JP2005002931A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress or avoid the occurrence of knocking at a change-over transient time. <P>SOLUTION: This controller for an internal combustion engine has a variable compression ratio mechanism VCR capable of changing compression ratio of the engine and a valve timing change device VTC capable of changing opening and closing time of a suction valve. When it is determined that time is simultaneous change-over demand time when change-over to "ON" which is a high filling efficiency side from "OFF" of VTC and change-over to a low compression ratio side of VCR are simultaneously demanded at S15, operation advances to S16 from S15, and change-over start time of VTC is delayed by a predetermined delay period to limit its change-over. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark ignition type internal combustion engine having a variable compression ratio device and a variable intake device, and particularly suppresses occurrence of knocking when switching by a variable compression ratio device and switching by a variable intake device are requested at the same time. -It relates to technology to avoid.
[0002]
[Prior art]
In Patent Document 1, both the intake valve and the exhaust valve are provided with a valve timing changing mechanism that makes the valve timing variable, and the opening / closing timing of the intake valve and the opening / closing timing of the exhaust valve are set according to the engine speed and the engine load. It describes techniques for proper control.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-235307
[Problems to be solved by the invention]
In a spark ignition type internal combustion engine that uses a variable compression ratio device that makes the engine compression ratio variable in addition to a variable intake device that makes the intake charge efficiency of the engine variable like the valve timing changing mechanism described above, There are challenges. When starting acceleration, etc., when switching to the low compression ratio side by the variable compression ratio device and switching to the high filling efficiency side by the variable intake device are performed simultaneously, transient knocking is likely to occur, and combustion stability May be damaged. In other words, when the charging efficiency is increased by the variable intake device in response to the acceleration request, the response of the variable compression ratio device is not affected even if the variable compression ratio device is switched to the low compression ratio side at the same time to avoid the occurrence of knocking. Due to a delay or the like, knocking may easily occur transiently.
[0005]
The present invention has been made in view of such a problem, and it is possible to perform knocking in a switching transition period in which switching to a low compression ratio side by a variable compression ratio device and switching to a high charging efficiency side by a variable intake device are performed together. The main object is to provide a novel control device for an internal combustion engine that effectively suppresses and avoids the occurrence.
[0006]
[Means for Solving the Problems]
The present invention is applied to a spark ignition type internal combustion engine that includes a variable compression ratio device that makes the compression ratio of the engine variable and a variable intake device that makes the intake charge efficiency of the engine variable. When the switching to the low compression ratio side by the variable compression ratio device and the switching to the high charging efficiency side by the variable intake device are simultaneously requested, switching of the variable intake device is limited.
[0007]
【The invention's effect】
When switching to the low compression ratio side by the variable compression ratio device and switching to the high filling efficiency side by the variable intake device are requested at the same time, the switching of the variable intake device is restricted, so knocking in the transitional period Can be effectively suppressed and avoided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the same components are denoted by the same reference numerals, and redundant description is omitted as appropriate.
[0009]
FIG. 1 is a system configuration diagram showing a control device for an internal combustion engine according to first to fourth embodiments of the present invention. This internal combustion engine is roughly constituted by a cylinder head 1 and a cylinder block 2 and is provided with a spark plug 9 for spark-igniting an air-fuel mixture in a combustion chamber 4 defined above a piston 3. This is a spark ignition type internal combustion engine. As is well known, this internal combustion engine includes an intake valve 5 that opens and closes an intake port 7, an exhaust valve 6 that opens and closes an exhaust port 8, a fuel injection valve 10 that injects fuel into the intake port 7, and an intake air (not shown). A variable compression ratio mechanism (hereinafter also simply referred to as a VCR) 20 as a variable compression ratio device having a throttle valve that opens and closes the upstream side of the collector and adjusts the intake air amount, and that can change the engine compression ratio. It has.
