JP2010185416A - Device and method for controlling engine compression ratio - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for controlling engine compression ratio that can prevent the occurrence of knocking and pre-ignition even when starting from idling during the stop of a vehicle. <P>SOLUTION: The engine compression ratio control device capable of changing a mechanical compression ratio by the operation of an actuator (51) includes a start predicting section for predicting a driver's start demand prior to an actual start demand (S3), and a compression ratio adjusting section for reducing the mechanical compression ratio by operating the actuator 51 when predicting the driver's start demand (S12). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and method for controlling the compression ratio of an engine.

  Engines that can change the mechanical compression ratio have been studied. In Patent Document 1, when the load is low, the compression ratio is increased to improve fuel efficiency, and when the amount of change in intake air amount per unit time increases, that is, when the engine is in an accelerated state, the compression ratio is decreased to prevent knocking. I am doing so.

JP-A-63-159630

  However, as in Patent Document 1, the present inventors have found that knocking and pre-ignition (so-called pre-ignition) cannot always be prevented even if the compression ratio is lowered based on the amount of change in the intake air amount per unit time. It was discovered.

  That is, when the driver depresses the accelerator pedal, the intake throttle opens in conjunction with the accelerator pedal. Even if the compression ratio is lowered because the amount of change in the intake air amount per unit time has increased, immediately after the air amount has increased, the control to lower the compression ratio is not in time, and knocking and pre-ignition may occur. there were. In particular, when starting from idling while the vehicle is stopped, the throttle is opened after the accelerator pedal is depressed, and a large amount of air flows into the combustion chamber at a low engine speed. At this time, since the air-fuel mixture is compressed over a relatively long time with a high compression ratio, the inventors have found that knocking and pre-ignition are likely to occur.

  The present invention has been made paying attention to such conventional problems, and is an engine compression capable of preventing knocking and pre-ignition even when starting from idling while the vehicle is stopped. It is an object of the present invention to provide a ratio control device and a compression ratio control method.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is an engine compression ratio control device capable of changing a mechanical compression ratio by operating an actuator (51), and a start prediction unit (90) for predicting a driver's start request prior to an actual start request; And a compression ratio adjusting section (90) for lowering the mechanical compression ratio by operating the actuator (51) when a driver's start request is predicted.

  According to the present invention, since the mechanical compression ratio is reduced when the start request is predicted prior to the actual start request of the driver, even when starting from idling while the vehicle is stopped, The occurrence of ignition can be prevented.

It is a figure which shows the variable compression ratio engine which the compression ratio control apparatus by this invention controls. It is a figure explaining the compression ratio change method by a multiple link type variable compression ratio engine. It is a flowchart which shows the main routine of control in 1st Embodiment of the compression ratio control apparatus by this invention. It is a time chart when 1st Embodiment is performed. It is a time chart when 2nd Embodiment is performed. It is a time chart when 3rd Embodiment is performed.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a variable compression ratio engine controlled by a compression ratio control apparatus according to the present invention.

  First, a variable compression ratio engine controlled by the compression ratio control apparatus according to the present invention will be described. This engine is a variable compression ratio engine (hereinafter referred to as a “multi-link variable compression ratio engine”) having a multi-link mechanism in which a piston and a crankshaft are connected by two links.

  The multi-link variable compression ratio engine 10 connects the piston 32 and the crankshaft 33 with two links (an upper link (first link) 11 and a lower link (second link) 12) and a control link (third The link) 13 controls the lower link 12 to adjust the positions of the top dead center and the bottom dead center to change the mechanical compression ratio.

  The upper link 11 has an upper end connected to the piston 32 via the piston pin 21 and a lower end connected to one end of the lower link 12 via the connection pin 22. The piston 32 receives the combustion pressure and reciprocates in the cylinder 31 a of the cylinder block 31.

