JP4147398B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device, and more particularly to an engine control device that reduces a starting torque required for a starter motor or the like when the engine is started.
[0002]
[Related background]
For example, the present invention is applied to a vehicle with an idle stop function that automatically stops the engine temporarily for the purpose of reducing fuel consumption and emission while the vehicle is stopped due to traffic light or traffic jams (see, for example, Patent Document 1).
In the vehicle with the idle stop function described in Patent Document 1, it is assumed that the vehicle is stopped when the vehicle speed is 0 km / h, the shift position of the manual transmission is N (neutral), and the engine stop condition such as clutch connection is established. The engine is stopped when the engine is started, and then the engine is started by a starter when an engine start condition such as clutch disconnection is established.
[0003]
[Patent Document 1]
JP-A-2001-173480 [0004]
[Problems to be solved by the invention]
In a vehicle with an idle stop function that stops the engine due to waiting for traffic lights or traffic jams, the vehicle is necessarily started immediately after the engine is started, so it is necessary to complete the engine start as quickly as possible.
By the way, the engine is stopped by stopping the fuel injection, etc. At this time, the engine increases the rotational speed while gradually consuming the inertial energy of the moving part such as the crankshaft by the frictional resistance of the bearings and the compression resistance of the intake air. Decrease and stop. Since the compression resistance of the intake air is generated in each compression stroke of each cylinder, the engine is frequently stopped at a position where one of the cylinders reaches the compression stroke and the compression resistance rapidly increases. FIG. 8 is a diagram showing the distribution of the piston stop positions of the in-line four-cylinder engine. The piston of each cylinder rises from the bottom dead center, and starts compression at the point a in the figure as the intake valve is closed. However, it can be seen that the frequency at which the piston stops immediately after the start of compression is very high.
[0005]
Therefore, when cranking is started after the engine start condition is satisfied, the starter motor is required to have a large starting torque, and the rise of cranking becomes slow. In particular, when the oil viscosity decreases due to the oil temperature increase, the torque required for cranking increases as the oil lubrication performance declines, especially the cylinder liner lubrication performance declines. The engine startability deteriorated remarkably, and there was a risk that the engine could not be started in severe cases.
[0006]
An object of the present invention is to provide an engine control device that can quickly start cranking by a starter motor at the time of engine start and thereby realize good startability.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes an engine stop / restart means for stopping the engine when a predetermined stop condition is satisfied, and restarting the engine when the predetermined restart condition is satisfied; A torque absorbing means connected to the output shaft of the engine and capable of absorbing the torque of the engine, and a torque absorption control means for controlling the torque absorbing means to absorb the engine torque when the engine is stopped when the stop condition is satisfied. The torque absorption control means includes a rotation speed detection means for detecting the engine rotation speed, and absorbs the torque until the engine is stopped after the engine rotation speed becomes lower than a predetermined rotation speed.
[0008]
Therefore, when the engine is stopped as the stop condition is satisfied, the engine is stopped by the torque absorption means controlled by the torque absorption control means until the engine is stopped after the engine rotation speed becomes lower than the predetermined rotation speed. Torque is absorbed.
During normal engine stop where torque absorption is not performed, one of the cylinders often reaches the compression stroke and stops at a position where the compression resistance of the intake air has increased rapidly. Since the piston is stopped at a low position, the starting torque of the starter motor or the like is reduced when the engine is restarted as the restart condition is satisfied. As a result, even when the oil lubrication performance is lowered due to the rise in the tail oil temperature, the cranking is quickly started up with a margin, and good startability is realized.
[0009]
According to a second aspect of the present invention, in the first aspect, the torque absorption control means decreases the torque absorption amount in accordance with the decrease in the engine rotational speed detected by the rotational speed detection means.
Therefore, the engine at the time of stopping gradually decreases the inertia energy together with the engine rotation speed, and the torque absorption amount is controlled according to the inertia energy. Therefore, the frequency at which the piston stops within the target region where the compression resistance of the intake air is low. Will increase.
[0010]
According to a third aspect of the present invention, there is provided the valve timing control means for adjusting the opening / closing timing of the intake valve based on the operating state of the engine according to the first or second aspect, and the torque absorption control means is adjusted by the valve timing adjustment means. The amount of torque absorption is controlled according to the opening / closing timing of the intake valve.
