JP6197275B2 - Engine control device - Google Patents

Description

  The present invention relates to a control device that controls the operating state of an engine in order to raise the temperature of a catalyst installed in an exhaust passage to an activation temperature or higher.

  The performance of the exhaust purification catalyst installed in the exhaust passage is degraded when the temperature is lower than the activation temperature. Therefore, after starting the engine, it is important to quickly raise the temperature of the catalyst and maintain it at the activation temperature.

  In order to properly purify the exhaust gas at the initial stage of starting the vehicle when the engine temperature is "warm", i.e., when the temperature of the cooling water is above a certain temperature and the catalyst temperature drops while idling In addition, Patent Document 1 describes that when the depression of the brake pedal is detected, the ignition timing is retarded and the throttle valve opening is increased. Further, in Patent Document 1, when a state in which the catalyst temperature is equal to or lower than a predetermined temperature is continuously detected for a certain period of time or more in the idling state, the ignition timing is retarded and the throttle valve opening is increased. . By retarding the ignition timing, the catalyst temperature is prevented from decreasing. In Patent Document 1, a decrease in torque due to retarding the ignition timing is compensated by increasing the opening of the throttle valve. Then, at the same time as detecting that the accelerator pedal is depressed, the ignition timing is changed to the advance side which is the original ignition timing.

  Also, when the engine is started in a “cold state (cold state)”, that is, in a state where the cooling water temperature is below a certain temperature, the engine rotational speed is set to the target rotational speed during idling while promoting warm-up of the catalyst. Patent Document 2 describes that the engine is controlled so that the air-fuel ratio is not leaned and the generation amount of HC (hydrocarbon) is not increased. According to Patent Document 2, when the engine rotation speed reaches the target rotation speed during idling after cranking, the ignition timing is retarded stepwise (at a stroke) from the ignition timing for starting to the ignition timing for promoting catalyst warm-up. (Retard). Further, when the engine speed reaches the target rotational speed during idling, the engine rotational speed is supplied to the combustion chamber so that the intake air amount necessary for maintaining the engine rotational speed at the target rotational speed during idling is supplied to the combustion chamber. Starts to open the throttle valve a certain time before reaching the target rotational speed during idling. After the engine rotation speed reaches the target rotation speed during idling, the fuel injection amount is increased until the rate of change in intake pressure or intake port intake flow rate falls within a predetermined range.

  In the idling operation at the cold start of the engine, the ignition timing is retarded to promote warming up of the exhaust gas purification catalyst, and the engine is driven by the motor or generator integrated with the starter and alternator. Patent Document 3 discloses an engine that performs torque assist that compensates for insufficient torque to ensure engine stability.

  Patent Document 4 describes three methods for reducing HC (hydrocarbon) emissions before the catalyst reaches the activation temperature. According to Patent Document 4, the first method is a method of retarding the ignition timing. The second method is a method in which the valve overlap amount at which the intake valve and the exhaust valve are simultaneously opened by the valve timing changing mechanism is increased to a predetermined value or more. When the valve overlap amount is increased, the combustion gas is blown back to the intake port, so that the HC contained in the combustion gas is also blown back to reduce the HC emission amount. The third method is to make the air-fuel ratio lean. Reducing fuel reduces the amount of carbon that is the source of HC and reduces HC emissions. However, both methods are described as being difficult to realize immediately after the cold start of the engine. It has been proposed to reduce the flow rate of air supplied to the engine until a certain amount of time has elapsed after startup, that is, by reducing the opening of the throttle valve, thereby reducing the amount of exhaust and reducing the amount of HC emissions during cold start. ing.

Japanese Patent No. 4023467 Japanese Patent No. 4872655 Japanese Patent No. 3846349 JP 2005-9474 A

  When the ignition timing is retarded so that the temperature of the catalyst exceeds the activation temperature, the throttle opening is small when the retard amount is small, so the engine speed for idling can be adjusted by changing the retard amount. it can. However, if the amount of retard required to raise the temperature of the catalyst becomes too large, the opening of the throttle will also increase. Therefore, it is attempted to adjust the engine speed for idle operation by adjusting the amount of retard and the opening of the throttle. Then, the responsiveness is dull and difficult to stabilize.

  In Patent Document 3, torque assist is performed in order to compensate for the shortage of the engine target torque associated with retarding the ignition timing, but no attempt is made to stabilize the engine speed. Patent Document 4 aims to reduce the total amount of HC (hydrocarbon) emission from the cold start to the completion of the catalyst warm-up operation. As in Patent Document 3, the engine speed is stabilized. It is not considered about making it.