[0010]
The ECU (engine control unit) 11 is a well-known digital computer having a CPU, ROM, RAM, and an input / output interface, and includes an accelerator opening sensor 12 that detects the accelerator opening, and a water temperature sensor 13 that detects the engine water temperature. , Based on detection signals from various sensors such as a crank angle sensor 14 for detecting the engine speed and a knock sensor 15 for detecting the presence or absence of knocking, a fuel injection valve 10, a spark plug 9, a drive device for a throttle valve, In addition, control signals are output to various actuators such as the drive device 21 of the variable compression ratio mechanism 20 to comprehensively control the fuel injection amount, fuel injection timing, ignition timing, throttle opening, engine compression ratio, and the like.
[0011]
In this example, as a variable intake device that makes the intake charge efficiency of the engine variable, at least a variable valve device that can change the closing timing of the intake valve 5, more specifically, the phase of the intake camshaft with respect to the crankshaft is changed. Thus, a valve timing changing mechanism (VTC) 5a capable of changing the opening / closing timing of the intake valve is provided. As this type of valve timing changing mechanism 5a, those using a helical spline, vane type, etc., as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-235307, are well known, and detailed description thereof is omitted.
[0012]
Referring to FIG. 18, the VCR 20 includes a lower link 24 rotatably mounted on a crankpin 23 of a crankshaft 22, an upper link 25 that links the lower link 24 and the piston 3, and an eccentric shaft 28. , And a control link 26 that links the eccentric shaft 28 and the lower link 24. When the rotational position of the control shaft 27 is changed by the driving device 21 (see FIG. 1), the motion restraint condition of the lower link 24 by the control link 26 changes, and the stroke characteristics of the piston 3, that is, the top dead of the piston 3 The point position and the engine compression ratio are continuously changed and controlled.
[0013]
FIG. 6 is a flowchart showing the flow of control according to the first embodiment of the present invention. In S (step) 11, detection signals of various sensors are read. In S12, based on the detection signal of the sensor, etc., the operation state such as the engine speed Ne and the engine load Te is calculated and determined. In S13, switching determination by the VTC 5a is performed. That is, it is determined whether or not VTC is switched based on the VTC control target value. In S14, switching determination by the VCR is performed. That is, it is determined whether or not the VCR is switched based on the VCR control target value.
[0014]
In S15, whether the switching to the low compression ratio side by the VCR as the variable compression ratio device and the switching to the high filling efficiency side by the VTC as the variable intake device are at the same time when simultaneous switching is requested. to decide. The VTC is set as a retard angle when it is “OFF”, which is the initial state, and is set as an advance angle when it is “ON”. In the advance angle setting, as compared with the retard angle setting, the amount of retardation relative to the bottom dead center of the intake closing timing is small, and the filling efficiency is high. Therefore, switching from “OFF” to “ON” of VTC is switching to the high filling efficiency side.
[0015]
The control target value of the VCR is obtained, for example, with reference to a VCR switching control map as shown in FIG. 2, which is set in advance, based on the engine speed Ne and the engine load Te. The VTC control target value is obtained, for example, based on the engine speed Ne and the engine load Te with reference to a preset switching control map for VTC as shown in FIG. For example, at the time of start acceleration that accelerates from the operation state A such as the idle state to the operation state B shown in FIGS. 2 and 3, the advance setting is performed from the retard setting OFF by the VTC so that the charging efficiency increases as the load increases. At the same time as switching to ON is required, switching from the high compression ratio setting state High-CR by the VCR to the low compression ratio setting state Low-CR is required so as to avoid the occurrence of knocking. Become.
[0016]
Referring to FIG. 6 again, when a simultaneous switching request is detected, the process proceeds from S15 to S16, and VTC switching is limited (limiting means). Specifically, as shown in FIG. 5, the VTC switching start timing is delayed by a predetermined delay period Δt. In subsequent S17, the VTC switching control is executed in consideration of the switching restriction process in S16, and in S18, the VCR switching control is executed. If there is no simultaneous switching request, the process proceeds from S15 to S17, and VTC and VCR switching control is performed in response to the request without performing the VTC switching restriction process of S16 (S17, S18).
[0017]
4 and 5 are time charts at the time of the simultaneous switching request, FIG. 4 is a comparative example without the VTC switching restriction process (S16), and FIG. 5 is the first having the VTC switching restriction process (S16). This corresponds to the embodiment. The solid line in the figure is the control target value / command value, and the broken line is the actual value that follows the command value with a response delay.