  One end of the lower link 12 is connected to the upper link 11 via a connecting pin 22, and the other end is connected to the control link 13 via a connecting pin 23. Further, the lower link 12 swings around the crank pin 33b as a central axis by inserting the crank pin 33b of the crank shaft 33 into a substantially central connecting hole. The lower link 12 is divided into two left and right members. The crankshaft 33 includes a plurality of journals 33a and a crankpin 33b. The journal 33 a is rotatably supported by the cylinder block 31 and the ladder frame 34. The crank pin 33b is eccentric from the journal 33a by a predetermined amount, and the lower link 12 is swingably connected thereto.

  The control link 13 is connected to the lower link 12 via a connecting pin 23. The other end of the control link 13 is connected to the control shaft 25 via a connecting pin 24. The control link 13 swings around the connecting pin 24. A gear is formed on the control shaft 25, and the gear meshes with a pinion 53 provided on the rotating shaft 52 of the electric actuator 51. The control shaft 25 is rotated by the electric actuator 51, and the connecting pin 24 moves.

  An air flow sensor 61, a throttle valve 62, and a fuel injection valve 63 are provided in the intake passage 60 of the engine 10. The air flow sensor 61 detects a fresh air amount. The throttle valve 62 adjusts the amount of fresh air according to the opening. The fuel injection valve 63 injects fuel.

  An exhaust gas recirculation (EGR) device 71 is provided in the exhaust passage 70 of the engine 10. Part of the exhaust gas flowing through the exhaust passage 70 is recirculated to the intake passage 60 via the EGR device 71. The EGR device 71 includes an EGR control valve 71a and an EGR passage 71b. The EGR control valve 71a adjusts the amount of EGR gas according to the opening degree.

  The controller 90 controls the electric actuator 51 to rotate the control shaft 25 to change the compression ratio. The controller 90 controls the fuel injection of the fuel injection valve 41 provided in the intake port. Further, the controller 90 controls the ignition timing of the ignition plug 42 provided on the cylinder head. The controller 90 controls the EGR control valve 71a to adjust the EGR amount. The controller 90 determines the engine load and performs control according to the load. The controller 90 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 90 may be composed of a plurality of microcomputers.

  FIG. 2 is a diagram for explaining a compression ratio changing method by a multi-link variable compression ratio engine.

  The multi-link variable compression ratio engine can change the mechanical compression ratio by rotating the control shaft 25 and changing the position of the connecting pin 24. For example, as shown in FIGS. 2 (A) and 2 (C), when the connecting pin 24 is set to the position A, the top dead center position (TDC) is increased and a high compression ratio is obtained.

  As shown in FIGS. 2B and 2C, when the connecting pin 24 is set to the position B, the control link 13 is pushed upward and the position of the connecting pin 23 is raised. As a result, the lower link 12 rotates counterclockwise about the crank pin 33b, the connecting pin 22 is lowered, and the position of the piston 32 at the piston top dead center (TDC) is lowered. Therefore, the compression ratio becomes a low compression ratio.

  As described above, in the conventional method, when the driver depresses the accelerator pedal, the intake throttle opens in conjunction with the accelerator pedal. Even if the compression ratio is lowered because the amount of change in the intake air amount per unit time has increased, the control for lowering the compression ratio may not be in time immediately after the air amount has increased. In particular, when starting from idling while the vehicle is stopped, the throttle is opened after the accelerator pedal is depressed, and a large amount of air flows into the combustion chamber at a low engine speed. At this time, since the air-fuel mixture is compressed over a relatively long time with a high compression ratio, the inventors have found that pre-ignition is likely to occur. Therefore, in the present embodiment, the compression ratio change control is started based on the brake pedal depressing operation prior to the actual start request (that is, the driver's accelerator pedal depressing operation). Hereinafter, specific control contents will be described.

  FIG. 3 is a flowchart showing a main routine of control in the first embodiment of the compression ratio control apparatus according to the present invention.

  The controller 90 starts this control when the vehicle is stopped and the engine is idling, and repeatedly executes it in a minute time (for example, 10 millisecond) cycle. During idle operation, the compression ratio is set high to reduce fuel consumption. The initial value of the target compression ratio targetε is the minimum compression ratio minimumε determined from the structure. The initial delay time is also set in advance.