  Therefore, the present invention provides a control device that stabilizes the engine speed of idle operation with existing equipment when the temperature of the catalyst immediately after the cold start is raised to the activation temperature.

The control device according to the present invention includes a rotation speed measurement means for measuring the rotation speed of the engine, a coolant temperature detection means for the engine cooling water, an ignition plug, an electric load means for applying a load to the engine output shaft, And a variable valve timing mechanism for adjusting an overlap amount at the opening timing of the exhaust valve. Then, the control device, after is retarded ignition timing of the spark plug in the idle operation immediately after the cold start to the target ignition timing, the rotational speed is first with respect to the target rotational speed detected by the rotational speed measuring means If it exceeds the variation range, depending on whether the speed is greater or less than the target rotational speed, the steps of adjusting to control at least one of the overlapping amount of the load or the variable valve timing mechanism due to an electric load means The rotation speed is controlled so that the rotation speed falls within the first fluctuation range with respect to the target rotation speed .

At this time, the control device, if it exceeds the second variation range larger than the rotation speed is the first fluctuation range, according to the load or combustible valve timing mechanism according to the electric load means the throttle opening disposed in the intake passage Prior to the adjustment of the overlap amount, adjustment is performed preferentially, and the rotational speed is controlled to be larger than the first fluctuation range and smaller than the second fluctuation range. Further, when the rotation speed is within the second fluctuation range and exceeds the upper limit of the first fluctuation range, the load of the electric load means is increased. Furthermore, when the lower limit of the first fluctuation range is exceeded, the overlap amount by the variable valve timing mechanism is reduced.

  Further, the control device increases the throttle opening in proportion to the amount of change when the ignition timing is gradually retarded toward the target ignition timing. The throttle opening at this time is set corresponding to the water temperature detected by the water temperature detecting means and the retarded ignition timing.

  According to the control device of the present invention, the load of the electric load means or the overlap amount by the variable valve timing mechanism is adjusted in order to control the engine speed within the first fluctuation range with respect to the target speed. The electric load means and the variable valve timing mechanism, which are adjusted to control the rotational speed, are the configurations provided in the existing engine, and the catalyst immediately after the cold start is avoided while avoiding further complication of the engine. It is possible to accurately adjust the engine speed of the idling operation in the catalyst temperature increase mode in which the temperature is increased to the activation temperature with respect to the first fluctuation range of the target rotation speed.

  When the engine speed exceeds the second fluctuation range that is larger than the first fluctuation range with respect to the target speed, the opening degree of the throttle installed in the intake passage is preferentially adjusted, and the rotation speed is set to the first speed. According to the control device of the invention that controls the engine speed to be larger than the fluctuation range and smaller than the second fluctuation range, the engine speed can be quickly adjusted to the target speed.

  Further, according to the control device of the invention for increasing the load of the electric load means when the rotation speed is within the second fluctuation range and exceeds the upper limit of the first fluctuation range, the fuel injection amount and the air amount are changed. The engine speed can be adjusted to the target speed without causing the exhaust gas properties to deteriorate.

  In addition, when the lower limit of the first fluctuation range is exceeded, according to the control device of the invention that reduces the overlap amount by the variable valve timing mechanism, the engine speed is set to the target speed while improving the combustion by reducing the internal EGR. Can be adjusted to a number.

  Also, according to the control device of the invention that increases the throttle opening in proportion to the amount of change when the ignition timing is gradually retarded toward the target ignition timing, the engine is operated by increasing the compression pressure in accordance with the ignition timing. Can prevent misfire. Further, it is possible to respond quickly when a change occurs in the engine speed, and to prevent a large fluctuation from the target speed. According to the control device of the invention that sets the throttle opening at this time corresponding to the water temperature detected by the water temperature detecting means and the retarded ignition timing, the engine speed can be easily controlled.

  Since the controllability is improved in any case, the engine speed of idle operation can be stabilized with existing equipment when raising the catalyst immediately after the cold start to the activation temperature, and this control device is provided. The drivability of the vehicle is improved.

The block diagram of an engine provided with the control apparatus which concerns on this invention. FIG. 2 is a flowchart of control performed by the control device of FIG. 1 when the engine is cold started. FIG. The time chart which shows the state of each part of the engine controlled by the flowchart of FIG.

  A control device 10 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. This control device 10 stabilizes the rotational speed Ne of the engine 1 when the temperature of the catalyst is raised to the activation temperature in the idle operation immediately after the cold start of the engine 1 which is an internal combustion engine. 1 includes a cylinder block 2, an intake passage 3, an exhaust passage 4, a cylinder head 5, a piston 6, an output shaft (crankshaft) 7, an alternator 8, an intake valve 31, A throttle 32, an exhaust valve 41, a catalyst 42, a spark plug 51, and a variable valve timing (VVT) mechanism 52 are included.