[0018]
In the comparative example shown in FIG. 4, at the timing t1 when the simultaneous switching request is made, the switching of the VTC and the switching of the VCR are started simultaneously without limiting the switching of the VTC. Therefore, during the transition period of switching, the closing timing of the intake valve is advanced before the engine compression ratio becomes sufficiently low, and knocking is likely to occur, which may impair combustion stability.
[0019]
On the other hand, in this embodiment shown in FIG. 5, at the timing t1 when the simultaneous switching request is made, the switching from the high compression ratio side to the low compression ratio side by the VCR is first preferentially started without any limitation, After a predetermined delay period Δt has elapsed, switching from OFF to ON by VTC is started. Since the VTC switching is thus limited, the occurrence of knocking in the VCR switching transition period can be effectively suppressed and avoided, and the combustion stability is improved.
[0020]
A second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, VTC switching is limited by delaying VTC switching start by a predetermined delay period Δt3 when simultaneous switching is requested, as in the first embodiment described above. The VTC switching start timing t2 or the delay period Δt3 is calculated and controlled so that the switching end timing t3 substantially coincides, in other words, the VTC switching end timing is delayed to the vicinity of the VCR switching end timing t3. Specifically, when the simultaneous switching request is detected in S15 of FIG. 8, the process proceeds to S16a, and the VTC switching end time t3 is set. This t3 can be calculated and set from the VCR switching start timing t1 and the switching period Δt1. In the subsequent S16b, the VTC switching start timing t2 or the delay period Δt3 is calculated based on the VCR switching period Δt1 and the VTC switching period Δt2. Based on the obtained t2 or Δt3, switching of VTC is restricted (S17).
[0021]
According to the second embodiment, as in the first embodiment, the switching end timing of both the VCR and the VTC is controlled while restricting the switching of the VTC at the time of the simultaneous switching request and effectively suppressing and avoiding the occurrence of knocking. Can be set substantially at the same time, and the switching responsiveness is not substantially lowered in spite of delaying the VTC switching start timing.
[0022]
A third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, by switching the VTC switching speed, the switching of the VTC is restricted and the switching end timing t3 of the VCR and the VTC is made substantially the same as in the second embodiment. Specifically, if it is determined in step 15 of FIG. 10 that simultaneous switching is requested, the process proceeds to S16c, where the VTC switching speed or the switching speed decreases so that the VCR and VTC switching end timings t3 substantially coincide. The amount is set. According to the third embodiment, similarly to the second embodiment, it is possible to effectively suppress and avoid the occurrence of knocking in the switching transition period without causing a decrease in switching response.
[0023]
A fourth embodiment of the present invention will be described with reference to FIG. In a configuration in which the VCR can be switched continuously or in three or more stages, the degree of limitation of VTC switching is changed / controlled according to the switching amount of the compression ratio. For example, the VTC delay period Δt4 when switching from the medium compression ratio setting state Middle-CR to the low compression ratio setting state Low-CR is changed from the high compression ratio setting state High-CR to the low compression ratio setting state Low-CR. Is set to be shorter than the delay periods Δt (FIG. 5) and Δt3 (FIG. 7) of the VTC when switching to. That is, the smaller the compression ratio switching amount, the smaller the VTC switching restriction degree, and the larger the compression ratio switching amount, the larger the VTC switching restriction degree. Thereby, switching of VTC can be more appropriately limited according to the switching amount of the compression ratio.
[0024]
A fifth embodiment of the present invention will be described with reference to FIGS. In the fifth embodiment, instead of the valve timing changing mechanism (VTC) 5a shown in FIG. 1, the intake branch passages 7c and 7d that branch on the downstream side of the intake collector 7b are used as variable intake devices that make the intake charge efficiency variable. An intake passage switching device that makes intake charge efficiency variable by switching and using is used. Referring to FIG. 12, this intake passage switching device includes a main intake port 7d and a sub intake port 7c as intake branch passages that branch downstream of intake collector 7b, and an intake port switching valve that opens and closes main intake port 7d. 16 and a drive device 16a for driving the switching valve 16. The operation of the driving device 16a is controlled by a command signal from the ECU 11.
