JP2014224462A - Control device and control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compatibly attain the homogenization and ignitability of air-fuel mixture.SOLUTION: A control device for an internal combustion engine includes a port-injection fuel injection valve (41) for injecting fuel into an intake port, a cylinder-injection fuel injection valve (8) for injecting fuel into a combustion chamber, a variable compression ratio mechanism (2) for changing a relative position relationship between a piston and a cylinder to vary a mechanical compression ratio, and a flow control valve (50) for varying an in-cylinder flow. Under predetermined operating conditions, the control device performs cooperative control of the sharing rate of cylinder injection to port injection, the compression ratio and the in-cylinder flow to produce the homogenization and ignitability of air-fuel mixture at a predetermined level.

Description

  The present invention relates to a control device and a control method for an internal combustion engine that use both a port injection fuel injection valve that injects fuel into an intake port and an in-cylinder injection fuel injection valve that injects fuel into a combustion chamber.

  A port injection fuel injection valve that injects fuel into the intake port and an in-cylinder injection fuel injection valve that directly injects fuel into the combustion chamber are used in combination, and the two are switched appropriately according to engine operating conditions. An internal combustion engine provided with a fuel injection device is described in Patent Document 1. In Patent Document 1, a change in the share ratio between port injection and in-cylinder injection is controlled as the engine temperature rises after the internal combustion engine is started.

JP 2008-25502 A

  In order to improve combustibility and suppress the discharge of unburned fuel, it is effective to increase the port injection share ratio and improve the homogeneity of the mixture, but the port injection share ratio is increased. Then, there exists a demerit that ignitability (ignition ease) falls. For this reason, it is difficult to achieve both the homogeneity and the ignitability simply by adjusting the share ratio between the port injection and the in-cylinder injection.

  The present invention has been made in view of such circumstances. That is, the present invention relates to a machine by changing the relative positional relationship between a port injection fuel injection valve that injects fuel into an intake port, a cylinder injection fuel injection valve that injects fuel into a combustion chamber, and a piston and a cylinder. In a control device for an internal combustion engine comprising a variable compression ratio mechanism that varies a typical compression ratio and a flow device that varies in-cylinder flow, a predetermined level of air-fuel mixture homogeneity under predetermined operating conditions In order to obtain ignitability, the sharing ratio between the in-cylinder injection and the port injection, the compression ratio, and the in-cylinder flow are controlled in a coordinated manner.

  For example, in order to improve the homogeneity, at least one of the reduction of the compression ratio, the increase of the share ratio of the port injection, and the enhancement of the in-cylinder flow are performed. Further, when improving the ignitability, at least one of a reduction in the compression ratio, an increase in the ratio of in-cylinder injection, and a reduction in in-cylinder flow are performed.

  According to the present invention, a predetermined level of air-fuel mixture is obtained by cooperatively controlling the sharing ratio, the compression ratio, and the in-cylinder flow, for example, under predetermined operating conditions such as during fast idling where warm-up operation is performed after cold start. It is possible to achieve both the homogeneity and the ignitability.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows the system structure of the control apparatus which concerns on one Example of this invention. Explanatory drawing which shows the relationship of ignition ease (A) and homogeneity (B) with respect to a compression ratio and a share. Explanatory drawing which shows the relationship of ignition ease (A) and homogeneity (B) with respect to flow strength and a share rate. Explanatory drawing which shows an example of the cooperative control of a present Example when a homogeneity is low. Explanatory drawing which shows an example of the cooperative control of a present Example when ignition ease is low.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a system configuration of an automotive internal combustion engine 1 to which an embodiment of the present invention is applied. This internal combustion engine 1 is a spark ignition internal combustion engine with a turbocharger of a 4-stroke cycle equipped with a variable compression ratio mechanism 2 using, for example, a multi-link type piston crank mechanism. The intake valve 4 and a pair of exhaust valves 5 are disposed, and a spark plug 6 is disposed in a central portion surrounded by the intake valves 4 and the exhaust valves 5.

  A cylinder injection fuel injection valve 8 that directly injects fuel into the combustion chamber 3 is disposed below the intake port 7 that is opened and closed by the intake valve 4. The intake port 7 is provided with a port injection fuel injection valve 41 that injects fuel into the intake port 7. These in-cylinder injection fuel injection valve 8 and port injection fuel injection valve 41 are both electromagnetic or piezoelectric injection valves that are opened when a drive pulse signal is applied. An amount of fuel that is substantially proportional to the pulse width is injected.