  In step S1, the controller 90 detects the current compression ratio actualε. For this detection, for example, the position of the connecting pin 24 may be directly detected using a sensor to detect the compression ratio actualε. Alternatively, the compression ratio actualε may be detected by indirectly detecting the position of the connecting pin 24 based on a command signal to the electric actuator 51.

  In step S2, the controller 90 determines whether or not the current compression ratio actualε matches the target compression ratio targetε. If they match, the process proceeds to step S10, and if not, the process proceeds to step S3.

  In step S3, the controller 90 predicts whether or not there is a driver's start request prior to the actual start request. Specifically, for example, it may be predicted that there is a start request when the force with which the driver steps on the brake pedal becomes zero. If a start request is predicted, the process proceeds to step S4, and if not, the process proceeds to step S10.

  In step S4, the controller 90 determines whether or not there is a change in the driver's required torque. Specifically, for example, when the driver's accelerator pedal depression amount changes, it may be determined that the required torque has changed. If there is a change in the required torque, the process proceeds to step S5, and if not, the process proceeds to step S6.

  In step S5, the controller 90 sets a target compression ratio targetε according to the driver's required torque. Specifically, it may be set in the map through experiments in advance. To explain the tendency, the target compression ratio targetε is set to be smaller as the driver depresses the accelerator pedal more greatly like a sudden start. When the driver depresses the accelerator pedal small, such as slowly starting and running at a low vehicle speed, the target compression ratio targetε is set large. Further, if the outside air temperature, the cooling water temperature, etc. are taken into consideration, a more appropriate target compression ratio targetε can be set.

  In step S6, the controller 90 determines whether or not the current compression ratio actualε is greater than the target compression ratio targetε. If it is larger, the process proceeds to step S12, and if not, the process proceeds to step S7.

  In step S7, the controller 90 determines whether or not the difference between the target compression ratio targetε and the current compression ratio actualε (targetε-actualε) is larger than the reference value. In addition, although 1 is illustrated as a reference value here, what is necessary is just to set suitably. If it is larger than the reference value, the process proceeds to step S9; otherwise, the process proceeds to step S8.

  In step S8, the controller 90 determines whether or not the delay time has elapsed. The process proceeds to step S10 until the time has elapsed, and the process proceeds to step S11 when the time has elapsed.

  In step S9, the controller 90 sets zero for the delay time.

  In step S10, the controller 90 maintains the current compression ratio.

  In step S11, the controller 90 operates the electric actuator 51 so that the compression ratio increases.

  In step S12, the controller 90 operates the electric actuator 51 so that the compression ratio decreases.

  FIG. 4 is a time chart when the first embodiment is executed. In addition, the step number of the flowchart is shown with S to make it easy to understand the correspondence with the flowchart.

  First, the case where the target compression ratio targetε set according to the driver's required torque is small (that is, the accelerator pedal is depressed relatively large) will be described with reference to FIG.

  First, a broken line comparison mode will be described.

  In this comparative mode, the compression ratio change control is started at time t1 when the driver depresses the accelerator pedal. In this way, as described above, knocking and pre-ignition are likely to occur particularly when starting from idling while the vehicle is stopped.

  On the other hand, in the present embodiment shown by the solid line, the compression ratio change control is started based on the brake pedal depressing operation prior to the actual start request (that is, the driver's accelerator pedal depressing operation). This will be described in detail below.

  Initially, the controller 90 repeats steps S 1 → S 2 → S 3 → S 10 to maintain the current compression ratio.

  When the driver removes his / her foot from the brake pedal at time t0, the controller 90 predicts the driver's start request and proceeds from step S3 to step S4. At this point, the driver does not step on the accelerator pedal, so the required torque does not change. At this time, the current compression ratio actualε is larger than the target compression ratio targetε (set to the minimum compression ratio minimumε at this time). Therefore, the controller 90 repeatedly performs steps S1, S2, S3, S4, S6, and S12. Then, the compression ratio gradually decreases.

