JP2005076579A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device for preventing the knocking of an engine due to too early ignition at a high temperature in a low-speed and high-load condition and improving the torque. <P>SOLUTION: The engine control device comprises operated condition detecting means 32, 33, 34 for detecting the operated condition of the engine 1, an actual compression ratio varying means 8a for varying an actual compression ratio in a combustion chamber of the engine, and a control means 31 for determining the operated condition of the engine from detection information for the operated condition and controlling the operation of the actual compression ratio varying means 8a so that the actual compression ratio is kept relatively high before the elapse of a preset time in the low-speed and high-load condition of the engine and it is lowered after the elapse of the preset time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine control device capable of changing an actual compression ratio of an engine.

  Conventionally, in knocking control in an internal combustion engine such as a gasoline engine, occurrence of knocking is determined based on a signal from a knock sensor provided in the engine. When it is determined that knocking has occurred, the ignition timing is retarded to suppress knocking. However, retarding the ignition timing may cause deterioration in fuel consumption, and therefore, knocking control instead of this has been desired.

  Therefore, in Patent Document 1, the variable timing mechanism is controlled so as to retard the opening / closing timing of the intake valve in the low-rotation / medium-load operating region of the engine where knocking is likely to occur, and after being once introduced into the combustion chamber. A technique has been proposed in which the effective compression ratio is reduced by increasing the intake air to escape. That is, a technique for suppressing knocking by controlling the valve timing is disclosed.

JP-A-6-257477

  In recent years, the compression ratio tends to increase in order to improve fuel consumption, and therefore knocking is likely to occur. In particular, when the engine temperature is high, knocking is likely to occur, so it is necessary to lower the actual compression ratio. In addition, when the engine is in a high temperature state for a long time and the low rotation and high load operation state continues, there is a concern that strong knocking may occur due to pre-ignition due to engine temperature.

  Patent Document 1 discloses a technique for reducing the compression ratio in a low-revolution medium load operation region, which is a region where knocking is likely to occur. However, the compression ratio is simply reduced in a low-revolution medium load operation region. However, there is a problem that countermeasures against the torque reduction that occurs with the reduction in the compression ratio are insufficient.

  The present invention pays particular attention to the fact that pre-ignition does not occur because the combustion chamber temperature does not rise immediately after high load, and the engine is at low speed, high load and high temperature. An object of the present invention is to provide an engine control device that can prevent knocking due to premature ignition in the engine and secure torque.

  The present invention relates to an operating state detecting means for detecting an operating state of the engine, an actual compression ratio varying means for changing an actual compression ratio in the combustion chamber of the engine, and an engine operating state based on detection information from the operating state detection. And a control means for controlling the operation of the actual compression ratio variable means so as to lower the actual compression ratio when the engine is running at a low speed and high load for a predetermined period. It is said. For this reason, until the engine is running at a low speed and a high load for a predetermined time, the actual compression ratio in the combustion chamber is relatively high and the volumetric effect is relatively large, and the torque is maintained. When the predetermined time has elapsed, the actual compression ratio in the combustion chamber is reduced and knocking is prevented.

  If the actual compression ratio variable means is a variable timing mechanism that can vary the valve opening timing of the intake valve that opens and closes the intake port leading to the combustion chamber, it can be changed when the engine is in a low rotation and high load state using the control means. The valve opening timing by the timing mechanism is controlled to move to the retard side, and the amount of movement to the retard side is suppressed before a predetermined period has elapsed. In this case, until the predetermined period elapses, the opening of the intake valve before and after the transition from the exhaust stroke to the intake stroke becomes relatively quick, so that the volumetric efficiency of the intake air amount increases and the actual compression ratio is reduced. Is suppressed. After a predetermined period of time, the intake valve closes slowly before and after the transition from the intake stroke to the compression stroke, so the intake air that tends to escape after being once introduced into the combustion chamber increases, reducing volumetric efficiency and actual compression. The ratio becomes smaller.

  A temperature detecting means for detecting the temperature of the engine; and when the control means judges the water temperature state from the detection information from the temperature detecting means and controls the movement of the variable timing mechanism to the retard side in response to the rise in the water temperature, The actual compression ratio in the combustion chamber after the passage of time is reduced as the water temperature rises. An ignition means for performing ignition in the combustion chamber is provided, and the torque increases when the control means advances the ignition timing by the ignition means in accordance with the reduction control of the actual compression ratio.

