories by the engine, the engine output is not increased. Also, with emphasis on vibration prevention, the VVT advance operation start time (decompression operation release time) is set later. FIG. 3 illustrates changes in the VVT phase (cam phase (opening / closing timing of the intake valve)) and the like when the engine is started and VVT control is performed in response to a request for acceleration operation. In FIG. 3, when the accelerator pedal position (APS) greatly changes in the throttle opening direction as shown by the solid line in the figure due to the accelerator pedal depressing operation, it is determined that there is an acceleration operation request, and the motor output is determined in an engine start control routine (not shown). Is increased by the cranking load. As a result, cranking is started, and thereafter, the engine speed increases at an increasing rate corresponding to the increase in the motor output. Then, when the engine speed reaches the threshold value NeS (= NeL), the advance operation of the VVT 24 is started. The opening / closing timing of the intake valve is advanced by the advance operation of the VVT 24, and accordingly, the engine output increases rapidly in response to a steep acceleration operation request. On the other hand, when the accelerator pedal position (APS) changes relatively slowly in the throttle opening direction as shown by the broken line in FIG. 3, it is determined that a slow acceleration operation has been requested, and the motor output is cranked. The cranking is started with the load increased. Compared with the case where a steep acceleration operation request is issued (solid line), the engine speed threshold NeS that defines the advance operation start time (decompression operation release time) takes a large value NeH, and the advance operation start time is Δ
It is delayed by Tdec time. For this reason, the opening / closing timing of the intake valve takes a value on the most retarded side for a relatively long period from the start of cranking, and during this time, the in-cylinder pressure reduced state is maintained. As a result, the vibration at the time of starting the engine is suppressed by the in-cylinder pressure lowering action of the VVT 24. And
When the engine speed reaches a threshold value NeS (= NeH), VV
The advancing operation of T24 is started. As a result, the engine output increases relatively slowly in response to a slow acceleration operation request. The present invention is not limited to the above embodiment, but can be variously modified. For example, in the embodiment, the engine control method for advancing the VVT advance operation start time (decompression operation release time) when a steep acceleration operation request is made in the parallel hybrid vehicle has been described. Is not limited to this. For example, in a parallel-type hybrid vehicle equipped with accessories having a large driving load, the accessory drive request indicates an increase in the required engine output. In consideration of this point, the advance operation of the VVT (the release of the decompression operation) may be performed earlier when there is a request to drive the accessories. Further, in the embodiment, the VVT advance operation start timing is set in two stages according to whether the request is a steep acceleration operation request or a gentle acceleration operation request. And the VVT advance operation start timing may be set in three or more stages. In the above embodiment, a VVT (variable valve timing device) is used as a decompression device, but a decompression operation (in-cylinder pressure reduction operation).
Other decompression devices that can achieve the above may be used. Further, in the embodiment, the case where the present invention is applied to the parallel hybrid vehicle has been described. However, the present invention stops the engine operation every time the vehicle stops and starts the engine every time the vehicle starts moving from the stopped state. The present invention is also applicable to a vehicle configured to perform this operation (a so-called idle stop vehicle). In this case, for example, when the accelerator stepping degree at the time of starting is small, and therefore, the driver wants a gentle start, while delaying the decompression operation cancellation time to prevent the vibration by the decompression effect, while wanting a steep start, The decompression operation release timing is advanced to quickly increase the engine output. Further, in the above-described embodiment, the engine speed is used as a parameter for determining the decompression operation release timing. However, the present invention is not limited to this. The release time may be determined. According to the present invention, the decompression device is made to perform a decompression operation when the engine is cranked, and the decompression operation is released when a release timing variably set according to the required engine output comes. When the output is large, for example, when an acceleration operation request is made, the engine output can be quickly increased by reducing the engine output decrease due to the decompression operation while reducing the vibration at the time of cranking by the decompression operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram illustrating a parallel hybrid vehicle to which an engine control method according to an embodiment of the present invention is applied. FIG. 2 is a flowchart of a “VVT control routine when starting an engine” executed by the electronic control unit shown in FIG. 1; FIG. 3 shows a VVT phase, an engine speed, a motor output, before and after execution of a VVT control routine at the time of engine start;
It is a figure which illustrates each change of an accelerator pedal position and a vehicle speed. FIG. 4 is a diagram illustrating a relationship among a VVT phase, a cranking rotation speed, and an engine rotation fluctuation. [Description of Signs] 10 Motor 20 Engine 24 VVT 80 Electronic Control Unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F01L 13/08 F02D 13/08 A F02D 13/08 29/02 321B 29/02 321 41/06 320 41/06 320 F02N 17 / 00A F02N 17/00 B60K 6/04 ZHV (72) Inventor Taketoshi Hirata 4-2-1-1, Shimomaruko, Ota-ku, Tokyo Inside Mitsubishi Automotive Engineering Co., Ltd. (56) References JP-A-59-63327 (JP, A) JP-A-10-89097 (JP, A) JP-A-10-47123 (JP, A) JP-A-9-303188 (JP, A) JP-A-9-72266 (JP, A) JP-A-8 JP-A-135546 (JP, A) JP-A-8-28313 (JP, A) JP-A-3-50380 (JP, A) JP-A-61-159671 (JP, U) (58) Fields investigated (Int. . ^7, DB name) B60K 6/02 - 6/04 B60L 11/00 - 11/18 F02D 13/00-45/00 F02N 1/00-17/08

Claims (1)

(57) [Claim 1] When an engine is cranked, a decompression device is made to perform a decompression operation, and a release time of the decompression operation is variably set in accordance with a required engine output, and when the release time comes An engine control method, wherein the decompression operation of the decompression device is canceled.