JP5561218B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to a technique in the case where an opening abnormality of a mechanical throttle valve that adjusts an intake air amount by a driver's stepping operation force occurs.

  There are two types of throttle valves: an electric type in which the throttle opening is controlled by an electric motor, and a mechanical type in which the throttle valve is mechanically driven by a driver's depression pedal operation force. Among these, the mechanical throttle valve, unlike the electric type, cannot adjust the throttle opening independently of the accelerator opening. For this reason, for example, if the accelerator pedal is pushed down regardless of the driver's intention, or if a malfunction occurs such as when the driver tries to return the accelerator pedal, the throttle valve remains open. Abnormality may occur. In this case, it is conceivable that the engine intake amount does not decrease, and as a result, the engine output is not reduced against the will of the driver.

  As a coping method when such a situation occurs, for example, Patent Document 1 discloses that the engine is abnormal when the throttle opening is equal to or greater than a predetermined value and the brake operation is repeated at a predetermined interval or less. It is disclosed that the fuel cut is performed. As a result, the engine output is reduced.

Japanese Utility Model Publication No. 01-124354

  If the above-mentioned throttle opening abnormality is detected while the vehicle is running, it is necessary to keep the vehicle in a state where it can run for the purpose of enabling retreating after the start of engine output restriction due to the occurrence of the abnormality. There is. In this case, for example, it is conceivable to perform control to limit the engine output while avoiding engine stall by repeating engine combustion stop and combustion return according to the engine rotation speed.

  However, when the engine combustion stop and the combustion return are repeatedly performed, it is conceivable that the engine rotational speed repeatedly increases and decreases, and the vehicle repeats acceleration and deceleration due to the rotational fluctuation. In this case, there is a concern that the running stability of the vehicle is reduced.

  The present invention has been made in view of the above problems, and in the vehicle running state, even when a throttle opening abnormality occurs in which the mechanical throttle valve does not close while being opened contrary to the intention of the driver, the vehicle running safety An object of the present invention is to provide an engine control device capable of suppressing the deterioration of the performance.

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

The engine control device of the present invention is applied to an in-vehicle engine including a mechanical throttle valve that is mechanically driven by a driver's depressing operation force on an accelerator pedal to adjust an intake air amount of the engine. In particular, the first configuration comprises an abnormality detection means for detecting an abnormality in throttle opening, which is an abnormality that the throttle valve is not closed while the throttle valve is open in a state where the driver depresses the accelerator pedal in the vehicle traveling state, An output limiting means for restricting engine output by stopping engine combustion when the throttle opening abnormality is detected by an abnormality detecting means, and after the engine combustion stop in the vehicle running state by the output limiting means When the engine rotation speed is lower than the first determination value, the engine is returned to combustion, and after the combustion return, the engine rotation speed is higher than the second determination value on the higher rotation side than the first determination value. Combustion control means for performing a combustion return stop process for stopping the combustion, and accompanying engine combustion stop by the combustion return stop process When the vehicle speed is reduced, the along with the vehicle speed decreases, characterized in that it comprises a deviation amount changing means for reducing the deviation amount between the second judgment value and the first determination value.

  In short, in a system equipped with a mechanical throttle valve, there is an abnormality (throttle opening abnormality) that the throttle valve remains open even though the driver depresses the accelerator pedal. Can be considered. In this configuration, when such a throttle opening abnormality occurs during traveling of the vehicle, the combustion of the engine is stopped to limit the output of the engine, so that the vehicle can be prevented from entering a dangerous state. Further, when the output is restricted, the engine is restarted and stopped according to the engine speed, so that the vehicle can be kept running while avoiding engine stall.

  In particular, in this configuration, when a throttle opening abnormality is detected, a determination value (first determination value) of the engine speed at which combustion is restored and a determination value (second determination value) of the engine speed at which combustion stops are determined. Since the amount of deviation is reduced as the vehicle speed decreases, fluctuations in engine rotation speed due to repeated combustion / combustion of the engine can be suppressed as the vehicle speed decreases. That is, the rotational fluctuation can be reduced in a low vehicle speed range that is easily affected by the rotational fluctuation of the engine, and as a result, it is possible to suppress a decrease in the stability of the vehicle when the engine output is limited. .

