JP4200860B2 - Internal combustion engine with variable compression ratio mechanism - Google Patents

Description

  The present invention relates to an internal combustion engine with a variable compression ratio mechanism.

Conventionally, as disclosed in Patent Document 1, in a control device for an internal combustion engine that includes a variable compression ratio mechanism and changes the compression ratio according to the operating region, there is a problem in detecting the compression ratio due to a failure of the compression ratio sensor. It is known that this will be detected when it occurs, and the occurrence of knocking will be avoided by fixing the compression ratio at the time of malfunction to the low compression ratio side and setting the ignition timing to an appropriate timing on the retarded side. It has been.
Japanese Patent Publication No. 7-72515

  However, the case where the variable compression ratio mechanism itself fails is not disclosed. In other words, a failure of the compression ratio sensor can be fail-safe, but if the variable compression ratio mechanism itself fails due to sticking or the like, even if this failure is detected, the minimum compression ratio realized by the variable compression ratio mechanism can be set. However, depending on the compression ratio at the time of failure, knocking may occur and the drivability may be deteriorated. Alternatively, when the fail ignition timing is set in consideration of regular gasoline, there is a possibility that combustion deterioration and misfire may occur due to excessive retard.

  In view of such a problem, an object of the present invention is to avoid the occurrence of knocking when a variable compression ratio mechanism fails.

For this reason, the present invention detects a fixed failure of the variable compression ratio mechanism and detects the actual compression ratio (ε) of the variable compression ratio mechanism in the fixed state at that time, and responds to the required load of the engine when detecting the failure. The target compression ratio (εT) and the actual compression ratio (ε) are compared, and when the target compression ratio is lower than the actual compression ratio, the air amount and the fuel amount are corrected to decrease, and the actual load of the engine is Regulation is performed so as not to enter the operation regulation region on the higher load side than the load corresponding to the actual compression ratio (ε) .

  According to the present invention, when there is a possibility that knocking may occur in the operation state when the variable compression ratio mechanism fails, the operation region can be restricted to avoid the occurrence of knocking.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an internal combustion engine provided with a variable compression ratio mechanism 14. FIG. 2 is a diagram showing a state in which the compression ratio is changed. (A) shows a high compression ratio state, and (B) shows a low compression ratio state.
A piston 3 is slidably disposed in a cylinder 2 formed in a cylinder block (internal combustion engine body) 1. A combustion chamber 4 is defined by the piston 3 and a cylinder head (not shown). The piston 3 receives a combustion pressure from the combustion chamber 4.

The piston 3 is attached to one end of a variable compression ratio mechanism 14 constituted by a plurality of links. A driving motor (actuator) 20 is linked to the other end of the variable compression ratio mechanism 14, and the position of the piston 3 at the compression top dead center can be changed by the operation of the driving motor 20 (see FIG. 2). Hereinafter, the configuration of the variable compression ratio mechanism 14 will be described.
One end of an upper link (first link) 5 is connected to the piston 3 via a piston pin 10 so as to be swingable. The other end of the upper link 5 is swingably connected to a lower link (second link) 6 via a first connecting pin 11. The lower link 6 is attached to the crankshaft 8, and is rotatably connected to a position offset from the axial center position of the journal portion 8a of the crankshaft 8 by a crankpin 13.

The crankshaft 8 is rotatably supported on the cylinder block 1 by a crank bearing bracket (not shown).
One end of a control link (third link) 7 is connected to the lower link 6 via a second connecting pin 12 so as to be swingable. A circular rotary cam 15 that is eccentrically fixed to the control shaft 9 is rotatably fitted to the other end of the control link 7.

The control shaft 9 extends parallel to the crankshaft 8 in the cylinder row direction and is rotatably supported by the cylinder block 1. A worm wheel 21 is fixed to the control shaft 9.
The worm wheel 21 has a gear formed on the outer periphery, and this gear meshes with the worm 20 a of the drive motor 20.