  The cylinder block 2 has a circulation path 21 formed so as to surround the combustion chamber 20 formed between the cylinder head 5 and the piston 6 in order to flow the cooling water W. The water temperature sensor 22 is attached to the cylinder block 2 as water temperature detection means, and measures the temperature of the cooling water W. The throttle 32 is installed in the middle of the intake passage 3 and its opening degree is adjusted by a drive device such as a servo motor. The opening degree of the throttle 32 is detected by a throttle position sensor 33.

  A rotation angle sensor 71 is installed on the output shaft 7. The rotation angle sensor 71 functions as a rotation speed measuring unit that detects the rotation angle of the output shaft 7 and measures the rotation speed of the output shaft 7, that is, the rotation speed Ne of the engine 1. The catalyst 42 is installed in the middle of the exhaust passage 4. In order to estimate the temperature of the catalyst 42, a catalyst temperature sensor 43 is installed in the exhaust passage 4 upstream of the catalyst 42.

  The variable valve timing mechanism 52 is installed in the cylinder head 5 and can individually change the lift amount and the opening timing of the intake valve 31 and the exhaust valve 41 by changing the lever ratio of the rocker arm. Using this function, the variable valve timing mechanism 52 adjusts the overlap amount of the opening timing of the intake valve 31 and the exhaust valve 41. The alternator 8 is connected to the output shaft 7 and functions as an electric load means for applying a load to the output shaft 7 by electromagnetic resistance when generating power.

  The control device 10 is an electronic control unit (ECU) that controls the operation of the engine 1 and performs signal detection and operation control of sensors installed in each part of the vehicle on which the engine 1 is mounted. The control device 10 is connected to the rotation angle sensor 71, the water temperature sensor 22, the spark plug 51, the throttle 32, the alternator 8, and the variable valve timing mechanism 52. The control device 10 calculates the rotation speed Ne of the engine 1 based on the signal output from the rotation angle sensor 71, adjusts the ignition timing of the spark plug 51, and the intake valve 31 and the exhaust by the variable valve timing mechanism 52. Adjustment of the opening timing and overlap amount of the valve 41 and adjustment of the opening degree of the throttle 32 are performed.

  When the engine 1 is started when the engine 1 is in a cold state lower than a certain temperature, the temperature of the catalyst 42 is increased by retarding the ignition timing of the spark plug 51 immediately after starting to raise the exhaust temperature. Raise to activation temperature. In order to stabilize the rotational speed Ne of the engine 1 during idling at this time, the control device 10 adjusts at least one of the opening degree of the throttle 32, the load of the alternator 8, and the overlap amount by the variable valve timing mechanism 52. Control to do. This control will be described in more detail with reference to FIGS.

  As shown in FIG. 2, when the engine 1 is started, the control device 10 determines whether or not the vehicle is stopped based on the signal from the vehicle speed sensor in order to determine whether or not the engine 1 is cold start. Determine (S1). When it is determined that the vehicle is stopped, it is determined whether the accelerator pedal is not operated, that is, whether the idle switch (ID-SW) is ON (S2). When the idle switch is OFF, the driver is stepping on the accelerator pedal, and the engine 1 is intentionally increasing the rotational speed Ne. If the idle switch is ON, it is further determined whether the water temperature detected by the water temperature sensor 22 is equal to or lower than a predetermined value, that is, whether the engine 1 is cold (S3).

  When the engine 1 is in a cold state, a light lean mode is started in which the amount of fuel is reduced in the compression stroke so that unburned fuel is not discharged (S4). When the light lean mode is started, the control device 10 gradually delays, that is, retards, the ignition timing of the spark plug 51 with respect to the top dead center of the piston as shown in FIG. 3 (S5).

  The control device 10 has a map for setting the opening degree of the throttle 32 using the water temperature detected by the water temperature sensor 22 and the retard amount of the ignition timing as variables, and with changes in the water temperature and the retard amount. The throttle opening is adjusted (S6). In this control, as shown in FIG. 3, the throttle opening is set to increase as the retard amount increases.

  In addition, the engine 1 of this embodiment includes a variable valve timing mechanism 52. When the variable valve timing mechanism 52 is provided, the opening degree of the throttle 32 varies depending on the overlap amount. Therefore, the control device 10 corrects the opening degree of the throttle 32 according to the overlap amount obtained from the variable valve timing mechanism 52 (S7).