In the second configuration , the divergence amount changing means decreases the divergence amount by decreasing the second determination value as the vehicle speed decreases. According to this configuration, since it is not necessary to change the first determination value, the amount of deviation between the first determination value and the second determination value while maintaining the first determination value at the minimum rotation speed at which engine stall does not occur. Can be changed.

In the third configuration , the abnormality detecting means detects that the brake pedal is depressed when the throttle valve is open as the throttle opening abnormality. In a system including a mechanical throttle valve, when the throttle valve is in an open state and the brake pedal is in a depressed state, it can be determined that the driver does not intend to travel and that the throttle valve is abnormally opened. . Therefore, in the above case, the engine output may be limited on the assumption that the throttle opening abnormality has occurred.

1 is an overall schematic configuration diagram of an engine control system. The flowchart which shows engine control when throttle opening abnormality arises in the vehicle running state. The map which shows the relationship between a vehicle speed and a 2nd determination value. The time chart which shows the specific aspect of the engine control of this embodiment. The time chart which shows the specific aspect of the engine control in other embodiment.

  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 a spark ignition type on-vehicle multi-cylinder gasoline engine. In the control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, ignition timing, and the like. FIG. 1 shows an overall schematic configuration diagram of the engine control system.

  In FIG. 1, an intake pipe 11 and an exhaust pipe 12 are connected to the engine 10, and the intake pipe 11 is provided with a throttle valve 13 for adjusting the amount of intake air into the cylinder. The throttle valve 13 is a mechanical air amount adjusting means that is mechanically opened and closed by a depression operation force of the accelerator pedal 14 by the driver. In the throttle valve 13, the opening (throttle opening) is adjusted by transmitting the operation amount when the accelerator pedal 14 is pushed down to the throttle valve 13 via the cable 15. The throttle opening is detected by a throttle opening sensor 17 incorporated in the throttle actuator 16.

  A surge tank 18 is provided on the downstream side of the throttle valve 13. An intake manifold 19 that introduces air into each cylinder of the engine 10 is connected to the surge tank 18. In the intake manifold 19, an injector as a fuel injection means that injects and supplies fuel near the intake port of each cylinder. 21 is attached.

  In the present embodiment, an intake port injection type engine is employed, and the injector 21 is provided in the vicinity of the intake port. Instead, a direct injection type engine is employed, and the injector 21 is provided for each cylinder. It is good also as a structure provided in a cylinder head etc.

  An intake valve 22 and an exhaust valve 23 are provided at the intake port and the exhaust port of the engine 10, respectively. Among these, the air-fuel mixture is introduced into the combustion chamber 24 by opening the intake valve 22, and the exhaust gas after combustion is discharged from the combustion chamber 24 to the exhaust pipe 12 by opening the exhaust valve 23. Is done.

  A spark plug 25 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 25 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 25, and the air-fuel mixture introduced into the combustion chamber 24 is ignited and used for combustion.

  The exhaust pipe 12 is provided with an oxygen concentration sensor 26 for detecting the oxygen concentration in the exhaust gas, and a catalyst 27 as an exhaust purification device is provided on the downstream side of the oxygen concentration sensor 26. The catalyst 27 is, for example, a three-way catalyst, and purifies harmful components and the like in the exhaust when the exhaust passes.

  In addition, this system includes a coolant temperature sensor 28 that detects the engine coolant temperature, a crank angle sensor 31 that outputs a pulse signal each time the crankshaft 29 rotates a predetermined crank angle, an engine such as an intake air amount and intake pipe negative pressure. Various sensors such as a load sensor 36 for detecting the load, an accelerator sensor 32 for detecting the operation amount of the accelerator pedal 14, a brake sensor 34 for detecting the operation amount of the brake pedal 33, and a vehicle speed sensor 35 for detecting the vehicle speed are provided. . The accelerator pedal 14 and the brake pedal 33 may be a suspension type (pendant type) or a floor support type (organ type).