  When the driver depresses the accelerator pedal relatively large at time t1 and the required torque changes, the controller 90 shifts the processing from step S4 to step S5, and sets the target compression ratio targetε according to the driver's required torque. In FIG. 4A, a target compression ratio targetε lower than the compression ratio at time t1 is set. Therefore, the controller 90 repeatedly performs steps S1, S2, S3, S4, S6, and S12 after the next cycle. Then, the compression ratio gradually decreases.

  When the compression ratio matches the target compression ratio targetε at time t2, the controller 90 shifts the processing from step S2 to step S10 and maintains the current compression ratio.

  Next, with reference to FIG. 4B, a case where the target compression ratio targetε set according to the driver's required torque is large (that is, the accelerator pedal is depressed only slightly) will be described.

  The process until time t1 is the same as that in FIG.

  When the driver depresses the accelerator pedal very slightly at time t1 and the required torque changes, the controller 90 proceeds from step S4 to step S5 to set the target compression ratio targetε according to the driver's required torque. In FIG. 4B, the target compression ratio targetε is higher than the compression ratio at time t1, and the difference (targetε-actualε) between the target compression ratio targetε and the current compression ratio actualε is larger than the reference value 1. Was set. Therefore, after the next cycle, the controller 90 repeatedly performs steps S1, S2, S3, S4, S6, S7, S9, and S11. After the difference between the target compression ratio targetε and the current compression ratio actualε (targetε-actualε) becomes smaller than the reference value 1, the controller 90 performs steps S1, S2, S3, S4, S6, S7, S8, and so on. S11 is repeatedly processed. As a result, the compression ratio gradually increases.

  When the compression ratio matches the target compression ratio targetε at time t3, the controller 90 shifts the processing from step S2 to step S10 and maintains the current compression ratio.

  Next, a case where the target compression ratio targetε set according to the driver's required torque is slightly large (that is, the accelerator pedal is depressed relatively small) will be described with reference to FIG.

  The process until time t1 is the same as that in FIG.

  When the driver depresses the accelerator pedal relatively small at time t1 and the required torque changes, the controller 90 shifts the process from step S4 to step S5, and sets the target compression ratio targetε according to the driver's required torque. In FIG. 4C, the target compression ratio targetε is higher than the compression ratio at time t1 and the difference (targetε-actualε) between the target compression ratio targetε and the current compression ratio actualε is smaller than the reference value 1. Was set. Therefore, after the next cycle, the controller 90 repeatedly performs steps S1, S2, S3, S4, S6, S7, S8, and S10. Then, the current compression ratio is maintained.

  After a predetermined delay time has elapsed at time t4, the controller 90 repeatedly performs steps S1, S2, S3, S4, S6, S7, S8, and S11. As a result, the compression ratio gradually increases.

  When the compression ratio matches the target compression ratio targetε at time t5, the controller 90 shifts the processing from step S2 to step S10, and maintains the current compression ratio.

  According to the present embodiment, the compression ratio change control is started based on the brake pedal depressing operation prior to the actual start request (that is, the driver's accelerator pedal depressing operation). For this reason, even when starting from idling while the vehicle is stopped, knocking and pre-ignition can be prevented.

  Also, after the true target compression ratio targetε is set based on the driver's accelerator pedal depression operation, if the target compression ratio targetε is very large, the control is immediately switched to increase the compression ratio. Can be minimized.

  Further, if the target compression ratio targetε is slightly high, even if the actual compression ratio is different from the target compression ratio, the cost of deterioration of fuel consumption is small. Therefore, in this case, the current compression ratio was maintained for the time being. If there is a change in the driver's required torque (that is, if the accelerator pedal is re-operated), the target compression ratio targetε is set again and the compression ratio change control is executed. At this time, since the current compression ratio is maintained, the target compression ratio after the reset can be quickly dealt with.

