JP5059043B2 - Engine stop / start control device - Google Patents

Description

  The present invention relates to an engine stop / start control device.

  2. Description of the Related Art Conventionally, there is known an engine control system having a so-called idle stop function that detects an operation for stopping or starting such as an accelerator operation or a brake operation to automatically stop and restart an engine. By this idle stop control, effects such as engine fuel consumption reduction are achieved.

  Various techniques are provided in the idle stop control. For example, at the time of restart after automatic engine stop, there is one that changes the engine start mode based on the engine rotation speed at the time of the start request (see, for example, Patent Document 1). In the automatic stop / restart control of the engine disclosed in Patent Document 1, when the engine is automatically restarted, the engine is started by a starter when the engine rotation speed at the time of the start request is lower than the threshold, and is larger than the threshold The engine is started by restarting the fuel supply without operating the starter. Thereby, the operation frequency of the starter is reduced.

  In Patent Document 1, a threshold value for determining whether or not to operate the starter when the engine is restarted is determined by the engine warm-up state, the operating state of the auxiliary machine, and the load state of the generator. That is, the same threshold value is set according to the decrease rate of the engine rotation speed, and the threshold value is increased as the decrease rate of the engine rotation speed increases (for example, as the engine coolant temperature decreases).

JP 2002-221058 A

  There is a time delay from when the engine start request is made to when the engine rotation speed starts to increase due to the start of combustion, and the length of the delay time may vary depending on the engine operating state. In this case, in the period from the engine start request until the engine starts to increase in rotation, even if the engine rotation speed decreases at the same rate, the amount of decrease in the engine rotation speed may vary depending on the length of the delay time. It is done. Therefore, when the necessity of the starter is determined based on the engine rotation speed at the time of the engine start request, the engine rotation speed and the necessity of the starter at the time of engine restart are changed because the amount of decrease in the engine rotation speed thereafter fluctuates. Depending on the relationship with the threshold value for determination, it is conceivable that the starter is operated even if the engine can be started by combustion. On the other hand, there is a concern that the starter will not be operated even though the engine cannot be started by combustion. In particular, when the number of starter operations increases, there is a concern that power consumption due to starter operation increases and wear of the starter is promoted.

  The present invention has been made to solve the above-described problems, and can appropriately determine whether or not the engine starter is required to operate, and thus suppresses inconvenience caused by driving the starter when it is not necessary. It is a main object of the present invention to provide an engine stop / start control device capable of performing the above.

  The present invention employs the following means in order to solve the above problems.

The present invention is applied to an engine including a starter that applies initial rotation to an output shaft of the engine, and automatically stops the engine when a predetermined automatic stop condition is satisfied, and performs a predetermined start during the automatic stop of the engine. The present invention relates to an engine stop / start control device that automatically restarts the engine when a condition is satisfied. The first configuration includes position detection means for detecting the rotation position of the output shaft, rotation speed detection means for detecting the rotation speed of the engine, and rotation detected by the position detection means when the engine is requested to be restarted. A determination value setting means for setting a necessity determination value as an engine rotation speed for determining whether or not the starter needs to be driven based on the position, and the rotation speed detection when there is a restart request for the engine. The engine is started by the starter based on a comparison result between the engine rotation speed detected by the means and the necessity determination value set by the determination value setting means, or the engine is controlled by resuming combustion control of the engine. Start control means for starting the motor.

  In the engine automatic stop / restart control, when the engine is restarted before the engine speed reaches zero, the starter is driven when the engine is restarted according to the level of the engine speed at the time of the restart request. There are things that determine whether or not it is necessary. On the other hand, there is a delay time from when the engine restart is requested until the engine rotation speed starts to increase due to combustion of the engine, and the engine rotation speed may fall during the delay time. Therefore, the rotational speed determination value (necessity determination value) for determining the start mode at the time of the restart request needs to be set to reflect the drop in the engine rotational speed during the delay time.

  Here, it is conceivable that the delay time differs depending on the rotational position (crank angle) of the engine output shaft when the engine is restarted. This is because in a cylinder in which combustion is performed after a request for restarting the engine, if the crank angle at the time of the request is different, the length of the period from the start request to the start of combustion is different.