  As is well known, the ECU 40 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) composed of a CPU, a ROM, a RAM, etc., and executes various control programs stored in the ROM, so that the ECU 40 responds to each engine operation state. Various controls of the engine 10 are performed. That is, the microcomputer of the ECU 40 inputs detection signals from the various sensors described above, calculates the fuel injection amount, ignition timing, and the like based on the various detection signals, and controls the drive of the injector 21 and the ignition device. .

  Here, when the throttle valve 13 is mechanical, the throttle opening cannot be adjusted independently of the accelerator opening. For this reason, for example, the accelerator pedal 14 is pushed down regardless of the driver's intention due to the displacement of the floor mat or the like, or the accelerator pedal 14 does not return to the original position due to malfunction of the cable 15 or the like. In this case, the open state of the throttle valve 13 is continued. In this case, since the amount of intake air does not decrease even when the driver releases the accelerator operation, there is a concern that the engine output is not reduced against the driver's will.

  Therefore, in the present embodiment, when there is an abnormality that does not close while the throttle valve 13 is open (throttle opening abnormality) while the vehicle is running, output restriction control is performed to stop the combustion of the engine 10 and restrict the engine output. We are going to carry out. Specifically, when it is detected that the throttle valve 13 is in the open state and the brake pedal 33 is in the depressed state, it is determined that the throttle opening abnormality has occurred, and the output of the engine 10 is limited. To do. If the brake pedal 33 is depressed even though the throttle is open, the driver has no intention of accelerating or driving, and the throttle open state is not based on the driver's intention. Because it is.

  Further, in the present embodiment, when the combustion of the engine 10 is stopped in response to the detection of the throttle opening abnormality, the engine rotation speed becomes lower than the first determination value T1 determined based on the minimum rotation speed at which engine stall does not occur. In this case, the combustion of the engine 10 is restarted, and the combustion of the engine 10 is stopped when it becomes higher than the second determination value T2 on the higher rotation side than the first determination value T1. In other words, when the engine output is limited when the throttle is abnormal, engine stall is avoided, so that the vehicle can run.

  By the way, when the combustion stop of the engine 10 and the combustion restart of the engine 10 are repeated in the vehicle running state, the engine rotation speed repeatedly increases and decreases, and the vehicle repeats acceleration and deceleration under the influence of engine rotation fluctuation. Can be considered. Further, the influence of such engine rotation fluctuations on the vehicle speed differs depending on the vehicle speed, and the lower the vehicle speed, the more easily the vehicle speed becomes unstable due to the influence of engine rotation fluctuation. In particular, it is necessary to avoid such a situation where the vehicle speed is unstable in consideration of the fact that the acceleration and deceleration of the vehicle are not intended by the driver at the time of an abnormal situation where the throttle is open against the driver's will. Is considered high. On the other hand, in a region where the vehicle speed is relatively high, it is desirable to obtain a sufficient vehicle deceleration effect by stopping combustion of the engine in order to avoid danger.

  Therefore, in the present embodiment, when the throttle opening abnormality occurs in the vehicle running state, when the vehicle speed decreases due to the combustion stop of the engine 10, the engine rotation speed for determining the combustion return is determined as the vehicle speed decreases. The amount of deviation between the first determination value T1 and the second determination value T2 that is the engine rotation speed for determining the combustion stop is reduced. Specifically, the lower the vehicle speed is, the lower the second determination value T2 is set. I am going to do that. In other words, in the high vehicle speed range, the engine rotation speed change from the combustion stop to the combustion recovery is increased so that the vehicle deceleration effect can be fully exerted, while in the low vehicle speed range, the engine rotation speed is changed in small increments. Thus, the fluctuation of the vehicle speed due to the fluctuation of the rotation is reduced. Further, when the deviation amount is reduced, the second determination value T2 is changed, and the first determination value T1 is set to a constant value so that the first determination value T1 is held at the minimum rotation speed at which engine stall does not occur. Like to do.

