JP2009209786A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the output of an internal combustion engine which has a variable valve timing mechanism for a supercharger, and which is equipped with an inlet valve and which is improved in fuel economy. <P>SOLUTION: If the variation quantity ΔAPO of an accelerator opening is larger than a predetermined value A, or the accelerator opening APO is larger than a predetermined value B, after a target excess pressure is set, taking into consideration the friction of the supercharger, the side of which the valve timing of the inlet valve is taken, a timing advance side or a timing retard side, is determined, based on an engine speed and an excess pressure and feedback control of the excess pressure is conducted, while switching the target excess pressure according to the valve timing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for improving fuel consumption and high output performance in an internal combustion engine including a supercharger and a variable valve timing mechanism that can vary the valve timing of an intake valve.

  Patent Document 1 discloses an internal combustion engine including a supercharger and a variable valve timing mechanism. In general, in this type of internal combustion engine, air response and torque are increased by increasing the charging efficiency by advancing the valve timing of the intake valve when acceleration is requested or when the load is high.

In the supercharging region, the scavenging efficiency is increased and the volumetric efficiency is improved by advancing the valve timing of the intake valve to increase the valve overlap amount with the exhaust valve.
JP 2004-183511 A

  However, if high supercharging is performed during acceleration or high load as described above, knocking generally tends to occur. Therefore, knocking is suppressed by increasing the amount of fuel, but fuel efficiency is significantly deteriorated.

  In addition, if the valve timing of the intake valve is advanced in the supercharging region, an increase in the fuel is still required as the exhaust gas temperature rises due to the ignition timing retard from knocking. After all, the area where high supercharging is possible is limited.

  The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide a control device for an internal combustion engine that can obtain a target torque while appropriately switching the valve timing of an intake valve.

For this reason, the invention according to claim 1
In an internal combustion engine provided with a supercharger and a variable valve timing mechanism that can change the valve timing of an intake valve,
Driving operation detection means for detecting the driving operation of the driver;
Valve timing switching means for switching the valve timing of the intake valve by the variable valve timing mechanism between the advance side and the retard side based on the degree of acceleration request by the driving operation;
Torque control means for controlling engine torque while suppressing a torque step due to switching of valve timing of the intake valve;
Constructed including.

  In this way, the valve timing of the intake valve is advanced to the vicinity of the knock occurrence limit to improve the output, and in the state where the advance is made, knocking occurs in the region where it is retarded. On the other hand, by controlling so as to suppress the torque step, it is possible to improve the output to the maximum while suppressing knocking, and as a result, the fuel efficiency can also be improved.

FIG. 1 is a system diagram showing the overall configuration of an embodiment of the present invention.
The intake passage 2 of the engine 1 is provided with an air flow meter 3 for detecting the intake air amount from the upstream side, a mechanically driven supercharger (supercharger) 4, an intercooler 5 for supercharging intake air cooling, and a throttle valve 6. It is done.

  A bypass passage 41 that bypasses the supercharger 4 and connects the intake passage 2 is provided. By controlling the opening of the bypass valve 42 interposed in the bypass passage 41 by an actuator, the supercharging pressure is reduced. Adjust.

The throttle valve 6 adjusts the amount of intake air by controlling the opening degree by an actuator.
Each cylinder of the engine 1 is provided with a fuel injection valve 7 that injects fuel into the combustion chamber, and an ignition plug 8 that performs spark ignition in the combustion chamber. Fuel is injected from the fuel injection valve 7 to form an air-fuel mixture, which is compressed in the combustion chamber 6 and ignited by spark ignition by the spark plug 8.

Exhaust gas from the engine 1 is discharged from the combustion chamber 6 to the exhaust passage 11 via the exhaust valve 10 and released into the atmosphere via an exhaust purification catalyst and a muffler (not shown).
The intake valve 9 and the exhaust valve 10 are driven to open and close by cams provided on the intake valve side camshaft 12 and the exhaust valve side camshaft 13, respectively.