The drive motor 20 is attached to the engine body, and rotates the motor according to the operation state by a rotation signal of an engine control device (not shown). The rotation angle by this motor rotation is calculated from the output signal of the angle sensor (compression ratio detection means) 17 attached to the drive motor 20.
As described above, by rotating the drive motor 20, the worm wheel 21 meshing with the worm 20a is rotated, and this rotation is transmitted directly to the control shaft 9, and the rotating cam 15 fixed to the shaft 9 is rotated eccentrically. As a result, the center position of the rotating cam 15, that is, the support center position of the other end of the control link 7 is displaced. For this reason, as shown in FIG. 2, the movement restraint conditions of the lower link 6 and the upper link 5 by the control link 7 change, the stroke stroke of the piston 3 with respect to the crank angle changes, and the compression ratio (volume of the combustion chamber 4) Is changed.

The compression ratio of the engine is detected based on the output signal of the angle sensor 17 attached to the drive motor 20. This is because the support center position of the other end of the control link 7 is determined by the output signal of the angle sensor 17, and the compression ratio in the link motion constraint condition at this time is determined.
In the variable compression ratio mechanism 14 described above, the compression ratio is changed by rotating the control shaft 9 using the worm wheel 21 and the worm 20, but the present invention is not limited to this. For example, as shown in FIG. 3, a rotation lever 18 is attached to the control shaft 9, and the control shaft 9 is rotated by rotating the rotation lever 18 by an output rod 24 of a linear motor (actuator) 23 that moves linearly. May be.

In this case, the rotary lever 18 fixes this one end to the control shaft 9. As shown in the figure, a slit 18a having a predetermined length and width is formed at the other end of the rotary lever 18. And the pin 26 attached to the front-end | tip of the output rod 24 of the linear motor 23 is fitted to this slit 18a.
The linear motor 23 is attached to the cylinder block (engine body) 1 and includes a power mechanism 25 that can extend and contract the output rod 24 in the distal direction. With this power mechanism 25, as shown in FIG. 3 (a), when the compression ratio is high, the output rod 24 is retracted and the control shaft 9 is rotated so that the other end (support center) of the control link 7 is positioned. Displace and change the compression ratio.

On the other hand, as shown in FIG. 3B, when the compression ratio is low, the output rod 24 is extended to the distal end side by the power mechanism 25 and the control shaft 9 is rotated, so that the other end (support center) of the control link 7 is rotated. Displace the position and change the compression ratio.
FIG. 4 is a compression ratio map obtained from the engine speed Ne and the engine load. The horizontal axis represents the engine speed Ne and the vertical axis represents the engine load. In addition, the line in a figure has shown that it is an equal compression ratio.

The compression ratio changed by the variable compression ratio mechanism 14 increases the compression ratio on the low load side to improve the combustion efficiency and the fuel consumption rate according to the operating state of the engine, while reducing the compression ratio on the high load side. And avoiding knocking.
Here, when the variable compression ratio mechanism 14 breaks down due to sticking or the like during operation of the engine, the compression ratio at the time of the failure is fixed. For this reason, for example, when the variable compression ratio mechanism 14 is stuck in a high compression ratio and operated in a high load region, the compression ratio becomes too high and knocking occurs. Hereinafter, control for restricting the engine operating region so as to avoid the occurrence of knocking when the variable compression ratio mechanism 14 fails will be described.

FIG. 5 is a flowchart of the operation region regulation of the internal combustion engine.
In step 1 (shown as “S1” in the figure, the same applies hereinafter), the actual compression ratio ε of the engine calculated based on the output signal of the angle sensor 17 and the operating state (engine speed and load) shown in FIG. The target compression ratio ε _T obtained from the compression ratio map corresponding to is read.
In step 2, it is determined whether or not there is a failure. Here, in the detection of the failure of the variable compression ratio mechanism 14, the actual compression ratio (compression ratio based on the angle sensor 17) ε read in step 1 coincides with the target compression ratio ε _T set by the compression ratio map. If it is not (ε ≠ ε _T ) and the actual compression ratio ε does not change, a failure (particularly a fixing failure) is determined. If it is determined that the variable compression ratio mechanism 14 has failed, the process proceeds to step 3. On the other hand, if it is determined that there is no failure, the process is terminated.