[0025]
Referring to FIG. 13, when switching to the low compression ratio side of the VCR and switching from “open” to “closed” (switching to the high charging efficiency side) by the intake port switching valve 16 are required at the same time. The intake port switching valve switching start time is delayed by a predetermined delay period Δt5 to limit the switching of the intake port switching valve.
[0026]
Specifically, as shown in FIG. 14, in S13d, switching of the intake ports 7c, 7d by the switching valve 16a is determined, and in S14, switching determination of the VCR is performed. In S15d, there is a simultaneous switching request in which switching from "open" to "closed" by the switching valve 16, that is, switching to the auxiliary intake port 7c and switching to the low compression ratio side by the VCR are simultaneously required. Determine whether. If it is determined that the simultaneous switching is requested, the process proceeds to S16d, where the switching start time to the “closed” side by the switching valve 16 is delayed by a predetermined delay period Δt5, and switching by the switching valve 16 as the variable intake device is performed. Restrict.
[0027]
Even when the intake passage switching device is used as the variable intake device as in the fourth embodiment, substantially the same operations and effects as when the VTC is used can be obtained.
[0028]
A sixth embodiment of the present invention will be described with reference to FIGS. In the sixth embodiment, a supercharger (the exhaust bypass valve 18a) is used as a variable intake device that makes intake charge efficiency variable. As is well known, this supercharger includes a compressor 17 and an exhaust turbine 18, and an exhaust bypass valve 18a serving as a waste gate (W / G) valve that opens and closes an exhaust bypass passage 18b that bypasses the exhaust turbine 18. And a drive unit 18c for driving the exhaust bypass valve 18a. A supercharging pressure sensor 30 that detects the supercharging pressure is provided in the intake passage on the downstream side of the throttle valve 19. The ECU 11 outputs a control signal to the drive device 18c of the exhaust bypass valve 18a and the drive device 19a of the throttle valve 19 based on detection signals of various sensors, and controls its operation.
[0029]
The exhaust bypass valve 18a is originally controlled to “open” for the purpose of escaping excess exhaust when the engine is at high speed and high load. However, the exhaust gas flow rate is relatively low. At high loads, the “closed” side is controlled to increase the efficiency of the exhaust turbine 18. Further, since there is no need to perform supercharging by driving the exhaust turbine 18 at low load, it is set to the “open” side in order to quickly exhaust the exhaust. When accelerating mainly at low speed, the engine is controlled so as to drive the exhaust turbine 18 by switching the exhaust bypass valve 18a from the “open” side to the “closed” side to increase the charging efficiency of the intake air. Therefore, in this embodiment, as shown in FIG. 16, simultaneous switching is required for both switching from "open" to "closed" by the exhaust bypass valve 18a and switching to the low compression ratio side of the VCR. At the request time t1, the switching start timing of the exhaust bypass valve 18a to the “closed” side is delayed by a predetermined delay period Δt6 to suppress / avoid knocking in the switching transition period.
[0030]
Specifically, as shown in FIG. 17, the switching determination of the exhaust bypass valve 18a is performed in S13e, and the switching of the VCR is determined in S14e. In S15e, a simultaneous switching request is requested in which both the switching to the “closed” direction by the exhaust bypass valve 18a and the switching to the low compression ratio side of the VCR are required. If it is determined that the simultaneous switching is requested, the process proceeds to S16e, where the switching of the exhaust bypass valve 18a in the “closed” direction is delayed by a predetermined delay period Δt6, and the exhaust bypass valve 18a of the supercharger as the variable intake device is delayed. Limit switching. In S17e, the opening degree of the exhaust bypass valve 18a is controlled in consideration of the switching restriction process in S16e. If it is not at the time of simultaneous switching request, the process proceeds from S15e to S17e without performing the process of S16e.