  An electronically controlled throttle valve 19 whose opening is controlled by a control signal from the engine controller 9 is interposed upstream of the collector portion 18a of the intake passage 18 connected to the intake port 7. A turbocharger compressor 20 is disposed on the upstream side. An air flow meter 10 that detects the intake air amount is disposed upstream of the compressor 20.

  In addition, a catalyst device 13 made of a three-way catalyst is interposed in the exhaust passage 12 connected to the exhaust port 11, and an air-fuel ratio sensor 14 for detecting the air-fuel ratio is disposed upstream thereof.

  In addition to the air flow meter 10 and the air-fuel ratio sensor 14, the engine controller 9 includes a crank angle sensor 15 for detecting the engine speed, a water temperature sensor 16 for detecting the coolant temperature, and an accelerator pedal operated by the driver. Detection signals of sensors such as an accelerator opening sensor 17 that detects the amount of depression of the vehicle are input. Based on these detection signals, the engine controller 9 optimally controls the fuel injection amount and injection timing by the fuel injection valves 8 and 41, the ignition timing by the spark plug 6, the opening of the throttle valve 19, and the like.

  On the other hand, the variable compression ratio mechanism 2 uses a known multi-link type piston crank mechanism, and includes a lower link 22 rotatably supported by a crank pin 21 a of the crankshaft 21 and one end of the lower link 22. An upper link 25 for connecting the upper pin 23 of the part and the piston pin 24a of the piston 24, a control link 27 having one end connected to the control pin 26 at the other end of the lower link 22, and the other end of the control link 27 And a control shaft 28 that supports the shaft in a swingable manner. The crankshaft 21 and the control shaft 28 are rotatably supported in a crankcase below the cylinder block 29 via a bearing structure (not shown). The control shaft 28 has an eccentric shaft portion 28a whose position changes with the rotation of the control shaft 28. Specifically, the end portion of the control link 27 is rotatably fitted to the eccentric shaft portion 28a. Match. In the variable compression ratio mechanism 2 described above, the top dead center position of the piston 24 is displaced up and down with the rotation of the control shaft 28, so that the mechanical compression ratio changes.

  As a drive mechanism for variably controlling the compression ratio of the variable compression ratio mechanism 2, an electric motor 31 having a rotation center axis parallel to the crankshaft 21 is disposed below the cylinder block 29. A reduction gear 32 is connected so as to be arranged in series in the direction. As the speed reducer 32, for example, a wave gear mechanism having a large speed reduction ratio is used, and the speed reducer output shaft 32 a is positioned coaxially with the output shaft (not shown) of the electric motor 31. Accordingly, the speed reducer output shaft 32a and the control shaft 28 are positioned in parallel with each other, and the first arm 33 and the control shaft 28 fixed to the speed reducer output shaft 32a are connected to each other so that both of them rotate in conjunction with each other. The fixed second arm 34 is connected to each other by an intermediate link 35.

  That is, when the electric motor 31 rotates, the angle of the speed reducer output shaft 32a changes in a form greatly decelerated by the speed reducer 32. The rotation of the speed reducer output shaft 32a is transmitted from the first arm 33 to the second arm 34 via the intermediate link 35, and the control shaft 28 rotates. Thereby, as mentioned above, the mechanical compression ratio of the internal combustion engine 1 changes. In the illustrated example, the first arm 33 and the second arm 34 extend in the same direction. Therefore, for example, when the speed reducer output shaft 32a rotates in the clockwise direction, the control shaft 28 also rotates in the clockwise direction. Although it is related, the link mechanism can also be configured to rotate in the opposite direction.

  The target compression ratio of the variable compression ratio mechanism 2 is set in the engine controller 9 based on engine operating conditions (for example, required load and engine speed), and the electric motor 31 is driven so as to realize this target compression ratio. Be controlled.

  Furthermore, a flow control valve 50 that provides a tumble flow component or a swirl flow component by opening and closing a part of the intake passage is provided as a flow device that controls in-cylinder flow. The operation of the flow control valve 50 is also controlled by the engine controller 9 based on engine operating conditions.