In Step 3, it is determined whether or not the compression ratio ε based on the angle sensor 17 is a compression ratio at which knocking is expected to occur (ε> ε _T ).
If the variable compression ratio mechanism 14 has failed, that is, if the actual compression ratio ε is a compression ratio at which knocking occurs (ε> ε _T ), the process proceeds to step 4. Thus, when a failure is detected at a compression ratio that may cause knocking, the operation region described later is regulated.

On the other hand, if the compression ratio does not cause knocking (ε ≦ ε _T ), the process is terminated. As a result, when a failure is detected at a compression ratio at which there is no possibility of occurrence of knocking, the operation region restriction is not performed and the deterioration in drivability is minimized.
In step 4, the engine operating region is regulated. This operation region restriction is performed by controlling the engine so as not to enter the operation restriction region. This is in a region where knocking or deterioration of combustion occurs when the operating state of the engine is in the operation restriction region, and setting this operation restriction region prevents the operation state from entering this region. It is to make it.

Here, when the failure of the variable compression ratio mechanism 14 is detected, the operating range is regulated by controlling the amount of air or fuel supplied to the engine.
As the air amount control in the operation region restriction, the amount of air flowing into the cylinder 2 is reduced by reducing the opening degree of the electric throttle valve (not shown). As a result, when the target air-fuel ratio is constant, the fuel injection amount from the fuel injection valve (not shown) decreases.

Further, as fuel amount control in the operation region regulation, the fuel amount in the combustion chamber 4 is reduced by fuel cut when the torque becomes excessive.
Thus, when a failure of the variable compression ratio mechanism 14 is detected, the operation state of the engine is controlled so as not to enter the operation restriction region at high load, that is, to operate in the operation region at low load.

In step 5, the target idle speed is increased. As a result, in idling operation, the deterioration of combustion due to a shift in the compression ratio is prevented by increasing the idling speed.
FIG. 6 is a diagram showing that the operation restriction region is set according to the compression ratio (fail compression ratio) ε _F when the variable compression ratio mechanism 14 fails. The horizontal axis represents the load, and the vertical axis represents the compression ratio. Show. The operation area and the operation restriction area are shown in the load direction. Note that ε _H represents the highest compression ratio realized by the variable compression ratio mechanism 14, and ε _L represents the lowest compression ratio realized by the variable compression ratio mechanism 14.

Here, the failure of the variable compression ratio mechanism 14 is detected based on the output signal (actual compression ratio ε) of the angle sensor 17 attached to the drive motor 20 (see step 2 in FIG. 5). The operation restriction region is set to a high load side operation region in which a compression ratio lower than the actual compression ratio ε _F at the time of failure detection detected by the angle sensor 17 is set.
As shown in FIG. 6, the region where the compression ratio is lower than the actual compression ratio ε _F at the time of failure detection (the region on the high load side) is the operation restriction region, and there is a concern about the occurrence of knocking or the like in this region. For this reason, the operation in this region is regulated, and the engine operating state is controlled in a lower load region than this operation restricted region, so that the high load region where a low compression ratio is required is regulated, and the operation due to the occurrence of knocking, etc. Minimize sexual deterioration.

  According to the present embodiment, in the internal combustion engine that includes the variable compression ratio mechanism 14 that can change the compression ratio and changes the compression ratio ε in accordance with the operation region, a failure detection unit that detects a failure of the variable compression ratio mechanism 14 ( Step 2) and operation region restriction means (steps 4 and 5) for restricting the operation region when a failure is detected are provided. For this reason, when there is a possibility that knocking may occur in the operation state when the variable compression ratio mechanism 14 breaks down, it is possible to avoid the occurrence of knocking by regulating the operation region.

Further, according to the present embodiment, the operation region restriction means controls the engine so as not to enter the operation restriction region (steps 4 and 5). For this reason, the driving | running | working in the driving | running | working area | region where knocking may generate | occur | produce is controlled, and drivability deterioration can be prevented.
Further, according to the present embodiment, the operation region restriction means restricts the operation region by reducing the amount of air supplied to the engine when a failure is detected (step 4). For this reason, when the variable compression ratio mechanism 14 breaks down in an operation region in which knocking may occur, deterioration in drivability can be minimized by simple control.