  Next, engine control when a throttle opening abnormality occurs in the vehicle running state will be described with reference to the flowchart of FIG. This process is executed by the ECU 40 at predetermined intervals.

  In FIG. 2, in step S <b> 11, for example, it is determined based on the detection value of the vehicle speed sensor 35 whether the vehicle is in a traveling state. If the vehicle is running, the process proceeds to step S12, and it is determined whether or not a throttle opening abnormality has occurred. Here, it is determined whether or not the throttle valve 13 is open and the brake pedal 33 is depressed. Whether the throttle valve 13 is open is determined by determining whether the throttle opening detected by the throttle opening sensor 17 is larger than the threshold value a. The brake pedal 33 is depressed by determining whether or not the brake depression amount detected by the brake sensor 34 is larger than the threshold value b.

  If the throttle opening abnormality has occurred, the process proceeds to step S13 to determine whether or not the throttle opening abnormality flag f1 is on. The throttle opening abnormality flag f1 is a flag that is turned on when a throttle opening abnormality is detected. When the throttle opening abnormality flag f1 is off, the process proceeds to step S14, where the throttle opening abnormality flag f1 is turned on and fuel injection is stopped. Further, the vehicle speed and the engine rotation speed at the time when the output restriction is started in accordance with the detection of the throttle opening abnormality are stored as the vehicle speed reference value Va and the rotation reference value Na, respectively.

  In the engine output limitation in step S14, the ignition timing is first changed to the retard side before the fuel injection is stopped, and the fuel injection is stopped after the ignition timing is changed to the retard side. As a result, the output of the engine 10 is gradually reduced to suppress the occurrence of torque shock (the same applies to the fuel cut in step S19 below).

  Now, when steps S11 to S13 are YES, the process proceeds to step S15, where the engine rotation speed (actual rotation speed) detected by the crank angle sensor 31 is based on the first determination value T1 that is the engine rotation speed for combustion return determination. It is determined whether it is low. The first determination value T1 is set to an engine rotational speed (for example, 700 to 800 rpm) during idle operation or a value slightly higher than that.

  If the actual rotational speed is lower than the first determination value T1, the process proceeds to step S16 to determine whether or not the fuel is being cut. If the fuel is being cut, the fuel cut of the engine 10 is canceled in step S17 (fuel injection). Resume). On the other hand, when the actual rotation speed is equal to or higher than the first determination value T1, the process proceeds to step S18, and based on the vehicle speed detected by the vehicle speed sensor 35, the second determination value T2 that is the engine rotation speed for fuel injection stop determination is set. Set.

  FIG. 3 is a map showing an example of the relationship between the vehicle speed and the second determination value T2. In the present embodiment, a change amount (inclination α) of the second determination value T2 per unit change amount of the vehicle speed is determined and stored in advance, and the inclination α, the vehicle speed reference value Va and the rotation reference stored in step S14. The relationship between the vehicle speed and the second determination value T2 is determined using the value Na. Specifically, as shown in FIG. 3, as the vehicle speed is lower than the vehicle speed reference value Va, the second determination value T2 is set lower than the rotation reference value Na. In other words, the lower the vehicle speed, the smaller the amount of deviation between the first determination value T1 and the second determination value T2.

  Returning to FIG. 2, in step S19, the engine rotation speed (actual rotation speed) detected by the crank angle sensor 31 is compared with the second determination value T2 calculated in step S18. At this time, if the actual rotational speed is higher than the second determination value T2, the process proceeds to step S20 to determine whether or not the fuel is being cut. If not, the fuel injection is stopped in step S21.

  Next, a specific mode of engine control according to the present embodiment will be described with reference to the time chart of FIG. In the figure, (a) shows the change in opening / closing of the throttle valve, (b) shows the change in depression / deactivation of the brake pedal 33, (c) shows the change in ON / OFF of the throttle opening abnormality flag f1, and (d) shows the vehicle speed. (E) shows the change in engine speed, and (f) shows the change in combustion cut / fuel cut release.