Accordingly, the opening / closing timing of the intake valve is adjusted by the valve timing adjusting means, and the timing of starting the compression in the compression stroke changes together with the closing timing of the intake valve, and accordingly, the region where the compression resistance is low also varies. Here, since the torque absorption amount is controlled according to the opening / closing timing of the intake valve, the stop position of the piston is adjusted according to the change in the region where the compression resistance is low, and as a result, the control state of the intake valve is changed. Regardless, the piston can be stopped in a region where the compression resistance is low.
[0011]
According to a fourth aspect of the present invention, in the first to third aspects, the torque absorbing means is a generator driven by the output from the engine.
Accordingly, since the torque absorbing means is configured using the existing generator, an increase in the vehicle weight and an increase in manufacturing cost when a new torque absorbing means is provided can be prevented.
[0012]
A fifth aspect of the present invention includes the first circuit that connects the generator and the battery, and the second circuit that connects the generator and the variable resistor. When torque absorption is performed by means, the first circuit is shut off and the second circuit is connected, and the torque absorption amount is changed by changing the resistance value of the variable resistor.
[0013]
Therefore, when the generator is connected to the battery by the first circuit, the generator generates power as usual, and when connected to the variable resistor by the second circuit, the generator increases the generated current to absorb the engine torque. The amount of absorption is changed according to the resistance value of the variable resistor. Thus, the generator functions as torque absorbing means only by switching the connection state of the generator by the first and second circuits.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in an engine control device applied to a vehicle with an idle stop function will be described.
As shown in the overall configuration diagram of FIG. 1, the engine 1 is configured as an intake pipe injection type in-line four-cylinder gasoline engine. The intake passage 2 of the engine 1 is provided with a fuel injection valve 3 for each cylinder, and each fuel injection valve 3 is supplied with fuel from a fuel pump (not shown). Intake air is introduced into the intake passage 2 from an air cleaner (not shown), and the introduced intake air is mixed with fuel injected from the fuel injection valve 3 after the flow rate is adjusted by the throttle valve 4 driven to open and close by the motor 4a. The air-fuel mixture is introduced into the combustion chamber 5 as the intake valve is opened. Thereafter, the air-fuel mixture is ignited by the spark plug 6 at a predetermined timing, and the exhaust gas after combustion is discharged from the combustion chamber 5 into the exhaust passage 7 and is discharged outside through a catalyst and a silencer (not shown).
[0015]
A starter generator 11 (torque absorbing means, generator) is disposed on one side of the engine 1, and a pulley 12 of the starter generator 11 is connected to a crank pulley 15 of the engine 1 together with a water pump pulley 13 and an idler pulley 14. They are connected by a belt 16. The starter generator 11 functions as an alternator for power generation and also functions as a starter motor for starting the engine.
[0016]
That is, the starter generator 11 is connected to a battery 17 mounted on the vehicle, and is also connected to an electric load (not shown) such as a vehicle lamp or an air conditioner, and the belt 16 is driven by the crank pulley 15 during engine operation. Is rotated together with the water pump pulley 13 to generate electric power for charging the battery 17 and power consumption by the electric load. On the other hand, when starting the engine, the crank pulley 15 is driven via the belt 16 on the contrary. Crank engine 1
[0017]
FIG. 2 is a circuit diagram showing an electrical connection state of the starter generator 11. The starter generator 11 is connected to the battery 17 via the first solenoid 21 (first circuit), while the second solenoid 22 (second Circuit) through a variable load resistor 23. The first and second solenoids 21 and 22 are alternately excited. When the first solenoid 21 is excited, the starter generator 11 is connected to the battery 17 side, and the battery 17 is charged / discharged as usual, and the starter generator 11 generates power. Is done. Further, when the second solenoid 22 is excited, the starter generator 11 is connected to the load resistor 23 side, and all the generated power of the starter generator 11 is consumed by the load resistor 23. That is, since the power generation current of the starter generator 11 increases, the power generation amount of the starter generator 11 increases accordingly.
[0018]
Although not shown, the engine 1 configured in this manner is connected to an automatic transmission equipped with a torque converter and mounted on the vehicle, and changes speed according to the vehicle speed and the throttle opening of the engine 1 when the vehicle travels. The stage is automatically switched.