  According to the present invention, the torque is maintained in a state in which the actual compression ratio in the combustion chamber is high and the volumetric efficiency is large until the low engine speed and the high load state elapse for a predetermined time. The actual compression ratio in the combustion chamber is reduced, and knocking due to pre-ignition at high temperatures can be prevented. In addition, after a predetermined period of time when the engine is running at a low speed and a high load, the ignition timing by the ignition means that performs ignition in the combustion chamber is corrected in advance according to the rise in the engine water temperature. The torque can be increased while preventing the occurrence of knocking due to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, the code | symbol 1 shows the engine 1 which has a control apparatus. The engine 1 is configured as an intake passage injection type engine, and a DOHC 4-valve type is adopted as the valve operating mechanism. A cylinder head 2 is mounted on an upper portion of a cylinder 2A constituting the engine 1. The intake-side valve mechanism 50 includes an intake valve 7a that opens and closes an intake port 11 formed in the cylinder head 2 so as to communicate with the combustion chamber 40, and an intake valve that abuts the upper end of the intake valve 7a via a rocker arm (not shown). The intake camshaft 21 is formed with a cam 3a, and a known valve spring that biases the intake valve 7a in the valve closing direction. The valve mechanism 51 includes an exhaust valve 7b that opens and closes an exhaust port 17 formed in the cylinder head 2 so as to communicate with the combustion chamber 40, and an exhaust cam 3b that abuts the upper end of the exhaust valve 7b via a rocker arm (not shown). The exhaust camshaft 22 is formed and a known valve spring that biases the exhaust valve 7b in the valve closing direction. Timing pulleys 4 a and 4 b are connected to the front ends of the intake camshaft 21 and the exhaust camshaft 22, respectively. These timing pulleys 4 a and 4 b are connected to a crankshaft 6 via a timing belt 5. The timing pulleys 4 a and 4 b and the camshafts 21 and 22 are rotationally driven as the crankshaft 6 rotates, and the intake and exhaust valves 7 a and 7 b are opened and closed in synchronization with the rotation of the engine 1 by the camshafts 21 and 22. Driven.

  Between each of the camshafts 21 and 22 and the timing pulleys 4a and 4b, a vane type timing variable mechanism 8a (hereinafter referred to as "VVT8a") is provided as an intake side variable timing mechanism. The configuration of the VVT 8a is well known in, for example, Japanese Patent Application Laid-Open No. 2000-27609, and will not be described in detail. However, a vane rotor is rotatably provided in a housing provided in the timing pulley 4a, and an intake camshaft 21 is connected to the vane rotor Configured. An oil control valve (hereinafter referred to as “OCV”) 9a is connected to the VVT 8a, and hydraulic pressure is applied to the vane rotor in accordance with the switching of the OCV 9a using hydraulic oil supplied from the oil pump 10 of the engine 1. As a result, the phase of the camshaft 21 with respect to the timing pulley 4a, that is, the opening / closing timing of the intake valve 7a is adjusted. In this embodiment, the VVT 8a constitutes an actual compression ratio variable means.

  In the intake passage 12 connected to the intake port 11, intake air is introduced from the air cleaner 13 as the piston 16 reciprocates up and down in the cylinder 2 </ b> A in FIG. 1 and is provided in the intake passage 12. After the flow rate is adjusted according to the opening degree of the throttle valve 14, it is mixed with the fuel injected from the fuel injection valve 15 as fuel injection means, and flows into the cylinder 2A via the intake port 11 when the intake valve 7a is opened. An air flow sensor 43 is disposed in the intake passage 12 located between the air cleaner 13 and the throttle valve 14.

  The cylinder head 2 is provided with a spark plug 19 as an ignition means that faces the combustion chamber 40 and performs ignition in the combustion chamber 40. An ignition signal distributed by the distributor 41 is applied to the spark plug 19. The distributor 41 distributes the high voltage output from the igniter 42 to the spark plug 19 in synchronization with the rotation of the crankshaft 6, that is, the crank angle. The ignition timing of the spark plug 19 is determined by the high voltage output timing from the igniter 42.

  In the exhaust passage 18 connected to the exhaust port 17, the exhaust gas after combustion in the combustion chamber 40 is guided from the exhaust port 17 as the piston 16 rises when the exhaust valve 7 b is opened, and is placed on the exhaust passage 18. It is discharged to the outside through the provided catalyst 20 and a silencer (not shown).