  The intake valve side camshaft 12 and the exhaust valve side camshaft 13 are of hydraulic drive type that advance and retard the valve timing (opening and closing timing) of the intake and exhaust valves by changing the rotational phase of the camshaft with respect to the crankshaft. Variable valve timing mechanisms (hereinafter referred to as VTC mechanisms) 14A and 14B are provided. The exhaust valve 10 may be driven at a constant valve timing by a cam fixed to the cam shaft.

  As shown in FIG. 2, the hydraulic drive type VTC mechanism 14 includes a cylindrical housing 51 of a cam sprocket that is rotationally driven by a crankshaft (not shown) via a timing chain, and the camshafts (12, 13). ) And a rotating member 52 rotatably accommodated in the housing 51, and a hydraulic circuit 53 that rotates the rotating member 52 relative to the housing 51.

On the inner peripheral surface of the housing 51, a trapezoidal shape in cross section is provided, and four partition wall portions 51A provided along the axial direction of the housing 51 are projected at 90 ° intervals.
The rotating member 52 is fixed to the front end portion of the camshaft, and four vanes 52B are provided at 90 ° intervals on the outer peripheral surface of the annular base portion 52A, so that the recesses between the partition wall portions 51A of the housing 51 are provided. The recessed portion is separated in the front and rear in the rotational direction, and an advance side hydraulic chamber 61 and a retard side hydraulic chamber 62 are formed between both sides of the vane 52B and both side surfaces of each partition wall 51A.

  The hydraulic circuit 53 includes two systems of a first hydraulic passage 81 that supplies and discharges hydraulic pressure to the advance side hydraulic chamber 61 and a second hydraulic passage 82 that supplies and discharges hydraulic pressure to the retard side hydraulic chamber 62. The hydraulic passages 81 and 82 are connected to a supply passage 83 and drain passages 84A and 84B via passage-switching electromagnetic switching valves 91, respectively. The supply passage 83 is connected to an engine-driven oil pump that pumps oil in the oil pan, while the downstream ends of the drain passages 84A and 84B are connected to the oil pan.

The electromagnetic switching valve 91 is configured such that an internal spool valve body 92 relatively switches and controls the hydraulic passages 81 and 82, the supply passage 83, and the drain passages 84A and 84B.
The ECU 21 controls an energization amount for the solenoid 93 of the electromagnetic switching valve 91.

  For example, when the energization amount to the solenoid 93 is increased, the hydraulic oil is supplied into the advance hydraulic chamber 61 through the first hydraulic passage 81 as shown in FIG. The hydraulic oil in the hydraulic chamber 62 is discharged to the oil pan through the second hydraulic passage 82 and the drain passage 84A, and the retard side hydraulic chamber 62 becomes low pressure.

  For this reason, the rotating member 52 rotates to the advance side through the vane 52B. In the case of the variable valve timing mechanism 14 on the intake valve 9 side, the valve timing of the intake valve 9 is advanced.

  On the other hand, when the energization amount to the solenoid 93 is decreased, the hydraulic oil pumped from the oil pump is supplied to the retard side hydraulic chamber 62 through the second hydraulic passage 82 as shown in FIG. At the same time, the hydraulic oil in the advance side hydraulic chamber 61 passes through the first hydraulic passage 81 and is discharged from the drain passage 84B into the oil pan.

  Accordingly, the internal pressure of the retard side hydraulic chamber 62 is high and the internal pressure of the advance side hydraulic chamber 61 is low, and the rotating member 52 rotates to the retard side via the vane 52B. In the case of the variable valve timing mechanism 14 on the intake valve 9 side, the valve timing of the intake valve 9 is retarded.

  Returning to FIG. 1, the operations of the variable valve timing mechanisms 14A and 14B, the bypass valve 42, the throttle valve 6, the fuel injection valve 7 and the spark plug 8 are controlled by an ECU (electronic control circuit) 21.