On the other hand, an ECU 31 provided with an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.), a central processing unit (CPU), a timer counter, etc. provided for storage of a control program, a control map, etc. (Engine control unit) is installed. On the input side of the ECU 31, there are a brake sensor 32 for detecting the brake operation of the driver, a vehicle speed sensor 33 for detecting the vehicle speed V, and a shift position of the automatic transmission (not selected by the driver, but a shift stage switched by automatic shift). A shift position sensor 34 for detecting the shift lever position), an accelerator sensor 35 for detecting the accelerator operation amount Acc by the driver, and a crank angle sensor 36 (rotation) for outputting an SGT signal at predetermined intervals as the engine 1 rotates. Speed detecting means) and other various switches and sensors. Further, on the output side of the ECU 31, the fuel injection valve 3, the motor 4a that drives the throttle valve 4 to open and close, the spark plug 6, the starter generator 11, the first and second solenoids 21 and 22, the load resistor 23, and other devices Is connected.
[0019]
The ECU 31 executes various controls for operating the engine 1 including fuel injection control and ignition timing control based on each detection information described above.
Further, the ECU 31 performs idle stop control for automatically stopping the engine 1 temporarily for the purpose of reducing fuel consumption and reducing emissions while the vehicle is stopped due to a signal waiting or traffic jam (engine restart restart). Means) When the engine is stopped, the generated current of the starter generator 11 is increased to stop the engine 1 at a predetermined piston stop position. Details of the control will be described below.
[0020]
Execution and cancellation of the idle stop control can be arbitrarily selected by the driver with a mode selection switch (not shown), and when the execution of the idle stop control is selected with the mode selection switch and the ignition key of the vehicle is turned on, the ECU 31 Thus, the idle stop control is executed based on predetermined engine stop conditions and engine start conditions.
[0021]
The engine stop condition is that the brake operation is detected by the brake sensor 32, the vehicle speed V detected by the vehicle speed sensor 33 is 0 km / h, and the shift position detected by the shift position sensor 34 is D ( Drive)) or N (neutral) is set, and when these conditions are satisfied, the ECU 31 determines that the engine stop condition is satisfied and stops the fuel injection control. The engine 1 is stopped.
[0022]
As engine start conditions, it is set that the release of the brake operation is detected by the brake sensor 32, and the shift position detected by the shift position sensor 34 is D, and these conditions are satisfied. At this time, the ECU 31 determines that the engine start condition is satisfied, restarts the fuel injection control, and cranks and starts the engine 1 by the starter generator 11.
[0023]
On the other hand, in parallel with the idle stop control, the ECU 31 executes the braking control mode setting routine shown in FIG. 3 at a predetermined control interval. First, in step S2, it is determined whether or not an engine stop condition is satisfied. When the determination is NO (negative), the routine proceeds to step S4 to reset the braking control mode, and then the routine is temporarily terminated.
[0024]
If the determination in step S2 is YES due to the establishment of the engine stop condition, the ECU 31 proceeds to step S6, where the engine speed Ne calculated based on the SGT signal from the crank angle sensor 36 is lower than the braking start speed Ne0. It is determined whether or not. The braking start rotational speed Ne0 is a rotational speed at which braking is applied to the engine 1. In the present embodiment, the rotational speed Ne0 is set to a rotational speed slightly lower than the target idle rotational speed tgtID (for example, 500 rpm), but is not limited thereto. Various settings can be made.
[0025]
When the determination in step S6 is NO, the process proceeds to step S4. When the determination in step S6 is YES as the engine speed Ne decreases, the ECU 31 proceeds to step S8 and performs an engine stall determination. This determination is made based on the SGT signal from the crank angle sensor 36, and the engine stall determination is made when the SGT signal is interrupted for a predetermined time.
[0026]
If the engine 1 is not yet stalled and the determination in step S8 is NO, the ECU 31 proceeds to step S10 and sets the braking control mode. If the determination in step S8 is YES, the ECU 31 proceeds to step S4 and performs braking control. Reset the mode. Therefore, the braking control mode is set until the engine stalls after the engine rotational speed Ne falls below the braking start rotational speed Ne0 by the engine stop process.
[0027]
On the other hand, the ECU 31 executes the braking control routine shown in FIG. 4 at a predetermined control interval in parallel with the braking control mode setting routine, and first determines whether or not the braking control mode is set in step S22. When the determination is NO, the first solenoid 21 is excited in step S24, the routine is terminated after the second solenoid 22 is demagnetized in the subsequent step S26. Accordingly, the starter generator 11 is connected to the battery 17 side, and normal power generation is performed.