  In view of this point, in the present invention, based on the crank angle at the time of engine restart, a determination value (necessity determination value) of the engine rotation speed for determining whether or not to drive the starter at the time of engine restart is set. To do. Thereby, in setting the same judgment value, it is possible to appropriately reflect the drop in the engine rotation speed after the restart request, and the starting mode at the time of engine restart depends on the engine rotation speed at the time of restart. It can be determined appropriately. Therefore, the starting device can be driven when necessary, and inconveniences caused by driving the starting device when not necessary can be suppressed.

  Here, when the engine is composed of multiple cylinders, the cylinder for which the rotational position is to be detected is preferably the first combustion cylinder after the engine restart request, but it may be the second or later combustion cylinder. Further, the rotational position of the combustion cylinder may be acquired by detecting the rotational position of a cylinder different from the combustion cylinder by the position detection means.

When considering the fluctuation of the delay time from the engine restart request to the start of combustion in the necessity determination value, it is preferable to consider not only the deviation of the start point of the delay time but also the deviation of the end point. In view of this point, the second configuration is such that the determination value setting means has a predetermined compression angle position from the rotational position detected by the position detection means at the time of the request in the combustion cylinder after the engine restart request. The necessity determination value is set based on the rotation angle. According to this configuration, the delay time can be accurately determined even when the end points in the delay time are different. Accordingly, it is possible to accurately reflect the drop in the engine speed after the restart request in the necessity determination value.

  Here, the predetermined compression angle position is, for example, a compression top dead center when the fuel injection mode is a direct injection type engine, and the ignition timing (for example, a predetermined angle from the compression top dead center when the fuel injection mode is a port injection type engine). Corner position). Regarding the necessity determination value, the necessity determination value may be increased as the rotation angle from the rotation position at the time of the engine restart request to the predetermined compression angle position is larger.

The amount of decrease in engine rotation speed (in the delay time) from the engine restart request until the engine rotation speed starts to increase due to the start of combustion has a correlation with other parameters other than the length of the delay time. Therefore, in order to accurately reflect the decrease in the engine speed after the restart request in the necessity determination value, for example, as in the third configuration , the determination value setting means includes the rotation position, the engine The necessity determination value may be set based on the compression load of the cylinder at the time of a restart request. When the engine is restarted, for example, if the in-cylinder air amount is different, the compression load of the cylinder changes. This is because the rate of decrease in engine speed increases as the compression load on the cylinder increases, and as a result, the amount of decrease in engine speed increases. That is, it is preferable to increase the necessity determination value as the compression load of the cylinder increases. Here, the compression load of the cylinder may be estimated based on, for example, the throttle valve opening (throttle opening) or the intake pipe pressure.

Further, as in the fourth configuration , the determination value setting means may set the necessity determination value based on the rotational position and engine friction at the time of the engine restart request. When the engine is restarted, if the engine friction loss (engine friction) is small, the rate of decrease in the engine speed decreases. As a result, the amount of decrease in the engine speed decreases, whereas if the engine friction is large, the engine speed decreases. As a result, the amount of decrease in engine rotation speed increases. Therefore, the necessity determination value may be increased as the engine friction increases.

Further, as in the fifth configuration , the determination value setting means may set the necessity determination value based on the rotational position and the rotational load of the output shaft when the engine is requested to be restarted. This is because, when the engine is restarted, the decrease rate of the engine rotation speed increases as the rotation load of the engine output shaft increases, and as a result, the amount of decrease in the engine rotation speed increases. That is, it is preferable to increase the necessity determination value as the rotational load of the output shaft increases. Here, the rotational load of the output shaft includes, for example, a power generation load in a power generation device and a driving load such as an air conditioner.

The block diagram which shows the whole engine control system outline. The time chart which shows transition of the engine speed during idle stop control execution. The schematic diagram which shows the relationship between the crank angle CA at the time of engine starting request | requirement in the first combustion cylinder after engine restart, and ignition timing. The time chart which shows transition of an engine speed when an engine is restarted before an engine speed becomes zero. The flowchart which shows the process sequence about engine restart control. The figure which shows the specific example at the time of setting starter necessity determination value NETH.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine. In the control system, fuel injection amount control, ignition timing control, idle stop control, and the like are performed with an electronic control unit (hereinafter referred to as ECU) as a center. FIG. 1 is a block diagram showing an overall outline of the engine control system.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11 (intake passage), and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. . A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15.

