JP2015145643A - Electronic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a situation that an engine is recovered from a fuel cut at improper timing.SOLUTION: In an engine ECU 2, a unit change amount being a change amount of a rotation number at a preset unit crank angle is firstly calculated during the execution of a fuel cut. Also in the engine ECU 2, a torque delay angle being a timing at which a torque is succeedingly generated by an engine is estimated on the assumption that the fuel cut is finished at a current time point during the execution of the fuel cut. Then, in the engine ECU 2, an estimated engine rotation number being an engine rotation number at the torque generation timing is calculated on the basis of the unit change amount and the torque delay angle. Furthermore, in the engine ECU 2, it is determined whether or not the engine is recovered from the fuel cut by using the calculated estimated engine rotation number.

Description

  The present invention relates to an electronic control device that performs control for executing fuel cut.

As a technique for improving the fuel efficiency of a vehicle, a fuel cut that temporarily stops fuel supply to an engine in a predetermined driving state is known.
The timing for returning from the fuel cut is determined in consideration of the following two requirements. The first requirement is to make the fuel cut period as long as possible in order to improve fuel efficiency. The second requirement is to avoid engine stall due to a decrease in engine speed due to fuel cut.

  As a fuel cut return method that satisfies these requirements, when the arrival time T1 from the current engine speed to the idle speed is less than the predicted time T2 from the fuel cut return to the generation of torque Further, there is known a method for returning from a fuel cut (see, for example, Patent Document 1).

Japanese Patent No. 3399479

  However, in the technique described in Patent Document 1, the estimated time T2 from when the fuel cut is restored to when the torque is generated is set in advance according to the engine state (cooling water temperature, intake air temperature, fuel temperature, etc.). The correction timing of the fuel cut is adjusted by using the correction.

  However, in order to satisfy both the first request and the second request, the correction value must be set to a value with a certain margin with respect to the optimum fuel cut return timing. I don't get it.

  For this reason, there is a possibility that fuel economy deteriorates because the fuel cut return timing is advanced, or engine stall occurs because the fuel cut return timing is delayed.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for suppressing the occurrence of a situation in which a fuel cut is returned at an inappropriate timing.

  An electronic control device of the present invention made to achieve the above object performs control for executing fuel cut for stopping fuel supply to an engine having a plurality of cylinders, and includes a change rate calculation means and a timing estimation means. And an engine speed calculation means and a return determination means.

  First, the change rate calculation means calculates a rotation rate change rate, which is a change amount of the engine rotation speed in a preset measurement time interval, during execution of fuel cut. Further, the timing estimation means estimates the torque generation timing that is the timing at which the engine next generates torque when it is assumed that the fuel cut has ended at the present time during the execution of the fuel cut.

  The engine speed calculation means is configured to generate torque that is the engine speed at the torque generation timing based on at least the rotation speed change rate calculated by the change rate calculation means and the torque generation timing estimated at the torque generation timing. Calculate the engine speed. Further, the return determination means determines whether or not to return from the fuel cut using the engine speed at the time of torque generation calculated by the engine speed calculation means.

  The timing estimation means detects an injectable cylinder, which is a cylinder capable of fuel injection at the present time, from among a plurality of cylinders, and estimates torque generation timing based on the next ignition timing in the injectable cylinder.

  In the electronic control device of the present invention configured as described above, by estimating the torque generation timing, the engine speed at the next torque generation timing (engine speed at the time of torque generation) is estimated at the present time. Accordingly, it is possible to determine whether the engine stall occurs if the engine is not restored from the fuel cut at this time by determining whether engine stall occurs at the engine speed when the torque is generated. It can be determined whether or not to return from the fuel cut.

  In the electronic control device of the present invention, the torque generation timing is estimated based on the next ignition timing in a cylinder (injectable cylinder) in which fuel injection is currently possible. The ignition timing is calculated by an electronic control unit that controls the engine, and the spark plug is controlled so as to ignite at the calculated ignition timing. Then, by igniting the spark plug at the calculated ignition timing, the fuel supplied to the injectable cylinder burns and torque is generated. For this reason, the timing at which torque is generated can be estimated by acquiring the calculated ignition timing. That is, it is not necessary to correct the torque generation timing by using correction values that change according to the engine state such as at least the coolant temperature, the intake air temperature, and the fuel temperature.

  For this reason, it is possible to suppress the occurrence of a situation where the fuel cut is returned at an inappropriate timing due to providing a margin for the correction value for correcting the torque generation timing.