Further, according to the present embodiment, the operation region restricting means restricts the operation region by reducing the amount of fuel supplied to the engine (fuel cut or the like) when a failure is detected (step 4). For this reason, when the variable compression ratio mechanism 14 breaks down in an operation region in which knocking may occur, deterioration in drivability can be minimized by simple control.
Further, according to the present embodiment, the operation region restricting means operates in an operation region in which a compression ratio lower than the actual compression ratio ε _F at the time of failure detection detected by the compression ratio detection means (angle sensor 17) is set. The restriction area is set (steps 4 and 5, FIG. 6). For this reason, the region where the load of the engine is low can be set as the operation region, and deterioration of operability due to the occurrence of knocking or the like can be prevented.

Further, according to the present embodiment, the idling speed is increased when a failure is detected (step 5). For this reason, it is possible to prevent deterioration in combustion due to a shift in the compression ratio during idle operation.
According to the present embodiment, the variable compression ratio mechanism 14 is a multi-link type. For this reason, a compact configuration can be achieved. In the multi-link system, since the inertial force at high rotation differs depending on the compression ratio, it is effective to restrict the operation region when a failure of the variable compression ratio mechanism 14 is detected.

  Further, according to the present embodiment, the variable compression ratio mechanism 14 can swing to the first link 5 and the first link 5 that are swingably connected to the piston 3 via the piston pin 10. And a second link (lower link) 6 that is rotatably connected to the crankpin portion 13 of the crankshaft 8, and is pivotally connected to the second link 6 and the position of the support center point is The displacement of the third link (control link) 7 that is movably supported and the position of the movable support center point of the third link 7 (the support center position of the other end of the control link 7) is displaced. Means for displacing the position (control shaft 9, rotating cam 15, worm wheel 21, worm 20a, drive motor 20). For this reason, the compression ratio ε can be changed by changing the motion constraint condition of the link mechanism and changing the stroke of the piston 3 with respect to the crank angle.

7 and 8 show a reference example of the present invention, and FIG . 7 is a flowchart for setting the operation restriction region in a region other than the maximum compression ratio εH of the variable compression ratio mechanism 14. Detailed description of the same processing as in FIG. 5 is omitted.
In step 1, the actual compression ratio ε and the target compression ratio εT are read.
In step 2, it is determined whether or not the variable compression ratio mechanism 14 has failed. If there is a failure, go to Step 6. On the other hand, if there is no failure, the process is terminated.

In step 6, it is determined whether or not the target compression ratio ε _T matches the maximum compression ratio ε _H (ε _T = ε _H ).
When the target compression ratio ε _T does not coincide with the maximum compression ratio ε _H (ε _T ≠ ε _H ), the process proceeds to step 4. This is because the operation region other than the operation region where the highest compression ratio ε _H is set is set as the operation restriction region.

On the other hand, when the target compression ratio ε _T matches the maximum compression ratio ε _H (ε _T = ε _H ), the process ends.
In step 4, the operating region is regulated by reducing the air amount or the fuel amount.
In step 5, the target idle speed is increased.

FIG. 8 is a diagram in which the operation region restriction in the above-described flowchart is set, that is, the operation restriction region is set in a region (high load side) other than the maximum compression ratio εH of the variable compression ratio mechanism 14. The load and the vertical axis indicate the compression ratio. The operation area and the operation restriction area are shown in the load direction.
As in this reference example, if the high load side operation region other than the operation region where the maximum compression ratio εH is set is the operation restriction region , the operation is regulated regardless of the actual compression ratio ε that is actually fixed. Made.

Next, another embodiment in the case of reducing the amount of air supplied to the engine in order to restrict the operation region when detecting a failure of the variable compression ratio mechanism 14 will be described with reference to FIGS.
Here, in step 4 of FIG. 5 described above, the opening degree of the electric throttle valve is reduced in order to reduce the amount of air supplied to the engine. However, in this embodiment, the intake valve and the exhaust valve The amount of air is reduced by reducing the overlap amount, which is the opening time.