  In the vehicle interior, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs, control maps, etc., a central processing unit (CPU), an ECU as a control means including a timer counter, etc. An (engine control unit) 31 is installed and performs overall control of the engine 1. On the input side of the ECU 31, there are a rotation speed sensor 32 as a rotation speed detection means for detecting the engine rotation speed, a throttle opening degree sensor 33 as a load posting means for detecting the opening degree of the throttle valve 14 serving as an engine load, and engine cooling. Various sensors such as a water temperature sensor 34 and an air flow sensor 43 as temperature detecting means for detecting the temperature of the water and a timer (not shown) are connected. An OCV 9a, a fuel injection valve 15, a spark plug 19, an igniter 42, and the like are connected to the output side of the ECU 31. In the present embodiment, the rotation speed sensor 32, the throttle opening sensor 33, and the air flow sensor 43 constitute an operation state detection unit for detecting the operation state of the engine 1.

  In this embodiment, it is assumed that the crankshaft 6 rotates twice for a series of four strokes of an intake stroke, a compression stroke, an explosion / expansion stroke and an exhaust stroke in the engine 1, and the rotational speed sensor 32 has 30 ° CA per pulse. The crank angle is detected as a percentage.

  The ECU 31 determines the fuel injection amount and the like based on detection information from each sensor, and drives and controls the fuel injection valve 15. The ECU 31 has a basic VVT phase (KHNVVT) based on a set value corresponding to a predetermined engine speed, a set value corresponding to a predetermined load, a lower limit value EvL and an upper limit value EvH of volumetric efficiency, an engine speed and a throttle opening. A VVT phase map and an ignition timing map (not shown) for calculating the basic ignition timing (KHNIGT) are stored. The ECU 31 also includes a first correction map (not shown) for calculating a VVT phase water temperature correction value (VVTWT) and a VVT phase water temperature correction ignition timing correction value (IGTVVTWT) from the engine speed, throttle opening, and water temperature, A second correction map (not shown) for calculating a VVT phase water temperature correction value (VVTTWTA) and a VVT phase water temperature correction ignition timing correction value (IGTVVTTWTA) from the rotation speed, throttle opening, and water temperature is stored. The first correction map and the second correction map have different correction widths. When the first correction map is used, the control width is larger than when the second correction map is used. It is like that.

  The ECU 31 appropriately controls the drive of the VVT 8a and the igniter 22 based on the map information, and controls the opening / closing timing of the intake valve 7a, that is, the overlap amount and the ignition timing of the intake valve 7a and the exhaust valve 7b. In the present embodiment, the actual compression ratio is kept high until a predetermined time elapses when the engine 1 is in a low rotation and high load state, and when the predetermined time elapses, the valve opening timing by the VVT 8a is retarded as the water temperature rises. The OCV 9a is controlled so as to control the movement of the spark plug 19 and the ignition timing of the spark plug 19 is advanced according to the rise in the water temperature.

  FIG. 2 is a diagram showing the VVT phase, ignition timing, and torque change according to the water temperature change. In FIG. 2, the broken line shows the relationship between torque and ignition timing when the phase of VVT 8a is constant, and the solid line shows the relationship between torque and ignition timing when the phase of VVT 8a is varied based on the first correction value. The dashed line shows the relationship between torque and ignition timing when the phase of the VVT 8a is varied based on the second correction value. In the figure, symbol TW indicates a predetermined temperature at which the phase of the VVT 8a is switched.

  An example of the processing operation by the control device having such a configuration will be described with reference to the flowcharts shown in FIGS. FIGS. 4 and 5 are flowcharts for switching the opening / closing timing of the intake valve 7a and switching the ignition timing by the spark plug 19 among the processes executed by the ECU 31, and FIG. This is for determining the elapsed time of the load state. These processes are interrupted at predetermined intervals every predetermined time while the engine 1 is in operation.

  In step R <b> 1 in FIG. 3, the volumetric efficiency Ev of the engine is calculated from the output of the throttle opening sensor 33 and the output of the airflow sensor 43. In steps R2 and R3, it is determined whether or not FLGEVH = 1 and FLGEVL = 1. If neither condition is satisfied, the process proceeds to step R4.