1 is a schematic configuration diagram showing an engine control system 1. FIG. It is a flowchart which shows a unit variation | change_quantity calculation process. It is a flowchart which shows a torque generation estimation process. It is a timing chart which shows the 1,2,3,4 cylinder injection possible range. It is a flowchart which shows an engine speed estimation process. It is a flowchart which shows FC return determination processing. It is a timing chart which shows operation | movement when performing a fuel cut.

Embodiments of the present invention will be described below with reference to the drawings.
The engine control system 1 is mainly configured of an engine 100 and an electronic control unit 2 (hereinafter referred to as an engine ECU 2) that controls the engine 100.

  The engine 100 is an internal combustion engine mounted on a vehicle, and as shown in FIG. 1, a combustion chamber 104 is defined by cylinders # 1, # 2, # 3, # 4 (main cylinders) by a cylinder 101, a piston 102, and a cylinder head 103. In the embodiment, it is formed every four cylinders). A spark plug 105 for igniting the fuel is attached in the combustion chamber 104.

An intake pipe 120 is connected to the combustion chamber 104 of the engine 100 via an intake valve 106, and an exhaust pipe 140 is connected via an exhaust valve 107.
The intake pipe 120 is provided with a throttle valve 130 that adjusts the amount of air supplied to the engine 100. The intake pipe 120 is connected to each cylinder of the engine 100 via an intake manifold 121, and the air whose amount is adjusted by the throttle valve 130 through the intake pipe 120 passes through the intake manifold 121 and passes through the engine. Distribution is supplied to each of the 100 cylinders.

  The intake manifold 121 is provided with an injector 122 for each cylinder of the engine 100. The fuel injected from the injector 122 is mixed with air from the intake pipe 120 and supplied to each cylinder of the engine 100. The fuel injection order of each cylinder # 1 to # 4 is “# 1 → # 3 → # 4 → # 2”.

  Further, in each cylinder of the engine 100, the air-fuel mixture is introduced into the combustion chamber 104 as the intake valve 106 is opened and closed, and the introduced air-fuel mixture is combusted by ignition of the ignition plug 105, whereby the piston 102 is pushed down. Torque is applied to the crankshaft 108 of the engine 100. The exhaust gas after combustion is discharged to the outside through the exhaust pipe 140 as the exhaust valve 107 is opened and closed.

  Further, the engine 100 is provided with a water temperature sensor 109, a crank angle sensor 110, an air flow meter 123, a throttle opening sensor 124, an intake pressure sensor 125, and an air-fuel ratio sensor 141 as sensors for detecting the operating state. .

Water temperature sensor 109 detects the cooling water temperature of engine 100.
Crank angle sensor 110 detects the rotation angle of crankshaft 108 of engine 100. Specifically, the crank angle sensor 110 outputs a crank angle signal that causes an edge at every predetermined angle (for example, every 10 ° CA) in accordance with the rotation of the crankshaft 108 of the engine 100.

  Air flow meter 123 detects the amount of air supplied to engine 100 through intake pipe 120. The throttle opening sensor 124 detects the opening of the throttle valve 130. The intake pressure sensor 125 detects the pressure in the intake pipe 120. The air-fuel ratio sensor 141 detects the air-fuel ratio of the fuel mixture supplied to the engine 100 from the oxygen concentration in the exhaust gas.

Further, an accelerator opening sensor 161 that detects the amount of depression of the accelerator pedal 160 (accelerator opening) is provided in a vehicle on which the engine 100 is mounted.
The engine ECU 2 also includes a microcomputer 3 that executes processing for controlling the engine 100, a drive circuit 4 that operates various actuators according to control signals from the microcomputer 3, and an input that inputs various signals to the microcomputer 3. Circuit 5.

  The microcomputer 3 includes a signal from the water temperature sensor 109, a signal from the crank angle sensor 110, a signal from the air flow meter 123, a signal from the throttle opening sensor 124, a signal from the intake pressure sensor 125, and an air-fuel ratio sensor 141. And the signal from the accelerator opening sensor 161 are input via the input circuit 5. The input circuit 5 is a general one, and can be processed by the microcomputer 3 by performing predetermined signal processing such as analog / digital conversion, noise removal, waveform shaping, etc., on a signal such as a sensor signal. Convert input signal to signal.