(Second Embodiment)
FIG. 5 is a time chart when the second embodiment is executed.

  During idle operation, the EGR control valve 71a is opened and a part of the exhaust gas flowing through the exhaust passage 70 is recirculated to the intake passage 60. Therefore, EGR gas exists in the intake collector and the intake port. .

  Even if the EGR control valve 71a is closed at the time t1 when the driver depresses the accelerator pedal as in the comparative example shown by the broken line in FIG. 5, EGR gas flows into the engine cylinder for several cycles.

  In contrast, in the present embodiment shown by the solid line in FIG. 5, the EGR control valve 71a is closed to stop EGR at time t0 when the driver's start request is predicted. As a result, when the driver depresses the accelerator pedal, there is no EGR gas and fresh air is drawn into the engine, so the acceleration performance is good.

(Third embodiment)
FIG. 6 is a time chart when the third embodiment is executed.

  In the present embodiment shown by the solid line in FIG. 6, at the time t0 when the driver's start request is predicted, the drive voltage of the electric actuator 51 is increased from the normal time so that the electric actuator 51 is operated at a higher speed than the normal time. did. Since it did in this way, a compression ratio can be reduced faster than the case of 1st Embodiment shown with a dashed-dotted line in FIG.

  When the compression ratio at which pre-ignition can be reliably prevented (for example, 10; this is referred to as a boost stop compression ratio) is reached, the boost is stopped. Since it did in this way, the increase in the electrical load (deterioration of fuel consumption) accompanying boosting can be minimized.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the above embodiment, it is predicted that there is a start request when the force with which the driver steps on the brake pedal becomes zero. However, the present invention is not limited to this, and it may be predicted that there is a start request when the driver operates the shift lever from the P range or the N range to the D range. In the case of a manual transmission vehicle, it may be predicted that there is a start request when the driver steps on the clutch pedal.

  Further, when the compression ratio is lowered, the thermal efficiency is lowered as the compression ratio is lowered, and the output torque of the engine is lowered, so that the rotation may be lowered. Therefore, it is advisable to advance the ignition timing as the compression ratio is lowered.

  Further, the present invention may be executed whenever the vehicle is started, but may be executed only when knocking or pre-ignition is particularly likely to occur. For example, the case where the intake air temperature or the coolant temperature is higher than the assumed temperature is applicable.

  Furthermore, execution / stop may be performed according to the octane number of the fuel supplied to the engine. In other words, so-called high-octane gasoline having a high octane number is less likely to cause knocking or pre-ignition than ordinary regular gasoline. Therefore, the present invention is not executed when gasoline with a high octane number is used, but when it is used with regular gasoline, unnecessary fuel consumption deterioration can be prevented.

10 Multi-link variable compression ratio engine 11 Upper link (first link)
12 Lower link (second link)
13 Control link (3rd link)
25 Control shaft 32 Piston 33 Crankshaft 33a Journal 33b Crankpin 51 Actuator 60 Intake passage 70 Exhaust passage 71 EGR device 71a EGR control valve 90 Controller Step S1 Compression ratio detection unit / Compression ratio detection step Step S3 Start prediction unit / Start prediction step Step S4 Start request detecting unit / start request detecting step Step S5 Target compression ratio setting unit / Target compression ratio setting step Steps S10, S11, S12 Compression ratio adjusting unit / Compression ratio adjusting step

Claims (17)