  A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The air-fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 24 (exhaust passage) by the opening operation of the exhaust valve 22.

  A spark plug 27 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 27 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  In this system, various auxiliary machines such as a starter 37, an AC generator 39, and an air conditioner (air conditioner) 25 are provided. The starter 37 is electrically connected to the battery 38, starts cranking by starting power supply from the battery 38 based on a command signal from the ECU 40, and starts the engine 10. The AC generator 39 induces an AC voltage as the crankshaft 35 as the output shaft of the engine 10 rotates. In the air conditioner 25, when the air conditioner switch is turned on, a compressor (not shown) is driven by the engine 10, thereby air-conditioning the vehicle interior.

  In addition, in this system, the coolant temperature sensor 34 for detecting the coolant temperature TW and the crank angle signal of the crankshaft 35 by outputting a rectangular crank angle signal at every predetermined crank angle of the engine 20 (for example, at a cycle of 30 ° CA). A crank angle sensor 36 that detects a rotational position (crank angle), a vehicle speed sensor 32 that detects a vehicle speed, and the like are attached. Signals from various sensors that detect the operating state of the engine 10 such as the coolant temperature TW from the coolant temperature sensor 34, the engine rotational speed NE from the crank angle sensor 36, the vehicle speed V from the vehicle speed sensor 32, and the like are transmitted from the electronic control unit 40 ( Hereinafter, it is input to the ECU 40).

  As is well known, the ECU 40 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine operation state can be changed each time. In response, various controls of the engine 10 are performed. That is, the microcomputer 41 of the ECU 40 inputs detection signals from the various sensors described above, calculates the fuel injection amount and ignition timing based on the various detection signals, and drives the fuel injection valve 19 and the ignition device. Control or perform idle stop control.

  Regarding idle stop control, the microcomputer 41 automatically stops the engine 10 by stopping fuel injection and ignition when a predetermined engine stop condition is satisfied. When a predetermined engine start condition is satisfied while the engine is stopped, the engine 10 is initially rotated by cranking by the starter 37, and fuel injection and ignition are restarted to automatically restart the engine 10. . Here, as the engine stop condition, for example, the accelerator is off, the brake is on, and the vehicle speed is equal to or lower than a predetermined vehicle speed (for example, 20 km / h or lower). Further, as engine start conditions, for example, the accelerator is off, the brake is off, and the like.

  In this embodiment, idle stop control is performed not only when the vehicle is stopped but also when the vehicle is decelerating. Specifically, for example, when the brake is depressed and the fuel cut control is shifted during medium / high speed traveling, the vehicle gradually decelerates as the fuel supply is stopped. Then, the engine 10 is automatically stopped on the condition that the vehicle speed is equal to or lower than the idle stop permission vehicle speed VIS, the brake is on, and the like.

  Here, in the idle stop control, after the engine 10 is requested to stop, the engine 10 may be restarted before the engine 10 is completely stopped (before the engine speed NE becomes zero). is there. In particular, in a vehicle that performs idle stop control while the vehicle is decelerating, the engine can be automatically stopped and restarted before the engine speed NE becomes zero, compared to a vehicle that performs the control only while the vehicle is stopped. It is thought that the nature becomes high. Therefore, in the present system, when the engine is restarted, the start mode of the engine 10 is determined according to the engine speed NE at the time of restart.

  Specifically, when the engine speed NE at the time of the start request of the engine 10 is smaller than a predetermined value (starter necessity determination value NETH), the starter 37 is driven to assist the rotation of the crankshaft 35. . On the other hand, when the engine speed NE at the time of the start request is equal to or higher than the starter necessity determination value NETH, the starter 37 is not operated, and the engine is started by restarting the fuel supply (by self-recovery). Thereby, the operation frequency of the starter 37 is reduced.