  For these controls, the ECU 21 includes an accelerator opening sensor 19 serving as a driving operation detecting means for detecting the depression amount of the accelerator pedal that is depressed by the driver, that is, the accelerator opening, the air flow meter 3, the crank angle sensor. 15, signals from the camshaft sensors 16A and 16B, the water temperature sensor 17, the pressure sensor 18 for detecting the intake pressure, and the like are input.

  In the internal combustion engine having such a system configuration, in this embodiment, as control according to the present invention, the valve timing of the intake valve 9 is delayed at a predetermined timing for each desired operating state based on the accelerator operation of the driver. Switching is performed with a step between the corner side and the advance side, and control is performed so that there is no torque step at the time of switching.

  Here, in this embodiment, as basic valve timing control of the intake valve 9, a so-called delayed closing mirror cycle in which the closing timing IVC is delayed from the bottom dead center BDC is applied. Therefore, when the angle is advanced, IVC approaches BDC and the intake cylinder volume increases, and when the angle is retarded, IVC moves away from BDC and the intake cylinder volume decreases.

FIG. 3 shows the flow of the control.
In step S1, it is determined whether the accelerator opening APO detected by the accelerator opening sensor 19 is fully open. If it is determined that the accelerator opening APO is fully open, the process proceeds to step S2.

  In step S2, switching of the valve timing of the intake valve 9 is controlled based on the engine rotational speed Ne detected by the crank angle sensor 15. Specifically, as shown in FIG. 4, the valve timing is controlled to the advance side at a predetermined rotational speed N1 or less where the torque difference is large, and when it is greater than N1, the valve timing is controlled to switch to the retard side. Do.

  Or, when the valve is fully opened, an increase in the fuel injection amount for avoiding knocking is also used. Therefore, when the valve timing is advanced as shown in FIG. 5A, the control is performed up to a limit rotational speed N2 or less at which misfire or smoke occurs. When the limit rotational speed N2 is exceeded, the control may be switched to the control for retarding the valve timing as shown in FIG.

By controlling in this way, the output performance when fully open can be enhanced as much as possible.
If it is determined in step S1 that the accelerator opening APO is not fully open, the process proceeds to step S3, where the change amount ΔAPO of the accelerator opening is 0 or less (steady or deceleration), and the accelerator opening APO is a predetermined opening. It is determined whether it is B or less (low load).

When the condition of step S1 is satisfied, that is, when neither acceleration nor high load is applied, the process proceeds to step S4 to determine whether the intake pressure Pb is higher than the external pressure Pa.
When the intake pressure Pb is higher than the external pressure Pa, the process proceeds to step S5, and the target supercharging pressure tPb corresponding to the target torque corresponding to the accelerator opening APO and the engine rotational speed Ne is taken into consideration while considering the friction of the supercharger 4. calculate.

  In step S6, the valve timing of the intake valve 9 is retarded, and the supercharging pressure is controlled only by the opening degree of the bypass valve 42 while the throttle valve 6 is fully opened. Specifically, feedback control is performed so that the actual boost pressure detected by the intake pressure sensor 18 approaches the target boost pressure Pb.

  The supercharging pressure control by a general supercharger is performed by throttle control of the throttle valve on the downstream side. In this case, fuel consumption is deteriorated due to throttle loss of the throttle valve. In the present embodiment, by controlling the opening degree of the bypass valve 42, the required supercharging pressure can be obtained without any throttle loss, so that the fuel efficiency is improved.

  Also, when the intake cylinder volume is decreased by retarding the valve timing of the intake valve 9 and compared with the case where the intake cylinder volume is increased by advancing, the same intake air amount is reduced by the compression in the cylinder. The decrease is obtained by increasing the supercharging pressure by the supercharger. However, when the supercharging pressure is increased, the intake air whose temperature has increased due to supercharging can be cooled by the intercooler 5, and finally The compression end temperature in the cylinder can be reduced, and the occurrence of knocking can be suppressed.

When the valve timing of the intake valve 9 is switched from the advanced state to the retarded angle, the target boost pressure tPb is switched as shown in FIG. 6 and increases stepwise as described above.
Therefore, the occurrence of knocking can be suppressed, and if it is advanced, it is necessary to increase the fuel injection amount in order to suppress knocking. Can improve.