  In FIG. 4, when a throttle opening abnormality is detected in the vehicle running state, a fuel cut (F / C) is performed, and the engine speed decreases. When the engine rotation speed falls below the first determination value T1 with this rotation drop, the fuel cut is canceled at the timing t11, and the engine rotation speed starts to increase, thereby reducing the degree of vehicle speed reduction. Note that FIG. 3 illustrates a case where the change in the vehicle speed becomes substantially zero due to the increase in the engine rotation speed accompanying the release of the fuel cut.

  Then, when the engine speed exceeds the second determination value T2 with the release of the fuel cut, the fuel cut is performed again at timing t12, and the engine speed changes from increasing to decreasing. While the throttle opening abnormality is detected, the fuel cut of the engine 10 and the release of the fuel cut are repeatedly performed in this way, so that the decrease and increase of the engine speed are repeated. As a result, the engine stall is avoided while the output of the engine 10 is restricted when the throttle is abnormal.

  In FIG. 3, the vehicle speed gradually decreases with the braking force and the fuel cut, and the second determination value T2 is gradually changed to the low rotation side as the vehicle speed decreases. As a result, in the high vehicle speed range, the range of change in the engine rotation speed from the fuel cut to the fuel cut return becomes large, and the vehicle deceleration effect due to the combustion stop of the engine is sufficiently exhibited. Further, in the low vehicle speed range, the fluctuation range of the engine rotation speed accompanying the fuel cut and the fuel cut return is reduced, and the repetition of acceleration and deceleration of the vehicle is suppressed.

  If the depression of the brake pedal 33 is released after the throttle opening abnormality flag f1 is turned on, it is preferable to release the fuel cut in order to release the output limitation of the engine 10 on the assumption that the driver intends to travel.

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

  When the driver is depressing the accelerator pedal and the throttle valve is open, but the throttle valve is not closed and the throttle is not closed, engine combustion is stopped. Since the engine output is limited, the vehicle can be prevented from falling into a dangerous state. Further, at that time, the engine is restarted and stopped in accordance with the engine rotation speed, so that the engine stall can be avoided and the vehicle can run.

  In particular, in the present embodiment, when the engine combustion is stopped with the detection of the throttle opening abnormality, and the vehicle speed is reduced due to the combustion stop, the amount of deviation between the first determination value T1 and the second determination value T2 is calculated. In order to reduce the vehicle speed as the vehicle speed decreases, fluctuations in the engine rotation speed due to repeated combustion / combustion of the engine 10 can be gradually reduced as the vehicle speed decreases. Thereby, it can suppress that the stability of a vehicle falls.

  When the amount of deviation between the first determination value T1 and the second determination value T2 is reduced, the second determination value is changed to the low rotation side, and the first determination value T1 is not changed. 1 determination value T1 can be held at the minimum rotation speed at which engine stall does not occur.

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

  In FIG. 3, the case where the change in the vehicle speed is substantially zero due to the increase in the engine speed accompanying the release of the fuel cut is illustrated, but the vehicle speed increases with the release of the fuel cut depending on the throttle opening when the abnormality occurs. It is possible. In view of this point, the second determination value T2 may be configured to hold the second determination value T2 when the vehicle speed increases. That is, in the fuel cut state, the second determination value T2 may be lowered as the vehicle speed decreases, and in the fuel cut release state, the second determination value T2 may be maintained as the current value regardless of the change in the vehicle speed. .

  In the above embodiment, the second determination value T2 is set according to the vehicle speed. However, in view of the fact that the vehicle speed decreases in the fuel cut state, the second determination value T2 is decreased according to the elapsed time Tc from the start of fuel cut. It is good also as a structure changed to a rotation side. In this case, the second determination value T2 is lowered as the elapsed time Tc is longer. Further, the elapsed time Tc may be the elapsed time from the timing (t10 in FIG. 4) when the fuel cut is started in accordance with the detection of the throttle opening abnormality, or the engine rotational speed has exceeded the second determination value T2. Accordingly, the elapsed time from the timing of starting fuel cut (t12 in FIG. 4) may be used.