  In Step R4, it is determined whether or not the state in which the volumetric efficiency Ev is lower than the lower limit value EvL continues for a predetermined time. If so, the process proceeds to Step R5 and sets FLGEVL = 1 and proceeds to Step R6. . In step R6, it is determined whether or not the volumetric efficiency Ev is greater than the upper limit value EvH. If it is larger, FLGEVL = 0 is set in step R7 and the process proceeds to step R8. If not larger, the process proceeds to step R11 and FLGEVH = 0. And In step R8, it is determined whether or not the state in which the volumetric efficiency Ev is larger than the upper limit value EvH continues for a predetermined time. If it continues, the process proceeds to step R9 to set FLGEVH = 0. It progresses to step R10 and sets FLGEVH = 1. That is, when the low rotation and high load state continues for a predetermined time, FLGEVH = 0 is set. When the low rotation and high load state is not yet continued for the predetermined time, FLGEVH = 1 is set. Is done.

  When the processing of FIG. 4 is started, information on the engine speed, load, and cooling water temperature is detected from the rotation speed sensor 32, the throttle opening sensor 33, and the water temperature sensor 34 in step S1. In step S2, the basic VVT phase (KHNVVT) is determined from the VVT phase map based on the detected engine speed and load. In step S3, the basic ignition timing (KHNIGT) is determined from the ignition timing map based on the detected engine speed and load. ).

  In step S4, the detected engine speed is compared with a predetermined value to determine whether or not the engine 1 is at a low speed. If the engine speed is lower than the predetermined value, the process proceeds to step S5. In step S5, the detected load is compared with a predetermined value to determine whether or not the engine 1 is in a high load range. If this load is greater than the predetermined value, it is determined that correction is necessary, and the process proceeds to step S6.

  In step S6, it is determined whether FLGEVH = 1. If FLGEVH = 1, it is determined that the low rotation and high load state has continued for a predetermined time, and the process proceeds to step S7. In step S7, a VVT phase water temperature correction value (VVTWT) is calculated and determined from the detected engine speed, throttle opening and water temperature, and the process proceeds to step S8, where the basic VVT phase (KHNVVT) determined in step S2 is set. The VVT control value 1 is determined by adding and correcting the VVT phase water temperature correction value (VVTWT). Based on the determined VVT control value 1, the ECU 31 controls the driving of the OCV 9a to switch the phase of the VVT 8a to the retard side. The degree of switching to the retard side is determined in relation to the water temperature as shown in FIG. In this embodiment, as the temperature rises at the predetermined temperature TW as a boundary, the amount of movement of the VVT 8a to the retard side increases.

  In step S9, a VVT phase water temperature correction ignition timing correction value (IGTVVTWT) is calculated and determined from the detected engine speed, throttle opening and water temperature information, and the process proceeds to step S10, where the basic ignition timing (KHNIGT determined in step S3 is determined. ) And VVT phase water temperature correction ignition timing correction value (IGTVVTWT) is added for correction to determine ignition timing correction value 1. Then, based on the determined ignition timing correction value 1, the ECU 31 controls the igniter 42 to switch the ignition timing by the spark plug 19 to the advance side. The degree to which the angle of advance is switched is determined in relation to the water temperature as shown in FIG. In this embodiment, as the temperature rises at the predetermined temperature TW as a boundary, the amount of movement of the ignition timing by the spark plug 19 to the advance side is increased. That is, in the processing from step S7 to step S10, calculation of the VVT control value 1 and the ignition timing correction value 1 is performed based on the first correction map.

  If FLGEVH = 1 is not satisfied in step S6, the low temperature and high load state has not been continued for a predetermined time, for example, when the accelerator opening is temporarily increased, and the temperature in the combustion chamber 40 is excessive. Assuming that pre-ignition cannot occur, the process proceeds to step S13 in FIG. In step S13, a VVT phase water temperature correction value (VVTTWTA) is calculated and determined from the detected engine speed, throttle opening, and water temperature, the process proceeds to step S14, and the basic VVT phase (KHNVVT) determined in step S2 is set. The VVT phase water temperature correction value (VVTTWTA) is added and corrected to determine the VVT control value 2. Based on the determined VVT control value 2, the ECU 31 controls the drive of the OCV 9a to switch the phase of the VVT 8a to the retard side. Since the VVT control value 2 is calculated using the second correction map, the value is smaller than the VVT control value 1.

  In step S15, a VVT phase water temperature correction ignition timing correction value (IGTVVTWT) is calculated and determined based on the detected engine speed, throttle opening, and water temperature information. The process proceeds to step S16, and the basic ignition timing (KHNIGT determined in step S3 is reached. And VVT phase water temperature correction ignition timing correction value (IGTVVTWTA) is added to correct the ignition timing correction value 2. Then, based on the determined ignition timing correction value 2, the ECU 31 controls the igniter 42 to switch the ignition timing by the spark plug 19 to the advance side. Since the ignition timing correction value 2 is calculated using the second correction map, the value is smaller than the ignition timing correction value 1. That is, in the processing from step S13 to step S16, the VVT control value 2 and the ignition timing correction value 2 are calculated based on the second correction map.