  Regarding the starter necessity determination value NETH, in this embodiment, in view of the fact that there is a time delay from when the engine 10 is requested to start until the engine speed actually turns to the increase side, the engine rotation occurring at that delay time The starter necessity determination value NETH is set in consideration of the speed reduction amount (rotational drop amount ΔNE). That is, as shown in FIG. 2, when a start request for the engine 10 is made at a timing t11 before the engine rotation speed NE becomes zero after the stop request for the engine 10, the fuel supply is resumed along with the start request. However, the engine speed NE continues to decrease until the first combustion (first explosion). Therefore, the engine speed NE drops during the period TA from the engine start request to the first explosion. That is, after the engine restart request is made, the engine rotation speed decreases by the rotation drop amount ΔNE.

  In view of this point, in the present embodiment, a value obtained by adding the rotation drop amount ΔNE to the lower limit value NELW of the engine rotation speed NE that can be started by restarting the fuel supply (without the operation of the starter 37) is determined as to whether the starter is necessary. The determination value is set to NETH. Then, the necessity of the starter 37 for starting the engine is determined by comparing the engine rotational speed NE at the time of starting the engine with the starter necessity determination value NETH.

  Here, considering that the starter necessity determination value NETH is set in consideration of the rotation drop amount ΔNE, if the fluctuation of the rotation drop amount ΔNE is not properly reflected, the engine is started in an appropriate start mode. May not be implemented. In other words, the starter 37 may start the engine even though the starter 37 is not required to operate, and conversely, the starter 37 may not be operated even if the self-recovery cannot start the engine. Conceivable.

  The inventors pay attention to the fact that the delay time TA from when the engine 10 is restarted to when the engine speed NE starts to increase due to the start of combustion can be one of the parameters of the fluctuation factor of the rotational drop amount ΔNE. did. Further, the length of the delay time is from the crank angle when the engine restart is requested to the first ignition timing of the cylinder in the first combustion cylinder after the engine 10 is restarted (the cylinder where the first explosion is performed). It was noted that this is indicated by the rotation angle of the crankshaft 35. In addition, when the ignition timing at each engine restart is constant or the deviation is small, it is noted that the length of the delay time is indicated by the crank angle when the engine restart request is made.

  Therefore, in this embodiment, the starter necessity determination value NETH is set based on the crank angle at the time of the engine restart request. Specifically, the crank angle CA at the time of engine start request is detected for the first combustion cylinder after engine restart, and the starter necessity determination value NETH is increased as the crank angle CA is larger (ΔNE is larger). is doing.

  Here, the first combustion cylinder after engine restart is a cylinder in which fuel injection is enabled for the first time after an engine restart request. For example, the crank angle CA at the time of engine restart request is a predetermined value before intake top dead center. A cylinder that is within a rotation angle.

  The setting of the starter necessity determination value NETH will be described in detail below with reference to FIGS.

  FIG. 3 is a schematic diagram showing the relationship between the crank angle CA and the ignition timing when the engine 10 is requested to start for the first combustion cylinder after engine restart. In the present embodiment, the first ignition timing in the first combustion cylinder after the engine restart is set to a predetermined timing CA3.

  In FIG. 3, a cylinder whose crank angle CA at the time of an engine restart request is in the injectable period TX (see FIG. 3) is a cylinder in which combustion is performed first after the engine restart. In the same cylinder, when the crank angle CA at the time of the engine restart request is CA1, the rotation angle Δθstart of the crankshaft 35 is Δθ1 from the crank angle CA1 to the ignition timing CA3. On the other hand, when the crank angle CA at the time of the engine restart request is CA2 which is retarded from CA1, the rotation angle Δθstart from the crank angle CA2 to the ignition timing CA3 is Δθ2 which is smaller than Δθ1. That is, as the crank angle CA at the time of the restart request of the engine 10 is on the retard side, the time to the ignition timing CA3 is short. Therefore, if the decrease speed of the engine rotation speed NE is the same, the crank angle CA is on the retard side. The rotation drop amount ΔNE at the delay time becomes small.

  Next, the relationship between the rotation angle until the ignition timing and the rotation drop amount ΔNE will be described. FIG. 4 is a time chart showing the transition of the engine speed when the engine is restarted before the engine speed becomes zero. In FIG. 4, the alternate long and short dash line indicates the case where the crank angle at the time of engine restart is CA1 for the first combustion cylinder after engine restart, and the solid line indicates the case of CA2 (see FIG. 3 for CA1 and CA2). . In FIG. 4, it is assumed that the engine stop condition is that the accelerator is turned off, and the engine restart condition is that the accelerator is turned on. In FIG. 4, it is assumed that the engine speed decreases at the same rate.