[0028]
If the determination in step S22 is YES, the first solenoid 21 is demagnetized in step S28, the second solenoid 22 is excited in the subsequent step S30, and the load resistance 23 is determined based on the engine speed Ne in step S32. Control the resistance. The resistance value is controlled based on the map shown in FIG. 5, and the resistance value at 200 rpm set as the rotation speed immediately before the stop is set to 0, and the resistance value is set to increase in proportion to the engine rotation speed Ne. The map characteristic for setting the resistance value is not limited to this. For example, the resistance value is increased exponentially with respect to the engine rotational speed Ne, or is constant in a region higher than the rotational speed immediately before the stop. May be set.
[0029]
By this processing, the starter generator 11 is connected to the load resistor 23 side, and the load torque for the engine 1 that drives the starter generator 11 is increased due to an increase in the generated current, and the output of the engine 1 is absorbed (torque absorption control means). . At this time, the higher the engine speed Ne that is decreasing, in other words, the larger the inertial energy of the engine 1 is, the larger the resistance value of the load resistor 23 is set and the load torque increases. As a result, the rotation can be quickly reduced.
[0030]
The engine 1 stops the piston at a position different from the normal time when the engine 1 does not receive the load torque due to the load torque applied during the rotation reduction. FIG. 6 shows the distribution of the piston stop position when the braking control of this embodiment is performed. The piston stops on the top dead center side from the point a (for example, BTDC 140 ° CA) indicating the start of compression of intake air. It turns out that the frequency is high.
[0031]
Here, since the compression resistance received by the piston is greatest immediately after the start of compression and decreases thereafter, the compression resistance is low between the compression start point a and the top dead center. In other words, the start required for the starter generator 11 There exists a region E where the torque is low (for example, BTDC 20 to 100 ° CA). FIG. 7 shows test results obtained by measuring the minimum starting torque required for the starter generator 11 for each piston stop position at the time of normal engine oil temperature. From this test result, the compression start point a and top dead center are also shown. It can be seen that there is a region E where the required starting torque is low.
[0032]
By performing the braking control, most of the piston stop positions are generated in the region E as shown in FIG. In other words, the braking start rotational speed Ne0 and the map characteristics shown in FIG. 5 are set based on a prior test so that such a piston stop position is realized. Therefore, even if the start torque of the starter generator 11 when the cranking is started in response to the engine start condition after that is reduced and the oil lubrication performance is deteriorated due to the rise in the oil temperature, the cranking is quickly performed with a margin. To achieve a good startability.
[0033]
In addition, since the resistance value of the load resistor 23 is set to be increased in proportion to the engine rotational speed Ne and the load torque corresponding to the inertial energy of the engine 1 that decreases with the engine rotational speed Ne is given, Thus, the frequency with which the piston stops is increased, and the subsequent startability can be further improved.
On the other hand, since the existing starter generator 11 is used for braking control, there is an advantage that an increase in vehicle weight and an increase in manufacturing cost can be prevented as compared with the case where a dedicated device is provided as a torque absorbing means. can get.
[0034]
Incidentally, in an engine (shown in FIG. 1) provided with a variable valve timing mechanism 41 (valve timing adjusting means) that adjusts the opening / closing timing of the intake valve based on the operating state of the engine 1, the compression start is started together with the closing timing of the intake valve. Since the point a changes, the region E where the compression resistance is low also fluctuates accordingly.
Therefore, similarly to the map of FIG. 5 based on the engine rotational speed Ne, the resistance value of the load resistor 23 is set from a predetermined map based on the control state of the intake valve (for example, the advance amount of the cam shaft from the reference position). You may make it do. If comprised in this way, a piston stop position will be adjusted according to the change of the area | region E accompanying control of an intake valve, and, as a result, a piston is set to the area | region E where compression resistance is low irrespective of the control condition of an intake valve. Since it can stop, the advantage that startability can be improved further is acquired.
[0035]
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the engine control device is applied to a vehicle with an idle stop function. However, the application is not limited to this, and for example, the engine control device for a hybrid vehicle may be realized. In hybrid vehicles, the engine is stopped and started according to the running state, battery SOC (State Of Charge), etc., but if the power generation current of the starter generator is increased when the engine is stopped, the compression resistance is reduced. Good startability can be realized by stopping the piston in the low region E.
[0036]
Further, even when embodied as an engine control device for a vehicle with an idle stop function, the types of the engine 1 and the transmission are not limited to the above-described embodiments. For example, the cylinder arrangement of the engine 1 is changed, or in-cylinder injection is performed. It may be configured as a type engine, or a manual transmission may be applied instead of the automatic transmission.