  In the above embodiment, when the second determination value T2 is changed based on the vehicle speed, the second determination value T2 is reduced as the vehicle speed decreases by using the map of FIG. The configuration for changing is not limited to the above. For example, as shown in FIG. 5, the second determination value T2 may be switched between large and small based on a comparison between the vehicle speed and the determination value Vth. That is, in FIG. 5, when the throttle opening abnormality is detected at timing t20 in the vehicle running state, the second determination value T2 is set to Nm when the vehicle speed is equal to or higher than Vth, and the second determination value when the vehicle speed is lower than Vth. T2 is set to Nn smaller than Nm. At this time, the vehicle speed determination value Vth may be an upper limit value of the vehicle speed at which the vehicle can be stopped when the brake pedal 33 is depressed. In this case, priority can be given to suppression of fluctuations in the vehicle speed in a low vehicle speed range in which the vehicle can be stopped by the braking force, and as a result, a decrease in vehicle stability can be suppressed.

  In FIG. 5, when the vehicle speed is less than the determination value Vth, the second determination value T2 is constant at Nn. However, in the region where the vehicle speed is less than the determination value Vth, the second determination value T2 is decreased as the vehicle speed decreases. It is good.

  In the above embodiment, the vehicle speed and the engine rotation speed at the time when the output restriction is started in accordance with the detection of the throttle opening abnormality are stored as the vehicle speed reference value Va and the rotation reference value Na, respectively, and these vehicle speed reference value Va and rotation reference value are stored. Although the second determination value T2 is set based on Na, the second determination value T2 may be set using a map stored in advance, for example, without using the vehicle speed reference value Va and the rotation reference value Na. Good.

  In the above embodiment, the second determination value T2 is changed by changing the second determination value T2 to the low rotation side when the deviation amount between the first determination value T1 and the second determination value T2 is reduced. Instead of or together with the second determination value T2, the first determination value T1 may be changed to the high rotation side.

  When the combustion of the engine 10 is stopped to limit the engine output, a configuration is adopted in which a transition from a partial cylinder stop for stopping the combustion of some cylinders to a full cylinder stop for stopping the combustion of all cylinders is performed. In this case, the torque change from the start of engine combustion stop to the stop of combustion for all cylinders becomes more gradual, and the occurrence of shock can be more suitably suppressed when the engine output is limited.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 13 ... Throttle valve, 14 ... Accelerator pedal, 15 ... Cable, 16 ... Throttle actuator, 17 ... Throttle opening sensor, 21 ... Injector, 25 ... Spark plug, 32 ... Accelerator sensor, 33 ... Brake pedal, 34 ... brake sensor, 35 ... vehicle speed sensor, 40 ... ECU (abnormality detection means, output limiting means, combustion control means, deviation amount changing means).

Claims (3)

It is applied to an in-vehicle engine equipped with a mechanical throttle valve that adjusts the intake amount of the engine by being mechanically driven by the driver's depressing operation force on the accelerator pedal,
An abnormality detection means for detecting an abnormality in throttle opening, which is an abnormality in which the throttle valve remains open while the driver depresses the accelerator pedal in a vehicle running state;
An output limiting means for stopping the combustion of the engine and limiting the output of the engine when the abnormality in the throttle opening is detected by the abnormality detecting means;
When the engine speed is lower than the first determination value after the engine is stopped in the vehicle running state by the output limiting means, the engine is returned to combustion, and after the combustion return, the engine speed is changed to the first value. Combustion control means for performing combustion return stop processing for stopping the combustion when higher than the second determination value on the higher rotation side than the first determination value;
Wherein when the vehicle speed due to the stop of the engine combustion is decreased by the combustion recovery stop processing, by lowering the second judgment value while fixing the first judgment value, entailment before Symbol first determination value to the vehicle speed decreases And a deviation amount changing means for reducing the deviation amount between the second determination value and the engine control device.   The engine control apparatus according to claim 1, wherein the deviation amount changing unit reduces the deviation amount by reducing the second determination value as the vehicle speed decreases.   3. The engine control device according to claim 1, wherein the abnormality detection unit detects that the brake pedal is depressed when the throttle valve is open as the throttle opening abnormality. 4.

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