  In FIG. 4, consider a case where the engine restart request is made at a timing t21 before the vehicle speed V and the engine rotational speed NE decrease due to the engine stop request and the engine rotational speed NE becomes zero. In FIG. 4, it is assumed that the ignition timing is CA3. At this time, when the crank angle CA at the timing t21 is CA1, the time until the ignition timing CA3 is long. Therefore, the engine rotational speed NE is increased before ignition is performed (until the engine rotational speed NE starts to increase). A large drop occurs, and the rotation drop amount is ΔNE1. On the other hand, if the crank angle CA at the timing t21 is CA2 that is retarded from the CA1, the time to the ignition timing CA3 is shorter than that at the time CA1, so the rate of decrease in the engine speed NE is the same. For example, the drop in the engine speed NE is small, and the rotation drop amount is ΔNE2 which is smaller than ΔNE1.

  Therefore, in the present embodiment, the starter necessity determination value NETH is made smaller as the crank angle CA at the time of the first combustion cylinder after the engine restart request is smaller. Specifically, for example, a map in which the crank angle is associated with the starter necessity determination value NETH is stored in advance in the ROM, and the starter corresponding to the crank angle CA at the time of the first combustion cylinder after the engine restart request is requested. The necessity determination value NETH is calculated from the map each time.

  FIG. 5 is a flowchart showing a processing procedure for engine restart control. This process is repeatedly executed by the ECU 40 at a predetermined cycle.

  In FIG. 5, first, in step S11, it is determined whether or not the engine 10 has been automatically stopped. In a succeeding step S12, it is determined whether or not an engine start condition is satisfied. If an affirmative determination is made in step S11 and step S12, the process proceeds to steps S13 and S14.

  In step S13, the first combustion cylinder after engine restart is specified based on the crank angle CA detected by the crank angle sensor 36 at the time of engine restart request. In step S14, the crank angle CA at the time of engine restart request in the identified combustion cylinder, the engine coolant temperature TW detected by the coolant temperature sensor 34, and the driving / non-driving state of the air conditioner 25 are acquired. Thereafter, in step S15, a starter necessity determination value NETH is set from these acquired values.

  In setting the starter necessity determination value NETH, in this embodiment, in addition to the crank angle CA at the time of engine restart request in the first combustion cylinder after engine restart, the engine friction at the time of start request and the driving state of the air conditioner 25 are set. Based on this, a starter necessity determination value NETH is set. The reasons are as follows.

(1) Engine friction Even when engine warm-up is complete at the time of cold start, engine friction changes depending on the vehicle running state, outside air environment, etc., for example, when engine cooling water temperature TW is low and engine oil viscosity is high, Friction loss at each of the 10 sliding portions increases (engine friction increases). Therefore, it is conceivable that the amount of decrease in the engine rotation speed NE changes due to friction loss in the delay time from when the engine restart request is made until the engine rotation speed NE starts to increase. In other words, the greater the engine friction (the lower the engine coolant temperature TW), the greater the rotational drop amount ΔNE. Therefore, in this embodiment, the starter necessity determination value NETH is increased as the engine coolant temperature TW is lower.

  Note that any parameter that can detect engine friction is not limited to the engine coolant temperature TW, and may be the temperature of the engine oil circulating in the engine 10 (engine oil temperature), for example.

(2) Driving / non-driving of the air conditioner 25 When the air conditioner switch is turned on and the air conditioner 25 is in a driving state, the rotation load of the crankshaft 35 is increased by driving the air conditioner 25. For this reason, in the delay time from when the engine restart request is made until the engine rotational speed NE starts to increase, it is conceivable that the amount of decrease in the engine rotational speed NE changes due to the rotational load. That is, when the air conditioner 25 is in the driving state, the rotation drop amount ΔNE is larger than that in the non-driving state. Therefore, in the present embodiment, the starter necessity determination value NETH is made larger in the driving state of the air conditioner 25 than in the non-driving state.