  On the other hand, if the engine speed is not lower (higher) than the predetermined value in step S4 in FIG. 4 or if the load is not higher (smaller) than the predetermined value in step S5, it is determined that no correction is necessary. Proceed to S11. Then, the basic VVT phase (KHNVVT) determined in step S2 is set as the VVT control value, and the process proceeds to step S12 and the basic ignition timing (KHNIGT) determined in step S3 is set as the ignition timing control value.

  In this way, the engine 1 is in a low rotation and high load state, and when this state has passed for a predetermined time, the VVT phase, that is, the opening / closing timing of the intake valve 7a is delayed by a relatively large amount, and the exhaust stroke. The opening of the intake valve 7a immediately before moving from the intake stroke to the intake stroke is delayed. For this reason, the actual compression ratio in the combustion chamber 40 at the time of high temperature becomes low, and the occurrence of knocking due to pre-ignition can be prevented. In addition, since the ignition timing by the spark plug 19 that performs ignition in the combustion chamber 40 is corrected in advance according to the rise in the water temperature of the engine 1, torque can be increased and fuel efficiency can be improved.

  Further, even when the engine 1 is at a low speed and a high load, if the state does not continue for a predetermined time, the VVT phase, that is, the opening / closing timing of the intake valve 7a is advanced, that is, the retarded angle. Since the opening of the intake valve 7a before and after the transition from the exhaust stroke to the intake stroke is accelerated by suppressing the amount of movement to the side, the volumetric efficiency of the amount of air sucked increases and the reduction in the actual compression ratio is suppressed. It is done. For this reason, the torque can be increased by effectively utilizing the time lag period between the load increase and the temperature increase in the combustion chamber 40 as in the case of a temporary load increase.

  In the above embodiment, the vane type VVT 8a is provided. However, the configuration of the timing variable mechanism is not limited to this. For example, the variable timing mechanism may be replaced with a helical timing variable mechanism or an eccentricity that changes the eccentric amount of the cam with respect to the cam shaft. A timing variable mechanism of a type, a switching type timing variable mechanism that selectively operates cams having different characteristics, an electromagnetic timing variable mechanism that directly opens and closes a valve by an electromagnetic actuator, or the like may be used.

It is a figure which shows the structure of the control apparatus of the engine which shows one embodiment of this invention. It is a characteristic view which shows the relationship between the phase of an intake valve, torque, and ignition timing. It is a flowchart for determining the predetermined period of the state of low rotation and high load. It is a flowchart which shows an example of control of the control means with respect to a variable timing mechanism and an ignition means. 5 is a flowchart following the terminal A of FIG.

Explanation of symbols

1 Engine 11 Intake port 7a Intake valve 8a Actual compression ratio variable means (variable timing mechanism)
19 Ignition means 23, 33, 43 Operating state detection means 31 Control means 34 Temperature detection means 40 Combustion chamber

Claims (4)

An operating state detecting means for detecting the operating state of the engine;
An actual compression ratio variable means for changing an actual compression ratio in the combustion chamber of the engine;
The operating state of the engine is determined based on the detection information from the operating state detection, and the actual compression ratio is reduced so that the actual compression ratio is lower than before the predetermined period when the low speed and high load state of the engine has elapsed for a predetermined period. An engine control device comprising control means for controlling the operation of the compression ratio variable means. The engine control apparatus according to claim 1, wherein
The actual compression ratio varying means is a variable timing mechanism capable of varying the valve opening timing of the intake valve that opens and closes the intake port leading to the combustion chamber,
The control means controls movement of the valve opening timing by the variable timing mechanism to the retard side when the engine is in a low rotation and high load state, and the amount of movement to the retard side before the predetermined period elapses. A control device for an engine characterized by being suppressed. The engine control device according to claim 2,
Temperature detecting means for detecting the temperature of the engine;
The engine control apparatus, wherein the control means determines a water temperature state from detection information from the temperature detection means, and controls to move the variable timing mechanism to the retard side in response to a rise in water temperature. The engine control apparatus according to claim 1, wherein
Ignition means for performing ignition in the combustion chamber;
The engine control apparatus according to claim 1, wherein the control means corrects the ignition timing of the ignition means in accordance with the reduction control of the actual compression ratio.

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