  2 and 3 show the ratio of port injection to in-cylinder injection and the compression ratio (compression ratio) under operating conditions where homogeneity is required to ensure combustion stability, as in fast idle operation immediately after cold start. ε) and the strength of the in-cylinder flow, the ease of ignition (ignitability), and the homogeneity are shown. In the following description, the in-cylinder injection by the in-cylinder injection fuel injection valve 8 is also referred to as “DGI”, and the port injection by the port injection fuel injection valve 41 is also referred to as “MPI”.

  As shown in FIG. 2A, basically, in-cylinder injection (GDI) is easier to ignite than port injection (MPI). In both cases of in-cylinder injection (GDI) and port injection (MPI), if the compression ratio is equal to or greater than a predetermined threshold value εs, the secondary voltage increases as the compression ratio increases. Will decline. Furthermore, in both the in-cylinder injection (GDI) and the port injection (MPI), in the low compression ratio region below the threshold εs, the lower the compression ratio, the more the flow component in the cylinder remains without being crushed, and Since the risk of blowout increases, the ease of ignition decreases.

  As shown in FIG. 2B, basically, port injection (MPI) has a higher degree of homogeneity than in-cylinder injection (GDI). Further, in any of the in-cylinder injection (GDI) and the port injection (MPI), the lower the compression ratio, the more in-cylinder flow remains without being crushed, and the homogeneity increases.

  With reference to FIG. 3A, as described above, in-cylinder injection (GDI) is easier to ignite than port injection (MPI). In addition, the higher the flow strength in the cylinder, the greater the risk of side fire and blowout, and the ease of ignition decreases.

  Referring to FIG. 3 (B), the port injection (MPI) is a cylinder that directly injects fuel into the combustion chamber because an air-fuel mixture in which fuel and air are mixed beforehand in the intake port is introduced into the combustion chamber. The degree of homogeneity is higher than that of internal injection (GDI). Further, the higher the strength of the in-cylinder flow, the higher the homogeneity.

  In the present embodiment, under predetermined operating conditions where the homogeneity of the air-fuel mixture is required, the share ratio, compression ratio, and cylinder are set so that each of the homogeneity and ignitability (ease of ignition) satisfies a predetermined level TG. This is a coordinated control of internal flow. For example, as shown in FIG. 4 (A), when the homogeneity is lower than a predetermined level TG among the ease of ignition and the homogeneity, and this homogeneity does not satisfy the predetermined level TG at most compression ratios. As shown in FIG. 4B, in order to improve the homogeneity, the share of port injection (MPI) is increased. Thereby, although the ease of ignition is reduced, the homogeneity is improved, and the region R1 where both the ease of ignition and the homogeneity exceed the predetermined level TG is expanded. Therefore, by setting the compression ratio as high as possible in the region R1, it is possible to increase the compression ratio and improve the combustion efficiency while ensuring the ignition ease and homogeneity of the predetermined level TG.

  On the other hand, as shown in FIG. 5A, when the ease of ignition is lower than the predetermined level TG among the ease of ignition and the homogeneity, the ease of ignition is improved as shown in FIG. 5B. In order to achieve this, the share ratio of in-cylinder injection (GDI) is increased. Thereby, although the homogeneity is lowered, the homogeneity is improved, and it is possible to secure a region R2 in which both the ease of ignition and the homogeneity exceed a predetermined level TG. Therefore, by setting the compression ratio as high as possible in the region R2, it is possible to increase the compression ratio while ensuring the ignition ease and homogeneity of the predetermined level TG.

  Such characteristic configurations and operational effects of this embodiment are listed below.

  [1] In the present embodiment, under predetermined operating conditions typified at the time of cold start, predetermined control is performed by cooperatively controlling the ratio of in-cylinder injection and port injection, the compression ratio, and in-cylinder flow. After ensuring the homogeneity and ignitability (easiness of ignition) of the air-fuel mixture at level TG, for example, the compression ratio can be set as high as possible to improve the combustion efficiency.

  [2] When improving the homogeneity, the ratio of port injection is increased in the example shown in FIG. 4 (B), but not limited to this, the reduction of the compression ratio and the enhancement of the in-cylinder flow are singly or combined. May be performed.

  [3] In the case of improving the ignitability, in the example shown in FIG. 5 (B), the share ratio of the in-cylinder injection is increased. However, the present invention is not limited to this. You may make it carry out in combination.

  [4] However, in order to increase the compression ratio as much as possible and improve the combustion efficiency, it is desirable to preferentially increase the compression ratio as in the examples of FIGS.