An engine compression ratio control device capable of changing a mechanical compression ratio by operation of an actuator,
A start prediction unit that predicts a driver's start request prior to the actual start request;
A compression ratio adjusting unit that lowers the mechanical compression ratio by operating the actuator when a driver's start request is predicted;
An engine compression ratio control device comprising: A compression ratio detector for detecting the current mechanical compression ratio;
A start request detector for detecting the actual start request of the driver;
A target compression ratio setting unit that sets a target mechanical compression ratio based on the engine operating state when an actual start request of the driver is detected;
With
The compression ratio adjustment unit adjusts the mechanical compression ratio by operating the actuator according to the difference between the set target mechanical compression ratio and the current mechanical compression ratio.
The engine compression ratio control apparatus according to claim 1. The compression ratio adjustment unit continues to decrease the mechanical compression ratio when the set target mechanical compression ratio is smaller than the current mechanical compression ratio.
The engine compression ratio control device according to claim 2. The compression ratio adjusting unit increases the mechanical compression ratio when the set target mechanical compression ratio is larger than the current mechanical compression ratio.
The engine compression ratio control device according to claim 2 or claim 3, wherein The compression ratio adjustment unit immediately increases the mechanical compression ratio when the difference between the set target mechanical compression ratio and the current mechanical compression ratio is greater than a predetermined value.
The engine compression ratio control device according to any one of claims 2 to 4, wherein the engine compression ratio control device is provided. When the difference between the set target mechanical compression ratio and the current mechanical compression ratio is smaller than a predetermined value, the compression ratio adjustment unit waits for the delay time to elapse and increases the mechanical compression ratio.
The engine compression ratio control device according to any one of claims 2 to 5, wherein It has an intake air temperature detector that detects the temperature of the air taken into the engine,
The compression ratio adjustment unit reduces the mechanical compression ratio when the driver's start request is predicted and the intake air temperature is higher than a predetermined value.
The engine compression ratio control apparatus according to any one of claims 1 to 6, wherein the engine compression ratio control apparatus is configured as described above. A cooling water temperature detector that detects the cooling water temperature of the engine
The compression ratio adjustment unit is a case where a driver's start request is predicted, and when the cooling water temperature is higher than a predetermined value, the mechanical compression ratio is reduced.
The engine compression ratio control apparatus according to any one of claims 1 to 7, wherein the engine compression ratio control apparatus is configured as described above. It has an octane number detection unit that detects the octane number of the fuel supplied to the engine,
The compression ratio adjustment unit is a case where a driver's start request is predicted and the mechanical compression ratio is reduced when the octane number is smaller than a predetermined value.
The engine compression ratio control apparatus according to any one of claims 1 to 8, wherein the compression ratio control apparatus for an engine is provided. The actuator is an electric actuator,
When the driver's start request is predicted, the driving speed of the electric actuator is increased from the normal time, and an actuator speed adjusting unit that operates the electric actuator at a higher speed than the normal time is provided.
The engine compression ratio control apparatus according to any one of claims 1 to 9, wherein the engine compression ratio control apparatus is characterized by the above. The actuator speed adjustment unit operates the electric actuator at a normal speed when the mechanical compression ratio becomes smaller than a predetermined value.
The engine compression ratio control apparatus according to claim 10. When the driver's start request is predicted, an EGR adjustment unit that stops the exhaust gas that is recirculated is provided.
The engine compression ratio control apparatus according to any one of claims 1 to 11, wherein the engine compression ratio control apparatus is characterized in that: When the driver's start request is predicted, an ignition timing adjustment unit is provided that corrects the ignition timing until the driver's actual start request is detected.
The engine compression ratio control apparatus according to any one of claims 1 to 12, wherein the engine compression ratio control apparatus is characterized by that. The start prediction unit predicts a start request based on a brake pedal operated by a driver,
The engine compression ratio control apparatus according to any one of claims 1 to 13, wherein the engine compression ratio control apparatus is provided. The start prediction unit predicts a start request based on a shift lever operated by a driver.
The engine compression ratio control apparatus according to any one of claims 1 to 13, wherein the engine compression ratio control apparatus is provided. The start prediction unit predicts a start request based on a clutch pedal operated by a driver.
The engine compression ratio control apparatus according to any one of claims 1 to 13, wherein the engine compression ratio control apparatus is provided. An engine compression ratio control method capable of changing a mechanical compression ratio by operating an actuator,
A start prediction process for predicting a driver's start request prior to the actual start request;
A compression ratio adjusting step of lowering the mechanical compression ratio by operating the actuator when the driver's start request is predicted;
An engine compression ratio control method comprising:

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