  The microcomputer 3 detects the state of the engine 100 based on the above signals input via the input circuit 5 and outputs a control signal to the drive circuit 4 based on the detection result. Thereby, the microcomputer 3 controls the various actuators such as the throttle motor 131 that changes the opening degree of the ignition plug 105 in each cylinder, the injector 122 in each cylinder, and the throttle valve 130 to operate the engine 100.

  The microcomputer 3 starts fuel cut control for stopping fuel injection by the injector 122 when a preset fuel cut start condition is satisfied. The fuel cut start condition is, for example, that the accelerator opening is 0 and the engine speed is a predetermined value or more.

  In the engine control system 1 configured as described above, the microcomputer 3 of the engine ECU 2 executes unit change amount calculation processing, torque generation estimation processing, engine rotation speed estimation processing, and fuel cut return determination processing described later.

First, the procedure of the unit change amount calculation process will be described. The unit variation calculation process is a process that is repeatedly executed during the fuel cut.
When this unit change amount calculation process is executed, the microcomputer 3 of the engine ECU 2 first calculates the unit change amount in S10 as shown in FIG. 2, and once ends the unit change amount calculation process. Specifically, the unit change amount is calculated by dividing a value obtained by subtracting the previous engine speed from the current engine speed by a preset unit crank angle (in this embodiment, for example, 30 ° CA). .

  The engine speed is calculated by measuring the time interval at which the crank angle signal is output from the crank angle sensor 110. The engine speed is the latest among the engine speeds calculated so far. The previous engine speed is the engine speed calculated based on the output of the crank angle signal before the crank angle at which the current engine speed is calculated, a unit crank angle (for example, 30 ° CA in this embodiment). is there.

Next, the procedure of torque generation estimation processing will be described. The torque generation estimation process is a process that is repeatedly executed during the fuel cut.
When this torque generation estimation process is executed, as shown in FIG. 3, the microcomputer 3 of the engine ECU 2 first determines in S110 that the current crank angle is the first cylinder injection possible range, the second cylinder injection possible range, It is determined whether it is included in either the third cylinder injectable range or the fourth cylinder injectable range.

The nth cylinder injectable range (n = 1, 2, 3, 4) indicates a crank angle range in which fuel can be injected in the cylinder #n.
As shown in FIG. 4, the nth cylinder injectable range is basically the exhaust stroke of cylinder #n (see the first cylinder injectable range IR1 and the third cylinder injectable range IR3 in FIG. 4). . However, when the injectable limit is retarded, the injectable range of the cylinder becomes longer by the retarded angle, and the injectable range of the next cylinder becomes shorter.

  In FIG. 4, the injection possible limit IL1 of the cylinder # 1, the injection possible limit IL2 of the cylinder # 2, and the injection possible limit IL3 of the cylinder # 3 are the end points of the exhaust stroke. Therefore, the first cylinder injectable range IR1 and the third cylinder injectable range IR3 are the exhaust strokes of cylinder # 1 and cylinder # 3, respectively.

  On the other hand, since the injectable limit IL4 of the cylinder # 4 is retarded, the fourth cylinder injectable range IR4 becomes longer than the exhaust stroke of the cylinder # 4 by the retard angle. Then, the second cylinder injectable range IR2 of cylinder # 2, which is the next cylinder, is shortened by the retard angle.

  In the present embodiment, the exhaust strokes of cylinder # 1, cylinder # 3, cylinder # 4, and cylinder # 3 are set to 0 to 180 CA, 180 to 360 CA, 360 to 540 CA, and 540 to 720 CA, respectively. The first, second, third and fourth cylinder injection possible ranges are set so as not to overlap each other within the range of 0 to 720CA. Therefore, in S110, any one of the first, second, third, and fourth cylinder injection possible ranges can be selected based on the current crank angle.

  As shown in FIG. 3, when the process of S110 is completed, a cylinder in which torque is generated (hereinafter referred to as a torque generating cylinder) is determined in S120. Specifically, when the n-th cylinder injection possible range (n = 1, 2, 3, 4) is selected in S110, the cylinder #n is determined as the torque generating cylinder.

  Thereafter, in S130, a crank angle from the current crank angle to the TDC of the torque generating cylinder (hereinafter referred to as a TDC delay angle) is calculated. Specifically, the current crank angle is subtracted from the TDC of the torque generating cylinder, and this subtracted value is used as the TDC delay angle.