  [5] In actual control, as an example, the target values of the above-mentioned share ratio, compression ratio, and in-cylinder flow are set to the engine load and water temperature so that a predetermined level of homogeneity and ignitability of the air-fuel mixture can be obtained. Is set as a map having parameters as parameters, and the target value is set in a feed-forward manner with reference to this map.

  [6] Alternatively, the homogeneity and ignitability of the air-fuel mixture are detected or estimated using a sensor or the like, and based on the detected or estimated homogeneity and ignitability, the above-described share ratio, compression ratio, and in-cylinder At least one of the flows may be feedback controlled.

  [7] Furthermore, the above feedforward control and feedback control may be combined. That is, the target values of the above-mentioned share ratio, compression ratio, and in-cylinder flow are set using a map or the like previously adapted to obtain a predetermined level of homogeneity and ignitability of the mixture, and the mixture Detects or estimates the homogeneity and ignitability of the engine, and based on these detected or estimated homogeneity and ignitability, feedback control to at least one of the above-mentioned share ratio, compression ratio, and in-cylinder flow toward the target value You may make it do.

  [8] When only a predetermined level of ignitability is not obtained among homogeneity and ignitability, at least one of the advance of the ignition timing or the reduction of the EGR rate may be performed. .

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Variable compression ratio mechanism 6 ... Spark plug 8 ... Fuel injection valve for cylinder injection 9 ... Engine controller 14 ... Air-fuel ratio sensor 20 ... Compressor 41 ... Fuel injection valve for port injection 50 ... Flow control valve (flow) device)

Claims (9)

The mechanical compression ratio is increased by changing the relative positional relationship between the port injection fuel injection valve that injects fuel into the intake port, the in-cylinder injection fuel injection valve that injects fuel into the combustion chamber, and the piston and cylinder. In a control device for an internal combustion engine, comprising: a variable compression ratio mechanism that is variable; and a fluid device that varies the in-cylinder flow.
Coordinated control of the ratio of in-cylinder injection and port injection, compression ratio, and in-cylinder flow so that a predetermined level of air-fuel mixture homogeneity and ignitability can be obtained under predetermined operating conditions A control device for an internal combustion engine.   2. The control device for an internal combustion engine according to claim 1, wherein when the homogeneity is improved, at least one of reduction of a compression ratio, increase of a share ratio of port injection, and enhancement of in-cylinder flow is performed.   3. The control device for an internal combustion engine according to claim 1, wherein when ignitability is improved, at least one of a reduction in the compression ratio, an increase in the share ratio of in-cylinder injection, and a reduction in in-cylinder flow are performed.   The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the compression ratio is preferentially increased within a range in which the homogeneity and ignitability of the air-fuel mixture at a predetermined level are obtained.   The target values of the share ratio, compression ratio, and in-cylinder flow are set according to engine operating conditions so that a predetermined level of homogeneity and ignitability of the air-fuel mixture can be obtained. The control apparatus of the internal combustion engine in any one of 1-4.   Detecting or estimating the homogeneity and ignitability of the air-fuel mixture, and feedback-controlling at least one of the above-mentioned share ratio, compression ratio and in-cylinder flow based on the detected or estimated homogeneity and ignitability. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine. In order to obtain a predetermined level of air-fuel mixture homogeneity and ignitability, the target values of the above-mentioned share ratio, compression ratio, and in-cylinder flow are set according to the engine operating state,
Detect or estimate the homogeneity and ignitability of the air-fuel mixture, and based on the detected or estimated homogeneity and ignitability, aim at least one of the above-mentioned share ratio, compression ratio and in-cylinder flow toward the target value. 5. The control apparatus for an internal combustion engine according to claim 1, wherein feedback control is performed.   When only a predetermined level of ignitability is not obtained among homogeneity and ignitability, at least one of advance of the ignition timing or reduction of the EGR rate is performed. The internal combustion engine control device described. The mechanical compression ratio is increased by changing the relative positional relationship between the port injection fuel injection valve that injects fuel into the intake port, the in-cylinder injection fuel injection valve that injects fuel into the combustion chamber, and the piston and cylinder. In a control method for an internal combustion engine, comprising: a variable compression ratio mechanism that is variable; and a cylinder flow device that varies cylinder flow.
Coordinated control of the ratio of in-cylinder injection and port injection, compression ratio, and in-cylinder flow so that a predetermined level of air-fuel mixture homogeneity and ignitability can be obtained under predetermined operating conditions A control method of an internal combustion engine characterized by the above.

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