The state at the time of this driving | running is shown to (A) of FIG.
When it is determined in step S4 that the intake pressure Pb is equal to or lower than the external pressure Pa, since it is not supercharging, the bypass valve 42 is fully opened and the intake air amount is controlled by the opening degree of the throttle valve 6. Also, the valve timing of the intake valve 9 is controlled to the retard side.

  That is, by retarding the IVC and reducing the intake cylinder volume, the opening degree of the throttle valve 6 is opened to obtain the same intake air amount, and the throttle loss of the throttle valve 6 can be made as small as possible. Can improve fuel efficiency.

The state at the time of this driving | running is shown to (B) of FIG.
Next, when the condition of step S3 is not satisfied, the routine proceeds to step S8, where the change amount ΔAPO of the accelerator opening is larger than the predetermined value A, or the accelerator opening APO is larger than the predetermined value B, that is, acceleration. It is determined whether the demand is large or the load is high.

  When the above condition is satisfied and the acceleration request is large or the load is high, the process proceeds to step S9, and in the same manner as in step S5, the accelerator opening APO, A target boost pressure tPb corresponding to the target torque corresponding to the engine speed Ne or the like is calculated.

  Next, in step S10, based on the engine speed Ne and the supercharging pressure (intake pressure) Pb, whether to maintain the valve timing of the intake valve 9 at the advance angle or switch to the retard angle from the map shown in FIG. decide.

Here, the map is set as follows. The following conditions are set as conditions for switching to the retard side.
A. In the knocking control, the ignition timing is retarded to suppress knocking, but when the ignition timing is retarded, the exhaust temperature rises. Region where exhaust temperature exceeds limit temperature and cannot be controlled by retarding ignition timing with intake valve 9 advanced. In a state where the intake valve 9 is advanced, a region exceeding the rich misfire limit due to the increase in fuel for suppressing knocking. In consideration of the responsiveness of the bypass valve 42 and the throttle valve 6 in a transient state, it is necessary to advance the intake valve 9 and increase the intake cylinder volume in relation to the rise of the supercharging pressure and the required vehicle acceleration. Region other than D. Area other than the area where it is necessary to increase the intake cylinder volume with the intake valve 9 being advanced with respect to the vehicle required acceleration in consideration of the shift response delay during transition E. In consideration of the delay of the turbocharger rotation speed from the time of clutch engagement, an area other than the area where the intake valve volume needs to be increased with the intake valve 9 being advanced with respect to the vehicle required acceleration. , B are conditions that need to be retarded when either one is satisfied, and C, D, and E are conditions that need to be retarded when all these conditions are satisfied. is there. In addition, “area” in “other than area” in each of C, D, and E is a condition that needs to be advanced even when overlapping with A and B.

Therefore, in summary, in the region of (A∪B) ∩C∩D∩E, the retard angle side is set, and in other regions, the advance side is set.
Then, the target boost pressure is switched according to the advance / delay of the intake valve 9 determined using the map set as described above, and feedback is performed so that the boost pressure approaches the target boost pressure. Control. It goes without saying that the throttle valve 6 is kept fully open.

  With such a configuration, when the valve timing of the intake valve 9 is advanced as much as possible using the map, the cylinder intake volume is increased, the maximum output is ensured, and the knocking limit is exceeded. By controlling the bypass valve while switching the timing to a retarded angle, the supercharging pressure can be maintained as high as possible to maintain a high output, and fuel efficiency can be improved.

The state at the time of this driving | running is shown to (C) of FIG.
Further, when the condition of step S8 is not satisfied, that is, when the accelerator opening degree change ΔAPO is less than the predetermined value A and the accelerator opening APO is less than the predetermined value B, the process proceeds to steps S11 and S12. move on.

  In steps S11 and S12, similarly to steps S5 and S6, the target boost pressure tPb corresponding to the target torque corresponding to the accelerator opening APO and the engine speed Ne is calculated while considering the friction of the supercharger 4. The supercharging pressure is controlled only by the opening degree of the bypass valve 42 while retarding the valve timing of the intake valve 9 and fully opening the throttle valve 6.