  The TDC is the top dead center of the compression stroke of the cylinder. For example, when the first cylinder injection possible range is selected in S110, since the torque generating cylinder is cylinder # 1, TDC is 540CA (see # 1 TDC in FIG. 4).

  Further, in S140, a crank angle until torque is generated (hereinafter referred to as a torque delay angle) is calculated from the current crank angle, and the torque generation estimation process is temporarily ended. Specifically, a basic offset (described later) and an ignition correction value (described later) are added to the TDC delay angle calculated in S130, and this added value is used as a torque delay angle.

  In normal ignition control, the ignition timing is set to MBT (Minimum Advance for Best Torque) in order to maximize the output torque. In this case, the timing at which the maximum torque is generated is several CA after the TDC (for example, after 10 CA). The basic offset is calculated based on the difference from TDC to the timing when the maximum torque is generated.

  In the ignition control, for example, the ignition timing may be set at a timing deviating from the MBT due to, for example, a delay at start-up or a delay in knock suppression. The ignition correction value is calculated based on the difference between such ignition timing and MBT.

Next, the procedure of the engine speed estimation process will be described. The engine speed estimation process is a process that is repeatedly executed during the fuel cut.
When the engine speed estimation process is executed, the microcomputer 3 of the engine ECU 2 first calculates an estimated change amount in S210 as shown in FIG. Specifically, the unit change amount calculated in S10 is multiplied by the torque delay angle calculated in S140, and this multiplied value is used as the estimated change amount.

  Further, in S220, an estimated engine speed is calculated, and the engine speed estimation process is temporarily terminated. Specifically, the current engine speed and the estimated change amount calculated in S210 are added, and this added value is used as the estimated engine speed.

  Next, a procedure of fuel cut return determination processing (hereinafter referred to as FC return determination processing) will be described. The FC recovery determination process is a process that is repeatedly executed during the fuel cut.

  When this FC return determination process is executed, the microcomputer 3 of the engine ECU 2 first, at S310, the estimated engine speed calculated at S220 exceeds the preset return determination speed as shown in FIG. Judge whether or not. Note that the engine speed at which engine stall does not occur is set as the return determination engine speed. The return determination rotational speed of the present embodiment is the engine rotational speed during idle operation.

Here, if the estimated engine speed exceeds the return determination speed (S310: YES), the FC return determination process is temporarily terminated. That is, the fuel cut continues.
On the other hand, when the estimated engine speed is equal to or lower than the return determination speed (S310: NO), the fuel cut is ended in S320, and the FC return determination process is ended. That is, it returns from the fuel cut.

Next, the operation when performing fuel cut in the engine control system 1 will be described.
As shown in FIG. 7, when the fuel cut is started at time t1 (see the FC request at time t1), the engine speed gradually decreases (see engine speed Ne in FIG. 7), and the estimated engine Calculation of the rotational speed is started (see the estimated engine rotational speed Ne ′ in FIG. 7).

  When the estimated engine speed becomes equal to or lower than the return determination speed at time t2, the engine speed returns from the fuel cut at a timing higher than the return determination speed (see the FC request at time t2).

  Thereafter, torque is generated before the engine speed reaches the return determination speed (see time t3), so that the decrease in the engine speed stops near the return determination speed and the engine stall is avoided.

  The engine ECU 2 configured as described above first calculates a unit change amount that is a change amount of the engine speed at a preset unit crank angle during execution of fuel cut (S10). Further, the engine ECU 2 estimates a torque delay angle that is a timing at which torque is next generated in the engine when it is assumed that the fuel cut is finished at the present time during the execution of the fuel cut (S110 to S140).

  Then, the engine ECU 2 calculates an estimated engine speed, which is the engine speed at the torque generation timing, based on the unit change amount and the torque delay angle (S210 to S220). Further, the engine ECU 2 determines whether or not to return from the fuel cut using the calculated estimated engine speed (S310).

  The engine ECU 2 configured in this way estimates the torque delay angle to estimate the engine speed (estimated engine speed) at the next timing when torque is generated. As a result, it is possible to determine whether the engine stall occurs unless the engine is restored from the current fuel cut by determining whether the engine stall occurs at this estimated engine speed. It can be determined whether or not to return from.