  FIG. 6 shows a specific example when the starter necessity determination value NETH is set in the present embodiment. In FIG. 6, the ECU 40 stores a map showing the relationship among the crank angle CA, the engine coolant temperature TW, the driving state of the air conditioner 25, and the starter necessity determination value NETH. Then, when the acquired value of each parameter is input in step S14 of FIG. 5, the starter necessity determination value NETH at the time of the current engine restart is set in step S15 of the same figure. .

  Returning to the description of FIG. 5, in the subsequent step S <b> 16, it is determined whether the engine speed NE at the time of the engine restart request is equal to or higher than the starter necessity determination value NETH. When the engine speed NE is less than the starter necessity determination value NETH, it is determined that cranking by the starter 37 is necessary to start the engine 10, and power is supplied from the battery 38 to the starter 37. The starter 37 is driven. On the other hand, when the engine speed NE is equal to or higher than the starter necessity determination value NETH, the starter 37 is not driven and the engine 10 is started by restarting the fuel supply. In the present embodiment, the fuel supply is resumed when the engine is started by the starter 37 in step S17.

  According to the embodiment described in detail above, the following excellent effects are obtained.

  Since the starter necessity determination value NETH is calculated each time based on the crank angle CA at the time of the engine restart request, when the starter necessity determination value NETH is set, the drop in the engine speed NE after the engine restart request ( The rotational drop amount ΔNE) can be suitably reflected. Thereby, it is possible to appropriately determine whether the start mode at the time of engine restart is performed by the starter 37 or without the starter 37 being driven according to the engine speed NE at the time of engine restart. Therefore, inconvenience due to the starter 37 being driven when not necessary can be suppressed. That is, by driving the starter 37 only when the starter 37 needs to be driven, the drive frequency of the starter 37 can be suppressed. As a result, the power consumption of the starter 37 can be reduced and the starter 37 can be prevented from being worn. Can be planned.

  Since the starter necessity determination value NETH is increased as the engine coolant temperature TW is lower, the starting form is determined in consideration of the drop in the engine speed NE due to the difference in friction loss at each sliding portion of the engine 10. Can do.

  Since the starter necessity determination value NETH is set to be larger in the driving state of the air conditioner 25 than in the non-driving state, the starting mode is determined in consideration of the drop in the engine speed NE due to the difference in the rotational load of the crankshaft 35. Can do. In particular, since the rotational load of the crankshaft 35 due to the driving of the air conditioner 25 is relatively large, the start mode can be suitably determined by considering the air conditioner driving.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the first combustion cylinder after the engine restart request, instead of setting the starter necessity determination value NETH based on the crank angle CA at the time of the engine restart request, from the crank angle CA at the time of the engine start request to the ignition timing CA3 The starter necessity determination value NETH is set based on the rotation angle Δθstart. The delay time TA from when the engine restart request is made to when the engine speed NE starts to increase due to the start of combustion varies not only according to the start point (when the engine restart is requested) but also according to the end point. In this case, the starter necessity determination value NETH may be increased as the rotation angle Δθstart increases. In particular, when the ignition timing is not constant, the starter necessity determination value NETH may be set based on the rotation angle Δθstart.

  Further, the starter necessity determination value NETH is set based on the compression load of the cylinder when the engine is restarted. This is because the greater the compression load of the cylinder, the slower the movement of the piston, and the lowering rate of the engine rotation speed NE becomes larger at the delay time TA. Specifically, the starter necessity determination value NETH is increased as the compression load of the cylinder increases. Here, the compression load of the cylinder may be estimated based on the throttle opening detected by the throttle opening sensor or the intake pipe pressure detected by the intake pipe pressure sensor 17. Specifically, the larger the throttle opening, the greater the amount of air charged into the cylinder (in-cylinder air amount), and the greater the compression load of the cylinder. It is better to raise the neth. Further, the higher the intake pipe pressure is, the more air is charged in the cylinder, and the compression load of the cylinder increases. Therefore, the higher the intake pipe pressure, the higher the starter necessity determination value NETH may be.

  The rotation load of the crankshaft 35 is assumed to be generated by the driving of the air conditioner 25, and the starter necessity determination value NETH is set based on the driving state of the air conditioner 25. Instead of or in addition to 25, an alternator 39 may be used, and the starter necessity determination value NETH may be set based on the drive state of the alternator 39.