  FIG. 9 is a cross-sectional view of the phase changing mechanism 30 for changing the valve overlap amount (valve opening / closing timing). FIG. 10 is a diagram showing that the overlap amount is reduced by setting the opening / closing timing of the intake valve from the advance side (a) to the retard side (b). FIG. 11 is a flowchart showing that the overlap amount is reduced when a failure of the variable compression ratio mechanism 14 is detected.

  The drive shaft 31 of the phase changing mechanism 30 is rotatably supported on the cylinder head side via a bearing bracket 32, and a cam pulley (or sprocket) 33 is coaxially disposed on the outer peripheral side of the drive shaft 31. Yes. The cam pulley 33 receives rotational power from the crankshaft via a chain or a timing belt, and rotates in synchronization with the crankshaft.

The phase changing mechanism 30 is provided in the rotational power transmission path between the cam pulley 33 and the drive shaft 31 and changes the rotational phase of the both 31 and 33, thereby increasing the operating angle of the intake valve. Without changing, the center phase is continuously changed within a predetermined range and held at an arbitrary phase.
More specifically, the phase changing mechanism 30 is integrally formed on the inner peripheral side of the cam pulley 33, and is fastened and fixed to the outer cylindrical portion 34 that rotates integrally with the cam pulley 33 and the drive shaft 31 via a bolt 35. The inner cylindrical portion 36 that rotates integrally with the drive shaft 31, the ring-shaped plunger 37 interposed between the outer cylindrical portion 34 and the inner cylindrical portion 36, and the plunger 37 in one direction ( And a return spring 38 that is constantly biased in the left direction in the figure. A sleeve 39 is fixed to the inner peripheral side of the outer cylindrical portion 34, and the sleeve 39 is rotatably supported by the bearing bracket 32 via a bearing 40.

  Here, the meshing portion 41 of the inner and outer peripheral surfaces of the plunger 37 and the outer peripheral surface of the inner cylindrical portion 36 and the inner peripheral surface of the outer cylindrical portion 34 is a helical spline. Therefore, by moving the plunger 37 in the axial direction (the left-right direction in the figure) of the inner and outer cylindrical portions 36 and 34 by a phase changing actuator 51 described later, the movement in the axial direction is caused to move between the inner cylindrical portion 36 and the outer cylindrical portion. It is converted into relative rotational motion with the part 34, and the relative rotational phase between the outer cylinder part 34 and the inner cylinder part 36 changes continuously.

  For example, as shown in FIG. 10, in the state where the plunger 37 is arranged in the leftmost direction in the drawing (the state shown in the figure), as shown by the waveform (b), the operating angle of the intake valve is held at the most retarded phase. The On the other hand, in the state where the plunger 37 is disposed on the rightmost side in the drawing, as shown by the waveform (a), the operating angle of the intake valve is set to the most advanced angle phase. As a result, the valve opening timing of the intake valve is set from the advance side (a) to the retard side (b) and the valve overlap is set to the small side, thereby reducing the amount of air supplied to the engine and the operating region. To regulate.

  In this example, the phase changing actuator 51 switches the operating oil pressure to the advance side hydraulic chamber 44 and the retard side hydraulic chamber 45 defined before and after the plunger 37, thereby controlling the plunger 37. Is configured as a hydraulic actuator that moves and holds the actuator at a predetermined axial position. The advance side hydraulic chamber 44 is liquid-tightly defined between one end of the plunger 37 and an end cap 43 fixed to the outer cylindrical portion 34 via a pin 42. The end cap 43, the bolt 35, The hydraulic control valve 48 is connected via oil passages 46 a, 46 b, 46 c, 46 d formed in the drive shaft 31. The retard side hydraulic chamber 45 is liquid-tightly defined on the other end side of the plunger 37 and is connected to a hydraulic control valve 48 via an oil passage 47. An oil pump 50 for supplying hydraulic oil from an oil pan 49 is connected to the hydraulic control valve 48, and the hydraulic pressure supplied to the hydraulic chambers 44 and 45 is controlled based on the control signal from the control unit 53. Is done.