Therefore, even during slow acceleration, the opening degree of the bypass valve 42 can be controlled while retarding the intake valve 9 to obtain a necessary supercharging pressure, so that fuel efficiency is improved.
As described above, according to the present embodiment, it is possible to ensure the maximum intake air amount and the minimum energy loss while suppressing knocking while switching the valve timing of the intake valve according to the operating state. It is possible to greatly improve output and fuel efficiency.

  Each step S2, S6, S7, S10, S12 in FIG. 3 constitutes a torque control means.

1 is a system diagram showing the overall configuration of an embodiment of the present invention. Sectional drawing which shows the valve timing control state by the variable valve timing mechanism in embodiment same as the above. The flowchart which shows the control in embodiment same as the above. The figure which shows an example of the valve timing switching timing of the intake valve at the time of accelerator full open. The figure which shows another example of the valve timing switching timing of the intake valve at the time of accelerator full open. The figure which shows the supercharging pressure switching accompanying the valve timing switching of an intake valve. The time chart which shows the change of the various state quantity in each driving | running state. The map which shows the valve timing switching operation conditions of the intake valve used at the time of an acceleration request | requirement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 9 ... Intake valve 10 ... Exhaust valve 12 ... Intake valve side cam shaft 14A ... Variable valve timing mechanism for intake valves 15 ... Crank angle sensor 16A ... Cam shaft sensor 21 ... Engine control circuit (ECU)

Claims (9)

In an internal combustion engine provided with a supercharger and a variable valve timing mechanism that can change the valve timing of an intake valve,
Driving operation detection means for detecting the driving operation of the driver;
Valve timing switching means for switching the valve timing of the intake valve by the variable valve timing mechanism between the advance side and the retard side based on the degree of acceleration request by the driving operation;
Torque control means for controlling engine torque while suppressing a torque step due to switching of valve timing of the intake valve;
A control apparatus for an internal combustion engine, comprising:   The torque control means performs control so that the valve timing is switched from the advance side to the retard side when the accelerator step is fully opened and the torque step before and after the switching of the valve timing of the intake valve is equal to or higher than the engine speed at which the torque level is lower than a predetermined value. The control apparatus for an internal combustion engine according to claim 1.   When supercharging is performed when acceleration is not required, the torque control means controls the engine pressure to be close to the target supercharging pressure by controlling the supercharging pressure close to the target supercharging pressure while keeping the valve timing of the intake valve retarded. The control device for an internal combustion engine according to claim 1 or 2, wherein the control device is controlled.   The internal combustion engine includes an intake throttle valve that is controlled to an arbitrary opening, and when the acceleration is not required and when not supercharged, the intake throttle valve is opened while the intake valve timing is retarded. The internal combustion engine control apparatus according to any one of claims 1 to 3, wherein the engine torque is controlled by controlling the engine torque.   When the acceleration request is large except when the accelerator is fully opened, the torque control means switches and sets the target boost pressure according to the valve timing of the intake valve, and sets the intake valve based on the boost pressure and the engine speed. The engine torque is controlled by setting the switching of the valve timing and controlling the supercharging pressure to approach the target supercharging pressure, according to any one of claims 1 to 4. Control device for internal combustion engine.   When the acceleration request is small, the torque control means controls the engine torque by controlling the boost pressure to approach the target boost pressure while setting the valve timing of the intake valve to the retard side. The control device for an internal combustion engine according to any one of claims 1 to 5.   The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the supercharger is an engine-driven supercharger.   The bypass pressure is provided in a bypass passage that bypasses the supercharger and connects to the intake passage, and the supercharging pressure is controlled by controlling the opening degree of the bypass valve. 8. The control device for an internal combustion engine according to any one of 7 above.   The control apparatus for an internal combustion engine according to any one of claims 1 to 8, wherein an intercooler for supercharged intake air cooling is provided in an intake passage downstream of the supercharger.

Images