  Further, the starter necessity determination value NETH is set based on the engine speed NE. The magnitude of the shaft torque of the engine 10 differs depending on the difference in the engine speed NE, and the shaft torque increases as the engine speed NE increases. Therefore, as the engine speed NE at the time of the engine restart request increases, the amount of rotation drop ΔNE at the delay time TA increases. Therefore, the starter necessity determination value NETH may be increased as the engine speed NE increases.

  The starter necessity determination value NETH is set using, for example, a map as shown in FIG. 6, but may be configured using mathematical formulas.

  Although the explanation has been made on the assumption that the engine speed NE starts to increase due to combustion in the first combustion cylinder after engine restart, the engine speed NE does not increase due to combustion in the first combustion cylinder after engine restart. In consideration of this, the starter necessity determination value NETH may be set based on the crank angle CA at the time of engine restart, targeting a cylinder that performs combustion for the second time after engine restart or thereafter.

  The present invention may be applied to a vehicle having a configuration in which a lockup clutch is provided between the engine 10 and the transmission and the connection state between the engine 10 and the transmission is switched by connecting / releasing the lockup clutch. In such a configuration, when the vehicle is decelerated due to the accelerator being off, the lockup clutch is engaged to directly connect the crankshaft 35 of the engine 10 and the transmission, and the fuel supply of the engine 10 is stopped. In other words, fuel consumption is reduced by maintaining the rotation of the engine 10 by driving from the crankshaft 35 side. In this configuration, when an engine restart request is made before the engine rotation speed NE becomes zero after the engine automatic stop request is made, the engine rotation speed NE is increased from the restart request until the engine rotation speed NE starts to increase. In the delay time TA, the decrease rate of the engine rotation speed NE is moderate, so that the decrease in the engine rotation speed NE is small, but the rotation drop amount ΔNE is generated as described above. Therefore, the same effect as described above can be obtained by applying the present invention to this configuration.

  However, it is more preferable to apply the present invention to a configuration in which a lockup clutch is not provided between the engine 10 and the transmission, as in the configuration described as the above embodiment. In a configuration without a lock-up clutch, if an engine restart request is made before the engine speed NE becomes zero after an engine automatic stop request, the rotational drop amount ΔNE at the delay time TA is This is because the first combustion cylinder is likely to increase in accordance with the difference in crank angle when the engine restart is requested.

  The fuel injection system has been described for the port type engine 10, but the present invention may be applied to a direct injection type engine or a diesel engine.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 25 ... Air conditioner, 34 ... Cooling water temperature sensor, 35 ... Crankshaft (output shaft), 36 ... Crank angle sensor (position detection means, rotation speed detection means), 37 ... Starter (starter), 39 ... AC Generator, 40 ... ECU (position detecting means, rotational speed detecting means, determination value setting means, start control means).

Claims (4)

Applied to an engine having a starting device for applying an initial rotation to the output shaft of the engine;
An engine stop / start control device that automatically stops the engine when a predetermined automatic stop condition is satisfied, and automatically restarts the engine when a predetermined start condition is satisfied during the automatic stop of the engine,
Position detecting means for detecting the rotational position of the output shaft;
Rotation speed detection means for detecting the rotation speed of the engine;
In order to determine whether or not the starter needs to be driven based on a rotation angle from a rotation position detected by the position detecting means to a predetermined compression angle position in the combustion cylinder after the engine restart request is made Determination value setting means for setting a necessity determination value as the engine rotation speed of
When there is a request for restarting the engine, based on a comparison result between the engine rotational speed detected by the rotational speed detection means and the necessity determination value set by the determination value setting means, the engine starts the engine. Or start control means for starting the engine by resuming combustion control of the engine,
An engine stop / start control device comprising: The engine stop / start control apparatus according to claim 1 , wherein the determination value setting means sets the necessity determination value based on the rotational position and a compression load of a cylinder when the engine is requested to be restarted. The engine stop / start control apparatus according to claim 1 or 2 , wherein the determination value setting means sets the necessity determination value based on the rotational position and engine friction when the engine is requested to be restarted. The determination value setting means, wherein a rotational position, according to any one of claims 1 to 3 sets the necessity determination value based on the rotational load of the output shaft at the time of restart request of the engine Engine stop start control device.

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