  Then, the engine ECU 2 estimates the torque delay angle based on the next ignition timing in the cylinder in which fuel injection is possible at present (hereinafter referred to as an injectable cylinder). The ignition timing is calculated by the engine ECU 2, and the spark plug 105 is controlled to ignite at the calculated ignition timing. Then, by igniting the spark plug 105 at the calculated ignition timing, the fuel supplied to the injectable cylinder burns and torque is generated. For this reason, the timing at which torque is generated can be estimated by acquiring the calculated ignition timing. That is, it is not necessary to correct the torque generation timing by using correction values that change according to the engine state such as at least the coolant temperature, the intake air temperature, and the fuel temperature.

  For this reason, it is possible to suppress the occurrence of a situation where the fuel cut is returned at an inappropriate timing due to providing a margin for the correction value for correcting the torque generation timing.

  Further, the engine ECU 2 calculates the estimated engine speed on the assumption that the change in the engine speed per unit change amount continues until the torque delay angle (S210). Therefore, the estimated engine speed can be calculated by a simple method of multiplying the unit change amount and the torque delay angle, and the processing load on the engine ECU 2 can be reduced.

  Further, in the engine ECU 2, when the estimated engine speed is equal to or lower than the return determination speed set in advance so as to be the engine speed during idling (S310: NO), it is determined that the fuel cut is to be returned. As a result, the fuel cut can be continued as long as possible within the range in which the engine stall can be avoided, and the fuel efficiency of the vehicle equipped with the engine control system 1 can be improved.

  In the embodiment described above, the engine ECU 2 is the electronic control unit according to the present invention, the processing at S10 is the change rate calculating means according to the present invention, the processing at S110 to S140 is the timing estimating means according to the present invention, and the processing at S210 to S220 is the present invention. The engine speed calculation means in S310 and the processing in S310 are return judgment means in the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the above-described embodiment, the return determination rotation speed is set to the engine rotation speed during idle operation. However, in order to avoid engine stall more reliably, the return determination rotational speed may be set to a value higher than the engine rotational speed during idle operation.

  In the above embodiment, the estimated engine speed is calculated on the assumption that the engine speed is decreased by the unit change amount calculated in S10 until the next torque is generated (see S220). However, the fluctuation tendency of the engine speed depends on the engine state. Therefore, for example, in the calculation of the estimated change amount (see S210), the acceleration component of the engine speed fluctuation is added to the unit change amount (see S10) that is the speed component of the engine speed fluctuation. At the same time, this acceleration component may be corrected by the engine oil temperature or the coolant temperature. Thereby, the estimation accuracy of the estimated engine speed can be improved.

  Moreover, in the said embodiment, while calculating the variation | change_quantity of an engine speed for every unit crank angle, the thing which calculates an estimated engine speed by estimating a torque delay angle was shown. However, the estimated engine speed may be estimated by calculating the amount of change in the engine speed per unit time and calculating the time from the current time to the torque generation timing.

  DESCRIPTION OF SYMBOLS 1 ... Engine control system, 2 ... Engine ECU, 100 ... Engine

Claims (3)

An electronic control unit (2) for performing control for executing fuel cut for stopping fuel supply to an engine (100) having a plurality of cylinders,
A change rate calculating means (S10) for calculating a rate of change of the engine speed that is a change amount of the engine speed in a preset measurement time interval during the execution of the fuel cut;
Timing estimation means (S110 to S140) for estimating a torque generation timing, which is a timing at which torque is next generated in the engine, when it is assumed that the fuel cut is ended at the present time during execution of the fuel cut;
An engine at the time of torque generation that is the engine speed at the torque generation timing based on at least the rotation speed change rate calculated by the change rate calculation means and the torque generation timing estimated at the torque generation timing Engine speed calculation means (S210 to S220) for calculating the speed;
Return determination means (S310) for determining whether to return from the fuel cut using the engine speed at the time of torque generation calculated by the engine speed calculation means;
The timing estimation means includes
Among the plurality of cylinders, an injectable cylinder that is the cylinder capable of fuel injection at the present time is detected, and the torque generation timing is estimated based on a next ignition timing in the injectable cylinder. Control device. The engine speed calculation means includes
Assuming that the change in the engine speed at the speed change rate calculated by the change rate calculation means continues until the torque generation timing estimated by the timing estimation means, the engine speed at the time of torque generation The electronic control device according to claim 1, wherein the electronic control device is calculated. The return determination means includes
The engine is determined to return from the fuel cut when the engine speed at the time of torque generation is equal to or lower than an idling target speed set in advance so as to be equal to an engine speed during idling of the engine. The electronic control device according to claim 1 or 2.