On the other hand, in the above embodiment, the brake operation, the vehicle speed of 0 km / h, the shift position is set to a travelable position such as D or N as the engine stop condition, and the brake operation stop, the shift is set as the engine start condition. Although the position is set to be a travelable position such as D, the stop condition and the start condition are not limited to this. For example, as the engine stop condition, the accelerator operation amount Acc detected by the accelerator sensor 35 is set. May be 0 (during idling).
[0037]
Furthermore, in the above embodiment, the resistance value of the load resistor 23 is adjusted according to the engine speed Ne, but it is not always necessary to configure the load resistor 23 as a variable type. Instead, a fixed resistor having a predetermined resistance value is used. You may apply.
On the other hand, in the above-described embodiment, load torque is applied to the engine 1 using the starter generator 11 having both functions as an alternator and a starter motor. A load torque may be applied to the engine 1 by increasing the generated current of the alternator, or a dedicated device may be provided as a torque absorbing means.
[0038]
【The invention's effect】
As described above, according to the engine control apparatus of the first aspect of the present invention, cranking by a starter motor or the like can be quickly started up at the time of engine start, and thus good startability can be realized.
According to the engine control apparatus of the second aspect of the present invention, in addition to the first aspect, it is possible to increase the frequency at which the piston stops in the region where the compression resistance of the intake air is low, thereby further improving the engine startability.
[0039]
According to the engine control apparatus of the invention of claim 3, in addition to claim 1 or 2, the engine is further improved in starting performance by stopping the piston in a region where the compression resistance is low regardless of the control state of the intake valve. Can be made.
According to the engine output control device of the fourth and fifth aspects of the invention, in addition to the first to third aspects, by using an existing generator as a torque absorbing means, an increase in vehicle weight and an increase in manufacturing cost can be prevented. Can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an engine control device applied to a vehicle with an idle stop function according to an embodiment.
FIG. 2 is a circuit diagram showing an electrical connection state of a starter generator.
FIG. 3 is a flowchart showing a braking control mode setting routine executed by the ECU.
FIG. 4 is a flowchart showing a braking control routine executed by the ECU.
FIG. 5 is an explanatory diagram showing a map for setting a resistance value of a load resistor.
FIG. 6 is a diagram illustrating a distribution of piston stop positions when the braking control according to the embodiment is performed.
FIG. 7 is a diagram showing a test result obtained by measuring a start torque required for the starter generator for each piston stop position.
FIG. 8 is a diagram illustrating a distribution of piston stop positions when braking control is not performed.
[Explanation of symbols]
1 Engine 11 Starter generator (torque absorption means, generator)
21 First solenoid (first circuit)
22 Second solenoid (second circuit)
23 Load resistance (variable resistance)
31 ECU (engine stop / restart means, torque absorption control means)
36 Crank angle sensor (rotational speed detection means)
41 Variable valve timing mechanism (valve timing adjustment means)

Claims (5)

Engine stop / restart means for stopping the engine when a predetermined stop condition is satisfied, and restarting the engine when the predetermined restart condition is satisfied;
Torque absorbing means connected to the engine output shaft and capable of absorbing the torque of the engine;
Torque absorption control means for controlling the torque absorption means to absorb the engine torque when the engine is stopped due to establishment of the stop condition;
The torque absorption control means includes a rotation speed detection means for detecting an engine rotation speed, and absorbs torque until the engine is stopped after the engine rotation speed becomes lower than a predetermined rotation speed. Engine control device. 2. The engine control apparatus according to claim 1, wherein the torque absorption control means decreases the torque absorption amount in accordance with a decrease in the engine rotation speed detected by the rotation speed detection means. Valve timing adjusting means for adjusting the opening and closing timing of the intake valve based on the operating state of the engine,
3. The engine control apparatus according to claim 1, wherein the torque absorption control means controls the torque absorption amount according to the opening / closing timing of the intake valve adjusted by the valve timing adjusting means. 4. The engine control apparatus according to claim 1, wherein the torque absorbing means is a generator driven by an output from the engine. A first circuit connecting the generator and the battery;
A second circuit connecting the generator and the variable resistor;
The torque absorption control means shuts off the first circuit and connects the second circuit when torque absorption is performed by the torque absorption means, and changes the resistance value of the variable resistor to change the torque absorption amount. The engine control device according to claim 4, wherein the engine control device is changed.

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