Such a phase change mechanism 30 is compact and excellent in mountability to the engine, and the number of parts is suppressed to be low. Further, the central phase of the operating angle of the intake valve can be maintained at an arbitrary phase within a predetermined range, and the degree of freedom of control is higher than that in which switching control is performed at two positions, for example.
Next, control for setting the valve overlap amount small when a failure of the variable compression ratio mechanism 14 is detected will be described with reference to FIG.

In step 1, the actual compression ratio ε and the target compression ratio ε _T are read.
In step 2, it is determined whether or not the variable compression ratio mechanism 14 has failed. If there is a failure, go to Step 7. On the other hand, if there is no failure, the process is terminated.
In step 7, the overlap amount is minimized. As a result, when a failure of the variable compression ratio mechanism 14 is detected, the valve overlap amount is uniformly minimized regardless of the operating state, the amount of air supplied to the engine is reduced, and the operating region is restricted.

  According to this embodiment, the valve overlap variable mechanism (phase change mechanism) 30 that further varies the valve overlap of the intake valve or the exhaust valve is provided, and the operation region restricting means performs the valve overlap when a failure is detected. The operation area is regulated by setting to the small side. For this reason, when the failure of the variable compression ratio mechanism 14 is detected, valve piston interference can be avoided, and with variable valve timing, the amount of air can be controlled particularly at low rotation and high load where the occurrence of knocking is severe.

Configuration diagram of an internal combustion engine equipped with a variable compression ratio mechanism The figure which shows the state which changed the compression ratio by the variable compression ratio mechanism The figure which shows the state which changed the compression ratio by the variable compression ratio mechanism Compression ratio map Operation restriction area flow chart Diagram showing the operation area and the regulated operation area in the load direction Operation restriction area flow chart Diagram showing the operation area and the regulated operation area in the load direction Cross section of phase change mechanism The figure which shows the state which changed the phase of the intake valve Flowchart for setting the overlap amount to the minimum side

Explanation of symbols

1 Cylinder block 2 Cylinder 3 Piston 4 Combustion chamber 5 Upper link (first link)
6 Lower link (second link)
7 Control link (3rd link)
8 Crankshaft 9 Control shaft 14 Variable compression ratio mechanism 15 Rotating cam 17 Angle sensor 20 Drive motor 20a Worm 21 Worm wheel

Claims (5)

In an internal combustion engine that includes a variable compression ratio mechanism capable of continuously changing the compression ratio , and changes the compression ratio so that the higher the load side, the lower the compression ratio , according to the operating region.
A failure detecting means for detecting a fixing failure of the variable compression ratio mechanism;
Means for detecting the actual compression ratio (ε) at that time of the variable compression ratio mechanism in the fixed state;
When a failure is detected, the target compression ratio (εT) corresponding to the required engine load is compared with the actual compression ratio (ε), and when the target compression ratio is lower than the actual compression ratio, the air amount and the fuel amount are reduced. And an operation region restriction means for correcting and restricting the actual load of the engine so as not to enter the operation restriction region on the higher load side than the load corresponding to the actual compression ratio (ε). An internal combustion engine with a variable compression ratio mechanism. Furthermore, it has a valve overlap variable mechanism that makes the valve overlap of the intake valve or exhaust valve variable,
2. The internal combustion engine with a variable compression ratio mechanism according to claim 1, wherein the operation region restricting unit restricts the operation region by setting the valve overlap to a small side when a failure is detected. 3. The internal combustion engine with a variable compression ratio mechanism according to claim 1, wherein the idling speed is increased when a failure is detected . The internal combustion engine with a variable compression ratio mechanism according to any one of claims 1 to 3 , wherein the variable compression ratio mechanism is a multi-link type. The variable compression ratio mechanism includes a first link that is swingably connected to a piston via a piston pin, and is rotatably connected to the first link and is also rotatably connected to a crankpin portion of a crankshaft. The second link, the third link that is swingably connected to the second link and the position of the support center point is movably supported, and the position of the movable support center point of the third link is displaced. 5. An internal combustion engine with a variable compression ratio mechanism according to claim 4 , further comprising means for displacing a position of compression top dead center of the piston.

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