[0031]
In the sixth embodiment, unlike the first to fifth embodiments described above, the VCR switching process (S18) is performed before the determination of the simultaneous switching request in S15e. There is no problem because the switching control is not limited.
[0032]
As described above, also in the sixth embodiment using the supercharger as the variable intake device, it is possible to effectively avoid and suppress the occurrence of knocking at the time of the simultaneous switching request as in the above-described embodiment.
[0033]
As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above embodiments, and includes various modifications and changes without departing from the spirit of the present invention. For example, a technique of controlling the switching restriction degree by the variable intake device according to the amount of compression ratio conversion by the variable compression ratio device as in the fourth embodiment can be applied to other embodiments.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a control device for an internal combustion engine provided with a valve timing changing mechanism according to first to fourth embodiments of the present invention.
FIG. 2 is a switching control map of a variable compression ratio mechanism.
FIG. 3 is a switching control map of a valve timing changing mechanism.
FIG. 4 is a time chart at the time of simultaneous switching request according to a comparative example.
FIG. 5 is a time chart at the time of simultaneous switching request according to the first embodiment.
FIG. 6 is a flowchart showing a flow of control according to the first embodiment.
FIG. 7 is a time chart at the time of a simultaneous switching request according to the second embodiment.
FIG. 8 is a flowchart showing a flow of control according to the second embodiment.
FIG. 9 is a time chart at the time of a simultaneous switching request according to the third embodiment.
FIG. 10 is a flowchart showing a flow of control according to the third embodiment.
FIG. 11 is a flowchart showing a flow of control according to a fourth embodiment.
FIG. 12 is a system configuration diagram showing a control device for an internal combustion engine including an intake passage switching device according to a fifth embodiment of the present invention.
FIG. 13 is a time chart at the time of simultaneous switching request according to the fifth embodiment.
FIG. 14 is a flowchart showing a flow of control according to the fifth embodiment.
FIG. 15 is a system configuration diagram showing a control device for an internal combustion engine including a supercharger according to a sixth embodiment of the present invention.
FIG. 16 is a time chart at the time of simultaneous switching request according to the sixth embodiment;
FIG. 17 is a flowchart showing a flow of control according to the sixth embodiment.
FIG. 18 is a configuration diagram showing a variable compression ratio mechanism as a variable compression ratio device.
[Explanation of symbols]
5a ... Valve timing changing mechanism (variable intake device)
16a ... Intake port switching valve (variable compression ratio device)
18a ... Exhaust bypass valve (variable compression ratio device)
20 ... Variable compression ratio mechanism (variable compression ratio device)

Claims (9)

In a control device applied to a spark ignition type internal combustion engine having a variable compression ratio device that makes the compression ratio of the engine variable, and a variable intake device that makes the intake charge efficiency of the engine variable,
Limiting means for restricting switching of the variable intake device at the time of simultaneous switching request for simultaneously switching to the low compression ratio side by the variable compression ratio device and switching to the high filling efficiency side by the variable intake device A control apparatus for an internal combustion engine, comprising: 2. The control apparatus for an internal combustion engine according to claim 1, wherein the limiting means delays the switching start timing of the variable intake device by a predetermined delay period. 3. The control device for an internal combustion engine according to claim 1 or 2, wherein the limiting means delays the switching end timing of the variable intake device to the vicinity of the switching end timing of the variable compression ratio device. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the limiting means reduces a switching speed of the variable intake device. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the restriction device controls a switching restriction degree of the variable intake device in accordance with a switching amount of the variable compression ratio device. The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the variable intake device is a variable valve device that makes at least the closing timing of the intake valve variable. 7. The control apparatus for an internal combustion engine according to claim 6, wherein the variable valve operating mechanism is a valve timing changing mechanism that controls the opening / closing timing of the intake valve by making the phase of the camshaft relative to the crankshaft variable. . 6. The control device for an internal combustion engine according to claim 1, wherein the variable intake device is a passage switching device that switches a plurality of intake branch passages branched from an intake collector. 6. The control apparatus for an internal combustion engine according to claim 1, wherein the variable intake device is a supercharger provided with an exhaust bypass valve.

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