  While increasing the opening of the throttle 32 while retarding the ignition timing of the spark plug 51, it is determined whether the ignition timing of the spark plug 51 has reached a preset target ignition timing (S8). If the target ignition timing has not been reached, the process returns to S5, where the ignition timing of the spark plug 51 is continuously retarded, and the opening of the throttle 32 is increased accordingly. Further, in accordance with the timing for retarding the ignition timing, the variable valve timing mechanism 52 is advanced to the target phase angle on the intake side and is retarded to the target phase angle on the exhaust side. The magnitude of advance or retard varies depending on the magnitude of the valve overlap amount.

  When the ignition timing reaches the target ignition timing, the control device 10 determines whether or not the rotational speed Ne of the engine 1 is within the first fluctuation range P1 with respect to the target rotational speed Me (S9). When it is in the first fluctuation range P1, the operation state is maintained as it is. If the rotational speed Ne is not within the first fluctuation range P1, it is further determined whether it is within the second fluctuation range P2 that is larger than the first fluctuation range P1 (S10). When the rotational speed Ne of the engine 1 exceeds the second fluctuation range P2 of the target rotational speed Me, the control device 10 makes the rotational speed Ne within the first fluctuation range P1 of the target rotational speed Me. Adjustment is made according to the opening of the throttle 32.

  At this time, it is determined whether the rotational speed Ne is larger than the target rotational speed Me (S11). When the rotational speed Ne exceeds the second fluctuation range P2 toward the larger side with respect to the target rotational speed Me, that is, when the rotational speed Ne is too large, the opening degree of the throttle 32 is decreased (S12), Reduce Ne. Further, when the rotational speed Ne exceeds the second fluctuation range P2 toward the smaller side relative to the target rotational speed Me, that is, when the rotational speed Ne is too small, it is confirmed whether the throttle 32 is fully opened (S13). After that, if there is still a margin in the opening of the throttle 32, the rotational speed Ne is increased by increasing the opening of the throttle 32 (S14). If the throttle 32 has already been fully opened, the throttle 32 cannot be opened any more in order to increase the rotational speed Ne. Therefore, the load of the alternator 8 or the overlap amount by the variable valve timing mechanism 52 can be reduced. By adjusting (VOL), the rotation speed Ne of the engine 1 is adjusted to be increased. Adjustment of the rotational speed Ne by the alternator 8 and the variable valve timing mechanism 52 is the same as when the rotational speed Ne is smaller than the target rotational speed Me and is between the first fluctuation range P1 and the second fluctuation range P2. It is. This will be described later.

  In S10, when the rotation speed Ne is within the second fluctuation range P2 of the target rotation speed Me, that is, when the rotation speed Ne is between the first fluctuation range P1 and the second fluctuation range P2, the alternator 8 Or the overlap amount (VOL) is adjusted by the variable valve timing mechanism 52 so that the rotational speed Ne is within the first fluctuation range P1 of the target rotational speed Me. At this time, the control procedure differs depending on whether the rotational speed Ne of the engine 1 is larger or smaller than the target rotational speed Me. Therefore, the control device 10 determines whether the rotational speed Ne is larger than the target rotational speed Me (S15).

  When the rotational speed Ne is greater than the target rotational speed Me, when the first fluctuation range P1 is equal to or greater than the second fluctuation range P2, the control device 10 sets the overlap amount VOL of the variable valve timing mechanism 52 in advance. It is determined whether the initial value VOLp has changed (S16). When the overlap amount VOL does not change from the initial value VOLp, the load Ne of the alternator 8 is increased (S17), thereby reducing the rotational speed Ne of the engine 1. On the other hand, when the overlap amount VOL is changed from the initial value VOLp, the overlap amount VOL is increased (S18) to reduce the rotational speed Ne.

  In S15, when the rotational speed Ne is smaller than the target rotational speed Me and is within the first fluctuation range P1 and the second fluctuation range P2, the control device 10 confirms whether the load on the alternator 8 is zero (S19). ) When the load on the alternator 8 is zero, the alternator 8 cannot increase the rotational speed Ne. Therefore, the variable valve timing mechanism 52 decreases the overlap amount VOL (S20) and increases the rotational speed Ne. If the load on the alternator 8 is not zero, the rotational speed Ne is increased by reducing the load on the alternator 8 (S21). The operations in S19 to S21 correspond to the case where the throttle 32 is fully opened in S13.

  As described above, when the rotational speed Ne is adjusted by at least one of the opening degree of the throttle 32, the overlap amount VOL adjusted by the variable valve timing mechanism 52, and the load of the alternator 8, the control device 10 It is determined whether or not it is within the duration of the mode (S22). If it is within the time, the process returns to S9 so that the rotational speed Ne during idling is stabilized within the first fluctuation range P1 of the target rotational speed Me. To control. If the duration has passed, the light lean mode is terminated (S23).

  When the light lean mode ends, the variable valve timing mechanism 52 is returned to the state before the light lean mode is started on both the intake side and the exhaust side. The retard amount of the throttle opening and the ignition timing of the fire plug 51 is returned to a predetermined position as soon as the light lean mode ends, that is, the throttle opening is reduced to a predetermined value, and the retard amount is advanced to a predetermined value. Let Thereafter, since the actual intake air amount decreases as the throttle opening is reduced, the ignition timing is gradually advanced in accordance with this so that the engine speed does not increase. As a result, the engine speed Ne gradually decreases toward the normal target idle speed and shifts to a normal idle operation (S24).

  As described above, the control device 10 determines the rotational speed Ne of the engine 1 using at least one of the opening degree of the throttle 32, the overlap amount of the variable valve timing mechanism 52, and the load of the alternator 8 at the cold start. Control is performed so that the target rotational speed Me is within the first fluctuation range P1. Since the rotation speed Ne is adjusted by means according to the operation state of the engine 1, the engine rotation in the idle operation in the catalyst temperature raising mode can be stabilized with high accuracy.

  In particular, when the engine speed exceeds a second fluctuation range that is larger than the first fluctuation range with respect to the target speed, the engine speed can be quickly adjusted to the target speed by adjusting the throttle opening. Can be adjusted.

  Further, when the rotational speed is within the second fluctuation range and exceeds the upper limit of the first fluctuation range, the engine speed is increased without changing the fuel injection amount or the air amount by increasing the load of the electric load means. Can be adjusted to the target rotational speed, and the exhaust gas properties are not deteriorated.

  Further, when the rotational speed is within the second fluctuation range and exceeds the lower limit of the first fluctuation range, the amount of overlap by the variable valve timing mechanism is reduced, thereby reducing internal EGR and improving combustion. The engine speed can be adjusted to the target speed.

  Furthermore, by increasing the throttle opening in proportion to the amount of change when the ignition timing is gradually retarded toward the target ignition timing, the compression pressure is increased in accordance with the ignition timing to prevent engine misfire. Can do. Further, it is possible to respond quickly when a change occurs in the engine speed, and to prevent a large fluctuation from the target speed. According to the control device of the invention that sets the throttle opening at this time corresponding to the water temperature detected by the water temperature detecting means and the retarded ignition timing, the engine speed can be easily controlled.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 10 ... Control apparatus, 7 ... Output shaft, 71 ... Rotation angle sensor, 8 ... Alternator (electric load means), 22 ... Water temperature sensor (water temperature detection means), 31 ... Intake valve, 41 ... Exhaust valve, 51 ... ignition plug, 52 ... variable valve timing mechanism, Ne ... (engine) speed, Me ... target speed, P1 ... first fluctuation range, P2 ... second fluctuation range, VOL ... overlap amount.

Claims (5)

A rotational speed measuring means for measuring the rotational speed of the engine;
Means for detecting the coolant temperature of the engine;
Spark plugs,
Electric load means for applying a load to the output shaft of the engine;
A control device connected to a variable valve timing mechanism that adjusts an overlap amount of the opening timing of the intake valve and the exhaust valve,
In the idling operation immediately after the cold start, the control device retards the ignition timing of the spark plug to the target ignition timing, and then the rotational speed detected by the rotational speed measuring means is a first relative to the target rotational speed. When the fluctuation range is exceeded, at least one of the load by the electric load means or the overlap amount by the variable valve timing mechanism is adjusted according to whether the rotation speed is larger or smaller than the target rotation speed The control apparatus is characterized in that the control procedure is varied to control the rotational speed so that it falls within the first fluctuation range of the target rotational speed. When the rotational speed exceeds a second fluctuation range that is larger than the first fluctuation range, the control device determines the opening of the throttle installed in the intake passage as a load by the electric load means or the variable valve timing mechanism. Prior to the adjustment of the overlap amount by the control, and the rotational speed is controlled to be larger than the first fluctuation range and smaller than the second fluctuation range. The control device according to claim 1. 3. The control device according to claim 2, wherein when the rotational speed is within the second fluctuation range and exceeds an upper limit of the first fluctuation range, the load of the electric load means is increased. . The overlap amount by the variable valve timing mechanism is reduced when the rotational speed is within the second fluctuation range and exceeds a lower limit of the first fluctuation range. Item 4. The control device according to Item 3. The opening degree of the throttle is increased in proportion to a change amount that gradually retards the ignition timing toward the target ignition timing. Control device.

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